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.ViewModels;

namespace ytLive.Tests;

/// <summary>
/// TASK 21 Good Dog (2026-11-05): a MediaSource layer exists but nothing ever started
/// a decode session, so a video file layer rendered nothing in a running app. This
/// drives the real add path through <see cref="MainWindow"/> and asserts the piece the
/// unit adds — the session lifecycle: adding a video file starts exactly one decoder,
/// the decoded frames reach the layer, a loop flip reaches that decoder, and removing
/// the layer stops it.
/// </summary>
[Collection("RealApp")]
public sealed class MediaSourceAcquisitionTests
{
    private readonly RealAppHost _app;

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

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

            var window = new MainWindow();
            var vm = (MainViewModel)window.DataContext;
            try
            {
                window.Show();
                window.UpdateLayout();
                var scene = vm.StagedScene!;

                vm.AddMediaSource(videoPath);

                var layer = scene.Elements.OfType<Source>().Single(s => s.IsMediaSource);
                Assert.Equal(videoPath, layer.MediaPath);
                Assert.Equal(SourceType.MediaSource, layer.Type);
                Assert.Single(decoders);

                var decoder = decoders[0];
                Assert.Equal(videoPath, decoder.Key);
                Assert.Equal(1, decoder.StartCount);

                // A decoded frame reaches the layer the preview/renderer draws from —
                // otherwise the session would be running and still invisible.
                Assert.Null(layer.DisplaySource);
                decoder.Emit(new VideoFrame(64, 36, new byte[64 * 36 * 4]));
                Assert.NotNull(layer.DisplaySource);

                // Loop intent is per Source; the shared session is the per-path answer.
                Assert.False(decoder.Looping);
                layer.MediaIsLooping = true;
                Assert.True(decoder.Looping);

                vm.RemoveSourceCommand.Execute(layer);

                Assert.DoesNotContain(layer, scene.Elements);
                Assert.Equal(1, decoder.StopCount);
            }
            finally
            {
                window.Close();
                MainViewModel.MediaFrameSourceFactoryOverride = null;
                MainViewModel.LayoutPathOverride = null;
                SqliteConnection.ClearAllPools();
                try { File.Delete(tempDb); } catch { /* best-effort cleanup */ }
            }
        });
    }

    /// <summary>Stands in for the ffmpeg decode process (the manager's factory seam).</summary>
    private sealed class FakeMediaFrameSource : IMediaFrameSource
    {
        public FakeMediaFrameSource(string key) => Key = key;

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

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

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

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

        public void Emit(VideoFrame frame) => FrameAvailable?.Invoke(frame);

        public void Dispose()
        {
        }
    }
}