using System.Net;
using System.Text;
using Xunit;
using ytLive.Models;
using ytLive.Services;
using ytLive.Services.Compositor;
using ytLive.Services.Encoder;

namespace ytLive.Tests;

/// <summary>
/// The live frame producer (TASK 4 ship step 5): composites the active scene at
/// the tier's FPS and paces frames into the encoder. The integration test drives
/// the full lifecycle against fakes — real SceneCompositor + real FramePump, fake
/// IFfmpegEncoder — proving the composite frame actually reaches the encoder and
/// that stop tears the pump down cleanly. The units pin the failure edges: the
/// no-URL skip (the TASK 5 seam), re-entrancy, and encoder death.
/// </summary>
public class FramePumpTests
{
    private sealed class FakeEncoder : IFfmpegEncoder
    {
        public readonly List<VideoFrame> Frames = new();
        public readonly List<byte[]> Backings = new();
        public int StartCount;
        public int StopCount;
        public bool Disposed;
        public EncoderOptions? LastOptions;
        public Exception? StartError;
        public TaskCompletionSource FrameArrived = new(TaskCreationOptions.RunContinuationsAsynchronously);

        public event EventHandler<StreamHealth>? HealthUpdated;
        public event EventHandler<string>? ProcessFailed;

        public Task StartAsync(EncoderOptions options, CancellationToken cancellationToken = default)
        {
            StartCount++;
            LastOptions = options;
            if (StartError != null) throw StartError;
            return Task.CompletedTask;
        }

        public Task SubmitFrameAsync(VideoFrame frame, CancellationToken cancellationToken = default)
        {
            // Snapshot the bytes like the production FfmpegEncoder does (WriteAsync to
            // stdin copies before returning). Holding the reference would race the
            // pump's scratch pool legitimately reusing the buffer one tick later.
            Frames.Add(new VideoFrame(frame.Width, frame.Height, (byte[])frame.BgraPixels.Clone()));
            Backings.Add(frame.BgraPixels); // the pre-copy buffer — pool-reuse witness
            FrameArrived.TrySetResult();
            return Task.CompletedTask;
        }

        public Task StopAsync(CancellationToken cancellationToken = default)
        {
            StopCount++;
            return Task.CompletedTask;
        }

        public void Dispose() => Disposed = true;

        public void RaiseProcessFailed(string message) => ProcessFailed?.Invoke(this, message);

        public void RaiseHealth(StreamHealth health) => HealthUpdated?.Invoke(this, health);

        public int DroppedFrames { get; set; }
    }

    private static Scene BackgroundScene()
    {
        var scene = new Scene { Name = "Live" };
        scene.Elements.Add(new Source { Type = SourceType.DisplayCapture, IsBackground = true, CaptureKey = "monitor:0" });
        return scene;
    }

    private static FramePump NewPump(FakeEncoder encoder, Func<EncoderOptions?>? options = null,
        Func<Scene?>? scene = null, Func<SceneElement, VideoFrame?>? resolve = null,
        List<string>? log = null,
        Func<(VideoFrame? Frame, SocialBarPosition Position)>? socialBar = null)
    {
        return new FramePump(
            sceneProvider: scene ?? (() => BackgroundScene()),
            frameResolver: resolve ?? (_ => null),
            compositorOptions: () => new CompositorOptions
            {
                SourceRectX = 0, SourceRectY = 0, SourceRectWidth = 64, SourceRectHeight = 48,
                OutputWidth = 64, OutputHeight = 48,
            },
            encoderOptions: options ?? (() => new EncoderOptions
            {
                RtmpUrl = "rtmp://a.rtmp.youtube.com/live2/abc",
                Width = 64, Height = 48, Fps = 60,
            }),
            encoderFactory: () => encoder,
            log: log != null ? m => log.Add(m) : null,
            pacingDelay: async (_, _) => await Task.Yield(), // deterministic: no real waits
            socialBar: socialBar);
    }

    private static void AssertColor(VideoFrame frame, int x, int y, byte r, byte g, byte b)
    {
        var i = (y * frame.Width + x) * 4;
        var br = frame.BgraPixels[i + 2];
        var bg = frame.BgraPixels[i + 1];
        var bb = frame.BgraPixels[i];
        Assert.True(
            Math.Abs(br - r) <= 2 && Math.Abs(bg - g) <= 2 && Math.Abs(bb - b) <= 2,
            $"pixel ({x},{y}): expected rgb({r},{g},{b}), got rgb({br},{bg},{bb})");
    }

    private sealed class FakeHttpHandler : HttpMessageHandler
    {
        public FakeHttpHandler(string body) => Body = body;

        public string Body;
        public string? LastUri;
        public int RequestCount;

        protected override Task<HttpResponseMessage> SendAsync(
            HttpRequestMessage request, CancellationToken cancellationToken)
        {
            RequestCount++;
            LastUri = request.RequestUri?.ToString();
            return Task.FromResult(new HttpResponseMessage(HttpStatusCode.OK)
            {
                Content = new StringContent(Body, Encoding.UTF8, "application/json"),
            });
        }
    }

    /// <summary>The ONE integration test for TASK 5: the real service (hermetic
    /// HTTP) returns the reusable stream's RTMP URL, the provider seam hands it
    /// to the pump, and the pump starts the encoder with that exact URL — the
    /// chain that makes go-live actually push. The stream is reused (listed),
    /// never recreated (no POST).</summary>
    [Fact]
    public async Task ReusableStream_Url_From_Service_Feeds_Encoder_Startup()
    {
        var handler = new FakeHttpHandler(
            """
            {"items":[{"id":"S456","cdn":{"isReusable":true,"ingestionInfo":{"ingestionAddress":"rtmp://a.rtmp.youtube.com/live2","streamName":"KEY123"}}}]}
            """);
        var auth = new YouTubeAuthService("test-id", "test-secret");
        auth.SetSession(new YouTubeChannel
        {
            AccessToken = "acc-123",
            TokenExpiry = DateTime.UtcNow.AddHours(1),
        });
        var service = new YouTubeStreamService(auth, new HttpClient(handler));

        var url = (await service.GetOrCreateReusableStreamAsync())?.RtmpUrl;
        var encoder = new FakeEncoder();
        using var pump = NewPump(encoder, options: () => url == null
            ? null
            : new EncoderOptions { RtmpUrl = url, Width = 64, Height = 48, Fps = 60 });

        await pump.StartAsync();

        Assert.Equal("rtmp://a.rtmp.youtube.com/live2/KEY123", url);
        Assert.Equal(1, encoder.StartCount);
        Assert.Equal("rtmp://a.rtmp.youtube.com/live2/KEY123", encoder.LastOptions?.RtmpUrl);
        Assert.Equal(1, handler.RequestCount); // reuse path: list only, no insert
        Assert.NotNull(handler.LastUri);
        Assert.Contains("liveStreams", handler.LastUri);
        Assert.Contains("mine=true", handler.LastUri);

        await pump.StopAsync();
    }

    [Fact]
    public async Task Start_CompositesScene_FeedsEncoder_StopsCleanly()
    {
        var red = SceneCompositorTests.Solid(64, 48, 255, 0, 0);
        var encoder = new FakeEncoder();
        using var pump = NewPump(encoder,
            resolve: e => e is Source { IsBackground: true } ? red : null);

        await pump.StartAsync();
        Assert.True(pump.IsRunning);
        Assert.Equal(1, encoder.StartCount);

        await encoder.FrameArrived.Task.WaitAsync(TimeSpan.FromSeconds(5));
        Assert.NotEmpty(encoder.Frames);
        var frame = encoder.Frames[0];
        Assert.Equal(64, frame.Width);
        Assert.Equal(48, frame.Height);
        AssertColor(frame, 0, 0, 255, 0, 0); // the background really was composited in

        await pump.StopAsync();
        Assert.False(pump.IsRunning);
        Assert.Equal(1, encoder.StopCount);
        Assert.True(encoder.Disposed);
    }

    [Fact]
    public async Task Start_WithoutRtmpUrl_SkipsEncoder()
    {
        var encoder = new FakeEncoder();
        var log = new List<string>();
        using var pump = NewPump(encoder, options: () => null, log: log);

        await pump.StartAsync();

        Assert.False(pump.IsRunning);
        Assert.Equal(0, encoder.StartCount);
        Assert.Contains(log, m => m.Contains("no output configured"));

        await pump.StopAsync(); // no-op after a skipped start
        Assert.Equal(0, encoder.StopCount);
    }

    [Fact]
    public async Task Start_WhileRunning_IsNoop()
    {
        var encoder = new FakeEncoder();
        using var pump = NewPump(encoder);

        await pump.StartAsync();
        await pump.StartAsync();

        Assert.Equal(1, encoder.StartCount);
    }

    [Fact]
    public async Task Stop_WithoutStart_IsNoop()
    {
        var encoder = new FakeEncoder();
        using var pump = NewPump(encoder);

        await pump.StopAsync();

        Assert.Equal(0, encoder.StopCount);
        Assert.False(pump.IsRunning);
    }

    [Fact]
    public async Task Start_WithSocialBarSeam_PlacesBarAtTopThenBottomEdge()
    {
        var red = SceneCompositorTests.Solid(64, 48, 255, 0, 0);
        var bar = new VideoFrame(64, 8, new byte[64 * 8 * 4]);
        Array.Fill(bar.BgraPixels, (byte)255); // opaque white strip

        var encoder = new FakeEncoder();
        var position = SocialBarPosition.Top;
        using var pump = NewPump(encoder,
            resolve: e => e is Source { IsBackground: true } ? red : null,
            socialBar: () => (bar, position));

        await pump.StartAsync();
        await encoder.FrameArrived.Task.WaitAsync(TimeSpan.FromSeconds(5));
        Assert.NotEmpty(encoder.Frames);
        AssertColor(encoder.Frames[0], 0, 0, 255, 255, 255); // bar at the top edge

        // Flip to Bottom: the pump re-reads the seam each frame, so a later frame
        // lands the bar at the bottom edge (SourceRectHeight - bar height) and the
        // top corner clears back to background.
        position = SocialBarPosition.Bottom;
        VideoFrame? flipped = null;
        var deadline = DateTime.UtcNow.AddSeconds(5);
        while (DateTime.UtcNow < deadline && flipped == null)
        {
            for (var i = 1; i < encoder.Frames.Count; i++)
            {
                var f = encoder.Frames[i];
                if (f.BgraPixels[2] == 255 && f.BgraPixels[1] == 0 && f.BgraPixels[0] == 0)
                {
                    flipped = f;
                    break;
                }
            }
            if (flipped == null) await Task.Delay(10);
        }
        Assert.NotNull(flipped);
        AssertColor(flipped!, 0, 47, 255, 255, 255); // bar sits on the bottom edge

        await pump.StopAsync();
    }

    [Fact]
    public async Task Start_EncoderThrows_RaisesFailed_AndDisposes()
    {
        var encoder = new FakeEncoder { StartError = new InvalidOperationException("access denied") };
        var failed = new TaskCompletionSource<string>(TaskCreationOptions.RunContinuationsAsynchronously);
        using var pump = NewPump(encoder);
        pump.Failed += (_, m) => failed.TrySetResult(m);

        await pump.StartAsync();

        Assert.False(pump.IsRunning);
        var message = await failed.Task.WaitAsync(TimeSpan.FromSeconds(5));
        Assert.Contains("access denied", message);
        Assert.True(encoder.Disposed);
    }

    [Fact]
    public async Task ProcessDeath_StopsPump_AndRaisesFailed()
    {
        var encoder = new FakeEncoder();
        var failed = new TaskCompletionSource<string>(TaskCreationOptions.RunContinuationsAsynchronously);
        using var pump = NewPump(encoder);
        pump.Failed += (_, m) => failed.TrySetResult(m);

        await pump.StartAsync();
        encoder.RaiseProcessFailed("FFmpeg exited with code 1");

        var message = await failed.Task.WaitAsync(TimeSpan.FromSeconds(5));
        Assert.Contains("1", message);

        // The pump self-stops (fire-and-forget); poll the definitive teardown
        // marker — the encoder's disposal — rather than the IsRunning flag, which
        // StopAsync clears before the loop has fully drained.
        var deadline = DateTime.UtcNow.AddSeconds(5);
        while (!encoder.Disposed && DateTime.UtcNow < deadline)
            await Task.Delay(10);
        Assert.True(encoder.Disposed);
        Assert.False(pump.IsRunning);
    }

    [Fact]
    public async Task HealthUpdated_ForwardsEncoderHealth()
    {
        var encoder = new FakeEncoder();
        var health = new TaskCompletionSource<StreamHealth>(TaskCreationOptions.RunContinuationsAsynchronously);
        using var pump = NewPump(encoder);
        pump.HealthUpdated += (_, h) => health.TrySetResult(h);

        await pump.StartAsync();
        encoder.RaiseHealth(new StreamHealth { Status = StreamStatus.Streaming, FPS = 59.9 });

        var h = await health.Task.WaitAsync(TimeSpan.FromSeconds(5));
        Assert.Equal(StreamStatus.Streaming, h.Status);
        Assert.Equal(59.9, h.FPS, 1);
    }

    /// <summary>The ONE integration test for the take-3 starvation fix (2026-09-03):
    /// the frame interval is a DEADLINE — render cost eats into it, never piles on
    /// top (the OBS libobs video-io.c pacing pattern). The old loop slept the full
    /// interval AFTER each render, so 30 wall-seconds of 258ms renders muxed into a
    /// 2.1s 60fps time-lapse (rawvideo stamps by arrival). Here the fake render
    /// costs ≥60ms of a 200ms interval and the pacing seam records every requested
    /// wait: no request may reach the full interval (that was the bug), none may be
    /// negative, and a machine slow enough to blow every deadline is still honest
    /// (zero waits &lt; interval passes too).</summary>
    [Fact]
    public async Task Pump_Paces_To_The_Deadline_Compensating_Render_Cost()
    {
        const int fps = 5;            // 200ms interval — generous margin over the fake cost
        const int renderCostMs = 60;  // Thread.Sleep is a guaranteed lower bound
        var interval = TimeSpan.FromSeconds(1d / fps);

        var encoder = new FakeEncoder();
        var scene = BackgroundScene();
        var delays = new List<TimeSpan>();
        using var pump = new FramePump(
            sceneProvider: () => scene,
            frameResolver: _ =>
            {
                System.Threading.Thread.Sleep(renderCostMs);
                return null;
            },
            compositorOptions: () => new CompositorOptions
            {
                SourceRectX = 0, SourceRectY = 0, SourceRectWidth = 64, SourceRectHeight = 48,
                OutputWidth = 64, OutputHeight = 48,
            },
            encoderOptions: () => new EncoderOptions
            {
                RtmpUrl = "rtmp://a.rtmp.youtube.com/live2/abc",
                Width = 64, Height = 48, Fps = fps,
            },
            encoderFactory: () => encoder,
            pacingDelay: async (d, ct) =>
            {
                lock (delays) delays.Add(d);
                await Task.Delay(d, ct); // honors the request, like the real Task.Delay default
            });

        await pump.StartAsync();
        var deadline = DateTime.UtcNow.AddSeconds(10);
        while (DateTime.UtcNow < deadline)
        {
            lock (delays) if (delays.Count >= 3) break;
            await Task.Delay(10);
        }
        await pump.StopAsync();

        List<TimeSpan> got;
        lock (delays) got = delays.ToList();
        Assert.True(got.Count >= 3, $"pump paced only {got.Count} frames in 10s");
        foreach (var d in got)
        {
            Assert.True(d >= TimeSpan.Zero, $"requested wait {d} is negative");
            Assert.True(d < interval,
                $"requested wait {d} reaches the full {interval} interval — render cost must subtract from the deadline (the take-3 bug)");
        }
    }

    /// <summary>The ONE integration test for the slice-15 pacing fix (2026-09-14):
    /// a render that overruns the deadline must NOT skip the missed slots — a skip
    /// authors fast playback: ty-1726 rendered one frame per 35ms overrun into a
    /// 60fps container (163 frames for 2.93s of audio) and cut the audio tail off.
    /// OBS fills an overrun's slots by DUPLICATING the newest frame (libobs
    /// media-io/video-io.c; docs.obsproject.com/backend-design: "If the video frame
    /// queue is full, it will duplicate the last frame") so recording duration stays
    /// equal to wall duration. Here a 60fps pump renders every frame at ~35ms cost
    /// (a genuine overrun): the slice-10 keep-fresh loop authored ~1 per 35ms; the
    /// slot-filling loop must emit a frame for ~every 16.6ms of wall time.</summary>
    [Fact]
    public async Task Pump_Overrun_Renders_EmitsEverySlot_NotSkipped()
    {
        const int fps = 60;
        var encoder = new FakeEncoder();
        using var pump = NewPump(encoder, resolve: _ =>
        {
            System.Threading.Thread.Sleep(35);
            return null;
        });

        await pump.StartAsync();
        await Task.Delay(7000); // ~420 slots of wall time
        await pump.StopAsync();

        // Slot-faithful: ~1 frame per 16.6ms -> ~415 in the window. Skipping (the
        // slice-10 behavior): ~1 per 35ms -> ~200. 0.65 * fps * (elapsed seconds)
        // is a middle line a skipped pump can never cross, a filling one only fails
        // on a pathological run.
        Assert.True(encoder.Frames.Count >= (int)(7.0 * fps * 0.65),
            $"pump emitted {encoder.Frames.Count} frames in ~7s wall at {fps}fps — "
            + $"{7.0 / encoder.Frames.Count * fps:F1}x playback — an overrun must "
            + "DUPLICATE the newest frame per missed slot (OBS), not skip it");
    }

    /// <summary>The ONE integration test for the take-4 scratch pool: the pump recycles
    /// its master buffers across frames (the 8.3MB-per-tick LOH churn that cost GC
    /// stalls inside "render") while EVERY frame's content stays correct — stale bytes
    /// from an earlier tick would show as a wrong color. The backdrop alternates
    /// red/blue per tick (submit snapshots pin the color), and a repeated backing-array
    /// identity proves the pool actually recycles (an inert pool keeps the pixel
    /// assertions green while leaving the churn in place).</summary>
    [Fact]
    public async Task Pump_Pools_ScratchBuffers_Across_Frames_Without_Stale_Pixels()
    {
        var red = SceneCompositorTests.Solid(64, 48, 255, 0, 0);
        var blue = SceneCompositorTests.Solid(64, 48, 0, 0, 255);
        var flip = 0;
        var encoder = new FakeEncoder();
        using var pump = NewPump(encoder, resolve: _ => flip++ % 2 == 0 ? red : blue);

        await pump.StartAsync();
        var deadline = DateTime.UtcNow.AddSeconds(10);
        while (DateTime.UtcNow < deadline && encoder.Frames.Count < 6)
            await Task.Delay(10);
        await pump.StopAsync();

        Assert.True(encoder.Frames.Count >= 6, $"only {encoder.Frames.Count} frames produced");
        for (var i = 0; i < encoder.Frames.Count; i++)
        {
            if (i % 2 == 0) AssertColor(encoder.Frames[i], 0, 0, 255, 0, 0);
            else AssertColor(encoder.Frames[i], 0, 0, 0, 0, 255);
        }
        Assert.True(encoder.Backings.Distinct().Count() < encoder.Backings.Count,
            "every frame rode a fresh buffer — the scratch pool is inert");
    }

    /// <summary>One integration test for the take-8 off-UI fix: the pump loop must NOT
    /// run on the starting thread's SynchronizationContext (StartAsync fires from a UI
    /// command handler; the old loop inherited it, so every frame competed with the
    /// live preview for the dispatcher — the "wait 10ms after a 22ms render" that the
    /// quantum stats exposed). An inline-pumping sync context makes the OLD code run
    /// its resolver on the starting thread; the Task.Run'd loop must never do so.</summary>
    [Fact]
    public async Task Pump_Produces_OffTheStartingContext()
    {
        var startThread = Environment.CurrentManagedThreadId;
        var resolverThreads = new List<int>();
        var firstFrame = new TaskCompletionSource(TaskCreationOptions.RunContinuationsAsynchronously);
        var encoder = new FakeEncoder();
        using var pump = NewPump(encoder, resolve: _ =>
        {
            lock (resolverThreads) resolverThreads.Add(Environment.CurrentManagedThreadId);
            firstFrame.TrySetResult();
            return null;
        });

        var prev = SynchronizationContext.Current;
        SynchronizationContext.SetSynchronizationContext(new InlineSyncContext());
        try
        {
            await pump.StartAsync();
            await firstFrame.Task.WaitAsync(TimeSpan.FromSeconds(5));
        }
        finally
        {
            SynchronizationContext.SetSynchronizationContext(prev);
            await pump.StopAsync();
        }

        Assert.NotEmpty(resolverThreads);
        Assert.All(resolverThreads, id => Assert.True(id != startThread,
            $"resolver ran on the starting thread ({startThread}) — the loop is back on the caller context"));
    }

    private sealed class InlineSyncContext : SynchronizationContext
    {
        public override void Post(SendOrPostCallback d, object? state) => d(state);
        public override void Send(SendOrPostCallback d, object? state) => d(state);
        public override SynchronizationContext CreateCopy() => this;
    }
}