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/*****************************************************************************
* Open MCT, Copyright (c) 2014-2021, United States Government
* as represented by the Administrator of the National Aeronautics and Space
* Administration. All rights reserved.
*
* Open MCT is 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.
*
* Open MCT includes source code licensed under additional open source
* licenses. See the Open Source Licenses file (LICENSES.md) included with
* this source code distribution or the Licensing information page available
* at runtime from the About dialog for additional information.
*****************************************************************************/
/**
* Module defining MutationCapability. Created by vwoeltje on 11/12/14.
*/
define(
[],
function () {
var GENERAL_TOPIC = "mutation",
TOPIC_PREFIX = "mutation:";
// Utility function to overwrite a destination object
// with the contents of a source object.
function copyValues(destination, source) {
// First, remove all previously-existing keys
Object.keys(destination).forEach(function (k) {
delete destination[k];
});
// Second, write all new keys
Object.keys(source).forEach(function (k) {
destination[k] = source[k];
});
}
// Utility function to cast to a promise, without waiting
// for nextTick if a value is non-promise-like.
function fastPromise(value) {
return (value || {}).then ? value : {
then: function (callback) {
return fastPromise(callback(value));
}
};
}
/**
* The `mutation` capability allows a domain object's model to be
* modified. Wrapping such modifications in calls made through
* this capability allows these changes to be tracked (e.g. to
* ensure that a domain object's `modified` timestamp is kept
* up-to-date.)
*
* Usage:
*
* ```
* domainObject.useCapability("mutation", function (model) {
* // make changes to model here...
* });
* ```
*
* @param {Function} topic a service for creating listeners
* @param {Function} now a service to get the current time
* @param {DomainObject} domainObject the domain object
* which will expose this capability
* @memberof platform/core
* @constructor
* @implements {Capability}
*/
function MutationCapability(topic, now, domainObject) {
this.generalMutationTopic =
topic(GENERAL_TOPIC);
this.specificMutationTopic =
topic(TOPIC_PREFIX + domainObject.getId());
this.now = now;
this.domainObject = domainObject;
}
/**
* Modify the domain object's model, using a provided
* function. This function will receive a copy of the
* domain object's model as an argument; behavior
* varies depending on that function's return value:
*
* * If no value (or undefined) is returned by the mutator,
* the state of the model object delivered as the mutator's
* argument will become the domain object's new model.
* This is useful for writing code that modifies the model
* directly.
* * If a plain object is returned, that object will be used
* as the domain object's new model.
* * If boolean `false` is returned, the mutation will be
* cancelled.
* * If a promise is returned, its resolved value will be
* handled as one of the above.
*
*
* @param {Function} mutator the function which will make
* changes to the domain object's model.
* @param {number} [timestamp] timestamp to record for
* this mutation (otherwise, system time will be
* used)
* @returns {Promise.<boolean>} a promise for the result
* of the mutation; true if changes were made.
*/
MutationCapability.prototype.mutate = function (mutator, timestamp) {
// Get the object's model and clone it, so the
// mutator function has a temporary copy to work with.
var domainObject = this.domainObject,
now = this.now,
generalTopic = this.generalMutationTopic,
specificTopic = this.specificMutationTopic,
model = domainObject.getModel(),
clone = JSON.parse(JSON.stringify(model)),
useTimestamp = arguments.length > 1;
function notifyListeners(newModel) {
generalTopic.notify(domainObject);
specificTopic.notify(newModel);
}
// Function to handle copying values to the actual
function handleMutation(mutationResult) {
// If mutation result was undefined, just use
// the clone; this allows the mutator to omit return
// values and just change the model directly.
var result = mutationResult || clone;
// Allow mutators to change their mind by
// returning false.
if (mutationResult !== false) {
// Copy values if result was a different object
// (either our clone or some other new thing)
let modelHasChanged = _.isEqual(model, result) === false;
if (modelHasChanged) {
copyValues(model, result);
}
if (modelHasChanged
|| (useTimestamp !== undefined)
|| (model.modified === undefined)) {
model.modified = useTimestamp ? timestamp : now();
}
notifyListeners(model);
}
// Report the result of the mutation
return mutationResult !== false;
}
// Invoke the provided mutator, then make changes to
// the underlying model (if applicable.)
return fastPromise(mutator(clone)).then(handleMutation);
};
/**
* Listen for mutations of this domain object's model.
* The provided listener will be invoked with the domain
* object's new model after any changes. To stop listening,
* invoke the function returned by this method.
* @param {Function} listener function to call on mutation
* @returns {Function} a function to stop listening
* @memberof platform/core.MutationCapability#
*/
MutationCapability.prototype.listen = function (listener) {
return this.specificMutationTopic.listen(listener);
};
/**
* Alias of `mutate`, used to support useCapability.
*/
MutationCapability.prototype.invoke =
MutationCapability.prototype.mutate;
return MutationCapability;
}
);
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