var Http = {
 ReadyState: { Uninitialized: 0, Loading: 1, Loaded: 2, Interactive: 3, Complete: 4 },
 Status: { OK: 200, Created: 201, Accepted: 202, NoContent: 204, BadRequest: 400, Forbidden: 403, NotFound: 404, Gone: 410, ServerError: 500 },
 Cache: { Get: 1, GetCache: 2, GetNoCache: 3, FromCache: 4 },
 Method: { Get: "GET", Post: "POST", Put: "PUT", Delete: "DELETE" },
 enabled: false,
 logging: false,
 _get: null,
 _cache: new Object(),

 Init: function() {
  Http._get = Http._getXmlHttp();
  Http.enabled = (Http._get != null);
  Http.logging = (window.Logging != null);
 },

 _getXmlHttp: function() {

  /*@cc_on @*//*@if( @_jscript_version >= 5 )
                  try { return new ActiveXObject( "Msxml2.XMLHTTP" ); } catch( e ) { ; }
                  try { return new ActiveXObject( "Microsoft.XMLHTTP" ); } catch( e ) { ; }
  @end @*/

  try { return new XMLHttpRequest(); }
  catch( e ) { ; }
  return null;
 },

 get: function( params, callback_args ) {
  if( ! Http.enabled ) throw "Http: XmlHttpRequest not available.";
  var url = params.url;
  if( ! url ) throw "Http: A URL must be specified";
  var cache = params.cache || Http.Cache.Get;
  var method = params.method || Http.Method.Get;
  var callback = params.callback;
		
  if( ( cache == Http.Cache.FromCache ) || ( cache == Http.Cache.GetCache ) ) {
   var in_cache = Http.from_cache( url, callback, callback_args )
   if( Http.logging ) Logging.log( ["Http: URL in cache: " + in_cache] );
   if( in_cache || ( cache == Http.Cache.FromCache ) ) return in_cache;
  }

  if( cache == Http.Cache.GetNoCache ) {
   var sep = ( -1 < url.indexOf( "?" ) ) ? "&" : "?";	
   url = url + sep + "__=" + encodeURIComponent( ( new Date() ).getTime() );
  }

  if( ( Http._get.readyState != Http.ReadyState.Uninitialized ) && ( Http._get.readyState != Http.ReadyState.Complete ) ) {
   this._get.abort();
   if( Http.logging ) Logging.log(["Http: Aborted request in progress."]);
  }

  Http._get.open( method, url, true );

  Http._get.onreadystatechange = function() {
   if( Http._get.readyState != Http.ReadyState.Complete ) return;
   if( Http.logging ) Logging.log( ["Http: Returned, status: " + Http._get.status] );
   if( ( cache == Http.Cache.GetCache ) && ( Http._get.status == Http.Status.OK ) ) Http._cache[url] = Http._get.responseText;
   if( callback_args == null ) callback_args = new Array();
   var cb_params = new Array();
   cb_params.push( Http._get );

   for( var i = 0; i < callback_args.length; i++ )
    cb_params.push( callback_args[i] );

   callback.apply( null, cb_params );
  }

  if( Http.logging ) Logging.log( ["Http: Started\n\tURL: " + url + "\n\tMethod: " + method + "; Cache: " + Hash.keyName( Http.Cache, cache )] );
  Http._get.send( params.body || null );
 },

 from_cache: function( url, callback, callback_args ) {
  var result = Http._cache[url];

  if( result != null ) {
   var response = new Http.CachedResponse( result );
   var cb_params = new Array();
   cb_params.push( response );

   for( var i = 0; i < callback_args.length; i++ )
    cb_params.push( callback_args[i] );

   callback.apply( null, cb_params );
   return true;
  }
  else
   return false;
 },

 clear_cache: function() {
  Http._cache = new Object();
 },

 is_cached: function( url ) {
  return Http._cache[url] != null;
 },

 CachedResponse: function( response ) {
  this.readyState = Http.ReadyState.Complete;
  this.status = Http.Status.OK;
  this.responseText = response;
 }
}

Http.Init();

function json_response( response ) {
 var js = response.responseText;

 try { return eval( js ); }
 catch( e ) {
  if( Http.logging )
   Logging.logError( ["json_response: " + e] );
  else
   alert( "Error: " + e + "\n" + js );

  return null;
 }
}

function getResponseProps( response, header ) {
 try {
  var s = response.getResponseHeader( header || 'X-Ajax-Props' );

  if( ( s == null ) || ( s == "" ) )
   return new Object();
  else
   return eval( "o=" + s );
 }
 catch( e ) { return new Object(); }
}