using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.Data.Sqlite;
using Xunit;
using ytLive.Models;
using ytLive.Services;
using ytLive.Services.Encoder;
using ytLive.ViewModels;

namespace ytLive.Tests;

/// <summary>
/// 2026-11-05 report: "when I click Loop, the video doesn't play in the preview pane." The switch was
/// enabled and saved, but Loop is only consulted at end-of-file by a LIVE decoder — and a finished
/// decoder could never be started again (`StartAsync` bailed out once it had run once). So a short clip
/// froze on its last frame forever. This pins the fix: a played-out clip can be started again, and
/// turning Loop on for a finished clip restarts it.
/// </summary>
[Collection("RealApp")]
public sealed class MediaPlaybackRestartTests
{
    private readonly RealAppHost _app;

    public MediaPlaybackRestartTests(RealAppHost app) => _app = app;

    [Fact]
    public async Task Pipe_CanPlayAgainAfterANaturalEnd()
    {
        var processStarts = 0;
        using var pipe = new VideoClipPipe(
            "clip.mp4", 1, 1, new FakeLocator(),
            () => { processStarts++; return new EmptyProcess(); },
            delay: (_, _) => Task.CompletedTask,
            audio: false);

        var completions = 0;
        pipe.Completed += () => completions++;

        await pipe.StartAsync();
        await WaitUntil(() => completions == 1);

        await pipe.StartAsync(); // a finished clip must be startable again
        await WaitUntil(() => completions == 2);

        Assert.Equal(2, completions);
        Assert.True(processStarts >= 2, "the second play did not spawn a decoder");
    }

    [Fact]
    public void PlayedOutClip_ShowsAsFinished_AndPlayAgainRestartsIt()
    {
        _app.Run(() =>
        {
            var tempDb = Path.Combine(Path.GetTempPath(), $"ytLlive-test-{Guid.NewGuid():N}.db");
            var videoPath = Path.Combine(Path.GetTempPath(), "short-loop.mp4");
            var decoders = new List<FakeMediaSource>();
            MainViewModel.LayoutPathOverride = tempDb;
            MainViewModel.MediaFrameSourceFactoryOverride = key =>
            {
                var decoder = new FakeMediaSource(key);
                decoders.Add(decoder);
                return decoder;
            };
            MainViewModel.ChromaProbeOverride = new NoProbe();

            var window = new MainWindow();
            var vm = (MainViewModel)window.DataContext;
            try
            {
                window.Show();
                window.UpdateLayout();
                vm.AddMediaSource(videoPath);

                var layer = vm.StagedScene!.Elements.OfType<Source>().Single(s => s.IsMediaSource);
                var decoder = decoders.Single();
                Assert.True(layer.IsMediaRunning, "a freshly added clip must report that it is playing");

                // The clip plays out.
                decoder.RaiseCompleted();
                Assert.False(layer.IsMediaRunning);
                Assert.True(layer.IsMediaFinished);

                // "Play again" restarts the same session from the top.
                vm.ReplayMediaCommand.Execute(layer);
                Assert.True(layer.IsMediaRunning);
                Assert.Equal(2, decoder.StartCount);

                // And turning Loop on for a finished clip restarts it — the reported bug.
                decoder.RaiseCompleted();
                Assert.False(layer.IsMediaRunning);
                layer.MediaIsLooping = true;
                Assert.True(layer.IsMediaRunning, "turning Loop on for a finished clip must start it again");
                Assert.Equal(3, decoder.StartCount);
            }
            finally
            {
                window.Close();
                MainViewModel.ChromaProbeOverride = null;
                MainViewModel.MediaFrameSourceFactoryOverride = null;
                MainViewModel.LayoutPathOverride = null;
                SqliteConnection.ClearAllPools();
                try { File.Delete(tempDb); } catch { /* best-effort cleanup */ }
            }
        });
    }

    private static async Task WaitUntil(Func<bool> condition)
    {
        for (var i = 0; i < 200 && !condition(); i++)
            await Task.Delay(10);
        Assert.True(condition(), "timed out waiting for the clip to finish");
    }

    private sealed class FakeMediaSource : IMediaFrameSource
    {
        public FakeMediaSource(string key) => Key = key;

        public string Key { get; }
        public bool Looping { get; set; }
        public int StartCount { get; private set; }

        public event Action<VideoFrame>? FrameAvailable { add { } remove { } }
        public event Action<ytLive.Services.Audio.AudioSample>? AudioAvailable { add { } remove { } }
        public event Action? Completed;

        public void RaiseCompleted() => Completed?.Invoke();

        public Task StartAsync(CancellationToken cancellationToken = default)
        {
            StartCount++;
            return Task.CompletedTask;
        }

        public Task StopAsync() => Task.CompletedTask;

        public void Dispose()
        {
        }
    }

    private sealed class NoProbe : IChromaProbe
    {
        public Task<VideoFrame?> ProbeAsync(string path, CancellationToken cancellationToken = default)
            => Task.FromResult<VideoFrame?>(null);
    }

    private sealed class EmptyProcess : IDecodeProcess
    {
        public void Start(System.Diagnostics.ProcessStartInfo startInfo) { }
        public Stream StandardOutput => Stream.Null;
        public bool HasExited => true;
        public int ExitCode => 0;
        public void Kill() { }
        public Task WaitForExitAsync(CancellationToken ct = default) => Task.CompletedTask;
        public void Dispose() { }
    }

    private sealed class FakeLocator : IFfmpegLocator
    {
        public Task<string> LocateAsync(CancellationToken ct = default) => Task.FromResult("ffmpeg.exe");
    }
}