(function($) { // block scope

$.ajaxHistory = new function() {

    var RESET_EVENT = 'historyReset';

    var _currentHash = location.hash;
    var _intervalId = null;
    var _observeHistory; // define outside if/else required by Opera

    this.update = function() { }; // empty function body for graceful degradation

    // create custom event for state reset
    var _defaultReset = function() {
        $('.remote-output').empty();
    };
    $(document).bind(RESET_EVENT, _defaultReset);

    if ($.browser.msie) {

        var _historyIframe, initialized = false; // for IE

        // add hidden iframe
        $(function() {
            _historyIframe = $('<iframe style="display: none;"></iframe>').appendTo(document.body).get(0);
            var iframe = _historyIframe.contentWindow.document;
            // create initial history entry
            iframe.open();
            iframe.close();
            if (_currentHash && _currentHash != '#') {
                iframe.location.hash = _currentHash.replace('#', '');
            }
        });

        this.update = function(hash) {
            _currentHash = hash;
            var iframe = _historyIframe.contentWindow.document;
            iframe.open();
            iframe.close();
            iframe.location.hash = hash.replace('#', '');
        };

        _observeHistory = function() {
            var iframe = _historyIframe.contentWindow.document;
            var iframeHash = iframe.location.hash;
            if (iframeHash != _currentHash) {
                _currentHash = iframeHash;
                if (iframeHash && iframeHash != '#') {
                    // order does matter, set location.hash after triggering the click...
                    $('a[@href$="' + iframeHash + '"]').click();
                    location.hash = iframeHash;
                } else if (initialized) {
                    location.hash = '';
                    $(document).trigger(RESET_EVENT);
                }
            }
            initialized = true;
        };

    } else if ($.browser.mozilla || $.browser.opera) {

        this.update = function(hash) {
            _currentHash = hash;
        };

        _observeHistory = function() {
            if (location.hash) {
                if (_currentHash != location.hash) {
                    _currentHash = location.hash;
                    $('a[@href$="' + _currentHash + '"]').click();
                }
            } else if (_currentHash) {
                _currentHash = '';
                $(document).trigger(RESET_EVENT);
            }
        };

    } else if ($.browser.safari) {

        var _backStack, _forwardStack, _addHistory; // for Safari

        // etablish back/forward stacks
        $(function() {
            _backStack = [];
            _backStack.length = history.length;
            _forwardStack = [];

        });
        var isFirst = false, initialized = false;
        _addHistory = function(hash) {
            _backStack.push(hash);
            _forwardStack.length = 0; // clear forwardStack (true click occured)
            isFirst = false;
        };

        this.update = function(hash) {
            _currentHash = hash;
            _addHistory(_currentHash);
        };

        _observeHistory = function() {
            var historyDelta = history.length - _backStack.length;
            if (historyDelta) { // back or forward button has been pushed
                isFirst = false;
                if (historyDelta < 0) { // back button has been pushed
                    // move items to forward stack
                    for (var i = 0; i < Math.abs(historyDelta); i++) _forwardStack.unshift(_backStack.pop());
                } else { // forward button has been pushed
                    // move items to back stack
                    for (var i = 0; i < historyDelta; i++) _backStack.push(_forwardStack.shift());
                }
                var cachedHash = _backStack[_backStack.length - 1];
                $('a[@href$="' + cachedHash + '"]').click();
                _currentHash = location.hash;
            } else if (_backStack[_backStack.length - 1] == undefined && !isFirst) {
                // back button has been pushed to beginning and URL already pointed to hash (e.g. a bookmark)
                // document.URL doesn't change in Safari
                if (document.URL.indexOf('#') >= 0) {
                    $('a[@href$="' + '#' + document.URL.split('#')[1] + '"]').click();
                } else if (initialized) {
                    $(document).trigger(RESET_EVENT);
                }
                isFirst = true;
            }
            initialized = true;
        };

    }

    this.initialize = function(callback) {
        // custom callback to reset app state (no hash in url)
        if (typeof callback == 'function') {
            $(document).unbind(RESET_EVENT, _defaultReset).bind(RESET_EVENT, callback);
        }
        // look for hash in current URL (not Safari)
        if (location.hash && typeof _addHistory == 'undefined') {
            $('a[@href$="' + location.hash + '"]').trigger('click');
        }
        // start observer
        if (_observeHistory && _intervalId == null) {
            _intervalId = setInterval(_observeHistory, 200); // Safari needs at least 200 ms
        }
    };

};

$.fn.remote = function(output, settings, callback) {

    callback = callback || function() {};
    if (typeof settings == 'function') { // shift arguments
        callback = settings;
    }

    settings = $.extend({
        hashPrefix: 'remote-',
        useAttr: '',
        beforeLoad: function() {}
    }, settings || {});

    var target = $(output).size() && $(output) || $('<div></div>').appendTo('body');
    target.addClass('remote-output');

    return this.each(function(i) {
        var href = this.href;
        var hash = '#';
        if (settings.useAttr != '') {
          var hashattrvalue = $(this).attr(settings.useAttr);
          if (hashattrvalue) {
            hash += hashattrvalue.replace(/\s/g, '_');
          }
        }
        if (hash == '#') {
          hash += settings.hashPrefix + (i + 1);
        }
//        var hash = '#' + ((settings.useTitleAttr && this.title && this.title.replace(/\s/g, '_')) || (settings.hashPrefix + (i + 1)) );
        this.href = hash;
        $(this).click(function(e) {
            // lock target to prevent double loading in Firefox
            if (!target['locked']) {
                // add to history only if true click occured, not a triggered click
                if (e.clientX) {
                    $.ajaxHistory.update(hash);
                }
                settings.beforeLoad();
                target.load(href, function() {
                    target['locked'] = null;
                    callback();
                });
            }
        });
    });

};

/**
 * Provides the ability to use the back/forward navigation buttons in a DHTML application.
 * A change of the application state is reflected by a change of the URL fragment identifier.
 *
 * The link's href attribute needs to point to a fragment identifier within the same resource,
 * although that fragment id does not need to exist. On click the link changes the URL fragment
 * identifier, informs the history manager of the state change and adds an entry to the browser's
 * history.
 *
 * @param Function callback A single function that will be executed as the click handler of the
 *                          matched element. It will be executed on click (adding an entry to
 *                          the history) as well as in case the history manager needs to trigger
 *                          it depending on the value of the URL fragment identifier, e.g. if its
 *                          current value matches the href attribute of the matched element.
 *
 * @type jQuery
 *
 * @name history
 * @cat Plugins/History
 * @author Klaus Hartl/klaus.hartl@stilbuero.de
 */
$.fn.history = function(callback) {
    return this.click(function(e) {
        // add to history only if true click occured, not a triggered click
        if (e.clientX) {
            $.ajaxHistory.update(this.hash);
        }
        typeof callback == 'function' && callback();
    });
};

})(jQuery);