/**
 * 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 2.1
 * @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:10,
      num_display_entries:11,
      current_page:0,
      num_edge_entries:0,
      link_to:"#",
      prev_text:"&lt;&lt;",
      next_text:"&gt;&gt;",
      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 paginationClickHandler(evt){
      var links, 
        new_current_page = $(evt.target).data('page_id'),
        continuePropagation = selectPage(new_current_page);
        document.location = '#p' + 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
    opts.callback(current_page, containers);
  } // End of $.fn.pagination block
  
})(jQuery);