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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.
*****************************************************************************/
define(
[],
function () {
/**
* The PersistenceQueue is used by the QueuingPersistenceCapability
* to aggregrate calls for object persistence. These are then issued
* in a group, such that if some or all are rejected, this result can
* be shown to the user (again, in a group.)
*
* This implementation is separate out from PersistenceQueue, which
* handles the wiring of injected dependencies into an instance of
* this class.
*
* @param $timeout Angular's $timeout
* @param {PersistenceQueueHandler} handler handles actual
* persistence when the queue is flushed
* @param {number} [DELAY] optional; delay in milliseconds between
* attempts to flush the queue
* @constructor
* @memberof platform/persistence/queue
*/
function PersistenceQueueImpl($q, $timeout, handler, delay) {
this.persistences = {};
this.objects = {};
this.lastObservedSize = 0;
this.activeDefer = $q.defer();
// If no delay is provided, use a default
this.delay = delay || 0;
this.handler = handler;
this.$timeout = $timeout;
this.$q = $q;
}
// Schedule a flushing of the queue (that is, plan to flush
// all objects in the queue)
PersistenceQueueImpl.prototype.scheduleFlush = function () {
var self = this,
$timeout = this.$timeout,
$q = this.$q,
handler = this.handler;
// Check if the queue's size has stopped increasing)
function quiescent() {
return Object.keys(self.persistences).length
=== self.lastObservedSize;
}
// Persist all queued objects
function flush() {
// Get a local reference to the active promise;
// this will be replaced with a promise for the next round
// of persistence calls, so we want to make sure we clear
// the correct one when this flush completes.
var flushingDefer = self.activeDefer;
// Clear the active promise for a queue flush
function clearFlushPromise(value) {
self.flushPromise = undefined;
flushingDefer.resolve(value);
return value;
}
// Persist all queued objects
self.flushPromise = handler.persist(
self.persistences,
self.objects,
self
).then(clearFlushPromise, clearFlushPromise);
// Reset queue, etc.
self.persistences = {};
self.objects = {};
self.lastObservedSize = 0;
self.pendingTimeout = undefined;
self.activeDefer = $q.defer();
}
function maybeFlush() {
// Timeout fired, so clear it
self.pendingTimeout = undefined;
// Only flush when we've stopped receiving updates
if (quiescent()) {
flush();
} else {
self.scheduleFlush();
}
// Update lastObservedSize to detect quiescence
self.lastObservedSize = Object.keys(self.persistences).length;
}
// If we are already flushing the queue...
if (self.flushPromise) {
// Wait until that's over before considering a flush
self.flushPromise.then(maybeFlush);
} else {
// Otherwise, schedule a flush on a timeout (to give
// a window for other updates to get aggregated)
self.pendingTimeout = self.pendingTimeout
|| $timeout(maybeFlush, self.delay, false);
}
return self.activeDefer.promise;
};
/**
* Queue persistence of a domain object.
* @param {DomainObject} domainObject the domain object
* @param {PersistenceCapability} persistence the object's
* undecorated persistence capability
* @returns {Promise} a promise which will resolve upon persistence
*/
PersistenceQueueImpl.prototype.put = function (domainObject, persistence) {
var id = domainObject.getId();
this.persistences[id] = persistence;
this.objects[id] = domainObject;
return this.scheduleFlush();
};
return PersistenceQueueImpl;
}
);
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