/**
 * This jQuery plugin displays pagination links inside the selected elements.
 *
 * @author Gabriel Birke (birke *at* d-scribe *dot* de)
 * @version 1.2
 * @param {int} maxentries Number of entries to paginate
 * @param {Object} opts Several options (see README for documentation)
 * @return {Object} jQuery Object
 */
jQuery.fn.pagination = function(maxentries, opts){
    opts = jQuery.extend({
items_per_page:10,
num_display_entries:10,
current_page:0,
num_edge_entries:0,
link_to:"#",
prev_text:"Prev",
next_text:"Next",
ellipse_text:"...",
prev_show_always:true,
next_show_always:true,
callback:function(){return false;}
},opts||{});

return this.each(function() {
	/**
	 * Calculate the maximum number of pages
	 */
	function numPages() {
	return Math.ceil(maxentries/opts.items_per_page);
	}

	/**
	 * Calculate start and end point of pagination links depending on 
	 * current_page and num_display_entries.
	 * @return {Array}
	 */
	function getInterval()  {
	var ne_half = Math.ceil(opts.num_display_entries/2);
	var np = numPages();
	var upper_limit = np-opts.num_display_entries;
	var start = current_page>ne_half?Math.max(Math.min(current_page-ne_half, upper_limit), 0):0;
	var end = current_page>ne_half?Math.min(current_page+ne_half, np):Math.min(opts.num_display_entries, np);
	return [start,end];
	}

	/**
	 * This is the event handling function for the pagination links. 
	 * @param {int} page_id The new page number
	 */
	function pageSelected(page_id, evt){
	    current_page = page_id;
	    drawLinks();
	    var continuePropagation = opts.callback(page_id, panel);
	    if (!continuePropagation) {
		if (evt.stopPropagation) {
		    evt.stopPropagation();
		}
		else {
		    evt.cancelBubble = true;
		}
	    }
	    return continuePropagation;
	}

	/**
	 * This function inserts the pagination links into the container element
	 */
	function drawLinks() {
	    panel.empty();
	    var interval = getInterval();
	    var np = numPages();
	    // This helper function returns a handler function that calls pageSelected with the right page_id
	    var getClickHandler = function(page_id) {
		return function(evt){ return pageSelected(page_id,evt); }
	    }
	    // Helper function for generating a single link (or a span tag if it's the current page)
	    var appendItem = function(page_id, appendopts){
		page_id = page_id<0?0:(page_id<np?page_id:np-1); // Normalize page id to sane value
		appendopts = jQuery.extend({text:page_id+1, classes:""}, appendopts||{});
		if(page_id == current_page){
		    var lnk = jQuery("<span class='current'>"+(appendopts.text)+"</span>");
		}
		else
		{
		    var lnk = jQuery("<a>"+(appendopts.text)+"</a>")
			.bind("click", getClickHandler(page_id))
			.attr('href', opts.link_to.replace(/__id__/,page_id));


		}
		if(appendopts.classes){lnk.addClass(appendopts.classes);}
		panel.append(lnk);
	    }
	    // Generate "Previous"-Link
	    if(opts.prev_text && (current_page > 0 || opts.prev_show_always)){
		appendItem(current_page-1,{text:opts.prev_text, classes:"prev"});
	    }
	    // Generate starting points
	    if (interval[0] > 0 && opts.num_edge_entries > 0)
	    {
		var end = Math.min(opts.num_edge_entries, interval[0]);
		for(var i=0; i<end; i++) {
		    appendItem(i);
		}
		if(opts.num_edge_entries < interval[0] && opts.ellipse_text)
		{
		    jQuery("<span>"+opts.ellipse_text+"</span>").appendTo(panel);
		}
	    }
	    // Generate interval links
	    for(var i=interval[0]; i<interval[1]; i++) {
		appendItem(i);
	    }
	    // Generate ending points
	    if (interval[1] < np && opts.num_edge_entries > 0)
	    {
		if(np-opts.num_edge_entries > interval[1]&& opts.ellipse_text)
		{
		    jQuery("<span>"+opts.ellipse_text+"</span>").appendTo(panel);
		}
		var begin = Math.max(np-opts.num_edge_entries, interval[1]);
		for(var i=begin; i<np; i++) {
		    appendItem(i);
		}

	    }
	    // Generate "Next"-Link
	    if(opts.next_text && (current_page < np-1 || opts.next_show_always)){
		appendItem(current_page+1,{text:opts.next_text, classes:"next"});
	    }
	}

	// Extract current_page from options
	var current_page = opts.current_page;
	// Create a sane value for maxentries and items_per_page
	maxentries = (!maxentries || maxentries < 0)?1:maxentries;
	opts.items_per_page = (!opts.items_per_page || opts.items_per_page < 0)?1:opts.items_per_page;
	// Store DOM element for easy access from all inner functions
	var panel = jQuery(this);
	// Attach control functions to the DOM element 
	this.selectPage = function(page_id){ pageSelected(page_id);}
	this.prevPage = function(){ 
	    if (current_page > 0) {
		pageSelected(current_page - 1);
		return true;
	    }
	    else {
		return false;
	    }
	}
	this.nextPage = function(){ 
	    if(current_page < numPages()-1) {
		pageSelected(current_page+1);
		return true;
	    }
	    else {
		return false;
	    }
	}
	// When all initialisation is done, draw the links
	drawLinks();
	// call callback function
	opts.callback(current_page, this);
});
}