package formats

import (
	"errors"
	"fmt"
	"github.com/bluenviron/gortsplib/v4"
	"github.com/bluenviron/gortsplib/v4/pkg/description"
	"github.com/bluenviron/gortsplib/v4/pkg/format"
	"github.com/bluenviron/gortsplib/v4/pkg/format/rtpvp8"
	"github.com/bluenviron/gortsplib/v4/pkg/format/rtpvp9"
	"github.com/pion/rtp"
	"image"
)

// FindVP9Format finds the VP9 media and format.
func FindVP9Format(desc *description.Session) (*format.VP9, *description.Media, error) {
	var vp9Format *format.VP9
	vp9Media := desc.FindFormat(&vp9Format)
	if vp9Media == nil {
		return nil, nil, errors.New("media VP9 not found")
	}

	return vp9Format, vp9Media, nil
}

// ProcessVP9RGBA processes VP9 flow and returns PTS and IMG.
func ProcessVP9RGBA(
	c *gortsplib.Client,
	vp9Media *description.Media,
	vp9RTPDec *rtpvp9.Decoder,
	vp9Dec *VPDecoder,
	pkt *rtp.Packet,
) (
	int64,
	*image.RGBA,
	error) {
	// Decode timestamp.
	pts, ok := c.PacketPTS2(vp9Media, pkt)
	if !ok {
		return 0, nil, fmt.Errorf("waiting for timestamp\n")
	}

	// Extract access units from RTP packets.
	au, err := vp9RTPDec.Decode(pkt)
	if err != rtpvp8.ErrNonStartingPacketAndNoPrevious && err != rtpvp8.ErrMorePacketsNeeded {
		return 0, nil, fmt.Errorf("decoding RTP packet error: %w", err)
	}

	// Convert VP8 access units into RGBA frames.
	img, err := vp9Dec.Decode(au)
	if err != nil {
		return 0, nil, fmt.Errorf("convert into RGBA frames error\n")
	}

	// Wait for a frame.
	if img == nil {
		return 0, nil, fmt.Errorf("frame not found\n")
	}

	return pts, img, nil
}