using DeepDrftModels.DTOs;
using DeepDrftPublic.Client.Services;
using Microsoft.AspNetCore.Components;

namespace DeepDrftTests;

/// <summary>
/// Unit tests for the play-queue orchestrator (<see cref="QueueService"/>). The queue is pure
/// domain logic over the single-slot player, so it is exercised here against a recording fake
/// (<see cref="FakeStreamingPlayer"/>) — no browser, no JS interop, no DI container. Coverage:
/// enqueue, ordered advance, next/previous bounds, clear, current-index integrity, and
/// auto-advance on the player's <see cref="IPlayerService.TrackEnded"/> signal.
/// </summary>
[TestFixture]
public class QueueServiceTests
{
    private FakeStreamingPlayer _player = null!;
    private QueueService _queue = null!;

    [SetUp]
    public void SetUp()
    {
        _player = new FakeStreamingPlayer();
        _queue = new QueueService();
        _queue.Attach(_player);
    }

    [TearDown]
    public void TearDown() => _queue.Dispose();

    private static List<TrackDto> Tracks(int count) =>
        Enumerable.Range(1, count)
            .Select(i => new TrackDto { EntryKey = $"track-{i}", TrackName = $"Track {i}", TrackNumber = i })
            .ToList();

    // --- Empty-queue invariants (no regression to single-track play) ---

    [Test]
    public void NewQueue_IsEmptyWithCurrentIndexNegativeOne()
    {
        Assert.Multiple(() =>
        {
            Assert.That(_queue.Items, Is.Empty);
            Assert.That(_queue.CurrentIndex, Is.EqualTo(-1));
            Assert.That(_queue.Current, Is.Null);
            Assert.That(_queue.HasNext, Is.False);
            Assert.That(_queue.HasPrevious, Is.False);
        });
    }

    [Test]
    public async Task NextAndPrevious_OnEmptyQueue_AreNoOpsAndDriveNoPlayback()
    {
        await _queue.Next();
        await _queue.Previous();

        Assert.Multiple(() =>
        {
            Assert.That(_queue.CurrentIndex, Is.EqualTo(-1));
            Assert.That(_player.SelectedTracks, Is.Empty);
        });
    }

    // --- PlayRelease: enqueue + ordered start ---

    [Test]
    public async Task PlayRelease_LoadsTracksInOrderAndStreamsFirst()
    {
        var tracks = Tracks(3);

        await _queue.PlayRelease(tracks);

        Assert.Multiple(() =>
        {
            Assert.That(_queue.Items.Select(t => t.EntryKey),
                Is.EqualTo(new[] { "track-1", "track-2", "track-3" }));
            Assert.That(_queue.CurrentIndex, Is.EqualTo(0));
            Assert.That(_queue.Current!.EntryKey, Is.EqualTo("track-1"));
            Assert.That(_player.SelectedTracks.Single().EntryKey, Is.EqualTo("track-1"));
        });
    }

    [Test]
    public async Task PlayRelease_WithStartIndex_StartsMidAlbumAndKeepsRemainderQueued()
    {
        var tracks = Tracks(4);

        await _queue.PlayRelease(tracks, startIndex: 2);

        Assert.Multiple(() =>
        {
            Assert.That(_queue.CurrentIndex, Is.EqualTo(2));
            Assert.That(_queue.Current!.EntryKey, Is.EqualTo("track-3"));
            Assert.That(_player.SelectedTracks.Single().EntryKey, Is.EqualTo("track-3"));
            Assert.That(_queue.HasNext, Is.True);
            Assert.That(_queue.HasPrevious, Is.True);
        });
    }

    [Test]
    public async Task PlayRelease_ClampsOutOfRangeStartIndex()
    {
        var tracks = Tracks(3);

        await _queue.PlayRelease(tracks, startIndex: 99);

        Assert.Multiple(() =>
        {
            Assert.That(_queue.CurrentIndex, Is.EqualTo(2));
            Assert.That(_player.SelectedTracks.Single().EntryKey, Is.EqualTo("track-3"));
        });
    }

    [Test]
    public async Task PlayRelease_WithEmptyTracks_IsNoOp()
    {
        await _queue.PlayRelease(Enumerable.Empty<TrackDto>());

        Assert.Multiple(() =>
        {
            Assert.That(_queue.Items, Is.Empty);
            Assert.That(_queue.CurrentIndex, Is.EqualTo(-1));
            Assert.That(_player.SelectedTracks, Is.Empty);
        });
    }

    [Test]
    public async Task PlayRelease_ReplacesAnExistingQueue()
    {
        await _queue.PlayRelease(Tracks(3));
        var second = new List<TrackDto>
        {
            new() { EntryKey = "x-1", TrackName = "X1" },
            new() { EntryKey = "x-2", TrackName = "X2" },
        };

        await _queue.PlayRelease(second);

        Assert.Multiple(() =>
        {
            Assert.That(_queue.Items, Has.Count.EqualTo(2));
            Assert.That(_queue.Items.Select(t => t.EntryKey), Is.EqualTo(new[] { "x-1", "x-2" }));
            Assert.That(_queue.CurrentIndex, Is.EqualTo(0));
        });
    }

    // --- Next / Previous mechanics and bounds ---

    [Test]
    public async Task Next_AdvancesThroughTracksInOrder()
    {
        await _queue.PlayRelease(Tracks(3));

        await _queue.Next();
        Assert.That(_queue.Current!.EntryKey, Is.EqualTo("track-2"));

        await _queue.Next();
        Assert.That(_queue.Current!.EntryKey, Is.EqualTo("track-3"));

        Assert.That(_player.SelectedTracks.Select(t => t.EntryKey),
            Is.EqualTo(new[] { "track-1", "track-2", "track-3" }));
    }

    [Test]
    public async Task Next_AtLastTrack_IsNoOp()
    {
        await _queue.PlayRelease(Tracks(2), startIndex: 1);

        await _queue.Next();

        Assert.Multiple(() =>
        {
            Assert.That(_queue.CurrentIndex, Is.EqualTo(1));
            Assert.That(_queue.HasNext, Is.False);
            // Only the initial PlayRelease selection — Next at the end drove no further playback.
            Assert.That(_player.SelectedTracks, Has.Count.EqualTo(1));
        });
    }

    [Test]
    public async Task Previous_StepsBackThroughTracks()
    {
        await _queue.PlayRelease(Tracks(3), startIndex: 2);

        await _queue.Previous();

        Assert.Multiple(() =>
        {
            Assert.That(_queue.CurrentIndex, Is.EqualTo(1));
            Assert.That(_queue.Current!.EntryKey, Is.EqualTo("track-2"));
            Assert.That(_player.SelectedTracks.Last().EntryKey, Is.EqualTo("track-2"));
        });
    }

    [Test]
    public async Task Previous_AtFirstTrack_IsNoOp()
    {
        await _queue.PlayRelease(Tracks(3));

        await _queue.Previous();

        Assert.Multiple(() =>
        {
            Assert.That(_queue.CurrentIndex, Is.EqualTo(0));
            Assert.That(_queue.HasPrevious, Is.False);
            Assert.That(_player.SelectedTracks, Has.Count.EqualTo(1));
        });
    }

    // --- Enqueue / EnqueueRange ---

    [Test]
    public void Enqueue_AppendsWithoutChangingCurrentOrStartingPlayback()
    {
        _queue.Enqueue(new TrackDto { EntryKey = "a", TrackName = "A" });

        Assert.Multiple(() =>
        {
            Assert.That(_queue.Items, Has.Count.EqualTo(1));
            Assert.That(_queue.CurrentIndex, Is.EqualTo(-1));
            Assert.That(_player.SelectedTracks, Is.Empty);
        });
    }

    [Test]
    public async Task Enqueue_AfterPlayRelease_ExtendsTheQueueAndEnablesHasNext()
    {
        await _queue.PlayRelease(Tracks(1));
        Assert.That(_queue.HasNext, Is.False);

        _queue.Enqueue(new TrackDto { EntryKey = "appended", TrackName = "Appended" });

        Assert.Multiple(() =>
        {
            Assert.That(_queue.HasNext, Is.True);
            Assert.That(_queue.CurrentIndex, Is.EqualTo(0));
        });
    }

    [Test]
    public void EnqueueRange_AppendsAllTracks()
    {
        _queue.EnqueueRange(Tracks(3));

        Assert.That(_queue.Items, Has.Count.EqualTo(3));
    }

    // --- Clear ---

    [Test]
    public async Task Clear_EmptiesQueueAndResetsIndexWithoutStoppingPlayer()
    {
        await _queue.PlayRelease(Tracks(3));

        _queue.Clear();

        Assert.Multiple(() =>
        {
            Assert.That(_queue.Items, Is.Empty);
            Assert.That(_queue.CurrentIndex, Is.EqualTo(-1));
            Assert.That(_queue.Current, Is.Null);
            // Clear is a queue-state reset; it must not tear the player down.
            Assert.That(_player.StopCount, Is.EqualTo(0));
        });
    }

    // --- QueueChanged notifications ---

    [Test]
    public async Task MutatingOperations_RaiseQueueChanged()
    {
        var count = 0;
        _queue.QueueChanged += () => count++;

        await _queue.PlayRelease(Tracks(3)); // 1
        await _queue.Next();                 // 2
        await _queue.Previous();             // 3
        _queue.Enqueue(new TrackDto { EntryKey = "z", TrackName = "Z" }); // 4
        _queue.Clear();                      // 5

        Assert.That(count, Is.EqualTo(5));
    }

    [Test]
    public void Clear_OnAlreadyEmptyQueue_DoesNotRaiseQueueChanged()
    {
        var raised = false;
        _queue.QueueChanged += () => raised = true;

        _queue.Clear();

        Assert.That(raised, Is.False);
    }

    // --- Auto-advance on TrackEnded ---

    [Test]
    public async Task TrackEnded_AutoAdvancesToNextTrack()
    {
        await _queue.PlayRelease(Tracks(3));

        _player.RaiseTrackEnded();

        Assert.Multiple(() =>
        {
            Assert.That(_queue.CurrentIndex, Is.EqualTo(1));
            Assert.That(_queue.Current!.EntryKey, Is.EqualTo("track-2"));
            Assert.That(_player.SelectedTracks.Last().EntryKey, Is.EqualTo("track-2"));
        });
    }

    [Test]
    public async Task TrackEnded_OnLastTrack_DoesNotAdvanceOrReplay()
    {
        await _queue.PlayRelease(Tracks(2), startIndex: 1);

        _player.RaiseTrackEnded();

        Assert.Multiple(() =>
        {
            Assert.That(_queue.CurrentIndex, Is.EqualTo(1));
            Assert.That(_player.SelectedTracks, Has.Count.EqualTo(1));
        });
    }

    [Test]
    public void TrackEnded_OnEmptyQueue_IsIgnored()
    {
        _player.RaiseTrackEnded();

        Assert.Multiple(() =>
        {
            Assert.That(_queue.CurrentIndex, Is.EqualTo(-1));
            Assert.That(_player.SelectedTracks, Is.Empty);
        });
    }

    /// <summary>
    /// Regression guard for the cross-context spurious-advance bug: a direct single-track play
    /// (Session, StreamNowButton, resume) overwrites the player's CurrentTrack without touching the
    /// queue. When that external track reaches its natural end, TrackEnded fires — but the queue's
    /// Current no longer matches the player's CurrentTrack, so the queue must NOT advance.
    /// </summary>
    [Test]
    public async Task TrackEnded_WhenPlayerCurrentTrackIsNotQueueCurrent_DoesNotAdvance()
    {
        // Load a 3-track album into the queue (queue.Current → track-1, player.CurrentTrack → track-1).
        await _queue.PlayRelease(Tracks(3));
        Assert.That(_queue.CurrentIndex, Is.EqualTo(0));

        // Simulate a direct play (e.g. SessionDetail streams an unrelated track by Id = 99).
        // The player's CurrentTrack is now the session track, but the queue is still on track-1.
        var sessionTrack = new TrackDto { Id = 99, EntryKey = "session-track", TrackName = "Session Mix" };
        _player.SimulateDirectPlay(sessionTrack);

        // The session track finishes naturally — player raises TrackEnded.
        _player.RaiseTrackEnded();

        // The queue must not have advanced: index still 0, and no additional SelectTrackStreaming
        // calls beyond the initial PlayRelease selection.
        Assert.Multiple(() =>
        {
            Assert.That(_queue.CurrentIndex, Is.EqualTo(0), "Queue must not advance when a direct-play track ends");
            Assert.That(_player.SelectedTracks, Has.Count.EqualTo(1), "No further streaming must be triggered by the queue");
            Assert.That(_player.SelectedTracks.Single().EntryKey, Is.EqualTo("track-1"), "Only the original PlayRelease selection must have been streamed");
        });
    }

    [Test]
    public async Task TrackEnded_PlaysWholeAlbumThroughToTheEnd()
    {
        await _queue.PlayRelease(Tracks(3));

        _player.RaiseTrackEnded(); // → track-2
        _player.RaiseTrackEnded(); // → track-3
        _player.RaiseTrackEnded(); // last track: no advance

        Assert.Multiple(() =>
        {
            Assert.That(_queue.CurrentIndex, Is.EqualTo(2));
            Assert.That(_player.SelectedTracks.Select(t => t.EntryKey),
                Is.EqualTo(new[] { "track-1", "track-2", "track-3" }));
        });
    }

    // --- Attach lifecycle ---

    [Test]
    public async Task Dispose_UnsubscribesFromTrackEnded_SoNoAutoAdvanceAfterDispose()
    {
        await _queue.PlayRelease(Tracks(3));
        _queue.Dispose();

        _player.RaiseTrackEnded();

        Assert.That(_queue.CurrentIndex, Is.EqualTo(0));
    }

    [Test]
    public async Task Attach_ToNewPlayer_RedirectsPlaybackAndAutoAdvance()
    {
        var second = new FakeStreamingPlayer();
        _queue.Attach(second);

        await _queue.PlayRelease(Tracks(3));
        Assert.That(second.SelectedTracks.Single().EntryKey, Is.EqualTo("track-1"));

        // The old player's TrackEnded must no longer drive this queue.
        _player.RaiseTrackEnded();
        Assert.That(_queue.CurrentIndex, Is.EqualTo(0));

        // The newly attached player does.
        second.RaiseTrackEnded();
        Assert.That(_queue.CurrentIndex, Is.EqualTo(1));
    }

    /// <summary>
    /// Records the tracks the queue asks the player to stream and lets a test raise the
    /// player's organic end-of-stream signal. Implements the full <see cref="IStreamingPlayerService"/>
    /// surface but only the members the queue actually drives carry behavior; the rest are inert
    /// — the queue touches nothing else, which is exactly the seam this fake pins down.
    /// </summary>
    private sealed class FakeStreamingPlayer : IStreamingPlayerService
    {
        public List<TrackDto> SelectedTracks { get; } = new();
        public int StopCount { get; private set; }

        public void RaiseTrackEnded() => TrackEnded?.Invoke();

        /// <summary>
        /// Sets <see cref="CurrentTrack"/> to <paramref name="track"/> without recording a
        /// <see cref="SelectedTracks"/> entry. Models a direct single-track play (SessionDetail,
        /// StreamNowButton, resume) that overwrites the player state without going through the queue.
        /// </summary>
        public void SimulateDirectPlay(TrackDto track) => CurrentTrack = track;

        public Task SelectTrackStreaming(TrackDto track)
        {
            SelectedTracks.Add(track);
            CurrentTrack = track;
            return Task.CompletedTask;
        }

        public Task Stop()
        {
            StopCount++;
            return Task.CompletedTask;
        }

        public event Action? TrackEnded;

        // Part of the implemented contract but the queue never subscribes to it, so it is
        // intentionally never raised here.
#pragma warning disable CS0067
        public event Action? StateChanged;
#pragma warning restore CS0067

        // Inert remainder of the contract — the queue never invokes these.
        public bool IsInitialized => false;
        public bool IsLoaded => false;
        public bool IsLoading => false;
        public bool IsPlaying => false;
        public bool IsPaused => false;
        public double CurrentTime => 0;
        public double? Duration => null;
        public double Volume => 1.0;
        public double LoadProgress => 0;
        public string? ErrorMessage => null;
        public TrackDto? CurrentTrack { get; private set; }
        public double[]? WaveformProfile => null;
        public EventCallback? OnStateChanged { get; set; }
        public EventCallback? OnTrackSelected { get; set; }
        public bool IsStreamingMode => false;
        public bool CanStartStreaming => false;
        public bool HeaderParsed => false;
        public int BufferedChunks => 0;

        public Task InitializeAsync() => Task.CompletedTask;
        public Task SelectTrack(TrackDto track) => SelectTrackStreaming(track);
        public Task Unload() => Task.CompletedTask;
        public Task TogglePlayPause() => Task.CompletedTask;
        public Task Seek(double position) => Task.CompletedTask;
        public Task SetVolume(double volume) => Task.CompletedTask;
        public Task ClearError() => Task.CompletedTask;
        public Task WarmAudioContext() => Task.CompletedTask;
        public Task StageTrack(TrackDto track) => Task.CompletedTask;
    }
}