/*!
 * Infinite Ajax Scroll, a jQuery plugin
 * Version 1.0.2
 * https://github.com/webcreate/infinite-ajax-scroll
 *
 * Copyright (c) 2011-2013 Jeroen Fiege
 * Licensed under MIT:
 * https://raw.github.com/webcreate/infinite-ajax-scroll/master/MIT-LICENSE.txt
 */

(function ($) {

    'use strict';

    Date.now = Date.now || function () { return +new Date(); };

    $.ias = function (options)
    {
        // setup
        var opts             = $.extend({}, $.ias.defaults, options);
        var util             = new $.ias.util();                                // utilities module
        var paging           = new $.ias.paging(opts.scrollContainer);          // paging module
        var hist             = (opts.history ? new $.ias.history() : false);    // history module
        var _self            = this;

        /**
         * Initialize
         *
         * - tracks scrolling through pages
         * - remembers current page with the history module
         * - setup scroll event and hides pagination element
         * - loads and scrolls to previous page when we have something in our history
         *
         * @return self
         */
        function init()
        {
            var pageNum;

            // track page number changes
            paging.onChangePage(function (pageNum, scrollOffset, pageUrl) {
                if (hist) {
                    hist.setPage(pageNum, pageUrl);
                }

                // call onPageChange event
                opts.onPageChange.call(this, pageNum, pageUrl, scrollOffset);
            });

            // setup scroll and hide pagination
            reset();

            // load and scroll to previous page
            if (hist && hist.havePage()) {
                stop_scroll();

                pageNum = hist.getPage();

                util.forceScrollTop(function () {
                    var curThreshold;

                    if (pageNum > 1) {
                        paginateToPage(pageNum);

                        curThreshold = get_scroll_threshold(true);
                        $('html, body').scrollTop(curThreshold);
                    }
                    else {
                        reset();
                    }
                });
            }

            return _self;
        }

        // initialize
        init();

        /**
         * Reset scrolling and hide pagination links
         *
         * @return void
         */
        function reset()
        {
            hide_pagination();

            opts.scrollContainer.scroll(scroll_handler);
        }

        /**
         * Scroll event handler
         *
         * @return void
         */
        function scroll_handler()
        {
            var curScrOffset,
                scrThreshold;

            curScrOffset = util.getCurrentScrollOffset(opts.scrollContainer);
            scrThreshold = get_scroll_threshold();

            if (curScrOffset >= scrThreshold) {
                if (get_current_page() >= opts.triggerPageThreshold) {
                    stop_scroll();
                    show_trigger(function () {
                        paginate(curScrOffset);
                    });
                }
                else {
                    paginate(curScrOffset);
                }
            }
        }

        /**
         * Cancel scrolling
         *
         * @return void
         */
        function stop_scroll()
        {
            opts.scrollContainer.unbind('scroll', scroll_handler);
        }

        /**
         * Hide pagination
         *
         * @return void
         */
        function hide_pagination()
        {
            $(opts.pagination).hide();
        }

        /**
         * Get scroll threshold based on the last item element
         *
         * @param boolean pure indicates if the thresholdMargin should be applied
         * @return integer threshold
         */
        function get_scroll_threshold(pure)
        {
            var el,
                threshold;

            el = $(opts.container).find(opts.item).last();

            if (el.size() === 0) {
                return 0;
            }

            threshold = el.offset().top + el.height();

            if (!pure) {
                threshold += opts.thresholdMargin;
            }

            return threshold;
        }

        /**
         * Load the items from the next page.
         *
         * @param int      curScrOffset      current scroll offset
         * @param function onCompleteHandler callback function
         * @return void
         */
        function paginate(curScrOffset, onCompleteHandler)
        {
            var urlNextPage;

            urlNextPage = $(opts.next).attr('href');
            if (!urlNextPage) {
                if (opts.noneleft) {
                    $(opts.container).find(opts.item).last().after(opts.noneleft);
                }
                return stop_scroll();
            }

            if (opts.beforePageChange && $.isFunction(opts.beforePageChange)) {
                if (opts.beforePageChange(curScrOffset, urlNextPage) === false) {
                    return;
                }
            }

            paging.pushPages(curScrOffset, urlNextPage);

            stop_scroll();
            show_loader();

            loadItems(urlNextPage, function (data, items) {
                // call the onLoadItems callback
                var result = opts.onLoadItems.call(this, items),
                    curLastItem;

                if (result !== false) {
                    $(items).hide();  // at first, hide it so we can fade it in later

                    // insert them after the last item with a nice fadeIn effect
                    curLastItem = $(opts.container).find(opts.item).last();
                    curLastItem.after(items);
                    $(items).fadeIn();
                }

                urlNextPage = $(opts.next, data).attr('href');

                // update pagination
                $(opts.pagination).replaceWith($(opts.pagination, data));

                remove_loader();
                hide_pagination();

                if (urlNextPage) {
                    reset();
                }
                else {
                    stop_scroll();
                }

                // call the onRenderComplete callback
                opts.onRenderComplete.call(this, items);

                if (onCompleteHandler) {
                    onCompleteHandler.call(this);
                }
            });
        }

        /**
         * Loads items from certain url, triggers
         * onComplete handler when finished
         *
         * @param string   the url to load
         * @param function the callback function
         * @param int      minimal time the loading should take, defaults to $.ias.default.loaderDelay
         * @return void
         */
        function loadItems(url, onCompleteHandler, delay)
        {
            var items = [],
                container,
                startTime = Date.now(),
                diffTime,
                self;

            delay = delay || opts.loaderDelay;

            $.get(url, null, function (data) {
                // walk through the items on the next page
                // and add them to the items array
                container = $(opts.container, data).eq(0);
                if (0 === container.length) {
                    // incase the element is a root element (body > element),
                    // try to filter it
                    container = $(data).filter(opts.container).eq(0);
                }

                if (container) {
                    container.find(opts.item).each(function () {
                        items.push(this);
                    });
                }

                if (onCompleteHandler) {
                    self = this;
                    diffTime = Date.now() - startTime;
                    if (diffTime < delay) {
                        setTimeout(function () {
                            onCompleteHandler.call(self, data, items);
                        }, delay - diffTime);
                    } else {
                        onCompleteHandler.call(self, data, items);
                    }
                }
            }, 'html');
        }

        /**
         * Paginate to a certain page number.
         *
         * - keeps paginating till the pageNum is reached
         *
         * @return void
         */
        function paginateToPage(pageNum)
        {
            var curThreshold = get_scroll_threshold(true);

            if (curThreshold > 0) {
                paginate(curThreshold, function () {
                    stop_scroll();

                    if ((paging.getCurPageNum(curThreshold) + 1) < pageNum) {
                        paginateToPage(pageNum);

                        $('html,body').animate({'scrollTop': curThreshold}, 400, 'swing');
                    }
                    else {
                        $('html,body').animate({'scrollTop': curThreshold}, 1000, 'swing');

                        reset();
                    }
                });
            }
        }

        function get_current_page()
        {
            var curScrOffset = util.getCurrentScrollOffset(opts.scrollContainer);

            return paging.getCurPageNum(curScrOffset);
        }

        /**
         * Return the active loader or creates a new loader
         *
         * @return object loader jquery object
         */
        function get_loader()
        {
            var loader = $('.ias_loader');

            if (loader.size() === 0) {
                loader = $('<div class="ias_loader">' + opts.loader + '</div>');
                loader.hide();
            }
            return loader;
        }

        /**
         * Inserts the loader and does a fadeIn.
         *
         * @return void
         */
        function show_loader()
        {
            var loader = get_loader(),
                el;

            if (opts.customLoaderProc !== false) {
                opts.customLoaderProc(loader);
            } else {
                el = $(opts.container).find(opts.item).last();
                el.after(loader);
                loader.fadeIn();
            }
        }

        /**
         * Removes the loader.
         *
         * return void
         */
        function remove_loader()
        {
            var loader = get_loader();
            loader.remove();
        }

        /**
         * Return the active trigger or creates a new trigger
         *
         * @return object trigger jquery object
         */
        function get_trigger(callback)
        {
            var trigger = $('.ias_trigger');

            if (trigger.size() === 0) {
                trigger = $('<div class="ias_trigger"><a href="#">' + opts.trigger + '</a></div>');
                trigger.hide();
            }

            $('a', trigger)
                .off('click')
                .on('click', function () { remove_trigger(); callback.call(); return false; })
            ;

            return trigger;
        }

        /**
         * @param function callback of the trigger (get's called onClick)
         */
        function show_trigger(callback)
        {
            var trigger = get_trigger(callback),
                el;

            el = $(opts.container).find(opts.item).last();
            el.after(trigger);
            trigger.fadeIn();
        }

        /**
         * Removes the trigger.
         *
         * return void
         */
        function remove_trigger()
        {
            var trigger = get_trigger();

            trigger.remove();
        }
    };

    // plugin defaults
    $.ias.defaults = {
        container: '#container',
        scrollContainer: $(window),
        item: '.item',
        pagination: '#pagination',
        next: '.next',
        noneleft: false,
        loader: '<img src="images/loader.gif"/>',
        loaderDelay: 600,
        triggerPageThreshold: 3,
        trigger: 'Load more items',
        thresholdMargin: 0,
        history : true,
        onPageChange: function () {},
        beforePageChange: function () {},
        onLoadItems: function () {},
        onRenderComplete: function () {},
        customLoaderProc: false
    };

    // utility module
    $.ias.util = function ()
    {
        // setup
        var wndIsLoaded = false;
        var forceScrollTopIsCompleted = false;
        var self = this;

        /**
         * Initialize
         *
         * @return void
         */
        function init()
        {
            $(window).load(function () {
                wndIsLoaded = true;
            });
        }

        // initialize
        init();

        /**
         * Force browsers to scroll to top.
         *
         * - When you hit back in you browser, it automatically scrolls
         *   back to the last position. There is no way to stop this
         *   in a nice way, so this function does it the hard way.
         *
         * @param function onComplete callback function
         * @return void
         */
        this.forceScrollTop = function (onCompleteHandler)
        {
            $('html,body').scrollTop(0);

            if (!forceScrollTopIsCompleted) {
                if (!wndIsLoaded) {
                    setTimeout(function () {self.forceScrollTop(onCompleteHandler); }, 1);
                } else {
                    onCompleteHandler.call();
                    forceScrollTopIsCompleted = true;
                }
            }
        };

        this.getCurrentScrollOffset = function (container)
        {
            var scrTop,
                wndHeight;

            // the way we calculate if we have to load the next page depends on which container we have
            if (container.get(0) === window) {
                scrTop = container.scrollTop();
            } else {
                scrTop = container.offset().top;
            }

            wndHeight = container.height();

            return scrTop + wndHeight;
        };
    };

    // paging module
    $.ias.paging = function ()
    {
        // setup
        var pagebreaks        = [[0, document.location.toString()]];
        var changePageHandler = function () {};
        var lastPageNum       = 1;
        var util              = new $.ias.util();

        /**
         * Initialize
         *
         * @return void
         */
        function init()
        {
            $(window).scroll(scroll_handler);
        }

        // initialize
        init();

        /**
         * Scroll handler
         *
         * - Triggers changePage event
         *
         * @return void
         */
        function scroll_handler()
        {
            var curScrOffset,
                curPageNum,
                curPagebreak,
                scrOffset,
                urlPage;

            curScrOffset = util.getCurrentScrollOffset($(window));

            curPageNum = getCurPageNum(curScrOffset);
            curPagebreak = getCurPagebreak(curScrOffset);

            if (lastPageNum !== curPageNum) {
                scrOffset = curPagebreak[0];
                urlPage = curPagebreak[1];
                changePageHandler.call({}, curPageNum, scrOffset, urlPage); // @todo fix for window height
            }

            lastPageNum = curPageNum;
        }

        /**
         * Returns current page number based on scroll offset
         *
         * @param int scroll offset
         * @return int current page number
         */
        function getCurPageNum(scrollOffset)
        {
            for (var i = (pagebreaks.length - 1); i > 0; i--) {
                if (scrollOffset > pagebreaks[i][0]) {
                    return i + 1;
                }
            }
            return 1;
        }

        /**
         * Public function for getCurPageNum
         *
         * @param int scrollOffset defaulst to the current
         * @return int current page number
         */
        this.getCurPageNum = function (scrollOffset)
        {
            scrollOffset = scrollOffset || util.getCurrentScrollOffset($(window));

            return getCurPageNum(scrollOffset);
        };

        /**
         * Returns current pagebreak information based on scroll offset
         *
         * @param int scroll offset
         * @return array pagebreak information
         */
        function getCurPagebreak(scrollOffset)
        {
            for (var i = (pagebreaks.length - 1); i >= 0; i--) {
                if (scrollOffset > pagebreaks[i][0]) {
                    return pagebreaks[i];
                }
            }
            return null;
        }

        /**
         * Sets onchangePage event handler
         *
         * @param function event handler
         * @return void
         */
        this.onChangePage = function (fn)
        {
            changePageHandler = fn;
        };

        /**
         * pushes the pages tracker
         *
         * @param int scroll offset for the new page
         * @return void
         */
        this.pushPages = function (scrollOffset, urlNextPage)
        {
            pagebreaks.push([scrollOffset, urlNextPage]);
        };
    };

    // history module
    $.ias.history = function ()
    {
        // setup
        var isPushed = false;
        var isHtml5 = false;

        /**
         * Initialize
         *
         * @return void
         */
        function init()
        {
            isHtml5 = !!(window.history && history.pushState && history.replaceState);
            isHtml5 = false; // html5 functions disabled due to problems in chrome
        }

        // initialize
        init();

        /**
         * Sets page to history
         *
         * @return void;
         */
        this.setPage = function (pageNum, pageUrl)
        {
            this.updateState({page : pageNum}, '', pageUrl);
        };

        /**
         * Checks if we have a page set in the history
         *
         * @return bool returns true when we have a previous page, false otherwise
         */
        this.havePage = function ()
        {
            return (this.getState() !== false);
        };

        /**
         * Gets the previous page from history
         *
         * @return int page number of previous page
         */
        this.getPage = function ()
        {
            var stateObj;

            if (this.havePage()) {
                stateObj = this.getState();
                return stateObj.page;
            }
            return 1;
        };

        /**
         * Returns current state
         *
         * @return object stateObj
         */
        this.getState = function ()
        {
            var haveState,
                stateObj,
                pageNum;

            if (isHtml5) {
                stateObj = history.state;
                if (stateObj && stateObj.ias) {
                    return stateObj.ias;
                }
            }
            else {
                haveState = (window.location.hash.substring(0, 7) === '#/page/');
                if (haveState) {
                    pageNum = parseInt(window.location.hash.replace('#/page/', ''), 10);
                    return { page : pageNum };
                }
            }

            return false;
        };

        /**
         * Pushes state when not pushed already, otherwise
         * replaces the state.
         *
         * @param obj stateObj
         * @param string title
         * @param string url
         * @return void
         */
        this.updateState = function (stateObj, title, url)
        {
            if (isPushed) {
                this.replaceState(stateObj, title, url);
            }
            else {
                this.pushState(stateObj, title, url);
            }
        };

        /**
         * Pushes state to history.
         *
         * @param obj stateObj
         * @param string title
         * @param string url
         * @return void
         */
        this.pushState = function (stateObj, title, url)
        {
            var hash;

            if (isHtml5) {
                history.pushState({ ias : stateObj }, title, url);
            }
            else {
                hash = (stateObj.page > 0 ? '#/page/' + stateObj.page : '');
                window.location.hash = hash;
            }

            isPushed = true;
        };

        /**
         * Replaces current history state.
         *
         * @param obj stateObj
         * @param string title
         * @param string url
         * @return void
         */
        this.replaceState = function (stateObj, title, url)
        {
            if (isHtml5) {
                history.replaceState({ ias : stateObj }, title, url);
            }
            else {
                this.pushState(stateObj, title, url);
            }
        };
    };
})(jQuery);