//C++ 11 or later
#include <thread>
#include <chrono>         // std::chrono::seconds
#include <vector>
#include <string>
#include <iostream>
using namespace std;

class Observer{
    public:
	virtual void Update(char c)=0;
};

class Subject{
  public:
	int 	SleepInSeconds;
	int 	N;
    char 	C;
    Subject(char c,int n,int sleepInSeconds):C(c),N(n),SleepInSeconds(sleepInSeconds){
	}
	virtual void Attach(Observer& observer)=0;
	virtual bool Detach(Observer& observer)=0;
	virtual void Notify()=0;
};

void EventTriggerer(Subject* ps) {//The thread function
	for(int i=0;i<ps->N;i++){
		ps->Notify();
		this_thread::sleep_for(chrono::seconds(ps->SleepInSeconds));
	}
}

class CSubject:public Subject{
	thread	t;
    vector<Observer*> observers;
  public:
    void Attach(Observer& observer){
    	observers.push_back(&observer);
	}
	bool Detach(Observer& observer){
		for (auto iter = observers.begin(); iter != observers.end(); iter++) {
        	if (*iter==&observer) {
            	observers.erase(iter);
            	return true;
        	}
        }
		return false; 
    }
	CSubject(char c,int n, int sleepInSeconds):Subject(c,n,sleepInSeconds){
	}
	void StartSimulation(){
		t = thread(EventTriggerer, this);
	}
	void Join(){
		t.join();
	}
	void Notify(){
		for (auto &observer : observers) {
			observer->Update(C); 
		}
	}
};

class CObserver:public Observer{
public:
	string Name;
	CObserver(string name):Name(name){ 
		//cout<<name<<":";
	}
    void Update(char c){
    	string s=Name+"("+c+") ";
		cout<<s;
    }
};

int main(){
	CObserver	A("A");
	CObserver	B("B");
	CSubject x('X',20, 1);	
	CSubject y('Y',10, 2);	
	x.Attach(A);
	x.Attach(B);
	y.Attach(A);
	x.StartSimulation();
	y.StartSimulation();
	this_thread::sleep_for(chrono::seconds(5)); //let the simultation run for a while
	x.Detach(A);
	cout<<"\nDetached A from X\n";
	x.Join();
	y.Join();
	cout<<endl<<"main() ended....."<<endl;
	return 0;
}