package obuwriter

import (
	"encoding/binary"
	"errors"
	"git.gammaspectra.live/S.O.N.G/Ignite/utilities"
	"io"
)

type Writer struct {
	w io.Writer
}

func NewWriter(w io.Writer, width, height int, fourCC uint32, timeBase utilities.Ratio) (*Writer, error) {
	if err := binary.Write(w, binary.LittleEndian, struct {
		Magic       [4]byte
		Version     uint16
		HeaderSize  uint16
		FourCC      uint32
		Width       uint16
		Height      uint16
		Denominator uint32
		Numerator   uint32
		Length      uint32
		Unused      uint32
	}{
		Magic:       [4]byte{'D', 'K', 'I', 'F'},
		Version:     0,
		HeaderSize:  32,
		FourCC:      fourCC,
		Width:       uint16(width),
		Height:      uint16(height),
		Denominator: uint32(timeBase.Denominator),
		Numerator:   uint32(timeBase.Numerator),
		Length:      0,
	}); err != nil {
		return nil, err
	}

	return &Writer{
		w: w,
	}, nil
}

func (w *Writer) WriteFrameBytes(pts uint64, data []byte) error {
	if err := binary.Write(w.w, binary.LittleEndian, uint32(len(data))); err != nil {
		return err
	} else if err = binary.Write(w.w, binary.LittleEndian, pts); err != nil {
		return err
	} else if _, err = w.w.Write(data); err != nil {
		return err
	}

	return nil
}

// WriteLength writes the Length field for number of frames, if writer was set to io.WriteSeeker
func (w *Writer) WriteLength(frames uint32) error {
	if seeker, ok := w.w.(io.WriteSeeker); ok {
		if currentIndex, err := seeker.Seek(0, io.SeekCurrent); err != nil {
			return err
		} else {
			if _, err = seeker.Seek(4+2+2+4+2+2+4+4, io.SeekStart); err != nil {
				return err
			} else if err = binary.Write(w.w, binary.LittleEndian, frames); err != nil {
				return err
			} else if _, err = seeker.Seek(currentIndex, io.SeekStart); err != nil {
				return err
			}

			return nil
		}
	} else {
		return errors.New("writer is not io.WriteSeeker")
	}
}