MilkyShots/Lactose/Jobs/FfmpegRunner.cs

using System.Diagnostics;
using Microsoft.Extensions.Logging;

namespace Lactose.Jobs;

/// <summary>
/// Runs ffmpeg/ffprobe invocations for media conversion jobs.
/// </summary>
internal static class FfmpegRunner {
    /// <summary>
    /// Executes ffmpeg with the given arguments, capturing output for logging.
    /// </summary>
    /// <param name="ffmpegPath">Path to the ffmpeg executable.</param>
    /// <param name="arguments">Command-line arguments to pass to ffmpeg.</param>
    /// <param name="logger">Logger for ffmpeg output.</param>
    /// <param name="token">Cancellation token; the process is killed if cancelled.</param>
    /// <exception cref="InvalidOperationException">Thrown when ffmpeg exits with a non-zero exit code.</exception>
    internal static async Task RunAsync(string ffmpegPath, string arguments, ILogger logger, CancellationToken token) {
        var startInfo = new ProcessStartInfo {
            FileName               = ffmpegPath,
            Arguments              = arguments,
            RedirectStandardOutput = true,
            RedirectStandardError  = true,
            UseShellExecute        = false,
            CreateNoWindow         = true
        };

        using var process = new Process { StartInfo = startInfo };
        process.Start();

        var stdoutTask = process.StandardOutput.ReadToEndAsync();
        var stderrTask = process.StandardError.ReadToEndAsync();

        try {
            await process.WaitForExitAsync(token);
        } catch (OperationCanceledException) {
            try { process.Kill(entireProcessTree: true); } catch { /* already exited */ }
            throw;
        }

        var stdout = await stdoutTask;
        var stderr = await stderrTask;

        if (!string.IsNullOrEmpty(stdout))
            logger.LogTrace("ffmpeg stdout: {Output}", stdout);
        if (!string.IsNullOrEmpty(stderr))
            logger.LogTrace("ffmpeg stderr: {Output}", stderr);

        if (process.ExitCode != 0) {
            logger.LogError("ffmpeg exited with code {Code}. Stderr: {Error}", process.ExitCode, stderr);
            throw new InvalidOperationException($"ffmpeg exited with code {process.ExitCode}.");
        }
    }
}