JsonRpcRequestId = 1;

 JsonRpcTransaction = Class.create();

 Object.extend(JsonRpcTransaction.prototype,

 {

     initialize: function(serviceUrl, methodName, params, options) {

 	this.options = {

 	    debug: false,

 	    timeout: 0 /* milliseconds; zero means "do not specify" */

 	};

 	Object.extend(this.options, options || {});

 	this.serviceUrl = serviceUrl;

 	this.methodName = methodName;

 	this.params = params;

 	this.error = null;

 	this.reply = null;

 	this.replyReady = 0;

 	this.callbacks = [];

 	this.errorCallbacks = [];

 	this.sendRequest();

     },

     buildRequest: function() {

 	return { version: "1.1",

 		 id: JsonRpcRequestId++,

 		 method: this.methodName,

 		 params: this.params };

     },

     sendRequest: function() {

 	var headers = ['Content-type', 'application/json',

 		       'Accept', 'application/json'];

 	if (this.options.timeout) {

 	    headers.push('X-JSON-RPC-Timeout', this.options.timeout);

 	}

 	this.request =

 	    new Ajax.Request(this.serviceUrl,

 			     { method: 'post',

 			       requestHeaders: headers,

 			       postBody: JSON.stringify(this.buildRequest()),

 			       onComplete: this.receiveReply.bind(this) });

     },

     receiveReply: function(ajaxRequest) {

 	var response = JSON.parse(ajaxRequest.responseText);

 	if (response.error) {

 	    if (this.options.debug) {

 		alert("JsonRPC error:\n" +

 		      "Service: " + JSON.stringify(this.serviceUrl) + "\n" +

 		      "Method: " + JSON.stringify(this.methodName) + "\n" +

 		      "Params: " + JSON.stringify(this.params) + "\n" +

 		      "Response: " + JSON.stringify(response) + "\n");

 	    }

 	    this.error = response.error;

 	    this.errorCallbacks.each(function (cb) {

 					 try { cb(response.error, true); }

 					 catch (err) {}

 				     });

 	} else {

 	    var reply = response.result;

 	    this.reply = reply;

 	    this.replyReady = 1;

 	    this.callbacks.each(function (cb) {

 				    try { cb(reply, false); }

 				    catch (err) {}

 				});

 	}

     },

     addCallback: function(cb) {

 	this.callbacks.push(cb);

 	if (this.replyReady) {

 	    try { cb(this.reply, false); }

 	    catch (err) {}

 	}

 	return this;

     },

     addErrorCallback: function(cb) {

 	this.errorCallbacks.push(cb);

 	if (this.error) {

 	    try { cb(this.error, true); }

 	    catch (err) {}

 	}

 	return this;

     }

 });

 JsonRpcService = Class.create();

 Object.extend(JsonRpcService.prototype,

 {

     initialize: function(serviceUrl, onReady, options) {

 	this.options = {

 	    transactionClass: JsonRpcTransaction,

 	    timeout: 0, /* milliseconds; zero means "do not specify" */

 	    debug: false

 	};

 	Object.extend(this.options, options || {});

 	this.serviceUrl = serviceUrl;

 	var svc = this;

 	var txn = new (this.options.transactionClass)(serviceUrl,

 						      "system.describe",

 						      [],

 						      {debug: this.options.debug});

 	txn.addCallback(receiveServiceDescription);

 	function receiveServiceDescription(sd) {

 	    svc.serviceDescription = sd;

 	    svc.serviceDescription.procs.each(svc.installGenericProxy.bind(svc));

 	    onReady();

 	}

     },

     installGenericProxy: function(desc) {

 	this[desc.name] = function () {

 	    var actuals = $A(arguments);

 	    return new (this.options.transactionClass)(this.serviceUrl,

 						       desc.name,

 						       actuals,

 						       {

 							   debug: this.options.debug,

 							   timeout: this.options.timeout

 						       });

 	};

     }

 });