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// Copyright 2010 The Closure Library Authors. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS-IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
/**
* @fileoverview An abstract superclass for message channels that handles the
* repetitive details of registering and dispatching to services. This is more
* useful for full-fledged channels than for decorators, since decorators
* generally delegate service registering anyway.
*
*/
goog.provide('goog.messaging.AbstractChannel');
goog.require('goog.Disposable');
goog.require('goog.debug');
goog.require('goog.debug.Logger');
goog.require('goog.json');
goog.require('goog.messaging.MessageChannel'); // interface
/**
* Creates an abstract message channel.
*
* @constructor
* @extends {goog.Disposable}
* @implements {goog.messaging.MessageChannel}
*/
goog.messaging.AbstractChannel = function() {
goog.base(this);
/**
* The services registered for this channel.
* @type {Object.<string, {callback: function((string|!Object)),
objectPayload: boolean}>}
* @private
*/
this.services_ = {};
};
goog.inherits(goog.messaging.AbstractChannel, goog.Disposable);
/**
* The default service to be run when no other services match.
*
* @type {?function(string, (string|!Object))}
* @private
*/
goog.messaging.AbstractChannel.prototype.defaultService_;
/**
* Logger for this class.
* @type {goog.debug.Logger}
* @protected
*/
goog.messaging.AbstractChannel.prototype.logger =
goog.debug.Logger.getLogger('goog.messaging.AbstractChannel');
/**
* Immediately calls opt_connectCb if given, and is otherwise a no-op. If
* subclasses have configuration that needs to happen before the channel is
* connected, they should override this and {@link #isConnected}.
* @override
*/
goog.messaging.AbstractChannel.prototype.connect = function(opt_connectCb) {
if (opt_connectCb) {
opt_connectCb();
}
};
/**
* Always returns true. If subclasses have configuration that needs to happen
* before the channel is connected, they should override this and
* {@link #connect}.
* @override
*/
goog.messaging.AbstractChannel.prototype.isConnected = function() {
return true;
};
/** @override */
goog.messaging.AbstractChannel.prototype.registerService =
function(serviceName, callback, opt_objectPayload) {
this.services_[serviceName] = {
callback: callback,
objectPayload: !!opt_objectPayload
};
};
/** @override */
goog.messaging.AbstractChannel.prototype.registerDefaultService =
function(callback) {
this.defaultService_ = callback;
};
/** @override */
goog.messaging.AbstractChannel.prototype.send = goog.abstractMethod;
/**
* Delivers a message to the appropriate service. This is meant to be called by
* subclasses when they receive messages.
*
* This method takes into account both explicitly-registered and default
* services, as well as making sure that JSON payloads are decoded when
* necessary. If the subclass is capable of passing objects as payloads, those
* objects can be passed in to this method directly. Otherwise, the (potentially
* JSON-encoded) strings should be passed in.
*
* @param {string} serviceName The name of the service receiving the message.
* @param {string|!Object} payload The contents of the message.
* @protected
*/
goog.messaging.AbstractChannel.prototype.deliver = function(
serviceName, payload) {
var service = this.getService(serviceName, payload);
if (!service) {
return;
}
var decodedPayload =
this.decodePayload(serviceName, payload, service.objectPayload);
if (goog.isDefAndNotNull(decodedPayload)) {
service.callback(decodedPayload);
}
};
/**
* Find the service object for a given service name. If there's no service
* explicitly registered, but there is a default service, a service object is
* constructed for it.
*
* @param {string} serviceName The name of the service receiving the message.
* @param {string|!Object} payload The contents of the message.
* @return {?{callback: function((string|!Object)), objectPayload: boolean}} The
* service object for the given service, or null if none was found.
* @protected
*/
goog.messaging.AbstractChannel.prototype.getService = function(
serviceName, payload) {
var service = this.services_[serviceName];
if (service) {
return service;
} else if (this.defaultService_) {
var callback = goog.partial(this.defaultService_, serviceName);
var objectPayload = goog.isObject(payload);
return {callback: callback, objectPayload: objectPayload};
}
this.logger.warning('Unknown service name "' + serviceName + '"');
return null;
};
/**
* Converts the message payload into the format expected by the registered
* service (either JSON or string).
*
* @param {string} serviceName The name of the service receiving the message.
* @param {string|!Object} payload The contents of the message.
* @param {boolean} objectPayload Whether the service expects an object or a
* plain string.
* @return {string|Object} The payload in the format expected by the service, or
* null if something went wrong.
* @protected
*/
goog.messaging.AbstractChannel.prototype.decodePayload = function(
serviceName, payload, objectPayload) {
if (objectPayload && goog.isString(payload)) {
try {
return goog.json.parse(payload);
} catch (err) {
this.logger.warning('Expected JSON payload for ' + serviceName +
', was "' + payload + '"');
return null;
}
} else if (!objectPayload && !goog.isString(payload)) {
return goog.json.serialize(payload);
}
return payload;
};
/** @override */
goog.messaging.AbstractChannel.prototype.disposeInternal = function() {
goog.base(this, 'disposeInternal');
goog.dispose(this.logger);
delete this.logger;
delete this.services_;
delete this.defaultService_;
};
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