#include <stdio.h>
#include <stdlib.h>
#include <math.h>


// declare our global vars that will be shared through out the program's functions
int *digits;
long cardNum;
long firstDigit; // yeah this should be an int, but im lazy to convert, TODO adress later
int secondDigit;
int numberOfDigits;
int *evenIndexDigits;
int *oddIndexDigits;

int evenIndexSum = 0;
int oddIndexSum = 0;

void reverseArray(int arrStart, int arrEnd)
{
    int moverStorage;
    while (arrStart < arrEnd)
    {
        moverStorage = digits[arrStart];
        digits[arrStart] = digits[arrEnd];
        digits[arrEnd] = moverStorage;
        arrStart++;
        arrEnd--;
    }

}

// gets input
void getInput(void)
{
    // checks input and passes it through a validator, if is valid, return value
    cardNum = get_long("Enter a credit card number: "); // this function is a myth, pretend its scanf
    numberOfDigits = floor(log10(cardNum));
    printf("%d\n", numberOfDigits);
    firstDigit = cardNum;
    while (firstDigit >= 10)
    {
        firstDigit /= 10;
    }
     if (numberOfDigits < 13 || numberOfDigits > 16)
    {
        printf("INVALID check number size!\n");
        exit(0);
    }
    digits = calloc(numberOfDigits, sizeof(int));
    for (int i = 0; i <= numberOfDigits; i++)
    {
        digits[i] = cardNum % 10;
        cardNum /= 10;
    }

    reverseArray(0, numberOfDigits);
    secondDigit = digits[1];
}

void parse(void)
{
    // the big gay region
    numberOfDigits += 1;
    if (numberOfDigits % 2 == 0)
    {
        evenIndexDigits = calloc(8, sizeof(int));
        oddIndexDigits = calloc(8, sizeof(int));

        int evenCounter = 0;
        int oddCounter = 0;
        printf("Card is 16 digits long starting from 1\n");
        for (int i = 0; i < numberOfDigits; i++)
        {
            if (i % 2 == 0)
            {
                evenIndexDigits[evenCounter] = digits[i] * 2;
                evenCounter++;
                //printf("%d\n", digits[i] * 2);
            }
            else
            {
                oddIndexDigits[oddCounter] = digits[i];
                oddCounter++;
            }
        }
    }
    else
    {
        // ignore this, pretend its like whats above in the else block
        printf("Card is 15 digits long starting from 1\n");
        for (int i = 0; i < numberOfDigits; i++)
        {
            if (i % 2 != 0)
            {
                evenIndexSum += digits[i] * 2;
              //  printf("%d\n", digits[i] * 2);
            }
            else
            {
                oddIndexSum += digits[i];
                printf("%d\n", digits[i]);
            }
        }
    }
}

// this function is a myth
string checkValidity(void)
{
    return "i dont exist";
}


int main(void)
{
    getInput();
    //string res = checkValidity();
    parse();
    printf("evenIndex\n");
    for (int i = 0; i < sizeof(evenIndexDigits); i++)
    {
        printf("%d\n", evenIndexDigits[i]);
    }

    printf("oddIndex\n");
    for (int i = 0; i < sizeof(oddIndexDigits); i++)
    {
        printf("%d\n", oddIndexDigits[i]);
    }
    printf("\nEvenIndexSum: %d  OddIndexedSum: %d\n", evenIndexSum, oddIndexSum);

    free(digits);
    free(evenIndexDigits);
    free(oddIndexDigits);
}