package mp3

/*
#cgo CFLAGS: -I"${SRCDIR}/../../../cgo" -march=native -Ofast -std=c99
#include "audio.h"
*/
import "C"
import (
	"git.gammaspectra.live/S.O.N.G/Kirika/audio"
	mp3Lib "github.com/kvark128/minimp3"
	"io"
	"unsafe"
)

type Format struct {
}

func NewFormat() Format {
	return Format{}
}

func (f Format) Open(r io.ReadSeekCloser, blockSize int) (*audio.Stream, error) {
	decoder := mp3Lib.NewDecoder(r)

	_, err := decoder.Read([]byte{})
	if err != nil {
		return nil, err
	}

	newChannel := make(chan []float32)

	go func() {
		defer close(newChannel)
		samples := make([]int16, blockSize*2)
		const SizeofInt16 = int(unsafe.Sizeof(int16(0)))
		byteSlice := unsafe.Slice((*byte)(unsafe.Pointer(&samples[0])), len(samples)*SizeofInt16)
		for {
			n, err := decoder.Read(byteSlice)
			if err != nil {
				return
			}
			n /= SizeofInt16

			buf := make([]float32, n)

			//convert 16-bit to f32 samples
			C.audio_int16_to_float32((*C.int16_t)(&samples[0]), C.size_t(n), (*C.float)(&buf[0]), C.int(16))

			newChannel <- buf
		}
	}()

	return audio.NewStream(newChannel, decoder.Channels(), float64(decoder.SampleRate()), blockSize), nil
}

func (f Format) Identify(peek []byte, extension string) bool {
	return /*bytes.Compare(peek[:4], []byte{'f', 'L', 'a', 'C'}) == 0 || */ extension == "mp3"
}