FFmpeg.cs

using System;
using System.Globalization;
using System.IO;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading;
using System.Threading.Tasks;
using CliWrap;
using CliWrap.Exceptions;
using YoutubeExplode.Converter.Utils.Extensions;

namespace YoutubeExplode.Converter;

// Ideally this should use named pipes and stream through stdout.
// However, named pipes aren't well supported on non-Windows OS and
// stdout streaming only works with some specific formats.
internal partial class FFmpeg(string filePath)
{
    public async ValueTask ExecuteAsync(
        string arguments,
        IProgress<double>? progress,
        CancellationToken cancellationToken = default
    )
    {
        var stdErrBuffer = new StringBuilder();

        var stdErrPipe = PipeTarget.Merge(
            // Collect error output in case of failure
            PipeTarget.ToStringBuilder(stdErrBuffer),
            // Collect progress output if requested
            progress?.Pipe(CreateProgressRouter) ?? PipeTarget.Null
        );

        try
        {
            await Cli.Wrap(filePath)
                .WithArguments(arguments)
                .WithStandardErrorPipe(stdErrPipe)
                .ExecuteAsync(cancellationToken);
        }
        catch (CommandExecutionException ex)
        {
            throw new InvalidOperationException(
                $"""
                FFmpeg command-line tool failed with an error.

                Standard error:
                {stdErrBuffer}
                """,
                ex
            );
        }
    }
}

internal partial class FFmpeg
{
    public static string GetFilePath() =>
        // Try to find FFmpeg in the probe directory
        Directory
            .EnumerateFiles(AppContext.BaseDirectory ?? Directory.GetCurrentDirectory())
            .FirstOrDefault(f =>
                string.Equals(
                    Path.GetFileNameWithoutExtension(f),
                    "ffmpeg",
                    StringComparison.OrdinalIgnoreCase
                )
            )
        // Otherwise fallback to just "ffmpeg" and hope it's on the PATH
        ?? "ffmpeg";

    private static PipeTarget CreateProgressRouter(IProgress<double> progress)
    {
        var totalDuration = default(TimeSpan?);

        return PipeTarget.ToDelegate(line =>
        {
            // Extract total stream duration
            if (totalDuration is null)
            {
                // Need to extract all components separately because TimeSpan cannot directly
                // parse a time string that is greater than 24 hours.
                var totalDurationMatch = Regex.Match(line, @"Duration:\s(\d+):(\d+):(\d+\.\d+)");
                if (totalDurationMatch.Success)
                {
                    var hours = int.Parse(
                        totalDurationMatch.Groups[1].Value,
                        CultureInfo.InvariantCulture
                    );
                    var minutes = int.Parse(
                        totalDurationMatch.Groups[2].Value,
                        CultureInfo.InvariantCulture
                    );
                    var seconds = double.Parse(
                        totalDurationMatch.Groups[3].Value,
                        CultureInfo.InvariantCulture
                    );

                    totalDuration =
                        TimeSpan.FromHours(hours)
                        + TimeSpan.FromMinutes(minutes)
                        + TimeSpan.FromSeconds(seconds);
                }
            }

            if (totalDuration is null || totalDuration == TimeSpan.Zero)
                return;

            // Extract processed stream duration
            var processedDurationMatch = Regex.Match(line, @"time=(\d+):(\d+):(\d+\.\d+)");
            if (processedDurationMatch.Success)
            {
                var hours = int.Parse(
                    processedDurationMatch.Groups[1].Value,
                    CultureInfo.InvariantCulture
                );
                var minutes = int.Parse(
                    processedDurationMatch.Groups[2].Value,
                    CultureInfo.InvariantCulture
                );
                var seconds = double.Parse(
                    processedDurationMatch.Groups[3].Value,
                    CultureInfo.InvariantCulture
                );

                var processedDuration =
                    TimeSpan.FromHours(hours)
                    + TimeSpan.FromMinutes(minutes)
                    + TimeSpan.FromSeconds(seconds);

                progress.Report(
                    (
                        processedDuration.TotalMilliseconds / totalDuration.Value.TotalMilliseconds
                    ).Clamp(0, 1)
                );
            }
        });
    }
}