/******************************************************************************

                              Online C++ Compiler.
               Code, Compile, Run and Debug C++ program online.
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*******************************************************************************/

#include <iostream>
#include <fstream>

std::string getCardString() {
    std::string userInput{""};

    std::cout << "Please enter a card number :: " << std::endl;
    std::getline(std::cin, userInput);

    return userInput;
}

std::string removeNondigitCharacters(std::string &userInputUnfiltered) {
    std::string filteredInput{""};

    for(char &c : userInputUnfiltered) {
        if(isdigit(c))
            filteredInput += c;
    }

    return filteredInput;
}

bool luhnCheck(std::string userInput) {
    int sum{0};
    int currentNumber{0};

    for(int i = 0; i < userInput.length(); i++) {
        currentNumber = userInput[i]-48;

        if(i==0 || i%2==0) {
            if(currentNumber*2>=10)
                sum+=currentNumber/10+currentNumber%10;
            else
                sum+=currentNumber;
        } else
            sum+=currentNumber;

    }

    if(sum%10!=0)
        return true;
    return false;
}

void appendToFile(std::string &userInput, std::string fileName) {
    //creating a stream to open files with
    std::ofstream fileToAppend;
    //opening a file and creating one if there isnt one
    fileToAppend.open(fileName, std::ios_base::app);
    //appending the users card to the file
    fileToAppend << userInput << "\n";
    //closing the file to prevent data leaks
    fileToAppend.close();

}



int main () {
    bool anotherCard = true;

    while(anotherCard) {
        std::string answer{""};
        std::string userInput{""};

        userInput = getCardString();

        std::cout << "Pre-Sanitized :: " << userInput << std::endl;

        userInput = removeNondigitCharacters(userInput);
        std::cout << "Sanitized :: " << userInput << std::endl;

        if(luhnCheck(userInput)) {
            std::cout << "VALID - " << userInput << std::endl;
            appendToFile(userInput, "valid_cards.txt");
        } else {
            std::cout << "INVALID - " << userInput << std::endl;
            appendToFile(userInput, "invalid_cards.txt");
        }

        std::cout << "Would you like to do another card? (y/n)" << std::endl;
        std::getline(std::cin, answer);
        if(answer == "y" || answer == "Y")
            anotherCard = true;
        else
            anotherCard = false;
    }


    return 0;
}