/******************************************************************************
 * This program demonstrates the Luhn Algorithm for credit card validation.
 * 
 * Copyright © 2021 Richard Lesh.  All rights reserved.
 *****************************************************************************/

#undef NDEBUG

#include "Utils.hpp"
#include <clocale>
#include <codecvt>
#include <iostream>
#include <string>
#include <vector>

std::locale utf8loc(std::locale(), new std::codecvt_utf8<wchar_t>);
using namespace Utils;
using namespace std;

static vector<wstring> GOOD_CASES = {L"4321123456789019", L"5432123456789020", L"65432101234567896"};
static vector<wstring> BAD_CASES = {L"4321123456798019", L"4432123456789020", L"65431201234567896"};

bool luhn_check(wstring s) noexcept {
    int checksum = 0;
    int const LENGTH = s.length();
    int const DOUBLE_DIGIT = LENGTH % 2;
    for (auto i = 0; i < LENGTH - 1; ++i) {
        int c = (int)(s[i]) - int(L'0');
        if (i % 2 == DOUBLE_DIGIT) {
            c *= 2;
            if (c > 9) {
                c -= 9;
            }
        }
        checksum += c;
    }
    checksum *= 9;
    checksum %= 10;
    return (int)(s[LENGTH - 1]) - int(L'0') == checksum;
}

int main(int argc, char **argv) {
    setlocale(LC_ALL, "en_US.UTF-8");
    wcout.imbue(utf8loc);
    wcin.imbue(utf8loc);

    wcout << L"Good Test Cases" << endl;
    for (auto s : GOOD_CASES) {
        wcout << s << L" is " << luhn_check(s) << endl;
    }
    wcout << L"Bad Test Cases" << endl;
    for (auto s : BAD_CASES) {
        wcout << s << L" is " << luhn_check(s) << endl;
    }
    return 0;
}