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


//this function checks if the command line argument has any non-alphabetic characters
int valid_command(string cmd);
//this function converts the key to an array of ints that correspond to each character in the key (ex: A or a = 0, B or b = 1, etc.) and returns a pointer to that array
int* convert_key (string cmd);
//calculate the length of the string
int length (string cmd);

int main (int argc, string argv[]){
    //cmd is used as a bool for the following if-statement- It's used to check if the command line argument (key) has any non-alphabetic characters
    int cmd = valid_command(argv[1]);

    //error checking for if the user input more than 2 command line arguments or if the key has any non-alphabetic characters
    if ((argc != 2) || cmd){
        printf("Error: Not valid input!n");
        return 1;
    }
    else{
        printf("plaintext: ");
        string plaintext = get_string();
        int size = length(argv[1]);  //save the length of the key

        //convert key to an array of integers
        int* delta = convert_key(argv[1]);

        int* cipher = (int*)malloc((size+1)*sizeof(int));
        int* cipher_ptr = cipher;
        char* p_ptr = plaintext;

        //go through each character in plaintext, determine if it's an alphabetic character and whether it's in the A-Z range or a-z range and use a calculation based on that to figure out how the character should be encrypted.  This also takes into account wrapping of the key array (if the key array is smaller than plaintext, then once the last character in key is used to encrypt a character in plaintext, the next character should start over from the beginning of key) and also takes into account maintaining the case of the character of plaintext
        if (plaintext != NULL){
            int i = 0;
            while ((*p_ptr) != ''){
                //implement wrapping of key array
                if (i == size){
                    i = 0;
                }
                if (isalpha(*p_ptr)){
                    //if element is in A-Z range:
                    if (isupper(*p_ptr)){
                        *cipher_ptr = ((((*p_ptr)-65)+(delta[i]))%26) + 65;
                        p_ptr++;
                        cipher_ptr++;
                        i++;
                    }
                    else {
                        *cipher_ptr = ((((*p_ptr)-97)+(delta[i]))%26) + 97;
                         p_ptr++;
                        cipher_ptr++;
                        i++;
                    }
                }
                else {
                    //if the character in plaintext is non-alphabetic, just copy that into the cipher array, but don't go on to the next element in key array
                    *cipher_ptr = *p_ptr;
                    p_ptr++;
                    cipher_ptr++;
                }
            }
        }
        else {
            return 1;
        }



        //print out the encrypted ciphertext
        printf("ciphertext: ");

        //put into chars
        char ciphertext [length(plaintext)];

        for (int i = 0; i < length(plaintext); i++){
            ciphertext[i] = *cipher;
            cipher++;
            printf("%c",ciphertext[i]);
        }
        printf("n");

        return 0;
    }

}

//pass in the key string and return a pointer to array of integers that are integer representations of each character in key string
int* convert_key (string cmd){
    char* ptr = cmd;
    int* array = (int*) malloc(strlen(cmd)*sizeof(int));
    int* array_ptr = array;
    while ((*ptr) != ''){
        *array_ptr = (toupper((*ptr))-65);
        ptr++;
        array_ptr++;
    }
    return array;
}

//this function checks if the command line argument has any non-alphabetic character
//return 0 if there are no non-alphabetic characters
//return 1 if there are non-alphabetic characters
int valid_command(string cmd){
    char* ptr = cmd;
    if (ptr != NULL){
        while ((*ptr) != ''){
            int value = (toupper((*ptr))-65);
            if ((value > 25) || (value < 0)){
                return 1;
            }
            else {
                ptr++;
            }
        }
        return 0;
    }
    else{
        return 1;  //return 1 if no command was given
    }
}

int length (string cmd){
    int length = 0;
    char* ptr = cmd;
    while ((*ptr) != ''){
        length++;
        ptr++;
    }
    return length;
}