#include <stdio.h>
#include <stdlib.h>
#include <libavformat/avformat.h>
#include <libavcodec/avcodec.h>
#include <libavutil/avutil.h>
#include <libavutil/mem.h>
#include <libswscale/swscale.h>

int main()
{
    AVFormatContext *avfc;
    AVCodecContext *codecctx;
    struct SwsContext *swsctx;
    AVCodec *codec;
    AVFrame *pFrame;
    AVFrame *pFrameRGB;
    uint8_t *picbuf;
    int numbytes;
    int res = 0;
    int frameFinished = 0;
    int gotpic;
    AVPacket pkt;
    int i = 0;

    printf("Hello world!\n");

    char fname[100] = "out.avi";

    av_log_set_level(AV_LOG_DEBUG);
    // Register
    av_register_all();
    // Alloc formatcontext and open input file
    avfc = avformat_alloc_context();
    res = avformat_open_input(&avfc, fname, NULL, NULL);
    printf("%i\n", res);
    // Populate streams (not always necessary
    res = avformat_find_stream_info(avfc, NULL);
    printf("%i\n", res);
    // Open codec described the first stream (should search for first video stream though)
    codecctx = avfc->streams[0]->codec;
    codec = avcodec_find_decoder(codecctx->codec_id);
    res = avcodec_open2(codecctx, codec, NULL);
    printf("%i\n", res);

    av_dump_format(avfc, 0, fname, 0);
    // Allocate frame and get next frame
    pFrame = avcodec_alloc_frame();
    pFrameRGB = avcodec_alloc_frame();
    pFrameRGB->format = PIX_FMT_RGBA;
    pFrameRGB->width = 512;
    pFrameRGB->height = 512;
    numbytes = avpicture_get_size(pFrameRGB->format, pFrameRGB->width, pFrameRGB->height);
    picbuf = av_malloc(numbytes*sizeof(uint8_t));
    avpicture_fill((AVPicture *) pFrameRGB, picbuf, pFrameRGB->format, pFrameRGB->width, pFrameRGB->height);

    av_init_packet(&pkt);

    int framenum = 0;
    while (av_read_frame(avfc, &pkt)>= 0) {
        pkt.flags = pkt.flags&AV_PKT_FLAG_KEY;
        avcodec_decode_video2(codecctx, pFrame, &gotpic, &pkt);
        printf("%d\n", gotpic);
        if (gotpic) {
            printf("Got frame.\n");
            swsctx = sws_getContext(pFrame->width, pFrame->height, pFrame->format, pFrameRGB->width, pFrameRGB->height, pFrameRGB->format, SWS_BICUBIC, NULL, NULL, NULL);
            sws_scale(swsctx, (const uint8_t * const*) pFrame->data, pFrame->linesize, 0, pFrame->height, pFrameRGB->data, pFrameRGB->linesize);

            AVCodec *encodec = avcodec_find_encoder(CODEC_ID_PNG);
            AVCodecContext *avencctx = avcodec_alloc_context3(encodec);
            avcodec_get_context_defaults3(avencctx, encodec);
            avencctx->pix_fmt = PIX_FMT_RGBA;
            avencctx->width = pFrameRGB->width;
            avencctx->height = pFrameRGB->height;
            int resenc = avcodec_open2(avencctx, avcodec_find_encoder(CODEC_ID_PNG), NULL);
            AVPacket avpenc;
            avpenc.data = NULL;
            int gotpkt = 0;
            if (avcodec_encode_video2(avencctx, &avpenc, pFrameRGB, &gotpkt) != 0) printf("Failed to encode.\n");
            else {FILE *file = NULL;
                char fname[10];
                sprintf(fname, "%04d.raw", framenum);
                file = fopen(fname, "wb");
                if (file != NULL) {
                    fwrite(avpenc.data, avpenc.size, 1, file);
                } else printf("Can't access file.\n");
                fclose(file);
            }
            framenum++;
        }
        av_free_packet(&pkt);

    }

    return 0;
}