/*
 * check_password_rules.c
 */

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

#define MAX_PASSWORD_SIZE 256



/*
Given a string, check whether it meets the quality rules for
UMD Directory passwords

Implement:
   * A password must be at least 8 and no more than 32 characters
     in length.
   * A password must contain at least one uppercase letter.
   * A password must contain at least one lowercase letter.
   * A password must contain at least one character
     from the set of digits or punctuation characters
     (such as # @ $ & among others).
   * A password may not begin or end with the space character.
   * A password may not contain more than two consecutive identical
     characters.

Do not implement
   * A password may not be (or be a variation of) a dictionary word
     in English or many other languages. This includes making simple
     substitutions of digits or punctuation that resemble alphabetic
     characters (such as replacing the letter S in a common word with
     the $ symbol).
   * You may not reuse a password you have already used.
*/
int
check_password_rules(char s[])
{
    int length      = 0;        // stores the password length
    int uppercase   = 0;        // count of uppercase characters
    int lowercase   = 0;        // count of lowercase characters
    int special     = 0;        // count of special characters
    int digit       = 0;        // count of digits
    int begin_space = 0;        // the string begins with a space
    int end_space   = 0;        // the string ends with a space
    int consecutive = 0;        // the string has consecutive identical chars
    char c, old_c;
    int i = -1;

    while ((i+1) <= MAX_PASSWORD_SIZE && (c = s[++i]) != '\0') {
        length++;

        // Check character classes
        if (c >= 'A' && c <= 'Z') {
            uppercase++;

        } else if (c >= 'a' && c <= 'z') {
            lowercase++;

        } else if (c >= '0' && c <= '9') {
            digit++;

        } else {
            switch (c) {
                case '#':
                case '@':
                case '$':
                case '&':
                    // Omit the rest, for brevity
                    special++;
                    break;

                case ' ':
                    if (i==0)
                        begin_space = 1;
                    break;
            }
        }

        // Check consecutive characters
        if (i >= 1 && c == old_c) {
            consecutive = 1;
        }

        // Maintain old_c
        old_c = c;
    }

    end_space = (old_c == ' ');

    // Print debugging info
//      printf ("length = %d\nuppercase = %d\nlowercase = %d\nspecial = %d\nbegin_space = %d\nend_space = %d\nconsecutive = %d\n",
//                      length, uppercase, lowercase, special, begin_space, end_space, consecutive);

    return  length >= 8 && length <= 32 &&
            uppercase > 0 &&
            lowercase > 0 &&
            (digit > 0 || special > 0) &&
            !begin_space &&
            !end_space &&
            !consecutive;
}


int
main ()
{
    char password[MAX_PASSWORD_SIZE];

    // Read password and check UMD rules

    printf("Enter your password: ");
    fgets(password, MAX_PASSWORD_SIZE, stdin);

    // Remove the final '\n' returned by fgets
    password[strnlen (password, MAX_PASSWORD_SIZE) - 1] = '\0';

    printf ("The string %s %s the UMD password requirements",
            password,
            check_password_rules(password) ? "meets" : "does not meet");


    return 0;
}