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

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

                // Initialize options with default values
                opts = jQuery.extend({
                        items_per_page:5,
                        num_display_entries:3,
                        current_page:0,
                        num_edge_entries:1,
                        link_to:"#",
                        prev_text:"Prev",
                        next_text:"Next",
                        ellipse_text:"...",
                        prev_show_always:true,
                        next_show_always:true,
                        renderer:"defaultRenderer",
                        load_first_page:false,
                        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 = 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);

                // Attach control events to the DOM elements
                var pc = new $.PaginationCalculator(maxentries, opts);
                var np = pc.numPages();
                containers.bind('setPage', {numPages:np}, function(evt, page_id) {
                                if(page_id >= 0 && page_id < evt.data.numPages) {
                                        selectPage(page_id); return false;
                                }
                });
                containers.bind('prevPage', function(evt){
                                var current_page = $(this).data('current_page');
                                if (current_page > 0) {
                                        selectPage(current_page - 1);
                                }
                                return false;
                });
                containers.bind('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;
                });

                // When all initialisation is done, draw the links
                links = renderer.getLinks(current_page, paginationClickHandler);
                containers.empty();
                links.appendTo(containers);
                // call callback function
                if(opts.load_first_page) {
                        opts.callback(current_page, containers);
                }
        } // End of $.fn.pagination block

})(jQuery);