#define PROGRAM_NAME "pcm"
#define USAGE_OPTS "infile.wav outfile.pcm"

#include "common.h"

#define CHUNKID(b1, b2, b3, b4) (uint32_t)((uint32_t)(b1) | ((uint32_t)(b2) << 8) | ((uint32_t)(b3) << 16) | ((uint32_t)(b4) << 24))

int32_t get_uint16le(uint8_t *data, long size, long i) {
	return i + 2 < size ? (int32_t)data[i] | ((int32_t)data[i + 1] << 8) : -1;
}

int64_t get_uint32le(uint8_t *data, long size, long i) {
	return i + 4 < size ? (int64_t)data[i] | ((int64_t)data[i + 1] << 8) | ((int64_t)data[i + 2] << 16) | ((int64_t)data[i + 3] << 24) : -1;
}

uint8_t *wav2pcm(uint8_t *wavdata, long wavsize, size_t *pcmsize) {
	int64_t fourcc = get_uint32le(wavdata, wavsize, 0);
	if (fourcc != CHUNKID('R', 'I', 'F', 'F')) {
		error_exit("WAV file does not start with 'RIFF'\n");
	}

	int64_t waveid = get_uint32le(wavdata, wavsize, 8);
	if (waveid != CHUNKID('W', 'A', 'V', 'E')) {
		error_exit("RIFF chunk does not start with 'WAVE'\n");
	}

	long sample_offset = 0;
	int64_t num_samples = 0;

	int64_t riffsize = get_uint32le(wavdata, wavsize, 4) + 8;
	for (long i = 12; i < riffsize;) {
		int64_t chunkid = get_uint32le(wavdata, wavsize, i);
		int64_t chunksize = get_uint32le(wavdata, wavsize, i + 4);
		if (chunksize == -1) {
			error_exit("Failed to read sub-chunk size\n");
		}
		i += 8;

		// Require 22050 Hz 8-bit PCM WAV audio
		if (chunkid == CHUNKID('f', 'm', 't', ' ')) {
			int32_t audio_format = get_uint16le(wavdata, wavsize, i);
			if (audio_format != 1) {
				error_exit("WAV data is not PCM format\n");
			}
			int32_t num_channels = get_uint16le(wavdata, wavsize, i + 2);
			if (num_channels != 1) {
				error_exit("WAV data is not mono\n");
			}
			int64_t sample_rate = get_uint32le(wavdata, wavsize, i + 4);
			if (sample_rate != 22050) {
				error_exit("WAV data is not 22050 Hz\n");
			}
			int32_t bits_per_sample = get_uint16le(wavdata, wavsize, i + 14);
			if (bits_per_sample != 8) {
				error_exit("WAV data is not 8-bit\n");
			}
		}

		else if (chunkid == CHUNKID('d', 'a', 't', 'a')) {
			sample_offset = i;
			num_samples = chunksize;
			break;
		}

		i += chunksize;
	}

	if (!num_samples) {
		error_exit("WAV data has no PCM samples\n");
	}

	// Pack 8 WAV samples per PCM byte, clamping each to 0 or 1
	*pcmsize = (size_t)((num_samples + 7) / 8);
	uint8_t *pcmdata = xmalloc(*pcmsize);
	for (int64_t i = 0; i < num_samples; i += 8) {
		uint8_t v = 0;
		for (int64_t j = 0; j < 8 && i + j < num_samples; j++) {
			v |= (wavdata[sample_offset + i + j] > 0x80) << (7 - j);
		}
		pcmdata[i / 8] = v;
	}
	return pcmdata;
}

int main(int argc, char *argv[]) {
	if (argc != 3) {
		usage_exit(1);
	}

	long wavsize;
	uint8_t *wavdata = read_u8(argv[1], &wavsize);
	size_t pcmsize;
	uint8_t *pcmdata = wav2pcm(wavdata, wavsize, &pcmsize);
	write_u8(argv[2], pcmdata, pcmsize);

	free(wavdata);
	free(pcmdata);
	return 0;
}