#include <stdio.h>
#include <ctype.h>
#define MAXSIZE 100

int main(void)
{
    FILE *message;
    FILE *encryptMessage;
    FILE *key;

    message = fopen("message.txt", "r");
    encryptMessage = fopen("encryptMessage.txt", "w");
    key = fopen("key.txt", "w");

    if  ((message == NULL) || (encryptMessage == NULL) || (key == NULL))
    {
            printf("Error reading file!!!\n");
            return 1;
    }

    int userKey;
    char sentence[MAXSIZE];
    char q[MAXSIZE];
    int i = 0;

//    printf("Input the text that you want to encrypt:\n> ");
//    fgets(sentence, 99, message);


   // printf("\nThe string that you wrote is:\n%s\n\n", sentence);

    printf("Input the key:\n");
    scanf("%d", &userKey);
    fprintf(key, "%d", userKey);

    //printf("\nThe key that you selected is: %d\n\n", userKey);


    while (fgets(sentence, MAXSIZE - 1, message)) {
        for(i = 0; sentence[i] != '\0'; ++i)
        {
            if( ( isupper(sentence[i]) ) || ( islower(sentence[i]) ) )
            {
                q[i] = sentence[i] + (char)userKey;
            }
            else
            {
                q[i] = (sentence[i]);
            }
        }
        q[i] = '\0';
        fprintf(encryptMessage, "%s", q);
    }


    fclose(encryptMessage);
    fclose(key);
    fclose(message);

    return 0;
}