FFMpegCore/FFMpegCore/FFMpeg/Arguments/PanArgument.cs

namespace FFMpegCore.Arguments;

/// <summary>
///     Mix channels with specific gain levels.
/// </summary>
public class PanArgument : IAudioFilterArgument
{
    private readonly string[] _outputDefinitions;
    public readonly string ChannelLayout;

    /// <summary>
    ///     Mix channels with specific gain levels <see href="https://ffmpeg.org/ffmpeg-filters.html#toc-pan-1" />
    /// </summary>
    /// <param name="channelLayout">
    ///     Represent the output channel layout. Like "stereo", "mono", "2.1", "5.1"
    /// </param>
    /// <param name="outputDefinitions">
    ///     Output channel specification, of the form: "out_name=[gain*]in_name[(+-)[gain*]in_name...]"
    /// </param>
    public PanArgument(string channelLayout, params string[] outputDefinitions)
    {
        if (string.IsNullOrWhiteSpace(channelLayout))
        {
            throw new ArgumentException("The channel layout must be set", nameof(channelLayout));
        }

        ChannelLayout = channelLayout;

        _outputDefinitions = outputDefinitions;
    }

    /// <summary>
    ///     Mix channels with specific gain levels <see href="https://ffmpeg.org/ffmpeg-filters.html#toc-pan-1" />
    /// </summary>
    /// <param name="channels">Number of channels in output file</param>
    /// <param name="outputDefinitions">
    ///     Output channel specification, of the form: "out_name=[gain*]in_name[(+-)[gain*]in_name...]"
    /// </param>
    public PanArgument(int channels, params string[] outputDefinitions)
    {
        if (channels <= 0)
        {
            throw new ArgumentOutOfRangeException(nameof(channels));
        }

        if (outputDefinitions.Length > channels)
        {
            throw new ArgumentException("The number of output definitions must be equal or lower than number of channels", nameof(outputDefinitions));
        }

        ChannelLayout = $"{channels}c";

        _outputDefinitions = outputDefinitions;
    }

    public string Key { get; } = "pan";

    public string Value =>
        string.Join("|", Enumerable.Empty<string>().Append(ChannelLayout).Concat(_outputDefinitions));
}