/*
 * Copyright (c) 2024 Mitchell Riedstra
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
 * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
 * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
 * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
 * OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
 * PERFORMANCE OF THIS SOFTWARE.
 *
 * Since `tr` on MacOS cannot handle the binary stream.
 *
 */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>

#define BUF_SIZE 64
#define MAX_OUT_CHARS 65534

void
help() {
	puts("genid [-d <rand device>] [-n <numchars]");
	exit(1);
}

int
main(int argc, char **argv)
{
	const char *rdev = "/dev/urandom";
	int chars = 8;
	char **a = argv+1;
	int fd, n;
	char c;
	int written = 0;

	for (;*a;a++) {
		if (strcmp(*a, "-d") == 0 && *(++a)) {
			rdev = *a;
		} else if (strcmp(*a, "-n") == 0 && *(++a)) {
				const char *errstr;
				chars = (int)strtonum(*a, 1, MAX_OUT_CHARS, &errstr);
				if (errstr != NULL) {
					printf("strtonum: %s\n", errstr);
					help();
				}
		} else {
			if (*a)
				printf("Unknown option: '%s'\n", *a);

			help();
		}
	}

	fd = open(rdev, O_RDONLY);
	if (fd == -1) {
		perror("opening random device");
		exit(1);
	}

	char buf[BUF_SIZE];
	for (int i=0; written<chars && i<1000; i++) {
		n = read(fd, &buf, BUF_SIZE-1);
		if (n == -1) {
			perror("read");
			exit(1);
		}

		for (int j = 0; j<n && j<BUF_SIZE && written<chars; j++) {
			c = buf[j];
			if (
					(c >= 'a' && c <= 'z') ||
					(c >= 'A' && c <= 'Z') ||
					(c >= '0' && c <= '9')
				) {
				written++;
				putc(c, stdout);
			}
		}
	}

	puts("");
	close(fd);
}