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


int shift(char q);// declaring function to handle keyword

int main(int argc, string argv [])

{
    string j = argv [1] ;

    if (argc != 2)
    {
        printf("BAD COMMAND\n");
        return 1;
    }

for (int s = 0, m = strlen(j); s < m; s++) // to iterate over keyword string

{
    if ( isalpha (j[s])== false)
    {

 printf("BAD COMMAND\n");
        return 1;
    }

    else
    {

   ;

    }

}

char k[strlen(j)] ; // declaring array k


    string p = get_string("plaintext: ");

    char c [strlen(p)]; // a char variable with the same string length of p

    printf("ciphertext: ");
    int x ; // variable to preserve letter case

int u = 0;


     for (int i = 0, n = strlen(p) ; i < n; i++)  //this is the loop to iterate over each character of the string

    {
        k[u] = shift(argv [1][u]);

        if (isalpha (p[i]) == true)

{
   u++ ;
}

     if (isupper(p[i]))
        {
            x = 65;
        }
        else if (islower(p[i]))
        {
            x = 97;
        }


        c[i] = (((p[i] - x) + k[u]) % 26) + x ; // this equation is to convert from ascii to alphabet index, as well as plaintext to ciphertext

 printf("%i", k[u]);


        if (isalpha(p[i]))
        {

            printf("%c", c[i]);
        }
        else if (p[i] == 32)
        {
            printf(" "); // to leave spaces as they are
        }

        else
        {
            printf("%c", (p[i])); //to leave non alphaetic characters as they are
        }
    }

    printf("\n");

}

int shift(char q) //  defining shift function

{

int keyword;


    if (islower(q))
    {

     keyword = ((int) (q)) -97;
    }

    else
    {
         keyword = ((int) (q)) -65;
    }

    return keyword;
}