window.dhtmlHistory = {
	isIE: false,
	isOpera: false,
	isSafari: false,
	isKonquerer: false,
	isGecko: false,
	isSupported: false,
	
	create: function(options) {
		
		var that = this;
		var UA = navigator.userAgent.toLowerCase();
		var platform = navigator.platform.toLowerCase();
		var vendor = navigator.vendor || "";
		if (vendor === "KDE") {
			this.isKonqueror = true;
			this.isSupported = false;
		} else if (typeof window.opera !== "undefined") {
			this.isOpera = true;
			this.isSupported = true;
		} else if (typeof document.all !== "undefined") {
			this.isIE = true;
			this.isSupported = true;
		} else if (vendor.indexOf("Apple Computer, Inc.") > -1) {
			this.isSafari = true;
			this.isSupported = (platform.indexOf("mac") > -1);
		} else if (UA.indexOf("gecko") != -1) {
			this.isGecko = true;
			this.isSupported = true;
		}
		window.historyStorage.setup(options);

		if (this.isSafari) {
			this.createSafari();
		} else if (this.isOpera) {
			this.createOpera();
		}
		
		var initialHash = this.getCurrentLocation();

		this.currentLocation = initialHash;

		if (this.isIE) {
			this.createIE(initialHash);
		}

		var unloadHandler = function() {
			that.firstLoad = null;
		};
		
		this.addEventListener(window,'unload',unloadHandler);		

		if (this.isIE) {
			this.ignoreLocationChange = true;
		} else {
			if (!historyStorage.hasKey(this.PAGELOADEDSTRING)) {
				this.ignoreLocationChange = true;
				this.firstLoad = true;
				historyStorage.put(this.PAGELOADEDSTRING, true);
			} else {
				this.ignoreLocationChange = false;
				this.fireOnNewListener = true;
			}
		}

		var locationHandler = function() {
			that.checkLocation();
		};
		setInterval(locationHandler, 100);
	},	
	
	initialize: function() {
		if (this.isIE) {
			if (!historyStorage.hasKey(this.PAGELOADEDSTRING)) {
				this.fireOnNewListener = false;
				this.firstLoad = true;
				historyStorage.put(this.PAGELOADEDSTRING, true);
			}
			else {
				this.fireOnNewListener = true;
				this.firstLoad = false;   
			}
		}
	},

	addListener: function(listener) {
		this.listener = listener;
		if (this.fireOnNewListener) {
			this.fireHistoryEvent(this.currentLocation);
			this.fireOnNewListener = false;
		}
	},
	
	addEventListener: function(o,e,l) {
		if (o.addEventListener) {
			o.addEventListener(e,l,false);
		} else if (o.attachEvent) {
			o.attachEvent('on'+e,function() {
				l(window.event);
			});
		}
	},
	
	add: function(newLocation, historyData) {
		
		if (this.isSafari) {
			
			newLocation = this.removeHash(newLocation);
			historyStorage.put(newLocation, historyData);
			this.currentLocation = newLocation;
			window.location.hash = newLocation;
			this.putSafariState(newLocation);
		} else {
			var that = this;
			var addImpl = function() {
				if (that.currentWaitTime > 0) {
					that.currentWaitTime = that.currentWaitTime - that.waitTime;
				}
				newLocation = that.removeHash(newLocation);
				if (document.getElementById(newLocation) && that.debugMode) {
					var e = "Exception: History locations can not have the same value as _any_ IDs that might be in the document,"
					+ " due to a bug in IE; please ask the developer to choose a history location that does not match any HTML"
					+ " IDs in this document. The following ID is already taken and cannot be a location: " + newLocation;
					throw new Error(e); 
				}
				historyStorage.put(newLocation, historyData);
				that.ignoreLocationChange = true;
				that.ieAtomicLocationChange = true;
				that.currentLocation = newLocation;
				window.location.hash = newLocation;
				if (that.isIE) {
					that.iframe.src = "blank.html?" + newLocation;
				}
				that.ieAtomicLocationChange = false;
			};

			window.setTimeout(addImpl, this.currentWaitTime);
			this.currentWaitTime = this.currentWaitTime + this.waitTime;
		}
	},
	isFirstLoad: function() {
		return this.firstLoad;
	},
	getVersion: function() {
		return "0.6";
	},
	getCurrentLocation: function() {
		var r = (this.isSafari
			? this.getSafariState()
			: this.getCurrentHash()
		);
		return r;
	},
    getCurrentHash: function() {
		var r = window.location.href;
		var i = r.indexOf("#");
		return (i >= 0
			? r.substr(i+1)
			: ""
		);
    },
	PAGELOADEDSTRING: "DhtmlHistory_pageLoaded",
	listener: null,
	waitTime: 200,
	currentWaitTime: 0,
	currentLocation: null,
	iframe: null,
	safariHistoryStartPoint: null,
	safariStack: null,
	safariLength: null,

	ignoreLocationChange: null,
	fireOnNewListener: null,
	firstLoad: null,
	ieAtomicLocationChange: null,
	createIE: function(initialHash) {
		this.waitTime = 400;/*IE needs longer between history updates*/
		var styles = (historyStorage.debugMode
			? 'width: 800px;height:80px;border:1px solid black;'
			: historyStorage.hideStyles
		);
		var iframeID = "rshHistoryFrame";
		var iframeHTML = '<iframe frameborder="0" id="' + iframeID + '" style="' + styles + '" src="blank.html?' + initialHash + '"></iframe>';
		document.write(iframeHTML);
		this.iframe = document.getElementById(iframeID);
	},
	
	createOpera: function() {
		this.waitTime = 400;/*Opera needs longer between history updates*/
		var imgHTML = '<img src="javascript:location.href=\'javascript:dhtmlHistory.checkLocation();\';" style="' + historyStorage.hideStyles + '" />';
		document.write(imgHTML);
	},
	
	createSafari: function() {
		var formID = "rshSafariForm";
		var stackID = "rshSafariStack";
		var lengthID = "rshSafariLength";
		var formStyles = historyStorage.debugMode ? historyStorage.showStyles : historyStorage.hideStyles;
		var inputStyles = (historyStorage.debugMode
			? 'width:800px;height:20px;border:1px solid black;margin:0;padding:0;'
			: historyStorage.hideStyles
		);
		var safariHTML = '<form id="' + formID + '" style="' + formStyles + '">'
			+ '<input type="text" style="' + inputStyles + '" id="' + stackID + '" value="[]"/>'
			+ '<input type="text" style="' + inputStyles + '" id="' + lengthID + '" value=""/>'
		+ '</form>';
		document.write(safariHTML);
		this.safariStack = document.getElementById(stackID);
		this.safariLength = document.getElementById(lengthID);
		if (!historyStorage.hasKey(this.PAGELOADEDSTRING)) {
			this.safariHistoryStartPoint = history.length;
			this.safariLength.value = this.safariHistoryStartPoint;
		} else {
			this.safariHistoryStartPoint = this.safariLength.value;
		}
	},
	
	getSafariStack: function() {
		var r = this.safariStack.value;
		return historyStorage.fromJSON(r);
	},

	getSafariState: function() {
		var stack = this.getSafariStack();
		var state = stack[history.length - this.safariHistoryStartPoint - 1];
		return state;
	},			
	putSafariState: function(newLocation) {
	    var stack = this.getSafariStack();
	    stack[history.length - this.safariHistoryStartPoint] = newLocation;
	    this.safariStack.value = historyStorage.toJSON(stack);
	},

	fireHistoryEvent: function(newHash) {
		var historyData = historyStorage.get(newHash);
		this.listener.call(null, newHash, historyData);
	},
	
	checkLocation: function() {
		
		if (!this.isIE && this.ignoreLocationChange) {
			this.ignoreLocationChange = false;
			return;
		}

		if (!this.isIE && this.ieAtomicLocationChange) {
			return;
		}
		
		var hash = this.getCurrentLocation();

		if (hash == this.currentLocation) {
			return;
		}

		this.ieAtomicLocationChange = true;

		if (this.isIE && this.getIframeHash() != hash) {
			this.iframe.src = "blank.html?" + hash;
		}
		else if (this.isIE) {
			return;
		}

		this.currentLocation = hash;

		this.ieAtomicLocationChange = false;

		this.fireHistoryEvent(hash);
	},

	getIframeHash: function() {
		var doc = this.iframe.contentWindow.document;
		var hash = String(doc.location.search);
		if (hash.length == 1 && hash.charAt(0) == "?") {
			hash = "";
		}
		else if (hash.length >= 2 && hash.charAt(0) == "?") {
			hash = hash.substring(1);
		}
		return hash;
	},

	removeHash: function(hashValue) {
		var r;
		if (hashValue === null || hashValue === undefined) {
			r = null;
		}
		else if (hashValue === "") {
			r = "";
		}
		else if (hashValue.length == 1 && hashValue.charAt(0) == "#") {
			r = "";
		}
		else if (hashValue.length > 1 && hashValue.charAt(0) == "#") {
			r = hashValue.substring(1);
		}
		else {
			r = hashValue;
		}
		return r;
	},

	iframeLoaded: function(newLocation) {
		if (this.ignoreLocationChange) {
			this.ignoreLocationChange = false;
			return;
		}

		var hash = String(newLocation.search);
		if (hash.length == 1 && hash.charAt(0) == "?") {
			hash = "";
		}
		else if (hash.length >= 2 && hash.charAt(0) == "?") {
			hash = hash.substring(1);
		}
		/*Keep the browser location bar in sync with the iframe hash*/
		window.location.hash = hash;

		/*Notify listeners of the change*/
		this.fireHistoryEvent(hash);
	}

};

window.historyStorage = {
	
	setup: function(options) {
		if (typeof options !== "undefined") {
			if (options.debugMode) {
				this.debugMode = options.debugMode;
			}
			if (options.toJSON) {
				this.toJSON = options.toJSON;
			}
			if (options.fromJSON) {
				this.fromJSON = options.fromJSON;
			}
		}		
		
		var formID = "rshStorageForm";
		var textareaID = "rshStorageField";
		var formStyles = this.debugMode ? historyStorage.showStyles : historyStorage.hideStyles;
		var textareaStyles = (historyStorage.debugMode
			? 'width: 800px;height:80px;border:1px solid black;'
			: historyStorage.hideStyles
		);
		var textareaHTML = '<form id="' + formID + '" style="' + formStyles + '">'
			+ '<textarea id="' + textareaID + '" style="' + textareaStyles + '"></textarea>'
		+ '</form>';
		document.write(textareaHTML);
		this.storageField = document.getElementById(textareaID);
		if (typeof window.opera !== "undefined") {
			this.storageField.focus();/*Opera needs to focus this element before persisting values in it*/
		}
	},
	
	put: function(key, value) {
		this.assertValidKey(key);
		if (this.hasKey(key)) {
			this.remove(key);
		}
		this.storageHash[key] = value;
		this.saveHashTable();
	},

	/*Public*/
	get: function(key) {
		this.assertValidKey(key);
		/*make sure the hash table has been loaded from the form*/
		this.loadHashTable();
		var value = this.storageHash[key];
		if (value === undefined) {
			value = null;
		}
		return value;
	},

	/*Public*/
	remove: function(key) {
		this.assertValidKey(key);
		/*make sure the hash table has been loaded from the form*/
		this.loadHashTable();
		/*delete the value*/
		delete this.storageHash[key];
		/*serialize and save the hash table into the form*/
		this.saveHashTable();
	},

	/*Public: Clears out all saved data.*/
	reset: function() {
		this.storageField.value = "";
		this.storageHash = {};
	},

	/*Public*/
	hasKey: function(key) {
		this.assertValidKey(key);
		/*make sure the hash table has been loaded from the form*/
		this.loadHashTable();
		return (typeof this.storageHash[key] !== "undefined");
	},

	/*Public*/
	isValidKey: function(key) {
		return (typeof key === "string");
	},
	
	/*Public - CSS strings utilized by both objects to hide or show behind-the-scenes DOM elements*/
	showStyles: 'border:0;margin:0;padding:0;',
	hideStyles: 'left:-1000px;top:-1000px;width:1px;height:1px;border:0;position:absolute;',
	
	/*Public - debug mode flag*/
	debugMode: false,
	
	/*- - - - - - - - - - - -*/

	/*Private: Our hash of key name/values.*/
	storageHash: {},

	/*Private: If true, we have loaded our hash table out of the storage form.*/
	hashLoaded: false, 

	/*Private: DOM reference to our history field*/
	storageField: null,

	/*Private: Assert that a key is valid; throw an exception if it not.*/
	assertValidKey: function(key) {
		var isValid = this.isValidKey(key);
		if (!isValid && this.debugMode) {
			throw new Error("Please provide a valid key for window.historyStorage. Invalid key = " + key + ".");
		}
	},

	/*Private: Load the hash table up from the form.*/
	loadHashTable: function() {
		if (!this.hashLoaded) {	
			var serializedHashTable = this.storageField.value;
			if (serializedHashTable !== "" && serializedHashTable !== null) {
				this.storageHash = this.fromJSON(serializedHashTable);
				this.hashLoaded = true;
			}
		}
	},
	/*Private: Save the hash table into the form.*/
	saveHashTable: function() {
		this.loadHashTable();
		var serializedHashTable = this.toJSON(this.storageHash);
		this.storageField.value = serializedHashTable;
	},
	/*Private: Bridges for our JSON implementations - both rely on 2007 JSON.org library - can be overridden by options bundle*/
	toJSON: function(o) {
		return o.toJSONString();
	},
	fromJSON: function(s) {
		return s.parseJSON();
	}
};