using System.Diagnostics;
using System.IO;
using System.Text;
using EmbyToolbox.Models;

namespace EmbyToolbox.Services;

public sealed class TrackExtractionService
{
    private readonly FfprobeService _ffprobe;

    public TrackExtractionService(FfprobeService ffprobe)
    {
        _ffprobe = ffprobe;
    }

    public async Task<MediaAnalysisResult?> AnalyzeMediaAsync(string filePath, LoggingService logging, CancellationToken ct)
    {
        var probe = await _ffprobe.AnalyzeAsync(filePath, ct).ConfigureAwait(false);
        if (!probe.IsSuccess)
        {
            logging.Error($"ffprobe: {probe.Error}", "tracks.extract");
            return null;
        }

        var parsed = MediaAnalysisParser.TryParse(probe.Json);
        if (parsed is null)
        {
            logging.Error($"ffprobe JSON не распознан: {Path.GetFileName(filePath)}", "tracks.extract");
        }

        return parsed;
    }

    /// <summary>Создаёт <c>[destination]\extract\{audio|subtitles|attachments}</c>, возвращает путь к <c>extract</c>.</summary>
    public string? PrepareExtractLayout(string destinationRootFolder) =>
        TrackExtractOutputPaths.TryPrepareExtractDirectories(destinationRootFolder);

    /// <returns>Успех, stderr ffmpeg.</returns>
    public async Task<(bool Success, string StdErr)> RunExtractProcessAsync(IReadOnlyList<string> ffmpegArgumentList, CancellationToken ct)
    {
        var exe = ResolveFfmpegPath();
        if (!File.Exists(exe))
        {
            return (false, $"ffmpeg не найден: {exe}");
        }

        var start = new ProcessStartInfo
        {
            FileName = exe,
            RedirectStandardOutput = true,
            RedirectStandardError = true,
            UseShellExecute = false,
            CreateNoWindow = true,
            StandardOutputEncoding = Encoding.UTF8,
            StandardErrorEncoding = Encoding.UTF8,
        };

        foreach (var a in ffmpegArgumentList)
        {
            start.ArgumentList.Add(a);
        }

        using var p = new Process { StartInfo = start };
        p.Start();
        using var reg = ct.Register(static state =>
        {
            try
            {
                if (state is not Process proc || proc.HasExited)
                {
                    return;
                }

                proc.Kill(entireProcessTree: true);
            }
            catch
            {
                // ignore
            }
        }, p, useSynchronizationContext: false);

        var stderrTask = p.StandardError.ReadToEndAsync(ct);
        var stdoutTask = p.StandardOutput.ReadToEndAsync(ct);
        try
        {
            await p.WaitForExitAsync(ct).ConfigureAwait(false);
        }
        catch (OperationCanceledException) when (ct.IsCancellationRequested)
        {
            try
            {
                await Task.WhenAll(stderrTask, stdoutTask).ConfigureAwait(false);
            }
            catch
            {
                // ignore
            }

            throw;
        }

        await Task.WhenAll(stderrTask, stdoutTask).ConfigureAwait(false);
        var err = stderrTask.Result;
        var ok = p.ExitCode == 0 && !ct.IsCancellationRequested;
        return (ok, err.Trim());
    }

    private static string ResolveFfmpegPath() => Path.Combine(AppContext.BaseDirectory, "Tools", "ffmpeg.exe");
}