package com.codepumpkin.behavioral.mediator; 

import java.util.HashSet;

public class Mediator_Design_Pattern_Traffic_Light_Signal_Example {

	public static void main(String[] args) {

		LightMediator lightMediator = new LightMediator();
		Light red = new Light("Red", lightMediator);
		Light green = new Light("Green", lightMediator);
		Light yellow = new Light("Yellow", lightMediator);

		red.turnON();
		green.turnON();
		yellow.turnON();
	}

}

/**
 * 
 * When any light turns ON in traffic Signal, Light Mediator turns OFF other
 * lights.
 *
 */
class LightMediator {

	// Using Hashset to achieve uniqueness in light color.
	HashSet<Light> trafficSignal = new HashSet<>();

	/**
	 * register passed light object in LightMediator It is being called by
	 * constructor of Light class. We can also explicitly call this method.
	 */
	public void registerLight(Light light) {
		trafficSignal.add(light);
	}

	/**
	 * unregisters light from LightMediator
	 */
	public void unRegisterLight(Light light) {
		trafficSignal.remove(light);
	}

	/**
	 * Turns off all the lights other than passed light Object
	 */
	void turnOffAllOtherLights(Light light) {
		for (Light l : trafficSignal) {
			if (!(l.equals(light))) {
				l.turnOFF();
			}
		}
		System.out.println("------------------------------");
	}

	/**
	 * When any light turns ON, it calls this method to notify mediator. Light
	 * mediator will turn OFF all other light by calling
	 * turnOffAllOtherLights(light) method
	 */
	public void notifyMediator(Light light) {
		turnOffAllOtherLights(light);
	}
}

/**
 * Represent light in traffic signal i.e. Red, Green or Yellow light
 */
class Light {

	/**
	 * represents the turn ON and OFF state of light
	 */
	enum State {
		ON, OFF
	}

	private String color;
	private State currentState;
	private LightMediator LightMediator;

	/**
	 * Creates Light object and register it to LightMediator
	 */
	Light(String color, LightMediator LightMediator) {
		this.color = color;
		this.LightMediator = LightMediator;
		LightMediator.registerLight(this);
	}

	/**
	 * Turns ON the light and notify mediator for the same
	 */
	void turnON() {
		currentState = State.ON;
		System.out.printf("%s is turned %s \n", this, currentState.ON);
		LightMediator.notifyMediator(this);
	}

	/**
	 * Turns OFF the light
	 */
	void turnOFF() {
		currentState = State.OFF;
		System.out.printf("%s is turned %s \n", this, currentState.OFF);
	}

	/**
	 * It is generated using its String property color's inbuilt hashcode()
	 * method
	 */
	@Override
	public int hashCode() {
		return color.hashCode();
	}

	/**
	 * Uses its String property color's inbuilt hashcode() method
	 */
	@Override
	public boolean equals(Object obj) {
		Light light = (Light) obj;
		return color.equals(light.color);
	}

	/**
	 * returns light color
	 */
	@Override
	public String toString() {
		return color;
	}
}