/* references:
https://www.gnu.org/software/ccd2cue/manual/html_node/CUE-sheet-format.html
https://wiki.osdev.org/User:Combuster/CDRom_BS
https://en.wikipedia.org/wiki/CD-ROM */

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

const char *self;

#define RAW_SECTOR_SIZE 2352
#define DATA_SECTOR_SIZE 2048

unsigned char mode1_sync[] = {
	0x00, 0xff, 0xff, 0xff,
	0xff, 0xff, 0xff, 0xff,
	0xff, 0xff, 0xff, 0x00 };

double silence_sec = 2.0l;
int silence_frames; /* same as above in 1/75 sec frames */
int silence_thresh = 0;
int multi_bin = 0;
int verbose = 0;
char *outfile = NULL;

void die(const char *msg) {
	if(!msg) msg = strerror(errno);
	fprintf(stderr, "%s: %s\n", self, msg);
	exit(1);
}

void usage() {
	fprintf(stderr, "cuerecover v" VERSION " by B. Watson, WTFPL\n");
	fprintf(stderr, "Usage: %s [-s sec] [-t thresh] bin-file [bin-file ...]\n", self);
	fprintf(stderr, "See man page for details\n");
	exit(0);
}

int looks_like_filesystem(const char *filename, FILE *f) {
	int have_apple_magic = 0, have_iso_magic = 0;
	char buf[2048];

	if(fseek(f, 0L, SEEK_SET) < 0)
		die(NULL);

	if(!fread(buf, 2048, 1, f)) {
		fprintf(stderr, "%s: file %s is too short to be a CD image file\n", self, filename);
		return 0;
	}

	if(buf[0] == 'E' && buf[1] == 'C' && buf[2] == 'M') {
		fprintf(stderr, "%s: file %s is ECM, use 'ecm2bin' to convert to raw bin\n", self, filename);
		exit(1);
	}

	if(buf[0] == 'E' && buf[1] == 'R' && buf[3] == 0 && (buf[2] == 0x02 || buf[2] == 0x08))
	{
		have_apple_magic++;
	}

	if(fseek(f, 16 * 2048L, SEEK_SET) < 0)
		die(NULL);

	if(!fread(buf, 2048, 1, f)) {
		fprintf(stderr, "%s: file %s is too short to be a CD image file\n", self, filename);
		return 0;
	}

	if(strncmp("\x01" "CD001", buf, 6) == 0) {
		have_iso_magic++;
	}

	if(fseek(f, 0L, SEEK_SET) < 0)
		die(NULL);

	if(have_apple_magic && have_iso_magic) {
		fprintf(stderr, "%s: file %s looks like hybrid ISO/HFS image\n", self, filename);
	} else if(have_apple_magic) {
		fprintf(stderr, "%s: file %s looks like Mac HFS image\n", self, filename);
	} else if(have_iso_magic) {
		fprintf(stderr, "%s: file %s looks like ISO9660 image\n", self, filename);
	}

	return have_apple_magic || have_iso_magic;
}

int frame_is_silent(const char *data) {
	int i, nonzero = 0;
	for(i=0; i<RAW_SECTOR_SIZE; i++)
		if(data[i]) nonzero++;

	if(nonzero <= silence_thresh)
		return 1;
	return 0;
}

const char *frame2time(int frame) {
	static char buf[10];
	int min, sec;

	min = frame / (75 * 60);
	frame %= (75 * 60);
	sec = frame / 75;
	frame %= 75;

	sprintf(buf, "%02d:%02d:%02d", min, sec, frame);

	return buf;
}

int read_sector(FILE *f, char *buf) {
	/*
	if(verbose)
		fprintf(stderr, "read_sector at pos %d\n", ftell(f));
	 */
	return fread(buf, RAW_SECTOR_SIZE, 1, f);
}

int has_mode1_sync(char *buf) {
	return (memcmp(buf, mode1_sync, sizeof(mode1_sync)) == 0);
}

int get_sector_mode(char *buf) {
	if(!has_mode1_sync(buf))
		return 0; /* audio, or something we don't grok */

	return buf[15];
}

int unbcd(int bcd) {
	int hi, lo;

	lo = bcd & 0x0f;
	hi = (bcd >> 4) & 0x0f;
	return hi * 10 + lo;
}

int get_sector_addr(char *buf) {
	int mm, ss, ff;
	mm = unbcd(buf[12]);
	ss = unbcd(buf[13]);
	ff = unbcd(buf[14]);
	return mm * 75 * 60 + ss * 75 + ff;
}

const char *mode_string(int mode) {
	switch(mode) {
		case 1: return "MODE1/2352";
		case 2: return "MODE2/2352";
		default: return "AUDIO";
	}
}

struct track {
	int mode;
	int index0;
	int index1;
};

void process_single(char *filename) {
	char buf[RAW_SECTOR_SIZE];
	FILE *f;
	int i;
	int track = 0;
	int sector = 0;
	int mode;
	int silence_start, in_silence = 0;
	struct track tracklist[100];
	struct track *t = tracklist;

	if(!(f = fopen(filename, "rb")))
		die(NULL);

	if(looks_like_filesystem(filename, f)) {
		fprintf(stderr, "%s: %s looks like 'cooked' data!\n", self, filename);
		/*
		// don't know all the details on how this works yet
		int skipped_sectors = 0;
		fprintf(stderr, "%s: %s looks like 'cooked' data, ", self, filename);
		if((skipped_sectors = skip_fs(filename, f))) {
		fprintf(stderr, "skipped %d 2048-byte sectors\n", skipped_sectors);
		} else {
		fprintf(stderr, "but not ISO9660, don't know how to skip it\n");
		}
		 */
	}

	/* only the first track can be data */
	if(read_sector(f, buf) && (mode = get_sector_mode(buf)) != 0) {
		if(verbose) fprintf(stderr, "track %d is data, mode %d\n", track, mode);
		t->index0 = sector;
		t->index1 = sector;
		t->mode = mode;

		/* skip over the data sectors */
		while(read_sector(f, buf) && (get_sector_mode(buf) == mode))
			sector++;

		/* now buf holds the first audio sector, which might or might not
			begin with silence */
		t++; track++;
		t->mode = 0;
		t->index0 = sector;
		t->index1 = sector;
	}

	if(silence_frames) while(read_sector(f, buf)) {
		if(frame_is_silent(buf)) {
			if(in_silence) {
				/* nothing */
			} else {
				t->index0 = sector;
				t->index1 = -1;
				silence_start = sector;
				in_silence = 1;
			}
		} else {
			if(in_silence) {
				if((sector - silence_start) >= silence_frames) {
					in_silence = 0;
					t->index1 = sector;
					t++;
					track++;
					if(track > 99) {
						fprintf(stderr, "%s: too many tracks (>99), skipping rest of file\n", self);
						break;
					}
					t->mode = 0;
				} else {
					/* nothing */
				}
			}
		}
		sector++;
	}

	fclose(f);

	t = tracklist;
	printf("FILE \"%s\" BINARY\r\n", filename);
	for(i=0; i<=track; t++, i++) {
		if(verbose) {
			fprintf(stderr, "track %d, mode %d, index0 %d, index1 %d\n",
					i, t->mode, t->index0, t->index1);
		}
		if(t->index1 > -1) {
			printf("  TRACK %02d %s\r\n", i + 1, mode_string(t->mode));
			if(t->index0 < t->index1) {
				if(silence_frames && t->index1 - t->index0 > silence_frames) {
					t->index0 = t->index1 - silence_frames;
					if(verbose)
						fprintf(stderr, "   (index0 adjusted to %d)\n", t->index0);
				}
				printf("    INDEX 00 %s\r\n", frame2time(t->index0));
			}
			printf("    INDEX 01 %s\r\n", frame2time(t->index1));
		}
	}
}

void process_multi(char **filenames) {
	char *filename;
	int track = 0;
	char buf[RAW_SECTOR_SIZE];
	FILE *f;

	while((filename = *filenames++)) {
		int index0 = 0, index1 = -1;
		int mode = -1;
		int sector = 0;

		track++;

		if(verbose) fprintf(stderr, "reading %s\n", filename);
		if(!(f = fopen(filename, "rb")))
			die(NULL);

		printf("FILE \"%s\" BINARY\r\n", filename);

		if(looks_like_filesystem(filename, f)) {
			fprintf(stderr, "%s: %s looks like 'cooked' data, assuming MODE1/2048\n",
					self, filename);
			printf("  TRACK %02d MODE1/2048\r\n", track);
			printf("    INDEX 01 00:00:00\r\n");
			continue;
		}

		while(read_sector(f, buf)) {
			mode = get_sector_mode(buf);

			/* if first sector is data, there's no index 01, we're done */
			if(mode > 0) {
				index0 = 0;
				index1 = -1;
				break;
			}

			/* for audio, keep reading silence until we hit sound */
			if(mode == 0 && index1 == -1 && !frame_is_silent(buf)) {
				index1 = (sector / 75) * 75; /* round to integer number of seconds */
				break;
			}

			sector++;
		}
		fclose(f);

		printf("  TRACK %02d %s\r\n", track, mode_string(mode));
		if(index1 < 1) {
			printf("    INDEX 01 %s\r\n", frame2time(index0));
		} else {
			printf("    INDEX 00 %s\r\n", frame2time(index0));
			printf("    INDEX 01 %s\r\n", frame2time(index1));
		}
	}
}

char **parse_args(int argc, char **argv) {
	if(argc == 1) usage();
	if(argc > 1 && strcmp(argv[1], "--help") == 0) usage();

	while(++argv, --argc) {
		if(argv[0][0] == '-') {
			char *nextarg = argv[1];
			switch(argv[0][1]) {
				case 'v':
					verbose++; break;
				case 'o':
					if(nextarg)
						outfile = nextarg;
					else
						die("-o requires an output filename");
					argv++, argc--;
					break;
				case 's':
					if(nextarg && ((*nextarg >= '0' && *nextarg <= '9') || (*nextarg == '.'))) {
						silence_sec = atof(nextarg);
						argv++, argc--;
					} else {
						die("-s requires numeric seconds argument");
					}
					break;
				case 't':
					if(nextarg &&
							(*nextarg >= '0' && *nextarg <= '9') &&
							(silence_thresh = atoi(nextarg) <= 100))
					{
						silence_thresh = (RAW_SECTOR_SIZE / 100.0) * atoi(nextarg);
						argv++, argc--;
					} else {
						die("-t requires numeric percentage argument, 0-100");
					}
					break;
				default:
					fprintf(stderr, "unrecognized option '%s', try --help\n", *argv);
					exit(1);
					break;
			}
		} else {
			break;
		}
	}

	silence_frames = (int)(75.0l * silence_sec);
	multi_bin = (argc > 1);
	return argv;
}

void redirect_output(void) {
	struct stat ss;

	if(lstat(outfile, &ss) >= 0)
		die("output file exists, not overwriting");

	if(!(freopen(outfile, "w", stdout)))
		die(NULL);
}

void set_exe_name(const char *argv0) {
	const char *p;
	self = argv0;
	for(p = self; *p; p++)
		if(p[0] == '/' && p[1]) self = p + 1;
}

int main(int argc, char **argv) {
	set_exe_name(argv[0]);

	argv = parse_args(argc, argv);

	if(verbose) fprintf(stderr, "writing %s CUE file to %s\n",
			(multi_bin ? "multi-bin" : "single-bin"),
			(outfile ? outfile : "<standard output>"));

	if(outfile) redirect_output();

	if(multi_bin)
		process_multi(argv);
	else
		process_single(*argv);

	return 0;
}