// =======================================================================
// PageLess - endless page
//
// Author: Jean-Sébastien Ney (jeansebastien.ney@gmail.com)
// Contributors:
//	Alexander Lang (langalex)
// 	Lukas Rieder (Overbryd)
//  Ryan Michael (kerinin)
//
// Parameters:
//    currentPage: current page (params[:page])
//    distance: distance to the end of page in px when ajax query is fired
//    loader: selector of the loader div (ajax activity indicator)
//    loaderHtml: html code of the div if loader not used
//    loaderImage: image inside the loader
//    loaderMsg: displayed ajax message
//    pagination: selector of the paginator divs. (if javascript is disabled paginator is required)
//    params: paramaters for the ajax query, you can pass auth_token here
//    totalPages: total number of pages
//    url: URL used to request more data
//    progress: selector of elements tracked by the progress cookie (ie 'div.progress')
//    progress_id: element ID to scroll to (assumed to be taken from previous progress cookie)
//    progress_top: pixel dimension from top of window to trigger progress or scroll to (if progress_id defined)
// Callback Parameters:
//		scrape: A function to modify the incoming data. (Doesn't do anything by default)
//		complete: A function to call when a new page has been loaded (optional)
//		afterStopListener: A function to call when the last page has been loaded (optional)
//
// Requires: jquery + jquery dimensions
//
// Thanks to:
//  * codemonky.com/post/34940898
//  * www.unspace.ca/discover/pageless/
//  * famspam.com/facebox
// =======================================================================

(function($) {
  $.pageless = function(settings) {
    $.isFunction(settings) ? settings.call() : $.pageless.init(settings);
  };

  // available params
  // loader: loading div
  // pagination: div selector for the pagination links
  // loaderMsg:
  // loaderImage:
  // loaderHtml:
  $.pageless.settings = {
    currentPage:  1,
    pagination:   '.pagination',
    url:          location.href,
    params:       {}, // params of the query you can pass auth_token here
    distance:     400, // page distance in px to the end when the ajax function is launch
    loaderImage:  "/images/load.gif",
		scrape: function(data) { return data; }  // Don't do anything by default
  };

  $.pageless.loaderHtml = function(){
    return $.pageless.settings.loaderHtml || '\
<div id="pageless-loader" style="display:none;text-align:center;width:100%;">\
  <div class="msg" style="color:#e9e9e9;font-size:2em"></div>\
  <img src="' + $.pageless.settings.loaderImage + '" title="load" alt="loading more results" style="margin: 10px auto" />\
</div>';
  };

  // settings params: totalPages
  $.pageless.init = function(settings) {
    if ($.pageless.settings.inited) return;
    $.pageless.settings.inited = true;

    if (settings) $.extend($.pageless.settings, settings);

    // for accessibility we can keep pagination links
    // but since we have javascript enabled we remove pagination links
    if($.pageless.settings.pagination)
      $($.pageless.settings.pagination).remove();

    // start the listener
    $.pageless.startListener();

    if( $.pageless.settings.progress_id ){
        // advance to the previous progress id set the progress element
        element = $( "#"+$.escape($.pageless.settings.progress_id) );
        offset = $.pageless.settings.progress_top ? (element.offset()['top']-(+$.pageless.settings.progress_top)) : element.offset()['top'];
        $(window).scrollTop( offset );
        $.pageless.setProgress( element );
    } else if ($.pageless.settings.progress){
        // set progress to the first element matching the 'progress' selector
        $.pageless.setProgress( $( $.pageless.settings.progress ).eq(0) );
    }
  };

  // init loader val
  $.pageless.isLoading = false;

  $.fn.pageless = function(settings) {
    $.pageless.init(settings);
    $.pageless.el = $(this);

    // loader element
    if(settings.loader && $(settings.loader).length){
      $.pageless.loader = $(settings.loader);
    } else {
      $.pageless.loader = $($.pageless.loaderHtml());
      $(this).append($.pageless.loader);
      // if we use the default loader, set the message
      if(!settings.loaderHtml) { $('#pageless-loader .msg').html(settings.loaderMsg) }
    }
  };

  //
  $.pageless.loading = function(bool){
    if(bool === true){
      $.pageless.isLoading = true;
      if($.pageless.loader)
        $.pageless.loader.fadeIn('normal');
    } else {
      $.pageless.isLoading = false;
      if($.pageless.loader)
        $.pageless.loader.fadeOut('normal');
    }
  };

  $.pageless.stopListener = function() {
    $(window).unbind('.pageless');
  };

  $.pageless.startListener = function() {
    $(window).bind('scroll.pageless', $.pageless.scroll);
  };


  // set the progress to current.id
  $.pageless.setProgress = function(current) {
    if(current && current.attr('id') ) {
      // set the cookie and a variable to access the current progress element
      $.pageless.progress_current = current;
      document.cookie = "pageless_progress="+current.attr('id')+"; path="+location.pathname;
    }
  };

  $.pageless.scroll = function() {
    // listener was stopped or we've run out of pages
    if($.pageless.settings.totalPages <= $.pageless.settings.currentPage){
      // $.pageless.stopListener();
			// if there is a afterStopListener callback we call it
      if ($.pageless.settings.afterStopListener) { $.pageless.settings.afterStopListener.call(); }
      return;
    } else if( $.pageless.progress_current && ($.pageless.progress_current.offset()['top']-(+$.pageless.settings.progress_top)) < $(window).scrollTop() ) {
      // find the next element matching the 'progress' selector
      next_current = $.pageless.progress_current.nextAll( $.pageless.settings.progress+'[id]:first' );
      // set the progress to cookie to the next element
      $.pageless.setProgress( next_current );
      // and trigger the scroll event on the new one
      // (in case we need to move forward more than one element)
      // (ie user presses 'end' key)
      $(window).trigger('scroll');
    }

    // distance to end of page
    var distance = $(document).height()-$(window).scrollTop()-$(window).height();
    // if slider past our scroll offset, then fire a request for more data
    if(!$.pageless.isLoading && (distance < $.pageless.settings.distance)) {
      $.pageless.loading(true);
      // move to next page
      $.pageless.settings.currentPage++;
      // set up ajax query params
      $.extend($.pageless.settings.params, {page: $.pageless.settings.currentPage});
      // finally ajax query
      $.get($.pageless.settings.url, $.pageless.settings.params, function(data){
				var data = $.pageless.settings.scrape(data);
				if ($.pageless.loader) { $.pageless.loader.before(data) } else { $.pageless.el.append(data) }
        $.pageless.loading(false);
        // if there is a complete callback we call it
        if ($.pageless.settings.complete) { $.pageless.settings.complete.call(); }
      });
    }
  };
})(jQuery);