//
//	class event
//		execution event in a discrete event driven simulation
//
//	Described in Chapter 15 of
//	Data Structures in C++ using the STL
//	Published by Addison-Wesley, 1997
//	Written by Tim Budd, budd@cs.orst.edu
//	Oregon State University
//

class event {
public:
		// constructor requires time of event
	event (unsigned int t) : time(t) { }

		// time is a public data field
	unsigned int time;

		// execute event by invoking this method
	virtual void processEvent() { }
};

class eventComparison {
public:
	bool operator () (event * left, event * right) 
		{ return left->time > right->time; }
};

class simulation {
public:
	simulation () : eventQueue(), currentTime(0) { }

	void scheduleEvent (event * newEvent)
		{ eventQueue.push (newEvent); }

	void run();

	unsigned int currentTime;

protected:
	priority_queue<vector<event *>, eventComparison> eventQueue;
};

void simulation::run()
	// execute events until event queue becomes empty
{
	while (! eventQueue.empty()) {
		event * nextEvent = eventQueue.top();
		eventQueue.pop();
		currentTime = nextEvent->time;
		nextEvent->processEvent();
		delete nextEvent;
		}
}