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

// Code techniques not taught in CS50 are from previous programming experience

int main(int argc, string argv[])
{
    // If the user passes the correct amount of arguments...
    if (argc == 2)
    {
        // Convert the user's argument into an int named argPassed
        int argPassed = atoi(argv[1]);
        // ...receive input for string plainText
        printf("plaintext: ");
        string plainText = get_string();

        printf("ciphertext: ");

        // Constrain the key to 26 value
        argPassed = argPassed % 26;

        // ...for each character in the string typedName...
        for (int i = 0; i < strlen(plainText); i++)
        {
            // ...create char variable "plainChar" with that chararcter
            char plainChar = plainText[i];

            // ...if the character is not a letter...
            if (plainChar > 'z' || plainChar < 'A')
            {
                // ...print that character
                printf("%c", plainChar);
            }
            // ...if character + argument <= z/Z and >= a/A...
            else if ((plainChar + argPassed <= 'z' && plainChar + argPassed >= 'a') || (plainChar + argPassed <= 'Z' && plainChar + argPassed >= 'A'))
            {
                // ...print the user's input + argument
                printf("%c", plainChar + argPassed);
            }
              // ...if character + argument > z or > Z but < a
            else if ((plainChar + argPassed > 'z') || (plainChar + argPassed > 'Z' && plainChar + argPassed < 'a'))
            {
                printf("%c", plainChar + argPassed - 26);
            }
        }
        // End on a new line
        printf("\n");
    }
    else
    {
        // Print an error and return 1 if the user enters an incorrect amount of arguments
        printf("Please enter an argument in the form of a single integer.\n");
        return(1);
    }
}