;(function ($, window) {

var intervals = {};
var removeListener = function(selector) {

	if (intervals[selector]) {

		window.clearInterval(intervals[selector]);
		intervals[selector] = null;
	}
};
var found = 'waitUntilExists.found';

/**
 * @function
 * @property {object} jQuery plugin which runs handler function once specified
 *           element is inserted into the DOM
 * @param {function|string} handler
 *            A function to execute at the time when the element is inserted or
 *            string "remove" to remove the listener from the given selector
 * @param {bool} shouldRunHandlerOnce
 *            Optional: if true, handler is unbound after its first invocation
 * @example jQuery(selector).waitUntilExists(function);
 */

$.fn.waitUntilExists = function(handler, shouldRunHandlerOnce, isChild) {

	var selector = this.selector;
	var $this = $(selector);
	var $elements = $this.not(function() { return $(this).data(found); });

	if (handler === 'remove') {

		// Hijack and remove interval immediately if the code requests
		removeListener(selector);
	}
	else {

		// Run the handler on all found elements and mark as found
		$elements.each(handler).data(found, true);

		if (shouldRunHandlerOnce && $this.length) {

			// Element was found, implying the handler already ran for all
			// matched elements
			removeListener(selector);
		}
		else if (!isChild) {

			// If this is a recurring search or if the target has not yet been
			// found, create an interval to continue searching for the target
			intervals[selector] = window.setInterval(function () {

				$this.waitUntilExists(handler, shouldRunHandlerOnce, true);
			}, 500);
		}
	}

	return $this;
};

}(jQuery, window));