#include <cs50.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <ctype.h>

// take in command line argument &  eliminate any wrong intake (lines 12-14)

int main(int argc, string argv[]) {

    if (argc != 2){
        printf ("mising command-line arguement\n");
        return 1;

    } else {


// check if argc[1] is a string

        string key = (argv[1]);

        int keylen = strlen(key);

//inside the for loop;
// 1) checking if the input is solely aplha
// 2) changeing key to all lowercase

        for (int str = 0; str < keylen; str++){

           if (!isalpha(key[str])) {

                printf("Key needs to be only characters!\n");
                return 1;
           }

            if ((isupper(key[str]))) {
                key[str] = (tolower(key[str]));
            }

        }

// now key is in lowercase
// will have to use isalpha when iterating over  plaintext

//take in plaintext and display ciphertext;

            printf("Plaintext:  ");
            string plaintext = get_string();
            printf("Ciphertext:  ");

// now to iterate over the plaintext

            int g = 0;

            for (int q = 0; q < strlen(plaintext) ; q++){


//need to ensure that its only letters that change using ASCII values

            int l = (g % (strlen(argv[1])));


                if islower(plaintext[q]) {

                   printf("%c", ((((plaintext[q] - 97) + (key[l] - 97))   %26 ) +97 ));
                   g++;

                }

                else if isupper(plaintext[q]) {
                   printf("%c", ((((plaintext[q] -65) + (key[l] - 65))  %26 ) +65 ));
                   g++;

                }

                else {
                   printf("%c", (plaintext[q]));
                }

        }

    printf("\n");

    }

}