/*
* ----------------------------- 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.
*/

/**
* $.jStorage
*
* 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
*
* -storageAvailable()
* $.jStorage.storageAvailable() -> returns true if storage is available
*
* -reInit()
* $.jStorage.reInit() -> reloads the data from browser storage
*
* <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();
        },

        /* which backend is currently used */
        _backend = false,

        /* Next check for TTL */
        _ttl_timeout,

        /**
* 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 */
        var localStorageReallyWorks = false;
        if("localStorage" in window){
            try {
                window.localStorage.setItem('_tmptest', 'tmpval');
                localStorageReallyWorks = true;
                window.localStorage.removeItem('_tmptest');
            } catch(BogusQuotaExceededErrorOnIos5) {
                // Thanks be to iOS5 Private Browsing mode which throws
                // QUOTA_EXCEEDED_ERRROR DOM Exception 22.
            }
        }
        if(localStorageReallyWorks){
            try {
                if(window.localStorage) {
                    _storage_service = window.localStorage;
                    _backend = "localStorage";
                }
            } catch(E3) {/* Firefox fails when touching localStorage and cookies are disabled */}
        }
        /* Check if browser supports globalStorage */
        else if("globalStorage" in window){
            try {
                if(window.globalStorage) {
                    _storage_service = window.globalStorage[window.location.hostname];
                    _backend = "globalStorage";
                }
            } 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;
                _backend = "userDataBehavior";
            }else{
                _storage_elm = null;
                return;
            }
        }

        _load_storage();

        // remove dead keys
        _handleTTL();
    }

    /**
* Loads the data from the storage based on the supported mechanism
* @returns undefined
*/
    function _load_storage(){
        /* 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 || (typeof key != "string" && typeof key != "number")){
            throw new TypeError('Key name must be string or numeric');
        }
        if(key == "__jstorage_meta"){
            throw new TypeError('Reserved key name');
        }
        return true;
    }

    /**
* Removes expired keys
*/
    function _handleTTL(){
        var curtime, i, TTL, nextExpire = Infinity, changed = false;

        clearTimeout(_ttl_timeout);

        if(!_storage.__jstorage_meta || typeof _storage.__jstorage_meta.TTL != "object"){
            // nothing to do here
            return;
        }

        curtime = +new Date();
        TTL = _storage.__jstorage_meta.TTL;
        for(i in TTL){
            if(TTL.hasOwnProperty(i)){
                if(TTL[i] <= curtime){
                    delete TTL[i];
                    delete _storage[i];
                    changed = true;
                }else if(TTL[i] < nextExpire){
                    nextExpire = TTL[i];
                }
            }
        }

        // set next check
        if(nextExpire != Infinity){
            _ttl_timeout = setTimeout(_handleTTL, nextExpire - curtime);
        }

        // save changes
        if(changed){
            _save();
        }
    }

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

    $.jStorage = {
        /* Version number */
        version: "0.1.6.0",

        /**
* 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(_storage[key] && 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];
                // remove from TTL list
                if(_storage.__jstorage_meta &&
                  typeof _storage.__jstorage_meta.TTL == "object" &&
                  key in _storage.__jstorage_meta.TTL){
                    delete _storage.__jstorage_meta.TTL[key];
                }
                _save();
                return true;
            }
            return false;
        },

        /**
* Sets a TTL for a key, or remove it if ttl value is 0 or below
*
* @param {String} key - key to set the TTL for
* @param {Number} ttl - TTL timeout in milliseconds
* @returns true if key existed or false if it didn't
*/
        setTTL: function(key, ttl){
            var curtime = +new Date();
            _checkKey(key);
            ttl = Number(ttl) || 0;
            if(key in _storage){

                if(!_storage.__jstorage_meta){
                    _storage.__jstorage_meta = {};
                }
                if(!_storage.__jstorage_meta.TTL){
                    _storage.__jstorage_meta.TTL = {};
                }

                // Set TTL value for the key
                if(ttl>0){
                    _storage.__jstorage_meta.TTL[key] = curtime + ttl;
                }else{
                    delete _storage.__jstorage_meta.TTL[key];
                }

                _save();

                _handleTTL();
                return true;
            }
            return false;
        },

        /**
* Deletes everything in cache.
*
* @return true
*/
        flush: function(){
            _storage = {};
            _save();
            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) && i != "__jstorage_meta"){
                    index.push(i);
                }
            }
            return index;
        },

        /**
* How much space in bytes does the storage take?
*
* @returns Number
*/
        storageSize: function(){
            return _storage_size;
        },

        /**
* Which backend is currently in use?
*
* @returns String
*/
        currentBackend: function(){
            return _backend;
        },

        /**
* Test if storage is available
*
* @returns Boolean
*/
        storageAvailable: function(){
            return !!_backend;
        },

        /**
* Reloads the data from browser storage
*
* @returns undefined
*/
        reInit: function(){
            var new_storage_elm, data;
            if(_storage_elm && _storage_elm.addBehavior){
                new_storage_elm = document.createElement('link');

                _storage_elm.parentNode.replaceChild(new_storage_elm, _storage_elm);
                _storage_elm = new_storage_elm;

                /* 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");
                data = "{}";
                try{
                    data = _storage_elm.getAttribute("jStorage");
                }catch(E5){}
                _storage_service.jStorage = data;
                _backend = "userDataBehavior";
            }

            _load_storage();
        }
    };

    // Initialize jStorage
    _init();

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