/*
**	history for ajax/javascript history
**		0.3 history events now setup in queue to ensure all entries reside in the history stack
**		0.2 no more FORM GET submission, straight location.href instead + hold time for iframe load
**		0.1 hidden frame + not bookmarkable + stores data for state change + allows reinstating data on forw/back hit
**	authored by Jim Palmer - released under MIT license
**  collage of ideas from Taku Sano, Mikage Sawatari, david bloom and Klaus Hartl
*/
(function($) {

    $.history = function(store) {

        // (initialize) create the hidden iframe if not on the root window.document.body
        if ($(".__historyFrame").length == 0) {

            // set the history cursor to (-1) - this will be populated with current unix timestamp or 0 for the first screen
            $.history.cursor = $.history.intervalId = 0;
            // initialize the stack of history stored entries
            $.history.stack = {};
            // initialize the stack of loading hold flags
            $.history._loading = {};
            // initialize the queue for loading history fragments in sequence
            $.history._queue = [];

            // append to the root window.document.body without the src - uses class for toggleClass debugging - display:none doesn't work
            $("body").append('<iframe class="__historyFrame" src="/blank.html" style="border:0px; width:0px; height:0px; visibility:hidden;" />');

            // set the src (safari doesnt load the src if set in the append above)  + set the onLoad event for the iframe
            $('.__historyFrame').load(function() {

                // parse out the current cursor from the location/URL
                var cursor = $(this).contents().attr($.browser.msie ? 'URL' : 'location').toString().split('#')[1];
                if (cursor) {
                    // remove the cursor from the load queue
                    var qPos = $.inArray(cursor, $.history._queue);
                    if (qPos > -1)
                        $.history._queue.splice(qPos, 1);
                    // flag that the iframe is done loading the new fragment id
                    $.history._loading[cursor] = false;
                }

                // setup interval function to check for changes in "history" via iframe hash and call appropriate callback function to handle it
                $.history.intervalId = $.history.intervalId || window.setInterval(function() {
                    // if any cursors in queue - load first cursor (FIFO)
                    if ($.history._queue.length > 0 && !$.history._loading[$.history._queue[0]]) {
                        // flag this queued cursor as loading so this interval will not load more than once
                        $.history._loading[$.history._queue[0]] = true;
                        // move the history cursor in the hidden iframe to the newest fragment identifier
                        $('.__historyFrame').contents()[0].location.href =
									$('.__historyFrame').contents().attr($.browser.msie ? 'URL' : 'location').toString().replace(/[\?|#]{1}(.*)$/gi, '') +
									'?' + $.history._queue[0] + '#' + $.history._queue[0];
                    } else if ($.history._queue.length == 0) {
                        // fetch current cursor from the iframe document.URL or document.location depending on browser support
                        var cursor = $(".__historyFrame").contents().attr($.browser.msie ? 'URL' : 'location').toString().split('#')[1];
                        // display debugging information if block id exists
                        $('#__historyDebug').html('"' + $.history.cursor + '" vs "' + cursor + '" - ' + (new Date()).toString());
                        // if cursors are different (forw/back hit) then reinstate data only when iframe is done loading
                        if (parseFloat($.history.cursor) >= 0 && parseFloat($.history.cursor) != (parseFloat(cursor) || 0)) {
                            // set the history cursor to the current cursor
                            $.history.cursor = parseFloat(cursor) || 0;
                            // reinstate the current cursor data through the callback
                            if (typeof ($.history.callback) == 'function')
                                $.history.callback($.history.stack[cursor], cursor);
                        }
                    }
                }, 150);

            });

        } else {			// handle new history entries apre-initialization

            // set the current unix timestamp for our history
            $.history.cursor = (new Date()).getTime().toString();
            // add this cursor fragment id into the queue to be loaded by the checking function interval
            $.history._queue.push($.history.cursor);
            // insert into the stack with current cursor
            $.history.stack[$.history.cursor] = store;
        }

    }

    // pre-initialize the history functionality - if you include this plugin this will be loaded as a singleton at time of the root window.onLoad
    $(document).ready(function() { $.history(); });

})(jQuery);