Musify/backend/Tests/Musify.Application.Tests/TestSupport/TestDatabase.cs

using Microsoft.Data.Sqlite;
using Microsoft.EntityFrameworkCore;
using Musify.Application.Contracts;
using Musify.Domain.Entities;

namespace Musify.Application.Tests.TestSupport
{
    /// <summary>
    /// An <see cref="IDatabase"/> backed by a private, in-memory SQLite database.
    /// </summary>
    /// <remarks>
    /// <para>
    /// <see cref="IDatabase"/> exposes raw <see cref="DbSet{TEntity}"/> properties, so handlers
    /// compose real LINQ queries (<c>Where</c>, <c>Select</c>, <c>Include</c>, ...) against it.
    /// Substituting <see cref="IDatabase"/> with a mock cannot express that — there is no
    /// <see cref="IQueryable{T}"/> provider behind a mock. SQLite's in-memory mode gives us a real
    /// relational engine instead: fast, no external dependency, and — unlike the EF Core InMemory
    /// provider — it actually supports transactions, which two handlers rely on.
    /// </para>
    /// <para>
    /// The model mirrors the parts of <c>Musify.Infrastructure.Persistence.Database</c> that affect
    /// query shape (owned types, table-per-type inheritance, unique indexes). MassTransit outbox/saga
    /// state and Postgres-specific configuration are left out — the Application layer never touches
    /// them.
    /// </para>
    /// </remarks>
    public sealed class TestDatabase : DbContext, IDatabase
    {
        private readonly SqliteConnection connection;

        private TestDatabase(SqliteConnection connection, DbContextOptions<TestDatabase> options)
            : base(options)
        {
            this.connection = connection;
        }

        /// <summary>
        /// Creates a fresh, empty database with its own private connection. Call <see cref="Seed"/>
        /// (via <see cref="Seeding.EntitySeedExtensions"/>) to populate it, then <see cref="DisposeAsync"/>
        /// when the test is done.
        /// </summary>
        public static async Task<TestDatabase> CreateAsync()
        {
            var connection = new SqliteConnection("Filename=:memory:");
            await connection.OpenAsync();

            var options = new DbContextOptionsBuilder<TestDatabase>()
                .UseSqlite(connection)
                .Options;

            var database = new TestDatabase(connection, options);
            await database.Database.EnsureCreatedAsync();
            return database;
        }

        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            base.OnModelCreating(modelBuilder);

            modelBuilder.Entity<Track>().OwnsOne(track => track.Pictures);
            modelBuilder.Entity<Track>().Navigation(track => track.Pictures).IsRequired();

            modelBuilder.Entity<Track>().OwnsOne(track => track.Audio);
            modelBuilder.Entity<Track>().Navigation(track => track.Audio).IsRequired();

            modelBuilder.Entity<LocalTrack>().ToTable("LocalTracks");

            modelBuilder.Entity<LocalTrack>()
                .HasOne(track => track.Owner)
                .WithMany()
                .HasForeignKey(track => track.OwnerUserId)
                .OnDelete(DeleteBehavior.Restrict);

            modelBuilder.Entity<ExternalTrack>().ToTable("ExternalTracks");

            modelBuilder.Entity<ExternalTrack>()
                .HasIndex(track => new { track.Source, track.ExternalId })
                .IsUnique();

            modelBuilder.Entity<TrackArtist>()
                .HasKey(trackArtist => new { trackArtist.TrackId, trackArtist.ArtistId });

            modelBuilder.Entity<TrackArtist>()
                .HasOne(trackArtist => trackArtist.Track)
                .WithMany(track => track.TrackArtists)
                .HasForeignKey(trackArtist => trackArtist.TrackId)
                .OnDelete(DeleteBehavior.Cascade);

            modelBuilder.Entity<TrackArtist>()
                .HasOne(trackArtist => trackArtist.Artist)
                .WithMany(artist => artist.TrackArtists)
                .HasForeignKey(trackArtist => trackArtist.ArtistId)
                .OnDelete(DeleteBehavior.Cascade);

            modelBuilder.Entity<Artist>()
                .HasIndex(artist => artist.ExternalId)
                .IsUnique();

            modelBuilder.Entity<PlayList>().OwnsOne(playList => playList.Pictures);
            modelBuilder.Entity<PlayList>().Navigation(playList => playList.Pictures).IsRequired();

            modelBuilder.Entity<Album>().OwnsOne(album => album.Pictures);
            modelBuilder.Entity<Album>().Navigation(album => album.Pictures).IsRequired(false);

            modelBuilder.Entity<UserAlbum>().ToTable("UserAlbums");

            modelBuilder.Entity<UserAlbum>()
                .HasOne(album => album.Owner)
                .WithMany()
                .HasForeignKey(album => album.OwnerUserId)
                .OnDelete(DeleteBehavior.Restrict);

            modelBuilder.Entity<ExternalAlbum>().ToTable("ExternalAlbums");

            modelBuilder.Entity<ExternalAlbum>()
                .HasIndex(album => new { album.Source, album.ExternalId })
                .IsUnique();

            modelBuilder.Entity<AlbumHasTrack>()
                .HasOne(albumTrack => albumTrack.Album)
                .WithMany(album => album.AlbumTracks)
                .HasForeignKey(albumTrack => albumTrack.AlbumId)
                .OnDelete(DeleteBehavior.Cascade);

            modelBuilder.Entity<AlbumHasTrack>()
                .HasOne(albumTrack => albumTrack.Track)
                .WithMany(track => track.AlbumTracks)
                .HasForeignKey(albumTrack => albumTrack.TrackId)
                .OnDelete(DeleteBehavior.Cascade);

            modelBuilder.Entity<AlbumHasTrack>()
                .HasIndex(albumTrack => new { albumTrack.AlbumId, albumTrack.TrackId })
                .IsUnique();

            modelBuilder.Entity<Mix>()
                .HasIndex(mix => new { mix.UserId, mix.Position });

            modelBuilder.Entity<MixItem>()
                .HasOne(item => item.Mix)
                .WithMany(mix => mix.Items)
                .HasForeignKey(item => item.MixId)
                .OnDelete(DeleteBehavior.Cascade);

            modelBuilder.Entity<MixItem>()
                .HasOne(item => item.Track)
                .WithMany()
                .HasForeignKey(item => item.TrackId)
                .IsRequired(false)
                .OnDelete(DeleteBehavior.Cascade);

            modelBuilder.Entity<MixItem>()
                .HasIndex(item => new { item.MixId, item.Position });
        }

        public DbSet<User> Users => Set<User>();

        public DbSet<PlayList> PlayLists => Set<PlayList>();

        public DbSet<Album> Albums => Set<Album>();

        public DbSet<UserAlbum> UserAlbums => Set<UserAlbum>();

        public DbSet<ExternalAlbum> ExternalAlbums => Set<ExternalAlbum>();

        public DbSet<AlbumHasTrack> AlbumHasTracks => Set<AlbumHasTrack>();

        public DbSet<Track> Tracks => Set<Track>();

        public DbSet<LocalTrack> LocalTracks => Set<LocalTrack>();

        public DbSet<ExternalTrack> ExternalTracks => Set<ExternalTrack>();

        public DbSet<Artist> Artists => Set<Artist>();

        public DbSet<TrackArtist> TrackArtists => Set<TrackArtist>();

        public DbSet<UserHasTrack> UserHasTracks => Set<UserHasTrack>();

        public DbSet<PlayListHasTrack> PlayListHasTracks => Set<PlayListHasTrack>();

        public DbSet<Mix> Mixes => Set<Mix>();

        public DbSet<MixItem> MixItems => Set<MixItem>();

        public DbSet<Upload> Uploads => Set<Upload>();

        public DbSet<UploadIntent> UploadIntents => Set<UploadIntent>();

        public DbSet<ListeningHistory> ListeningHistories => Set<ListeningHistory>();

        public async Task<IDatabaseTransaction> BeginTransactionAsync(System.Data.IsolationLevel isolationLevel, CancellationToken cancellationToken)
        {
            var transaction = await Database.BeginTransactionAsync(isolationLevel, cancellationToken);
            return new SqliteDatabaseTransaction(transaction);
        }

        public override async ValueTask DisposeAsync()
        {
            await base.DisposeAsync();
            await connection.DisposeAsync();
        }

        private sealed class SqliteDatabaseTransaction(Microsoft.EntityFrameworkCore.Storage.IDbContextTransaction inner)
            : IDatabaseTransaction
        {
            public Task CommitAsync(CancellationToken cancellationToken = default) =>
                inner.CommitAsync(cancellationToken);

            public ValueTask DisposeAsync() => inner.DisposeAsync();
        }
    }
}