Musify/backend/Tests/Musify.Application.Tests/PlayLists/RemoveTrackFromPlayListCommandHandlerTests.cs

using ErrorOr;
using Musify.Application.PlayLists;
using Musify.Application.Tests.TestSupport;
using Musify.Domain.Entities;
using Xunit;

namespace Musify.Application.Tests.PlayLists
{
    public sealed class RemoveTrackFromPlayListCommandHandlerTests : HandlerTestBase
    {
        private RemoveTrackFromPlayListCommandHandler CreateHandler() => new(Database, NoOpLogger<RemoveTrackFromPlayListCommandHandler>());

        [Fact]
        public async Task Handle_TrackInPlayList_RemovesTheLink()
        {
            var owner = TestEntities.User();
            var playList = TestEntities.PlayList(owner.Id);
            var track = TestEntities.Track(owner);
            await SeedAsync(owner, playList, track, new PlayListHasTrack { PlayListId = playList.Id, TrackId = track.Id, Position = 0 });

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

            Assert.False(result.IsError);
            Assert.Empty(Database.PlayListHasTracks);
        }

        [Fact]
        public async Task Handle_PlayListMissing_ReturnsNotFound()
        {
            var result = await CreateHandler().Handle(new RemoveTrackFromPlayListCommand(1, Guid.NewGuid(), Guid.NewGuid()), 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 playList = TestEntities.PlayList(owner.Id);
            await SeedAsync(owner, stranger, playList);

            var result = await CreateHandler().Handle(new RemoveTrackFromPlayListCommand(stranger.Id, playList.Id, Guid.NewGuid()), TestContext.Current.CancellationToken);

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

        [Fact]
        public async Task Handle_TrackNotLinked_ReturnsNotFound()
        {
            var owner = TestEntities.User();
            var playList = TestEntities.PlayList(owner.Id);
            await SeedAsync(owner, playList);

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

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

        [Fact]
        public async Task Handle_TrackInTheMiddle_RenumbersTheRemainingTracks()
        {
            var owner = TestEntities.User();
            var playList = TestEntities.PlayList(owner.Id);
            var first = TestEntities.Track(owner, "First");
            var second = TestEntities.Track(owner, "Second");
            var third = TestEntities.Track(owner, "Third");
            await SeedAsync(
                owner, playList, first, second, third,
                new PlayListHasTrack { PlayListId = playList.Id, TrackId = first.Id, Position = 0 },
                new PlayListHasTrack { PlayListId = playList.Id, TrackId = second.Id, Position = 1 },
                new PlayListHasTrack { PlayListId = playList.Id, TrackId = third.Id, Position = 2 });

            var result = await CreateHandler().Handle(new RemoveTrackFromPlayListCommand(owner.Id, playList.Id, second.Id), TestContext.Current.CancellationToken);

            Assert.False(result.IsError);
            var remaining = Database.PlayListHasTracks.OrderBy(link => link.Position).ToList();
            Assert.Equal([first.Id, third.Id], remaining.Select(link => link.TrackId));
            Assert.Equal([0, 1], remaining.Select(link => link.Position));
        }
    }
}