//FADER: INTERVAL IN MILLISECONDS - SHOULD BE MADE LARGER IF THERE ARE PERFORMANCE ISSUES

Fade.INTERVAL_MILLIS = 50;

function Fade (element, rate, initialOpacity, minOpacity, maxOpacity) {
	this._element = element;
	this._intervalId = null;
	this._rate = rate;
	this._isFadeOut = true;

	this._minOpacity = 0;
	this._maxOpacity = 99;
	this._opacity = 99;

	if (typeof minOpacity != 'undefined') {
		if (minOpacity < 0)
			this._minOpacity = 0;
		else if (minOpacity > 99)
			this._minOpacity = 99;
		else
			this._minOpacity = minOpacity;
	}
	if (typeof maxOpacity != 'undefined') {
		if (maxOpacity < 0)
			this._maxOpacity = 0;
		else if (maxOpacity > 99)
			this._maxOpacity = 99;
		else
			this._maxOpacity = maxOpacity;
	}
	if (this._maxOpacity < this._minOpacity)
		this._maxOpacity = this._minOpacity;
	if (typeof initialOpacity != 'undefined') {
		if (initialOpacity > this._maxOpacity)
			this._opacity = this._maxOpacity;
		else if (initialOpacity < this._minOpacity)
			this._opacity = this._minOpacity;
		else
			this._opacity = initialOpacity;
	}
	if(typeof element.style.opacity != 'undefined')
		this._updateOpacity = this._updateOpacityW3c;
	else if (typeof element.style.filter != 'undefined') {
		if (element.style.filter.indexOf("alpha") == -1) {
			var existingFilters="";
			if (element.style.filter)
				existingFilters = element.style.filter+" ";
			element.style.filter = existingFilters+"alpha(opacity="+this._opacity+")";
		}
		this._updateOpacity = this._updateOpacityMSIE;
	}
	else
		this._updateOpacity = this._updateVisibility;
	this._updateOpacity();
}
//INITIATES A FADE-OUT
Fade.prototype.fadeOut = function () {
	this._isFadeOut = true;
	this._beginFade();
}
//INITIATES A FADE-IN
Fade.prototype.fadeIn = function () {
	this._isFadeOut = false;
	this._beginFade();
}
//MAKES THE ELEMENT COMPLETELY OPAQUE - STOPS ANY FADE IN PROGRESS
Fade.prototype.show = function () {
	this.haltFade();
	this._opacity = this._maxOpacity;
	this._updateOpacity();
}
//MAKES THE ELEMENT COMPLETELY TRANSPARENT - STOPS ANY FADE IN PROGRESS
Fade.prototype.hide = function () {
	this.haltFade();
	this._opacity = 0;
	this._updateOpacity();
}
//HALTS ANY FADE IN PROGRESS
Fade.prototype.haltFade = function () {
	clearInterval(this._intervalId);
}
//RESUMES A FADE WHERE IT WAS HALTED
Fade.prototype.resumeFade = function () {
	this._beginFade();
}
//PSEUDO PRIVATE MEMBERS
Fade.prototype._beginFade = function () {
	this.haltFade();
	var objref = this;
	this._intervalId = setInterval(function() { objref._tickFade(); },Fade.INTERVAL_MILLIS);
}
Fade.prototype._tickFade = function () {
	if (this._isFadeOut) {
		this._opacity -= this._rate;
		if (this._opacity < this._minOpacity) {
			this._opacity = this._minOpacity;
			this.haltFade();
		}
	}
	else {
		this._opacity += this._rate;
		if (this._opacity > this._maxOpacity ) {
			this._opacity = this._maxOpacity;
			this.haltFade();
		}
	}
	this._updateOpacity();
}
Fade.prototype._updateVisibility = function () {
	if (this._opacity > 0)
		this._element.style.visibility = 'visible';
	else
		this._element.style.visibility = 'hidden';
}
Fade.prototype._updateOpacityW3c = function () {
	this._element.style.opacity = this._opacity/100;
	this._updateVisibility();
}
Fade.prototype._updateOpacityMSIE = function () {
	this._element.filters.alpha.opacity = this._opacity;
	this._updateVisibility();
}
Fade.prototype._updateOpacity = null;