/**
 * ----------------------------- JSTORAGE -------------------------------------
 * Simple local storage wrapper to save data on the browser side, supporting
 * all major browsers - IE6+, Firefox2+, Safari4+, Chrome4+ and Opera 10.5+
 *
 * Copyright (c) 2010 Andris Reinman, andris.reinman@gmail.com
 * Project homepage: www.jstorage.info
 *
 * Licensed under MIT-style license:
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

/**
 * USAGE:
 *
 * jStorage requires Prototype, MooTools or jQuery! If jQuery is used, then
 * jQuery-JSON (http://code.google.com/p/jquery-json/) is also needed.
 * (jQuery-JSON needs to be loaded BEFORE jStorage!)
 *
 * Methods:
 *
 * -set(key, value)
 * $.jStorage.set(key, value) -> saves a value
 *
 * -get(key[, default])
 * value = $.jStorage.get(key [, default]) ->
 *    retrieves value if key exists, or default if it doesn't
 *
 * -deleteKey(key)
 * $.jStorage.deleteKey(key) -> removes a key from the storage
 *
 * -flush()
 * $.jStorage.flush() -> clears the cache
 * 
 * -storageObj()
 * $.jStorage.storageObj() -> returns a read-ony copy of the actual storage
 * 
 * -storageSize()
 * $.jStorage.storageSize() -> returns the size of the storage in bytes
 *
 * -index()
 * $.jStorage.index() -> returns the used keys as an array
 * 
 * <value> can be any JSON-able value, including objects and arrays.
 *
 */

(function($){
	if(!$ || !($.toJSON || Object.toJSON || window.JSON)){
		throw new Error("jQuery, MooTools or Prototype needs to be loaded before jStorage!");
	}
	
	var
		/* This is the object, that holds the cached values */ 
		_storage = {},

		/* Actual browser storage (localStorage or globalStorage['domain']) */
		_storage_service = {jStorage:"{}"},

		/* DOM element for older IE versions, holds userData behavior */
		_storage_elm = null,
		
		/* How much space does the storage take */
		_storage_size = 0,

		/* function to encode objects to JSON strings */
		json_encode = $.toJSON || Object.toJSON || (window.JSON && (JSON.encode || JSON.stringify)),

		/* function to decode objects from JSON strings */
		json_decode = $.evalJSON || (window.JSON && (JSON.decode || JSON.parse)) || function(str){
			return String(str).evalJSON();
		},
		
		/**
		 * XML encoding and decoding as XML nodes can't be JSON'ized
		 * XML nodes are encoded and decoded if the node is the value to be saved
		 * but not if it's as a property of another object
		 * Eg. -
		 *   $.jStorage.set("key", xmlNode);        // IS OK
		 *   $.jStorage.set("key", {xml: xmlNode}); // NOT OK
		 */
		_XMLService = {
			
			/**
			 * Validates a XML node to be XML
			 * based on jQuery.isXML function
			 */
			isXML: function(elm){
				var documentElement = (elm ? elm.ownerDocument || elm : 0).documentElement;
				return documentElement ? documentElement.nodeName !== "HTML" : false;
			},
			
			/**
			 * Encodes a XML node to string
			 * based on http://www.mercurytide.co.uk/news/article/issues-when-working-ajax/
			 */
			encode: function(xmlNode) {
				if(!this.isXML(xmlNode)){
					return false;
				}
				try{ // Mozilla, Webkit, Opera
					return new XMLSerializer().serializeToString(xmlNode);
				}catch(E1) {
					try {  // IE
						return xmlNode.xml;
					}catch(E2){}
				}
				return false;
			},
			
			/**
			 * Decodes a XML node from string
			 * loosely based on http://outwestmedia.com/jquery-plugins/xmldom/
			 */
			decode: function(xmlString){
				var dom_parser = ("DOMParser" in window && (new DOMParser()).parseFromString) ||
						(window.ActiveXObject && function(_xmlString) {
					var xml_doc = new ActiveXObject('Microsoft.XMLDOM');
					xml_doc.async = 'false';
					xml_doc.loadXML(_xmlString);
					return xml_doc;
				}),
				resultXML;
				if(!dom_parser){
					return false;
				}
				resultXML = dom_parser.call("DOMParser" in window && (new DOMParser()) || window, xmlString, 'text/xml');
				return this.isXML(resultXML)?resultXML:false;
			}
		};

	////////////////////////// PRIVATE METHODS ////////////////////////

	/**
	 * Initialization function. Detects if the browser supports DOM Storage
	 * or userData behavior and behaves accordingly.
	 * @returns undefined
	 */
	function _init(){
		/* Check if browser supports localStorage */
		if("localStorage" in window){
			try {
				_storage_service = window.localStorage;
			} catch(E3) {/* Firefox fails when touching localStorage and cookies are disabled */}
		}
		/* Check if browser supports globalStorage */
		else if("globalStorage" in window){
			try {
				_storage_service = window.globalStorage[window.location.hostname];
			} catch(E4) {/* Firefox fails when touching localStorage and cookies are disabled */}
		}
		/* Check if browser supports userData behavior */
		else {
			_storage_elm = document.createElement('link');
			if(_storage_elm.addBehavior){

				/* Use a DOM element to act as userData storage */
				_storage_elm.style.behavior = 'url(#default#userData)';

				/* userData element needs to be inserted into the DOM! */
				document.getElementsByTagName('head')[0].appendChild(_storage_elm);

				_storage_elm.load("jStorage");
				var data = "{}";
				try{
					data = _storage_elm.getAttribute("jStorage");
				}catch(E5){}
				_storage_service.jStorage = data;
			}else{
				_storage_elm = null;
				return;
			}
		}

		/* if jStorage string is retrieved, then decode it */
		if(_storage_service.jStorage){
			try{
				_storage = json_decode(String(_storage_service.jStorage));
			}catch(E6){_storage_service.jStorage = "{}";}
		}else{
			_storage_service.jStorage = "{}";
		}
		_storage_size = _storage_service.jStorage?String(_storage_service.jStorage).length:0;
	}

	/**
	 * This functions provides the "save" mechanism to store the jStorage object
	 * @returns undefined
	 */
	function _save(){
		try{
			_storage_service.jStorage = json_encode(_storage);
			// If userData is used as the storage engine, additional
			if(_storage_elm) {
				_storage_elm.setAttribute("jStorage",_storage_service.jStorage);
				_storage_elm.save("jStorage");
			}
			_storage_size = _storage_service.jStorage?String(_storage_service.jStorage).length:0;
		}catch(E7){/* probably cache is full, nothing is saved this way*/}
	}

	/**
	 * Function checks if a key is set and is string or numberic
	 */
	function _checkKey(key){
		if((!key && key!==0) || (typeof key != "string" && typeof key != "number")){
			throw new TypeError('Key name must be string or numeric');
		}
		return true;
	}

	////////////////////////// PUBLIC INTERFACE /////////////////////////

	$.jStorage = {
		/* Version number */
		version: "0.1.4.1",

		/**
		 * Sets a key's value.
		 * 
		 * @param {String} key - Key to set. If this value is not set or not
		 *				a string an exception is raised.
		 * @param value - Value to set. This can be any value that is JSON
		 *				compatible (Numbers, Strings, Objects etc.).
		 * @returns the used value
		 */
		set: function(key, value){
			_checkKey(key);
			if(_XMLService.isXML(value)){
				value = {_is_xml:true,xml:_XMLService.encode(value)};
			}
			_storage[key] = value;
			_save();
			return value;
		},
		
		/**
		 * Looks up a key in cache
		 * 
		 * @param {String} key - Key to look up.
		 * @param {mixed} def - Default value to return, if key didn't exist.
		 * @returns the key value, default value or <null>
		 */
		get: function(key, def){
			_checkKey(key);
			if(key in _storage){
				if(typeof _storage[key] == "object" &&
						_storage[key]._is_xml &&
							_storage[key]._is_xml){
					return _XMLService.decode(_storage[key].xml);
				}else{
					return _storage[key];
				}
			}
			return typeof(def) == 'undefined' ? null : def;
		},
		
		/**
		 * Deletes a key from cache.
		 * 
		 * @param {String} key - Key to delete.
		 * @returns true if key existed or false if it didn't
		 */
		deleteKey: function(key){
			_checkKey(key);
			if(key in _storage){
				delete _storage[key];
				_save();
				return true;
			}
			return false;
		},

		/**
		 * Deletes everything in cache.
		 * 
		 * @returns true
		 */
		flush: function(){
			_storage = {};
			_save();
			/*
			 * Just to be sure - andris9/jStorage#3
			 */
			try{
				window.localStorage.clear();
			}catch(E8){}
			return true;
		},
		
		/**
		 * Returns a read-only copy of _storage
		 * 
		 * @returns Object
		*/
		storageObj: function(){
			function F() {}
			F.prototype = _storage;
			return new F();
		},
		
		/**
		 * Returns an index of all used keys as an array
		 * ['key1', 'key2',..'keyN']
		 * 
		 * @returns Array
		*/
		index: function(){
			var index = [], i;
			for(i in _storage){
				if(_storage.hasOwnProperty(i)){
					index.push(i);
				}
			}
			return index;
		},
		
		/**
		 * How much space in bytes does the storage take?
		 * 
		 * @returns Number
		 */
		storageSize: function(){
			return _storage_size;
		}
	};

	// Initialize jStorage
	_init();

})(window.jQuery || window.$);