function Gallery( p_reference, p_id ){
	this.photoList = document.getElementById( p_id );
	this.currentPhoto = 0;
	this.photoElements = this.photoList.getElementsByTagName('li');
	this.amountPhotos = this.photoElements.length;
	
	this.hidePhoto = function (p_photo ){
		this.photoElements[p_photo].className = 'hidden';
	}

	this.hideAllPhotos = function(){
		for( var i=0; i<this.amountPhotos; i++ ){
			this.hidePhoto(i);
		}
	};
	
	this.showPhoto = function( p_photo ){
		this.photoElements[p_photo].className = '';
	};
	
	this.showNextPhoto = function(){
		this.hidePhoto(this.currentPhoto);
		if( this.currentPhoto == this.amountPhotos-1 ){
			this.currentPhoto = '0';
		}else{
			this.currentPhoto++;
		}
		this.showPhoto(this.currentPhoto);
	};
	
	this.showPreviousPhoto = function(){
		var oldPhoto = this.currentPhoto
		if( this.currentPhoto == 0 ){
			this.currentPhoto = this.amountPhotos - 1;
		}else{
			this.currentPhoto--;
		}
		this.showPhoto(this.currentPhoto);
		this.hidePhoto(oldPhoto);
	};
}