/* Constructor
 * PARAMS:	thumb_list - array of thumbIDs
 *			first_thumb - the index of the first_thumb to be shown
 */
function ThumbSlider(thumb_list, active_pid, num_thumbs)
{
	this.num_thumbs = num_thumbs; // the number of thumbs that are displayed
	this.thumbList = thumb_list; // the list of thumb IDs
	
	window_padding = Math.floor(this.num_thumbs/2); // find the number of padding images in the viewing window
	currIndex = 0;
	this.first_index = 0; // the first thumb index 
	found = false; // flag to see if a match has occured
	//alert('before loop window_padding = '+window_padding);
	for(i = 0; i< window_padding; i++)
	{
		
		//alert('array value = '+this.thumbList[currIndex]+'\nactive_pid = '+active_pid);
		// check if the pid is in the first few, so there is no need to move the first_index
		if(this.thumbList[currIndex] == active_pid)
		{
			found = true; // change the flag
			//alert('found');
		}
		else
			currIndex++; // not found so move to the next
	}
	
	while(!found && currIndex < this.thumbList.length -window_padding-1)
	{
		if(this.thumbList[currIndex] == active_pid)
		{
			found = true; // change the flag
			//alert('found');
		}
		else
		{	currIndex++; // not found so move to the next
			this.first_index++;
		}
	}
	
	currIndex = this.first_index;
	for(i = 0; i< this.num_thumbs; i++)
	{
//		alert('thumb_'+this.thumbList[currIndex]);
		currThumb = document.getElementById('thumb_'+this.thumbList[currIndex]);
		currThumb.style.display = "inline";
		currIndex++;
	}
}

/* Function to hide the leftmost thumb and show the next one
 */
ThumbSlider.prototype.moveRight = function()
{
	// check to see if it can still move previous ie thumb left at the end
	right_thumb = this.first_index + this.num_thumbs;
	if(right_thumb < this.thumbList.length)
	{
		// get the first of the thumbs that is displayed
		leftThumb = document.getElementById('thumb_'+this.thumbList[this.first_index]);
		leftThumb.style.display = "none";
		
		nextThumb = document.getElementById('thumb_'+this.thumbList[right_thumb]);
		nextThumb.style.display = "inline";
	
		this.first_index++; // move the first index up one
	}
}

/* Function to hide the rightmost thumb and show the previous one
 */
ThumbSlider.prototype.moveLeft = function()
{
	// check to see if it can still move previous ie thumb left at the end
	left_thumb = this.first_index -1;
	//alert('next_thumb = '+next_thumb+'\nthumbList length = '+this.thumbList.length);
	right_thumb = this.first_index + this.num_thumbs;
	if(this.first_index > 0)
	{
		// get the first of the thumbs that is displayed
		leftThumb = document.getElementById('thumb_'+this.thumbList[this.first_index - 1]);
		leftThumb.style.display = "inline";
		
		rightThumb = document.getElementById('thumb_'+this.thumbList[right_thumb - 1]);
		rightThumb.style.display = "none";
	
		this.first_index--; // move the first index down one
	}
}

ThumbSlider.prototype.changePhoto = function()
{
	
}

ThumbSlider.prototype.addThumb = function(thumbID)
{
	this.thumbList.push(thumbID);
}