/**

 * 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);

    });

};

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