using System.Globalization;
using ErsatzTV.FFmpeg.Environment;

namespace ErsatzTV.FFmpeg.InputOption;

public class ReadrateInputOption(double readRate, Option<int> initialBurstSeconds, Option<double> catchupReadRate)
    : IInputOption
{
    public ReadrateInputOption(double readRate)
        : this(readRate, Option<int>.None, Option<double>.None)
    {
    }

    public EnvironmentVariable[] EnvironmentVariables => [];

    public string[] GlobalOptions => [];

    public string[] InputOptions(InputFile inputFile)
    {
        var result = new List<string>
        {
            "-readrate",
            readRate.ToString("0.0####", CultureInfo.InvariantCulture)
        };

        // burst-read this much input before the readrate throttle kicks in, so a cold start doesn't
        // have to wait ~realtime for the first segment to be written (ersatztv#350)
        foreach (int burst in initialBurstSeconds)
        {
            result.Add("-readrate_initial_burst");
            result.Add(burst.ToString(CultureInfo.InvariantCulture));
        }

        // -readrate paces the WHOLE input off its furthest-behind stream, so one sparse stream
        // (an embedded PGS/DVD bitmap subtitle feeding the overlay) drags the video down with it
        // and output collapses to ~0.53x realtime. catchup lets a lagging input read faster until
        // it is level again; it is a ceiling that only applies WHILE behind, never a target, so
        // caught-up input still paces at readRate and cannot race ahead (ersatztv#726)
        foreach (double catchup in catchupReadRate)
        {
            result.Add("-readrate_catchup");
            result.Add(catchup.ToString("0.0####", CultureInfo.InvariantCulture));
        }

        return result.ToArray();
    }

    public string[] FilterOptions => [];
    public string[] OutputOptions => [];
    public FrameState NextState(FrameState currentState) => currentState with { Realtime = true };

    public bool AppliesTo(AudioInputFile audioInputFile) => audioInputFile is not NullAudioInputFile;

    // don't use realtime input for a still image
    public bool AppliesTo(VideoInputFile videoInputFile) => videoInputFile.VideoStreams.All(s => !s.StillImage);

    public bool AppliesTo(ConcatInputFile concatInputFile) => true;

    public bool AppliesTo(GraphicsEngineInput graphicsEngineInput) => false;
}