#include<stdio.h>
#include<stdlib.h>
#include<string.h>
char menu(void);
char action(char option);
void encypt();
void decrypt();



char menu(void){
  int i;
  char option;
  printf("Pick whether you would like to enycrypt a text or decrypt a text.\n");
  printf("1 - encrypt\n");
  printf("2 - decrypt\n");
  printf("x - end\n");
  scanf(" %c", &option);



  return option;
}


void encrypt(){
  char message[100], ch;
    int i, key;

    printf("Enter a message to encrypt: \n");
    fgets(message,100,stdin);
    scanf("%s",message);
    printf("Enter key: \n");
    scanf("%d", &key);

    for(i = 0; message[i] != '\0'; ++i){
        ch = message[i];

        if(ch >= 'a' && ch <= 'z'){
            ch = ch + key;

            if(ch > 'z'){
                ch = ch - 'z' + 'a' - 1;
            }

            message[i] = ch;
        }
        else if(ch >= 'A' && ch <= 'Z'){
            ch = ch + key;

            if(ch > 'Z'){
                ch = ch - 'Z' + 'A' - 1;
            }

            message[i] = ch;
        }
    }

   printf("Encrypted message: %s\n", message);
}
void decrypt(){
  char ch,message_1[100];
    int i, key;
  printf("Enter a message to decrypt:\n");
    fgets(message_1,100,stdin);
    scanf("%s",message_1);
     printf("Enter key: ");
    scanf("%d", &key);
    for(i = 0; message_1[i] != '\0'; ++i){
        ch = message_1[i];

        if(ch >= 'a' && ch <= 'z'){
            ch = ch - key;

            if(ch < 'a'){
                ch = ch + 'z' - 'a' + 1;
            }

            message_1[i] = ch;
        }
        else if(ch >= 'A' && ch <= 'Z'){
            ch = ch - key;

            if(ch < 'A'){
                ch = ch + 'Z' - 'A' + 1;
            }

            message_1[i] = ch;
        }
    }

    printf("Decrypted message: %s\n", message_1);
}
int main(){
    char option;
    printf("Encryption and decription program\n");
    printf("-------------------------------------\n");

    do{
      option = menu();
      switch(option){
         case '1':
      encrypt();
      break;

      case '2':
      decrypt();
      break;

      }
      getchar();
    }
    while(option != 'x');
    return 0;
}