BakaMusicPlayer/Bmp.Core/FFMpeg/CsCorePorts/FFMpegWrap/FfmpegUtils.cs

using System.ComponentModel;
using System.Runtime.InteropServices;
using Bmp.Core.FFMpeg.CsCorePorts.FFMpegWrap.Interops;

namespace Bmp.Core.FFMpeg.CsCorePorts.FFMpegWrap;

/// <summary>
/// Contains some utilities for working with ffmpeg.
/// </summary>
public static class FfmpegUtils
{
    // ReSharper disable once PrivateFieldCanBeConvertedToLocalVariable
    private static readonly FfmpegCalls.LogCallback LogCallback;
    private static readonly FfmpegCalls.LogCallback DefaultLogCallback;
    private static readonly object LockObj = new object();

    /// <summary>
    /// Occurs when a ffmpeg log entry was received.
    /// </summary>
    public static event EventHandler<FfmpegLogReceivedEventArgs> FfmpegLogReceived;

    /// <summary>
    /// Occurs when the location of the native FFmpeg binaries has get resolved.
    /// Note: This is currently only available for Windows Platforms.
    /// </summary>
    public static event EventHandler<ResolveFfmpegAssemblyLocationEventArgs> ResolveFfmpegAssemblyLocation;

    static unsafe FfmpegUtils()
    {
        LogCallback = OnLogMessage;
        DefaultLogCallback = FfmpegCalls.GetDefaultLogCallback();
        FfmpegCalls.SetLogCallback(LogCallback);
    }

    /// <summary>
    /// Gets the output formats.
    /// </summary>
    /// <returns>All supported output formats.</returns>
    public static IEnumerable<Format> GetOutputFormats()
    {
        var outputFormats = FfmpegCalls.GetOutputFormats();
        return outputFormats.Select(format => new Format(format));
    }

    /// <summary>
    /// Gets the input formats.
    /// </summary>
    /// <returns>All supported input formats.</returns>
    public static IEnumerable<Format> GetInputFormats()
    {
        var inputFormats = FfmpegCalls.GetInputFormats();
        return inputFormats.Select(format => new Format(format));
    }

    /// <summary>
    /// Gets or sets the log level.
    /// </summary>
    /// <value>
    /// The log level.
    /// </value>
    /// <exception cref="InvalidEnumArgumentException">value</exception>
    public static LogLevel LogLevel
    {
        get { return FfmpegCalls.GetLogLevel(); }
        set
        {
            if ((int)value < (int)LogLevel.Quit || (int)value > (int)LogLevel.Debug || (int)value % 8 != 0)
                throw new InvalidEnumArgumentException("value", (int)value, typeof(LogLevel));

            FfmpegCalls.SetLogLevel(value);
        }
    }

    /// <summary>
    /// Gets or sets a value indicating whether log entries should be passed to the default ffmpeg logger.
    /// </summary>
    /// <value>
    ///   <c>true</c> if log messages should be passed to the default ffmpeg logger; otherwise, <c>false</c>.
    /// </value>
    public static bool LogToDefaultLogger { get; set; }

    private static unsafe void OnLogMessage(void* ptr, int level, byte* fmt, nint vl)
    {
        lock (LockObj)
        {
            if (level >= 0)
            {
                level &= 0xFF;
            }

            if (level > (int)LogLevel)
                return;

            if (LogToDefaultLogger)
            {
                DefaultLogCallback(ptr, level, fmt, vl);
            }

            var eventHandler = FfmpegLogReceived;
            if (eventHandler != null)
            {
                AVClass? avClass = null;
                AVClass? parentLogContext = null;
                AVClass** ppParent = default;
                if (ptr != null)
                {
                    avClass = **(AVClass**)ptr;
                    if (avClass.Value.parent_log_context_offset != 0)
                    {
                        ppParent = *(AVClass***)((byte*)ptr + avClass.Value.parent_log_context_offset);
                        if (ppParent != null && *ppParent != null)
                        {
                            parentLogContext = **ppParent;
                        }
                    }
                }


                var printPrefix = 1;
                var line = FfmpegCalls.FormatLine(ptr, level, Marshal.PtrToStringAnsi((nint)fmt), vl, ref printPrefix);

                eventHandler(null,
                    new FfmpegLogReceivedEventArgs(avClass, parentLogContext, (LogLevel)level, line, ptr, ppParent));
            }
        }
    }

    internal static DirectoryInfo FindFfmpegDirectory(PlatformID platform)
    {
        var resolveEvent = ResolveFfmpegAssemblyLocation;
        var eventArgs = new ResolveFfmpegAssemblyLocationEventArgs(platform);
        if (resolveEvent != null)
            resolveEvent(null, eventArgs);

        return eventArgs.FfmpegDirectory;
    }
}