static const char *wav_hdr = "RIFF";
static const char *wav_hdr_fmt = "fmt ";
static const char *wav_hdr_data = "data";
static const char *wav_format = "WAVE";
#define WAV_HDRSIZE 44

typedef struct {
	uint32_t samplerate;
	uint16_t channels;
	uint16_t bytes;
	uint32_t samples;
	FILE *fd;
	const char *filename;
	uint8_t *buffer;
} wav_handle;

void wav_write_uint32(uint8_t *data, uint32_t value) {
	for(int h = 0; h < 4; h++) {
		data[h] = ((uint32_t)((value >> (8*h) & 0xff)));
	}
}

void wav_write_uint16(uint8_t *data, uint16_t value) {
	for(int h = 0; h < 2; h++) {
		data[h] = ((uint16_t)((value >> (8*h) & 0xff)));
	}
}

void wav_write_header(uint8_t *data, uint32_t samplerate, uint16_t channels, uint32_t samples, uint16_t bytes) {
	memcpy(data+0, wav_hdr, 4);
	wav_write_uint32(data+4, 36 + samples * ((uint32_t)channels) * ((uint32_t)bytes));
	memcpy(data+8, wav_format, 4);
	memcpy(data+12, wav_hdr_fmt, 4);
	wav_write_uint32(data+16, 16);
	wav_write_uint16(data+20, 1);
	wav_write_uint16(data+22, channels);
	wav_write_uint32(data+24, samplerate);
	wav_write_uint32(data+28, samplerate * ((uint32_t)channels) * ((uint32_t)bytes));
	wav_write_uint16(data+32, channels * bytes);
	wav_write_uint16(data+34, 8 * bytes);
	memcpy(data+36, wav_hdr_data, 4);
	wav_write_uint32(data+40, samples * ((uint32_t)channels) * ((uint32_t)bytes));
}

bool wav_open(wav_handle *wav, const char *filename, uint32_t samplerate, uint16_t channels, uint16_t bytes) {
	int err;
	FILE *fd = fopen(filename, "wb");
	if(fd == NULL) {
		err = errno;
		mid_log(STR_WAV_OPNERR, filename, strerror(err), err);
		return false;
	}
	uint8_t pad[WAV_HDRSIZE];
	memset(pad, 0, WAV_HDRSIZE);
	if(fwrite(pad, 1, WAV_HDRSIZE, fd) != WAV_HDRSIZE) {
		mid_log(STR_WAV_EIO, filename);
		fclose(fd);
		return false;
	}
	wav->fd = fd;
	wav->samplerate = samplerate;
	wav->channels = channels;
	wav->bytes = bytes;
	wav->samples = 0;
	wav->filename = filename;
	return true;
}

bool wav_close(wav_handle *wav) {
	if(wav->fd == NULL) {
		return false;
	}
	int err;
	if(fseek(wav->fd, 0L, SEEK_SET)) {
		err = errno;
		mid_log(STR_WAV_EGEN, wav->filename, strerror(err), err);
		fclose(wav->fd);
		return false;
	}
	uint8_t header[WAV_HDRSIZE];
	wav_write_header(header, wav->samplerate, wav->channels, wav->samples, wav->bytes);
	if(fwrite(header, 1, WAV_HDRSIZE, wav->fd) != WAV_HDRSIZE) {
		mid_log(STR_WAV_EIO, wav->filename);
		fclose(wav->fd);
		return false;
	}
	fclose(wav->fd);
	return true;
}