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

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

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

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

            Assert.False(result.IsError);
            var link = Assert.Single(await Database.PlayListHasTracks.ToListAsync(TestContext.Current.CancellationToken));
            Assert.Equal(0, link.Position);
        }

        [Fact]
        public async Task Handle_PlayListAlreadyHasTracks_AppendsAtNextPosition()
        {
            var owner = TestEntities.User();
            var playList = TestEntities.PlayList(owner.Id);
            var existingTrack = TestEntities.Track(owner, "Existing");
            var newTrack = TestEntities.Track(owner, "New");
            await SeedAsync(
                owner, playList, existingTrack, newTrack,
                new PlayListHasTrack { PlayListId = playList.Id, TrackId = existingTrack.Id, Position = 0 });

            var result = await CreateHandler().Handle(new AddTracksToPlayListCommand(owner.Id, playList.Id, [newTrack.Id]), TestContext.Current.CancellationToken);

            Assert.False(result.IsError);
            var newLink = await Database.PlayListHasTracks.SingleAsync(link => link.TrackId == newTrack.Id, TestContext.Current.CancellationToken);
            Assert.Equal(1, newLink.Position);
        }

        [Fact]
        public async Task Handle_PlayListMissing_ReturnsNotFound()
        {
            var result = await CreateHandler().Handle(new AddTracksToPlayListCommand(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 AddTracksToPlayListCommand(stranger.Id, playList.Id, [Guid.NewGuid()]), TestContext.Current.CancellationToken);

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

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

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

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

        [Fact]
        public async Task Handle_TrackAlreadyInPlayList_IsSkipped()
        {
            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 AddTracksToPlayListCommand(owner.Id, playList.Id, [track.Id]), TestContext.Current.CancellationToken);

            Assert.False(result.IsError);
            Assert.Single(await Database.PlayListHasTracks.ToListAsync(TestContext.Current.CancellationToken));
        }

        [Fact]
        public async Task TrySaveChangesAsync_DuplicatePlayListTrack_MapsTheUniqueViolationToTheGivenError()
        {
            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 });
            Database.PlayListHasTracks.Add(new PlayListHasTrack { PlayListId = playList.Id, TrackId = track.Id, Position = 1 });

            var result = await Database.TrySaveChangesAsync(Error.Conflict("Test.Duplicate", "duplicate"), TestContext.Current.CancellationToken);

            Assert.Equal("Test.Duplicate", result.FirstError.Code);
        }

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

            var result = await CreateHandler().Handle(
                new AddTracksToPlayListCommand(owner.Id, playList.Id, [first.Id, existing.Id, second.Id, first.Id]),
                TestContext.Current.CancellationToken);

            Assert.False(result.IsError);
            var links = await Database.PlayListHasTracks.OrderBy(link => link.Position).ToListAsync(TestContext.Current.CancellationToken);
            Assert.Equal([existing.Id, first.Id, second.Id], links.Select(link => link.TrackId));
            Assert.Equal([0, 1, 2], links.Select(link => link.Position));
        }
    }
}