//      cripto_cesar.c
//      
//      Copyright 2010 Orlando Xavier <ox@orlandoxavier.org>
//      
//      This program is free software; you can redistribute it and/or modify
//      it under the terms of the GNU General Public License as published by
//      the Free Software Foundation; either version 2 of the License, or
//      (at your option) any later version.
//      
//      This program is distributed in the hope that it will be useful,
//      but WITHOUT ANY WARRANTY; without even the implied warranty of
//      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//      GNU General Public License for more details.
//      
//      You should have received a copy of the GNU General Public License
//      along with this program; if not, write to the Free Software
//      Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
//      MA 02110-1301, USA.

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

void encrypt(void);
void uncrypt(void);
void lowercase(char string[]);
void clear(void) { system("clear"); }
void getch(void) { system("read key"); }
int main(int argc, char** argv) {
   
   int menu = 0;
   
   do {
      printf("\n\nEnter para Continuar: \n");
      getch();
      clear();
      printf("+----------------------------+\n");
      printf("|;.<<,y7= Cesar-Crypto +;-,~^|\n");
      printf("+--------------+-------------+\n");
      printf("|&.6,+---------+--------+`~{,|\n");
      printf("|*[3,|  (1) - Encrypt   |,.çz|\n");
      printf("|;5m.+---------+--------+[k/;|\n");
      printf("|,'.;+---------+--------+.7.,|\n");
      printf("|}1>i|  (2) - uncrypt   |'^,>|\n");
      printf("|^f,;+---------+--------+,j.'|\n");
      printf("|&];.+---------+--------+x~};|\n");
      printf("|.4-a|  (3) - Exit      |'.,!|\n");
      printf("+----+------------------+----+\n");
      printf("Escolha uma opcao: ");
      scanf("%d",&menu);
      switch (menu) {
         case 1:
            encrypt();
            break;
         case 2:
            uncrypt();
         break;
      }
   } while (menu != 3);
   return(0);
}

void encrypt(void) {
   char string[255];
   int i = 0;
   
   clear();
   printf("Entre com a palavra: ");
   gets(string);
   gets(string);
   lowercase(string);
   for (; string[i] != '{FONTE}'; i++) {
      if (string[i] == 'z')
         string[i] = 'c';
      else if (string[i] == 'y')
         string[i] = 'b';
      else if (string[i] == 'x')
         string[i] = 'a';
      else
         string[i] = string[i] + 3;
   }
   printf("Resultado >> ");
   for (i = 0; string[i] != '{FONTE}'; i++) {
      printf("%c",string[i]);
   }
}

void uncrypt(void) {
   char string[255];
   int i = 0;
   
   clear();
   printf("Entre com a sequencia: ");   
   gets(string);
   gets(string);
   lowercase(string);
   for (; string[i] != '{FONTE}'; i++) {
      if (string[i] == 'c')
         string[i] = 'z';
      else if (string[i] == 'b')
         string[i] = 'y';
      else if (string[i] == 'a')
         string[i] = 'x';
      else
         string[i] = string[i] - 3;
   }
   printf("Resultado >> ");
   for (i = 0; string[i] != '{FONTE}'; i++) {
      printf("%c",string[i]);
   }
}

void lowercase(char string[])
{
   int  i = 0;

   while (string[i]) {
      string[i] = tolower(string[i]);
      i++;
   }

   return;
}