package me.nluk;

import java.util.List;
import java.util.Scanner;
import java.util.concurrent.Semaphore;
import java.util.stream.Collectors;
import java.util.stream.Stream;

public class Main {
    public static void main(String[] args) throws InterruptedException{
        Semaphore stdio = new Semaphore(1);
        Semaphore inputReady = new Semaphore(2);
        inputReady.drainPermits();
        Input height = new Input("height", stdio, inputReady);
        Input base = new Input("base", stdio, inputReady);
        Output output = new Output(height, base, inputReady);

        List<Thread> threads = Stream.of(output, height, base).map(Thread::new).collect(Collectors.toList());
        threads.forEach(Thread::start);
        for(Thread t : threads){
            t.join();
        }
    }

    public static class Output implements Runnable{
        Semaphore outputSemaphore;
        Input height, base;
        Output(Input height, Input base, Semaphore outputSemaphore){
            this.outputSemaphore = outputSemaphore;
            this.height = height;
            this.base = base;
        }

        @Override
        public void run() {
            try {
                outputSemaphore.acquire(2);
                System.out.println("Result is "+(0.5 * height.input * base.input));
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            finally {
                outputSemaphore.release(2);
            }
        }
    }

    public static class Input implements Runnable{
        Semaphore stdio, inputReady;
        Long input;
        String type;
        Input(String type, Semaphore stdio, Semaphore inputReady){
            this.type = type;
            this.stdio = stdio;
            this.inputReady = inputReady;
        }
        @Override
        public void run() {
            try {
                stdio.acquire();
                System.out.println("Enter "+type+" value: ");
                input = new Scanner(System.in).nextLong();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            finally {
                stdio.release();
                inputReady.release();
            }
        }
    }
}