using Bmp.Core.FFMpeg.CsCorePorts.FFMpegWrap.Interops;
 
namespace Bmp.Core.FFMpeg.CsCorePorts.FFMpegWrap;

internal sealed class AvioContext : IDisposable
{
    // ReSharper disable once PrivateFieldCanBeConvertedToLocalVariable
    private readonly FfmpegCalls.AvioReadData _readDataCallback;
    private readonly FfmpegCalls.AvioSeek _seekCallback;
    private readonly FfmpegCalls.AvioWriteData _writeDataCallback;
    private unsafe AVIOContext* _context;
    private AvioBuffer _buffer;
    // ReSharper restore PrivateFieldCanBeConvertedToLocalVariable

    public unsafe nint ContextPtr
    {
        get { return (nint)_context; }
    }

    public unsafe AVIOContext Context
    {
        get
        {
            if (_context == null)
                return default;
            return *_context;
        }
    }


    public AvioContext(
        FfmpegCalls.AvioReadData readDataCallback,
        FfmpegCalls.AvioSeek seekCallback)
        : this(readDataCallback, seekCallback, null)
    {
    }

    public unsafe AvioContext(
        FfmpegCalls.AvioReadData readDataCallback,
        FfmpegCalls.AvioSeek seekCallback,
        FfmpegCalls.AvioWriteData writeDataCallback)
    {
        _readDataCallback = readDataCallback;
        _seekCallback = seekCallback;
        _writeDataCallback = writeDataCallback;

        //make sure that the buffer won't be disposed
        //the buffer may change. we always have to free _context->buffer
        _buffer = new AvioBuffer { SuppressAvFree = true };
        _context = FfmpegCalls.AvioAllocContext(_buffer, _writeDataCallback != null, nint.Zero,
            _readDataCallback, _writeDataCallback, _seekCallback);
    }

    public unsafe void Dispose()
    {
        GC.SuppressFinalize(this);
        if (_context != null)
        {
            //free the allocated buffer
            //note: the internal buffer could have changed, and be != _buffer
            FfmpegCalls.AvFree((nint)_context->buffer);

            //free the context itself
            FfmpegCalls.AvFree((nint)_context);
            _context = null;
        }
    }

    ~AvioContext()
    {
        Dispose();
    }
}