using System.Diagnostics;
using System.IO;
using Xunit;
using ytLive.Services;
using ytLive.Services.Encoder;

namespace ytLive.Tests;

/// <summary>
/// TASK 21 (slice 2): the ffprobe frame-rate parser is pure (synthetic text, no
/// probe); the one integration test drives the real <see cref="FfmpegFrameRateProbe"/>
/// against a fake locator + fake probe subprocess end to end.
/// </summary>
public class FfmpegFrameRateParserTests
{
    // ─── Pure parser (unit) ───

    [Fact]
    public void Parse_AvgFrameRate_Rational()
    {
        var out0 = "codec_name=h264\navg_frame_rate=30/1\nr_frame_rate=30/1\n";
        Assert.Equal(30.0, FfmpegFrameRateParser.ParseFrameRate(out0));
    }

    [Fact]
    public void Parse_AvgFrameRate_29_97()
    {
        var out0 = "avg_frame_rate=30000/1001\nr_frame_rate=30/1\n";
        Assert.Equal(30000.0 / 1001.0, FfmpegFrameRateParser.ParseFrameRate(out0)!.Value, 3);
    }

    [Fact]
    public void Parse_PrefersAvgOverRFrame()
    {
        var out0 = "avg_frame_rate=25/1\nr_frame_rate=30000/1001\n";
        Assert.Equal(25.0, FfmpegFrameRateParser.ParseFrameRate(out0));
    }

    [Fact]
    public void Parse_FallsBackToRFrame_WhenAvgUnknown()
    {
        var out0 = "avg_frame_rate=0/0\nr_frame_rate=50/1\n";
        Assert.Equal(50.0, FfmpegFrameRateParser.ParseFrameRate(out0));
    }

    [Fact]
    public void Parse_IntegerValue_HasUnitDenominator()
    {
        var out0 = "avg_frame_rate=60\n";
        Assert.Equal(60.0, FfmpegFrameRateParser.ParseFrameRate(out0));
    }

    [Theory]
    [InlineData("avg_frame_rate=0/0\nr_frame_rate=0/0\n")]
    [InlineData("")]
    [InlineData("codec_name=h264\n")]
    public void Parse_Unknown_ReturnsNull(string output)
    {
        Assert.Null(FfmpegFrameRateParser.ParseFrameRate(output));
    }

    // ─── The one integration test: probe against fake locator + fake subprocess ───

    [Fact]
    public async Task Probe_ReturnsParsedFps_FromFakeSubprocess()
    {
        var toolsDir = CreateTempDir();
        try
        {
            // ffprobe.exe must exist next to the located ffmpeg for the sibling
            // derivation to return a usable path.
            var probeExe = Path.Combine(toolsDir, "ffprobe.exe");
            File.WriteAllText(probeExe, "ffprobe");

            var fakeOutput = "codec_name=h264\navg_frame_rate=24000/1001\nr_frame_rate=24000/1001\n";
            var probe = new FfmpegFrameRateProbe(
                new FakeLocator(toolsDir),
                () => new FakeProbeProcess(System.Text.Encoding.UTF8.GetBytes(fakeOutput)));

            var fps = await probe.ProbeAsync(@"C:\videos\clip.mp4");
            Assert.Equal(24000.0 / 1001.0, fps!.Value, 3);
        }
        finally
        {
            Directory.Delete(toolsDir, recursive: true);
        }
    }

    private static string CreateTempDir()
    {
        var dir = Path.Combine(Path.GetTempPath(), "ytllive-tests-" + Guid.NewGuid().ToString("N"));
        Directory.CreateDirectory(dir);
        return dir;
    }

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

    private sealed class FakeProbeProcess : IDecodeProcess
    {
        private readonly MemoryStream _stream;
        public FakeProbeProcess(byte[] bytes) => _stream = new MemoryStream(bytes);
        public void Start(ProcessStartInfo startInfo) { }
        public Stream StandardOutput => _stream;
        public bool HasExited => _stream.Position >= _stream.Length;
        public int ExitCode => 0;
        public void Kill() { }
        public Task WaitForExitAsync(CancellationToken ct = default) => Task.CompletedTask;
        public void Dispose() => _stream.Dispose();
    }
}