96 lines
3.5 KiB
JavaScript
96 lines
3.5 KiB
JavaScript
/*****************************************************************************
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* Open MCT, Copyright (c) 2014-2017, United States Government
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* as represented by the Administrator of the National Aeronautics and Space
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* Administration. All rights reserved.
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*
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* Open MCT is licensed under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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* http://www.apache.org/licenses/LICENSE-2.0.
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*
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* Open MCT includes source code licensed under additional open source
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* licenses. See the Open Source Licenses file (LICENSES.md) included with
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* this source code distribution or the Licensing information page available
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* at runtime from the About dialog for additional information.
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*****************************************************************************/
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define(
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[],
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function () {
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var ERROR_PREFIX = "Error when notifying listener: ";
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/**
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* The `topic` service provides a way to create both named,
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* shared listeners and anonymous, private listeners.
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*
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* Usage:
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*
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* ```
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* var t = topic('foo'); // Use/create a named topic
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* t.listen(function () { ... });
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* t.notify({ some: "message" });
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* ```
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*
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* Named topics are shared; multiple calls to `topic`
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* with the same argument will return a single object instance.
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* Anonymous topics (where `topic` has been called with no
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* arguments) are private; each call returns a new instance.
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*
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* @returns {Function}
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* @memberof platform/core
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*/
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function Topic($log) {
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var topics = {};
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function createTopic() {
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var listeners = [];
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return {
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listen: function (listener) {
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listeners.push(listener);
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return function unlisten() {
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listeners = listeners.filter(function (l) {
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return l !== listener;
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});
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};
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},
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notify: function (message) {
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listeners.forEach(function (listener) {
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try {
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listener(message);
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} catch (e) {
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$log.error(ERROR_PREFIX + e.message);
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$log.error(e);
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}
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});
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}
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};
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}
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/**
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* Use and (if necessary) create a new topic.
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* @param {string} [key] name of the topic to use
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* @memberof platform/core.Topic#
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*/
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return function (key) {
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if (arguments.length < 1) {
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return createTopic();
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} else {
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topics[key] = topics[key] || createTopic();
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return topics[key];
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}
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};
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}
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return Topic;
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}
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);
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