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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 interface for asynchronous message-passing channels.
*
* This interface is useful for writing code in a message-passing style that's
* independent of the underlying communication medium. It's also useful for
* adding decorators that wrap message channels and add extra functionality on
* top. For example, {@link goog.messaging.BufferedChannel} enqueues messages
* until communication is established, while {@link goog.messaging.MultiChannel}
* splits a single underlying channel into multiple virtual ones.
*
* Decorators should be passed their underlying channel(s) in the constructor,
* and should assume that those channels are already connected. Decorators are
* responsible for disposing of the channels they wrap when the decorators
* themselves are disposed. Decorators should also follow the APIs of the
* individual methods listed below.
*
*/
goog.provide('goog.messaging.MessageChannel');
/**
* @interface
*/
goog.messaging.MessageChannel = function() {};
/**
* Initiates the channel connection. When this method is called, all the
* information needed to connect the channel has to be available.
*
* Implementers should only require this method to be called if the channel
* needs to be configured in some way between when it's created and when it
* becomes active. Otherwise, the channel should be immediately active and this
* method should do nothing but immediately call opt_connectCb.
*
* @param {Function=} opt_connectCb Called when the channel has been connected
* and is ready to use.
*/
goog.messaging.MessageChannel.prototype.connect = function(opt_connectCb) {};
/**
* Gets whether the channel is connected.
*
* If {@link #connect} is not required for this class, this should always return
* true. Otherwise, this should return true by the time the callback passed to
* {@link #connect} has been called and always after that.
*
* @return {boolean} Whether the channel is connected.
*/
goog.messaging.MessageChannel.prototype.isConnected = function() {};
/**
* Registers a service to be called when a message is received.
*
* Implementers shouldn't impose any restrictions on the service names that may
* be registered. If some services are needed as control codes,
* {@link goog.messaging.MultiMessageChannel} can be used to safely split the
* channel into "public" and "control" virtual channels.
*
* @param {string} serviceName The name of the service.
* @param {function((string|!Object))} callback The callback to process the
* incoming messages. Passed the payload. If opt_objectPayload is set, the
* payload is decoded and passed as an object.
* @param {boolean=} opt_objectPayload If true, incoming messages for this
* service are expected to contain an object, and will be deserialized from
* a string automatically if necessary. It's the responsibility of
* implementors of this class to perform the deserialization.
*/
goog.messaging.MessageChannel.prototype.registerService =
function(serviceName, callback, opt_objectPayload) {};
/**
* Registers a service to be called when a message is received that doesn't
* match any other services.
*
* @param {function(string, (string|!Object))} callback The callback to process
* the incoming messages. Passed the service name and the payload. Since
* some channels can pass objects natively, the payload may be either an
* object or a string.
*/
goog.messaging.MessageChannel.prototype.registerDefaultService =
function(callback) {};
/**
* Sends a message over the channel.
*
* @param {string} serviceName The name of the service this message should be
* delivered to.
* @param {string|!Object} payload The value of the message. If this is an
* Object, it is serialized to a string before sending if necessary. It's
* the responsibility of implementors of this class to perform the
* serialization.
*/
goog.messaging.MessageChannel.prototype.send =
function(serviceName, payload) {};
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