import java.util.Scanner;

public class heartMonitor {
    /**
     * Task: Make the necessary changes in this code to run the statement
     * 
     * System.out.println("Invalid option. Inform age and heart rate first.");
     * 
     * if the user selects options 3, 4, or 5 before entering
     * their age and heart rate correctly.
     */
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int choice = 0;
        // User age, in years
        int age = 0;
        // Current user heart rate
        int heartRate = 0;
        // Three consecutive heart rate measurements
        int hr1, hr2, hr3;
        while (choice != 6) {
            System.out.println("\n Heart Monitor Menu:");
            System.out.println("1. Enter age");
            System.out.println("2. Enter heart rate");
            System.out.println("3. Compute maximum heart rate");
            System.out.println("4. Compute heart rate zone");
            System.out.println("5. Compute heart rate variation");
            System.out.println("6. Exit");

            System.out.print("Enter your choice (1-6): ");
            choice = scanner.nextInt();

            if (choice == 1) {
                System.out.print("Enter your age [2-150]: ");
                age = scanner.nextInt();
                if (checkAge(age))
                    System.out.println("You are " + age + " years old.");
                else {
                    System.out.println("Invalid value. Try again.");
                    age = 0;
                }
            } else if (choice == 2) {

                System.out.print("Enter your heart rate [40-220]: ");
                heartRate = scanner.nextInt();
                if (checkHeartRate(heartRate))
                    System.out.println("Your current heart rate is " + heartRate + ".");
                else {
                    System.out.println("Invalid value. Try again.");
                    heartRate = 0;
                }
            } else if (choice == 3) {
                System.out.println("Your maximum heart rate is " + maximumHeartRate(age) + ".");

            } else if (choice == 4) {
                System.out.println("Your heart rate zone is " + heartRateZone(age, heartRate));

            } else if (choice == 5) {
                System.out.print("Enter three heart rate measurement separated by a space: ");
                hr1 = scanner.nextInt();
                hr2 = scanner.nextInt();
                hr3 = scanner.nextInt();
                System.out.println("Your heart rate is " + heartRateVariation(hr1, hr2, hr3) + ".");
            }

            else if (choice == 6)
                System.out.println("Exiting the program. Goodbye!");

            else
                System.out.println("Invalid choice. Please enter a number between 1 and 5.");

        }
        scanner.close();

    }

    /**
     * A valid age is a number in the inverval [2,150]
     * If the user inputs an invalid number return false.
     * If the age is valid, return true.
     */
    public static boolean checkAge(int ag) {
        // Implement checkAge

        return false;
    }

    /**
     * A valid heart rate is a number in the inverval [40,220].
     * If the user inputs an invalid number return false.
     * If the heart rate is valid, return true.
     */
    public static boolean checkHeartRate(int hr) {
        // Implement checkHeartRate

        return false;
    }

    // Task: compute user's maximum heart rate
    // and return an integer number
    // The maximum heart rate is compute as:
    // maximumHeartRate = 220 - age
    public static int maximumHeartRate(int age) {
        // Implement maximumHeartRate
        int mhr = 0;
        return mhr; // Replace with actual result
    }

    /**
     * Task: compute user's heart rate zone.
     * The heart rate zone is a number in the
     * interval [1-5] according to the following rules:
     * zone = 1, if current heart rate is less than 60% of the maximum heart rate
     * zone = 2, if current heart rate is greater than or equal to 60% and less than
     * 70% of the maximum heart rate
     * zone = 3, if current heart rate is greater than or equal to 70% and less than
     * 80% of the maximum heart rate
     * zone = 4, if current heart rate is greater than or equal to 80% and less than
     * 90% of the maximum heart rate
     * zone = 5, if current heart rate is greater than or equal to 90% of the
     * maximum
     */
    public static int heartRateZone(int age, int hr) {
        // Implement heartRateZone
        int zone = 0;
        // ...
        return zone; // Return the actual zone
    }

    // Task: given three measurements of the user's heart rate, hr1, hr2, and, hr3,
    // update the boolean variables: increaseing, decreasing and stable.
    // The variable increasing should be set to true if the input values are
    // strictly increasing
    // The variable decreasing should be set to true if the input values are
    // strictly decreasing
    // The variable stable should be set to true if the input values are all equal.
    public static String heartRateVariation(int hr1, int hr2, int hr3) {
        // Implement heartRateVariation
        boolean increasing = false;
        boolean decreasing = false;
        boolean stable = false;
        // ...

        if (increasing)
            return "increasing";
        else if (decreasing)
            return "decreasing";
        else if (stable)
            return "stable";
        else
            return "oscillating";
    }
}