/**
 * Endless Scroll plugin for jQuery
 *
 * v1.3
 *
 * Copyright (c) 2008 Fred Wu
 *
 * Dual licensed under the MIT and GPL licenses:
 *   http://www.opensource.org/licenses/mit-license.php
 *   http://www.gnu.org/licenses/gpl.html
 */

/**
 * Usage:
 *
 * // using default options
 * $(document).endlessScroll();
 *
 * // using some custom options
 * $(document).endlessScroll({
 *   fireOnce: false,
 *   fireDelay: false,
 *   loader: "<div class=\"loading\"><div>",
 *   callback: function(){
 *     alert("test");
 *   }
 * });
 *
 * Configuration options:
 *
 * bottomPixels  integer          the number of pixels from the bottom of the page that triggers the event
 * fireOnce      boolean          only fire once until the execution of the current event is completed
 * fireDelay     integer          delay the subsequent firing, in milliseconds. 0 or false to disable delay.
 * loader        string           the HTML to be displayed during loading
 * data          string|function  plain HTML data, can be either a string or a function that returns a string
 * insertAfter   string           jQuery selector syntax: where to put the loader as well as the plain HTML data
 * callback      function         callback function, accepets one argument: fire sequence (the number of times
 *                                the event triggered during the current page session)
 * resetCounter  function         resets the fire sequence counter if the function returns true, this function
 *                                could also perform hook actions since it is applied at the start of the event
 * ceaseFire     function         stops the event (no more endless scrolling) if the function returns true
 *
 * Usage tips:
 *
 * The plugin is more useful when used with the callback function, which can then make AJAX calls to retrieve content.
 * The fire sequence argument (for the callback function) is useful for 'pagination'-like features.
 */

(function($){

    $.fn.endlessScroll = function(options){

        var defaults = {
            bottomPixels: 50,
            fireOnce: true,
            fireDelay: 150,
            loader: "<br />Loading...<br />",
            data: "",
            insertAfter: "div:last",
            resetCounter: function(){ return false; },
            callback: function(){ return true; },
            ceaseFire: function(){ return false; }
        };

        var options = $.extend(defaults, options);

        var firing       = true;
        var fired        = false;
        var fireSequence = 0;

        if(options.ceaseFire.apply(this) === true)
        {
            firing = false;
        }

        if (firing === true)
        {
            $(window).scroll(function(){
                if ($(document).height() - $(window).height() <= $(window).scrollTop() + options.bottomPixels)
                {
                    if ((options.fireOnce == false || (options.fireOnce == true && fired != true)))
                    {
                        if(options.resetCounter.apply(this) === true)
                        {
                            fireSequence = 0;
                        }

                        fired = true;
                        fireSequence++;

                        $(options.insertAfter).after("<div id=\"endless_scroll_loader\">" + options.loader + "</div>");

                        if (typeof options.data == 'function')
                        {
                            data = options.data.apply(this);
                        }
                        else
                        {
                            data = options.data;
                        }

                        if (data !== false)
                        {
                            $("div#endless_scroll_loader").remove();
                            $(options.insertAfter).after("<div id=\"endless_scroll_data\">" + data + "</div>");
                            $("div#endless_scroll_data").hide().fadeIn();
                            $("div#endless_scroll_data").removeAttr("id");

                            var args = new Array();
                            args[0] = fireSequence;
                            options.callback.apply(this, args);

                            if (options.fireDelay !== false || options.fireDelay !== 0)
                            {
                                // slight delay for preventing event firing twice
                                $("body").after("<div id=\"endless_scroll_marker\"></div>");
                                $("div#endless_scroll_marker").fadeTo(options.fireDelay, 1, function(){
                                    $(this).remove();
                                    fired = false;
                                });
                            }
                            else
                            {
                                fired = false;
                            }
                        }
                    }
                }
            });
        }
    };

})(jQuery);