import java.util.Scanner;
public class Main {
	public static void main(String args[]){
		Scanner sc = new Scanner(System.in);
		boolean run = false;

		do{
			System.out.println
			("Enter Credit Card Number:");
			String asknumber = sc.next();
			int cclen = asknumber.length();
			boolean oddeven = deterOdEv(cclen);
			int[] ccnum = splitCC(asknumber, cclen);
			char[] charcc = splitSecureCC(asknumber, cclen);
			byte ctype = findType(ccnum);
			boolean valid = calcLahn(ccnum, cclen, oddeven);
			printVerdict(ctype, valid, charcc, cclen);
			run = deterRestart();
		}while(run == true);
	}

	public static boolean calcLahn(int[] ccnum, int digits, boolean oddeven){
		int[] dubccnum = new int[digits+1];
		boolean valid;
		int start;
		int ftest;
		int tadd;
		double totlnum = 0;

		if(oddeven == true){
			start = 2;
			tadd = 0;
			ftest= 1;
		}else{
			start = 1;
			tadd = 1;
			ftest= 0;
		}
		for (int i = start; i <= ccnum.length-2; i +=2){
			if (ccnum[i] <=4){
				dubccnum[i] = ccnum[i] * 2;
			}else if (ccnum[i] >4){
				int tempnu1 = ccnum[i] * 2;
				int tempnu2 = tempnu1 % 10;
				tempnu1 /= 10;
				int tempnu3 = tempnu1 % 10;
				dubccnum[i] = tempnu3;
				dubccnum[i+1] = tempnu2;
			}
		}
		for (int i = start; i <= ccnum.length-1; i++){
			System.out.print(dubccnum[i]);
		}
		for (int i = 1; i <= ccnum.length-1; i+=2){
			int tempnu = dubccnum[i + ftest] + dubccnum[i + ftest + 1] + ccnum[i + tadd];
			totlnum+=tempnu;
			System.out.println
			(totlnum);
		}
		if (totlnum % 10 == 0){
			System.out.println
			("This is valid");
			valid = true;
		}else{
			System.out.println
			("This is invalid");
			valid = false;
		}
		return valid;
	}
	public static int[] splitCC(String asknumber, int cclen){
		long longccnum = Long.parseLong(asknumber);
		int[] ccnum = new int[cclen + 1];
		for (int i = ccnum.length-1; i >= 1; i--){
			long digit = longccnum % 10;
			ccnum[i] = ((int)digit);
			longccnum /= 10;
			System.out.println(ccnum[i]);
		}
		System.out.println
		("The Number Entered is: ");
		for (int i = 1; i <= ccnum.length-1; i++){
			System.out.print(ccnum[i]);
		}
		System.out.println
		("\n");
		return ccnum;
	}
	public static char[] splitSecureCC(String asknumber, int cclen){
		char symbol = 42;
		char[] charcc = new char[cclen];
		char[] ccsec = new char[cclen];
		for(int i = 0; i < cclen; i++){
			charcc[i] = asknumber.charAt(i);
		}
		for(int i = 0; i < cclen-4; i++){
			ccsec[i] = symbol;
		}
		for(int i = cclen-4; i < cclen; i++){
			ccsec[i] = charcc[i];
		}
		return ccsec;
	}
	public static byte findType(int[] ccnum){
		int prefix = (ccnum[1]*1000) + (ccnum[2]*100) + (ccnum[3]*10) + (ccnum[4]*1);
		byte ctype;

		System.out.println
		("Prefix is: " + prefix);
		if (prefix >= 5100 && prefix <=5500){
			System.out.println
			("This is a MasterCard");
			ctype = 1;
		}else if (prefix >= 4000 && prefix <=4999){
			System.out.println
			("This is a Visa");
			ctype = 2;
		}else if (prefix == 6011){
			System.out.println
			("This is a Discover");
			ctype = 3;
		}else if (prefix >= 3400 && prefix <=3700){
			System.out.println
			("This is an Amercan Express");
			ctype = 4;
		}else{
			System.out.println
			("Please Enter Valid Number");
			ctype = 0;
		}
		return ctype;
	}
	public static boolean deterOdEv(int cclen){
		boolean oddeven;
		if(cclen % 2 == 0){
			oddeven = false;
		}else{
			oddeven = true;
		}
		return oddeven;
	}
	public static void printVerdict(byte ctype, boolean valid, char[] charcc, int cclen){
		System.out.println
		("The Credit Card Number is:\n");
		try{
			for(int i = 0; i < cclen; i++){
				System.out.print(charcc[i]);
			}
		}finally{
			System.out.println("");
		}
		switch(ctype){
			case 0: System.out.println("The Card Type Does Not Match Any Stored Types"); break;
			case 1: System.out.println("This is a MasterCard."); break;
			case 2: System.out.println("This is a Visa."); break;
			case 3: System.out.println("This is a Discover."); break;
			case 4: System.out.println("This is an American Express."); break;
		}
		if(valid == true){
			System.out.println("This Card is Valid");
		}else{
			System.out.println("This Card is NOT Valid");
		}
	}
	public static boolean deterRestart(){
		boolean restart;
		Scanner sc = new Scanner(System.in);
		System.out.println("Would you like to restart?");
		String askrestart = sc.next();
		if(askrestart.equalsIgnoreCase("Yes") || askrestart.equalsIgnoreCase("Y")){
			restart = true;
		}else{
			restart = false;
		}
		return restart;
	}
}