#include <stdio.h>
#include <string.h>
#include <sys/stat.h>
#include <stdlib.h>
#include <unistd.h>

/* so it's easier to fwrite */
typedef struct
{
	char cuehead[4];
	int chunk_size;
	int numcues;
	int cueid;
	int cuepos;

	char datahead[4];
	int chunk_start;
	int block_start;
	int sample_offset;
} loop_t;

/* -o enables users to specify at which point in the sample to start */
static int sample_offset;

void process_wav2loop(char *filename)
{
	FILE *fWAV;
	FILE *fLOOP;
	size_t szWAV;
	char *buffer;
	loop_t loopy;

	fWAV = fopen(filename, "rb");

	if (!fWAV) {
		fprintf(stderr, "couldn't find %s\n", filename);
		return;
	}

	/* get wav file size */
	fseek(fWAV, 0L, SEEK_END);
	szWAV = (size_t)ftell(fWAV);
	fseek(fWAV, 0L, SEEK_SET);

	/* load wav into memory */
	buffer = (char *)malloc(szWAV);

	if (buffer == NULL) {
		fprintf(stderr, "error: Memory allocation failed. Exiting.\n");
		exit(0);
	}

	fread(buffer, 1, szWAV, fWAV);
	fclose(fWAV);

	/* this is LAZY, however we're not going to bother writing a full WAV loader LMAO */
	for (int i = 0; i < (szWAV - 4); i++ ) {
		if (buffer[i] == 'c')
		if (buffer[i+1] == 'u')
		if (buffer[i+2] == 'e')
		if (buffer[i+3] == ' ') {
			fprintf(stderr, "wav file %s has cue info already\n", filename);
			goto end;
		}
	}

	/* this is quite stupid, we're just appending it at the end,
	   we don't even care if there already are other cue marks */	
	fLOOP = fopen(filename, "w+b");
	fwrite(buffer, 1, szWAV, fLOOP);
	
	loopy.cuehead[0] = 'c';
	loopy.cuehead[1] = 'u';
	loopy.cuehead[2] = 'e';
	loopy.cuehead[3] = ' ';
	loopy.chunk_size = 28;
	loopy.numcues = 1;
	loopy.cueid = 0;
	loopy.cuepos = 0;
	loopy.datahead[0] = 'd';
	loopy.datahead[1] = 'a';
	loopy.datahead[2] = 't';
	loopy.datahead[3] = 'a';
	loopy.chunk_start = 0;
	loopy.block_start = 0;
	loopy.sample_offset = sample_offset;

	/* append our data to the end of the file */
	fwrite(&loopy, 1, sizeof(loop_t), fLOOP);
	fclose(fLOOP);

	/* inb4 goto considered harmful */
end:
	free(buffer);
}

int main(int argc, char *argv[])
{
	int c, ch;

	if (argc <= 1) {
		fprintf(stderr, "usage: wav2loop [-o offset] file.wav ...\n");
		return 1;
	}

	/* by default, we loop at the very start */
	sample_offset = 0;

	/* process arguments: TODO: add more? probably not */
	while ((ch = getopt(argc, argv, "o")) != -1) {
		switch (ch) {
		case 'o':
			sample_offset = atoi(argv[optind]);
			optind++;
			printf("sample offset: %i\n", sample_offset);
			break;
		default:
			return 1;
		}
	}
	argc -= optind;
	argv += optind;

	for (c = 0; c < argc; c++)
		process_wav2loop(argv[c]);

	return 0;
}