using FFmpeg.AutoGen;
using System;
using System.Drawing;
using System.Runtime.InteropServices;

namespace EC.FFmpegAutoGen
{
    public sealed unsafe class VideoConverter : IDisposable
    {
        private readonly SwsContext* _pConvertContext;

        public VideoConverter(Size sourceSize, AVPixelFormat sourcePixelFormat,
            Size destinationSize, AVPixelFormat destinationPixelFormat)
        {
            _pConvertContext = ffmpeg.sws_getContext(sourceSize.Width,
                sourceSize.Height,
                sourcePixelFormat,
                destinationSize.Width,
                destinationSize.Height,
                destinationPixelFormat,
                ffmpeg.SWS_FAST_BILINEAR,
                null,
                null,
                null);
            if (_pConvertContext == null)
                throw new ApplicationException("Could not initialize the conversion context.");

            var convertedFrameBufferSize = ffmpeg.av_image_get_buffer_size(destinationPixelFormat,
                destinationSize.Width,
                destinationSize.Height,
                1);
            var convertedFrameBufferPtr = Marshal.AllocHGlobal(convertedFrameBufferSize);
            var dstData = new byte_ptrArray4();
            var dstLinesize = new int_array4();

            ffmpeg.av_image_fill_arrays(ref dstData,
                ref dstLinesize,
                (byte*) convertedFrameBufferPtr,
                destinationPixelFormat,
                destinationSize.Width,
                destinationSize.Height,
                1);
        }

        public void Dispose()
        {
        }

        public AVFrame Convert(AVFrame sourceFrame)
        {
            var dstData = new byte_ptrArray4();
            var dstLinesize = new int_array4();

            ffmpeg.sws_scale(_pConvertContext,
                sourceFrame.data,
                sourceFrame.linesize,
                0,
                sourceFrame.height,
                dstData,
                dstLinesize);

            return new AVFrame();
        }
    }
}