Add anonymous listening support and redesign web-player UI

Backend:
- Expose GET /config/playback so the frontend can detect whether
  anonymous listening is enabled without requiring auth
- Wire anonymous access through track streaming and YouTube resolve flows

Frontend:
- Allow browsing/listening without a session when the backend enables it
- Redesign Inicio, Sidebar and top bar with a new dark theme, typography,
  and layout (top bar with live quick-search, sticky/blurred on scroll)
- Populate Top música, Popular and Recomendados with real Musify +
  YouTube Music data instead of placeholders
- Various shape, spacing, color and animation refinements across the
  redesigned components

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

.claude/launch.json

@@ -4,21 +4,14 @@
 		{
 			"name": "musify-web",
 			"runtimeExecutable": "npm",
-			"runtimeArgs": ["--prefix", "web-player", "run", "dev"],
-			"port": 3000,
-			"autoPort": true
+			"runtimeArgs": ["--prefix", "web-player", "run", "dev", "--", "--port", "3000"],
+			"port": 3000
 		},
 		{
 			"name": "musify-api",
 			"runtimeExecutable": "dotnet",
 			"runtimeArgs": ["run", "--project", "backend/Hosts/Musify.Api"],
 			"port": 5111
-		},
-		{
-			"name": "musify-streaming-gateway",
-			"runtimeExecutable": "dotnet",
-			"runtimeArgs": ["run", "--project", "backend/Hosts/Musify.StreamingGateway"],
-			"port": 8081
 		}
 	]
 }

.gitea/workflows/ci-cd.yml

@@ -1,127 +0,0 @@
-name: CI/CD
-
-on:
-  push:
-    branches: ['**']
-  pull_request:
-    branches: ['**']
-
-concurrency:
-  group: production-deploy
-  cancel-in-progress: false
-
-jobs:
-  backend-tests:
-    name: BackEnd
-    runs-on: ubuntu-latest
-    timeout-minutes: 20
-    defaults:
-      run:
-        working-directory: backend
-    steps:
-      - uses: actions/checkout@v4
-
-      - uses: actions/setup-dotnet@v4
-        with:
-          dotnet-version: '10.0.x'
-
-      - name: Restore
-        run: dotnet restore Musify.slnx
-
-      - name: Build
-        run: dotnet build Musify.slnx --no-restore -c Release
-
-      - name: Test
-        run: dotnet test Musify.slnx --no-build -c Release
-
-  web-player-checks:
-    name: WebPlayer
-    runs-on: ubuntu-latest
-    timeout-minutes: 15
-    defaults:
-      run:
-        working-directory: web-player
-    steps:
-      - uses: actions/checkout@v4
-
-      - uses: actions/setup-node@v4
-        with:
-          node-version: '22'
-          cache: npm
-          cache-dependency-path: web-player/package-lock.json
-
-      - run: npm ci
-
-      - name: Type-check
-        run: npm run check
-
-      - name: Lint
-        run: npm run lint
-
-  # Runs on the production host itself, through the existing self-hosted
-  # Gitea Actions runner (act_runner), which also carries a "production"
-  # label registered in native (non-docker) mode so its steps see the host's
-  # real Docker daemon directly (Docker socket + a bind-mounted deploy
-  # directory — see deploy/README.md for how that runner is set up).
-  #
-  # DEPLOY_PATH is the persistent clone already on that host (the one whose
-  # deploy/.env.prod is filled in and matches SharedServices/.env.prod) —
-  # deploy reuses it instead of a fresh checkout, since .env.prod is
-  # untracked and only lives there.
-  deploy:
-    name: Deploy
-    needs: [backend-tests, web-player-checks]
-    if: github.ref == 'refs/heads/master' && github.event_name == 'push'
-    runs-on: [production]
-    timeout-minutes: 20
-    env:
-      DEPLOY_PATH: /home/ubuntu/deploys/musify
-      COMPOSE: docker compose --env-file deploy/.env.prod -f deploy/compose.yml -f deploy/compose.prod.yml
-    steps:
-      - name: Pull latest master
-        run: |
-          set -euo pipefail
-          git config --global --add safe.directory "$DEPLOY_PATH"
-          cd "$DEPLOY_PATH"
-          git fetch origin master
-          git reset --hard origin/master
-
-      - name: Generate stream-ticket keys
-        run: |
-          set -euo pipefail
-          cd "$DEPLOY_PATH"
-          $COMPOSE run --rm --no-deps keys-init
-
-      # The migrations are baked into the migrator image, so it is rebuilt on
-      # every deploy (plain `up` would reuse the stale image and re-apply the
-      # old migrations). `run --rm` starts wait-for-postgres, blocks until the
-      # migration finishes and propagates its exit code, so a failed migration
-      # aborts the deploy before the new API is started against an old schema.
-      - name: Migrate database
-        run: |
-          set -euo pipefail
-          cd "$DEPLOY_PATH"
-          $COMPOSE build migrate
-          $COMPOSE run --rm migrate
-
-      # Both jobs verify themselves through the public auth./s3. URLs, served
-      # by the shared edge nginx (Infrastructure's edge/), and are idempotent.
-      - name: Create OIDC app and S3 bucket
-        run: |
-          set -euo pipefail
-          cd "$DEPLOY_PATH"
-          $COMPOSE up -d seaweedfs-init zitadel-init
-          for job in musify-seaweedfs-init musify-zitadel-init; do
-            code=$(docker wait "$job")
-            if [ "$code" != "0" ]; then
-              docker logs "$job"
-              echo "$job exited with $code"
-              exit 1
-            fi
-          done
-
-      - name: Build and start apps
-        run: |
-          set -euo pipefail
-          cd "$DEPLOY_PATH"
-          $COMPOSE --profile apps up -d --build api worker gateway web-player

.gitignore

@@ -7,9 +7,6 @@ obj/
 *.userosscache
 .vs/
 artifacts/
-TestResults/
-*.trx
-*.coverage
 
 # Rider / VS
 .idea/
@@ -28,4 +25,5 @@ Thumbs.db
 # Deploy secrets and runtime state
 deploy/keys/
 deploy/secrets/
+deploy/nginx/certs/
 deploy/zitadel/.output/

README.md

@@ -1,55 +1,57 @@
 # Musify
 
-A music streaming app. Upload your own tracks, organize them into playlists
-and albums, and stream them back with a web player built around your
-listening habits: auto-generated mixes, a home feed, search, likes, and an
-Explore page for finding something new.
-
-## What it does
-
-- **Upload and organize your own music**: tracks, albums, cover art, artist credits.
-- **Playlists**, likes, and a "recently played" history.
-- **Mixes**, playlists generated automatically from what you actually listen to.
-- **Explore**, genre browsing and search across tracks, albums, playlists and people.
-- **Real streaming**, not just file downloads: seek, queue, shuffle, repeat.
-- **Accounts via OIDC login**, with an optional anonymous listening mode.
-- Light and dark themes, and a layout that works on both desktop and mobile.
-
-## How it's built
-
-**Backend**: .NET 10, split into a REST API, a background worker, and a
-dedicated streaming gateway.
-- Clean architecture (Domain / Application / Infrastructure) with CQRS (Mediator) and `ErrorOr` results.
-- PostgreSQL via EF Core for metadata. RabbitMQ and MassTransit handle async processing (audio transcoding, thumbnails) with saga-based rollback.
-- SeaweedFS (S3-compatible) for file storage. Uploads and downloads go straight between the client and storage, never through the API.
-- ffmpeg for audio transcoding, ImageSharp for thumbnails.
-- A YARP reverse proxy that streams the audio and checks a signed, short-lived ticket on every request.
-- Zitadel for login (OIDC/OAuth2).
-
-**Web client**: SvelteKit 2 on Svelte 5 (runes), TypeScript, Tailwind 4.
-The session lives on the server, so the backend access token never reaches the browser.
-
-**Infrastructure**: Musify's own apps run from Docker Compose (dev and
-production overlays). Postgres, RabbitMQ, SeaweedFS, Zitadel and Jaeger are
-shared infrastructure that lives in a separate `Infrastructure` git
-repository, used by Musify and by other projects that need the same OIDC
-provider and object storage.
-
-## Project layout
+Music streaming platform: upload your own tracks (or import them from YouTube),
+process them asynchronously (audio transcoded to `.m4a`, thumbnails generated)
+and stream them without the bytes ever going through the API.
 
 ```
-backend/      .NET solution: Api, Worker, StreamingGateway, and the shared Domain/Application/Infrastructure
-web-player/   the SvelteKit web client
-deploy/       Docker Compose stacks for dev and production
-docs/         architecture notes, one file per area
+backend/      .NET 10 — Domain / Application / Infrastructure / Api / Worker / StreamingGateway / Tests
+web-player/   SvelteKit 2 + Svelte 5 + Tailwind 4 web client
+deploy/       Docker Compose stacks — self-contained, no wrapper scripts
+docs/         What each piece does and why (in Spanish)
 ```
 
-Postgres, Zitadel, SeaweedFS, RabbitMQ and Jaeger are not part of this
-layout. They live in the separate `Infrastructure` repository instead.
+```sh
+dotnet test backend/Musify.slnx   # backend/Tests/ — Docker running (Testcontainers: Postgres, SeaweedFS)
+```
 
-## Digging deeper
+## Run it
 
-[docs/](docs/README.md) covers how each piece works and why: architecture,
-authentication, storage, streaming, media processing, and the local dev
-setup. [deploy/README.md](deploy/README.md) has the full instructions for
-running the stack, in development or on a production server.
+Development (Docker Desktop):
+
+```sh
+docker compose -f deploy/compose.yml -f deploy/compose.dev.yml up -d
+```
+
+Infrastructure plus stream-ticket keys, database migrations and Zitadel OIDC
+provisioning — all as one-shot jobs baked into the compose file. Apps run from
+the IDE by default; add `--profile apps up -d --build` as a second command to
+run them in Docker instead.
+
+Production, on a server with a domain:
+
+```sh
+cp deploy/.env.prod.example deploy/.env.prod   # fill in the domain and secrets
+docker compose --env-file deploy/.env.prod -f deploy/compose.yml -f deploy/compose.prod.yml up -d
+docker compose --env-file deploy/.env.prod -f deploy/compose.yml -f deploy/compose.prod.yml --profile apps up -d --build
+```
+
+Idempotent — run the same commands again to deploy an update. See
+[deploy/README.md](deploy/README.md) for the details, the port map and the
+production prerequisites.
+
+## Components
+
+| Service | Port (dev) | Role |
+|---|---|---|
+| `Musify.Api` | 5111 | REST API, issues presigned upload URLs and stream tickets |
+| `Musify.StreamingGateway` | 8081 | YARP proxy that validates the stream ticket and serves the audio |
+| `Musify.Worker` | — | MassTransit consumers: transcoding, thumbnails, YouTube downloads |
+| `web-player` | 5173 / 3000 | Web client (SvelteKit, server-side OIDC session) |
+| Zitadel | 8080 | Identity (OIDC/OAuth2) |
+| PostgreSQL / RabbitMQ / SeaweedFS / Jaeger | 59000 / 5672 / 8333 / 16686 | Metadata, messaging, object storage, traces |
+
+More in [docs/](docs/README.md): [architecture](docs/architecture.md),
+[authentication](docs/authentication.md), [storage](docs/storage.md),
+[streaming](docs/streaming.md), [media processing](docs/media-processing.md),
+[development](docs/development.md).

backend/.editorconfig

@@ -1,79 +0,0 @@
-root = true
-
-[*]
-charset = utf-8
-insert_final_newline = true
-trim_trailing_whitespace = true
-indent_style = space
-
-[*.{csproj,props,targets,slnx,xml}]
-indent_size = 2
-
-[*.json]
-indent_size = 4
-
-[**/Migrations/**.cs]
-generated_code = true
-
-[*.cs]
-indent_size = 4
-
-csharp_style_namespace_declarations = block_scoped:warning
-csharp_using_directive_placement = outside_namespace:warning
-dotnet_sort_system_directives_first = true
-dotnet_separate_import_directive_groups = false
-dotnet_diagnostic.IDE0005.severity = warning
-
-dotnet_style_require_accessibility_modifiers = always:warning
-csharp_style_var_for_built_in_types = true:suggestion
-csharp_style_var_when_type_is_apparent = true:suggestion
-csharp_style_var_elsewhere = true:suggestion
-csharp_prefer_braces = when_multiline:warning
-csharp_style_prefer_primary_constructors = true:suggestion
-csharp_style_expression_bodied_methods = when_on_single_line:suggestion
-dotnet_style_prefer_collection_expression = when_types_loosely_match:suggestion
-
-# Naming. Roslyn applies the first matching rule in file order, so the specific rules come first.
-# Private fields are _camelCase whatever their modifiers (static, readonly, const).
-dotnet_naming_rule.private_fields.symbols = private_fields
-dotnet_naming_rule.private_fields.style = underscore_camel_case
-dotnet_naming_rule.private_fields.severity = warning
-dotnet_naming_symbols.private_fields.applicable_kinds = field
-dotnet_naming_symbols.private_fields.applicable_accessibilities = private
-dotnet_naming_style.underscore_camel_case.capitalization = camel_case
-dotnet_naming_style.underscore_camel_case.required_prefix = _
-
-# Non-private fields (constants, static readonly, etc.) are PascalCase.
-dotnet_naming_rule.other_fields.symbols = other_fields
-dotnet_naming_rule.other_fields.style = pascal_case
-dotnet_naming_rule.other_fields.severity = warning
-dotnet_naming_symbols.other_fields.applicable_kinds = field
-dotnet_naming_symbols.other_fields.applicable_accessibilities = public, internal, protected, protected_internal, private_protected
-dotnet_naming_style.pascal_case.capitalization = pascal_case
-
-dotnet_naming_rule.interfaces.symbols = interfaces
-dotnet_naming_rule.interfaces.style = interface_style
-dotnet_naming_rule.interfaces.severity = warning
-dotnet_naming_symbols.interfaces.applicable_kinds = interface
-dotnet_naming_style.interface_style.capitalization = pascal_case
-dotnet_naming_style.interface_style.required_prefix = I
-
-dotnet_naming_rule.types_and_members.symbols = types_and_members
-dotnet_naming_rule.types_and_members.style = pascal_case
-dotnet_naming_rule.types_and_members.severity = warning
-dotnet_naming_symbols.types_and_members.applicable_kinds = class, struct, enum, delegate, property, method, event
-dotnet_naming_symbols.types_and_members.applicable_accessibilities = *
-
-# CA1848/CA1873 would turn every log call into a [LoggerMessage] source-generated method; CA1716 flags the
-# EF-style IDatabase.Set<T>() and the Musify.Application.Shared namespace, whose names are deliberate.
-dotnet_diagnostic.CA1848.severity = suggestion
-dotnet_diagnostic.CA1873.severity = suggestion
-dotnet_diagnostic.CA1716.severity = suggestion
-# The routing slip builders are stateless services resolved from DI; they stay instance members.
-dotnet_diagnostic.CA1822.severity = suggestion
-
-# Test names follow Method_Scenario_Expected.
-[Tests/**.cs]
-dotnet_diagnostic.CA1707.severity = none
-# xUnit collection fixtures are conventionally named ...Collection.
-dotnet_diagnostic.CA1711.severity = none

backend/CLAUDE.md

@@ -1,58 +0,0 @@
-# Musify: backend
-
-.NET 10 solution (`Musify.slnx`): `Core/` (Domain, Application, Infrastructure), `Hosts/` (Api, Worker, StreamingGateway) and `Tests/`. Architecture and flows are in `../docs/`.
-
-## Commands
-
-Run from `backend/`.
-
-```sh
-dotnet build Musify.slnx            # warnings are errors, including unused usings (IDE0005)
-dotnet test Musify.slnx             # Infrastructure and Api tests need Docker (Testcontainers)
-dotnet format Musify.slnx --verify-no-changes
-```
-
-- Read the totals of `dotnet test` (`total:`, `succeeded:`) before trusting it; don't chain it with `&&` into a commit.
-- EF migrations: `dotnet ef migrations add <Name> --project Core/Musify.Infrastructure --startup-project Core/Musify.Infrastructure` (set `Database__ConnectionString` to any value). A model change needs a migration; the entity model lives in `ModelConfiguration.Apply`, which the in-memory test database reuses.
-- An HTTP contract change (routes, DTOs, responses) needs the web-player schema regenerated (`web-player/src/lib/api/schema.d.ts`, from `/openapi/v1.json`) and `npm run check` clean.
-- A MassTransit message change (events, routing slip arguments, process kinds) means the queues must be drained before deploying; note it in the commit.
-
-## Style
-
-- Block-scoped namespaces (`namespace X { }`; file-scoped `namespace X;` is not allowed), usings outside the namespace and sorted (`.editorconfig` enforces it).
-- Private fields are `_camelCase` whatever their modifiers (including `static readonly` and `const`); non-private constants and static fields, types, methods and properties are PascalCase; interfaces start with `I`; explicit accessibility. Enforced by `.editorconfig` (IDE1006).
-- `ArgumentNullException.ThrowIfNull(x)` without `nameof`.
-- Use `PlayList` (not `Playlist`) in code; configuration POCOs end in `Configuration`; injected services are named after their type (`storageService`).
-- User-facing strings are in English (the web-player owns translation).
-- Trim stored names; normalized columns go through `TextNormalizer.Normalize`.
-- Format ids and numbers with `CultureInfo.InvariantCulture`; put `CancellationToken` last.
-
-## Application layer
-
-- One file per use case, `<Feature>/<UseCase>.cs`, holding the record and its handler; responses go in `Responses/`.
-- Errors come from `AppErrors` (`NotFound`, `Forbidden` = 403 for "not the owner", `Conflict`). `Error.Unauthorized` (401) only means "not signed in". The success value is `Result.Success`; the API maps it to 204.
-- Handlers that cannot fail return plain types. Lists are paginated through `PageRequest` / `ToPaginatedAsync`, ordered with an `Id` tiebreak, and public reads return only `LifeCycleStatus.Active` rows.
-- Owned-entity operations go through `FindOwnedAsync` (non-active entities are not found).
-- No try/catch around `SaveChangesAsync` or `PublishAsync` in handlers: the outbox makes publish + save atomic. Infrastructure either handles an error or lets it propagate; never log and rethrow.
-- List query records keep `int PageNumber, int PageSize`; the API binds them through `PageQuery` and validates them with `PageQueryValidator`.
-
-## API layer
-
-- Routes: `{id:guid}` for the resource, `{trackId:guid}` for sub-resources, `{id:long}` / `{userId:long}` for user ids.
-- Every endpoint returns `IResult` (`Results.Ok` when the handler cannot fail, `ToHttpResult()` otherwise).
-- Validation limits live in `Validators/Limits.cs`; the database column length wins when a limit disagrees with the web-player. Upload allow-lists are in `Validators/Uploads.cs`.
-- `.WithSummary(...)` is sentence case without a trailing period.
-
-## Infrastructure and hosts
-
-- MassTransit routing slips are built from `RoutingSlips.Create` / `AddStep` / `TrackFaults`; activities for the three owner types share generic bases (`MarkLifeCycleActivity<T>`, `DeleteEntityActivity<T>`, `UpdatePicturesActivity<T>`).
-- Recurring work is Hangfire (`RecurringJobsRegistrar`); intervals are in seconds and rounded up to whole minutes.
-- The Worker calls `AddApplication` and validates its service container on build, so any handler dependency must be registered there. Shared config sections in its `appsettings.json` mirror the API's.
-- The StreamingGateway references neither Application nor Infrastructure and keeps its own options.
-
-## Tests
-
-- xUnit v3; pass `TestContext.Current.CancellationToken` to methods that take a token (analyzer xUnit1051).
-- Test names are `Method_Scenario_Expected`.
-- Application tests use the in-memory SQLite `TestDatabase`; Infrastructure and Api tests use Testcontainers (Postgres, SeaweedFS). MassTransit sagas and consumers are tested on the MassTransit test harness.
-- `Infrastructure` exposes its internals to `Musify.Infrastructure.Tests`.

backend/Core/Musify.Application/Albums/AddTrackToAlbum.cs

@@ -0,0 +1,85 @@
+using ErrorOr;
+using Mediator;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.Logging;
+using Musify.Application.Contracts;
+using Musify.Domain.Entities;
+
+namespace Musify.Application.Albums
+{
+    public record AddTrackToAlbumCommand(long UserId, Guid AlbumId, Guid TrackId)
+        : ICommand<ErrorOr<Success>>;
+
+    public class AddTrackToAlbumCommandHandler(
+        IDatabase database,
+        ILogger<AddTrackToAlbumCommandHandler> logger)
+        : ICommandHandler<AddTrackToAlbumCommand, ErrorOr<Success>>
+    {
+        public async ValueTask<ErrorOr<Success>> Handle(AddTrackToAlbumCommand request, CancellationToken cancellationToken)
+        {
+            var album = await database.UserAlbums
+                .AsNoTracking()
+                .SingleOrDefaultAsync(a => a.Id == request.AlbumId, cancellationToken);
+            if (album is null)
+            {
+                logger.LogInformation("Album {AlbumId} not found", request.AlbumId);
+                return Error.NotFound();
+            }
+
+            if (album.OwnerUserId != request.UserId)
+            {
+                logger.LogWarning("User {UserId} is not the owner of album {AlbumId}", request.UserId, request.AlbumId);
+                return Error.Unauthorized();
+            }
+
+            var trackExists = await database.Tracks
+                .AsNoTracking()
+                .AnyAsync(t => t.Id == request.TrackId, cancellationToken);
+            if (!trackExists)
+            {
+                logger.LogInformation("Track {TrackId} not found", request.TrackId);
+                return Error.NotFound(description: $"Track {request.TrackId} not found");
+            }
+
+            var localTrack = await database.LocalTracks
+                .AsNoTracking()
+                .SingleOrDefaultAsync(t => t.Id == request.TrackId, cancellationToken);
+            if (localTrack is not null && localTrack.OwnerUserId != request.UserId)
+            {
+                logger.LogWarning("User {UserId} does not own track {TrackId}", request.UserId, request.TrackId);
+                return Error.Unauthorized();
+            }
+
+            var alreadyAdded = await database.AlbumHasTracks
+                .AsNoTracking()
+                .AnyAsync(albumTrack => albumTrack.AlbumId == request.AlbumId && albumTrack.TrackId == request.TrackId, cancellationToken);
+            if (alreadyAdded)
+            {
+                logger.LogInformation("Track {TrackId} already in album {AlbumId}", request.TrackId, request.AlbumId);
+                return Error.Conflict(description: "Track is already in the album.");
+            }
+
+            var albumTracksQuery = database.AlbumHasTracks
+                .Where(albumTrack => albumTrack.AlbumId == request.AlbumId);
+
+            var hasTracks = await albumTracksQuery.AnyAsync(cancellationToken);
+            var nextTrackNumber = hasTracks
+                ? await albumTracksQuery.MaxAsync(albumTrack => albumTrack.TrackNumber, cancellationToken) + 1
+                : 1;
+
+            await database.AlbumHasTracks.AddAsync(new AlbumHasTrack
+            {
+                AlbumId = request.AlbumId,
+                TrackId = request.TrackId,
+                TrackNumber = nextTrackNumber
+            }, cancellationToken);
+
+            await database.SaveChangesAsync(cancellationToken);
+
+            logger.LogInformation("Added track {TrackId} to album {AlbumId} as number {TrackNumber}",
+                request.TrackId, request.AlbumId, nextTrackNumber);
+
+            return new Success();
+        }
+    }
+}

backend/Core/Musify.Application/Albums/AddTracksToAlbum.cs

@@ -1,78 +0,0 @@
-using ErrorOr;
-using Mediator;
-using Microsoft.EntityFrameworkCore;
-using Microsoft.Extensions.Logging;
-using Musify.Application.Contracts;
-using Musify.Application.Shared;
-using Musify.Domain.Entities;
-using Musify.Domain.ValueObjects;
-
-namespace Musify.Application.Albums
-{
-    /// <summary>Appends your own tracks to an album in the given order, skipping the ones it already has.</summary>
-    public record AddTracksToAlbumCommand(long UserId, Guid AlbumId, IReadOnlyList<Guid> TrackIds)
-        : ICommand<ErrorOr<Success>>;
-
-    public class AddTracksToAlbumCommandHandler(
-        IDatabase database,
-        ILogger<AddTracksToAlbumCommandHandler> logger)
-        : ICommandHandler<AddTracksToAlbumCommand, ErrorOr<Success>>
-    {
-        public async ValueTask<ErrorOr<Success>> Handle(AddTracksToAlbumCommand request, CancellationToken cancellationToken)
-        {
-            var album = await database.Albums.FindOwnedAsync(request.AlbumId, request.UserId, cancellationToken);
-            if (album.IsError)
-                return album.Errors;
-
-            var requestedIds = request.TrackIds.Distinct().ToList();
-
-            var tracks = await database.Tracks
-                .AsNoTracking()
-                .Where(track => requestedIds.Contains(track.Id) && track.LifeCycleStatus == LifeCycleStatus.Active)
-                .Select(track => new { track.Id, track.OwnerUserId })
-                .ToListAsync(cancellationToken);
-
-            var missing = requestedIds.FirstOrDefault(id => tracks.All(track => track.Id != id));
-            if (missing != Guid.Empty)
-                return AppErrors.NotFound("Track", missing);
-
-            var foreign = tracks.FirstOrDefault(track => track.OwnerUserId != request.UserId);
-            if (foreign != null)
-                return AppErrors.Forbidden("Track", foreign.Id);
-
-            var alreadyInAlbum = await database.AlbumHasTracks
-                .AsNoTracking()
-                .Where(link => link.AlbumId == request.AlbumId && requestedIds.Contains(link.TrackId))
-                .Select(link => link.TrackId)
-                .ToListAsync(cancellationToken);
-
-            var toAdd = requestedIds.Where(id => !alreadyInAlbum.Contains(id)).ToList();
-            if (toAdd.Count == 0)
-                return Result.Success;
-
-            // Album track numbers are user-visible, so they start at 1.
-            var nextTrackNumber = (await database.AlbumHasTracks
-                .Where(link => link.AlbumId == request.AlbumId)
-                .MaxAsync(link => (int?)link.TrackNumber, cancellationToken) ?? 0) + 1;
-
-            foreach (var trackId in toAdd)
-            {
-                await database.AlbumHasTracks.AddAsync(new AlbumHasTrack
-                {
-                    AlbumId = request.AlbumId,
-                    TrackId = trackId,
-                    TrackNumber = nextTrackNumber++
-                }, cancellationToken);
-            }
-
-            var saved = await database.TrySaveChangesAsync(
-                AppErrors.Conflict("Album.ConcurrentChange", "The album changed while adding tracks. Try again."), cancellationToken);
-            if (saved.IsError)
-                return saved;
-
-            logger.LogInformation("Added {Count} tracks to album {AlbumId}", toAdd.Count, request.AlbumId);
-
-            return Result.Success;
-        }
-    }
-}

backend/Core/Musify.Application/Albums/CreateAlbum.cs

@@ -2,15 +2,14 @@ using ErrorOr;
 using Mediator;
 using Microsoft.EntityFrameworkCore;
 using Microsoft.Extensions.Logging;
-using Musify.Application.Albums.Responses;
 using Musify.Application.Configuration;
-using Musify.Application.Contracts;
-using Musify.Application.Events;
-using Musify.Application.Pictures;
-using Musify.Application.Services;
 using Musify.Application.Shared;
+using Musify.Application.Events;
+using Musify.Application.Albums.Responses;
+using Musify.Application.Services;
 using Musify.Domain.Entities;
 using Musify.Domain.ValueObjects;
+using Musify.Application.Contracts;
 
 namespace Musify.Application.Albums
 {
@@ -27,7 +26,9 @@ namespace Musify.Application.Albums
         IDatabase database,
         UploadIntentValidator uploadIntentValidator,
         ILogger<CreateAlbumCommandHandler> logger,
-        AlbumConfiguration albumConfiguration)
+        ApplicationStorageConfiguration storageConfiguration,
+        AlbumConfiguration albumConfiguration,
+        UploadIntentConfiguration uploadIntentConfiguration)
         : ICommandHandler<CreateAlbumCommand, ErrorOr<AlbumApplicationResponse>>
     {
         public async ValueTask<ErrorOr<AlbumApplicationResponse>> Handle(CreateAlbumCommand request, CancellationToken cancellationToken)
@@ -36,38 +37,92 @@ namespace Musify.Application.Albums
                 .AsNoTracking()
                 .AnyAsync(user => user.Id == request.UserId, cancellationToken);
             if (!userExists)
-                return AppErrors.NotFound("User", request.UserId);
+            {
+                logger.LogWarning("User {UserId} not found", request.UserId);
+                return Error.NotFound(description: $"User {request.UserId} not found");
+            }
 
-            var prepared = await PictureSourceChange.PrepareAsync(
-                uploadIntentValidator, request.PictureIntentId, request.UserId, UploadIntentPurpose.AlbumPicture, albumConfiguration, cancellationToken);
-            if (prepared.IsError)
-                return prepared.Errors;
+            var pictureIntent = await uploadIntentValidator.ValidateAndLoadAsync(
+                uploadIntentConfiguration, request.PictureIntentId, request.UserId, cancellationToken);
+            if (pictureIntent.IsError)
+                return pictureIntent.Errors;
 
-            var picture = prepared.Value;
+            var intent = pictureIntent.Value;
             var title = request.Title.Trim();
 
-            var album = new Album
+            var album = new UserAlbum
             {
                 OwnerUserId = request.UserId,
                 Title = title,
-                NormalizedTitle = TextNormalizer.Normalize(title),
+                NormalizedTitle = title.ToUpperInvariant(),
                 Description = request.Description,
                 ReleaseYear = request.ReleaseYear,
-                Pictures = picture.Pictures
+                Pictures = new AlbumPictures
+                {
+                    OriginalName = intent.ObjectName,
+                    SmallName = intent.ObjectName,
+                    MediumName = intent.ObjectName,
+                    LargeName = intent.ObjectName
+                }
             };
 
-            await database.Albums.AddAsync(album, cancellationToken);
+            await database.UserAlbums.AddAsync(album, cancellationToken);
 
-            await eventBus.PublishAsync(
-                new CreateAlbumResourcesEvent(
-                    album.Id, picture.Intent.Id, picture.Intent.Bucket, picture.Intent.Key, picture.FinalKey, picture.Sizes),
-                cancellationToken);
+            var finalPictureKey = albumConfiguration.Routes.BuildOriginalPicturePath(request.UserId, intent.ObjectName);
+            var publishResult = await PublishCreateAlbumEventAsync(album.Id, intent, finalPictureKey, cancellationToken);
+            if (publishResult.IsError)
+                return publishResult.Errors;
 
+            try
+            {
                 await database.SaveChangesAsync(cancellationToken);
+            }
+            catch (Exception exception)
+            {
+                logger.LogError(exception, "Failed to save album for user {UserId}", request.UserId);
+                return Error.Failure(description: $"Failed to create album for user {request.UserId}");
+            }
 
             logger.LogInformation("Created album {AlbumId} for user {UserId}", album.Id, request.UserId);
 
             return AlbumApplicationResponse.FromEntity(album, trackCount: 0);
         }
+
+        private async Task<ErrorOr<Success>> PublishCreateAlbumEventAsync(
+            Guid albumId,
+            UploadIntent pictureIntent,
+            string finalPictureKey,
+            CancellationToken cancellationToken)
+        {
+            try
+            {
+                await eventBus.PublishAsync(
+                    new CreateAlbumResourcesEvent(
+                        albumId,
+                        pictureIntent.Id,
+                        storageConfiguration.Bucket,
+                        pictureIntent.Key,
+                        finalPictureKey,
+                        new ImageSize(
+                            albumConfiguration.Routes.SmallPicturesPath,
+                            albumConfiguration.PicturesSizes.SmallPictureWidth,
+                            albumConfiguration.PicturesSizes.SmallPictureHeight),
+                        new ImageSize(
+                            albumConfiguration.Routes.MediumPicturesPath,
+                            albumConfiguration.PicturesSizes.MediumPictureWidth,
+                            albumConfiguration.PicturesSizes.MediumPictureHeight),
+                        new ImageSize(
+                            albumConfiguration.Routes.LargePicturesPath,
+                            albumConfiguration.PicturesSizes.LargePictureWidth,
+                            albumConfiguration.PicturesSizes.LargePictureHeight)),
+                    cancellationToken);
+                return new Success();
+            }
+            catch (Exception exception)
+            {
+                logger.LogError(exception, "Failed to publish create album event for album {AlbumId}", albumId);
+                return Error.Failure(description: $"Failed to publish create album event for album {albumId}");
+            }
+        }
     }
 }

backend/Core/Musify.Application/Albums/DeleteAlbum.cs

@@ -1,10 +1,8 @@
 using ErrorOr;
 using Mediator;
+using Microsoft.EntityFrameworkCore;
 using Microsoft.Extensions.Logging;
 using Musify.Application.Contracts;
-using Musify.Application.Events;
-using Musify.Application.Shared;
-using Musify.Domain.ValueObjects;
 
 namespace Musify.Application.Albums
 {
@@ -13,25 +11,40 @@ namespace Musify.Application.Albums
 
     public class DeleteAlbumCommandHandler(
         IDatabase database,
-        IEventBus eventBus,
         ILogger<DeleteAlbumCommandHandler> logger)
         : ICommandHandler<DeleteAlbumCommand, ErrorOr<Success>>
     {
         public async ValueTask<ErrorOr<Success>> Handle(DeleteAlbumCommand request, CancellationToken cancellationToken)
         {
-            var found = await database.Albums.FindOwnedAsync(request.AlbumId, request.UserId, cancellationToken);
-            if (found.IsError)
-                return found.Errors;
+            var album = await database.UserAlbums
+                .SingleOrDefaultAsync(a => a.Id == request.AlbumId, cancellationToken);
+            if (album is null)
+            {
+                logger.LogDebug("Album {AlbumId} not found", request.AlbumId);
+                return Error.NotFound();
+            }
 
-            var album = found.Value;
-            album.LifeCycleStatus = LifeCycleStatus.Removing;
+            if (album.OwnerUserId != request.UserId)
+            {
+                logger.LogWarning("Album {AlbumId} does not belong to user {UserId}", request.AlbumId, request.UserId);
+                return Error.Unauthorized();
+            }
 
-            await eventBus.PublishAsync(new DeleteAlbumEvent(album.Id, request.UserId), cancellationToken);
+            database.UserAlbums.Remove(album);
+
+            try
+            {
                 await database.SaveChangesAsync(cancellationToken);
+            }
+            catch (Exception exception)
+            {
+                logger.LogError(exception, "Failed to delete album {AlbumId}", request.AlbumId);
+                return Error.Failure(description: $"Failed to delete album {request.AlbumId}");
+            }
 
-            logger.LogInformation("Marked album {AlbumId} as removing", request.AlbumId);
+            logger.LogInformation("Deleted album {AlbumId} for user {UserId}", request.AlbumId, request.UserId);
 
-            return Result.Success;
+            return new Success();
         }
     }
 }

backend/Core/Musify.Application/Albums/GetAlbumById.cs

@@ -3,7 +3,6 @@ using Mediator;
 using Microsoft.EntityFrameworkCore;
 using Musify.Application.Albums.Responses;
 using Musify.Application.Contracts;
-using Musify.Application.Shared;
 
 namespace Musify.Application.Albums
 {
@@ -15,16 +14,25 @@ namespace Musify.Application.Albums
     {
         public async ValueTask<ErrorOr<AlbumApplicationResponse>> Handle(GetAlbumByIdQuery request, CancellationToken cancellationToken)
         {
-            var album = await database.Albums
+            var album = await database.UserAlbums
                 .AsNoTracking()
-                .Active()
                 .Where(a => a.Id == request.Id)
-                .SelectResponse()
+                .Select(a => new
+                {
+                    Album = a,
+                    TrackCount = a.AlbumTracks.Count,
+                    CoverTrackIds = a.AlbumTracks
+                        .OrderBy(albumTrack => albumTrack.TrackNumber)
+                        .Take(AlbumApplicationResponse.CoverTrackCount)
+                        .Select(albumTrack => albumTrack.TrackId)
+                        .ToList()
+                })
                 .SingleOrDefaultAsync(cancellationToken);
 
-            return album == null
-                ? AppErrors.NotFound("Album", request.Id)
-                : album;
+            if (album is null)
+                return Error.NotFound();
+
+            return AlbumApplicationResponse.FromEntity(album.Album, album.TrackCount, album.CoverTrackIds);
         }
     }
 }

backend/Core/Musify.Application/Albums/GetAlbumCover.cs

@@ -0,0 +1,49 @@
+using ErrorOr;
+using Mediator;
+using Microsoft.EntityFrameworkCore;
+using MimeMapping;
+using Musify.Application.Configuration;
+using Musify.Application.Contracts;
+
+namespace Musify.Application.Albums
+{
+    public record GetAlbumCoverQuery(Guid AlbumId, string Size)
+        : IQuery<ErrorOr<AlbumCoverLocation>>;
+
+    public record AlbumCoverLocation(string Bucket, string Key, string ContentType);
+
+    public class GetAlbumCoverQueryHandler(
+        IDatabase database,
+        ApplicationStorageConfiguration storageConfiguration,
+        AlbumConfiguration albumConfiguration)
+        : IQueryHandler<GetAlbumCoverQuery, ErrorOr<AlbumCoverLocation>>
+    {
+        public async ValueTask<ErrorOr<AlbumCoverLocation>> Handle(GetAlbumCoverQuery request, CancellationToken cancellationToken)
+        {
+            var pictures = await database.Albums.AsNoTracking()
+                .Where(a => a.Id == request.AlbumId)
+                .Select(a => a.Pictures)
+                .SingleOrDefaultAsync(cancellationToken);
+
+            if (pictures is null)
+                return Error.NotFound();
+
+            var routes = albumConfiguration.Routes;
+            var (name, key) = request.Size.ToLowerInvariant() switch
+            {
+                "small" => (pictures.SmallName, BuildKey(routes.BuildSmallPicturePath, pictures.SmallName)),
+                "large" => (pictures.LargeName, BuildKey(routes.BuildLargePicturePath, pictures.LargeName)),
+                _ => (pictures.MediumName, BuildKey(routes.BuildMediumPicturePath, pictures.MediumName))
+            };
+
+            if (string.IsNullOrEmpty(name) || string.IsNullOrEmpty(key))
+                return Error.NotFound();
+
+            var contentType = MimeUtility.GetMimeMapping(name);
+            return new AlbumCoverLocation(storageConfiguration.Bucket, key, contentType);
+        }
+
+        private static string? BuildKey(Func<string, string> builder, string? name)
+            => string.IsNullOrEmpty(name) ? null : builder(name);
+    }
+}

backend/Core/Musify.Application/Albums/GetAlbumTracks.cs

@@ -1,10 +1,12 @@
 using ErrorOr;
 using Mediator;
 using Microsoft.EntityFrameworkCore;
-using Musify.Application.Albums.Responses;
 using Musify.Application.Contracts;
 using Musify.Application.Shared;
 using Musify.Application.Tracks.Responses;
+using Musify.Domain.Entities;
+using X.PagedList;
+using X.PagedList.EF;
 
 namespace Musify.Application.Albums
 {
@@ -21,19 +23,29 @@ namespace Musify.Application.Albums
         {
             var albumExists = await database.Albums
                 .AsNoTracking()
-                .Active()
                 .AnyAsync(album => album.Id == request.AlbumId, cancellationToken);
             if (!albumExists)
-                return AppErrors.NotFound("Album", request.AlbumId);
+                return Error.NotFound();
 
-            return await database.AlbumHasTracks
+            var tracksQuery = database.AlbumHasTracks
                 .AsNoTracking()
-                .Where(albumTrack => albumTrack.AlbumId == request.AlbumId && albumTrack.Track.LifeCycleStatus == Domain.ValueObjects.LifeCycleStatus.Active)
+                .Include(albumTrack => ((ExternalTrack)albumTrack.Track).TrackArtists)
+                    .ThenInclude(trackArtist => trackArtist.Artist)
+                .Include(albumTrack => ((LocalTrack)albumTrack.Track).Owner)
+                .Where(albumTrack => albumTrack.AlbumId == request.AlbumId);
+
+            var totalCount = await tracksQuery.CountAsync(cancellationToken);
+
+            var pagedEntities = await tracksQuery
                 .OrderBy(albumTrack => albumTrack.TrackNumber)
-                .ThenBy(albumTrack => albumTrack.Id)
-                .Select(albumTrack => albumTrack.Track)
-                .SelectResponse()
-                .ToPaginatedAsync(new PageRequest(request.PageNumber, request.PageSize), cancellationToken);
+                .Select(albumTrack => new { albumTrack.Track, ListensCount = albumTrack.Track.ListeningHistories.Count })
+                .ToPagedListAsync(request.PageNumber, request.PageSize, totalCount, cancellationToken);
+
+            var pagedTracks = new StaticPagedList<TrackApplicationResponse>(
+                pagedEntities.Select(entry => TrackApplicationResponse.FromEntity(entry.Track, entry.ListensCount)),
+                pagedEntities.PageNumber, pagedEntities.PageSize, pagedEntities.TotalItemCount);
+
+            return PaginatedResponse<TrackApplicationResponse>.FromPagedList(pagedTracks);
         }
     }
 }

backend/Core/Musify.Application/Albums/GetAlbums.cs

@@ -1,34 +1,113 @@
+using ErrorOr;
 using Mediator;
 using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.Logging;
 using Musify.Application.Albums.Responses;
 using Musify.Application.Contracts;
-using Musify.Application.Shared;
+using Musify.Domain.Entities;
+using Musify.Domain.ValueObjects;
+using X.PagedList;
+using X.PagedList.EF;
 
 namespace Musify.Application.Albums
 {
-    public record GetAlbumsQuery(string? Title, int PageNumber, int PageSize)
-        : IQuery<PaginatedResponse<AlbumApplicationResponse>>;
+    public record GetAlbumsQuery(string? Title, int PageNumber, int PageSize, string? YoutubeContinuationToken = null)
+        : IQuery<ErrorOr<AlbumsSearchResponse>>;
 
-    public class GetAlbumsQueryHandler(IDatabase database)
-        : IQueryHandler<GetAlbumsQuery, PaginatedResponse<AlbumApplicationResponse>>
+    public class GetAlbumsQueryHandler(
+        IDatabase database,
+        IYouTubeMusicService youTubeMusicService,
+        ILogger<GetAlbumsQueryHandler> logger)
+        : IQueryHandler<GetAlbumsQuery, ErrorOr<AlbumsSearchResponse>>
     {
-        public async ValueTask<PaginatedResponse<AlbumApplicationResponse>> Handle(GetAlbumsQuery request, CancellationToken cancellationToken)
+        // Mirrors GetTracksQueryHandler's threshold: a title shorter than this is too likely to
+        // still be mid-keystroke to justify a live call to the external search API.
+        private const int MinTitleLengthForYouTubeSearch = 2;
+
+        public async ValueTask<ErrorOr<AlbumsSearchResponse>> Handle(GetAlbumsQuery request, CancellationToken cancellationToken)
         {
             var albumsQuery = database.Albums
                 .AsNoTracking()
-                .Active();
+                .AsQueryable();
 
-            if (!string.IsNullOrWhiteSpace(request.Title))
+            if (!string.IsNullOrEmpty(request.Title))
             {
-                var normalizedTitle = TextNormalizer.Normalize(request.Title);
+                var normalizedTitle = request.Title.Trim().ToUpperInvariant();
                 albumsQuery = albumsQuery.Where(album => album.NormalizedTitle.Contains(normalizedTitle));
             }
 
-            return await albumsQuery
+            var totalCount = await albumsQuery.CountAsync(cancellationToken);
+
+            var pagedEntities = await albumsQuery
                 .OrderByDescending(album => album.CreatedAt)
-                .ThenBy(album => album.Id)
-                .SelectResponse()
-                .ToPaginatedAsync(new PageRequest(request.PageNumber, request.PageSize), cancellationToken);
+                .Select(album => new
+                {
+                    Album = album,
+                    TrackCount = album.AlbumTracks.Count,
+                    CoverTrackIds = album.AlbumTracks
+                        .OrderBy(albumTrack => albumTrack.TrackNumber)
+                        .Take(AlbumApplicationResponse.CoverTrackCount)
+                        .Select(albumTrack => albumTrack.TrackId)
+                        .ToList()
+                })
+                .ToPagedListAsync(request.PageNumber, request.PageSize, totalCount, cancellationToken);
+
+            var localItems = pagedEntities
+                .Select(entry => AlbumSearchItemResponse.FromAlbum(
+                    AlbumApplicationResponse.FromEntity(entry.Album, entry.TrackCount, entry.CoverTrackIds)))
+                .ToList();
+
+            var knownExternalIds = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
+            foreach (var entry in pagedEntities)
+            {
+                if (entry.Album is ExternalAlbum { Source: TrackSource.YouTube } external)
+                    knownExternalIds.Add(external.ExternalId);
+            }
+
+            var youtubeItems = new List<AlbumSearchItemResponse>();
+            string? nextContinuationToken = null;
+            var youtubeUnavailable = false;
+
+            if (request.Title?.Trim().Length >= MinTitleLengthForYouTubeSearch)
+                (youtubeItems, nextContinuationToken, youtubeUnavailable) =
+                    await SearchYouTubeAsync(request.Title, request.YoutubeContinuationToken, knownExternalIds, cancellationToken);
+
+            return AlbumsSearchResponse.Create(
+                [.. localItems, .. youtubeItems],
+                pagedEntities.PageNumber,
+                pagedEntities.PageSize,
+                pagedEntities.PageCount,
+                pagedEntities.TotalItemCount,
+                pagedEntities.HasPreviousPage,
+                pagedEntities.HasNextPage,
+                nextContinuationToken,
+                youtubeUnavailable);
+        }
+
+        private async Task<(List<AlbumSearchItemResponse> Items, string? NextContinuationToken, bool Unavailable)> SearchYouTubeAsync(
+            string title,
+            string? continuationToken,
+            HashSet<string> knownExternalIds,
+            CancellationToken cancellationToken)
+        {
+            var searchResult = await youTubeMusicService.SearchAlbumsAsync(title, continuationToken ?? string.Empty, cancellationToken);
+            if (searchResult.IsError)
+            {
+                logger.LogInformation(
+                    "YouTube album search unavailable while combining album results: {Error}", searchResult.FirstError.Description);
+                return ([], null, true);
+            }
+
+            var items = searchResult.Value.Items
+                .Where(album => knownExternalIds.Add(album.AlbumId))
+                .Select(AlbumSearchItemResponse.FromYouTubeAlbum)
+                .ToList();
+
+            var nextToken = string.IsNullOrEmpty(searchResult.Value.ContinuationToken)
+                ? null
+                : searchResult.Value.ContinuationToken;
+
+            return (items, nextToken, false);
         }
     }
 }

backend/Core/Musify.Application/Albums/GetAlbumsByUserId.cs

@@ -4,6 +4,8 @@ using Microsoft.EntityFrameworkCore;
 using Musify.Application.Albums.Responses;
 using Musify.Application.Contracts;
 using Musify.Application.Shared;
+using X.PagedList;
+using X.PagedList.EF;
 
 namespace Musify.Application.Albums
 {
@@ -19,16 +21,33 @@ namespace Musify.Application.Albums
                 .AsNoTracking()
                 .AnyAsync(user => user.Id == request.UserId, cancellationToken);
             if (!userExists)
-                return AppErrors.NotFound("User", request.UserId);
+                return Error.NotFound(description: $"User {request.UserId} not found");
 
-            return await database.Albums
+            var albumsQuery = database.UserAlbums
                 .AsNoTracking()
-                .Active()
-                .Where(album => album.OwnerUserId == request.UserId)
+                .Where(album => album.OwnerUserId == request.UserId);
+
+            var totalCount = await albumsQuery.CountAsync(cancellationToken);
+
+            var pagedEntities = await albumsQuery
                 .OrderByDescending(album => album.CreatedAt)
-                .ThenBy(album => album.Id)
-                .SelectResponse()
-                .ToPaginatedAsync(new PageRequest(request.PageNumber, request.PageSize), cancellationToken);
+                .Select(album => new
+                {
+                    Album = album,
+                    TrackCount = album.AlbumTracks.Count,
+                    CoverTrackIds = album.AlbumTracks
+                        .OrderBy(albumTrack => albumTrack.TrackNumber)
+                        .Take(AlbumApplicationResponse.CoverTrackCount)
+                        .Select(albumTrack => albumTrack.TrackId)
+                        .ToList()
+                })
+                .ToPagedListAsync(request.PageNumber, request.PageSize, totalCount, cancellationToken);
+
+            var pagedAlbums = new StaticPagedList<AlbumApplicationResponse>(
+                pagedEntities.Select(entry => AlbumApplicationResponse.FromEntity(entry.Album, entry.TrackCount, entry.CoverTrackIds)),
+                pagedEntities.PageNumber, pagedEntities.PageSize, pagedEntities.TotalItemCount);
+
+            return PaginatedResponse<AlbumApplicationResponse>.FromPagedList(pagedAlbums);
         }
     }
 }

backend/Core/Musify.Application/Albums/GetRecentlyListenedAlbums.cs

@@ -1,3 +1,4 @@
+using ErrorOr;
 using Mediator;
 using Microsoft.EntityFrameworkCore;
 using Musify.Application.Albums.Responses;
@@ -6,46 +7,54 @@ using Musify.Application.Contracts;
 namespace Musify.Application.Albums
 {
     public record GetRecentlyListenedAlbumsQuery(long UserId, int Limit)
-        : IQuery<IReadOnlyList<AlbumApplicationResponse>>;
+        : IQuery<ErrorOr<IReadOnlyList<AlbumApplicationResponse> >>;
 
     public class GetRecentlyListenedAlbumsQueryHandler(IDatabase database)
-        : IQueryHandler<GetRecentlyListenedAlbumsQuery, IReadOnlyList<AlbumApplicationResponse>>
+        : IQueryHandler<GetRecentlyListenedAlbumsQuery, ErrorOr<IReadOnlyList<AlbumApplicationResponse>>>
     {
-        public async ValueTask<IReadOnlyList<AlbumApplicationResponse>> Handle(GetRecentlyListenedAlbumsQuery request, CancellationToken cancellationToken)
+        public async ValueTask<ErrorOr<IReadOnlyList<AlbumApplicationResponse>>> Handle(GetRecentlyListenedAlbumsQuery request, CancellationToken cancellationToken)
         {
-            var listens = database.ListeningHistories
+            var listenedTrackIds = database.ListeningHistories
                 .AsNoTracking()
-                .Where(history => history.UserId == request.UserId && history.IsCounted);
+                .Where(history => history.UserId == request.UserId);
 
             var ranked = await database.AlbumHasTracks
                 .AsNoTracking()
-                .Where(albumTrack => albumTrack.Album.LifeCycleStatus == Domain.ValueObjects.LifeCycleStatus.Active)
                 .Join(
-                    listens,
+                    listenedTrackIds,
                     albumTrack => albumTrack.TrackId,
                     history => history.TrackId,
-                    (albumTrack, history) => new { albumTrack.AlbumId, history.ListenedAt })
+                    (albumTrack, history) => new { albumTrack.AlbumId, history.ListenedAt } )
                 .GroupBy(entry => entry.AlbumId)
-                .Select(group => new { AlbumId = group.Key, LastListenedAt = group.Max(entry => entry.ListenedAt) })
+                .Select(group => new { AlbumId = group.Key, LastListenedAt = group.Max(entry => entry.ListenedAt) } )
                 .OrderByDescending(entry => entry.LastListenedAt)
-                .ThenBy(entry => entry.AlbumId)
                 .Take(request.Limit)
                 .ToListAsync(cancellationToken);
 
             if (ranked.Count == 0)
-                return [];
+                return new List<AlbumApplicationResponse>();
 
             var albumIds = ranked.Select(entry => entry.AlbumId).ToList();
 
-            var albumsById = await database.Albums
+            var albums = await database.Albums
                 .AsNoTracking()
                 .Where(album => albumIds.Contains(album.Id))
-                .SelectResponse()
-                .ToDictionaryAsync(album => album.Id, cancellationToken);
+                .Select(album => new
+                {
+                    Album = album,
+                    TrackCount = album.AlbumTracks.Count,
+                    CoverTrackIds = album.AlbumTracks
+                        .OrderBy(albumTrack => albumTrack.TrackNumber)
+                        .Take(AlbumApplicationResponse.CoverTrackCount)
+                        .Select(albumTrack => albumTrack.TrackId)
+                        .ToList()
+                } )
+                .ToDictionaryAsync(entry => entry.Album.Id, cancellationToken);
 
             return ranked
-                .Where(entry => albumsById.ContainsKey(entry.AlbumId))
-                .Select(entry => albumsById[entry.AlbumId])
+                .Where(entry => albums.ContainsKey(entry.AlbumId))
+                .Select(entry => albums[entry.AlbumId])
+                .Select(entry => AlbumApplicationResponse.FromEntity(entry.Album, entry.TrackCount, entry.CoverTrackIds))
                 .ToList();
         }
     }

backend/Core/Musify.Application/Albums/RemoveTrackFromAlbum.cs

@@ -3,7 +3,6 @@ using Mediator;
 using Microsoft.EntityFrameworkCore;
 using Microsoft.Extensions.Logging;
 using Musify.Application.Contracts;
-using Musify.Application.Shared;
 
 namespace Musify.Application.Albums
 {
@@ -17,9 +16,20 @@ namespace Musify.Application.Albums
     {
         public async ValueTask<ErrorOr<Success>> Handle(RemoveTrackFromAlbumCommand request, CancellationToken cancellationToken)
         {
-            var album = await database.Albums.FindOwnedAsync(request.AlbumId, request.UserId, cancellationToken);
-            if (album.IsError)
-                return album.Errors;
+            var album = await database.UserAlbums
+                .AsNoTracking()
+                .SingleOrDefaultAsync(a => a.Id == request.AlbumId, cancellationToken);
+            if (album is null)
+            {
+                logger.LogInformation("Album {AlbumId} not found", request.AlbumId);
+                return Error.NotFound();
+            }
+
+            if (album.OwnerUserId != request.UserId)
+            {
+                logger.LogWarning("User {UserId} is not the owner of album {AlbumId}", request.UserId, request.AlbumId);
+                return Error.Unauthorized();
+            }
 
             var albumTracks = await database.AlbumHasTracks
                 .Where(albumTrack => albumTrack.AlbumId == request.AlbumId)
@@ -27,8 +37,11 @@ namespace Musify.Application.Albums
                 .ToListAsync(cancellationToken);
 
             var link = albumTracks.SingleOrDefault(albumTrack => albumTrack.TrackId == request.TrackId);
-            if (link == null)
-                return Error.NotFound("Album.TrackNotFound", "Track is not in the album.");
+            if (link is null)
+            {
+                logger.LogInformation("Track {TrackId} not in album {AlbumId}", request.TrackId, request.AlbumId);
+                return Error.NotFound(description: "Track is not in the album.");
+            }
 
             database.AlbumHasTracks.Remove(link);
 
@@ -40,7 +53,7 @@ namespace Musify.Application.Albums
 
             logger.LogInformation("Removed track {TrackId} from album {AlbumId}", request.TrackId, request.AlbumId);
 
-            return Result.Success;
+            return new Success();
         }
     }
 }

backend/Core/Musify.Application/Albums/RequestAlbumPictureUpload.cs

@@ -1,9 +1,13 @@
 using ErrorOr;
 using Mediator;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.Logging;
 using Musify.Application.Configuration;
-using Musify.Application.Pictures.Responses;
+using Musify.Application.Albums.Responses;
 using Musify.Application.Services;
+using Musify.Domain.Entities;
 using Musify.Domain.ValueObjects;
+using Musify.Application.Contracts;
 
 namespace Musify.Application.Albums
 {
@@ -12,14 +16,90 @@ namespace Musify.Application.Albums
         string FileType,
         string ContentType,
         long? ExpectedSizeBytes = null)
-        : ICommand<ErrorOr<PictureUploadResponse>>;
+        : ICommand<ErrorOr<AlbumPictureUploadResponse>>;
 
-    public class RequestAlbumPictureUploadCommandHandler(UploadIntentIssuer issuer, AlbumConfiguration albumConfiguration)
-        : ICommandHandler<RequestAlbumPictureUploadCommand, ErrorOr<PictureUploadResponse>>
+    public class RequestAlbumPictureUploadCommandHandler(
+        IDatabase database,
+        UploadIntentValidator uploadIntentValidator,
+        IStorageService storageService,
+        ILogger<RequestAlbumPictureUploadCommandHandler> logger,
+        ApplicationStorageConfiguration storageConfiguration,
+        AlbumConfiguration albumConfiguration,
+        UploadIntentConfiguration uploadIntentConfiguration)
+        : ICommandHandler<RequestAlbumPictureUploadCommand, ErrorOr<AlbumPictureUploadResponse>>
     {
-        public async ValueTask<ErrorOr<PictureUploadResponse>> Handle(RequestAlbumPictureUploadCommand request, CancellationToken cancellationToken) =>
-            await issuer.IssuePictureAsync(
-                request.UserId, UploadIntentPurpose.AlbumPicture, albumConfiguration,
-                request.FileType, request.ContentType, request.ExpectedSizeBytes, cancellationToken);
+        public async ValueTask<ErrorOr<AlbumPictureUploadResponse>> Handle(RequestAlbumPictureUploadCommand request, CancellationToken cancellationToken)
+        {
+            var userExists = await database.Users
+                .AsNoTracking()
+                .AnyAsync(u => u.Id == request.UserId, cancellationToken);
+            if (!userExists)
+            {
+                logger.LogWarning("User {UserId} not found", request.UserId);
+                return Error.NotFound(description: $"User {request.UserId} not found");
+            }
+
+            var effectiveSizeBytes = request.ExpectedSizeBytes
+                ?? uploadIntentConfiguration.DefaultExpectedPictureSizeBytes;
+
+            var objectName = $"{Guid.NewGuid() }.{request.FileType.TrimStart('.').ToLowerInvariant() }";
+
+            var tempKey = albumConfiguration.Routes.BuildTempPicturePath(
+                uploadIntentConfiguration.TemporalRootPrefix, request.UserId, objectName);
+
+            try
+            {
+                var uploadUrl = await storageService.GetUploadUrlAsync(
+                    storageConfiguration.Bucket,
+                    tempKey,
+                    request.ContentType,
+                    TimeSpan.FromSeconds(uploadIntentConfiguration.UploadUrlExpiresInSeconds),
+                    cancellationToken);
+
+                await using var transaction = await database.BeginTransactionAsync(
+                    System.Data.IsolationLevel.Serializable, cancellationToken);
+
+                var quotaCheck = await uploadIntentValidator.CheckQuotaAsync(
+                    uploadIntentConfiguration,
+                    request.UserId, effectiveSizeBytes, 1, cancellationToken);
+                if (quotaCheck.IsError)
+                {
+                    logger.LogWarning("User {UserId} failed upload intent quota check", request.UserId);
+                    return quotaCheck.Errors;
+                }
+
+                var intent = new UploadIntent
+                {
+                    UserId = request.UserId,
+                    Bucket = storageConfiguration.Bucket,
+                    Key = tempKey,
+                    ObjectName = objectName,
+                    ContentType = request.ContentType,
+                    ExpectedSizeBytes = effectiveSizeBytes,
+                    Purpose = UploadIntentPurpose.AlbumPicture,
+                    ExpiresAt = DateTime.UtcNow.AddSeconds(uploadIntentConfiguration.UploadUrlExpiresInSeconds),
+                };
+
+                await database.UploadIntents.AddAsync(intent, cancellationToken);
+                await database.SaveChangesAsync(cancellationToken);
+                await transaction.CommitAsync(cancellationToken);
+
+                logger.LogInformation("Issued upload intent {IntentId} for user {UserId} (AlbumPicture, temp key: {Key} )", intent.Id, request.UserId, tempKey);
+
+                return new AlbumPictureUploadResponse(
+                    intent.Id,
+                    storageConfiguration.Bucket,
+                    tempKey,
+                    objectName,
+                    request.ContentType,
+                    uploadIntentConfiguration.UploadUrlExpiresInSeconds,
+                    uploadUrl);
+            }
+            catch (Exception exception)
+            {
+                logger.LogError(exception, "Failed to generate album picture upload URL for user {UserId}", request.UserId);
+                return Error.Failure(description: "Failed to generate upload URL");
+            }
+        }
     }
 }

backend/Core/Musify.Application/Albums/Responses/AlbumApplicationResponse.cs

@@ -1,7 +1,17 @@
+using System.Text.Json.Serialization;
 using Musify.Domain.Entities;
 
 namespace Musify.Application.Albums.Responses
 {
+    // [JsonPolymorphic]/[JsonDerivedType] are required here, not optional: without them
+    // System.Text.Json serializes strictly by the declared CLR type at each call site
+    // (AlbumApplicationResponse, both as a bare return type and nested inside
+    // AlbumSearchItemResponse.Album), so an ExternalAlbumApplicationResponse instance would
+    // silently lose ExternalId/ThumbnailUrl on the wire. This also gives every response a
+    // "source" discriminator field for free, matching AlbumSearchItemResponse.Source.
+    [JsonPolymorphic(TypeDiscriminatorPropertyName = "source")]
+    [JsonDerivedType(typeof(AlbumApplicationResponse), typeDiscriminator: "Local")]
+    [JsonDerivedType(typeof(ExternalAlbumApplicationResponse), typeDiscriminator: "YouTube")]
     public record AlbumApplicationResponse(
         Guid Id,
         string Title,
@@ -16,10 +26,10 @@ namespace Musify.Application.Albums.Responses
         DateTime UpdatedAt,
         IReadOnlyList<Guid> CoverTrackIds)
     {
-        public const int CoverTrackCount = AlbumProjections.CoverTrackCount;
+        public const int CoverTrackCount = 4;
 
         public static AlbumApplicationResponse FromEntity(
-            Album album,
+            UserAlbum album,
             int trackCount,
             IReadOnlyList<Guid>? coverTrackIds = null)
         {
@@ -37,5 +47,18 @@ namespace Musify.Application.Albums.Responses
                 album.UpdatedAt,
                 coverTrackIds ?? []);
         }
+
+        public static AlbumApplicationResponse FromEntity(
+            Album album,
+            int trackCount,
+            IReadOnlyList<Guid>? coverTrackIds = null)
+        {
+            return album switch
+            {
+                ExternalAlbum externalAlbum => ExternalAlbumApplicationResponse.FromEntity(externalAlbum, trackCount, coverTrackIds),
+                UserAlbum userAlbum => FromEntity(userAlbum, trackCount, coverTrackIds),
+                _ => throw new NotSupportedException($"Unsupported album entity type '{album.GetType().Name}'.")
+            };
+        }
     }
 }

backend/Core/Musify.Application/Albums/Responses/AlbumPictureUploadResponse.cs

@@ -1,6 +1,6 @@
-namespace Musify.Application.Pictures.Responses
+namespace Musify.Application.Albums.Responses
 {
-    public record PictureUploadResponse(
+    public record AlbumPictureUploadResponse(
         Guid IntentId,
         string Bucket,
         string Key,

backend/Core/Musify.Application/Albums/Responses/AlbumProjections.cs

@@ -1,32 +0,0 @@
-using Musify.Domain.Entities;
-using Musify.Domain.ValueObjects;
-
-namespace Musify.Application.Albums.Responses
-{
-    public static class AlbumProjections
-    {
-        public const int CoverTrackCount = 4;
-
-        public static IQueryable<Album> Active(this IQueryable<Album> query) =>
-            query.Where(album => album.LifeCycleStatus == LifeCycleStatus.Active);
-
-        public static IQueryable<AlbumApplicationResponse> SelectResponse(this IQueryable<Album> query) =>
-            query.Select(album => new AlbumApplicationResponse(
-                album.Id,
-                album.Title,
-                album.Description,
-                album.ReleaseYear,
-                album.OwnerUserId,
-                album.AlbumTracks.Count,
-                album.Pictures!.SmallName,
-                album.Pictures!.MediumName,
-                album.Pictures!.LargeName,
-                album.CreatedAt,
-                album.UpdatedAt,
-                album.AlbumTracks
-                    .OrderBy(albumTrack => albumTrack.TrackNumber)
-                    .Take(CoverTrackCount)
-                    .Select(albumTrack => albumTrack.TrackId)
-                    .ToList()));
-    }
-}

backend/Core/Musify.Application/Albums/Responses/AlbumSearchItemResponse.cs

@@ -0,0 +1,22 @@
+using Musify.Application.Contracts;
+using Musify.Domain.ValueObjects;
+
+namespace Musify.Application.Albums.Responses
+{
+    /// <summary>One item of a combined local/external album listing. Exactly one of
+    /// <see cref="Album"/> or <see cref="YouTubeAlbum"/> is populated: <see cref="Album"/> for
+    /// anything already in the catalog (locally created albums and external albums materialized
+    /// earlier), <see cref="YouTubeAlbum"/> for a live external search hit that hasn't been
+    /// materialized yet, so it has no album id.</summary>
+    public record AlbumSearchItemResponse(
+        TrackSource Source,
+        AlbumApplicationResponse? Album,
+        YouTubeAlbumResult? YouTubeAlbum)
+    {
+        public static AlbumSearchItemResponse FromAlbum(AlbumApplicationResponse album) =>
+            new(album is ExternalAlbumApplicationResponse ? TrackSource.YouTube : TrackSource.Local, album, null);
+
+        public static AlbumSearchItemResponse FromYouTubeAlbum(YouTubeAlbumResult album) =>
+            new(TrackSource.YouTube, null, album);
+    }
+}

backend/Core/Musify.Application/Albums/Responses/AlbumsSearchResponse.cs

@@ -0,0 +1,38 @@
+namespace Musify.Application.Albums.Responses
+{
+    /// <summary>Result of a combined albums listing/search: a page of local catalog albums
+    /// (user-created and previously materialized external albums), plus, when a search term was
+    /// given, live external hits appended after them. Pagination metadata (<see cref="PageNumber"/>,
+    /// <see cref="PageSize"/>, <see cref="PageCount"/>, <see cref="TotalItemCount"/>) describes only
+    /// the local page — the external source has no stable total, so its continuation is tracked
+    /// separately via <see cref="NextYoutubeContinuationToken"/>.</summary>
+    public record AlbumsSearchResponse(
+        IReadOnlyList<AlbumSearchItemResponse> Items,
+        int PageNumber,
+        int PageSize,
+        int PageCount,
+        int TotalItemCount,
+        bool HasPreviousPage,
+        bool HasNextLocalPage,
+        string? NextYoutubeContinuationToken,
+        bool YoutubeUnavailable,
+        bool HasNextPage)
+    {
+        // HasNextPage is a real field (not a computed property) so it shows up as a required member
+        // of the generated OpenAPI schema, same as every other field here — a get-only property added
+        // outside the primary constructor gets reflected as optional instead, which is never true here.
+        public static AlbumsSearchResponse Create(
+            IReadOnlyList<AlbumSearchItemResponse> items,
+            int pageNumber,
+            int pageSize,
+            int pageCount,
+            int totalItemCount,
+            bool hasPreviousPage,
+            bool hasNextLocalPage,
+            string? nextYoutubeContinuationToken,
+            bool youtubeUnavailable) =>
+            new(items, pageNumber, pageSize, pageCount, totalItemCount, hasPreviousPage, hasNextLocalPage,
+                nextYoutubeContinuationToken, youtubeUnavailable,
+                HasNextPage: hasNextLocalPage || !string.IsNullOrEmpty(nextYoutubeContinuationToken));
+    }
+}

backend/Core/Musify.Application/Albums/Responses/ExternalAlbumApplicationResponse.cs

@@ -0,0 +1,47 @@
+using Musify.Domain.Entities;
+
+namespace Musify.Application.Albums.Responses
+{
+    public record ExternalAlbumApplicationResponse(
+        Guid Id,
+        string Title,
+        string? Description,
+        int? ReleaseYear,
+        long OwnerUserId,
+        int TrackCount,
+        string? SmallImageKeyName,
+        string? MediumImageKeyName,
+        string? LargeImageKeyName,
+        DateTime CreatedAt,
+        DateTime UpdatedAt,
+        IReadOnlyList<Guid> CoverTrackIds,
+        string ExternalId,
+        string? ThumbnailUrl)
+        : AlbumApplicationResponse(
+            Id, Title, Description, ReleaseYear, OwnerUserId, TrackCount,
+            SmallImageKeyName, MediumImageKeyName, LargeImageKeyName,
+            CreatedAt, UpdatedAt, CoverTrackIds)
+    {
+        public static ExternalAlbumApplicationResponse FromEntity(
+            ExternalAlbum album,
+            int trackCount,
+            IReadOnlyList<Guid>? coverTrackIds = null)
+        {
+            return new ExternalAlbumApplicationResponse(
+                album.Id,
+                album.Title,
+                album.Description,
+                album.ReleaseYear,
+                0,
+                trackCount,
+                album.Pictures?.SmallName,
+                album.Pictures?.MediumName,
+                album.Pictures?.LargeName,
+                album.CreatedAt,
+                album.UpdatedAt,
+                coverTrackIds ?? [],
+                album.ExternalId,
+                album.ThumbnailUrl);
+        }
+    }
+}

backend/Core/Musify.Application/Albums/UpdateAlbum.cs

@@ -2,14 +2,14 @@ using ErrorOr;
 using Mediator;
 using Microsoft.EntityFrameworkCore;
 using Microsoft.Extensions.Logging;
-using Musify.Application.Albums.Responses;
 using Musify.Application.Configuration;
-using Musify.Application.Contracts;
-using Musify.Application.Events;
-using Musify.Application.Pictures;
-using Musify.Application.Services;
 using Musify.Application.Shared;
+using Musify.Application.Events;
+using Musify.Application.Albums.Responses;
+using Musify.Application.Services;
+using Musify.Domain.Entities;
 using Musify.Domain.ValueObjects;
+using Musify.Application.Contracts;
 
 namespace Musify.Application.Albums
 {
@@ -27,48 +27,126 @@ namespace Musify.Application.Albums
         IDatabase database,
         UploadIntentValidator uploadIntentValidator,
         ILogger<UpdateAlbumCommandHandler> logger,
-        AlbumConfiguration albumConfiguration)
+        ApplicationStorageConfiguration storageConfiguration,
+        AlbumConfiguration albumConfiguration,
+        UploadIntentConfiguration uploadIntentConfiguration)
         : ICommandHandler<UpdateAlbumCommand, ErrorOr<AlbumApplicationResponse>>
     {
         public async ValueTask<ErrorOr<AlbumApplicationResponse>> Handle(UpdateAlbumCommand request, CancellationToken cancellationToken)
         {
-            var found = await database.Albums.FindOwnedAsync(request.AlbumId, request.UserId, cancellationToken);
-            if (found.IsError)
-                return found.Errors;
+            var album = await database.UserAlbums
+                .SingleOrDefaultAsync(a => a.Id == request.AlbumId, cancellationToken);
+            if (album is null)
+            {
+                logger.LogInformation("Album {AlbumId} not found", request.AlbumId);
+                return Error.NotFound();
+            }
+
+            if (album.OwnerUserId != request.UserId)
+            {
+                logger.LogWarning("Album {AlbumId} does not belong to user {UserId}", request.AlbumId, request.UserId);
+                return Error.Unauthorized();
+            }
 
-            var album = found.Value;
             var title = request.Title.Trim();
 
             album.Title = title;
-            album.NormalizedTitle = TextNormalizer.Normalize(title);
+            album.NormalizedTitle = title.ToUpperInvariant();
             album.Description = request.Description;
             album.ReleaseYear = request.ReleaseYear;
 
-            if (request.NewPictureIntentId is { } intentId)
+            UploadIntent? pictureIntent = null;
+            string? finalPictureKey = null;
+
+            if (request.NewPictureIntentId.HasValue)
             {
-                var prepared = await PictureSourceChange.PrepareAsync(
-                    uploadIntentValidator, intentId, request.UserId, UploadIntentPurpose.AlbumPicture, albumConfiguration, cancellationToken);
-                if (prepared.IsError)
-                    return prepared.Errors;
+                var validation = await uploadIntentValidator.ValidateAndLoadAsync(
+                    uploadIntentConfiguration,
+                    request.NewPictureIntentId.Value, request.UserId, cancellationToken);
+                if (validation.IsError)
+                    return validation.Errors;
 
-                var picture = prepared.Value;
-                album.Pictures = picture.Pictures;
-
-                await eventBus.PublishAsync(
-                    new UpdateAlbumPictureSourceEvent(
-                        album.Id, picture.Intent.Id, picture.Intent.Bucket, picture.Intent.Key, picture.FinalKey, picture.Sizes),
-                    cancellationToken);
+                pictureIntent = validation.Value;
+                album.Pictures = new AlbumPictures
+                {
+                    OriginalName = pictureIntent.ObjectName,
+                    SmallName = pictureIntent.ObjectName,
+                    MediumName = pictureIntent.ObjectName,
+                    LargeName = pictureIntent.ObjectName
+                };
+                finalPictureKey = albumConfiguration.Routes.BuildOriginalPicturePath(request.UserId, pictureIntent.ObjectName);
             }
 
+            database.UserAlbums.Update(album);
+
+            if (pictureIntent != null && finalPictureKey != null)
+            {
+                var publishResult = await PublishUpdateAlbumPictureSourceEventAsync(
+                    album.Id, pictureIntent, finalPictureKey, cancellationToken);
+                if (publishResult.IsError)
+                    return publishResult.Errors;
+            }
+
+            try
+            {
                 await database.SaveChangesAsync(cancellationToken);
+            }
+            catch (Exception exception)
+            {
+                logger.LogError(exception, "Failed to update album {AlbumId}", request.AlbumId);
+                return Error.Failure(description: $"Failed to update album {request.AlbumId}");
+            }
+
+            var albumTracks = database.AlbumHasTracks
+                .AsNoTracking()
+                .Where(albumTrack => albumTrack.AlbumId == album.Id);
+
+            var trackCount = await albumTracks.CountAsync(cancellationToken);
+            var coverTrackIds = await albumTracks
+                .OrderBy(albumTrack => albumTrack.TrackNumber)
+                .Take(AlbumApplicationResponse.CoverTrackCount)
+                .Select(albumTrack => albumTrack.TrackId)
+                .ToListAsync(cancellationToken);
 
             logger.LogInformation("Updated album {AlbumId}", album.Id);
+            return AlbumApplicationResponse.FromEntity(album, trackCount, coverTrackIds);
+        }
 
-            return await database.Albums
-                .AsNoTracking()
-                .Where(a => a.Id == album.Id)
-                .SelectResponse()
-                .SingleAsync(cancellationToken);
+        private async Task<ErrorOr<Success>> PublishUpdateAlbumPictureSourceEventAsync(
+            Guid albumId,
+            UploadIntent pictureIntent,
+            string finalPictureKey,
+            CancellationToken cancellationToken)
+        {
+            try
+            {
+                await eventBus.PublishAsync(
+                    new UpdateAlbumPictureSourceEvent(
+                        albumId,
+                        pictureIntent.Id,
+                        storageConfiguration.Bucket,
+                        pictureIntent.Key,
+                        finalPictureKey,
+                        new ImageSize(
+                            albumConfiguration.Routes.SmallPicturesPath,
+                            albumConfiguration.PicturesSizes.SmallPictureWidth,
+                            albumConfiguration.PicturesSizes.SmallPictureHeight),
+                        new ImageSize(
+                            albumConfiguration.Routes.MediumPicturesPath,
+                            albumConfiguration.PicturesSizes.MediumPictureWidth,
+                            albumConfiguration.PicturesSizes.MediumPictureHeight),
+                        new ImageSize(
+                            albumConfiguration.Routes.LargePicturesPath,
+                            albumConfiguration.PicturesSizes.LargePictureWidth,
+                            albumConfiguration.PicturesSizes.LargePictureHeight)),
+                    cancellationToken);
+                return new Success();
+            }
+            catch (Exception exception)
+            {
+                logger.LogError(exception, "Failed to publish update album picture source event for album {AlbumId}", albumId);
+                return Error.Failure(description: $"Failed to publish update album picture source event for album {albumId}");
+            }
         }
     }
 }

backend/Core/Musify.Application/Application.csproj

@@ -19,6 +19,8 @@
     <PackageReference Include="Microsoft.Extensions.Options.ConfigurationExtensions" />
     <PackageReference Include="Microsoft.Extensions.Options.DataAnnotations" />
     <PackageReference Include="MimeMapping" />
+    <PackageReference Include="X.PagedList" />
+    <PackageReference Include="X.PagedList.EF" />
   </ItemGroup>
 
   <ItemGroup>

backend/Core/Musify.Application/ApplicationDependencyInjection.cs

@@ -3,27 +3,26 @@ using Microsoft.Extensions.DependencyInjection;
 using Musify.Application.Configuration;
 using Musify.Application.Services;
 
-namespace Musify.Application
+namespace Musify.Application;
+
+public static class ApplicationDependencyInjection
 {
-    public static class ApplicationDependencyInjection
-    {
     public static IServiceCollection AddApplication(this IServiceCollection services, IConfiguration configuration)
     {
         services.AddMediator();
         services.AddScoped<UploadIntentValidator>();
-            services.AddScoped<UploadIntentIssuer>();
         services.AddScoped<TrackStreamIssuer>();
+        services.AddScoped<YouTubeTrackProvisioner>();
 
-            services.AddValidatedOptions<ApplicationStorageConfiguration>(configuration);
-            services.AddValidatedOptions<PlayListConfiguration>(configuration);
-            services.AddValidatedOptions<AlbumConfiguration>(configuration);
-            services.AddValidatedOptions<TrackConfiguration>(configuration);
-            services.AddValidatedOptions<MixConfiguration>(configuration);
-            services.AddValidatedOptions<StreamGatewayConfiguration>(configuration);
-            services.AddValidatedOptions<UploadIntentConfiguration>(configuration);
-            services.AddValidatedOptions<PlaybackConfiguration>(configuration);
+        services.AddValidatedOptions<ApplicationStorageConfiguration>(configuration, ApplicationStorageConfiguration.SectionName);
+        services.AddValidatedOptions<PlayListConfiguration>(configuration, PlayListConfiguration.SectionName);
+        services.AddValidatedOptions<AlbumConfiguration>(configuration, AlbumConfiguration.SectionName);
+        services.AddValidatedOptions<TrackConfiguration>(configuration, TrackConfiguration.SectionName);
+        services.AddValidatedOptions<MixConfiguration>(configuration, MixConfiguration.SectionName);
+        services.AddValidatedOptions<StreamGatewayConfiguration>(configuration, StreamGatewayConfiguration.SectionName);
+        services.AddValidatedOptions<UploadIntentConfiguration>(configuration, UploadIntentConfiguration.SectionName);
+        services.AddValidatedOptions<PlaybackConfiguration>(configuration, PlaybackConfiguration.SectionName);
 
         return services;
     }
-    }
 }

backend/Core/Musify.Application/AssemblyInfo.cs

@@ -1,4 +1,4 @@
-using Mediator;
+using Mediator;
 using Microsoft.Extensions.DependencyInjection;
 
 [assembly: MediatorOptions(ServiceLifetime = ServiceLifetime.Scoped)]

backend/Core/Musify.Application/Configuration/AlbumConfiguration.cs

@@ -1,15 +1,79 @@
 using System.ComponentModel.DataAnnotations;
+using Musify.Application.Shared;
 
 namespace Musify.Application.Configuration
 {
-    public class AlbumConfiguration : IConfigurationOptions, IPictureOwnerConfiguration
+    public class AlbumConfiguration
     {
-        public static string SectionName => "Album";
+        public const string SectionName = "Album";
 
         [Required]
-        public PictureRoutes Routes { get; set; } = new() { ParentFolder = "Albums" };
+        public AlbumRoutes Routes { get; set; } = new AlbumRoutes();
 
         [Required]
-        public PictureSizes PicturesSizes { get; set; } = new();
+        public AlbumPicturesSizes PicturesSizes { get; set; } = new AlbumPicturesSizes();
+    }
+
+    public class AlbumRoutes
+    {
+        [Required]
+        public string UploadsFolder { get; set; } = "uploads";
+
+        [Required]
+        public string ParentFolders { get; set; } = "Albums";
+
+        [Required]
+        public string OriginalPicturesFolder { get; set; } = "OriginalPictures";
+
+        [Required]
+        public string SmallPicturesFolder { get; set; } = "SmallPictures";
+
+        [Required]
+        public string MediumPicturesFolder { get; set; } = "MediumPictures";
+
+        [Required]
+        public string LargePicturesFolder { get; set; } = "LargePictures";
+
+        public string SmallPicturesPath => StorageKey.Combine(ParentFolders, SmallPicturesFolder);
+
+        public string MediumPicturesPath => StorageKey.Combine(ParentFolders, MediumPicturesFolder);
+
+        public string LargePicturesPath => StorageKey.Combine(ParentFolders, LargePicturesFolder);
+
+        public string OriginalPicturesPath => StorageKey.Combine(ParentFolders, OriginalPicturesFolder);
+
+        public string BuildOriginalPicturePath(string pictureName) => StorageKey.Combine(ParentFolders, OriginalPicturesFolder, pictureName);
+
+        public string BuildOriginalPicturePath(long userId, string pictureName) => StorageKey.Combine(UploadsFolder, userId.ToString(), ParentFolders, OriginalPicturesFolder, pictureName);
+
+        public string BuildSmallPicturePath(string pictureName) => StorageKey.Combine(ParentFolders, SmallPicturesFolder, pictureName);
+
+        public string BuildMediumPicturePath(string pictureName) => StorageKey.Combine(ParentFolders, MediumPicturesFolder, pictureName);
+
+        public string BuildLargePicturePath(string pictureName) => StorageKey.Combine(ParentFolders, LargePicturesFolder, pictureName);
+
+        public string BuildTempPicturePath(string tempRootPrefix, long userId, string objectName) =>
+            StorageKey.Combine(tempRootPrefix, userId.ToString(), ParentFolders, objectName);
+    }
+
+    public class AlbumPicturesSizes
+    {
+        [Range(1, 1024)]
+        public int SmallPictureWidth { get; set; } = 128;
+
+        [Range(1, 1024)]
+        public int SmallPictureHeight { get; set; } = 128;
+
+        [Range(1, 1024)]
+        public int MediumPictureWidth { get; set; } = 256;
+
+        [Range(1, 1024)]
+        public int MediumPictureHeight { get; set; } = 256;
+
+        [Range(1, 1024)]
+        public int LargePictureWidth { get; set; } = 512;
+
+        [Range(1, 1024)]
+        public int LargePictureHeight { get; set; } = 512;
     }
 }

backend/Core/Musify.Application/Configuration/ApplicationStorageConfiguration.cs

@@ -2,9 +2,9 @@ using System.ComponentModel.DataAnnotations;
 
 namespace Musify.Application.Configuration
 {
-    public class ApplicationStorageConfiguration : IConfigurationOptions
+    public class ApplicationStorageConfiguration
     {
-        public static string SectionName => "ApplicationStorage";
+        public const string SectionName = "ApplicationStorage";
 
         [Required]
         [StringLength(128, MinimumLength = 1)]

backend/Core/Musify.Application/Configuration/ConfigurationDependencyInjection.cs

@@ -2,14 +2,10 @@ using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Options;
 
-namespace Musify.Application.Configuration
-{
-    public static class ConfigurationDependencyInjection
-    {
-        public static IServiceCollection AddValidatedOptions<T>(this IServiceCollection services, IConfiguration configuration)
-            where T : class, IConfigurationOptions =>
-            services.AddValidatedOptions<T>(configuration, T.SectionName);
+namespace Musify.Application.Configuration;
 
+public static class ConfigurationDependencyInjection
+{
     public static IServiceCollection AddValidatedOptions<T>(
         this IServiceCollection services,
         IConfiguration configuration,
@@ -26,5 +22,4 @@ namespace Musify.Application.Configuration
 
         return services;
     }
-    }
 }

backend/Core/Musify.Application/Configuration/GetPlaybackPublicConfig.cs

@@ -3,7 +3,8 @@ using Musify.Application.Configuration.Responses;
 
 namespace Musify.Application.Configuration
 {
-
+    /// <summary>Reads the parts of <see cref="PlaybackConfiguration"/> that are safe to expose to an
+    /// unauthenticated client, so it can decide whether to gate the app behind sign-in at all.</summary>
     public record GetPlaybackPublicConfigQuery : IQuery<PlaybackPublicConfigResponse>;
 
     public class GetPlaybackPublicConfigQueryHandler(PlaybackConfiguration playbackConfiguration)

backend/Core/Musify.Application/Configuration/IConfigurationOptions.cs

@@ -1,7 +0,0 @@
-namespace Musify.Application.Configuration
-{
-    public interface IConfigurationOptions
-    {
-        public static abstract string SectionName { get; }
-    }
-}

backend/Core/Musify.Application/Configuration/MixConfiguration.cs

@@ -2,11 +2,20 @@ using System.ComponentModel.DataAnnotations;
 
 namespace Musify.Application.Configuration
 {
-    public class MixConfiguration : IConfigurationOptions
+    public class MixConfiguration
     {
-        public static string SectionName => "Mix";
+        public const string SectionName = "Mix";
+
+        [Range(1, 20)]
+        public int ArtistMixCount { get; set; } = 3;
 
         [Range(4, 100)]
         public int ItemsPerMix { get; set; } = 12;
+
+        [Range(1, 10)]
+        public int SeedArtistCount { get; set; } = 3;
+
+        [Range(1, 100)]
+        public int YouTubeResultsPerSeed { get; set; } = 12;
     }
 }

backend/Core/Musify.Application/Configuration/Pictures.cs

@@ -1,92 +0,0 @@
-using System.ComponentModel.DataAnnotations;
-using System.Globalization;
-using Musify.Application.Shared;
-
-namespace Musify.Application.Configuration
-{
-    public enum PictureSize
-    {
-        Small,
-        Medium,
-        Large
-    }
-
-    public class PictureRoutes
-    {
-        [Required]
-        public string UploadsFolder { get; set; } = "uploads";
-
-        [Required]
-        public string ParentFolder { get; set; } = string.Empty;
-
-        [Required]
-        public string OriginalPicturesFolder { get; set; } = "OriginalPictures";
-
-        [Required]
-        public string SmallPicturesFolder { get; set; } = "SmallPictures";
-
-        [Required]
-        public string MediumPicturesFolder { get; set; } = "MediumPictures";
-
-        [Required]
-        public string LargePicturesFolder { get; set; } = "LargePictures";
-
-        public string FolderPath(PictureSize size) => StorageKey.Combine(ParentFolder, size switch
-        {
-            PictureSize.Small => SmallPicturesFolder,
-            PictureSize.Medium => MediumPicturesFolder,
-            PictureSize.Large => LargePicturesFolder,
-            _ => throw new ArgumentOutOfRangeException(nameof(size), size, null)
-        });
-
-        public string BuildPicturePath(PictureSize size, string pictureName) => StorageKey.Combine(FolderPath(size), pictureName);
-
-        public string BuildOriginalPicturePath(long userId, string pictureName) =>
-            StorageKey.Combine(UploadsFolder, userId.ToString(CultureInfo.InvariantCulture), ParentFolder, OriginalPicturesFolder, pictureName);
-
-        public string BuildTempPath(string tempRootPrefix, long userId, string objectName) =>
-            StorageKey.Combine(tempRootPrefix, userId.ToString(CultureInfo.InvariantCulture), ParentFolder, objectName);
-    }
-
-    public class PictureSizes
-    {
-        [Range(1, 1024)]
-        public int SmallWidth { get; set; } = 128;
-
-        [Range(1, 1024)]
-        public int SmallHeight { get; set; } = 128;
-
-        [Range(1, 1024)]
-        public int MediumWidth { get; set; } = 256;
-
-        [Range(1, 1024)]
-        public int MediumHeight { get; set; } = 256;
-
-        [Range(1, 1024)]
-        public int LargeWidth { get; set; } = 512;
-
-        [Range(1, 1024)]
-        public int LargeHeight { get; set; } = 512;
-
-        public ImageSizes ToImageSizes(PictureRoutes routes) => new(
-            new ImageSize(routes.FolderPath(PictureSize.Small), SmallWidth, SmallHeight),
-            new ImageSize(routes.FolderPath(PictureSize.Medium), MediumWidth, MediumHeight),
-            new ImageSize(routes.FolderPath(PictureSize.Large), LargeWidth, LargeHeight));
-    }
-
-    public interface IPictureOwnerConfiguration
-    {
-        public PictureRoutes Routes { get; }
-
-        public PictureSizes PicturesSizes { get; }
-    }
-
-    public static class PictureSizeParser
-    {
-        /// <summary>Parses the <c>size</c> query value; anything unknown means <see cref="PictureSize.Medium"/>.</summary>
-        public static PictureSize Parse(string? value) =>
-            Enum.TryParse<PictureSize>(value, ignoreCase: true, out var size) && Enum.IsDefined(size)
-                ? size
-                : PictureSize.Medium;
-    }
-}

backend/Core/Musify.Application/Configuration/PlayListConfiguration.cs

@@ -1,15 +1,101 @@
 using System.ComponentModel.DataAnnotations;
+using Musify.Application.Shared;
 
 namespace Musify.Application.Configuration
 {
-    public class PlayListConfiguration : IConfigurationOptions, IPictureOwnerConfiguration
+    public class PlayListConfiguration
     {
-        public static string SectionName => "PlayList";
+        public const string SectionName = "PlayList";
 
         [Required]
-        public PictureRoutes Routes { get; set; } = new() { ParentFolder = "PlayLists" };
+        public PlayListRoutes Routes { get; set; } = new PlayListRoutes();
 
         [Required]
-        public PictureSizes PicturesSizes { get; set; } = new();
+        public PlayListPicturesSizes PicturesSizes { get; set; } = new PlayListPicturesSizes();
+
+        public bool SeedPresetPictures { get; set; } = true;
+
+        public bool OverwritePresetPictures { get; set; } = false;
+    }
+
+    public class PlayListRoutes
+    {
+        [Required]
+        public string UploadsFolder { get; set; } = "uploads";
+
+        [Required]
+        public string ParentFolders { get; set; } = "PlayLists";
+
+        [Required]
+        public string OriginalPicturesFolder { get; set; } = "OriginalPictures";
+
+        [Required]
+        public string SmallPicturesFolder { get; set; } = "SmallPictures";
+
+        [Required]
+        public string MediumPicturesFolder { get; set; } = "MediumPictures";
+
+        [Required]
+        public string LargePicturesFolder { get; set; } = "LargePictures";
+
+        [Required]
+        public string PresetOriginalPicture { get; set; } = "PresetOriginalPicture.webp";
+
+        [Required]
+        public string PresetSmallPicture { get; set; } = "PresetSmallPicture.webp";
+
+        [Required]
+        public string PresetMediumPicture { get; set; } = "PresetMediumPicture.webp";
+
+        [Required]
+        public string PresetLargePicture { get; set; } = "PresetLargePicture.webp";
+
+        public string SmallPicturesPath => StorageKey.Combine(ParentFolders, SmallPicturesFolder);
+
+        public string MediumPicturesPath => StorageKey.Combine(ParentFolders, MediumPicturesFolder);
+
+        public string LargePicturesPath => StorageKey.Combine(ParentFolders, LargePicturesFolder);
+
+        public string OriginalPicturesPath => StorageKey.Combine(ParentFolders, OriginalPicturesFolder);
+
+        public string PresetSmallPicturePath => StorageKey.Combine(ParentFolders, SmallPicturesFolder, PresetSmallPicture);
+
+        public string PresetMediumPicturePath => StorageKey.Combine(ParentFolders, MediumPicturesFolder, PresetMediumPicture);
+
+        public string PresetLargePicturePath => StorageKey.Combine(ParentFolders, LargePicturesFolder, PresetLargePicture);
+
+        public string BuildOriginalPicturePath(string pictureName) => StorageKey.Combine(ParentFolders, OriginalPicturesFolder, pictureName);
+
+        public string BuildOriginalPicturePath(long userId, string pictureName) => StorageKey.Combine(UploadsFolder, userId.ToString(), ParentFolders, OriginalPicturesFolder, pictureName);
+
+        public string BuildSmallPicturePath(string pictureName) => StorageKey.Combine(ParentFolders, SmallPicturesFolder, pictureName);
+
+        public string BuildMediumPicturePath(string pictureName) => StorageKey.Combine(ParentFolders, MediumPicturesFolder, pictureName);
+
+        public string BuildLargePicturePath(string pictureName) => StorageKey.Combine(ParentFolders, LargePicturesFolder, pictureName);
+
+        public string BuildTempPicturePath(string tempRootPrefix, long userId, string objectName) =>
+            StorageKey.Combine(tempRootPrefix, userId.ToString(), ParentFolders, objectName);
+    }
+
+    public class PlayListPicturesSizes
+    {
+        [Range(1, 1024)]
+        public int SmallPictureWidth { get; set; } = 128;
+
+        [Range(1, 1024)]
+        public int SmallPictureHeight { get; set; } = 128;
+
+        [Range(1, 1024)]
+        public int MediumPictureWidth { get; set; } = 256;
+
+        [Range(1, 1024)]
+        public int MediumPictureHeight { get; set; } = 256;
+
+        [Range(1, 1024)]
+        public int LargePictureWidth { get; set; } = 512;
+
+        [Range(1, 1024)]
+        public int LargePictureHeight { get; set; } = 512;
     }
 }

backend/Core/Musify.Application/Configuration/PlaybackConfiguration.cs

@@ -2,16 +2,28 @@ using System.ComponentModel.DataAnnotations;
 
 namespace Musify.Application.Configuration
 {
-
-    public sealed class PlaybackConfiguration : IConfigurationOptions
+    /// <summary>Controls whether listeners without a session can stream music at all, and if so,
+    /// how much of a track they get to hear before being cut off (a Spotify-style preview).</summary>
+    public sealed class PlaybackConfiguration
     {
-        public static string SectionName => "Playback";
+        public const string SectionName = "Playback";
 
+        /// <summary>When false (the default), every stream endpoint requires a signed-in user, exactly
+        /// like before this setting existed. When true, an anonymous request is issued a stream ticket
+        /// too, capped by <see cref="AnonymousFragmentSeconds"/> if that is greater than zero.</summary>
         public bool AllowAnonymousListening { get; set; }
 
+        /// <summary>How many seconds of a track an anonymous listener may hear, enforced by the
+        /// Streaming Gateway clamping the byte range it will serve for that ticket. Zero (the default)
+        /// means no cap: anonymous listeners hear the full track, same as a signed-in user. Ignored
+        /// when <see cref="AllowAnonymousListening"/> is false.</summary>
         [Range(0, 3600)]
         public int AnonymousFragmentSeconds { get; set; }
 
+        /// <summary>Bytes per second of the transcoded audio, used to turn <see cref="AnonymousFragmentSeconds"/>
+        /// into a byte cap for the stream ticket. Defaults to the app's own transcoder output (128 kbps
+        /// AAC, <c>AudioTranscoder:Ffmpeg:AudioBitrate</c>) — update this alongside that setting if it
+        /// ever changes, since the two aren't wired together.</summary>
         [Range(1, int.MaxValue)]
         public int EstimatedAudioBytesPerSecond { get; set; } = 16_000;
     }

backend/Core/Musify.Application/Configuration/Responses/PlaybackPublicConfigResponse.cs

@@ -1,5 +1,7 @@
 namespace Musify.Application.Configuration.Responses
 {
-
+    /// <param name="AllowAnonymousListening">Whether listeners without a session can stream music at all.</param>
+    /// <param name="AnonymousFragmentSeconds">How many seconds of a track an anonymous listener may hear.
+    /// Zero means no cap. Meaningless when <paramref name="AllowAnonymousListening"/> is false.</param>
     public record PlaybackPublicConfigResponse(bool AllowAnonymousListening, int AnonymousFragmentSeconds);
 }

backend/Core/Musify.Application/Configuration/StreamGatewayConfiguration.cs

@@ -2,9 +2,9 @@ using System.ComponentModel.DataAnnotations;
 
 namespace Musify.Application.Configuration
 {
-    public class StreamGatewayConfiguration : IConfigurationOptions
+    public class StreamGatewayConfiguration
     {
-        public static string SectionName => "StreamGateway";
+        public const string SectionName = "StreamGateway";
 
         [Url]
         [Required]

backend/Core/Musify.Application/Configuration/TrackConfiguration.cs

@@ -1,28 +1,38 @@
 using System.ComponentModel.DataAnnotations;
-using System.Globalization;
 using Musify.Application.Shared;
 
 namespace Musify.Application.Configuration
 {
-    public class TrackConfiguration : IConfigurationOptions, IPictureOwnerConfiguration
+    public class TrackConfiguration
     {
-        public static string SectionName => "Track";
+        public const string SectionName = "Track";
 
         [Required]
-        public TrackRoutes Routes { get; set; } = new();
+        public TrackRoutes Routes { get; set; } = new TrackRoutes();
 
         [Required]
-        public PictureSizes PicturesSizes { get; set; } = new();
-
-        PictureRoutes IPictureOwnerConfiguration.Routes => Routes;
+        public TrackPicturesSizes PicturesSizes { get; set; } = new TrackPicturesSizes();
     }
 
-    public class TrackRoutes : PictureRoutes
+    public class TrackRoutes
     {
-        public TrackRoutes()
-        {
-            ParentFolder = "Tracks";
-        }
+        [Required]
+        public string UploadsFolder { get; set; } = "uploads";
+
+        [Required]
+        public string ParentFolder { get; set; } = "Tracks";
+
+        [Required]
+        public string OriginalPicturesFolder { get; set; } = "OriginalPictures";
+
+        [Required]
+        public string SmallPicturesFolder { get; set; } = "SmallPictures";
+
+        [Required]
+        public string MediumPicturesFolder { get; set; } = "MediumPictures";
+
+        [Required]
+        public string LargePicturesFolder { get; set; } = "LargePictures";
 
         [Required]
         public string PresetOriginalPicture { get; set; } = "PresetOriginalPicture.webp";
@@ -40,7 +50,13 @@ namespace Musify.Application.Configuration
         public string OriginalAudiosFolder { get; set; } = "OriginalAudios";
 
         [Required]
-        public string ProcessedAudiosFolder { get; set; } = "ProcessedAudios";
+        public string ProcessedAudioFolder { get; set; } = "ProcessedAudios";
+
+        public string SmallPicturesPath => StorageKey.Combine(ParentFolder, SmallPicturesFolder);
+
+        public string MediumPicturesPath => StorageKey.Combine(ParentFolder, MediumPicturesFolder);
+
+        public string LargePicturesPath => StorageKey.Combine(ParentFolder, LargePicturesFolder);
 
         public string PresetSmallPicturePath => StorageKey.Combine(ParentFolder, PresetSmallPicture);
 
@@ -48,10 +64,53 @@ namespace Musify.Application.Configuration
 
         public string PresetLargePicturePath => StorageKey.Combine(ParentFolder, PresetLargePicture);
 
-        public string BuildOriginalAudioPath(long userId, string audioName) =>
-            StorageKey.Combine(UploadsFolder, userId.ToString(CultureInfo.InvariantCulture), ParentFolder, OriginalAudiosFolder, audioName);
+        public string OriginalPicturesPath => StorageKey.Combine(ParentFolder, OriginalPicturesFolder);
 
-        public string BuildProcessedAudioPath(string folderName) =>
-            StorageKey.Combine(ParentFolder, ProcessedAudiosFolder, folderName);
+        public string OriginalAudiosPath => StorageKey.Combine(ParentFolder, OriginalAudiosFolder);
+
+        public string ProcessedAudiosPath => StorageKey.Combine(ParentFolder, ProcessedAudioFolder);
+
+        public string BuildOriginalPicturePath(string pictureName) => StorageKey.Combine(OriginalPicturesPath, pictureName);
+
+        public string BuildOriginalPicturePath(long userId, string pictureName) => StorageKey.Combine(UploadsFolder, userId.ToString(), OriginalPicturesPath, pictureName);
+
+        public string BuildSmallPicturePath(string pictureName) => StorageKey.Combine(SmallPicturesPath, pictureName);
+
+        public string BuildMediumPicturePath(string pictureName) => StorageKey.Combine(MediumPicturesPath, pictureName);
+
+        public string BuildLargePicturePath(string pictureName) => StorageKey.Combine(LargePicturesPath, pictureName);
+
+        public string BuildOriginalAudioPath(string audioName) => StorageKey.Combine(OriginalAudiosPath, audioName);
+
+        public string BuildOriginalAudioPath(long userId, string audioName) => StorageKey.Combine(UploadsFolder, userId.ToString(), OriginalAudiosPath, audioName);
+
+        public string BuildProcessedAudioPath(string audioName) => StorageKey.Combine(ProcessedAudiosPath, audioName);
+
+        public string BuildTempPicturePath(string tempRootPrefix, long userId, string objectName) =>
+            StorageKey.Combine(tempRootPrefix, userId.ToString(), ParentFolder, objectName);
+
+        public string BuildTempAudioPath(string tempRootPrefix, long userId, string objectName) =>
+            StorageKey.Combine(tempRootPrefix, userId.ToString(), ParentFolder, objectName);
+    }
+
+    public class TrackPicturesSizes
+    {
+        [Range(1, 1024)]
+        public int SmallPictureWidth { get; set; } = 128;
+
+        [Range(1, 1024)]
+        public int SmallPictureHeight { get; set; } = 128;
+
+        [Range(1, 1024)]
+        public int MediumPictureWidth { get; set; } = 256;
+
+        [Range(1, 1024)]
+        public int MediumPictureHeight { get; set; } = 256;
+
+        [Range(1, 1024)]
+        public int LargePictureWidth { get; set; } = 512;
+
+        [Range(1, 1024)]
+        public int LargePictureHeight { get; set; } = 512;
     }
 }

backend/Core/Musify.Application/Configuration/UploadIntentConfiguration.cs

@@ -2,9 +2,9 @@ using System.ComponentModel.DataAnnotations;
 
 namespace Musify.Application.Configuration
 {
-    public class UploadIntentConfiguration : IConfigurationOptions
+    public class UploadIntentConfiguration
     {
-        public static string SectionName => "UploadIntent";
+        public const string SectionName = "UploadIntent";
 
         [Range(10, 3600)]
         public int UploadUrlExpiresInSeconds { get; set; } = 120;
@@ -31,12 +31,12 @@ namespace Musify.Application.Configuration
         public int ExpiredIntentsRetentionDays { get; set; } = 7;
 
         [Required, MinLength(1)]
-        public string TempRootPrefix { get; set; } = "temp";
+        public string TemporalRootPrefix { get; set; } = "temporal";
 
         [Range(1, 30)]
-        public int TempUploadsRetentionDays { get; set; } = 3;
+        public int TemporalUploadsRetentionDays { get; set; } = 3;
 
         [Range(60, 86400)]
-        public int TempCleanupJobIntervalSeconds { get; set; } = 3600;
+        public int TemporalCleanUpJobIntervalSeconds { get; set; } = 3600;
     }
 }

backend/Core/Musify.Application/Contracts/IAudioTranscoderService.cs

@@ -2,6 +2,8 @@ namespace Musify.Application.Contracts
 {
     public interface IAudioTranscoderService
     {
-        public Task<AudioTranscodeResult> TranscodeToAudioFileAsync(Stream audioStream, string destinationPath, CancellationToken cancellationToken);
+        Task<AudioTranscodeResult> TranscodeToAudioFileAsync(Stream audioStream, string destinationPath, CancellationToken cancellationToken);
+
+        Task<bool> IsValidAudioFileAsync(string filePath, CancellationToken cancellationToken);
     }
 }

backend/Core/Musify.Application/Contracts/IDatabase.cs

@@ -1,4 +1,3 @@
-using ErrorOr;
 using Microsoft.EntityFrameworkCore;
 using Musify.Domain.Entities;
 
@@ -6,38 +5,44 @@ namespace Musify.Application.Contracts
 {
     public interface IDatabase
     {
-        public DbSet<User> Users { get; }
+        DbSet<User> Users { get; }
 
-        public DbSet<PlayList> PlayLists { get; }
+        DbSet<PlayList> PlayLists { get; }
 
-        public DbSet<Album> Albums { get; }
+        DbSet<Album> Albums { get; }
 
-        public DbSet<AlbumHasTrack> AlbumHasTracks { get; }
+        DbSet<UserAlbum> UserAlbums { get; }
 
-        public DbSet<Track> Tracks { get; }
+        DbSet<ExternalAlbum> ExternalAlbums { get; }
 
-        public DbSet<PlayListHasTrack> PlayListHasTracks { get; }
+        DbSet<AlbumHasTrack> AlbumHasTracks { get; }
 
-        public DbSet<Mix> Mixes { get; }
+        DbSet<Track> Tracks { get; }
 
-        public DbSet<MixItem> MixItems { get; }
+        DbSet<LocalTrack> LocalTracks { get; }
 
-        public DbSet<UploadIntent> UploadIntents { get; }
+        DbSet<ExternalTrack> ExternalTracks { get; }
 
-        public DbSet<ListeningHistory> ListeningHistories { get; }
+        DbSet<Artist> Artists { get; }
 
-        public DbSet<TrackLike> TrackLikes { get; }
+        DbSet<TrackArtist> TrackArtists { get; }
 
-        public DbSet<TrackTag> TrackTags { get; }
+        DbSet<UserHasTrack> UserHasTracks { get; }
 
-        public DbSet<UserFollow> UserFollows { get; }
+        DbSet<PlayListHasTrack> PlayListHasTracks { get; }
 
-        public Task<IDatabaseTransaction> BeginTransactionAsync(System.Data.IsolationLevel isolationLevel, CancellationToken cancellationToken);
+        DbSet<Mix> Mixes { get; }
 
-        public DbSet<TEntity> Set<TEntity>() where TEntity : class;
+        DbSet<MixItem> MixItems { get; }
 
-        public Task<int> SaveChangesAsync(CancellationToken cancellationToken);
+        DbSet<Upload> Uploads { get; }
 
-        public Task<ErrorOr<Success>> TrySaveChangesAsync(Error onUniqueViolation, CancellationToken cancellationToken);
+        DbSet<UploadIntent> UploadIntents { get; }
+
+        DbSet<ListeningHistory> ListeningHistories { get; }
+
+        Task<IDatabaseTransaction> BeginTransactionAsync(System.Data.IsolationLevel isolationLevel, CancellationToken cancellationToken);
+
+        Task<int> SaveChangesAsync(CancellationToken cancellationToken);
     }
 }

backend/Core/Musify.Application/Contracts/IDatabaseTransaction.cs

@@ -2,6 +2,6 @@ namespace Musify.Application.Contracts
 {
     public interface IDatabaseTransaction : IAsyncDisposable
     {
-        public Task CommitAsync(CancellationToken cancellationToken = default);
+        Task CommitAsync(CancellationToken cancellationToken = default);
     }
 }

backend/Core/Musify.Application/Contracts/IEventBus.cs

@@ -2,6 +2,6 @@ namespace Musify.Application.Contracts
 {
     public interface IEventBus
     {
-        public Task PublishAsync<T>(T message, CancellationToken cancellationToken) where T : class;
+        Task PublishAsync<T>(T message, CancellationToken cancellationToken) where T : class;
     }
 }

backend/Core/Musify.Application/Contracts/IPictureService.cs

@@ -2,6 +2,6 @@ namespace Musify.Application.Contracts
 {
     public interface IPictureService
     {
-        public Task<Stream> ResizePictureAsWebpAsync(Stream pictureStream, int width, int height, CancellationToken cancellationToken);
+        Task<Stream> ResizePictureAsWebpAsync(Stream pictureStream, int width, int height, CancellationToken cancellationToken);
     }
 }

backend/Core/Musify.Application/Contracts/IStorageService.cs

@@ -2,24 +2,27 @@ namespace Musify.Application.Contracts
 {
     public interface IStorageService
     {
-        /// <summary>Opens an object for reading, or returns null when it does not exist.</summary>
-        public Task<Stream?> GetFileAsync(string bucket, string key, CancellationToken cancellationToken);
+        Task<Stream> GetFileAsync(string bucket, string key, CancellationToken cancellationToken);
 
-        public Task<ObjectMetaData?> HeadObjectAsync(string bucket, string key, CancellationToken cancellationToken);
+        Task<ObjectMetaData?> HeadObjectAsync(string bucket, string key, CancellationToken cancellationToken);
 
-        public Task<string> GetUploadUrlAsync(string bucket, string key, string contentType, TimeSpan expirationTime, bool preventOverwrite = true, CancellationToken cancellationToken = default);
+        Task<string> GetUrlAsync(string bucket, string key, TimeSpan ExpirationTime, CancellationToken cancellationToken);
 
-        public Task UploadFileAsync(string filePath, string bucket, string key, CancellationToken cancellationToken);
+        Task<string> GetUploadUrlAsync(string bucket, string key, string contentType, TimeSpan expirationTime, CancellationToken cancellationToken, bool preventOverwrite = true);
 
-        public Task UploadFileAsync(Stream sourceStream, string contentType, string bucket, string key, CancellationToken cancellationToken);
+        Task UploadFileAsync(string filePath, string bucket, string key, CancellationToken cancellationToken);
 
-        public Task<IReadOnlyList<string>> TransferFilesAsync(string sourceDirectory, string bucket, string route, CancellationToken cancellationToken);
+        Task UploadFileAsync(Stream sourceStream, string contentType, string bucket, string key, CancellationToken cancellationToken);
 
-        public Task RemoveFileAsync(string bucket, string key, CancellationToken cancellationToken);
+        Task<IReadOnlyList<string>> TransferFilesAsync(string sourceDirectory, string bucket, string route, CancellationToken cancellationToken);
 
-        public Task CopyFileAsync(string sourceBucket, string sourceKey, string destinationBucket, string destinationKey,
+        Task RemoveFileAsync(string bucket, string key, CancellationToken cancellationToken);
+
+        Task CopyFileAsync(string sourceBucket, string sourceKey, string destinationBucket, string destinationKey,
             CancellationToken cancellationToken);
 
-        public IAsyncEnumerable<StorageObject> ListObjectsAsync(string bucket, string prefix, CancellationToken cancellationToken);
+        Task RemoveFolderAsync(string bucket, string folderKey, CancellationToken cancellationToken);
+        
+        IAsyncEnumerable<StorageObject> ListObjectsAsync(string bucket, string prefix, CancellationToken cancellationToken);
     }
 }

backend/Core/Musify.Application/Contracts/IStreamTicketService.cs

@@ -2,7 +2,12 @@ namespace Musify.Application.Contracts
 {
     public interface IStreamTicketService
     {
-        public StreamTicket IssueTicket(long? userId, string keyPrefix, long? maxBytes = null);
+        /// <param name="userId">Null for an anonymous listener — the ticket is issued without a
+        /// <c>sub</c> claim.</param>
+        /// <param name="keyPrefix">The storage key (prefix) the ticket authorizes reading from.</param>
+        /// <param name="maxBytes">When set, the Streaming Gateway clamps the byte range it will serve
+        /// for this ticket to <c>[0, maxBytes)</c> — used for the anonymous preview fragment.</param>
+        StreamTicket IssueTicket(long? userId, string keyPrefix, long? maxBytes = null);
     }
 
     public record StreamTicket(string Token, int ExpiresInSeconds);

backend/Core/Musify.Application/Contracts/IYouTubeDownloaderService.cs

@@ -0,0 +1,9 @@
+namespace Musify.Application.Contracts
+{
+    public record YouTubeDownloadResult(int ExitCode, string StandardError);
+
+    public interface IYouTubeDownloaderService
+    {
+        Task<YouTubeDownloadResult> DownloadAudioAsync(string videoId, string destinationFilePath, CancellationToken cancellationToken);
+    }
+}

backend/Core/Musify.Application/Contracts/IYouTubeMusicService.cs

@@ -0,0 +1,64 @@
+using ErrorOr;
+
+namespace Musify.Application.Contracts
+{
+    public record YouTubeArtistRef(string? Id, string Name);
+
+    public record YouTubeSongResult(
+        string VideoId,
+        string Title,
+        string Artist,
+        string Album,
+        int DurationSeconds,
+        string ThumbnailUrl,
+        bool IsExplicit,
+        IReadOnlyList<YouTubeArtistRef> Artists);
+
+    public record YouTubeSearchResult(
+        IReadOnlyList<YouTubeSongResult> Items,
+        string ContinuationToken);
+
+    public record YouTubeAlbumResult(
+        string AlbumId,
+        string Title,
+        string Artist,
+        string ThumbnailUrl,
+        int? ReleaseYear,
+        bool IsSingle,
+        bool IsEp,
+        IReadOnlyList<YouTubeArtistRef> Artists);
+
+    public record YouTubeAlbumSearchResult(
+        IReadOnlyList<YouTubeAlbumResult> Items,
+        string ContinuationToken);
+
+    public record YouTubeAlbumTrack(
+        string VideoId,
+        string Title,
+        int DurationSeconds,
+        int TrackNumber,
+        bool IsExplicit);
+
+    public record YouTubeAlbumDetail(
+        YouTubeAlbumResult Album,
+        string Description,
+        int TotalDurationSeconds,
+        IReadOnlyList<YouTubeAlbumTrack> Tracks);
+
+    public record YouTubeStreamInfo(string Url, int ExpiresInSeconds);
+
+    public interface IYouTubeMusicService
+    {
+        Task<ErrorOr<YouTubeSearchResult>> SearchSongsAsync(string query, string continuationToken, CancellationToken cancellationToken);
+
+        Task<ErrorOr<YouTubeAlbumSearchResult>> SearchAlbumsAsync(string query, string continuationToken, CancellationToken cancellationToken);
+
+        Task<ErrorOr<YouTubeAlbumDetail>> GetAlbumAsync(string albumId, CancellationToken cancellationToken);
+
+        Task<ErrorOr<YouTubeStreamInfo>> GetAudioStreamAsync(string videoId, CancellationToken cancellationToken);
+
+        Task<ErrorOr<YouTubeSongResult>> GetSongAsync(string videoId, CancellationToken cancellationToken);
+
+        string ResolveArtworkUrl(string thumbnailUrl);
+    }
+}

backend/Core/Musify.Application/Events/CreateAlbumResourcesEvent.cs

@@ -8,5 +8,7 @@ namespace Musify.Application.Events
         string Bucket,
         string PictureSourceKey,
         string PictureDestinationKey,
-        ImageSizes Sizes);
+        ImageSize Small,
+        ImageSize Medium,
+        ImageSize Large);
 }

backend/Core/Musify.Application/Events/CreatePlayListResourcesEvent.cs

@@ -8,5 +8,7 @@ namespace Musify.Application.Events
         string Bucket,
         string PictureSourceKey,
         string PictureDestinationKey,
-        ImageSizes Sizes);
+        ImageSize Small,
+        ImageSize Medium,
+        ImageSize Large);
 }

backend/Core/Musify.Application/Events/CreateTrackResourcesEvent.cs

@@ -12,5 +12,7 @@ namespace Musify.Application.Events
         string AudioSourceKey,
         string AudioDestinationKey,
         string AudioProcessedFolderKey,
-        ImageSizes Sizes);
+        ImageSize Small,
+        ImageSize Medium,
+        ImageSize Large);
 }

backend/Core/Musify.Application/Events/DeleteAlbumEvent.cs

@@ -1,6 +0,0 @@
-namespace Musify.Application.Events
-{
-    public record DeleteAlbumEvent(
-        Guid AlbumId,
-        long UserId);
-}

backend/Core/Musify.Application/Events/DownloadYouTubeTrackEvent.cs

@@ -0,0 +1,14 @@
+using Musify.Application.Shared;
+
+namespace Musify.Application.Events
+{
+    public record DownloadYouTubeTrackEvent(
+        Guid TrackId,
+        string VideoId,
+        string ThumbnailUrl,
+        string Bucket,
+        string AudioProcessedFolderKey,
+        ImageSize Small,
+        ImageSize Medium,
+        ImageSize Large);
+}

backend/Core/Musify.Application/Events/UpdateAlbumPictureEvent.cs

@@ -6,5 +6,7 @@ namespace Musify.Application.Events
         Guid AlbumId,
         string Bucket,
         string SourceKey,
-        ImageSizes Sizes);
+        ImageSize Small,
+        ImageSize Medium,
+        ImageSize Large);
 }

backend/Core/Musify.Application/Events/UpdateAlbumPictureSourceEvent.cs

@@ -8,5 +8,7 @@ namespace Musify.Application.Events
         string Bucket,
         string PictureSourceKey,
         string PictureDestinationKey,
-        ImageSizes Sizes);
+        ImageSize Small,
+        ImageSize Medium,
+        ImageSize Large);
 }

backend/Core/Musify.Application/Events/UpdatePlayListPictureEvent.cs

@@ -1,10 +1,12 @@
 using Musify.Application.Shared;
 
-namespace Musify.Application.Events
+namespace Musify.Application.Events
 {
     public record UpdatePlayListPictureEvent(
         Guid PlayListId,
         string Bucket,
         string SourceKey,
-        ImageSizes Sizes);
+        ImageSize Small,
+        ImageSize Medium,
+        ImageSize Large);
 }

backend/Core/Musify.Application/Events/UpdatePlayListPictureSourceEvent.cs

@@ -8,5 +8,7 @@ namespace Musify.Application.Events
         string Bucket,
         string PictureSourceKey,
         string PictureDestinationKey,
-        ImageSizes Sizes);
+        ImageSize Small,
+        ImageSize Medium,
+        ImageSize Large);
 }

backend/Core/Musify.Application/Events/UpdateTrackAudioEvent.cs

@@ -1,4 +1,4 @@
-namespace Musify.Application.Events
+namespace Musify.Application.Events
 {
     public record UpdateTrackAudioEvent(
         Guid TrackId,

backend/Core/Musify.Application/Events/UpdateTrackPictureEvent.cs

@@ -1,10 +1,12 @@
 using Musify.Application.Shared;
 
-namespace Musify.Application.Events
+namespace Musify.Application.Events
 {
     public record UpdateTrackPictureEvent(
         Guid TrackId,
         string Bucket,
         string SourceKey,
-        ImageSizes Sizes);
+        ImageSize Small,
+        ImageSize Medium,
+        ImageSize Large);
 }

backend/Core/Musify.Application/Genres/GetAvailableGenres.cs

@@ -1,25 +0,0 @@
-using Mediator;
-using Musify.Application.Genres.Responses;
-using Musify.Domain.ValueObjects;
-
-namespace Musify.Application.Genres
-{
-    public record GetAvailableGenresQuery : IQuery<IReadOnlyList<AvailableGenreResponse>>;
-
-    public class GetAvailableGenresQueryHandler
-        : IQueryHandler<GetAvailableGenresQuery, IReadOnlyList<AvailableGenreResponse>>
-    {
-        public ValueTask<IReadOnlyList<AvailableGenreResponse>> Handle(GetAvailableGenresQuery request, CancellationToken cancellationToken)
-        {
-            var all = Enum.GetValues<Genre>();
-
-            IReadOnlyList<AvailableGenreResponse> result = all
-                .Select(genre => new AvailableGenreResponse(
-                    genre,
-                    all.Where(other => !GenreCompatibility.AreCompatible(genre, other)).ToList()))
-                .ToList();
-
-            return ValueTask.FromResult(result);
-        }
-    }
-}

backend/Core/Musify.Application/Genres/GetGenres.cs

@@ -1,30 +0,0 @@
-using Mediator;
-using Microsoft.EntityFrameworkCore;
-using Musify.Application.Contracts;
-using Musify.Application.Genres.Responses;
-using Musify.Domain.ValueObjects;
-
-namespace Musify.Application.Genres
-{
-    public record GetGenresQuery : IQuery<IReadOnlyList<GenreResponse>>;
-
-    public class GetGenresQueryHandler(IDatabase database)
-        : IQueryHandler<GetGenresQuery, IReadOnlyList<GenreResponse>>
-    {
-        public async ValueTask<IReadOnlyList<GenreResponse>> Handle(GetGenresQuery request, CancellationToken cancellationToken)
-        {
-            var rows = await database.TrackTags
-                .AsNoTracking()
-                .Where(tag => tag.Track.LifeCycleStatus == LifeCycleStatus.Active)
-                .GroupBy(tag => tag.Tag)
-                .Select(group => new { Genre = group.Key, TrackCount = group.Select(tag => tag.TrackId).Distinct().Count() })
-                .ToListAsync(cancellationToken);
-
-            return rows
-                .OrderByDescending(row => row.TrackCount)
-                .ThenBy(row => row.Genre)
-                .Select(row => new GenreResponse(row.Genre, row.TrackCount))
-                .ToList();
-        }
-    }
-}

backend/Core/Musify.Application/Genres/Responses/AvailableGenreResponse.cs

@@ -1,6 +0,0 @@
-using Musify.Domain.ValueObjects;
-
-namespace Musify.Application.Genres.Responses
-{
-    public record AvailableGenreResponse(Genre Genre, IReadOnlyList<Genre> IncompatibleWith);
-}

backend/Core/Musify.Application/Genres/Responses/GenreResponse.cs

@@ -1,6 +0,0 @@
-using Musify.Domain.ValueObjects;
-
-namespace Musify.Application.Genres.Responses
-{
-    public record GenreResponse(Genre Genre, int TrackCount);
-}

backend/Core/Musify.Application/Likes/GetLikedTracks.cs

@@ -1,31 +0,0 @@
-using Mediator;
-using Microsoft.EntityFrameworkCore;
-using Musify.Application.Contracts;
-using Musify.Application.Shared;
-using Musify.Application.Tracks.Responses;
-using Musify.Domain.ValueObjects;
-
-namespace Musify.Application.Likes
-{
-    public record GetLikedTracksQuery(
-        long UserId,
-        int PageNumber,
-        int PageSize)
-        : IQuery<PaginatedResponse<TrackApplicationResponse>>;
-
-    public class GetLikedTracksQueryHandler(IDatabase database)
-        : IQueryHandler<GetLikedTracksQuery, PaginatedResponse<TrackApplicationResponse>>
-    {
-        public async ValueTask<PaginatedResponse<TrackApplicationResponse>> Handle(GetLikedTracksQuery request, CancellationToken cancellationToken)
-        {
-            return await database.TrackLikes
-                .AsNoTracking()
-                .Where(like => like.UserId == request.UserId && like.Track.LifeCycleStatus == LifeCycleStatus.Active)
-                .OrderByDescending(like => like.CreatedAt)
-                .ThenBy(like => like.Id)
-                .Select(like => like.Track)
-                .SelectResponse()
-                .ToPaginatedAsync(new PageRequest(request.PageNumber, request.PageSize), cancellationToken);
-        }
-    }
-}

backend/Core/Musify.Application/Likes/ToggleTrackLike.cs

@@ -1,59 +0,0 @@
-using ErrorOr;
-using Mediator;
-using Microsoft.EntityFrameworkCore;
-using Microsoft.Extensions.Logging;
-using Musify.Application.Contracts;
-using Musify.Application.Shared;
-using Musify.Domain.Entities;
-using Musify.Domain.ValueObjects;
-
-namespace Musify.Application.Likes
-{
-    public record ToggleTrackLikeCommand(long UserId, Guid TrackId)
-        : ICommand<ErrorOr<bool>>;
-
-    public class ToggleTrackLikeCommandHandler(
-        IDatabase database,
-        ILogger<ToggleTrackLikeCommandHandler> logger)
-        : ICommandHandler<ToggleTrackLikeCommand, ErrorOr<bool>>
-    {
-        public async ValueTask<ErrorOr<bool>> Handle(ToggleTrackLikeCommand request, CancellationToken cancellationToken)
-        {
-            var trackExists = await database.Tracks
-                .AsNoTracking()
-                .AnyAsync(t => t.Id == request.TrackId && t.LifeCycleStatus == LifeCycleStatus.Active, cancellationToken);
-            if (!trackExists)
-                return AppErrors.NotFound("Track", request.TrackId);
-
-            var existingLike = await database.TrackLikes
-                .SingleOrDefaultAsync(like => like.UserId == request.UserId && like.TrackId == request.TrackId, cancellationToken);
-
-            bool nowLiked;
-            if (existingLike != null)
-            {
-                database.TrackLikes.Remove(existingLike);
-                nowLiked = false;
-            }
-            else
-            {
-                await database.TrackLikes.AddAsync(new TrackLike
-                {
-                    UserId = request.UserId,
-                    TrackId = request.TrackId
-                }, cancellationToken);
-                nowLiked = true;
-            }
-
-            // A concurrent double click can hit the unique index; the outcome is already in place, so treat it as a no-op.
-            var saved = await database.TrySaveChangesAsync(
-                AppErrors.Conflict("TrackLike.Duplicate", "Track is already liked."), cancellationToken);
-            if (saved.IsError)
-                return true;
-
-            logger.LogInformation("User {UserId} {Action} track {TrackId}",
-                request.UserId, nowLiked ? "liked" : "unliked", request.TrackId);
-
-            return nowLiked;
-        }
-    }
-}

backend/Core/Musify.Application/Mixes/GenerateMixesForUser.cs

@@ -1,93 +1,287 @@
+using ErrorOr;
 using Mediator;
 using Microsoft.EntityFrameworkCore;
 using Microsoft.Extensions.Logging;
 using Musify.Application.Configuration;
 using Musify.Application.Contracts;
+using Musify.Application.Tracks.Responses;
 using Musify.Domain.Entities;
 using Musify.Domain.ValueObjects;
 
 namespace Musify.Application.Mixes
 {
     public record GenerateMixesForUserCommand(long UserId)
-        : ICommand;
+        : ICommand<ErrorOr<Success>>;
 
     public class GenerateMixesForUserCommandHandler(
         IDatabase database,
+        IYouTubeMusicService youTubeMusicService,
         MixConfiguration mixConfiguration,
         ILogger<GenerateMixesForUserCommandHandler> logger)
-        : ICommandHandler<GenerateMixesForUserCommand>
+        : ICommandHandler<GenerateMixesForUserCommand, ErrorOr<Success>>
     {
-        private sealed record MixDraft(MixKind Kind, IReadOnlyList<Guid> TrackIds);
+        private sealed record SeedArtist(Guid Id, string Name);
 
-        public async ValueTask<Unit> Handle(GenerateMixesForUserCommand request, CancellationToken cancellationToken)
+        private sealed record LocalCandidate(Guid TrackId, string Title, string? Artist, double DurationSeconds);
+
+        private sealed record MixDraft(string Title, string? Subtitle, IReadOnlyList<MixItem> Items);
+
+        private const int TitleLength = 300;
+        private const int ArtistLength = 300;
+        private const int ThumbnailUrlLength = 512;
+        private const int MixTitleLength = 100;
+
+        public async ValueTask<ErrorOr<Success>> Handle(GenerateMixesForUserCommand request, CancellationToken cancellationToken)
         {
             var userId = request.UserId;
 
-            var libraryTrackIds = await database.Tracks
-                .AsNoTracking()
-                .Where(track => track.OwnerUserId == userId && track.LifeCycleStatus == LifeCycleStatus.Active)
-                .Select(track => track.Id)
-                .ToListAsync(cancellationToken);
-
-            if (libraryTrackIds.Count == 0)
-            {
-                logger.LogInformation("User {UserId} has no tracks yet, skipping mix generation", userId);
-                return Unit.Value;
-            }
-
             var historyTrackIds = await database.ListeningHistories
                 .AsNoTracking()
-                .Where(history => history.UserId == userId && history.IsCounted)
+                .Where(history => history.UserId == userId)
                 .Select(history => history.TrackId)
                 .Distinct()
                 .ToListAsync(cancellationToken);
 
-            var historySet = new HashSet<Guid>(historyTrackIds);
-            var unheardTrackIds = libraryTrackIds.Where(id => !historySet.Contains(id)).ToList();
-
-            var drafts = new List<MixDraft>();
-
-            var discovery = Take(Shuffle(unheardTrackIds));
-            if (discovery.Count > 0)
+            if (historyTrackIds.Count == 0)
             {
-                drafts.Add(new MixDraft(MixKind.Discovery, discovery));
+                logger.LogInformation("User {UserId} has no listening history yet, skipping mix generation", userId);
+                return new Success();
             }
 
-            var daily = Take(Interleave(Shuffle(historyTrackIds), Shuffle(unheardTrackIds)));
-            if (daily.Count > 0)
+            var seedArtists = await GetSeedArtistsAsync(historyTrackIds, cancellationToken);
+
+            if (seedArtists.Count == 0)
             {
-                drafts.Add(new MixDraft(MixKind.Daily, daily));
+                logger.LogInformation("User {UserId} has no artists to seed mixes from, skipping mix generation", userId);
+                return new Success();
             }
 
+            var knownVideoIds = await database.ExternalTracks
+                .AsNoTracking()
+                .Where(track => track.Source == TrackSource.YouTube && historyTrackIds.Contains(track.Id))
+                .Select(track => track.ExternalId)
+                .ToListAsync(cancellationToken);
+
+            var excludedVideoIds = new HashSet<string>(knownVideoIds, StringComparer.OrdinalIgnoreCase);
+
+            var youTubeByArtist = await SearchYouTubeAsync(seedArtists, excludedVideoIds, cancellationToken);
+            var localByArtist = await GetLocalCandidatesAsync(seedArtists, historyTrackIds, cancellationToken);
+
+            var drafts = BuildDrafts(seedArtists, localByArtist, youTubeByArtist);
+
             if (drafts.Count == 0)
             {
                 logger.LogInformation("No candidate songs found for user {UserId}, skipping mix generation", userId);
-                return Unit.Value;
+                return new Success();
             }
 
             await ReplaceMixesAsync(userId, drafts, cancellationToken);
 
+            try
+            {
                 await database.SaveChangesAsync(cancellationToken);
-
-            logger.LogInformation("Generated {Count} mixes for user {UserId}", drafts.Count, userId);
-            return Unit.Value;
+            }
+            catch (Exception exception)
+            {
+                logger.LogError(exception, "Failed to generate mixes for user {UserId}", userId);
+                return Error.Failure(description: $"Failed to generate mixes for user {userId}");
             }
 
-        private List<Guid> Take(IEnumerable<Guid> trackIds) =>
-            [.. trackIds.Take(mixConfiguration.ItemsPerMix)];
+            logger.LogInformation("Generated {Count} mixes for user {UserId}", drafts.Count, userId);
+            return new Success();
+        }
 
-        private static List<Guid> Shuffle(IEnumerable<Guid> trackIds) =>
-            [.. trackIds.OrderBy(_ => Guid.NewGuid())];
-
-        private static List<Guid> Interleave(List<Guid> first, List<Guid> second)
+        private async Task<List<SeedArtist>> GetSeedArtistsAsync(
+            IReadOnlyList<Guid> historyTrackIds,
+            CancellationToken cancellationToken)
         {
-            var merged = new List<Guid>(first.Count + second.Count);
+            var ranked = await database.TrackArtists
+                .AsNoTracking()
+                .Where(trackArtist => historyTrackIds.Contains(trackArtist.TrackId))
+                .GroupBy(trackArtist => trackArtist.ArtistId)
+                .Select(group => new { ArtistId = group.Key, Listens = group.Count() } )
+                .OrderByDescending(entry => entry.Listens)
+                .Take(mixConfiguration.SeedArtistCount)
+                .ToListAsync(cancellationToken);
+
+            var artistIds = ranked.Select(entry => entry.ArtistId).ToList();
+
+            var names = await database.Artists
+                .AsNoTracking()
+                .Where(artist => artistIds.Contains(artist.Id))
+                .ToDictionaryAsync(artist => artist.Id, artist => artist.Name, cancellationToken);
+
+            return [.. ranked
+                .Where(entry => names.ContainsKey(entry.ArtistId))
+                .Select(entry => new SeedArtist(entry.ArtistId, names[entry.ArtistId])) ];
+        }
+
+        private async Task<Dictionary<Guid, List<MixItem>> > SearchYouTubeAsync(
+            IReadOnlyList<SeedArtist> seedArtists,
+            HashSet<string> excludedVideoIds,
+            CancellationToken cancellationToken)
+        {
+            var byArtist = new Dictionary<Guid, List<MixItem>>();
+
+            foreach (var seed in seedArtists)
+            {
+                var searchResult = await youTubeMusicService.SearchSongsAsync(seed.Name, string.Empty, cancellationToken);
+                if (searchResult.IsError)
+                {
+                    logger.LogWarning("YouTube Music search failed for seed artist {Artist}: {Error}",
+                        seed.Name, searchResult.FirstError.Description);
+                    byArtist[seed.Id] = [];
+                    continue;
+                }
+
+                var songs = new List<MixItem>();
+                foreach (var song in searchResult.Value.Items.Take(mixConfiguration.YouTubeResultsPerSeed))
+                {
+                    if (!excludedVideoIds.Add(song.VideoId))
+                        continue;
+
+                    songs.Add(new MixItem
+                    {
+                        MixId = Guid.Empty,
+                        Source = MixItemSource.YouTube,
+                        VideoId = song.VideoId,
+                        Title = Truncate(song.Title, TitleLength),
+                        Artist = Truncate(song.Artist, ArtistLength),
+                        ThumbnailUrl = Truncate(youTubeMusicService.ResolveArtworkUrl(song.ThumbnailUrl), ThumbnailUrlLength),
+                        DurationSeconds = song.DurationSeconds,
+                        IsExplicit = song.IsExplicit
+                    } );
+                }
+
+                byArtist[seed.Id] = songs;
+            }
+
+            return byArtist;
+        }
+
+        private async Task<Dictionary<Guid, List<MixItem>> > GetLocalCandidatesAsync(
+            IReadOnlyList<SeedArtist> seedArtists,
+            IReadOnlyList<Guid> historyTrackIds,
+            CancellationToken cancellationToken)
+        {
+            var artistIds = seedArtists.Select(seed => seed.Id).ToList();
+
+            var links = await database.TrackArtists
+                .AsNoTracking()
+                .Where(trackArtist => artistIds.Contains(trackArtist.ArtistId) && !historyTrackIds.Contains(trackArtist.TrackId))
+                .Select(trackArtist => new { trackArtist.ArtistId, trackArtist.TrackId } )
+                .ToListAsync(cancellationToken);
+
+            var trackIds = links.Select(link => link.TrackId).Distinct().ToList();
+
+            var candidates = await LoadCandidatesAsync(trackIds, cancellationToken);
+
+            var byArtist = new Dictionary<Guid, List<MixItem>>();
+            foreach (var seed in seedArtists)
+            {
+                byArtist[seed.Id] = [.. links
+                    .Where(link => link.ArtistId == seed.Id)
+                    .Select(link => candidates.GetValueOrDefault(link.TrackId))
+                    .Where(candidate => candidate is not null)
+                    .Select(candidate => ToMixItem(candidate!))];
+            }
+
+            return byArtist;
+        }
+
+        private async Task<Dictionary<Guid, LocalCandidate>> LoadCandidatesAsync(
+            IReadOnlyList<Guid> trackIds,
+            CancellationToken cancellationToken)
+        {
+            if (trackIds.Count == 0)
+                return [];
+
+            var tracks = await database.Tracks
+                .AsNoTracking()
+                .Where(track => trackIds.Contains(track.Id) && track.LifeCycleStatus == LifeCycleStatus.Active)
+                .Include(track => ((ExternalTrack)track).TrackArtists)
+                    .ThenInclude(trackArtist => trackArtist.Artist)
+                .Include(track => ((LocalTrack)track).Owner)
+                .ToListAsync(cancellationToken);
+
+            return tracks
+                .Select(track => TrackApplicationResponse.FromEntity(track, 0))
+                .ToDictionary(
+                    response => response.Id,
+                    response => new LocalCandidate(response.Id, response.Title, response.Artist, response.Duration));
+        }
+
+        private static MixItem ToMixItem(LocalCandidate candidate) => new()
+        {
+            MixId = Guid.Empty,
+            Source = MixItemSource.Musify,
+            TrackId = candidate.TrackId,
+            Title = candidate.Title,
+            Artist = candidate.Artist,
+            DurationSeconds = candidate.DurationSeconds
+        };
+
+        private List<MixDraft> BuildDrafts(
+            IReadOnlyList<SeedArtist> seedArtists,
+            IReadOnlyDictionary<Guid, List<MixItem>> localByArtist,
+            IReadOnlyDictionary<Guid, List<MixItem>> youTubeByArtist)
+        {
+            var drafts = new List<MixDraft>();
+
+            var everyYouTube = seedArtists.SelectMany(seed => youTubeByArtist[seed.Id]).ToList();
+            var everyLocal = seedArtists.SelectMany(seed => localByArtist[seed.Id]).ToList();
+
+            var discovery = Take(Shuffle(everyYouTube));
+            if (discovery.Count > 0)
+            {
+                drafts.Add(new MixDraft(
+                    "Descubrimiento",
+                    "Canciones nuevas que todavía no has escuchado.",
+                    discovery));
+            }
+
+            var daily = Take(Interleave(Shuffle(everyLocal), Shuffle(everyYouTube)));
+            if (daily.Count > 0)
+            {
+                drafts.Add(new MixDraft(
+                    "Tu mezcla diaria",
+                    "Lo que más escuchas, con alguna sorpresa nueva.",
+                    daily));
+            }
+
+            foreach (var seed in seedArtists.Take(mixConfiguration.ArtistMixCount))
+            {
+                var items = Take(Interleave(Shuffle(localByArtist[seed.Id]), Shuffle(youTubeByArtist[seed.Id])));
+                if (items.Count == 0)
+                    continue;
+
+                drafts.Add(new MixDraft(
+                    Truncate(seed.Name, MixTitleLength),
+                    $"Canciones de {seed.Name} y de artistas parecidos.",
+                    items));
+            }
+
+            return drafts;
+        }
+
+        private List<MixItem> Take(IEnumerable<MixItem> items) =>
+            [.. items.Take(mixConfiguration.ItemsPerMix)];
+
+        private static string Truncate(string value, int maxLength) =>
+            value.Length <= maxLength ? value : value[..maxLength];
+
+        private static List<MixItem> Shuffle(IEnumerable<MixItem> items) =>
+            [.. items.OrderBy(_ => Guid.NewGuid())];
+
+        private static List<MixItem> Interleave(IReadOnlyList<MixItem> first, IReadOnlyList<MixItem> second)
+        {
+            var merged = new List<MixItem>(first.Count + second.Count);
             for (var index = 0; index < Math.Max(first.Count, second.Count); index++)
             {
                 if (index < first.Count)
-                    merged.Add(first[index]);
+                    merged.Add(first[index] );
                 if (index < second.Count)
-                    merged.Add(second[index]);
+                    merged.Add(second[index] );
             }
 
             return merged;
@@ -101,6 +295,12 @@ namespace Musify.Application.Mixes
 
             if (previousMixes.Count > 0)
             {
+                var previousIds = previousMixes.Select(mix => mix.Id).ToList();
+                var previousItems = await database.MixItems
+                    .Where(item => previousIds.Contains(item.MixId))
+                    .ToListAsync(cancellationToken);
+
+                database.MixItems.RemoveRange(previousItems);
                 database.Mixes.RemoveRange(previousMixes);
             }
 
@@ -110,19 +310,28 @@ namespace Musify.Application.Mixes
                 var mix = new Mix
                 {
                     UserId = userId,
-                    Kind = draft.Kind,
+                    Title = draft.Title,
+                    Subtitle = draft.Subtitle,
                     Position = position
                 };
 
                 await database.Mixes.AddAsync(mix, cancellationToken);
 
-                for (var itemPosition = 0; itemPosition < draft.TrackIds.Count; itemPosition++)
+                for (var itemPosition = 0; itemPosition < draft.Items.Count; itemPosition++)
                 {
+                    var item = draft.Items[itemPosition];
                     await database.MixItems.AddAsync(new MixItem
                     {
                         MixId = mix.Id,
                         Position = itemPosition,
-                        TrackId = draft.TrackIds[itemPosition]
+                        Source = item.Source,
+                        TrackId = item.TrackId,
+                        VideoId = item.VideoId,
+                        Title = item.Title,
+                        Artist = item.Artist,
+                        ThumbnailUrl = item.ThumbnailUrl,
+                        DurationSeconds = item.DurationSeconds,
+                        IsExplicit = item.IsExplicit
                     }, cancellationToken);
                 }
             }

backend/Core/Musify.Application/Mixes/GetMixById.cs

@@ -3,7 +3,6 @@ using Mediator;
 using Microsoft.EntityFrameworkCore;
 using Musify.Application.Contracts;
 using Musify.Application.Mixes.Responses;
-using Musify.Application.Shared;
 
 namespace Musify.Application.Mixes
 {
@@ -20,13 +19,12 @@ namespace Musify.Application.Mixes
                 .Include(mix => mix.Items)
                 .SingleOrDefaultAsync(mix => mix.Id == request.MixId && mix.UserId == request.UserId, cancellationToken);
 
-            if (mix == null)
-                return AppErrors.NotFound("Mix", request.MixId);
+            if (mix is null)
+                return Error.NotFound(description: $"Mix {request.MixId} was not found");
 
-            var orderedItems = mix.Items.OrderBy(item => item.Position).ToList();
-            var items = await MixItemMapper.ToResponsesAsync(database, orderedItems, cancellationToken);
+            var items = mix.Items.OrderBy(item => item.Position).ToList();
 
-            return new MixApplicationResponse(mix.Id, mix.Kind, items.Count, items);
+            return MixApplicationResponse.FromEntity(mix, items.Count, items);
         }
     }
 }

backend/Core/Musify.Application/Mixes/GetMixesByUserId.cs

@@ -1,3 +1,4 @@
+using ErrorOr;
 using Mediator;
 using Microsoft.EntityFrameworkCore;
 using Musify.Application.Contracts;
@@ -6,46 +7,31 @@ using Musify.Application.Mixes.Responses;
 namespace Musify.Application.Mixes
 {
     public record GetMixesByUserIdQuery(long UserId)
-        : IQuery<IReadOnlyList<MixApplicationResponse>>;
+        : IQuery<ErrorOr<IReadOnlyList<MixApplicationResponse>>>;
 
     public class GetMixesByUserIdQueryHandler(IDatabase database)
-        : IQueryHandler<GetMixesByUserIdQuery, IReadOnlyList<MixApplicationResponse>>
+        : IQueryHandler<GetMixesByUserIdQuery, ErrorOr<IReadOnlyList<MixApplicationResponse>>>
     {
-        public async ValueTask<IReadOnlyList<MixApplicationResponse>> Handle(GetMixesByUserIdQuery request, CancellationToken cancellationToken)
+        public async ValueTask<ErrorOr<IReadOnlyList<MixApplicationResponse>>> Handle(GetMixesByUserIdQuery request, CancellationToken cancellationToken)
         {
-            var mixes = await database.Mixes
+            var entries = await database.Mixes
                 .AsNoTracking()
                 .Where(mix => mix.UserId == request.UserId)
-                .Include(mix => mix.Items)
                 .OrderBy(mix => mix.Position)
-                .ThenBy(mix => mix.Id)
+                .Select(mix => new
+                {
+                    Mix = mix,
+                    ItemCount = mix.Items.Count,
+                    CoverItems = mix.Items
+                        .OrderBy(item => item.Position)
+                        .Take(MixApplicationResponse.CoverItemCount)
+                        .ToList()
+                })
                 .ToListAsync(cancellationToken);
 
-            var orderedItemsByMix = mixes.ToDictionary(
-                mix => mix.Id,
-                mix => mix.Items.OrderBy(item => item.Position).ToList());
-
-            var coverItems = orderedItemsByMix.Values
-                .SelectMany(items => items.Take(MixApplicationResponse.CoverItemCount))
+            return entries
+                .Select(entry => MixApplicationResponse.FromEntity(entry.Mix, entry.ItemCount, entry.CoverItems))
                 .ToList();
-            var coverResponses = (await MixItemMapper.ToResponsesAsync(database, coverItems, cancellationToken))
-                .GroupBy(response => response.TrackId)
-                .ToDictionary(group => group.Key, group => group.First());
-
-            var responses = new List<MixApplicationResponse>(mixes.Count);
-            foreach (var mix in mixes)
-            {
-                var orderedItems = orderedItemsByMix[mix.Id];
-                var covers = orderedItems
-                    .Take(MixApplicationResponse.CoverItemCount)
-                    .Where(item => coverResponses.ContainsKey(item.TrackId))
-                    .Select(item => coverResponses[item.TrackId])
-                    .ToList();
-
-                responses.Add(new MixApplicationResponse(mix.Id, mix.Kind, orderedItems.Count, covers));
-            }
-
-            return responses;
         }
     }
 }

backend/Core/Musify.Application/Mixes/MixItemMapper.cs

@@ -1,41 +0,0 @@
-using Microsoft.EntityFrameworkCore;
-using Musify.Application.Contracts;
-using Musify.Application.Mixes.Responses;
-using Musify.Domain.Entities;
-using Musify.Domain.ValueObjects;
-
-namespace Musify.Application.Mixes
-{
-
-    internal static class MixItemMapper
-    {
-        public static async Task<List<MixItemApplicationResponse>> ToResponsesAsync(
-            IDatabase database,
-            IReadOnlyList<MixItem> orderedItems,
-            CancellationToken cancellationToken)
-        {
-            var trackIds = orderedItems.Select(item => item.TrackId).Distinct().ToList();
-
-            var tracksById = await database.Tracks
-                .AsNoTracking()
-                .Include(track => track.Owner)
-                .Where(track => trackIds.Contains(track.Id) && track.LifeCycleStatus == LifeCycleStatus.Active)
-                .Select(track => new { Track = track, ListensCount = track.ListeningHistories.Count(l => l.IsCounted) })
-                .ToDictionaryAsync(x => x.Track.Id, cancellationToken);
-
-            return orderedItems
-                .Where(item => tracksById.ContainsKey(item.TrackId))
-                .Select(item =>
-                {
-                    var entry = tracksById[item.TrackId];
-                    return new MixItemApplicationResponse(
-                        item.TrackId,
-                        entry.Track.Title,
-                        entry.Track.Owner.Name,
-                        entry.Track.DurationSeconds,
-                        entry.ListensCount);
-                })
-                .ToList();
-        }
-    }
-}

backend/Core/Musify.Application/Mixes/Responses/MixApplicationResponse.cs

@@ -1,13 +1,25 @@
-using Musify.Domain.ValueObjects;
+using Musify.Domain.Entities;
 
 namespace Musify.Application.Mixes.Responses
 {
     public record MixApplicationResponse(
         Guid Id,
-        MixKind Kind,
+        string Title,
+        string? Subtitle,
         int ItemCount,
         IReadOnlyList<MixItemApplicationResponse> Items)
     {
         public const int CoverItemCount = 4;
+
+        public static MixApplicationResponse FromEntity(
+            Mix mix,
+            int itemCount,
+            IReadOnlyList<MixItem> items) =>
+            new(
+                mix.Id,
+                mix.Title,
+                mix.Subtitle,
+                itemCount,
+                [.. items.Select(MixItemApplicationResponse.FromEntity)]);
     }
 }

backend/Core/Musify.Application/Mixes/Responses/MixItemApplicationResponse.cs

@@ -1,9 +1,27 @@
+using Musify.Domain.Entities;
+using Musify.Domain.ValueObjects;
+
 namespace Musify.Application.Mixes.Responses
 {
     public record MixItemApplicationResponse(
-        Guid TrackId,
+        MixItemSource Source,
+        Guid? TrackId,
+        string? VideoId,
         string Title,
         string? Artist,
+        string? ThumbnailUrl,
         double DurationSeconds,
-        int ListensCount);
+        bool IsExplicit)
+    {
+        public static MixItemApplicationResponse FromEntity(MixItem item) =>
+            new(
+                item.Source,
+                item.TrackId,
+                item.VideoId,
+                item.Title ?? string.Empty,
+                item.Artist,
+                item.ThumbnailUrl,
+                item.DurationSeconds,
+                item.IsExplicit);
+    }
 }

backend/Core/Musify.Application/Pictures/GetCover.cs

@@ -1,76 +0,0 @@
-using ErrorOr;
-using Mediator;
-using Microsoft.EntityFrameworkCore;
-using MimeMapping;
-using Musify.Application.Configuration;
-using Musify.Application.Contracts;
-using Musify.Application.Shared;
-using Musify.Domain.ValueObjects;
-
-namespace Musify.Application.Pictures
-{
-    public enum CoverOwner
-    {
-        Track,
-        Album,
-        PlayList
-    }
-
-    public record GetCoverQuery(CoverOwner Owner, Guid Id, PictureSize Size = PictureSize.Medium)
-        : IQuery<ErrorOr<CoverLocation>>;
-
-    public record CoverLocation(string Bucket, string Key, string ContentType);
-
-    public class GetCoverQueryHandler(
-        IDatabase database,
-        ApplicationStorageConfiguration storageConfiguration,
-        TrackConfiguration trackConfiguration,
-        AlbumConfiguration albumConfiguration,
-        PlayListConfiguration playListConfiguration)
-        : IQueryHandler<GetCoverQuery, ErrorOr<CoverLocation>>
-    {
-        private sealed record CoverSource(long OwnerUserId, string? Original, string? Small, string? Medium, string? Large);
-
-        public async ValueTask<ErrorOr<CoverLocation>> Handle(GetCoverQuery request, CancellationToken cancellationToken)
-        {
-            var (source, routes) = request.Owner switch
-            {
-                CoverOwner.Track => (await database.Tracks.AsNoTracking()
-                    .Where(t => t.Id == request.Id && t.LifeCycleStatus == LifeCycleStatus.Active)
-                    .Select(t => new CoverSource(t.OwnerUserId, t.Pictures.OriginalName, t.Pictures.SmallName, t.Pictures.MediumName, t.Pictures.LargeName))
-                    .SingleOrDefaultAsync(cancellationToken), trackConfiguration.Routes),
-                CoverOwner.Album => (await database.Albums.AsNoTracking()
-                    .Where(a => a.Id == request.Id && a.LifeCycleStatus == LifeCycleStatus.Active && a.Pictures != null)
-                    .Select(a => new CoverSource(a.OwnerUserId, a.Pictures!.OriginalName, a.Pictures.SmallName, a.Pictures.MediumName, a.Pictures.LargeName))
-                    .SingleOrDefaultAsync(cancellationToken), albumConfiguration.Routes),
-                _ => (await database.PlayLists.AsNoTracking()
-                    .Where(p => p.Id == request.Id && p.LifeCycleStatus == LifeCycleStatus.Active && p.Pictures != null)
-                    .Select(p => new CoverSource(p.OwnerUserId, p.Pictures!.OriginalName, p.Pictures.SmallName, p.Pictures.MediumName, p.Pictures.LargeName))
-                    .SingleOrDefaultAsync(cancellationToken), playListConfiguration.Routes)
-            };
-
-            var entity = request.Owner.ToString();
-            if (source == null)
-                return AppErrors.NotFound($"{entity}Cover", request.Id);
-
-            var resizedName = request.Size switch
-            {
-                PictureSize.Small => source.Small,
-                PictureSize.Large => source.Large,
-                _ => source.Medium
-            };
-
-            // The resized files only exist once processing has finished; until then serve the original.
-            var (name, key) = !string.IsNullOrEmpty(resizedName)
-                ? (resizedName, routes.BuildPicturePath(request.Size, resizedName))
-                : !string.IsNullOrEmpty(source.Original)
-                    ? (source.Original, routes.BuildOriginalPicturePath(source.OwnerUserId, source.Original))
-                    : (null, null);
-
-            if (name == null || key == null)
-                return AppErrors.NotFound($"{entity}Cover", request.Id);
-
-            return new CoverLocation(storageConfiguration.Bucket, key, MimeUtility.GetMimeMapping(name));
-        }
-    }
-}

backend/Core/Musify.Application/Pictures/PictureSourceChange.cs

@@ -1,36 +0,0 @@
-using ErrorOr;
-using Musify.Application.Configuration;
-using Musify.Application.Services;
-using Musify.Application.Shared;
-using Musify.Domain.Entities;
-using Musify.Domain.ValueObjects;
-
-namespace Musify.Application.Pictures
-{
-    /// <summary>What an album or playlist needs to switch to a freshly uploaded picture.</summary>
-    public sealed record PreparedPicture(UploadIntent Intent, EntityPictures Pictures, string FinalKey, ImageSizes Sizes);
-
-    public static class PictureSourceChange
-    {
-        public static async Task<ErrorOr<PreparedPicture>> PrepareAsync(
-            UploadIntentValidator uploadIntentValidator,
-            Guid intentId,
-            long userId,
-            UploadIntentPurpose purpose,
-            IPictureOwnerConfiguration owner,
-            CancellationToken cancellationToken)
-        {
-            var validation = await uploadIntentValidator.ValidateAndLoadAsync(intentId, userId, purpose, cancellationToken);
-            if (validation.IsError)
-                return validation.Errors;
-
-            var intent = validation.Value;
-
-            return new PreparedPicture(
-                intent,
-                EntityPictures.Pending(intent.ObjectName),
-                owner.Routes.BuildOriginalPicturePath(userId, intent.ObjectName),
-                owner.PicturesSizes.ToImageSizes(owner.Routes));
-        }
-    }
-}

backend/Core/Musify.Application/PlayLists/AddTrackToPlayList.cs

@@ -0,0 +1,75 @@
+using ErrorOr;
+using Mediator;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.Logging;
+using Musify.Application.Contracts;
+using Musify.Domain.Entities;
+
+namespace Musify.Application.PlayLists
+{
+    public record AddTrackToPlayListCommand(long UserId, Guid PlayListId, Guid TrackId)
+        : ICommand<ErrorOr<Success>>;
+
+    public class AddTrackToPlayListCommandHandler(
+        IDatabase database,
+        ILogger<AddTrackToPlayListCommandHandler> logger)
+        : ICommandHandler<AddTrackToPlayListCommand, ErrorOr<Success>>
+    {
+        public async ValueTask<ErrorOr<Success>> Handle(AddTrackToPlayListCommand request, CancellationToken cancellationToken)
+        {
+            var playList = await database.PlayLists
+                .SingleOrDefaultAsync(pl => pl.Id == request.PlayListId, cancellationToken);
+            if (playList is null)
+            {
+                logger.LogInformation("Playlist {PlayListId} not found", request.PlayListId);
+                return Error.NotFound();
+            }
+
+            if (playList.UserId != request.UserId)
+            {
+                logger.LogWarning("User {UserId} is not the owner of playlist {PlayListId}", request.UserId, request.PlayListId);
+                return Error.Unauthorized();
+            }
+
+            var trackExists = await database.Tracks
+                .AsNoTracking()
+                .AnyAsync(t => t.Id == request.TrackId, cancellationToken);
+            if (!trackExists)
+            {
+                logger.LogInformation("Track {TrackId} not found", request.TrackId);
+                return Error.NotFound(description: $"Track {request.TrackId} not found");
+            }
+
+            var alreadyAdded = await database.PlayListHasTracks
+                .AsNoTracking()
+                .AnyAsync(plt => plt.PlayListId == request.PlayListId && plt.TrackId == request.TrackId, cancellationToken);
+            if (alreadyAdded)
+            {
+                logger.LogInformation("Track {TrackId} already in playlist {PlayListId}", request.TrackId, request.PlayListId);
+                return Error.Conflict(description: "Track is already in the playlist.");
+            }
+
+            var playListTracksQuery = database.PlayListHasTracks
+                .Where(plt => plt.PlayListId == request.PlayListId);
+
+            var hasTracks = await playListTracksQuery.AnyAsync(cancellationToken);
+            var nextPosition = hasTracks
+                ? await playListTracksQuery.MaxAsync(plt => plt.Position, cancellationToken) + 1
+                : 0;
+
+            await database.PlayListHasTracks.AddAsync(new PlayListHasTrack
+            {
+                PlayListId = request.PlayListId,
+                TrackId = request.TrackId,
+                Position = nextPosition
+            }, cancellationToken);
+
+            await database.SaveChangesAsync(cancellationToken);
+
+            logger.LogInformation("Added track {TrackId} to playlist {PlayListId} at position {Position}",
+                request.TrackId, request.PlayListId, nextPosition);
+
+            return new Success();
+        }
+    }
+}

backend/Core/Musify.Application/PlayLists/AddTracksToPlayList.cs

@@ -1,74 +0,0 @@
-using ErrorOr;
-using Mediator;
-using Microsoft.EntityFrameworkCore;
-using Microsoft.Extensions.Logging;
-using Musify.Application.Contracts;
-using Musify.Application.Shared;
-using Musify.Domain.Entities;
-using Musify.Domain.ValueObjects;
-
-namespace Musify.Application.PlayLists
-{
-    /// <summary>Appends tracks to a playlist in the given order, skipping the ones it already has.</summary>
-    public record AddTracksToPlayListCommand(long UserId, Guid PlayListId, IReadOnlyList<Guid> TrackIds)
-        : ICommand<ErrorOr<Success>>;
-
-    public class AddTracksToPlayListCommandHandler(
-        IDatabase database,
-        ILogger<AddTracksToPlayListCommandHandler> logger)
-        : ICommandHandler<AddTracksToPlayListCommand, ErrorOr<Success>>
-    {
-        public async ValueTask<ErrorOr<Success>> Handle(AddTracksToPlayListCommand request, CancellationToken cancellationToken)
-        {
-            var playList = await database.PlayLists.FindOwnedAsync(request.PlayListId, request.UserId, cancellationToken);
-            if (playList.IsError)
-                return playList.Errors;
-
-            var requestedIds = request.TrackIds.Distinct().ToList();
-
-            var existingIds = await database.Tracks
-                .AsNoTracking()
-                .Where(track => requestedIds.Contains(track.Id) && track.LifeCycleStatus == LifeCycleStatus.Active)
-                .Select(track => track.Id)
-                .ToListAsync(cancellationToken);
-
-            var missing = requestedIds.FirstOrDefault(id => !existingIds.Contains(id));
-            if (missing != Guid.Empty)
-                return AppErrors.NotFound("Track", missing);
-
-            var alreadyInPlayList = await database.PlayListHasTracks
-                .AsNoTracking()
-                .Where(link => link.PlayListId == request.PlayListId && requestedIds.Contains(link.TrackId))
-                .Select(link => link.TrackId)
-                .ToListAsync(cancellationToken);
-
-            var toAdd = requestedIds.Where(id => !alreadyInPlayList.Contains(id)).ToList();
-            if (toAdd.Count == 0)
-                return Result.Success;
-
-            // Playlist positions are internal indexes, so they start at 0.
-            var nextPosition = (await database.PlayListHasTracks
-                .Where(link => link.PlayListId == request.PlayListId)
-                .MaxAsync(link => (int?)link.Position, cancellationToken) ?? -1) + 1;
-
-            foreach (var trackId in toAdd)
-            {
-                await database.PlayListHasTracks.AddAsync(new PlayListHasTrack
-                {
-                    PlayListId = request.PlayListId,
-                    TrackId = trackId,
-                    Position = nextPosition++
-                }, cancellationToken);
-            }
-
-            var saved = await database.TrySaveChangesAsync(
-                AppErrors.Conflict("PlayList.ConcurrentChange", "The playlist changed while adding tracks. Try again."), cancellationToken);
-            if (saved.IsError)
-                return saved;
-
-            logger.LogInformation("Added {Count} tracks to playlist {PlayListId}", toAdd.Count, request.PlayListId);
-
-            return Result.Success;
-        }
-    }
-}

backend/Core/Musify.Application/PlayLists/AddYouTubeTrackToPlayList.cs

@@ -0,0 +1,149 @@
+using ErrorOr;
+using Mediator;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.Logging;
+using Musify.Application.Configuration;
+using Musify.Application.Contracts;
+using Musify.Application.Events;
+using Musify.Application.Services;
+using Musify.Application.Shared;
+using Musify.Application.Tracks.Responses;
+using Musify.Domain.Entities;
+using Musify.Domain.ValueObjects;
+
+namespace Musify.Application.PlayLists
+{
+    public record AddYouTubeTrackToPlayListCommand(
+        long UserId,
+        Guid PlayListId,
+        string VideoId)
+        : ICommand<ErrorOr<TrackApplicationResponse>>;
+
+    public class AddYouTubeTrackToPlayListCommandHandler(
+        IDatabase database,
+        IEventBus eventBus,
+        IYouTubeMusicService youTubeMusicService,
+        YouTubeTrackProvisioner provisioner,
+        ApplicationStorageConfiguration storageConfiguration,
+        TrackConfiguration trackConfiguration,
+        ILogger<AddYouTubeTrackToPlayListCommandHandler> logger)
+        : ICommandHandler<AddYouTubeTrackToPlayListCommand, ErrorOr<TrackApplicationResponse>>
+    {
+        public async ValueTask<ErrorOr<TrackApplicationResponse>> Handle(AddYouTubeTrackToPlayListCommand request, CancellationToken cancellationToken)
+        {
+            var playList = await database.PlayLists.AsNoTracking()
+                .SingleOrDefaultAsync(pl => pl.Id == request.PlayListId, cancellationToken);
+            if (playList is null)
+            {
+                logger.LogInformation("Playlist {PlayListId} not found", request.PlayListId);
+                return Error.NotFound();
+            }
+
+            if (playList.UserId != request.UserId)
+            {
+                logger.LogWarning("User {UserId} is not the owner of playlist {PlayListId}", request.UserId, request.PlayListId);
+                return Error.Unauthorized();
+            }
+
+            var provisionResult = await provisioner.GetOrCreateAsync(request.VideoId, cancellationToken);
+            if (provisionResult.IsError)
+                return provisionResult.Errors;
+
+            var track = provisionResult.Value.Track;
+
+            var failed = track.Audio.IsFailed;
+            var neverQueued = !track.Audio.DownloadRequested && !track.Audio.IsProcessed;
+            if (failed || neverQueued)
+            {
+                if (failed)
+                {
+                    track.Audio.TranscodeStatus = ProcessingStatus.Pending;
+                    track.Pictures.ProcessingStatus = ProcessingStatus.Pending;
+                    track.LifeCycleStatus = LifeCycleStatus.Active;
+                    track.Audio.RetryCount += 1;
+                    track.Audio.LastRetryAt = DateTime.UtcNow;
+                }
+                track.Audio.DownloadRequested = true;
+
+                var thumbnailUrl = await ResolveThumbnailUrlAsync(request.VideoId, provisionResult.Value.Song, cancellationToken);
+                if (thumbnailUrl.IsError)
+                    return thumbnailUrl.Errors;
+
+                await PublishDownloadEventAsync(track.Id, request.VideoId, thumbnailUrl.Value, cancellationToken);
+                await database.SaveChangesAsync(cancellationToken);
+                logger.LogInformation("Queued YouTube track {VideoId} for download", request.VideoId);
+            }
+
+            var alreadyAdded = await database.PlayListHasTracks.AsNoTracking()
+                .AnyAsync(plt => plt.PlayListId == request.PlayListId && plt.TrackId == track.Id, cancellationToken);
+            if (alreadyAdded)
+            {
+                logger.LogInformation("Track {TrackId} already in playlist {PlayListId}", track.Id, request.PlayListId);
+                return Error.Conflict(description: "Track is already in the playlist.");
+            }
+
+            var playListTracksQuery = database.PlayListHasTracks
+                .Where(plt => plt.PlayListId == request.PlayListId);
+
+            var hasTracks = await playListTracksQuery.AnyAsync(cancellationToken);
+            var nextPosition = hasTracks
+                ? await playListTracksQuery.MaxAsync(plt => plt.Position, cancellationToken) + 1
+                : 0;
+
+            await database.PlayListHasTracks.AddAsync(new PlayListHasTrack
+            {
+                PlayListId = request.PlayListId,
+                TrackId = track.Id,
+                Position = nextPosition
+            }, cancellationToken);
+
+            await database.SaveChangesAsync(cancellationToken);
+
+            logger.LogInformation("Added YouTube track {VideoId} ({TrackId}) to playlist {PlayListId} at position {Position}",
+                request.VideoId, track.Id, request.PlayListId, nextPosition);
+
+            var listensCount = await database.ListeningHistories.AsNoTracking()
+                .CountAsync(lh => lh.TrackId == track.Id, cancellationToken);
+
+            return TrackApplicationResponse.FromEntity(track, listensCount);
+        }
+
+        private async Task<ErrorOr<string>> ResolveThumbnailUrlAsync(string videoId, YouTubeSongResult? song, CancellationToken cancellationToken)
+        {
+            if (!string.IsNullOrEmpty(song?.ThumbnailUrl))
+                return youTubeMusicService.ResolveArtworkUrl(song.ThumbnailUrl);
+
+            var songResult = await youTubeMusicService.GetSongAsync(videoId, cancellationToken);
+            if (songResult.IsError)
+                return songResult.Errors;
+
+            return youTubeMusicService.ResolveArtworkUrl(songResult.Value.ThumbnailUrl);
+        }
+
+        private async Task PublishDownloadEventAsync(Guid trackId, string videoId, string thumbnailUrl, CancellationToken cancellationToken)
+        {
+            var audioProcessedFolderKey = trackConfiguration.Routes.BuildProcessedAudioPath(Guid.NewGuid().ToString());
+
+            await eventBus.PublishAsync(
+                new DownloadYouTubeTrackEvent(
+                    trackId,
+                    videoId,
+                    thumbnailUrl,
+                    storageConfiguration.Bucket,
+                    audioProcessedFolderKey,
+                    new ImageSize(
+                        trackConfiguration.Routes.SmallPicturesPath,
+                        trackConfiguration.PicturesSizes.SmallPictureWidth,
+                        trackConfiguration.PicturesSizes.SmallPictureHeight),
+                    new ImageSize(
+                        trackConfiguration.Routes.MediumPicturesPath,
+                        trackConfiguration.PicturesSizes.MediumPictureWidth,
+                        trackConfiguration.PicturesSizes.MediumPictureHeight),
+                    new ImageSize(
+                        trackConfiguration.Routes.LargePicturesPath,
+                        trackConfiguration.PicturesSizes.LargePictureWidth,
+                        trackConfiguration.PicturesSizes.LargePictureHeight)),
+                cancellationToken);
+        }
+    }
+}

backend/Core/Musify.Application/PlayLists/CreatePlayList.cs

@@ -3,14 +3,13 @@ using Mediator;
 using Microsoft.EntityFrameworkCore;
 using Microsoft.Extensions.Logging;
 using Musify.Application.Configuration;
-using Musify.Application.Contracts;
+using Musify.Application.Shared;
 using Musify.Application.Events;
-using Musify.Application.Pictures;
 using Musify.Application.PlayLists.Responses;
 using Musify.Application.Services;
-using Musify.Application.Shared;
 using Musify.Domain.Entities;
 using Musify.Domain.ValueObjects;
+using Musify.Application.Contracts;
 
 namespace Musify.Application.PlayLists
 {
@@ -18,8 +17,7 @@ namespace Musify.Application.PlayLists
         long UserId,
         string Name,
         string? Description,
-        Guid? PictureIntentId,
-        PlayListVisibility Visibility = PlayListVisibility.Private)
+        Guid? PictureIntentId)
         : ICommand<ErrorOr<PlayListApplicationResponse>>;
 
     public class CreatePlayListCommandHandler(
@@ -27,53 +25,126 @@ namespace Musify.Application.PlayLists
         IDatabase database,
         UploadIntentValidator uploadIntentValidator,
         ILogger<CreatePlayListCommandHandler> logger,
-        PlayListConfiguration playListConfiguration)
+        ApplicationStorageConfiguration storageConfiguration,
+        PlayListConfiguration playListConfiguration,
+        UploadIntentConfiguration uploadIntentConfiguration)
         : ICommandHandler<CreatePlayListCommand, ErrorOr<PlayListApplicationResponse>>
     {
+        private sealed record ResolvedPlayListPictures(PlayListPictures Pictures, UploadIntent? Intent);
+
         public async ValueTask<ErrorOr<PlayListApplicationResponse>> Handle(CreatePlayListCommand request, CancellationToken cancellationToken)
         {
             var userExists = await database.Users
                 .AsNoTracking()
                 .AnyAsync(u => u.Id == request.UserId, cancellationToken);
             if (!userExists)
-                return AppErrors.NotFound("User", request.UserId);
-
-            PreparedPicture? picture = null;
-            if (request.PictureIntentId is { } intentId)
             {
-                var prepared = await PictureSourceChange.PrepareAsync(
-                    uploadIntentValidator, intentId, request.UserId, UploadIntentPurpose.PlayListPicture, playListConfiguration, cancellationToken);
-                if (prepared.IsError)
-                    return prepared.Errors;
-
-                picture = prepared.Value;
+                logger.LogWarning("User {UserId} not found", request.UserId);
+                return Error.NotFound(description: $"User {request.UserId} not found");
             }
 
-            var name = request.Name.Trim();
+            var picturesResult = await ResolvePicturesAsync(request, cancellationToken);
+            if (picturesResult.IsError)
+                return picturesResult.Errors;
+
+            var resolvedPictures = picturesResult.Value;
+
             var playList = new PlayList
             {
-                OwnerUserId = request.UserId,
-                Name = name,
-                NormalizedName = TextNormalizer.Normalize(name),
-                Description = string.IsNullOrWhiteSpace(request.Description) ? null : request.Description.Trim(),
-                Pictures = picture?.Pictures,
-                Visibility = request.Visibility
+                UserId = request.UserId,
+                Name = request.Name,
+                NormalizedName = request.Name.Trim().ToUpperInvariant(),
+                Description = string.IsNullOrWhiteSpace(request.Description)? null: request.Description.Trim(),
+                Pictures = resolvedPictures.Pictures
             };
             await database.PlayLists.AddAsync(playList, cancellationToken);
 
-            if (picture != null)
+            if (resolvedPictures.Intent != null)
+            {
+                var finalPictureKey = playListConfiguration.Routes.BuildOriginalPicturePath(request.UserId, resolvedPictures.Pictures.OriginalName);
+                var publishResult = await PublishCreatePlayListEventAsync(playList.Id, resolvedPictures.Intent, finalPictureKey, cancellationToken);
+                if (publishResult.IsError)
+                    return publishResult.Errors;
+            }
+
+            try
+            {
+                await database.SaveChangesAsync(cancellationToken);
+            }
+            catch (Exception exception)
+            {
+                logger.LogError(exception, "Failed to save playlist for user {UserId}", request.UserId);
+                return Error.Failure(description: $"Failed to create playlist for user {request.UserId}");
+            }
+
+            logger.LogInformation("Created playlist {PlayListId} for user {UserId}", playList.Id, request.UserId);
+            return PlayListApplicationResponse.FromEntity(playList);
+        }
+
+        private async ValueTask<ErrorOr<ResolvedPlayListPictures>> ResolvePicturesAsync(
+            CreatePlayListCommand request, CancellationToken cancellationToken)
+        {
+            if (!request.PictureIntentId.HasValue)
+            {
+                return new ResolvedPlayListPictures(new PlayListPictures
+                {
+                    OriginalName = playListConfiguration.Routes.PresetOriginalPicture,
+                    SmallName = playListConfiguration.Routes.PresetSmallPicture,
+                    MediumName = playListConfiguration.Routes.PresetMediumPicture,
+                    LargeName = playListConfiguration.Routes.PresetLargePicture
+                }, null);
+            }
+
+            var validation = await uploadIntentValidator.ValidateAndLoadAsync(
+                uploadIntentConfiguration, request.PictureIntentId.Value, request.UserId, cancellationToken);
+
+            if (validation.IsError)
+                return validation.Errors;
+
+            return new ResolvedPlayListPictures(new PlayListPictures 
+            { 
+                OriginalName = validation.Value.ObjectName,
+                SmallName = playListConfiguration.Routes.PresetSmallPicture,
+                MediumName = playListConfiguration.Routes.PresetMediumPicture,
+                LargeName = playListConfiguration.Routes.PresetLargePicture
+            }, validation.Value);
+        }
+
+        async Task<ErrorOr<Success>> PublishCreatePlayListEventAsync(
+            Guid playListId,
+            UploadIntent pictureIntent,
+            string finalPictureKey,
+            CancellationToken cancellationToken)
+        {
+            try
             {
                 await eventBus.PublishAsync(
                     new CreatePlayListResourcesEvent(
-                        playList.Id, picture.Intent.Id, picture.Intent.Bucket, picture.Intent.Key, picture.FinalKey, picture.Sizes),
+                        playListId,
+                        pictureIntent.Id,
+                        storageConfiguration.Bucket,
+                        pictureIntent.Key,
+                        finalPictureKey,
+                        new ImageSize(
+                            playListConfiguration.Routes.SmallPicturesPath,
+                            playListConfiguration.PicturesSizes.SmallPictureWidth,
+                            playListConfiguration.PicturesSizes.SmallPictureHeight),
+                        new ImageSize(
+                            playListConfiguration.Routes.MediumPicturesPath,
+                            playListConfiguration.PicturesSizes.MediumPictureWidth,
+                            playListConfiguration.PicturesSizes.MediumPictureHeight),
+                        new ImageSize(
+                            playListConfiguration.Routes.LargePicturesPath,
+                            playListConfiguration.PicturesSizes.LargePictureWidth,
+                            playListConfiguration.PicturesSizes.LargePictureHeight)),
                     cancellationToken);
+                return new Success();
+            }
+            catch (Exception exception)
+            {
+                logger.LogError(exception, "Failed to publish create playlist event for playlist {PlayListId}", playListId);
+                return Error.Failure(description: $"Failed to publish create playlist event for playlist {playListId}");
             }
-
-            await database.SaveChangesAsync(cancellationToken);
-
-            logger.LogInformation("Created playlist {PlayListId} for user {UserId}", playList.Id, request.UserId);
-
-            return PlayListApplicationResponse.FromEntity(playList);
         }
     }
 }

backend/Core/Musify.Application/PlayLists/DeletePlayList.cs

@@ -1,9 +1,9 @@
 using ErrorOr;
 using Mediator;
+using Microsoft.EntityFrameworkCore;
 using Microsoft.Extensions.Logging;
 using Musify.Application.Contracts;
 using Musify.Application.Events;
-using Musify.Application.Shared;
 using Musify.Domain.ValueObjects;
 
 namespace Musify.Application.PlayLists
@@ -19,19 +19,44 @@ namespace Musify.Application.PlayLists
     {
         public async ValueTask<ErrorOr<Success>> Handle(DeletePlayListCommand request, CancellationToken cancellationToken)
         {
-            var found = await database.PlayLists.FindOwnedAsync(request.PlayListId, request.UserId, cancellationToken);
-            if (found.IsError)
-                return found.Errors;
+            var playList = await database.PlayLists.SingleOrDefaultAsync(p => p.Id == request.PlayListId, cancellationToken);
+            if (playList is null)
+            {
+                logger.LogDebug("Playlist {PlayListId} not found", request.PlayListId);
+                return Error.NotFound();
+            }
+
+            if (playList.UserId != request.UserId)
+            {
+                logger.LogWarning("Playlist {PlayListId} does not belong to user {UserId}", request.PlayListId, request.UserId);
+                return Error.Unauthorized();
+            }
 
-            var playList = found.Value;
             playList.LifeCycleStatus = LifeCycleStatus.Removing;
 
-            await eventBus.PublishAsync(new DeletePlayListEvent(playList.Id, request.UserId), cancellationToken);
+            try
+            {
+                await eventBus.PublishAsync(
+                    new DeletePlayListEvent(playList.Id, request.UserId),
+                    cancellationToken);
+            }
+            catch (Exception exception)
+            {
+                logger.LogError(exception, "Failed to publish delete playlist event for playlist {PlayListId}", request.PlayListId);
+                return Error.Failure(description: $"Failed to delete playlist {request.PlayListId}");
+            }
+
+            try
+            {
                 await database.SaveChangesAsync(cancellationToken);
+            }
+            catch (Exception exception)
+            {
+                logger.LogError(exception, "Failed to mark playlist {PlayListId} as removing", request.PlayListId);
+                return Error.Failure(description: $"Failed to delete playlist {request.PlayListId}");
+            }
 
-            logger.LogInformation("Marked playlist {PlayListId} as removing", request.PlayListId);
-
-            return Result.Success;
+            return new Success();
         }
     }
 }

backend/Core/Musify.Application/PlayLists/GetPlayListById.cs

@@ -1,13 +1,12 @@
 using ErrorOr;
-using Mediator;
 using Microsoft.EntityFrameworkCore;
-using Musify.Application.Contracts;
 using Musify.Application.PlayLists.Responses;
-using Musify.Application.Shared;
+using Mediator;
+using Musify.Application.Contracts;
 
 namespace Musify.Application.PlayLists
 {
-    public record GetPlayListByIdQuery(Guid Id, long? RequestingUserId = null)
+    public record GetPlayListByIdQuery(Guid Id)
         : IQuery<ErrorOr<PlayListApplicationResponse>>;
 
     public class GetPlayListByIdQueryHandler(IDatabase database)
@@ -15,17 +14,24 @@ namespace Musify.Application.PlayLists
     {
         public async ValueTask<ErrorOr<PlayListApplicationResponse>> Handle(GetPlayListByIdQuery request, CancellationToken cancellationToken)
         {
-            var playList = await database.PlayLists
+            var entry = await database.PlayLists
                 .AsNoTracking()
-                .Active()
-                .VisibleTo(request.RequestingUserId)
                 .Where(p => p.Id == request.Id)
-                .SelectResponse()
+                .Select(p => new
+                {
+                    PlayList = p,
+                    CoverTrackIds = p.PlayListTracks
+                        .OrderBy(plt => plt.Position)
+                        .Take(PlayListApplicationResponse.CoverTrackCount)
+                        .Select(plt => plt.TrackId)
+                        .ToList()
+                })
                 .SingleOrDefaultAsync(cancellationToken);
 
-            return playList == null
-                ? AppErrors.NotFound("PlayList", request.Id)
-                : playList;
+            if (entry is null)
+                return Error.NotFound();
+
+            return PlayListApplicationResponse.FromEntity(entry.PlayList, entry.CoverTrackIds);
         }
     }
 }

backend/Core/Musify.Application/PlayLists/GetPlayListCover.cs

@@ -0,0 +1,49 @@
+using ErrorOr;
+using Mediator;
+using Microsoft.EntityFrameworkCore;
+using MimeMapping;
+using Musify.Application.Configuration;
+using Musify.Application.Contracts;
+
+namespace Musify.Application.PlayLists
+{
+    public record GetPlayListCoverQuery(Guid PlayListId, string Size)
+        : IQuery<ErrorOr<PlayListCoverLocation>>;
+
+    public record PlayListCoverLocation(string Bucket, string Key, string ContentType);
+
+    public class GetPlayListCoverQueryHandler(
+        IDatabase database,
+        ApplicationStorageConfiguration storageConfiguration,
+        PlayListConfiguration playListConfiguration)
+        : IQueryHandler<GetPlayListCoverQuery, ErrorOr<PlayListCoverLocation>>
+    {
+        public async ValueTask<ErrorOr<PlayListCoverLocation>> Handle(GetPlayListCoverQuery request, CancellationToken cancellationToken)
+        {
+            var pictures = await database.PlayLists.AsNoTracking()
+                .Where(p => p.Id == request.PlayListId)
+                .Select(p => p.Pictures)
+                .SingleOrDefaultAsync(cancellationToken);
+
+            if (pictures is null)
+                return Error.NotFound();
+
+            var routes = playListConfiguration.Routes;
+            var (name, key) = request.Size.ToLowerInvariant() switch
+            {
+                "small" => (pictures.SmallName, BuildKey(routes.BuildSmallPicturePath, pictures.SmallName)),
+                "large" => (pictures.LargeName, BuildKey(routes.BuildLargePicturePath, pictures.LargeName)),
+                _ => (pictures.MediumName, BuildKey(routes.BuildMediumPicturePath, pictures.MediumName))
+            };
+
+            if (string.IsNullOrEmpty(name) || string.IsNullOrEmpty(key))
+                return Error.NotFound();
+
+            var contentType = MimeUtility.GetMimeMapping(name);
+            return new PlayListCoverLocation(storageConfiguration.Bucket, key, contentType);
+        }
+
+        private static string? BuildKey(Func<string, string> builder, string? name)
+            => string.IsNullOrEmpty(name) ? null : builder(name);
+    }
+}

backend/Core/Musify.Application/PlayLists/GetPlayListTracks.cs

@@ -2,41 +2,50 @@ using ErrorOr;
 using Mediator;
 using Microsoft.EntityFrameworkCore;
 using Musify.Application.Contracts;
-using Musify.Application.PlayLists.Responses;
 using Musify.Application.Shared;
 using Musify.Application.Tracks.Responses;
-using Musify.Domain.ValueObjects;
+using Musify.Domain.Entities;
+using X.PagedList;
+using X.PagedList.EF;
 
 namespace Musify.Application.PlayLists
 {
     public record GetPlayListTracksQuery(
         Guid PlayListId,
         int PageNumber,
-        int PageSize,
-        long? ViewerId = null)
+        int PageSize)
         : IQuery<ErrorOr<PaginatedResponse<TrackApplicationResponse>>>;
 
     public class GetPlayListTracksQueryHandler(IDatabase database)
-        : IQueryHandler<GetPlayListTracksQuery, ErrorOr<PaginatedResponse<TrackApplicationResponse>>>
+        : IQueryHandler<GetPlayListTracksQuery, ErrorOr<PaginatedResponse<TrackApplicationResponse>> >
     {
-        public async ValueTask<ErrorOr<PaginatedResponse<TrackApplicationResponse>>> Handle(GetPlayListTracksQuery request, CancellationToken cancellationToken)
+        public async ValueTask<ErrorOr<PaginatedResponse<TrackApplicationResponse> >> Handle(GetPlayListTracksQuery request, CancellationToken cancellationToken)
         {
-            var playListVisible = await database.PlayLists
+            var playListExists = await database.PlayLists
                 .AsNoTracking()
-                .Active()
-                .VisibleTo(request.ViewerId)
-                .AnyAsync(playList => playList.Id == request.PlayListId, cancellationToken);
-            if (!playListVisible)
-                return AppErrors.NotFound("PlayList", request.PlayListId);
+                .AnyAsync(p => p.Id == request.PlayListId, cancellationToken);
+            if (!playListExists)
+                return Error.NotFound();
 
-            return await database.PlayListHasTracks
+            var tracksQuery = database.PlayListHasTracks
                 .AsNoTracking()
-                .Where(playListTrack => playListTrack.PlayListId == request.PlayListId && playListTrack.Track.LifeCycleStatus == LifeCycleStatus.Active)
-                .OrderBy(playListTrack => playListTrack.Position)
-                .ThenBy(playListTrack => playListTrack.Id)
-                .Select(playListTrack => playListTrack.Track)
-                .SelectResponse()
-                .ToPaginatedAsync(new PageRequest(request.PageNumber, request.PageSize), cancellationToken);
+                .Include(plt => ((ExternalTrack)plt.Track).TrackArtists)
+                    .ThenInclude(trackArtist => trackArtist.Artist)
+                .Include(plt => ((LocalTrack)plt.Track).Owner)
+                .Where(plt => plt.PlayListId == request.PlayListId);
+
+            var totalCount = await tracksQuery.CountAsync(cancellationToken);
+
+            var pagedEntities = await tracksQuery
+                .OrderBy(plt => plt.Position)
+                .Select(plt => new { plt.Track, ListensCount = plt.Track.ListeningHistories.Count })
+                .ToPagedListAsync(request.PageNumber, request.PageSize, totalCount, cancellationToken);
+
+            var pagedTracks = new StaticPagedList<TrackApplicationResponse>(
+                pagedEntities.Select(x => TrackApplicationResponse.FromEntity(x.Track, x.ListensCount)),
+                pagedEntities.PageNumber, pagedEntities.PageSize, pagedEntities.TotalItemCount);
+
+            return PaginatedResponse<TrackApplicationResponse>.FromPagedList(pagedTracks);
         }
     }
 }

backend/Core/Musify.Application/PlayLists/GetPlayLists.cs

@@ -0,0 +1,43 @@
+using ErrorOr;
+using Microsoft.EntityFrameworkCore;
+using Musify.Application.Shared;
+using Musify.Application.PlayLists.Responses;
+using X.PagedList;
+using X.PagedList.EF;
+using Mediator;
+using Musify.Application.Contracts;
+
+namespace Musify.Application.PlayLists
+{
+    public record GetPlayListsQuery(int PageNumber, int PageSize)
+        : IQuery<ErrorOr<PaginatedResponse<PlayListApplicationResponse>> >;
+
+    public class GetPlayListsQueryHandler(IDatabase database)
+        : IQueryHandler<GetPlayListsQuery, ErrorOr<PaginatedResponse<PlayListApplicationResponse> >>
+    {
+        public async ValueTask<ErrorOr<PaginatedResponse<PlayListApplicationResponse> >> Handle(GetPlayListsQuery request, CancellationToken cancellationToken)
+        {
+            var totalCount = await database.PlayLists.CountAsync(cancellationToken);
+
+            var pagedEntities = await database.PlayLists
+                .AsNoTracking()
+                .OrderBy(p => p.Id)
+                .Select(p => new
+                {
+                    PlayList = p,
+                    CoverTrackIds = p.PlayListTracks
+                        .OrderBy(plt => plt.Position)
+                        .Take(PlayListApplicationResponse.CoverTrackCount)
+                        .Select(plt => plt.TrackId)
+                        .ToList()
+                })
+                .ToPagedListAsync(request.PageNumber, request.PageSize, totalCount, cancellationToken);
+
+            var pagedPlayLists = new StaticPagedList<PlayListApplicationResponse>(
+                pagedEntities.Select(entry => PlayListApplicationResponse.FromEntity(entry.PlayList, entry.CoverTrackIds)),
+                pagedEntities.PageNumber, pagedEntities.PageSize, pagedEntities.TotalItemCount);
+
+            return PaginatedResponse<PlayListApplicationResponse>.FromPagedList(pagedPlayLists);
+        }
+    }
+}

backend/Core/Musify.Application/PlayLists/GetPlayListsByUserId.cs

@@ -1,8 +1,12 @@
+using ErrorOr;
 using Mediator;
 using Microsoft.EntityFrameworkCore;
 using Musify.Application.Contracts;
 using Musify.Application.PlayLists.Responses;
 using Musify.Application.Shared;
+using Musify.Domain.ValueObjects;
+using X.PagedList;
+using X.PagedList.EF;
 
 namespace Musify.Application.PlayLists
 {
@@ -10,32 +14,45 @@ namespace Musify.Application.PlayLists
         long UserId,
         string? Name,
         int PageNumber,
-        int PageSize,
-        long? ViewerId = null)
-        : IQuery<PaginatedResponse<PlayListApplicationResponse>>;
+        int PageSize)
+        : IQuery<ErrorOr<PaginatedResponse<PlayListApplicationResponse>> >;
 
     public class GetPlayListsByUserIdQueryHandler(IDatabase database)
-        : IQueryHandler<GetPlayListsByUserIdQuery, PaginatedResponse<PlayListApplicationResponse>>
+        : IQueryHandler<GetPlayListsByUserIdQuery, ErrorOr<PaginatedResponse<PlayListApplicationResponse> > >
     {
-        public async ValueTask<PaginatedResponse<PlayListApplicationResponse>> Handle(GetPlayListsByUserIdQuery request, CancellationToken cancellationToken)
+        public async ValueTask<ErrorOr<PaginatedResponse<PlayListApplicationResponse> >> Handle(GetPlayListsByUserIdQuery request, CancellationToken cancellationToken)
         {
             var playListsQuery = database.PlayLists
                 .AsNoTracking()
-                .Active()
-                .VisibleTo(request.ViewerId)
-                .Where(playList => playList.OwnerUserId == request.UserId);
+                .Where(p => p.UserId == request.UserId);
 
-            if (!string.IsNullOrWhiteSpace(request.Name))
+            if (!string.IsNullOrEmpty(request.Name))
             {
-                var normalizedName = TextNormalizer.Normalize(request.Name);
-                playListsQuery = playListsQuery.Where(playList => playList.NormalizedName.Contains(normalizedName));
+                var normalizedName = request.Name.Trim().ToUpperInvariant();
+                playListsQuery = playListsQuery.Where(p => p.NormalizedName.Contains(normalizedName));
             }
 
-            return await playListsQuery
-                .OrderBy(playList => playList.CreatedAt)
-                .ThenBy(playList => playList.Id)
-                .SelectResponse()
-                .ToPaginatedAsync(new PageRequest(request.PageNumber, request.PageSize), cancellationToken);
+            var totalCount = await playListsQuery.CountAsync(cancellationToken);
+
+            var pagedEntities = await playListsQuery
+                .OrderBy(p => p.CreatedAt)
+                .Where(p => p.LifeCycleStatus == LifeCycleStatus.Active)
+                .Select(p => new
+                {
+                    PlayList = p,
+                    CoverTrackIds = p.PlayListTracks
+                        .OrderBy(plt => plt.Position)
+                        .Take(PlayListApplicationResponse.CoverTrackCount)
+                        .Select(plt => plt.TrackId)
+                        .ToList()
+                } )
+                .ToPagedListAsync(request.PageNumber, request.PageSize, totalCount, cancellationToken);
+
+            var pagedPlayLists = new StaticPagedList<PlayListApplicationResponse>(
+                pagedEntities.Select(entry => PlayListApplicationResponse.FromEntity(entry.PlayList, entry.CoverTrackIds)),
+                pagedEntities.PageNumber, pagedEntities.PageSize, pagedEntities.TotalItemCount);
+
+            return PaginatedResponse<PlayListApplicationResponse>.FromPagedList(pagedPlayLists);
         }
     }
 }

backend/Core/Musify.Application/PlayLists/RemoveTrackFromPlayList.cs

@@ -3,7 +3,6 @@ using Mediator;
 using Microsoft.EntityFrameworkCore;
 using Microsoft.Extensions.Logging;
 using Musify.Application.Contracts;
-using Musify.Application.Shared;
 
 namespace Musify.Application.PlayLists
 {
@@ -17,30 +16,34 @@ namespace Musify.Application.PlayLists
     {
         public async ValueTask<ErrorOr<Success>> Handle(RemoveTrackFromPlayListCommand request, CancellationToken cancellationToken)
         {
-            var playList = await database.PlayLists.FindOwnedAsync(request.PlayListId, request.UserId, cancellationToken);
-            if (playList.IsError)
-                return playList.Errors;
+            var playList = await database.PlayLists
+                .SingleOrDefaultAsync(pl => pl.Id == request.PlayListId, cancellationToken);
+            if (playList is null)
+            {
+                logger.LogInformation("Playlist {PlayListId} not found", request.PlayListId);
+                return Error.NotFound();
+            }
 
-            var playListTracks = await database.PlayListHasTracks
-                .Where(plt => plt.PlayListId == request.PlayListId)
-                .OrderBy(plt => plt.Position)
-                .ToListAsync(cancellationToken);
+            if (playList.UserId != request.UserId)
+            {
+                logger.LogWarning("User {UserId} is not the owner of playlist {PlayListId}", request.UserId, request.PlayListId);
+                return Error.Unauthorized();
+            }
 
-            var link = playListTracks.SingleOrDefault(plt => plt.TrackId == request.TrackId);
-            if (link == null)
-                return Error.NotFound("PlayList.TrackNotFound", "Track is not in the playlist.");
+            var link = await database.PlayListHasTracks
+                .SingleOrDefaultAsync(plt => plt.PlayListId == request.PlayListId && plt.TrackId == request.TrackId, cancellationToken);
+            if (link is null)
+            {
+                logger.LogInformation("Track {TrackId} not in playlist {PlayListId}", request.TrackId, request.PlayListId);
+                return Error.NotFound(description: "Track is not in the playlist.");
+            }
 
             database.PlayListHasTracks.Remove(link);
-
-            var position = 0;
-            foreach (var remaining in playListTracks.Where(plt => plt.Id != link.Id))
-                remaining.Position = position++;
-
             await database.SaveChangesAsync(cancellationToken);
 
             logger.LogInformation("Removed track {TrackId} from playlist {PlayListId}", request.TrackId, request.PlayListId);
 
-            return Result.Success;
+            return new Success();
         }
     }
 }

backend/Core/Musify.Application/PlayLists/RequestPlayListPictureUpload.cs

@@ -1,9 +1,13 @@
 using ErrorOr;
 using Mediator;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.Logging;
 using Musify.Application.Configuration;
-using Musify.Application.Pictures.Responses;
+using Musify.Application.PlayLists.Responses;
 using Musify.Application.Services;
+using Musify.Domain.Entities;
 using Musify.Domain.ValueObjects;
+using Musify.Application.Contracts;
 
 namespace Musify.Application.PlayLists
 {
@@ -12,14 +16,90 @@ namespace Musify.Application.PlayLists
         string FileType,
         string ContentType,
         long? ExpectedSizeBytes = null)
-        : ICommand<ErrorOr<PictureUploadResponse>>;
+        : ICommand<ErrorOr<PlayListPictureUploadResponse>>;
 
-    public class RequestPlayListPictureUploadCommandHandler(UploadIntentIssuer issuer, PlayListConfiguration playListConfiguration)
-        : ICommandHandler<RequestPlayListPictureUploadCommand, ErrorOr<PictureUploadResponse>>
+    public class RequestPlayListPictureUploadCommandHandler(
+        IDatabase database,
+        UploadIntentValidator uploadIntentValidator,
+        IStorageService storageService,
+        ILogger<RequestPlayListPictureUploadCommandHandler> logger,
+        ApplicationStorageConfiguration storageConfiguration,
+        PlayListConfiguration playListConfiguration,
+        UploadIntentConfiguration uploadIntentConfiguration)
+        : ICommandHandler<RequestPlayListPictureUploadCommand, ErrorOr<PlayListPictureUploadResponse>>
     {
-        public async ValueTask<ErrorOr<PictureUploadResponse>> Handle(RequestPlayListPictureUploadCommand request, CancellationToken cancellationToken) =>
-            await issuer.IssuePictureAsync(
-                request.UserId, UploadIntentPurpose.PlayListPicture, playListConfiguration,
-                request.FileType, request.ContentType, request.ExpectedSizeBytes, cancellationToken);
+        public async ValueTask<ErrorOr<PlayListPictureUploadResponse>> Handle(RequestPlayListPictureUploadCommand request, CancellationToken cancellationToken)
+        {
+            var userExists = await database.Users
+                .AsNoTracking()
+                .AnyAsync(u => u.Id == request.UserId, cancellationToken);
+            if (!userExists)
+            {
+                logger.LogWarning("User {UserId} not found", request.UserId);
+                return Error.NotFound(description: $"User {request.UserId} not found");
+            }
+
+            var effectiveSizeBytes = request.ExpectedSizeBytes
+                ?? uploadIntentConfiguration.DefaultExpectedPictureSizeBytes;
+
+            var objectName = $"{Guid.NewGuid() }.{request.FileType.TrimStart('.').ToLowerInvariant() }";
+
+            var tempKey = playListConfiguration.Routes.BuildTempPicturePath(
+                uploadIntentConfiguration.TemporalRootPrefix, request.UserId, objectName);
+
+            try
+            {
+                var uploadUrl = await storageService.GetUploadUrlAsync(
+                    storageConfiguration.Bucket,
+                    tempKey,
+                    request.ContentType,
+                    TimeSpan.FromSeconds(uploadIntentConfiguration.UploadUrlExpiresInSeconds),
+                    cancellationToken);
+
+                await using var transaction = await database.BeginTransactionAsync(
+                    System.Data.IsolationLevel.Serializable, cancellationToken);
+
+                var quotaCheck = await uploadIntentValidator.CheckQuotaAsync(
+                    uploadIntentConfiguration,
+                    request.UserId, effectiveSizeBytes, 1, cancellationToken);
+                if (quotaCheck.IsError)
+                {
+                    logger.LogWarning("User {UserId} failed upload intent quota check", request.UserId);
+                    return quotaCheck.Errors;
+                }
+
+                var intent = new UploadIntent
+                {
+                    UserId = request.UserId,
+                    Bucket = storageConfiguration.Bucket,
+                    Key = tempKey,
+                    ObjectName = objectName,
+                    ContentType = request.ContentType,
+                    ExpectedSizeBytes = effectiveSizeBytes,
+                    Purpose = UploadIntentPurpose.PlayListPicture,
+                    ExpiresAt = DateTime.UtcNow.AddSeconds(uploadIntentConfiguration.UploadUrlExpiresInSeconds),
+                };
+
+                await database.UploadIntents.AddAsync(intent, cancellationToken);
+                await database.SaveChangesAsync(cancellationToken);
+                await transaction.CommitAsync(cancellationToken);
+
+                logger.LogInformation("Issued upload intent {IntentId} for user {UserId} (PlayListPicture, temp key: {Key} )", intent.Id, request.UserId, tempKey);
+
+                return new PlayListPictureUploadResponse(
+                    intent.Id,
+                    storageConfiguration.Bucket,
+                    tempKey,
+                    objectName,
+                    request.ContentType,
+                    uploadIntentConfiguration.UploadUrlExpiresInSeconds,
+                    uploadUrl);
+            }
+            catch (Exception exception)
+            {
+                logger.LogError(exception, "Failed to generate playlist picture upload URL for user {UserId}", request.UserId);
+                return Error.Failure(description: "Failed to generate upload URL");
+            }
+        }
     }
 }

backend/Core/Musify.Application/PlayLists/Responses/PlayListApplicationResponse.cs

@@ -1,6 +1,4 @@
 using Musify.Domain.Entities;
-using Musify.Domain.ValueObjects;
-
 
 namespace Musify.Application.PlayLists.Responses
 {
@@ -11,21 +9,15 @@ namespace Musify.Application.PlayLists.Responses
         string? SmallImageKeyName,
         string? MediumImageKeyName,
         string? LargeImageKeyName,
-        PlayListVisibility Visibility,
         DateTime CreatedAt,
         DateTime UpdatedAt,
-        IReadOnlyList<Guid> CoverTrackIds,
-        long OwnerUserId,
-        int TrackCount,
-        double DurationSeconds)
+        IReadOnlyList<Guid> CoverTrackIds)
     {
-        public const int CoverTrackCount = PlayListProjections.CoverTrackCount;
+        public const int CoverTrackCount = 4;
 
         public static PlayListApplicationResponse FromEntity(
             PlayList playList,
-            IReadOnlyList<Guid>? coverTrackIds = null,
-            int trackCount = 0,
-            double durationSeconds = 0)
+            IReadOnlyList<Guid>? coverTrackIds = null)
         {
             return new PlayListApplicationResponse(
                 playList.Id,
@@ -34,13 +26,9 @@ namespace Musify.Application.PlayLists.Responses
                 playList.Pictures?.SmallName,
                 playList.Pictures?.MediumName,
                 playList.Pictures?.LargeName,
-                playList.Visibility,
                 playList.CreatedAt,
                 playList.UpdatedAt,
-                coverTrackIds ?? [],
-                playList.OwnerUserId,
-                trackCount,
-                durationSeconds);
+                coverTrackIds ?? []);
         }
     }
 }

backend/Core/Musify.Application/PlayLists/Responses/PlayListPictureUploadResponse.cs

@@ -0,0 +1,11 @@
+namespace Musify.Application.PlayLists.Responses
+{
+    public record PlayListPictureUploadResponse(
+        Guid IntentId,
+        string Bucket,
+        string Key,
+        string PictureName,
+        string ContentType,
+        int ExpiresInSeconds,
+        string UploadUrl);
+}

backend/Core/Musify.Application/PlayLists/Responses/PlayListProjections.cs

@@ -1,38 +0,0 @@
-using Musify.Domain.Entities;
-using Musify.Domain.ValueObjects;
-
-namespace Musify.Application.PlayLists.Responses
-{
-    public static class PlayListProjections
-    {
-        public const int CoverTrackCount = 4;
-
-        public static IQueryable<PlayList> Active(this IQueryable<PlayList> query) =>
-            query.Where(playList => playList.LifeCycleStatus == LifeCycleStatus.Active);
-
-        public static IQueryable<PlayList> VisibleTo(this IQueryable<PlayList> query, long? viewerId) =>
-            query.Where(playList => playList.Visibility == PlayListVisibility.Public || playList.OwnerUserId == viewerId);
-
-        public static IQueryable<PlayListApplicationResponse> SelectResponse(this IQueryable<PlayList> query) =>
-            query.Select(playList => new PlayListApplicationResponse(
-                playList.Id,
-                playList.Name,
-                playList.Description,
-                playList.Pictures!.SmallName,
-                playList.Pictures!.MediumName,
-                playList.Pictures!.LargeName,
-                playList.Visibility,
-                playList.CreatedAt,
-                playList.UpdatedAt,
-                playList.PlayListTracks
-                    .OrderBy(playListTrack => playListTrack.Position)
-                    .Take(CoverTrackCount)
-                    .Select(playListTrack => playListTrack.TrackId)
-                    .ToList(),
-                playList.OwnerUserId,
-                playList.PlayListTracks.Count(playListTrack => playListTrack.Track.LifeCycleStatus == LifeCycleStatus.Active),
-                playList.PlayListTracks
-                    .Where(playListTrack => playListTrack.Track.LifeCycleStatus == LifeCycleStatus.Active)
-                    .Sum(playListTrack => playListTrack.Track.DurationSeconds)));
-    }
-}

backend/Core/Musify.Application/PlayLists/UpdatePlayList.cs

@@ -3,13 +3,13 @@ using Mediator;
 using Microsoft.EntityFrameworkCore;
 using Microsoft.Extensions.Logging;
 using Musify.Application.Configuration;
-using Musify.Application.Contracts;
+using Musify.Application.Shared;
 using Musify.Application.Events;
-using Musify.Application.Pictures;
 using Musify.Application.PlayLists.Responses;
 using Musify.Application.Services;
-using Musify.Application.Shared;
+using Musify.Domain.Entities;
 using Musify.Domain.ValueObjects;
+using Musify.Application.Contracts;
 
 namespace Musify.Application.PlayLists
 {
@@ -18,8 +18,7 @@ namespace Musify.Application.PlayLists
         Guid PlayListId,
         string? NewName,
         string? NewDescription,
-        Guid? NewPictureIntentId,
-        PlayListVisibility? NewVisibility = null)
+        Guid? NewPictureIntentId)
         : ICommand<ErrorOr<PlayListApplicationResponse>>;
 
     public class UpdatePlayListCommandHandler(
@@ -27,55 +26,126 @@ namespace Musify.Application.PlayLists
         IDatabase database,
         UploadIntentValidator uploadIntentValidator,
         ILogger<UpdatePlayListCommandHandler> logger,
-        PlayListConfiguration playListConfiguration)
+        ApplicationStorageConfiguration storageConfiguration,
+        PlayListConfiguration playListConfiguration,
+        UploadIntentConfiguration uploadIntentConfiguration)
         : ICommandHandler<UpdatePlayListCommand, ErrorOr<PlayListApplicationResponse>>
     {
         public async ValueTask<ErrorOr<PlayListApplicationResponse>> Handle(UpdatePlayListCommand request, CancellationToken cancellationToken)
         {
-            var found = await database.PlayLists.FindOwnedAsync(request.PlayListId, request.UserId, cancellationToken);
-            if (found.IsError)
-                return found.Errors;
+            var playListEntity = await database.PlayLists.SingleOrDefaultAsync(pl => pl.Id == request.PlayListId, cancellationToken);
+            if (playListEntity is null)
+            {
+                logger.LogInformation("Playlist {PlayListId} not found", request.PlayListId);
+                return Error.NotFound();
+            }
 
-            var playList = found.Value;
+            if (playListEntity.UserId != request.UserId)
+            {
+                logger.LogWarning("User {UserId} is not the owner of playlist {PlayListId}", request.UserId, request.PlayListId);
+                return Error.Unauthorized();
+            }
 
             if (!string.IsNullOrWhiteSpace(request.NewName))
             {
-                playList.Name = request.NewName.Trim();
-                playList.NormalizedName = TextNormalizer.Normalize(request.NewName);
+                playListEntity.Name = request.NewName;
+                playListEntity.NormalizedName = request.NewName.Trim().ToUpperInvariant();
             }
 
-            // null means "unchanged"; a blank description clears it.
-            if (request.NewDescription != null)
-                playList.Description = string.IsNullOrWhiteSpace(request.NewDescription) ? null : request.NewDescription.Trim();
-
-            if (request.NewVisibility is { } visibility)
-                playList.Visibility = visibility;
-
-            if (request.NewPictureIntentId is { } intentId)
+            if (!string.IsNullOrWhiteSpace(request.NewDescription))
             {
-                var prepared = await PictureSourceChange.PrepareAsync(
-                    uploadIntentValidator, intentId, request.UserId, UploadIntentPurpose.PlayListPicture, playListConfiguration, cancellationToken);
-                if (prepared.IsError)
-                    return prepared.Errors;
+                playListEntity.Description = request.NewDescription;
+            }
 
-                var picture = prepared.Value;
-                playList.Pictures = picture.Pictures;
+            UploadIntent? pictureIntent = null;
+            string? finalPictureKey = null;
 
+            if (request.NewPictureIntentId.HasValue)
+            {
+                var validation = await uploadIntentValidator.ValidateAndLoadAsync(
+                    uploadIntentConfiguration,
+                    request.NewPictureIntentId.Value, request.UserId, cancellationToken);
+                if (validation.IsError)
+                    return validation.Errors;
+
+                pictureIntent = validation.Value;
+                playListEntity.Pictures = new PlayListPictures 
+                { 
+                    OriginalName = pictureIntent.ObjectName,
+                    SmallName = playListConfiguration.Routes.PresetSmallPicture,
+                    MediumName = playListConfiguration.Routes.PresetMediumPicture,
+                    LargeName = playListConfiguration.Routes.PresetLargePicture
+                };
+                finalPictureKey = playListConfiguration.Routes.BuildOriginalPicturePath(request.UserId, pictureIntent.ObjectName);
+            }
+
+            database.PlayLists.Update(playListEntity);
+
+            if (pictureIntent != null&& finalPictureKey != null)
+            {
+                var publishResult = await PublishUpdatePlayListPictureSourceEventAsync(
+                    playListEntity.Id, pictureIntent, finalPictureKey, cancellationToken);
+                if (publishResult.IsError)
+                    return publishResult.Errors;
+            }
+
+            try
+            {
+                await database.SaveChangesAsync(cancellationToken);
+            }
+            catch (Exception exception)
+            {
+                logger.LogError(exception, "Failed to update playlist {PlayListId}", playListEntity.Id);
+                return Error.Failure(description: $"Failed to update playlist {playListEntity.Id}");
+            }
+
+            var coverTrackIds = await database.PlayListHasTracks
+                .AsNoTracking()
+                .Where(plt => plt.PlayListId == playListEntity.Id)
+                .OrderBy(plt => plt.Position)
+                .Take(PlayListApplicationResponse.CoverTrackCount)
+                .Select(plt => plt.TrackId)
+                .ToListAsync(cancellationToken);
+
+            logger.LogInformation("Updated playlist {PlayListId}", playListEntity.Id);
+            return PlayListApplicationResponse.FromEntity(playListEntity, coverTrackIds);
+        }
+
+        async Task<ErrorOr<Success>> PublishUpdatePlayListPictureSourceEventAsync(
+            Guid playListId,
+            UploadIntent pictureIntent,
+            string finalPictureKey,
+            CancellationToken cancellationToken)
+        {
+            try
+            {
                 await eventBus.PublishAsync(
                     new UpdatePlayListPictureSourceEvent(
-                        playList.Id, picture.Intent.Id, picture.Intent.Bucket, picture.Intent.Key, picture.FinalKey, picture.Sizes),
+                        playListId,
+                        pictureIntent.Id,
+                        storageConfiguration.Bucket,
+                        pictureIntent.Key,
+                        finalPictureKey,
+                        new ImageSize(
+                            playListConfiguration.Routes.SmallPicturesPath,
+                            playListConfiguration.PicturesSizes.SmallPictureWidth,
+                            playListConfiguration.PicturesSizes.SmallPictureHeight),
+                        new ImageSize(
+                            playListConfiguration.Routes.MediumPicturesPath,
+                            playListConfiguration.PicturesSizes.MediumPictureWidth,
+                            playListConfiguration.PicturesSizes.MediumPictureHeight),
+                        new ImageSize(
+                            playListConfiguration.Routes.LargePicturesPath,
+                            playListConfiguration.PicturesSizes.LargePictureWidth,
+                            playListConfiguration.PicturesSizes.LargePictureHeight)),
                     cancellationToken);
+                return new Success();
+            }
+            catch (Exception exception)
+            {
+                logger.LogError(exception, "Failed to publish update playlist picture source event for playlist {PlayListId}", playListId);
+                return Error.Failure(description: $"Failed to publish update playlist picture source event for playlist {playListId}");
             }
-
-            await database.SaveChangesAsync(cancellationToken);
-
-            logger.LogInformation("Updated playlist {PlayListId}", playList.Id);
-
-            return await database.PlayLists
-                .AsNoTracking()
-                .Where(p => p.Id == playList.Id)
-                .SelectResponse()
-                .SingleAsync(cancellationToken);
         }
     }
 }

backend/Core/Musify.Application/Services/TrackStreamIssuer.cs

@@ -1,20 +1,28 @@
 using Musify.Application.Configuration;
 using Musify.Application.Contracts;
 using Musify.Application.Tracks.Responses;
+using Musify.Domain.Entities;
 
-namespace Musify.Application.Services
-{
-    /// <summary>Builds the stream URL and signed ticket for a processed track. It never touches the database.</summary>
-    public sealed class TrackStreamIssuer(
+namespace Musify.Application.Services;
+
+public sealed class TrackStreamIssuer(
+    IDatabase database,
     IStreamTicketService ticketService,
     TrackConfiguration trackConfiguration,
     StreamGatewayConfiguration streamGatewayConfiguration,
     PlaybackConfiguration playbackConfiguration)
-    {
-        public TrackStreamResponse Issue(string audioFolderName, long? userId, Guid? listenId)
+{
+    public async Task<TrackStreamResponse> IssueAsync(
+        Guid trackId,
+        string audioFolderName,
+        long? userId,
+        CancellationToken cancellationToken)
     {
         var folderPath = trackConfiguration.Routes.BuildProcessedAudioPath(audioFolderName);
-            var ticket = ticketService.IssueTicket(userId, $"{folderPath}/", AnonymousFragmentBytes(userId));
+        var keyPrefix = $"{folderPath}/";
+
+        var maxBytes = AnonymousFragmentBytes(userId);
+        var ticket = ticketService.IssueTicket(userId, keyPrefix, maxBytes);
 
         var manifestUrl = string.Join('/',
             streamGatewayConfiguration.PublicBaseUrl.TrimEnd('/'),
@@ -22,15 +30,27 @@ namespace Musify.Application.Services
             folderPath,
             streamGatewayConfiguration.AudioFileName);
 
-            return new TrackStreamResponse(manifestUrl, ticket.Token, ticket.ExpiresInSeconds, listenId);
+        // Anonymous listeners have no User row to satisfy ListeningHistory's foreign key against, and
+        // their plays aren't "history" anyone can look back on anyway, so there's nothing to record.
+        if (userId is not null)
+        {
+            var newListeningHistory = new ListeningHistory
+            {
+                UserId = userId.Value,
+                TrackId = trackId,
+            };
+            await database.ListeningHistories.AddAsync(newListeningHistory, cancellationToken);
+            await database.SaveChangesAsync(cancellationToken);
+        }
+
+        return new TrackStreamResponse(manifestUrl, ticket.Token, ticket.ExpiresInSeconds);
     }
 
     private long? AnonymousFragmentBytes(long? userId)
     {
-            if (userId != null || playbackConfiguration.AnonymousFragmentSeconds <= 0)
+        if (userId is not null || playbackConfiguration.AnonymousFragmentSeconds <= 0)
             return null;
 
         return (long)playbackConfiguration.AnonymousFragmentSeconds * playbackConfiguration.EstimatedAudioBytesPerSecond;
     }
-    }
 }

backend/Core/Musify.Application/Services/UploadIntentIssuer.cs

@@ -1,134 +0,0 @@
-using ErrorOr;
-using Microsoft.EntityFrameworkCore;
-using Microsoft.Extensions.Logging;
-using Musify.Application.Configuration;
-using Musify.Application.Contracts;
-using Musify.Application.Pictures.Responses;
-using Musify.Application.Shared;
-using Musify.Domain.Entities;
-using Musify.Domain.ValueObjects;
-
-namespace Musify.Application.Services
-{
-    public sealed record UploadRequest(
-        UploadIntentPurpose Purpose,
-        PictureRoutes Routes,
-        string FileType,
-        string ContentType,
-        long? ExpectedSizeBytes);
-
-    public sealed record IssuedUpload(
-        Guid IntentId,
-        string Key,
-        string ObjectName,
-        string ContentType,
-        string UploadUrl);
-
-    /// <summary>Issues pre-signed upload URLs and the upload intents that track them, checking the user quota first.</summary>
-    public sealed class UploadIntentIssuer(
-        IDatabase database,
-        IStorageService storageService,
-        UploadIntentValidator uploadIntentValidator,
-        ApplicationStorageConfiguration storageConfiguration,
-        UploadIntentConfiguration uploadIntentConfiguration,
-        ILogger<UploadIntentIssuer> logger)
-    {
-        public async Task<ErrorOr<IReadOnlyList<IssuedUpload>>> IssueAsync(
-            long userId,
-            IReadOnlyList<UploadRequest> requests,
-            CancellationToken cancellationToken)
-        {
-            var userExists = await database.Users
-                .AsNoTracking()
-                .AnyAsync(user => user.Id == userId, cancellationToken);
-            if (!userExists)
-                return AppErrors.NotFound("User", userId);
-
-            var planned = requests
-                .Select(request =>
-                {
-                    var objectName = $"{Guid.NewGuid()}.{request.FileType.TrimStart('.').ToLowerInvariant()}";
-                    var key = request.Routes.BuildTempPath(uploadIntentConfiguration.TempRootPrefix, userId, objectName);
-                    var size = request.ExpectedSizeBytes ?? DefaultSize(request.Purpose);
-                    return (Request: request, ObjectName: objectName, Key: key, Size: size);
-                })
-                .ToList();
-
-            await using var transaction = await database.BeginTransactionAsync(
-                System.Data.IsolationLevel.Serializable, cancellationToken);
-
-            var quota = await uploadIntentValidator.CheckQuotaAsync(
-                userId, planned.Sum(item => item.Size), planned.Count, cancellationToken);
-            if (quota.IsError)
-                return quota.Errors;
-
-            var expiresIn = TimeSpan.FromSeconds(uploadIntentConfiguration.UploadUrlExpiresInSeconds);
-            var expiresAt = DateTime.UtcNow + expiresIn;
-            var issued = new List<IssuedUpload>(planned.Count);
-
-            foreach (var item in planned)
-            {
-                var uploadUrl = await storageService.GetUploadUrlAsync(
-                    storageConfiguration.Bucket, item.Key, item.Request.ContentType, expiresIn, cancellationToken: cancellationToken);
-
-                var intent = new UploadIntent
-                {
-                    UserId = userId,
-                    Bucket = storageConfiguration.Bucket,
-                    Key = item.Key,
-                    ObjectName = item.ObjectName,
-                    ContentType = item.Request.ContentType,
-                    ExpectedSizeBytes = item.Size,
-                    Purpose = item.Request.Purpose,
-                    ExpiresAt = expiresAt,
-                };
-
-                await database.UploadIntents.AddAsync(intent, cancellationToken);
-                issued.Add(new IssuedUpload(intent.Id, item.Key, item.ObjectName, item.Request.ContentType, uploadUrl));
-            }
-
-            await database.SaveChangesAsync(cancellationToken);
-            await transaction.CommitAsync(cancellationToken);
-
-            logger.LogInformation("Issued {Count} upload intents for user {UserId} ({Purposes})",
-                issued.Count, userId, string.Join('/', planned.Select(item => item.Request.Purpose)));
-
-            return issued;
-        }
-
-        public async Task<ErrorOr<IssuedUpload>> IssueOneAsync(long userId, UploadRequest request, CancellationToken cancellationToken)
-        {
-            var issued = await IssueAsync(userId, [request], cancellationToken);
-            return issued.IsError ? issued.Errors : issued.Value[0];
-        }
-
-        public async Task<ErrorOr<PictureUploadResponse>> IssuePictureAsync(
-            long userId,
-            UploadIntentPurpose purpose,
-            IPictureOwnerConfiguration owner,
-            string fileType,
-            string contentType,
-            long? expectedSizeBytes,
-            CancellationToken cancellationToken)
-        {
-            var issued = await IssueOneAsync(
-                userId, new UploadRequest(purpose, owner.Routes, fileType, contentType, expectedSizeBytes), cancellationToken);
-            if (issued.IsError)
-                return issued.Errors;
-
-            return new PictureUploadResponse(
-                issued.Value.IntentId,
-                storageConfiguration.Bucket,
-                issued.Value.Key,
-                issued.Value.ObjectName,
-                issued.Value.ContentType,
-                uploadIntentConfiguration.UploadUrlExpiresInSeconds,
-                issued.Value.UploadUrl);
-        }
-
-        private long DefaultSize(UploadIntentPurpose purpose) =>
-            purpose == UploadIntentPurpose.TrackAudio
-                ? uploadIntentConfiguration.DefaultExpectedAudioSizeBytes
-                : uploadIntentConfiguration.DefaultExpectedPictureSizeBytes;
-    }
-}

backend/Core/Musify.Application/Services/UploadIntentValidator.cs

@@ -1,78 +1,63 @@
 using ErrorOr;
 using Microsoft.EntityFrameworkCore;
 using Musify.Application.Configuration;
-using Musify.Application.Contracts;
-using Musify.Application.Shared;
 using Musify.Domain.Entities;
 using Musify.Domain.ValueObjects;
+using Musify.Application.Contracts;
 
-namespace Musify.Application.Services
-{
-    public sealed class UploadIntentValidator(
+namespace Musify.Application.Services;
+
+public sealed class UploadIntentValidator(
     IDatabase database,
-        IStorageService storageService,
-        UploadIntentConfiguration config)
-    {
+    IStorageService storageService)
+{
     public async Task<ErrorOr<Success>> CheckQuotaAsync(
+        UploadIntentConfiguration config,
         long userId,
         long requiredBytes,
         int requiredIntentCount,
         CancellationToken cancellationToken)
     {
-            var now = DateTime.UtcNow;
-            var pictureDefault = config.DefaultExpectedPictureSizeBytes;
-            var audioDefault = config.DefaultExpectedAudioSizeBytes;
-
-            var active = await database.UploadIntents
+        var activeIntents = await database.UploadIntents
             .AsNoTracking()
-                .Where(intent => intent.UserId == userId && intent.Status == UploadIntentStatus.Issued && intent.ExpiresAt > now)
-                .GroupBy(_ => 1)
-                .Select(group => new
-                {
-                    Count = group.Count(),
-                    Bytes = group.Sum(intent => intent.ExpectedSizeBytes
-                        ?? (intent.Purpose == UploadIntentPurpose.TrackAudio ? audioDefault : pictureDefault))
-                })
-                .SingleOrDefaultAsync(cancellationToken);
+            .Where(i => i.UserId == userId && i.Status == UploadIntentStatus.Issued)
+            .ToListAsync(cancellationToken);
 
-            if ((active?.Count ?? 0) + requiredIntentCount > config.MaxActiveUploadIntentsPerUser)
+        if (activeIntents.Count + requiredIntentCount > config.MaxActiveUploadIntentsPerUser)
             return Error.Validation(description: "Upload intent limit exceeded. Wait for existing uploads to complete or expire.");
 
-            if ((active?.Bytes ?? 0) + requiredBytes > config.MaxActiveUploadBytesPerUser)
+        var activeBytes = activeIntents.Sum(i => i.ExpectedSizeBytes ?? config.DefaultExpectedPictureSizeBytes);
+        if (activeBytes + requiredBytes > config.MaxActiveUploadBytesPerUser)
             return Error.Validation(description: "Upload byte quota exceeded. Wait for existing uploads to complete or expire.");
 
-            return Result.Success;
+        return new Success();
     }
 
     public async Task<ErrorOr<UploadIntent>> ValidateAndLoadAsync(
+        UploadIntentConfiguration config,
         Guid intentId,
         long userId,
-            UploadIntentPurpose purpose,
         CancellationToken cancellationToken)
     {
         var intent = await database.UploadIntents
             .FirstOrDefaultAsync(i => i.Id == intentId, cancellationToken);
 
-            if (intent == null || intent.UserId != userId)
-                return AppErrors.NotFound("UploadIntent", intentId);
-
-            if (intent.Purpose != purpose)
-                return Error.Validation(description: "Upload intent was issued for a different purpose.");
+        if (intent is null || intent.UserId != userId)
+            return Error.NotFound(description: "Upload intent not found or not accessible.");
 
         if (intent.IsConsumed)
-                return AppErrors.Conflict("UploadIntent.Consumed", "Upload intent has already been consumed.");
+            return Error.Conflict(description: "Upload intent has already been consumed.");
 
-            if (intent.IsExpiredAt(DateTime.UtcNow))
+        if (intent.IsExpired)
             return Error.Validation(description: "Upload intent has expired.");
 
         var metadata = await storageService.HeadObjectAsync(intent.Bucket, intent.Key, cancellationToken);
-            if (metadata == null)
-                return Error.NotFound("UploadIntent.ObjectMissing", "Uploaded object not found in storage. Upload the file first.");
+        if (metadata is null)
+            return Error.NotFound(description: "Uploaded object not found in storage. Upload the file first.");
 
         if (metadata.ContentLength > config.MaxUploadBytes)
             return Error.Validation(description: $"Uploaded file exceeds the maximum allowed size of {config.MaxUploadBytes} bytes.");
 
         return intent;
     }
-    }
 }

backend/Core/Musify.Application/Services/YouTubeTrackProvisioner.cs

@@ -0,0 +1,265 @@
+using ErrorOr;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.Logging;
+using Musify.Application.Configuration;
+using Musify.Application.Contracts;
+using Musify.Domain.Entities;
+using Musify.Domain.ValueObjects;
+
+namespace Musify.Application.Services;
+
+public sealed record YouTubeTrackProvision(ExternalTrack Track, YouTubeSongResult? Song);
+
+public sealed class YouTubeTrackProvisioner(
+    IDatabase database,
+    IYouTubeMusicService youTubeMusicService,
+    TrackConfiguration trackConfiguration,
+    ILogger<YouTubeTrackProvisioner> logger)
+{
+    public Task<ExternalTrack?> FindAsync(string videoId, CancellationToken cancellationToken) =>
+        database.ExternalTracks
+            .Include(track => track.TrackArtists)
+            .ThenInclude(trackArtist => trackArtist.Artist)
+            .SingleOrDefaultAsync(t => t.Source == TrackSource.YouTube && t.ExternalId == videoId, cancellationToken);
+
+    public async Task<ErrorOr<YouTubeTrackProvision>> GetOrCreateAsync(string videoId, CancellationToken cancellationToken)
+    {
+        var existing = await FindAsync(videoId, cancellationToken);
+        if (existing is not null)
+            return new YouTubeTrackProvision(existing, Song: null);
+
+        var songResult = await youTubeMusicService.GetSongAsync(videoId, cancellationToken);
+        if (songResult.IsError)
+            return songResult.Errors;
+
+        var song = songResult.Value;
+
+        var artistRefs = song.Artists
+            .GroupBy(artistRef => artistRef.Id ?? artistRef.Name.ToUpperInvariant())
+            .Select(group => group.First())
+            .ToList();
+
+        var artists = new List<Artist>();
+        foreach (var artistRef in artistRefs)
+            artists.Add(await GetOrCreateArtistAsync(artistRef, cancellationToken));
+
+        var title = Truncate(song.Title, 200);
+        var track = new ExternalTrack
+        {
+            Title = title,
+            NormalizedTitle = title.ToUpperInvariant(),
+            Source = TrackSource.YouTube,
+            ExternalId = videoId,
+            DurationSeconds = song.DurationSeconds,
+            Pictures = new TrackPictures
+            {
+                SmallName = trackConfiguration.Routes.PresetSmallPicture,
+                MediumName = trackConfiguration.Routes.PresetMediumPicture,
+                LargeName = trackConfiguration.Routes.PresetLargePicture,
+                ProcessingStatus = ProcessingStatus.Pending
+            },
+            Audio = new TrackAudio
+            {
+                DownloadRequested = false,
+                TranscodeStatus = ProcessingStatus.Pending
+            }
+        };
+
+        await database.ExternalTracks.AddAsync(track, cancellationToken);
+
+        for (var position = 0; position < artists.Count; position++)
+        {
+            await database.TrackArtists.AddAsync(new TrackArtist
+            {
+                TrackId = track.Id,
+                ArtistId = artists[position].Id,
+                Position = position
+            }, cancellationToken);
+        }
+
+        try
+        {
+            await database.SaveChangesAsync(cancellationToken);
+            logger.LogInformation("Created YouTube track {VideoId} ({TrackId})", videoId, track.Id);
+            return new YouTubeTrackProvision(track, Song: song);
+        }
+        catch (DbUpdateException)
+        {
+            database.ExternalTracks.Remove(track);
+            var refetched = await FindAsync(videoId, cancellationToken);
+            if (refetched is null)
+            {
+                logger.LogWarning("YouTube track {VideoId} creation raced but could not be refetched", videoId);
+                return Error.Conflict(description: "The track was just created by another request. Retry the operation.");
+            }
+            return new YouTubeTrackProvision(refetched, Song: null);
+        }
+    }
+
+    public async Task MaterializeAlbumAsync(string albumExternalId, YouTubeAlbumDetail detail, CancellationToken cancellationToken)
+    {
+        var validTracks = detail.Tracks
+            .Where(track => !string.IsNullOrEmpty(track.VideoId))
+            .ToList();
+        if (validTracks.Count == 0)
+            return;
+
+        var album = await GetOrCreateExternalAlbumAsync(albumExternalId, detail.Album.Title, detail.Album.ThumbnailUrl, cancellationToken);
+
+        var videoIds = validTracks.Select(track => track.VideoId).ToList();
+
+        var tracksByVideoId = await database.ExternalTracks
+            .Where(track => track.Source == TrackSource.YouTube && videoIds.Contains(track.ExternalId))
+            .ToDictionaryAsync(track => track.ExternalId, cancellationToken);
+
+        var linkedTrackIds = (await database.AlbumHasTracks
+            .Where(albumTrack => albumTrack.AlbumId == album.Id)
+            .Select(albumTrack => albumTrack.TrackId)
+            .ToListAsync(cancellationToken))
+            .ToHashSet();
+
+        if (tracksByVideoId.Count == validTracks.Count && linkedTrackIds.Count >= validTracks.Count)
+            return;
+
+        var artistRefs = detail.Album.Artists
+            .GroupBy(artistRef => artistRef.Id ?? artistRef.Name.ToUpperInvariant())
+            .Select(group => group.First())
+            .ToList();
+
+        var albumArtists = new List<Artist>();
+        foreach (var artistRef in artistRefs)
+            albumArtists.Add(await GetOrCreateArtistAsync(artistRef, cancellationToken));
+
+        foreach (var albumTrack in validTracks)
+        {
+            if (!tracksByVideoId.TryGetValue(albumTrack.VideoId, out var track))
+            {
+                track = BuildStubTrack(albumTrack);
+                await database.ExternalTracks.AddAsync(track, cancellationToken);
+
+                for (var position = 0; position < albumArtists.Count; position++)
+                {
+                    await database.TrackArtists.AddAsync(new TrackArtist
+                    {
+                        TrackId = track.Id,
+                        ArtistId = albumArtists[position].Id,
+                        Position = position
+                    }, cancellationToken);
+                }
+
+                tracksByVideoId[albumTrack.VideoId] = track;
+            }
+
+            if (linkedTrackIds.Contains(track.Id))
+                continue;
+
+            await database.AlbumHasTracks.AddAsync(new AlbumHasTrack
+            {
+                AlbumId = album.Id,
+                TrackId = track.Id,
+                TrackNumber = albumTrack.TrackNumber
+            }, cancellationToken);
+            linkedTrackIds.Add(track.Id);
+        }
+
+        try
+        {
+            await database.SaveChangesAsync(cancellationToken);
+            logger.LogInformation("Materialized YouTube album {AlbumId} ({TrackCount} tracks)", albumExternalId, validTracks.Count);
+        }
+        catch (DbUpdateException exception)
+        {
+            logger.LogWarning(exception, "Race while materializing YouTube album {AlbumId}", albumExternalId);
+        }
+    }
+
+    private ExternalTrack BuildStubTrack(YouTubeAlbumTrack albumTrack)
+    {
+        var title = Truncate(albumTrack.Title, 200);
+        return new ExternalTrack
+        {
+            Title = title,
+            NormalizedTitle = title.ToUpperInvariant(),
+            Source = TrackSource.YouTube,
+            ExternalId = albumTrack.VideoId,
+            DurationSeconds = albumTrack.DurationSeconds,
+            Pictures = new TrackPictures
+            {
+                SmallName = trackConfiguration.Routes.PresetSmallPicture,
+                MediumName = trackConfiguration.Routes.PresetMediumPicture,
+                LargeName = trackConfiguration.Routes.PresetLargePicture,
+                ProcessingStatus = ProcessingStatus.Pending
+            },
+            Audio = new TrackAudio
+            {
+                DownloadRequested = false,
+                TranscodeStatus = ProcessingStatus.Pending
+            }
+        };
+    }
+
+    private async Task<Artist> GetOrCreateArtistAsync(YouTubeArtistRef reference, CancellationToken cancellationToken)
+    {
+        var name = Truncate(reference.Name, 200);
+        var normalized = name.ToUpperInvariant();
+        var externalId = reference.Id ?? $"name:{normalized}";
+
+        var existing = await database.Artists.SingleOrDefaultAsync(a => a.ExternalId == externalId, cancellationToken);
+        if (existing is not null)
+            return existing;
+
+        var artist = new Artist
+        {
+            Name = name,
+            NormalizedName = normalized,
+            ExternalId = externalId
+        };
+
+        await database.Artists.AddAsync(artist, cancellationToken);
+
+        try
+        {
+            await database.SaveChangesAsync(cancellationToken);
+            return artist;
+        }
+        catch (DbUpdateException)
+        {
+            database.Artists.Remove(artist);
+            return await database.Artists.SingleAsync(a => a.ExternalId == externalId, cancellationToken);
+        }
+    }
+
+    private async Task<ExternalAlbum> GetOrCreateExternalAlbumAsync(string externalId, string name, string? thumbnailUrl, CancellationToken cancellationToken)
+    {
+        var existing = await database.ExternalAlbums
+            .SingleOrDefaultAsync(album => album.Source == TrackSource.YouTube && album.ExternalId == externalId, cancellationToken);
+        if (existing is not null)
+            return existing;
+
+        var title = Truncate(name, 200);
+        var album = new ExternalAlbum
+        {
+            Title = title,
+            NormalizedTitle = title.ToUpperInvariant(),
+            Source = TrackSource.YouTube,
+            ExternalId = externalId,
+            ThumbnailUrl = string.IsNullOrEmpty(thumbnailUrl) ? null : Truncate(thumbnailUrl, 512)
+        };
+
+        await database.ExternalAlbums.AddAsync(album, cancellationToken);
+
+        try
+        {
+            await database.SaveChangesAsync(cancellationToken);
+            return album;
+        }
+        catch (DbUpdateException)
+        {
+            database.ExternalAlbums.Remove(album);
+            return await database.ExternalAlbums.SingleAsync(a => a.Source == TrackSource.YouTube && a.ExternalId == externalId, cancellationToken);
+        }
+    }
+
+    private static string Truncate(string value, int maxLength) =>
+        value.Length <= maxLength ? value : value[..maxLength];
+}

backend/Core/Musify.Application/Shared/AppErrors.cs

@@ -1,16 +0,0 @@
-using ErrorOr;
-
-namespace Musify.Application.Shared
-{
-    public static class AppErrors
-    {
-        public static Error NotFound(string entity, object id) =>
-            Error.NotFound($"{entity}.NotFound", $"{entity} {id} was not found.");
-
-        public static Error Forbidden(string entity, object id) =>
-            Error.Forbidden($"{entity}.Forbidden", $"You do not have permission to modify {entity} {id}.");
-
-        public static Error Conflict(string code, string description) =>
-            Error.Conflict(code, description);
-    }
-}

backend/Core/Musify.Application/Shared/ImageSize.cs

@@ -1,12 +1,7 @@
-namespace Musify.Application.Shared
+namespace Musify.Application.Shared
 {
     public record ImageSize(
         string SavePath,
         int Width,
         int Height);
-
-    public record ImageSizes(
-        ImageSize Small,
-        ImageSize Medium,
-        ImageSize Large);
 }

backend/Core/Musify.Application/Shared/OwnershipExtensions.cs

@@ -1,29 +0,0 @@
-using ErrorOr;
-using Microsoft.EntityFrameworkCore;
-using Musify.Domain.Abstractions;
-using Musify.Domain.ValueObjects;
-
-namespace Musify.Application.Shared
-{
-    public static class OwnershipExtensions
-    {
-        /// <summary>
-        /// Loads an active, tracked entity owned by <paramref name="userId"/>: NotFound when it is missing
-        /// or not active, Forbidden when someone else owns it.
-        /// </summary>
-        public static async Task<ErrorOr<T>> FindOwnedAsync<T>(
-            this DbSet<T> set, Guid id, long userId, CancellationToken cancellationToken)
-            where T : class, IOwnedEntity, IHasLifeCycle
-        {
-            var entity = await set.SingleOrDefaultAsync(
-                e => e.Id == id && e.LifeCycleStatus == LifeCycleStatus.Active, cancellationToken);
-
-            if (entity == null)
-                return AppErrors.NotFound(typeof(T).Name, id);
-
-            return entity.OwnerUserId == userId
-                ? entity
-                : AppErrors.Forbidden(typeof(T).Name, id);
-        }
-    }
-}

backend/Core/Musify.Application/Shared/PaginatedResponse.cs

@@ -0,0 +1,26 @@
+using X.PagedList;
+
+namespace Musify.Application.Shared
+{
+    public record PaginatedResponse<T>(
+        IReadOnlyCollection<T> Items,
+        int PageNumber,
+        int PageSize,
+        int PageCount,
+        int TotalItemCount,
+        bool HasNextPage,
+        bool HasPreviousPage)
+    {
+        public static PaginatedResponse<T> FromPagedList(IPagedList<T> pagedList)
+        {
+            return new PaginatedResponse<T>(
+                pagedList.ToArray(),
+                pagedList.PageNumber,
+                pagedList.PageSize,
+                pagedList.PageCount,
+                pagedList.TotalItemCount,
+                pagedList.HasNextPage,
+                pagedList.HasPreviousPage);
+        }
+    }
+}

backend/Core/Musify.Application/Shared/Pagination.cs

@@ -1,46 +0,0 @@
-using Microsoft.EntityFrameworkCore;
-
-namespace Musify.Application.Shared
-{
-    public record PageRequest(int PageNumber = 1, int PageSize = 20)
-    {
-        public const int MaxPageSize = 100;
-    }
-
-    public record PaginatedResponse<T>(
-        IReadOnlyList<T> Items,
-        int PageNumber,
-        int PageSize,
-        int PageCount,
-        int TotalItemCount,
-        bool HasNextPage,
-        bool HasPreviousPage);
-
-    public static class PaginationExtensions
-    {
-        /// <summary>Counts and pages the same (already filtered, ordered and projected) query.</summary>
-        public static async Task<PaginatedResponse<T>> ToPaginatedAsync<T>(
-            this IQueryable<T> query, PageRequest page, CancellationToken cancellationToken)
-        {
-            var pageNumber = Math.Max(page.PageNumber, 1);
-            var pageSize = Math.Clamp(page.PageSize, 1, PageRequest.MaxPageSize);
-
-            var totalCount = await query.CountAsync(cancellationToken);
-            var items = await query
-                .Skip((pageNumber - 1) * pageSize)
-                .Take(pageSize)
-                .ToListAsync(cancellationToken);
-
-            var pageCount = (int)Math.Ceiling(totalCount / (double)pageSize);
-
-            return new PaginatedResponse<T>(
-                items,
-                pageNumber,
-                pageSize,
-                pageCount,
-                totalCount,
-                HasNextPage: pageNumber < pageCount,
-                HasPreviousPage: pageNumber > 1 && pageCount > 0);
-        }
-    }
-}