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 = avcodec_alloc_frame();
		h->ctx->extradata = data;
		h->ctx->extradata_size = len;
		h->ctx->debug = 0x3;
		return avcodec_open2(h->ctx, h->c, 0);
	}

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

type H264Decoder struct {
	m C.h264dec_t
}

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

func (m *H264Decoder) Decode(nal []byte) (f *image.YCbCr, err error) {
	C.h264dec_decode(
		&m.m,
		(*C.uint8_t)(unsafe.Pointer(&nal[0])),
		(C.int)(len(nal)),
	)
	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
}