#include "tween.h"

#include <string.h>

/*
Copyright (c) 2013-2021 Devine Lu Linvega
2018 web port by rezmason
2021 C89 port by rezmason

Permission to use, copy, modify, and distribute this software for any
purpose with or without fee is hereby granted, provided that the above
copyright notice and this permission notice appear in all copies.

THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
WITH REGARD TO THIS SOFTWARE.
*/

void
Tween_Update(Tween *tween, double now)
{
	double t;
	int complete = 0;
	if(tween->duration <= 0) {
		return;
	}
	t = (now - tween->start) / tween->duration;
	if(t <= 0) {
		t = 0;
	} else if(t >= 1) {
		t = 1;
		complete = 1;
		tween->duration = -1;
	}
	tween->value = t * tween->endValue + (1. - t) * tween->startValue;

	if(complete && tween->onComplete != NULL) {
		void (*onComplete)(void) = tween->onComplete;
		tween->onComplete = NULL;
		onComplete();
	}
}

void
Tween_Start(Tween *tween, double startValue, double endValue, double start, double duration, void (*onComplete)(void))
{
	tween->startValue = startValue;
	tween->endValue = endValue;
	tween->start = start;
	tween->duration = duration;
	tween->onComplete = onComplete;
}

void
Tween_Stop(Tween *tween, int complete)
{
	tween->duration = -1;
	if(complete) {
		tween->value = tween->endValue;
	}
}