package codec

import (
	/*
		#include <libavcodec/avcodec.h>
		#include <libavformat/avformat.h>
		#include <libavutil/avutil.h>

		typedef struct {
			AVCodec *c;
			AVCodecContext *ctx;
			AVFrame *f;
			int got;
		} h264dec_t ;

		static int h264dec_new(h264dec_t *h, uint8_t *data, int len) {
			h->c = avcodec_find_decoder(CODEC_ID_H264);
			h->ctx = avcodec_alloc_context3(h->c);
			h->f = av_frame_alloc();
			h->ctx->extradata = data;
			h->ctx->extradata_size = len;
			h->ctx->debug = 0x3;
			return avcodec_open2(h->ctx, h->c, 0);
		}

		static int h264dec_decode(h264dec_t *h, uint8_t *data, int len) {
			AVPacket pkt;
			av_init_packet(&pkt);
			pkt.data = data;
			pkt.size = len;
			return avcodec_decode_video2(h->ctx, h->f, &h->got, &pkt);
		}
	*/
	"C"
	"errors"
	"image"
	"unsafe"
)

type H264Decoder struct {
	m C.h264dec_t
}

func NewH264Decoder(header []byte) (m *H264Decoder, err error) {
	m = &H264Decoder{}
	r := C.h264dec_new(
		&m.m,
		(*C.uint8_t)(unsafe.Pointer(&header[0])),
		(C.int)(len(header)),
	)
	if int(r) < 0 {
		err = errors.New("open codec failed")
	}
	return
}

func (m *H264Decoder) Decode(nal []byte) (f *image.YCbCr, err error) {
	r := C.h264dec_decode(
		&m.m,
		(*C.uint8_t)(unsafe.Pointer(&nal[0])),
		(C.int)(len(nal)),
	)
	if int(r) < 0 {
		err = errors.New("decode failed")
		return
	}
	if m.m.got == 0 {
		err = errors.New("no picture")
		return
	}

	w := int(m.m.f.width)
	h := int(m.m.f.height)
	ys := int(m.m.f.linesize[0])
	cs := int(m.m.f.linesize[1])

	f = &image.YCbCr{
		Y:              fromCPtr(unsafe.Pointer(m.m.f.data[0]), ys*h),
		Cb:             fromCPtr(unsafe.Pointer(m.m.f.data[1]), cs*h/2),
		Cr:             fromCPtr(unsafe.Pointer(m.m.f.data[2]), cs*h/2),
		YStride:        ys,
		CStride:        cs,
		SubsampleRatio: image.YCbCrSubsampleRatio420,
		Rect:           image.Rect(0, 0, w, h),
	}

	return
}