namespace ytLive.Services.Encoder;

/// <summary>
/// Builds the FFmpeg command line for a live RTMP push (TASK 4 ship step 3):
/// raw BGRA frames via stdin (paced by the frame pump — the pump holds a strict
/// CFR cadence, so <c>-re</c> would only add a second, fighting pacer), real
/// audio via the named pipe
/// (TASK 9 — the mixer streams f32le at 48 kHz stereo into <c>\\.\pipe\&lt;name&gt;</c>;
/// WASAPI loopback + the mic ride the pipe instead of the old anullsrc silence),
/// H.264 + AAC encoding, FLV muxing to the ingestion URL. Pure — the encoder
/// just starts <c>ffmpeg.exe [Build(...)]</c>.
/// </summary>
public static class FfmpegArgs
{
    public static IReadOnlyList<string> Build(EncoderOptions options, string videoEncoder)
    {
        var args = new List<string>
        {
            "-hide_banner", "-loglevel", "info",
            "-stats", "-stats_period", "0.5",
            "-f", "rawvideo", "-pix_fmt", "bgra",
            "-video_size", $"{options.Width}x{options.Height}",
            "-framerate", options.Fps.ToString(),
            "-i", "pipe:0",
            "-f", "f32le", "-ar", options.AudioSampleRate.ToString(),
            "-ac", options.AudioChannels.ToString(),
            "-i", $@"\\.\pipe\{options.AudioPipeName}",
        };

        // Each output is a self-contained block: its own -map, codec options,
        // format, and destination. Record+stream encodes the video twice off the
        // one raw input pipe (cheap on NVENC).
        if (options.StreamEnabled)
        {
            AddVideoTags(args, options, videoEncoder);
            args.AddRange(["-c:a", "aac", "-b:a", "128k",
                "-ar", options.AudioSampleRate.ToString(), "-ac", options.AudioChannels.ToString()]);
            args.AddRange(["-f", "flv", options.RtmpUrl]);
        }

        if (options.RecordEnabled)
        {
            AddVideoTags(args, options, videoEncoder);
            args.AddRange(["-c:a", "aac",
                "-ar", options.AudioSampleRate.ToString(), "-ac", options.AudioChannels.ToString()]);
            args.AddRange(["-f", "mp4", options.RecordPath!]);
        }

        return args;
    }

    private static void AddVideoTags(List<string> args, EncoderOptions options, string videoEncoder)
    {
        var gop = options.GopSize;
        args.AddRange(["-map", "0:v", "-map", "1:a"]);
        args.AddRange(["-c:v", videoEncoder]);
        args.AddRange(["-b:v", $"{options.BitrateKbps}k", "-maxrate", $"{options.BitrateKbps}k",
            "-bufsize", $"{options.BitrateKbps * 2}k"]);
        args.AddRange(["-g", gop.ToString(), "-keyint_min", gop.ToString(),
            "-sc_threshold", "0", "-bf", "0", "-pix_fmt", "yuv420p"]);
    }
}