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

int main(int argc, string argv[])
{
    int key = 0;
    //Check that only one command line argument was entered, otherwhise prompt "Usage: ./caesar key"
    if (argc != 2)
    {
        printf("Usage: ./caesar key\n");
        return 1;
    }
    else
    {
        // loop through the command line arguments
        for (int i = 1; i < argc; i++)
        {
            // loop through the characters of the command line argument
            for (int j = 0, n = strlen(argv[i]); j < n; j++)
            {
                // check whether the given character is a number - if not, print "not a digit key"
                if (!isdigit(argv[i][j]))
                {
                    printf("not a digit key\n");
                    return 1;
                }
            }
            key = atoi(argv[i]);
            //printf("Success\n%i\n", key);
        }
    }
    string ptext = get_string("plaintext:  ");
    printf("ciphertext: ");
    for (int k = 0, n = strlen(ptext); k < n; k++)
    {
        // check if plain text is lowercase and convert the characters
        if islower(ptext[k])
        {
            printf("%c", (((ptext[k] + key) - 97) % 26) + 97);
        }
        // check if plain text is uppercase and convert the characters
        else if isupper(ptext[k])
        {
            printf("%c", (((ptext[k] + key) - 65) % 26) + 65);
        }
        // for any ASCII value outside of a-z and A-Z just print the value without any conversions
        else
        {
            printf("%c", ptext[k]);
        }
    }
    printf("\n");
    return 0;
}