Source.cpp

//https://dnschecker.org/credit-card-validator.php
//https://www.testingdocs.com/displaying-a-table-of-values-in-c-program/
#include <iostream>
#include <sstream>
using namespace std;



//Check if number or string 
bool check_number(string str) {
	for (int i = 0; i < str.length(); i++)
		if (isdigit(str[i]) == false)
			return false;
	return true;
}

//Count number of digits
int countDigit(long long n)
{
	if (n == 0)
		return 1;
	int count = 0;
	while (n != 0) {
		n = n / 10;
		++count;
	}
	return count;
}

//Find the last digit
int lastDigit(int n)
{
	return (n % 10);
	cout << lastDigit;
}

int majorIndustryIdentifierLookUp(int m)
{
	return (m % 10);
}

string majorIndustryIdentifier[10] = { "ISO_and_other_industry_duties",
"Airlines", "Airlines, finance, and other future industry duties",
"Travel and leisure", "Banking and finance", "Finance and banking",
"Sales and banking/finance", "Petroleum and other future industry tasks",
"Healthcare, telecommunications, and other future industry tasks",
"For the appointment of national standards bodies" };
string card_no;

int main() {

	cout << "Type your credit card number: ";
	cin >> card_no;

	//0. Check if user input is int only 
	bool initializer = true;
	while (initializer) {
		if (check_number(card_no)) {
			cout << card_no << " is an integer." << endl;

			//Output the card number as an integer (back from string)
			stringstream stream(card_no);
			long long card_no_int;
			stream >> card_no_int;
			long long n = card_no_int;

			//1. Check if the input has the right number of digits
			int dgts = countDigit(n);
			cout << "Number of digits : " << dgts << "\n";

			if (dgts == 16 || dgts == 17) {
				cout << "The credit card is valid." << endl;
				initializer = false;
			}
			else {
				cout << "Number of digits is not correct. " << endl;
				goto jump;
			}
		}
		else {
			cout << card_no << " is a string. " << endl;
		jump:
			cout << "Input a proper credit card number or exit with 'x'. \n" << endl;
			cout << "Type your credit card number: "; // Type a number and press enter
			cin >> card_no; // Get user input 
			if (card_no == "x");
		
		}

		//1. Major industry identifier (MII)
		

	}




	//1. Major industry identifier (MII) (OSKAR)
		/*
		Create a list with MII categories assigned to numbers 0-9. Spit out the correct category based on the first digit of card_no
		*/
	


	//2. BIN/IIN (Bank/Issuer Identification Number)

	//3. Personal account number

	//4. Luhn Algorithm
			/*
			Example: 347609692102916
			1. Take last digit: 6
			*/
			//int last_d = lastDigit(card_no_int);
			//cout << last_d << " is the last digit." << endl;
			/*
				2. Take the rest of the sequence: 34760969210291
				3. Double every other digit starting from the right 3,8,7,12,0,18,6,18,2,2,0,4,9,2.
				4. Sum the digits of the products 12 = 1 + 2 = 3, same with 18 that gives you 9
				5. Add all the digits together 3+8+7+3+0+9+6+9+2+2+0+4+9+2 = 64
				6. Multiply the result by 9, 64 * 9 = 576
				7. Take the last digit of the result 6. If this matches the check digit, then we have a valid sequence.
				8.Since our check digit 6 matches our result 6, we conclude that this sequence is a valid credit card number.
				*/

	//5. Credit card prefix numbers (OSKAR)
		/*
		Create a list with credit card issuers assigned to prefix numbers. Spit out the correct credit card issuer.
		*/

}