// ---------------------------------------------------------------------------------------------
//	Javascript methods used to address basic DOM compatability issues in event handling and element selection
//	Version	Date			Reason
// 	0.1		Feb-2009		Initial version using Core.js from Simply Javascript by Kevin Yank and Cameron Adams
//	0.2		28-Feb-2009	Base.byId - a uniform getElementById to support W3C and older browsers, e.g. IE4, providing documents.all[element name]
//	0.3		29-Feb-2009	Base.byTag - a uniform getElementByTagName which also supports older browsers e.g. IE4 providing element.all.tags("tag name")
//	0.4		1-Mar-2009	Modify Base.addEventListener to support IE4 and IE5 Mac using DOM 0 event handlers
//	0.5		3-Mar-2009	Add browser detection algorithm, borrowed from Peter-Paul Koch at http://www.quirksmode.org/js/detect.html;
//						excluded Safari earlier than Safari 3 from using W3C event model, due to known bug with preventDefault 
// ---------------------------------------------------------------------------------------------

var Base = {};

// if (document.addEventListener && !Base.browser.oldSafari) { // W3C DOM 2 Events model
if (document.addEventListener) { // W3C DOM 2 Events model
// Development Note:  Safari 2.03 and earlier implementation of preventDefault is  non-functioning, which means that Safari < 2.0.4 will need to be excluded 
	Base.addEventListener = function (target, type, listener) {
		target.addEventListener(type, listener, false);
	}; // end Base.addEventListener method for W3C
	Base.removeEventListener = function (target, type, listener) {
		target.removeEventListener(type, listener, false);
	}; // end Base.removeEventListener method for W3C
	Base.preventDefault = function (event) {
		event.preventDefault();
	}; // end Base.preventDefault method for W3C
	Base.stopPropagation = function (event) {
		event.stopPropagation();
	}; // end Base.stopPropagation method for W3C

} else if (document.attachEvent) { // Internet Explorer Events model (IE 5+ Win)

	Base.addEventListener = function (target, type, listener) {
		// prevent adding the same listener twice, since DOM 2 Events ignores duplicates like this
		if (Base._findListener(target, type, listener) != -1) {
			return;
		}
		// listener2 calls listener as a method of target in one of two ways, depending on what this version of IE supports,
		// and passes it the global event object as an argument
		var listener2 = function () {
			var event = window.event;
			if (Function.prototype.call) { // IE 5.5 + supports call
				listener.call(target, event);
			} else { // IE 5.0 doesn't support call
				target._currentListener = listener;
				target._currentListener(event);
				target._currentListener = null;
			}
		};
		// following code allows complete removal of all listeners on unload - necessary due to notorious IE memory leak
		// add listener2 using IE's attachEvent method
		target.attachEvent("on" + type, listener2);
		// create an object describing this listener so we can clean it up later
		var listenerRecord = {
			target: target,
			type: type,
			listener: listener,
			listener2: listener2
		};
		// get a reference to the window object containing target
		var targetDocument = target.document || target;
		var targetWindow = targetDocument.parentWindow;
		// create a unique ID for this listener
		var listenerId = "l" + Base._listenerCounter++;
		// store a record of this listener in the window object
		if (!targetWindow._allListeners) {
			targetWindow._allListeners = {};
		}
		targetWindow._allListeners[listenerId] = listenerRecord;
	    // store this listener's ID in target
	    if (!target._listeners) {
			target._listeners = [];
		}
	    target._listeners[target._listeners.length] = listenerId;
		// set up Base._removeAllListeners to clean up all listeners on unload
	    if (!targetWindow._unloadListenerAdded) {
			targetWindow._unloadListenerAdded = true;
			targetWindow.attachEvent("onunload", Base._removeAllListeners);
		}
	}; // end Base.addEventListener method for IE 5+ Win

	Base.removeEventListener = function (target, type, listener) {
		// find out if the listener was actually added to target
		var listenerIndex = Base._findListener(target, type, listener);
		if (listenerIndex == -1) {
			return;
		}
		// get a reference to the window object containing target
		var targetDocument = target.document || target;
		var targetWindow = targetDocument.parentWindow;
		// obtain the record of the listener from the window object
		var listenerId = target._listeners[listenerIndex];
		var listenerRecord = targetWindow._allListeners[listenerId];
		// remove the listener, and remove its ID from target
		target.detachEvent("on" + type, listenerRecord.listener2);
		target._listeners.splice(listenerIndex, 1);
		// remove the record of the listener from the window object
		delete targetWindow._allListeners[listenerId];
	}; // end Base.removeEventListener method for IE 5+ Win

	Base.preventDefault = function (event) {
		event.returnValue = false;
	}; // end Base.preventDefault method for IE 5+ Win

	Base.stopPropagation = function (event) {
		event.cancelBubble = true;
	}; // end Base.stopPropagation method for IE 5+ Win

	Base._findListener = function (target, type, listener) {
		// get the array of listener IDs added to target
		var listeners = target._listeners;
		if (!listeners) {
			return -1;
		}
		// get a reference to the window object containing target
		var targetDocument = target.document || target;
		var targetWindow = targetDocument.parentWindow;
		// searching backward (to speed up onunload processing), find the listener
		for (var i = listeners.length - 1; i >= 0; i--) {
			// get the listener's ID from target
			var listenerId = listeners[i];
			// get the record of the listener from the window object
			var listenerRecord = targetWindow._allListeners[listenerId];
			// compare type and listener with the retrieved record
			if (listenerRecord.type == type && listenerRecord.listener == listener) {
				return i;
			}
		}
		return -1;
	}; // end Base._findListener private method for IE 5+ Win

	Base._removeAllListeners = function () {
		var targetWindow = this;
		for (id in targetWindow._allListeners) {
			var listenerRecord = targetWindow._allListeners[id];
			listenerRecord.target.detachEvent("on" + listenerRecord.type, listenerRecord.listener2);
			delete targetWindow._allListeners[id];
		}
	}; // end Base._removeAllListeners private method for IE 5+ Win

	Base._listenerCounter = 0;

} else { // old browsers - particularly IE4 and IE5Mac - which do not support W3C or IE event listeners, but do support DOM 0 event model

	Base.addEventListener = function (target, type, listener) {
		type = "on" + type;
		if (typeof target[type] == "function") {
			var oldListener = target[type];
			target[type] = function () {
				oldListener();
				return listener();
			};
		} else {
			target[type] = listener;
		}
	};  // end Base.addEventListener method for IE 4 Win
	Base.preventDefault = function (event) { //  DOM 0 supports cancelling the  default action only by returning false from the event handler
	};
	// Development Notes:
	// 1. No remove or detach event method, so any removal algorithm inevitably will be complicated
	// 2. stopPropagation ?
}

Base.addClass = function (target, theClass) {
	if (!Base.hasClass(target, theClass)) {
		if (target.className === "") {
			target.className = theClass;
		} else {
			target.className += " " + theClass;
		}
	}
}; // end Base.addClass method
Base.getElementsByClass = function (theClass) {
	var elementArray = [];
	if (typeof document.all != "undefined") {
		elementArray = document.all;
	} else {
		elementArray = document.getElementsByTagName("*");
	}
	var matchedArray = [];
	var pattern = new RegExp("(^| )" + theClass + "( |$)");
	for (var i = 0; i < elementArray.length; i++) {
		if (pattern.test(elementArray[i].className)) {
			matchedArray[matchedArray.length] = elementArray[i];
	    }
	}
	return matchedArray;
}; // end Base.getElementsByClass method
Base.hasClass = function (target, theClass) {
	var pattern = new RegExp("(^| )" + theClass + "( |$)");
	if (pattern.test(target.className)) {
		return true;
	}
	return false;
}; // end Base.hasClass method
Base.removeClass = function (target, theClass) {
	var pattern = new RegExp("(^| )" + theClass + "( |$)");
	target.className = target.className.replace(pattern, "$1");
	target.className = target.className.replace(/ $/, "");
}; // end Base.removeClass method
Base.getComputedStyle = function (element, styleProperty) {
	var computedStyle = null;
	if (typeof element.currentStyle != "undefined") {
		computedStyle = element.currentStyle;
	} else {
		computedStyle = document.defaultView.getComputedStyle(element, null);
	}
	return computedStyle[styleProperty];
}; // end Base.getComputedStyle method

Base.byId = function (element) {
	var elementId;
	if (typeof document.getElementById != "undefined") {
		elementId = document.getElementById(element);
	} else if (typeof document.all != "undefined") {
		elementId = document.all[element];
	}
	return elementId;
}; // end Base.byId method
Base.byTag = function (elementId, tag) {
// Development Note: this function still needs to be tested
	var element = Base.byId(elementId);
	if (typeof element.getElementByTagName != "undefined") {
		return element.getElementByTagName(tag);
	} else if (typeof element.all.tags != "undefined") {
		return element.all.tags("a");
	}
	return elementId;
}; // end Base.byTag method

String.prototype.trim = function () {
// enrich javascript's String object with a trim method which removes white space from the start and end of a string
	return this.replace(/^\s+|\s+$/g, "");
}; // end String.prototype.trim method

Base.start = function (runnable) {
	Base.addEventListener(window, "load", runnable.init);
}; // end Base.start method