/*
 * Copyright (c) 2026, Chloe M., et al.
 * Provided under the BSD-3 clause.
 */

#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <fcntl.h>
#include <assert.h>
#include <unistd.h>

static const char chrtab[] = {
    "ab123cde987654321=0fghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWZYZ"
    "!@#$%^&*()[]><?"
};

static void
help(void)
{
    printf("usage: ./newpass [flags]\n");
    printf("[-h]    Display this help menu\n");
    printf("[-l]    Length of password to create\n");
    printf("[-c]    Number of passwords to generate\n");
}

static void *
xmalloc(size_t sz)
{
    void *buf;

#ifdef __OpenBSD__
    buf = malloc_conceal(sz);
#else
    buf = malloc(sz);
#endif

    assert(buf != NULL && "allocation failure");
    return buf;
}

static uint8_t *
randbytes(size_t count)
{
    int fd;
    uint8_t *buf;
    ssize_t nbyte;

    buf = xmalloc(count);
    fd = open("/dev/urandom", O_RDONLY);

    if (fd < 0) {
        perror("open");
        free(buf);
        return NULL;
    }
    
    if ((nbyte = read(fd, buf, count)) < 0) {
        perror("read");
        free(buf);
        close(fd);
        return NULL;
    }

    return buf;
}

static void
genpass(size_t passlen)
{
    uint8_t ind, *bytes;
    size_t i;
    
    if ((bytes = randbytes(passlen)) == NULL) {
        printf("fatal: unable to generate random bytes\n");
        return;
    }

    for (i = 0; i < passlen; ++i) {
        ind = bytes[i] % sizeof(chrtab);
        printf("%c", chrtab[ind]);
    }

    printf("\n");
    free(bytes);
}

int
main(int argc, char **argv)
{
    int opt;
    size_t passlen = 0;
    size_t i, passcount = 0;

    while ((opt = getopt(argc, argv, "hl:c:")) != -1) {
        switch (opt) {
        case 'h':
            help();
            return -1;
        case 'l':
            if ((passlen = atoi(optarg)) == 0) {
                printf("fatal: bad length given\n");
                return -1;
            }

            break;
        case 'c':
            if ((passcount = atoi(optarg)) == 0) {
                printf("fatal: bad count given\n");
                return -1;
            }

            break;
        }
    }

    if (passcount == 0) {
        ++passcount;
    }

    if (passlen == 0) {
        printf("fatal: please specify a length with '-l'\n");
        help();
        return -1;
    }

    for (i = 0; i < passcount; ++i) {
        genpass(passlen);
    }

    return 0;
}