/**
 * Copyright 2009 by David Kerkeslager
 * Released under the BSD License (http://davidkerkeslager.com/license.txt).
 *
 * This library defines an object-literal which allows one to store key/value pairs after the hash (#) in the URI.
 * The syntax of the storage is modeled after the way that GET variables are stored after the question mark (?) in
 * the URI.
 *
 * Example URI: "http://www.foo.com/index.html#foo=bar&baz=quux"
 *
 * Note: it should be obvious that this should not be used for storing private data of any kind.
 */

var URIHash =
{
        /**
         * Dump the contents of the URI hash into an associative array. If the hash is invalid, the method returns
         * undefined.
         */
        dump : function()
        {
                var hash = document.location.hash;
                var dump = new Array();

                if(hash.length == 0) return dump;

                hash = hash.substring(1).split('&');

                for(var key in hash)
                {
                        var pair = hash[key].split('=');

                        if(pair.length != 2 || pair[0] in dump)
                                return undefined;

                        // escape for storage
                        dump[unescape(pair[0])] = unescape(pair[1]);
                }

                return dump;
        },

        /**
         * Takes an associative array and stores it in the URI as a hash after the # prefix, replacing any pre-
         * existing hash.
         */
        load : function(array)
        {
                var first = true;
                var hash = '';

                for(var key in array)
                {
                        if(!first) hash += '&';
                        first = false;
                        hash += escape(key) + '=' + escape(array[key]);
                }

                document.location.hash = hash;
        },
        

        /**
         * Get the value of a key from the hash.  If the hash does not contain the key or the hash is invalid,
         * the function returns undefined.
         */
        get : function(key)
        {
                return this.dump()[key];
        },

        /**
         * Set the value of a key in the hash.  If the key does not exist, the key/value pair is added.
         */
        set : function(key,value)
        {
                var dump = this.dump();
                dump[key] = value;

                var hash = new Array();

                for(var key in dump)
                        hash.push(escape(key) + '=' + escape(dump[key]));

                document.location.hash = hash.join('&');
        }
}