QueryStringUtil

/*
    CASA Lib for ActionScript 3.0
    Copyright (c) 2011, Aaron Clinger & Contributors of CASA Lib
    All rights reserved.
    
    Redistribution and use in source and binary forms, with or without
    modification, are permitted provided that the following conditions are met:
    
    - Redistributions of source code must retain the above copyright notice,
      this list of conditions and the following disclaimer.
    
    - Redistributions in binary form must reproduce the above copyright notice,
      this list of conditions and the following disclaimer in the documentation
      and/or other materials provided with the distribution.
    
    - Neither the name of the CASA Lib nor the names of its contributors
      may be used to endorse or promote products derived from this software
      without specific prior written permission.
    
    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
    AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
    IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
    ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
    LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
    CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
    SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
    INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
    CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
    ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
    POSSIBILITY OF SUCH DAMAGE.
*/
package org.casalib.util {
    import flash.external.ExternalInterface;
    import flash.utils.Dictionary;
    
    
    /**
        Utility for providing easy access to the browser query string.
        
        @author Aaron Clinger
        @version 03/28/10
    */
    public class QueryStringUtil {
        protected static var _query:String;
        protected static var _hasRequested:Boolean;
        protected static var _pairMap:Dictionary;
        
        
        /**
            The field/value pairs of the browser URL.
        */
        public static function get queryString():String {
            if (!QueryStringUtil._hasRequested) {
                QueryStringUtil._hasRequested = true;
                
                if (ExternalInterface.available) {
                    try {
                        const query:String = ExternalInterface.call('document.location.search.toString');
                        
                        if (query != '' && query != null) {
                            QueryStringUtil._query = query.substring(1);
                            
                            const pairs:Array = QueryStringUtil._query.split('&');
                            var i:int         = -1;
                            var pair:Array;
                            
                            QueryStringUtil._pairMap = new Dictionary();
                            
                            while (++i < pairs.length) {
                                pair = pairs[i].split('=');
                                
                                QueryStringUtil._pairMap[pair[0]] = pair[1];
                            }
                        }
                    } catch (e:Error) {}
                }
            }
            
            return QueryStringUtil._query;
        }
        
        /**
            Returns a query string value by key.
            
            @param key: The key of the query string value to retrieve.
            @return The string value of the key.
        */
        public static function getValue(key:String):String {
            if (QueryStringUtil.queryString == null)
                return null;
            
            return QueryStringUtil._pairMap[key];
        }
        
        /**
            Checks to if query string key exists.
            
            @param key: The name of the key to check for existence.
            @return Returns true if the key exists; otherwise false.
        */
        public static function hasKey(key:String):Boolean {
            return QueryStringUtil.getValue(key) ? true : false;
        }
    }
}