/**
 * this jquery plugin displays pagination links inside the selected elements.
 * 
 * this plugin needs at least jquery 1.4.2
 *
 * @author gabriel birke (birke *at* d-scribe *dot* de)
 * @version 2.2
 * @param {int} maxentries number of entries to paginate
 * @param {object} opts several options (see readme for documentation)
 * @return {object} jquery object
 */
 (function($){
	/**
	 * @class class for calculating pagination values
	 */
	$.paginationcalculator = function(maxentries, opts) {
		this.maxentries = maxentries;
		this.opts = opts;
	};
	
	$.extend($.paginationcalculator.prototype, {
		/**
		 * calculate the maximum number of pages
		 * @method
		 * @returns {number}
		 */
		numpages:function() {
			return math.ceil(this.maxentries/this.opts.items_per_page);
		},
		/**
		 * calculate start and end point of pagination links depending on 
		 * current_page and num_display_entries.
		 * @returns {array}
		 */
		getinterval:function(current_page)  {
			var ne_half = math.floor(this.opts.num_display_entries/2);
			var np = this.numpages();
			var upper_limit = np - this.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 + (this.opts.num_display_entries % 2), np):math.min(this.opts.num_display_entries, np);
			return {start:start, end:end};
		}
	});
	
	// initialize jquery object container for pagination renderers
	$.paginationrenderers = {};
	
	/**
	 * @class default renderer for rendering pagination links
	 */
	$.paginationrenderers.defaultrenderer = function(maxentries, opts) {
		this.maxentries = maxentries;
		this.opts = opts;
		this.pc = new $.paginationcalculator(maxentries, opts);
	};
	$.extend($.paginationrenderers.defaultrenderer.prototype, {
		/**
		 * helper function for generating a single link (or a span tag if it's the current page)
		 * @param {number} page_id the page id for the new item
		 * @param {number} current_page 
		 * @param {object} appendopts options for the new item: text and classes
		 * @returns {jquery} jquery object containing the link
		 */
		createlink:function(page_id, current_page, appendopts){
			var lnk, np = this.pc.numpages();
			page_id = page_id<0?0:(page_id<np?page_id:np-1); // normalize page id to sane value
			appendopts = $.extend({text:page_id+1, classes:""}, appendopts||{});
			if(page_id == current_page){
				lnk = $("<span class='current'>" + appendopts.text + "</span>");
			}
			else
			{
				lnk = $("<a>" + appendopts.text + "</a>")
					.attr('href', this.opts.link_to.replace(/__id__/,page_id));
			}
			if(appendopts.classes){ lnk.addclass(appendopts.classes); }
			if(appendopts.rel){ lnk.attr('rel', appendopts.rel); }
			lnk.data('page_id', page_id);
			return lnk;
		},
		// generate a range of numeric links 
		appendrange:function(container, current_page, start, end, opts) {
			var i;
			for(i=start; i<end; i++) {
				this.createlink(i, current_page, opts).appendto(container);
			}
		},
		getlinks:function(current_page, eventhandler) {
			var begin, end,
				interval = this.pc.getinterval(current_page),
				np = this.pc.numpages(),
				fragment = $("<div class='pagination'></div>");
			
			// generate "previous"-link
			if(this.opts.prev_text && (current_page > 0 || this.opts.prev_show_always)){
				fragment.append(this.createlink(current_page-1, current_page, {text:this.opts.prev_text, classes:"prev",rel:"prev"}));
			}
			// generate starting points
			if (interval.start > 0 && this.opts.num_edge_entries > 0)
			{
				end = math.min(this.opts.num_edge_entries, interval.start);
				this.appendrange(fragment, current_page, 0, end, {classes:'sp'});
				if(this.opts.num_edge_entries < interval.start && this.opts.ellipse_text)
				{
					$("<span>"+this.opts.ellipse_text+"</span>").appendto(fragment);
				}
			}
			// generate interval links
			this.appendrange(fragment, current_page, interval.start, interval.end);
			// generate ending points
			if (interval.end < np && this.opts.num_edge_entries > 0)
			{
				if(np-this.opts.num_edge_entries > interval.end && this.opts.ellipse_text)
				{
					$("<span>"+this.opts.ellipse_text+"</span>").appendto(fragment);
				}
				begin = math.max(np-this.opts.num_edge_entries, interval.end);
				this.appendrange(fragment, current_page, begin, np, {classes:'ep'});
				
			}
			// generate "next"-link
			if(this.opts.next_text && (current_page < np-1 || this.opts.next_show_always)){
				fragment.append(this.createlink(current_page+1, current_page, {text:this.opts.next_text, classes:"next",rel:"next"}));
			}
			$('a', fragment).click(eventhandler);
			return fragment;
		}
	});
	
	// extend jquery
	$.fn.pagination = function(maxentries, opts){
		
		// initialize options with default values
		opts = $.extend({
			items_per_page:10,
			num_display_entries:11,
			current_page:0,
			num_edge_entries:0,
			link_to:"javascript:void",
			prev_text:"prev",
			next_text:"next",
			ellipse_text:"...",
			prev_show_always:true,
			next_show_always:true,
			renderer:"defaultrenderer",
			show_if_single_page:false,
			load_first_page:true,
			callback:function(){return false;}
		},opts||{});
		
		var containers = this,
			renderer, links, current_page;
		
		/**
		 * this is the event handling function for the pagination links. 
		 * @param {int} page_id the new page number
		 */
		function paginationclickhandler(evt){
			var links, 
				new_current_page = $(evt.target).data('page_id'),
				continuepropagation = selectpage(new_current_page);
			if (!continuepropagation) {
				evt.stoppropagation();
			}
			return continuepropagation;
		}
		
		/**
		 * this is a utility function for the internal event handlers. 
		 * it sets the new current page on the pagination container objects, 
		 * generates a new html fragment for the pagination links and calls
		 * the callback function.
		 */
		function selectpage(new_current_page) {
			// update the link display of a all containers
			containers.data('current_page', new_current_page);
			links = renderer.getlinks(new_current_page, paginationclickhandler);
			containers.empty();
			links.appendto(containers);
			// call the callback and propagate the event if it does not return false
			var continuepropagation = opts.callback(new_current_page, containers);
			return continuepropagation;
		}
		
		// -----------------------------------
		// initialize containers
		// -----------------------------------
		current_page = parseint(opts.current_page, 10);
		containers.data('current_page', 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;
		
		if(!$.paginationrenderers[opts.renderer])
		{
			throw new referenceerror("pagination renderer '" + opts.renderer + "' was not found in jquery.paginationrenderers object.");
		}
		renderer = new $.paginationrenderers[opts.renderer](maxentries, opts);
		
		// attach control events to the dom elements
		var pc = new $.paginationcalculator(maxentries, opts);
		var np = pc.numpages();
		containers.off('setpage').on('setpage', {numpages:np}, function(evt, page_id) { 
				if(page_id >= 0 && page_id < evt.data.numpages) {
					selectpage(page_id); return false;
				}
		});
		containers.off('prevpage').on('prevpage', function(evt){
				var current_page = $(this).data('current_page');
				if (current_page > 0) {
					selectpage(current_page - 1);
				}
				return false;
		});
		containers.off('nextpage').on('nextpage', {numpages:np}, function(evt){
				var current_page = $(this).data('current_page');
				if(current_page < evt.data.numpages - 1) {
					selectpage(current_page + 1);
				}
				return false;
		});
		containers.off('currentpage').on('currentpage', function(){
				var current_page = $(this).data('current_page');
				selectpage(current_page);
				return false;
		});
		
		// when all initialisation is done, draw the links
		links = renderer.getlinks(current_page, paginationclickhandler);
		containers.empty();
		if(np > 1 || opts.show_if_single_page) {
			links.appendto(containers);
		}
		// call callback function
		if(opts.load_first_page) {
			//opts.callback(current_page, containers);
		}
	}; // end of $.fn.pagination block
	
})(jquery);