/////////////////////////////////////////////////////////////////////////////
//
//  This file is Copyright 1992,1993 by Warwick W. Allison.
//  This file is part of the gem++ library.
//  You are free to copy and modify these sources, provided you acknowledge
//  the origin by retaining this notice, and adhere to the conditions
//  described in the file COPYING.LIB.
//
/////////////////////////////////////////////////////////////////////////////

#include "gemt.h"
#include "gema.h"

GEMtimer::GEMtimer(GEMactivity& in, int millisec) :
	interval(millisec), mytime(now+interval)
{
	if (!act) (act=&in)->SetTimer(this);
	InsertInto(head);
}

GEMtimer::~GEMtimer()
{
	if (head==this && !next) {
		act->SetTimer(0);
		act=0;
	} else {
		DeleteFrom(head);
	}
}

// Below for service provider
int GEMtimer::NextInterval()
{
	if (head)
		return head->mytime-now;
	else
		// WAIT A SEC!  THIS SHOULDN'T HAPPEN!
		return 1000;
}

GEMfeedback GEMtimer::ExpireNext(const GEMevent& e)
// Expire() the next GEMtimer and any equal to it.
{
	GEMfeedback result=ContinueInteraction;
	now=head->mytime;
	while (head->mytime <= now && result!=EndInteraction) {
		result=head->Expire(e);
		head->mytime+=head->interval+1; // So interval==0 doesn't lock or starve the scheduler.
		GEMtimer* toinsert=head;
		head=head->next;
		toinsert->InsertInto(head);
	}
	return result;
}


GEMactivity* GEMtimer::act=0;
GEMtimer* GEMtimer::head=0;
int GEMtimer::now=0;

void GEMtimer::InsertInto(GEMtimer*& list)
// Insert self into the given list in order of increasing mytime.
{
	if (list) {
		if (list->mytime > mytime) {
			next=list;
			list=this;
		} else {
			InsertInto(list->next);
		}
	} else {
		next=list;
		list=this;
	}
}

void GEMtimer::DeleteFrom(GEMtimer*& list)
// Delete self from the given list
{
	if (list) {
		if (list==this) {
			list=next;
		} else {
			DeleteFrom(list->next);
		}
	}
}