(function($){
    
  $.fn.infinitescroll = function(options,callback){
    
    // console log wrapper.
    function debug(){
      if (opts.debug) { window.console && console.log.call(console,arguments)}
    }
    
    // grab each selector option and see if any fail.
    function areSelectorsValid(opts){
      for (var key in opts){
        if (key.indexOf && key.indexOf('Selector') > -1 && $(opts[key]).length === 0){
            debug('Your ' + key + ' found no elements.');    
            return false;
        } 
        return true;
      }
    }


    // find the number to increment in the path.
    function determinePath(path){
           path.match(relurl) ? path.match(relurl)[2] : path; 
      // there is a 2 in the url surrounded by slashes, e.g. /page/2/
      if ( path.match(/^(.*?)\b2\b(.*?$)/) ){ 
          path = path.match(/^(.*?)\b2\b(.*?$)/).slice(1);
      } else 
        // if there is any 2 in the url at all.
        if (path.match(/^(.*?)2(.*?$)/)){
          
          // page= is used in django:
          //   http://www.infinite-scroll.com/changelog/comment-page-1/#comment-127
          if ( path.match(/^(.*?page=)2(\/.*|$)/) ){
            path = path.match(/^(.*?page=)2(\/.*|$)/).slice(1);
            return path;
          }
          
          debug('Trying backup next selector parse technique. Treacherous waters here, matey.');
          path = path.match(/^(.*?)2(.*?$)/).slice(1);
      } else {
        // page= is used in drupal too but second page is page=1 not page=2:
        // thx Jerod Fritz, vladikoff
        if (path.match(/^(.*?page=)1(\/.*|$)/)) {
	   	
		path = path.match(/^(.*?page=)1(\/.*|$)/).slice(1);
		return path;
        }  

        debug('Sorry, we couldn\'t parse your Next (Previous Posts) URL. Verify your the css selector points to the correct A tag. If you still get this error: yell, scream, and kindly ask for help at infinite-scroll.com.');    
        props.isInvalidPage = true;  //prevent it from running on this page.
      }
      
      return path;
    }


    // 'document' means the full document usually, but sometimes the content of the overflow'd div in local mode
    function getDocumentHeight(){
      // weird doubletouch of scrollheight because http://soulpass.com/2006/07/24/ie-and-scrollheight/
      return opts.localMode ? ($(props.container)[0].scrollHeight && $(props.container)[0].scrollHeight) 
                                // needs to be document's height. (not props.container's) html's height is wrong in IE.
                                : $(document).height()
    }
    
    
        
    function isNearBottom(){
      
      // distance remaining in the scroll
      // computed as: document height - distance already scroll - viewport height - buffer
      var pixelsFromWindowBottomToBottom = 0 +
                getDocumentHeight()  - (
                    opts.localMode ? $(props.container).scrollTop() : 
                    // have to do this bs because safari doesnt report a scrollTop on the html element
                    ($(props.container).scrollTop() || $(props.container.ownerDocument.body).scrollTop())
                    ) - $(opts.localMode ? props.container : window).height();
      
      debug('math:',pixelsFromWindowBottomToBottom, props.pixelsFromNavToBottom);
      
      // if distance remaining in the scroll (including buffer) is less than the orignal nav to bottom....
      return (pixelsFromWindowBottomToBottom  - opts.bufferPx < props.pixelsFromNavToBottom);    
    }    
    
    function showDoneMsg(){
      /*
      props.loadingMsg
        .find('img').hide()
        .parent()
          .find('div').html(opts.donetext).animate({opacity: 1},2000, function() {
            $(this).parent().fadeOut('normal');
          });
      */
      // user provided callback when done    
      opts.errorCallback(opts.second);
    }
    
    function infscrSetup(){
    
        if (props.isDuringAjax || props.isInvalidPage || props.isDone) return; 
        
        if ( !isNearBottom(opts,props) ) return; 
        
        $(document).trigger('retrieve.infscr');
                
                
    }  // end of infscrSetup()
          
  
      
    function kickOffAjax(){
        // we dont want to fire the ajax multiple times
        props.isDuringAjax = true; 
        
        // show the loading message quickly
        // then hide the previous/next links after we're
        // sure the loading message was visible
        props.loadingMsg.appendTo( opts.loadMsgSelector ).show(opts.loadingMsgRevealSpeed, function(){
          $( opts.navSelector ).hide(); 
	   // increment the URL bit. e.g. /page/3/
          var pg = (opts.second == false) ? ++props.currPage : ++props.extraPage;  
	     
	   debug('heading into ajax',path);

          // if we're dealing with a table we can't use DIVs
          box = $(opts.contentSelector).is('table') ? $('<tbody/>') : $('<div/>');  
          frag = document.createDocumentFragment();
    	   	
          box.load( path.join(pg) + ' ' + opts.itemSelector,null,loadCallback);
        });
        
       
    }
    
    function loadCallback(){
        // if we've hit the last page...
        if (props.isDone){
	     showDoneMsg();
            
            return false;    
        } else {
        	var children = box.children();
		if(children.length == 0)
		{
			showDoneMsg();
              	return;
		}	
        	// if it didn't return anything
            if (children.length == 0 || children.hasClass('error404')){
              // fake an ajaxError so we can quit.
              return $.event.trigger( "ajaxError", [{status:404}] ); 
            }
            
            //check if a target container has been set
            //if so , devide the elemets along all the containers
            if(opts.targetContainer != undefined && jQuery(opts.targetContainer).length > 0)
            {
            	var containers = jQuery(opts.targetContainer);
				var column_items = Math.ceil(children.length / containers.length)-1;
				var remained_items = children.length % containers.length;
            	
				for (var i = 0; i < children.length; i++) {
					var $child = jQuery(children[i]);
					var _colIndex = children[i].className.split(" ")[0];
					jQuery(containers[_colIndex]).append($child);
				}
				/*
            	//display the column items
            	for(var i=0;i<containers.length*column_items;i++)
            	{
            		if(children[i] == undefined)
            			continue;
            		
            		//choose the column to be displayed into 
            		var column = Math.ceil(i / column_items) - 1;
            		column = (column < 0) ? 0 : column;
            		
            		jQuery(containers[column]).append(jQuery(children[i]));
            	}
            	
            	//display the remaining itmes
            	for(var i=0;i<remained_items;i++)
            	{
            		jQuery(containers[i]).append(jQuery(children[i]));
            	}*/
            }
            else
            {
				// use a documentFragment because it works when content is going into a table or UL
	            while (box[0].firstChild){
	              frag.appendChild(  box[0].firstChild );
	            }
	
	           	$(opts.contentSelector)[0].appendChild(frag);
            }
            // fadeout currently makes the <em>'d text ugly in IE6
            props.loadingMsg.fadeOut('normal' ); 

            // smooth scroll to ease in the new content
            if (opts.animate){ 
                var scrollTo = $(window).scrollTop()  + opts.extraScrollPx + 'px';
                $('html,body').animate({scrollTop: scrollTo}, 800,function(){ props.isDuringAjax = false; }); 
            }
        
            // previously, we would pass in the new DOM element as context for the callback
            // however we're now using a documentfragment, which doesnt havent parents or children,
            // so the context is the contentContainer guy, and we pass in an array
            //   of the elements collected as the first argument.
            callback.call( $(opts.contentSelector)[0], children.get() );
        
            if (!opts.animate) props.isDuringAjax = false; // once the call is done, we can allow it again.
        }
    }
    
      
    // lets get started.
    $.browser.ie6 = $.browser.msie && $.browser.version < 7;
    
    var opts    = $.extend({}, $.infinitescroll.defaults, options),
        props   = $.infinitescroll, // shorthand
        box, frag;
        
    callback    = callback || function(){};
    
    if (!areSelectorsValid(opts)){ return false;  }
    
    // we doing this on an overflow:auto div?
    props.container   =  opts.localMode ? this : document.documentElement;
                   
    // contentSelector we'll use for our .load()
    opts.contentSelector = opts.contentSelector || this;
    
    // loadMsgSelector - if we want to place the load message in a specific selector, defaulted to the contentSelector
    opts.loadMsgSelector = opts.loadMsgSelector || opts.contentSelector;
    
    
    // get the relative URL - everything past the domain name.
    var relurl        = /(.*?\/\/).*?(\/.*)/,
        path          = $(opts.nextSelector).attr('href');
    
    
    if (!path) { debug('Navigation selector not found'); return; }
    
    // set the path to be a relative URL from root.
    path          = determinePath(path);
    
    // reset scrollTop in case of page refresh:
    if (opts.localMode) $(props.container)[0].scrollTop = 0;

    // distance from nav links to bottom
    // computed as: height of the document + top offset of container - top offset of nav link
    props.pixelsFromNavToBottom =  getDocumentHeight()  +
                                     (props.container == document.documentElement ? 0 : $(props.container).offset().top )- 
                                     $(opts.navSelector).offset().top;
    
    // define loading msg
    props.loadingMsg = $('<div></div>');    
     // preload the image
    (new Image()).src    = opts.loadingImg;
              

  
    // set up our bindings
    $(document).ajaxError(function(e,xhr,opt){
      debug('Page not found. Self-destructing...');    
      
      // die if we're out of pages.
      if (xhr.status == 404){ 
        showDoneMsg();
        props.isDone = true; 
        $(opts.localMode ? this : window).unbind('scroll.infscr');
      } 
    });
    
    // bind scroll handler to element (if its a local scroll) or window  
    $(opts.localMode ? this : window)
      .bind('scroll.infscr', infscrSetup)
      .trigger('scroll.infscr'); // trigger the event, in case it's a short page
    
    if(opts.activator != undefined)
    {
    	jQuery(opts.activator).click(kickOffAjax);
    }
    else
    {
    	$(document).bind('retrieve.infscr',kickOffAjax);
        
    }
    return this;
  
  }  // end of $.fn.infinitescroll()
  

  
  // options and read-only properties object
  
  $.infinitescroll = {     
        defaults      : {
                          debug           : false,
                          preload         : false,
                          nextSelector    : "div.navigation a:first",
                          loadingImg      : "",
                          loadingText     : "",
                          donetext        : "",
                          navSelector     : "div.navigation",
                          contentSelector : null,           // not really a selector. :) it's whatever the method was called on..
                          loadMsgSelector : null,
                          loadingMsgRevealSpeed : 'fast', // controls how fast you want the loading message to come in, ex: 'fast', 'slow', 200 (milliseconds)
                          extraScrollPx   : 150,
                          itemSelector    : "div.post",
                          animate         : false,
			     second : false,
                          localMode       : false,
                          bufferPx        : 40,
                          targetContainer : undefined, 
                          errorCallback   : function(){}
                        }, 
        loadingImg    : undefined,
        loadingMsg    : undefined,
        container     : undefined,
        activator	  : undefined,
        currPage      : 0,
	 extraPage     : 0,
	 second 	 : false,
        currDOMChunk  : null,  // defined in setup()'s load()
        isDuringAjax  : false,
        isInvalidPage : false,
        targetContainer: undefined,
        isDone        : false  // for when it goes all the way through the archive.
  };
  


})(jQuery);