#include <cs50.h>
#include <stdio.h>
#include <math.h>

void Validation(long long int CardID);
int CardOrder(long long int CardID);


int main(int argc, string argv[])
{
    long long int CardID = 4276380162463959  ; //15 digit 378282246310005
    Validation(CardID);

}

int CardOrder(long long int CardID)
{
     for (int i = 0; i <= 20; i++)
         {
             if (CardID/((long long int) pow(10,i)) == 0)
             {
                 return i;
                 break;
             }
         }
    printf("Unknown card ID type");
    return 0;
}

void Validation(long long int CardID)
{
    int ValidationValue = 0, temp = 0, Order = CardOrder(CardID), identifier = 0;

    for (int i = 1; i <= Order; i++)
    {
        temp = (CardID%(long long int)pow(10,i)/(long long int)pow(10,i-1));
        if (i==Order)
        {
            identifier = temp;
        }
        if (i%2 == 0)
        {
            temp *=2;
            if (temp >= 10)
            {
                temp = temp/10 + temp%10;
            }
        }
        ValidationValue += temp;
    }
    printf("Company: ");
    switch (identifier)
    {
        case 3:
            printf("AMEX\n");
            break;
        case 4:
            printf("VISA\n");
            break;
        case 5:
            printf("MASTERSCARD\n");
            break;
        default:
            printf("Unidentified company\n");
    }
    printf ("ValidationValue: %i\n", ValidationValue);
    if (ValidationValue%10 == 0)
    {

        printf ("VALID\n");
    }
}