@lightbend/akkaserverless-javascript-sdk
Version:
Akka Serverless JavaScript SDK
107 lines • 3.83 kB
JavaScript
;
/*
* Copyright 2021 Lightbend Inc.
*
* 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.
*/
const util = require('util');
const Long = require('long');
/**
* @classdesc A Replicated Counter data type.
*
* A counter that can be incremented and decremented.
*
* The value is stored as a 64-bit signed long, hence values over `2^63 - 1` and less than `2^63` can't be represented.
*
* @constructor module:akkaserverless.replicatedentity.ReplicatedCounter
* @implements module:akkaserverless.replicatedentity.ReplicatedData
*/
function ReplicatedCounter() {
let currentValue = Long.ZERO;
let delta = Long.ZERO;
/**
* The value as a long.
*
* @name module:akkaserverless.replicatedentity.ReplicatedCounter#longValue
* @type {Long}
* @readonly
*/
Object.defineProperty(this, 'longValue', {
get: function () {
return currentValue;
},
});
/**
* The value as a number. Note that once the value exceeds `2^53`, this will not be an accurate
* representation of the value. If you expect it to exceed `2^53`, {@link module:akkaserverless.replicatedentity.ReplicatedCounter#longValue}
* should be used instead.
*
* @name module:akkaserverless.replicatedentity.ReplicatedCounter#value
* @type {number}
* @readonly
*/
Object.defineProperty(this, 'value', {
get: function () {
return currentValue.toNumber();
},
});
/**
* Increment the counter by the given number.
*
* @function module:akkaserverless.replicatedentity.ReplicatedCounter#increment
* @param {Long|number} increment The amount to increment the counter by. If negative, it will be decremented instead.
* @returns {module:akkaserverless.replicatedentity.ReplicatedCounter} This counter.
*/
this.increment = function (increment) {
currentValue = currentValue.add(increment);
delta = delta.add(increment);
return this;
};
/**
* Decrement the counter by the given number.
*
* @function module:akkaserverless.replicatedentity.ReplicatedCounter#decrement
* @param {Long|number} decrement The amount to decrement the counter by. If negative, it will be incremented instead.
* @returns {module:akkaserverless.replicatedentity.ReplicatedCounter} This counter.
*/
this.decrement = function (decrement) {
currentValue = currentValue.subtract(decrement);
delta = delta.subtract(decrement);
return this;
};
this.getAndResetDelta = function (initial) {
if (!delta.isZero() || initial) {
const currentDelta = {
counter: {
change: delta,
},
};
delta = Long.ZERO;
return currentDelta;
}
else {
return null;
}
};
this.applyDelta = function (delta) {
if (!delta.counter) {
throw new Error(util.format('Cannot apply delta %o to ReplicatedCounter', delta));
}
currentValue = currentValue.add(delta.counter.change);
};
this.toString = function () {
return 'ReplicatedCounter(' + currentValue + ')';
};
}
module.exports = ReplicatedCounter;
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