var CurrentDomain = 'thommenag.ch';

function ypChaser(sLayerId, iTopOffset, iSlideTime, iCeiling, iFloor) {

	this.chaserDiv = null
	this.layerId   = sLayerId
	this.topOffset = iTopOffset
	this.slideTime = iSlideTime
	this.ceiling   = iCeiling
	this.floor     = iFloor

	ypChaser.registry[ypChaser.registry.length] = this

}

ypChaser.isIE = window.clientInformation ? true : false

ypChaser.isN4 = document.layers ? true : false

ypChaser.isN6	= navigator.appName == "Netscape" && parseInt(navigator.appVersion) >= 5

ypChaser.isO5 = navigator.userAgent.indexOf("Opera") != -1 && parseInt(navigator.appVersion) >= 4

ypChaser.registry = new Array( )

ypChaser.callRate = 10

window.setInterval("ypChaser.timer( )", ypChaser.callRate)

// this is the main loop of the program. To avoid having multiple timers
// running concurrently (CPU-intensive) this goes through ypChaser.registry[ ]
// and calls the .main( ) method of each instance of ypChaser in turn.

ypChaser.timer = function() {

	for (var i = 0; chObj = this.registry[i]; i++) {

		if (!chObj.chaserDiv) chObj.attemptLoad()

		if (chObj.chaserDiv)  chObj.main()
	}
}

// attempts to find the target layer.
// sets the chaserDiv property of the parent object to
// found layer, or null if none is found.

ypChaser.prototype.attemptLoad = function() {

	var chDiv = null

	if (ypChaser.isN6 || ypChaser.isO5)	chDiv = document.getElementById(this.layerId)

	else if (ypChaser.isIE)			chDiv = document.all[this.layerId]

	else if (ypChaser.isN4)			chDiv = document.layers[this.layerId]

	if (chDiv && chDiv != null) 
	{
		this.chaserDiv = chDiv
	}
}

// Main function. gets called very often by ypChaser.timer().
// Updates targetY, and decides whether to start
// the animation over again, continue an existing animation,
// or do nothing at all.

ypChaser.prototype.main = function( )

{
	this.currentY	= this.getCurrentY()

	var scrollTop	= ypChaser.getWindowScroll() 

	var newTargetY	= scrollTop + this.topOffset

	var floor		= ypChaser.getDocumentHeight() - this.floor

	newTargetY = Math.max( newTargetY, this.ceiling)

	if (!ypChaser.isO5) newTargetY = Math.min(newTargetY, floor)

	if ( this.currentY != newTargetY ) {

		if ( newTargetY != this.targetY ) {

			this.targetY = newTargetY

			this.slideInit( )
		}
		this.slide( )
	}
}


// .slideInit( ). Initializes the slide animation.

ypChaser.prototype.slideInit = function( )

{
	this.A		= (this.targetY - this.currentY) / this.slideTime / this.slideTime

	this.startT	= (new Date()).getTime()

	this.startP	= this.getCurrentY()

	this.D		= this.targetY - this.startP
}


// .slide( ). Moves the Chaser one frame. Its rate decreases and
// is defined by a sine wave.

ypChaser.prototype.slide = function( )

{
	var elapsed	= (new Date()).getTime() - this.startT

	if (elapsed < this.slideTime) {

		this.moveTo(this.D - (Math.round(Math.pow(this.slideTime - elapsed, 2) * this.A)) + this.startP)
	}
}

ypChaser.prototype.moveTo = function(ny) {

	if (ypChaser.isN4)	this.chaserDiv.top = ny

	else				this.chaserDiv.style.top = ny
}

ypChaser.prototype.getCurrentY = function() {

	var n = ypChaser.isN4 ? this.chaserDiv.top : parseInt(this.chaserDiv.style.top)

	return isNaN(n) ? 0 : n
}

ypChaser.getWindowScroll = function() {

	if (ypChaser.isIE)	return document.body.scrollTop

	else				return window.pageYOffset
}

ypChaser.getDocumentHeight = function() {

	if (ypChaser.isO5)		return 0 // opera can't retreive this property.

	else if (ypChaser.isIE)	return Math.max(document.body.scrollHeight, document.body.offsetHeight)

	else					return window.document.height

}