fullcalendar/src/util.js

// exports
FC.intersectRanges = intersectRanges;
FC.applyAll = applyAll;
FC.debounce = debounce;
FC.isInt = isInt;
FC.htmlEscape = htmlEscape;
FC.cssToStr = cssToStr;
FC.proxy = proxy;
FC.capitaliseFirstLetter = capitaliseFirstLetter;


/* FullCalendar-specific DOM Utilities
----------------------------------------------------------------------------------------------------------------------*/


// Given the scrollbar widths of some other container, create borders/margins on rowEls in order to match the left
// and right space that was offset by the scrollbars. A 1-pixel border first, then margin beyond that.
function compensateScroll(rowEls, scrollbarWidths) {
	if (scrollbarWidths.left) {
		rowEls.css({
			'border-left-width': 1,
			'margin-left': scrollbarWidths.left - 1
		});
	}
	if (scrollbarWidths.right) {
		rowEls.css({
			'border-right-width': 1,
			'margin-right': scrollbarWidths.right - 1
		});
	}
}


// Undoes compensateScroll and restores all borders/margins
function uncompensateScroll(rowEls) {
	rowEls.css({
		'margin-left': '',
		'margin-right': '',
		'border-left-width': '',
		'border-right-width': ''
	});
}


// Make the mouse cursor express that an event is not allowed in the current area
function disableCursor() {
	$('body').addClass('fc-not-allowed');
}


// Returns the mouse cursor to its original look
function enableCursor() {
	$('body').removeClass('fc-not-allowed');
}


// Given a total available height to fill, have `els` (essentially child rows) expand to accomodate.
// By default, all elements that are shorter than the recommended height are expanded uniformly, not considering
// any other els that are already too tall. if `shouldRedistribute` is on, it considers these tall rows and 
// reduces the available height.
function distributeHeight(els, availableHeight, shouldRedistribute) {

	// *FLOORING NOTE*: we floor in certain places because zoom can give inaccurate floating-point dimensions,
	// and it is better to be shorter than taller, to avoid creating unnecessary scrollbars.

	var minOffset1 = Math.floor(availableHeight / els.length); // for non-last element
	var minOffset2 = Math.floor(availableHeight - minOffset1 * (els.length - 1)); // for last element *FLOORING NOTE*
	var flexEls = []; // elements that are allowed to expand. array of DOM nodes
	var flexOffsets = []; // amount of vertical space it takes up
	var flexHeights = []; // actual css height
	var usedHeight = 0;

	undistributeHeight(els); // give all elements their natural height

	// find elements that are below the recommended height (expandable).
	// important to query for heights in a single first pass (to avoid reflow oscillation).
	els.each(function(i, el) {
		var minOffset = i === els.length - 1 ? minOffset2 : minOffset1;
		var naturalOffset = $(el).outerHeight(true);

		if (naturalOffset < minOffset) {
			flexEls.push(el);
			flexOffsets.push(naturalOffset);
			flexHeights.push($(el).height());
		}
		else {
			// this element stretches past recommended height (non-expandable). mark the space as occupied.
			usedHeight += naturalOffset;
		}
	});

	// readjust the recommended height to only consider the height available to non-maxed-out rows.
	if (shouldRedistribute) {
		availableHeight -= usedHeight;
		minOffset1 = Math.floor(availableHeight / flexEls.length);
		minOffset2 = Math.floor(availableHeight - minOffset1 * (flexEls.length - 1)); // *FLOORING NOTE*
	}

	// assign heights to all expandable elements
	$(flexEls).each(function(i, el) {
		var minOffset = i === flexEls.length - 1 ? minOffset2 : minOffset1;
		var naturalOffset = flexOffsets[i];
		var naturalHeight = flexHeights[i];
		var newHeight = minOffset - (naturalOffset - naturalHeight); // subtract the margin/padding

		if (naturalOffset < minOffset) { // we check this again because redistribution might have changed things
			$(el).height(newHeight);
		}
	});
}


// Undoes distrubuteHeight, restoring all els to their natural height
function undistributeHeight(els) {
	els.height('');
}


// Given `els`, a jQuery set of <td> cells, find the cell with the largest natural width and set the widths of all the
// cells to be that width.
// PREREQUISITE: if you want a cell to take up width, it needs to have a single inner element w/ display:inline
function matchCellWidths(els) {
	var maxInnerWidth = 0;

	els.find('> span').each(function(i, innerEl) {
		var innerWidth = $(innerEl).outerWidth();
		if (innerWidth > maxInnerWidth) {
			maxInnerWidth = innerWidth;
		}
	});

	maxInnerWidth++; // sometimes not accurate of width the text needs to stay on one line. insurance

	els.width(maxInnerWidth);

	return maxInnerWidth;
}


// Given one element that resides inside another,
// Subtracts the height of the inner element from the outer element.
function subtractInnerElHeight(outerEl, innerEl) {
	var both = outerEl.add(innerEl);
	var diff;

	// effin' IE8/9/10/11 sometimes returns 0 for dimensions. this weird hack was the only thing that worked
	both.css({
		position: 'relative', // cause a reflow, which will force fresh dimension recalculation
		left: -1 // ensure reflow in case the el was already relative. negative is less likely to cause new scroll
	});
	diff = outerEl.outerHeight() - innerEl.outerHeight(); // grab the dimensions
	both.css({ position: '', left: '' }); // undo hack

	return diff;
}


/* Element Geom Utilities
----------------------------------------------------------------------------------------------------------------------*/

FC.getOuterRect = getOuterRect;
FC.getClientRect = getClientRect;
FC.getContentRect = getContentRect;
FC.getScrollbarWidths = getScrollbarWidths;


// borrowed from https://github.com/jquery/jquery-ui/blob/1.11.0/ui/core.js#L51
function getScrollParent(el) {
	var position = el.css('position'),
		scrollParent = el.parents().filter(function() {
			var parent = $(this);
			return (/(auto|scroll)/).test(
				parent.css('overflow') + parent.css('overflow-y') + parent.css('overflow-x')
			);
		}).eq(0);

	return position === 'fixed' || !scrollParent.length ? $(el[0].ownerDocument || document) : scrollParent;
}


// Queries the outer bounding area of a jQuery element.
// Returns a rectangle with absolute coordinates: left, right (exclusive), top, bottom (exclusive).
// Origin is optional.
function getOuterRect(el, origin) {
	var offset = el.offset();
	var left = offset.left - (origin ? origin.left : 0);
	var top = offset.top - (origin ? origin.top : 0);

	return {
		left: left,
		right: left + el.outerWidth(),
		top: top,
		bottom: top + el.outerHeight()
	};
}


// Queries the area within the margin/border/scrollbars of a jQuery element. Does not go within the padding.
// Returns a rectangle with absolute coordinates: left, right (exclusive), top, bottom (exclusive).
// Origin is optional.
// NOTE: should use clientLeft/clientTop, but very unreliable cross-browser.
function getClientRect(el, origin) {
	var offset = el.offset();
	var scrollbarWidths = getScrollbarWidths(el);
	var left = offset.left + getCssFloat(el, 'border-left-width') + scrollbarWidths.left - (origin ? origin.left : 0);
	var top = offset.top + getCssFloat(el, 'border-top-width') + scrollbarWidths.top - (origin ? origin.top : 0);

	return {
		left: left,
		right: left + el[0].clientWidth, // clientWidth includes padding but NOT scrollbars
		top: top,
		bottom: top + el[0].clientHeight // clientHeight includes padding but NOT scrollbars
	};
}


// Queries the area within the margin/border/padding of a jQuery element. Assumed not to have scrollbars.
// Returns a rectangle with absolute coordinates: left, right (exclusive), top, bottom (exclusive).
// Origin is optional.
function getContentRect(el, origin) {
	var offset = el.offset(); // just outside of border, margin not included
	var left = offset.left + getCssFloat(el, 'border-left-width') + getCssFloat(el, 'padding-left') -
		(origin ? origin.left : 0);
	var top = offset.top + getCssFloat(el, 'border-top-width') + getCssFloat(el, 'padding-top') -
		(origin ? origin.top : 0);

	return {
		left: left,
		right: left + el.width(),
		top: top,
		bottom: top + el.height()
	};
}


// Returns the computed left/right/top/bottom scrollbar widths for the given jQuery element.
// NOTE: should use clientLeft/clientTop, but very unreliable cross-browser.
function getScrollbarWidths(el) {
	var leftRightWidth = el.innerWidth() - el[0].clientWidth; // the paddings cancel out, leaving the scrollbars
	var widths = {
		left: 0,
		right: 0,
		top: 0,
		bottom: el.innerHeight() - el[0].clientHeight // the paddings cancel out, leaving the bottom scrollbar
	};

	if (getIsLeftRtlScrollbars() && el.css('direction') == 'rtl') { // is the scrollbar on the left side?
		widths.left = leftRightWidth;
	}
	else {
		widths.right = leftRightWidth;
	}

	return widths;
}


// Logic for determining if, when the element is right-to-left, the scrollbar appears on the left side

var _isLeftRtlScrollbars = null;

function getIsLeftRtlScrollbars() { // responsible for caching the computation
	if (_isLeftRtlScrollbars === null) {
		_isLeftRtlScrollbars = computeIsLeftRtlScrollbars();
	}
	return _isLeftRtlScrollbars;
}

function computeIsLeftRtlScrollbars() { // creates an offscreen test element, then removes it
	var el = $('<div><div/></div>')
		.css({
			position: 'absolute',
			top: -1000,
			left: 0,
			border: 0,
			padding: 0,
			overflow: 'scroll',
			direction: 'rtl'
		})
		.appendTo('body');
	var innerEl = el.children();
	var res = innerEl.offset().left > el.offset().left; // is the inner div shifted to accommodate a left scrollbar?
	el.remove();
	return res;
}


// Retrieves a jQuery element's computed CSS value as a floating-point number.
// If the queried value is non-numeric (ex: IE can return "medium" for border width), will just return zero.
function getCssFloat(el, prop) {
	return parseFloat(el.css(prop)) || 0;
}


/* Mouse / Touch Utilities
----------------------------------------------------------------------------------------------------------------------*/

FC.preventDefault = preventDefault;


// Returns a boolean whether this was a left mouse click and no ctrl key (which means right click on Mac)
function isPrimaryMouseButton(ev) {
	return ev.which == 1 && !ev.ctrlKey;
}


function getEvX(ev) {
	if (ev.pageX !== undefined) {
		return ev.pageX;
	}
	var touches = ev.originalEvent.touches;
	if (touches) {
		return touches[0].pageX;
	}
}


function getEvY(ev) {
	if (ev.pageY !== undefined) {
		return ev.pageY;
	}
	var touches = ev.originalEvent.touches;
	if (touches) {
		return touches[0].pageY;
	}
}


function getEvIsTouch(ev) {
	return /^touch/.test(ev.type);
}


function preventSelection(el) {
	el.addClass('fc-unselectable')
		.on('selectstart', preventDefault);
}


// Stops a mouse/touch event from doing it's native browser action
function preventDefault(ev) {
	ev.preventDefault();
}


// attach a handler to get called when ANY scroll action happens on the page.
// this was impossible to do with normal on/off because 'scroll' doesn't bubble.
// http://stackoverflow.com/a/32954565/96342
// returns `true` on success.
function bindAnyScroll(handler) {
	if (window.addEventListener) {
		window.addEventListener('scroll', handler, true); // useCapture=true
		return true;
	}
	return false;
}


// undoes bindAnyScroll. must pass in the original function.
// returns `true` on success.
function unbindAnyScroll(handler) {
	if (window.removeEventListener) {
		window.removeEventListener('scroll', handler, true); // useCapture=true
		return true;
	}
	return false;
}


/* General Geometry Utils
----------------------------------------------------------------------------------------------------------------------*/

FC.intersectRects = intersectRects;

// Returns a new rectangle that is the intersection of the two rectangles. If they don't intersect, returns false
function intersectRects(rect1, rect2) {
	var res = {
		left: Math.max(rect1.left, rect2.left),
		right: Math.min(rect1.right, rect2.right),
		top: Math.max(rect1.top, rect2.top),
		bottom: Math.min(rect1.bottom, rect2.bottom)
	};

	if (res.left < res.right && res.top < res.bottom) {
		return res;
	}
	return false;
}


// Returns a new point that will have been moved to reside within the given rectangle
function constrainPoint(point, rect) {
	return {
		left: Math.min(Math.max(point.left, rect.left), rect.right),
		top: Math.min(Math.max(point.top, rect.top), rect.bottom)
	};
}


// Returns a point that is the center of the given rectangle
function getRectCenter(rect) {
	return {
		left: (rect.left + rect.right) / 2,
		top: (rect.top + rect.bottom) / 2
	};
}


// Subtracts point2's coordinates from point1's coordinates, returning a delta
function diffPoints(point1, point2) {
	return {
		left: point1.left - point2.left,
		top: point1.top - point2.top
	};
}


/* Object Ordering by Field
----------------------------------------------------------------------------------------------------------------------*/

FC.parseFieldSpecs = parseFieldSpecs;
FC.compareByFieldSpecs = compareByFieldSpecs;
FC.compareByFieldSpec = compareByFieldSpec;
FC.flexibleCompare = flexibleCompare;


function parseFieldSpecs(input) {
	var specs = [];
	var tokens = [];
	var i, token;

	if (typeof input === 'string') {
		tokens = input.split(/\s*,\s*/);
	}
	else if (typeof input === 'function') {
		tokens = [ input ];
	}
	else if ($.isArray(input)) {
		tokens = input;
	}

	for (i = 0; i < tokens.length; i++) {
		token = tokens[i];

		if (typeof token === 'string') {
			specs.push(
				token.charAt(0) == '-' ?
					{ field: token.substring(1), order: -1 } :
					{ field: token, order: 1 }
			);
		}
		else if (typeof token === 'function') {
			specs.push({ func: token });
		}
	}

	return specs;
}


function compareByFieldSpecs(obj1, obj2, fieldSpecs) {
	var i;
	var cmp;

	for (i = 0; i < fieldSpecs.length; i++) {
		cmp = compareByFieldSpec(obj1, obj2, fieldSpecs[i]);
		if (cmp) {
			return cmp;
		}
	}

	return 0;
}


function compareByFieldSpec(obj1, obj2, fieldSpec) {
	if (fieldSpec.func) {
		return fieldSpec.func(obj1, obj2);
	}
	return flexibleCompare(obj1[fieldSpec.field], obj2[fieldSpec.field]) *
		(fieldSpec.order || 1);
}


function flexibleCompare(a, b) {
	if (!a && !b) {
		return 0;
	}
	if (b == null) {
		return -1;
	}
	if (a == null) {
		return 1;
	}
	if ($.type(a) === 'string' || $.type(b) === 'string') {
		return String(a).localeCompare(String(b));
	}
	return a - b;
}


/* FullCalendar-specific Misc Utilities
----------------------------------------------------------------------------------------------------------------------*/


// Computes the intersection of the two ranges. Returns undefined if no intersection.
// Expects all dates to be normalized to the same timezone beforehand.
// TODO: move to date section?
function intersectRanges(subjectRange, constraintRange) {
	var subjectStart = subjectRange.start;
	var subjectEnd = subjectRange.end;
	var constraintStart = constraintRange.start;
	var constraintEnd = constraintRange.end;
	var segStart, segEnd;
	var isStart, isEnd;

	if (subjectEnd > constraintStart && subjectStart < constraintEnd) { // in bounds at all?

		if (subjectStart >= constraintStart) {
			segStart = subjectStart.clone();
			isStart = true;
		}
		else {
			segStart = constraintStart.clone();
			isStart =  false;
		}

		if (subjectEnd <= constraintEnd) {
			segEnd = subjectEnd.clone();
			isEnd = true;
		}
		else {
			segEnd = constraintEnd.clone();
			isEnd = false;
		}

		return {
			start: segStart,
			end: segEnd,
			isStart: isStart,
			isEnd: isEnd
		};
	}
}


/* Date Utilities
----------------------------------------------------------------------------------------------------------------------*/

FC.computeIntervalUnit = computeIntervalUnit;
FC.divideRangeByDuration = divideRangeByDuration;
FC.divideDurationByDuration = divideDurationByDuration;
FC.multiplyDuration = multiplyDuration;
FC.durationHasTime = durationHasTime;

var dayIDs = [ 'sun', 'mon', 'tue', 'wed', 'thu', 'fri', 'sat' ];
var intervalUnits = [ 'year', 'month', 'week', 'day', 'hour', 'minute', 'second', 'millisecond' ];


// Diffs the two moments into a Duration where full-days are recorded first, then the remaining time.
// Moments will have their timezones normalized.
function diffDayTime(a, b) {
	return moment.duration({
		days: a.clone().stripTime().diff(b.clone().stripTime(), 'days'),
		ms: a.time() - b.time() // time-of-day from day start. disregards timezone
	});
}


// Diffs the two moments via their start-of-day (regardless of timezone). Produces whole-day durations.
function diffDay(a, b) {
	return moment.duration({
		days: a.clone().stripTime().diff(b.clone().stripTime(), 'days')
	});
}


// Diffs two moments, producing a duration, made of a whole-unit-increment of the given unit. Uses rounding.
function diffByUnit(a, b, unit) {
	return moment.duration(
		Math.round(a.diff(b, unit, true)), // returnFloat=true
		unit
	);
}


// Computes the unit name of the largest whole-unit period of time.
// For example, 48 hours will be "days" whereas 49 hours will be "hours".
// Accepts start/end, a range object, or an original duration object.
function computeIntervalUnit(start, end) {
	var i, unit;
	var val;

	for (i = 0; i < intervalUnits.length; i++) {
		unit = intervalUnits[i];
		val = computeRangeAs(unit, start, end);

		if (val >= 1 && isInt(val)) {
			break;
		}
	}

	return unit; // will be "milliseconds" if nothing else matches
}


// Computes the number of units (like "hours") in the given range.
// Range can be a {start,end} object, separate start/end args, or a Duration.
// Results are based on Moment's .as() and .diff() methods, so results can depend on internal handling
// of month-diffing logic (which tends to vary from version to version).
function computeRangeAs(unit, start, end) {

	if (end != null) { // given start, end
		return end.diff(start, unit, true);
	}
	else if (moment.isDuration(start)) { // given duration
		return start.as(unit);
	}
	else { // given { start, end } range object
		return start.end.diff(start.start, unit, true);
	}
}


// Intelligently divides a range (specified by a start/end params) by a duration
function divideRangeByDuration(start, end, dur) {
	var months;

	if (durationHasTime(dur)) {
		return (end - start) / dur;
	}
	months = dur.asMonths();
	if (Math.abs(months) >= 1 && isInt(months)) {
		return end.diff(start, 'months', true) / months;
	}
	return end.diff(start, 'days', true) / dur.asDays();
}


// Intelligently divides one duration by another
function divideDurationByDuration(dur1, dur2) {
	var months1, months2;

	if (durationHasTime(dur1) || durationHasTime(dur2)) {
		return dur1 / dur2;
	}
	months1 = dur1.asMonths();
	months2 = dur2.asMonths();
	if (
		Math.abs(months1) >= 1 && isInt(months1) &&
		Math.abs(months2) >= 1 && isInt(months2)
	) {
		return months1 / months2;
	}
	return dur1.asDays() / dur2.asDays();
}


// Intelligently multiplies a duration by a number
function multiplyDuration(dur, n) {
	var months;

	if (durationHasTime(dur)) {
		return moment.duration(dur * n);
	}
	months = dur.asMonths();
	if (Math.abs(months) >= 1 && isInt(months)) {
		return moment.duration({ months: months * n });
	}
	return moment.duration({ days: dur.asDays() * n });
}


// Returns a boolean about whether the given duration has any time parts (hours/minutes/seconds/ms)
function durationHasTime(dur) {
	return Boolean(dur.hours() || dur.minutes() || dur.seconds() || dur.milliseconds());
}


function isNativeDate(input) {
	return  Object.prototype.toString.call(input) === '[object Date]' || input instanceof Date;
}


// Returns a boolean about whether the given input is a time string, like "06:40:00" or "06:00"
function isTimeString(str) {
	return /^\d+\:\d+(?:\:\d+\.?(?:\d{3})?)?$/.test(str);
}


/* Logging and Debug
----------------------------------------------------------------------------------------------------------------------*/

FC.log = function() {
	var console = window.console;

	if (console && console.log) {
		return console.log.apply(console, arguments);
	}
};

FC.warn = function() {
	var console = window.console;

	if (console && console.warn) {
		return console.warn.apply(console, arguments);
	}
	else {
		return FC.log.apply(FC, arguments);
	}
};


/* General Utilities
----------------------------------------------------------------------------------------------------------------------*/

var hasOwnPropMethod = {}.hasOwnProperty;


// Merges an array of objects into a single object.
// The second argument allows for an array of property names who's object values will be merged together.
function mergeProps(propObjs, complexProps) {
	var dest = {};
	var i, name;
	var complexObjs;
	var j, val;
	var props;

	if (complexProps) {
		for (i = 0; i < complexProps.length; i++) {
			name = complexProps[i];
			complexObjs = [];

			// collect the trailing object values, stopping when a non-object is discovered
			for (j = propObjs.length - 1; j >= 0; j--) {
				val = propObjs[j][name];

				if (typeof val === 'object') {
					complexObjs.unshift(val);
				}
				else if (val !== undefined) {
					dest[name] = val; // if there were no objects, this value will be used
					break;
				}
			}

			// if the trailing values were objects, use the merged value
			if (complexObjs.length) {
				dest[name] = mergeProps(complexObjs);
			}
		}
	}

	// copy values into the destination, going from last to first
	for (i = propObjs.length - 1; i >= 0; i--) {
		props = propObjs[i];

		for (name in props) {
			if (!(name in dest)) { // if already assigned by previous props or complex props, don't reassign
				dest[name] = props[name];
			}
		}
	}

	return dest;
}


// Create an object that has the given prototype. Just like Object.create
function createObject(proto) {
	var f = function() {};
	f.prototype = proto;
	return new f();
}


function copyOwnProps(src, dest) {
	for (var name in src) {
		if (hasOwnProp(src, name)) {
			dest[name] = src[name];
		}
	}
}


// Copies over certain methods with the same names as Object.prototype methods. Overcomes an IE<=8 bug:
// https://developer.mozilla.org/en-US/docs/ECMAScript_DontEnum_attribute#JScript_DontEnum_Bug
function copyNativeMethods(src, dest) {
	var names = [ 'constructor', 'toString', 'valueOf' ];
	var i, name;

	for (i = 0; i < names.length; i++) {
		name = names[i];

		if (src[name] !== Object.prototype[name]) {
			dest[name] = src[name];
		}
	}
}


function hasOwnProp(obj, name) {
	return hasOwnPropMethod.call(obj, name);
}


// Is the given value a non-object non-function value?
function isAtomic(val) {
	return /undefined|null|boolean|number|string/.test($.type(val));
}


function applyAll(functions, thisObj, args) {
	if ($.isFunction(functions)) {
		functions = [ functions ];
	}
	if (functions) {
		var i;
		var ret;
		for (i=0; i<functions.length; i++) {
			ret = functions[i].apply(thisObj, args) || ret;
		}
		return ret;
	}
}


function firstDefined() {
	for (var i=0; i<arguments.length; i++) {
		if (arguments[i] !== undefined) {
			return arguments[i];
		}
	}
}


function htmlEscape(s) {
	return (s + '').replace(/&/g, '&amp;')
		.replace(/</g, '&lt;')
		.replace(/>/g, '&gt;')
		.replace(/'/g, '&#039;')
		.replace(/"/g, '&quot;')
		.replace(/\n/g, '<br />');
}


function stripHtmlEntities(text) {
	return text.replace(/&.*?;/g, '');
}


// Given a hash of CSS properties, returns a string of CSS.
// Uses property names as-is (no camel-case conversion). Will not make statements for null/undefined values.
function cssToStr(cssProps) {
	var statements = [];

	$.each(cssProps, function(name, val) {
		if (val != null) {
			statements.push(name + ':' + val);
		}
	});

	return statements.join(';');
}


function capitaliseFirstLetter(str) {
	return str.charAt(0).toUpperCase() + str.slice(1);
}


function compareNumbers(a, b) { // for .sort()
	return a - b;
}


function isInt(n) {
	return n % 1 === 0;
}


// Returns a method bound to the given object context.
// Just like one of the jQuery.proxy signatures, but without the undesired behavior of treating the same method with
// different contexts as identical when binding/unbinding events.
function proxy(obj, methodName) {
	var method = obj[methodName];

	return function() {
		return method.apply(obj, arguments);
	};
}


// Returns a function, that, as long as it continues to be invoked, will not
// be triggered. The function will be called after it stops being called for
// N milliseconds. If `immediate` is passed, trigger the function on the
// leading edge, instead of the trailing.
// https://github.com/jashkenas/underscore/blob/1.6.0/underscore.js#L714
function debounce(func, wait, immediate) {
	var timeout, args, context, timestamp, result;

	var later = function() {
		var last = +new Date() - timestamp;
		if (last < wait) {
			timeout = setTimeout(later, wait - last);
		}
		else {
			timeout = null;
			if (!immediate) {
				result = func.apply(context, args);
				context = args = null;
			}
		}
	};

	return function() {
		context = this;
		args = arguments;
		timestamp = +new Date();
		var callNow = immediate && !timeout;
		if (!timeout) {
			timeout = setTimeout(later, wait);
		}
		if (callNow) {
			result = func.apply(context, args);
			context = args = null;
		}
		return result;
	};
}


// HACK around jQuery's now A+ promises: execute callback synchronously if already resolved.
// thenFunc shouldn't accept args.
// similar to whenResources in Scheduler plugin.
function syncThen(promise, thenFunc) {
	// not a promise, or an already-resolved promise?
	if (!promise || !promise.then || promise.state() === 'resolved') {
		return $.when(thenFunc()); // resolve immediately
	}
	else if (thenFunc) {
		return promise.then(thenFunc);
	}
}