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


bool only_digits(string phrase);
int rotate(char c, int i);


int main(int argc, string argv[])
{
    if (argc != 2 || only_digits(argv[1]) == false) {
        printf("Usage: ./caesar key\n");
        return 1;
    } else {
        int key = (atoi(argv[1])) % 26;
        string plain = get_string("plaintext: ");
        int plainlen = strlen(plain);
        int cypher[plainlen];
        printf("ciphertext: ");
        for (int i = 0; i < plainlen; i++) {
            cypher[i] = rotate(plain[i], key);
            printf("%c", cypher[i]);
        }
        printf("\n");
    }
}


bool only_digits(string phrase) {
    for (int i = 0; phrase[i] != '\0'; i++) {
        if (47 > phrase[i] || phrase[i] > 58) {
            return false;
        }
    }
    return true;
}


int rotate(char c, int i) {
    if ((64 < c && c < 91) || (96 < c && c < 123)) {
        c += i;
        if (64 >= c || (c >= 91 && 96 >= c) || c >= 123) {
            c -= 26;
        }
    }
    return c;
}



/*
Your program must accept a single command-line argument, a non-negative integer. Let’s call it *k*
    for the sake of discussion.
If your program is executed without any command-line arguments or with more than one command-line
    argument, your program should print an error message of your choice (with printf) and return from
    main a value of 1 (which tends to signify an error) immediately.
If any of the characters of the command-line argument is not a decimal digit, your program should print
    the message Usage: ./caesar key and return from main a value of 1.
Do not assume that k will be less than or equal to 26. Your program should work for all non-negative
    integral values of k less than 2^31-26. In other words, you don’t need to worry if your program eventually
    breaks if the user chooses a value for k that’s too big or almost too big to fit in an int. (Recall
    that an int can overflow.) But, even if k is greater than 26, alphabetical characters in your program’s
    input should remain alphabetical characters in your program’s output. For instance, if k is 27, A should
    not become \ even though \ is positions away from A in ASCII, per asciitable.com; A should become B,
    since B is 27 positions away from A, provided you wrap around from Z to A.
Your program must output plaintext: (with two spaces but without a newline) and then prompt the user for
    a string of plaintext (using get_string).
Your program must output ciphertext: (with one space but without a newline) followed by the plaintext’s
    corresponding ciphertext, with each alphabetical character in the plaintext “rotated” by k positions;
    non-alphabetical characters should be outputted unchanged.
Your program must preserve case: capitalized letters, though rotated, must remain capitalized letters;
    lowercase letters, though rotated, must remain lowercase letters.
After outputting ciphertext, you should print a newline. Your program should then exit by returning 0
    from main.
*/