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#include "config.h"

#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <string.h>

#ifdef __linux__
#include <sys/random.h>
#else
#include <time.h>

#if defined (_WIN32) && ! defined (__MINGW32__)
#include <io.h>
#elif ! defined (__linux__)
#include <unistd.h>
#endif

#endif


#define CLASS(c, chars) \
  case c: \
    class = chars; \
    class_size = sizeof(chars)-1; \
    break;


int main(int argc, char *argv[])
{
    bool custom_grammar = false;
    char *grammar = DEFAULT_GRAMMAR;
    int grammar_size = sizeof(DEFAULT_GRAMMAR)-1;

    if (argc == 2) {
        // Take first argument as the grammar
        grammar = argv[1];
        grammar_size = strlen(grammar);
    } else if (argc == 4) {
        // Take arguments as triplets, specials, numbers
        // atoi might be scuffed but so be it (it just goes = 0 if invalid input)
        int triplets = atoi(argv[1]);
        int specials = atoi(argv[2]);
        int numbers = atoi(argv[3]);

        if (triplets < 1) {
            fprintf(stderr, "ERROR: Cannot have less than one triplet.");
            return 1;
        }

        grammar_size = triplets * 3 + specials + numbers;
        grammar = malloc(grammar_size + 1);
        if (grammar == NULL) {
            perror("malloc");
            return 1;
        }
        grammar[grammar_size] = 0;

        memcpy(grammar, "Cvc", 3);
        for (int i = 1; i < triplets; ++i)
            memcpy(grammar + (i * 3), "cvc", 3);

        memset(grammar + (triplets * 3), '!', specials);
        memset(grammar + (triplets * 3) + specials, '#', numbers);
        custom_grammar = true;
    }

    char *password = malloc(grammar_size + 1);
    if (password == NULL) {
        perror("malloc");
        return 1;
    }
    password[grammar_size] = 0;

#ifndef __linux__
    // seed RNG; this isn't very good, but it's enough(?)
    srand(time(NULL) + getpid() % 420 - 69);
#endif

    for (int i = 0; i < grammar_size; ++i) {
        char c = grammar[i];

        bool caps = false;
        if (c >= 'A' && c <= 'Z') {
            caps = true;
            c += 'a' - 'A';
        }

        char *class;
        int class_size = 0;
        switch (c) {
            CLASSES
        default:
            fprintf(stderr, "ERROR: Invalid grammar character '%c'.\n", c);
            if (custom_grammar)
                free(grammar);
            free(password);
            return 1;
        }

        do {
#ifdef __linux__
            unsigned int r;
            getrandom(&r, sizeof(r), 0);
#else
            long r = rand();
#endif
            password[i] = class[r % class_size] - (caps ? 'a' - 'A' : 0);
        } while (i != 0 && password[i] == password[i-1]);
    }

    if (custom_grammar)
        free(grammar);

    printf("%s\n", password);
    free(password);

    return 0;
}