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

int main(int argc, string argv[])

{
    char *key = argv[1];
    char n;
    int newkey;

    //rejects too many arguments
    if (argc != 2)
    {
        printf("./caesar key\n");
        return 1;
    }
    // converts char key into int newkey
    for (int i = 0; n = strlen(key), i < n; i++)
    {
        if isdigit(key[i])
        {
            newkey = atoi(key);

        }
        // rejects letters
        else
        {
            printf("./caesar key\n");
            return 1;
        }
    }
    // gets plaintext from user

    char *plain = get_string("plaintext: ");
    // prints modded cipher text

    printf("ciphertext: ");
    for (int i = 0; n = strlen(plain), i < n; i++)
    {
        // checks case
        if (isupper(plain[i]))
        {
            int plainupper = (plain[i] - 65);
            int ciphupper = (plainupper + newkey) % 26;
            char fintext = (ciphupper + 65);
            printf("%c", fintext);
        }
        // checks case
        if (islower(plain[i]))
        {
            int plainlower = (plain[i] - 97);
            int ciphlower = (plainlower + newkey) % 26;
            char finntext = (ciphlower + 97);
            printf("%c", finntext);
        }
        else
            // prints whatever was typed if it isnt upper or lower case
        {
            printf("%c", plain[i]);
        }

    }
    printf("\n");
}