Musify/backend/Tests/Musify.Application.Tests/Albums/AddTrackToAlbumCommandHandlerTests.cs

using ErrorOr;
using Microsoft.EntityFrameworkCore;
using Musify.Application.Albums;
using Musify.Application.Tests.TestSupport;
using Musify.Domain.Entities;
using Xunit;

namespace Musify.Application.Tests.Albums;

public sealed class AddTrackToAlbumCommandHandlerTests : HandlerTestBase
{
    private AddTrackToAlbumCommandHandler CreateHandler() => new(Database, NoOpLogger<AddTrackToAlbumCommandHandler>());

    [Fact]
    public async Task Handle_FirstTrack_AddsItAtNumberOne()
    {
        var owner = TestEntities.User();
        var album = TestEntities.Album(owner.Id);
        var track = TestEntities.Track(owner);
        await SeedAsync(owner, album, track);

        var result = await CreateHandler().Handle(new AddTrackToAlbumCommand(owner.Id, album.Id, track.Id), TestContext.Current.CancellationToken);

        Assert.False(result.IsError);
        var link = Assert.Single(await Database.AlbumHasTracks.ToListAsync(TestContext.Current.CancellationToken));
        Assert.Equal(1, link.TrackNumber);
    }

    [Fact]
    public async Task Handle_AlbumMissing_ReturnsNotFound()
    {
        var owner = TestEntities.User();
        var track = TestEntities.Track(owner);
        await SeedAsync(owner, track);

        var result = await CreateHandler().Handle(new AddTrackToAlbumCommand(owner.Id, Guid.NewGuid(), track.Id), TestContext.Current.CancellationToken);

        Assert.Equal(ErrorType.NotFound, result.FirstError.Type);
    }

    [Fact]
    public async Task Handle_NotOwner_ReturnsForbidden()
    {
        var owner = TestEntities.User(1, "owner");
        var stranger = TestEntities.User(2, "stranger");
        var album = TestEntities.Album(owner.Id);
        var track = TestEntities.Track(owner);
        await SeedAsync(owner, stranger, album, track);

        var result = await CreateHandler().Handle(new AddTrackToAlbumCommand(stranger.Id, album.Id, track.Id), TestContext.Current.CancellationToken);

        Assert.Equal(ErrorType.Forbidden, result.FirstError.Type);
    }

    [Fact]
    public async Task Handle_TrackMissing_ReturnsNotFound()
    {
        var owner = TestEntities.User();
        var album = TestEntities.Album(owner.Id);
        await SeedAsync(owner, album);

        var result = await CreateHandler().Handle(new AddTrackToAlbumCommand(owner.Id, album.Id, Guid.NewGuid()), TestContext.Current.CancellationToken);

        Assert.Equal(ErrorType.NotFound, result.FirstError.Type);
    }

    [Fact]
    public async Task Handle_TrackOwnedByAnotherUser_ReturnsForbidden()
    {
        var owner = TestEntities.User(1, "owner");
        var otherOwner = TestEntities.User(2, "other");
        var album = TestEntities.Album(owner.Id);
        var foreignTrack = TestEntities.Track(otherOwner);
        await SeedAsync(owner, otherOwner, album, foreignTrack);

        var result = await CreateHandler().Handle(new AddTrackToAlbumCommand(owner.Id, album.Id, foreignTrack.Id), TestContext.Current.CancellationToken);

        Assert.Equal(ErrorType.Forbidden, result.FirstError.Type);
    }

    [Fact]
    public async Task Handle_AlreadyInAlbum_ReturnsConflict()
    {
        var owner = TestEntities.User();
        var album = TestEntities.Album(owner.Id);
        var track = TestEntities.Track(owner);
        var link = new AlbumHasTrack { AlbumId = album.Id, TrackId = track.Id, TrackNumber = 1 };
        await SeedAsync(owner, album, track, link);

        var result = await CreateHandler().Handle(new AddTrackToAlbumCommand(owner.Id, album.Id, track.Id), TestContext.Current.CancellationToken);

        Assert.Equal(ErrorType.Conflict, result.FirstError.Type);
    }

    [Fact]
    public async Task Handle_AlbumAlreadyHasTracks_AppendsAtNextNumber()
    {
        var owner = TestEntities.User();
        var album = TestEntities.Album(owner.Id);
        var firstTrack = TestEntities.Track(owner, "First");
        var secondTrack = TestEntities.Track(owner, "Second");
        var existingLink = new AlbumHasTrack { AlbumId = album.Id, TrackId = firstTrack.Id, TrackNumber = 3 };
        await SeedAsync(owner, album, firstTrack, secondTrack, existingLink);

        var result = await CreateHandler().Handle(new AddTrackToAlbumCommand(owner.Id, album.Id, secondTrack.Id), TestContext.Current.CancellationToken);

        Assert.False(result.IsError);
        var newLink = await Database.AlbumHasTracks.SingleAsync(l => l.TrackId == secondTrack.Id, TestContext.Current.CancellationToken);
        Assert.Equal(4, newLink.TrackNumber);
    }
}