#include <cs50.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
/*
bool all_alpha(const char *str){

    char c;

    while ((c = *str++) != '\0')
        if (!isalpha(c))
            return false;
    return true;
}*/

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

    string key;
    int textLength;
    string text;
    int shift;
    char symb;


    //if user did not provide an argument
    if (argc == 1 || argc > 2){
        return 1;


    //if argv[1] provided - get a key
    } else {
        key = (argv[1]);
    }

    //get text for encoding
    text = get_string("Enter text: ");
    textLength = strlen(text);

    printf("ciphertext: ");

    //filtering loop
    int j = 0;
    for (int i = 0; i < textLength; i++){

        if (islower[key[j]])
            shift = key[j] - 'a'
        else
            shift = key[j] - 'A'


        if (isaplha(text[i])) {
            if (islower(text[i]))
                symb = ((((text[i] - 'a') + shift) % 26) + 'a');
            else
                symb = ((((text[i] - 'A') + shift) % 26) + 'A');

            printf("%c", symb);
            j++;
        } else
            printf("%c", text[i]);

        if (j == (strlen(key)))
            j=0;
    }

    printf("\n");
}