/**
 * 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({
    num_display_entries:12,    
    current_page:0,
    num_edge_entries:2,
    link_to:"#",
    prev_text:"«",
    next_text:"»",
    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:"sites"}, appendopts||{});
        if(page_id == current_page){
          var lnk = jQuery("<a class='sites'>"+(appendopts.text)+"</a>");
        }
        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:"sites"});
      }
      // 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:"sites"});
      }
    }
    
    // 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);
  });
}