/**
 * 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 2.0rc
 * @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.ceil(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, 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); }
             lnk.data('page_id', page_id);
             return lnk;
         },
         // Generate a range of numeric links 
         appendRange: function (container, current_page, start, end) {
             var i;
             for (i = start; i < end; i++) {
                 this.createLink(i, current_page).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" }));
             }
             // 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);
                 if (this.opts.num_edge_entries < interval.start && this.opts.ellipse_text) {
                     jQuery("<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) {
                     jQuery("<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);

             }
             // 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" }));
             }
             $('a', fragment).click(eventHandler);
             return fragment;
         }
     });

     // Extend jQuery
     $.fn.pagination = function (maxentries, opts) {

         // Initialize options with default values
         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,
             renderer: "defaultRenderer",
             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 pageSelected(evt) {
             var links, current_page = $(evt.target).data('page_id');
             if (current_page == undefined) current_page = $(evt.target).parent().data('page_id');
             containers.data('current_page', current_page);
             links = renderer.getLinks(current_page, pageSelected);
             containers.empty();
             links.appendTo(containers);
             var continuePropagation = opts.callback(current_page, containers);
             if (!continuePropagation) {
                 if (evt.stopPropagation) {
                     evt.stopPropagation();
                 }
                 else {
                     evt.cancelBubble = true;
                 }
             }
             return continuePropagation;
         }

         current_page = opts.current_page;
         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);

         containers.each(function () {
             // Attach control functions to the DOM element 
             this.selectPage = function (page_id) { pageSelected(page_id); }
             this.prevPage = function () {
                 var current_page = containers.data('current_page');
                 if (current_page > 0) {
                     pageSelected(current_page - 1);
                     return true;
                 }
                 else {
                     return false;
                 }
             }
             this.nextPage = function () {
                 var current_page = containers.data('current_page');
                 if (current_page < numPages() - 1) {
                     pageSelected(current_page + 1);
                     return true;
                 }
                 else {
                     return false;
                 }
             }
         });
         // When all initialisation is done, draw the links
         links = renderer.getLinks(current_page, pageSelected);
         containers.empty();
         links.appendTo(containers);
         // call callback function
         opts.callback(current_page, containers);

     }

 })(jQuery);