import java.util.Scanner;

/**
 * This program calculates gratuity for a purchase based on the purchase amount and gratuity rate.
 * Solution to programming exercise 5 from chapter 2 from page 70.
 *
 *  Here is the pseudocode :
 *
 *  gratuity rate <- prompt user for validated double input using try/catch
 *  purchase amount <- prompt user for validated double input using try/catch
 *
 *  gratuity amount <- purchase amount * gratuity rate/100
 *  purchase total <- gratuity amount + purchase amount
 *
 *  Inform the user of their gratuity amount and total amount, allow user to run program again if they press "0'
 *
 */
public class U1_Problem5 {

    public static void main(String[] args){
        while(true) {
            interactWithUser();
            Scanner scan = new Scanner(System.in);
            System.out.print("Please press 0 if you would like to go again.   ");
            if (scan.nextInt() != 0){
                break;
            }
        }

        System.out.println("Goodbye!");

    }

    private static void interactWithUser(){
        calculateAndDisplayTotal(
                getDouble("Please enter amount spent!"),
                getDouble("Please enter gratuity rate!")
        );
    }

    // Use try/catch to receive a validated double as input to a prompt.
    private static double getDouble(String prompt) {
        double amount = 0;
        String currentInput;
        boolean amountSelected = false;
        Scanner scan = new Scanner(System.in);

        while (!amountSelected) {
            System.out.print(prompt + "  ");
            currentInput = scan.nextLine();
            try {
                amount = Double.valueOf(currentInput);
                amountSelected = true;
            } catch (NumberFormatException e) {
                System.out.println(
                        "Sorry, I can only understand if you enter a single number, not " + currentInput +
                        ". Please try again!"
                );
            }
        }

        return amount;
    }

    // Calculate gratuity amount and total amount based of amount spent and gratuity percentage.
    // Inform user of gratuity amount and total amount spent.
    private static void calculateAndDisplayTotal(double amountSpent, double gratuityPercentage){

        double gratuity = amountSpent * gratuityPercentage/100;
        double total = amountSpent + gratuity;

        System.out.println(
                "Since you spent " + amountSpent + " with a gratuity rate of " + gratuityPercentage + "%," +
                " your gratuity is " + gratuity + " and your total is " + total + "!"
        );
    }