#include <cs50.h>
#include <stdio.h>
#include <string.h>
#include <crypt.h>

char next(char c);

int main(int argc, string argv[])
{
    //check correct usage.
    if (argc == 2)
    {}
    else
    {
        printf("Usage ./crack hash\n");
        return 1;
    }
    //initialize starting variables
    string key = argv[1];
    bool result = false;
    char word[6] = "\0";
    word[0] = 'A';

    //extract salt
    char salt[3];
    salt[0] = key[0];
    salt[1] = key[1];
    salt[2] = '\0';

    // main loop
    while(!result)
    {

        //check if word yield correct hash
        if (strcmp(crypt(word, salt), argv[1]) == 0)
        {
            result = true;
            break;
        }
        // for each character in word
        for (int n = strlen(word)-1; n >= 0; n--)
        {
            //check if word is final option available ('z')
            if (word[n] == 'z')
            {
                // if first letter is final option available assume every other letter in word is also final option
                // increment each one and add another letter
                if (n == 0)
                {
                    int k = strlen(word);
                    for (int j = 0;  j < k ;j++)
                    {
                        word[j+1] = 'A';
                    }
                }
                word[n] = next(word[n]);
            }
            // if letter is not final option, change letter to next letter available
            else
            {
                word[n] = next(word[n]);
                break;
            }
        }
    }
    // if correct result is found print it
    printf("result is: %s\n",word);
}

//function for easy changing of available option pool.
char next(char c)
{
    c = c + 1;
    if (c == 'Z' + 1)
    {
        c = 'a';
    }
    if (c == 'z' + 1)
    {
        c = 'A';
    }
    return c;
}