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130 lines
4.9 KiB
130 lines
4.9 KiB
import { root } from '../util/root'; |
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import { Action } from './Action'; |
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/** |
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* We need this JSDoc comment for affecting ESDoc. |
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* @ignore |
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* @extends {Ignored} |
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*/ |
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export class AsyncAction extends Action { |
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constructor(scheduler, work) { |
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super(scheduler, work); |
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this.scheduler = scheduler; |
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this.pending = false; |
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this.work = work; |
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} |
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schedule(state, delay = 0) { |
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if (this.closed) { |
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return this; |
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} |
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// Always replace the current state with the new state. |
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this.state = state; |
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// Set the pending flag indicating that this action has been scheduled, or |
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// has recursively rescheduled itself. |
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this.pending = true; |
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const id = this.id; |
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const scheduler = this.scheduler; |
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// |
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// Important implementation note: |
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// |
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// Actions only execute once by default, unless rescheduled from within the |
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// scheduled callback. This allows us to implement single and repeat |
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// actions via the same code path, without adding API surface area, as well |
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// as mimic traditional recursion but across asynchronous boundaries. |
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// |
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// However, JS runtimes and timers distinguish between intervals achieved by |
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// serial `setTimeout` calls vs. a single `setInterval` call. An interval of |
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// serial `setTimeout` calls can be individually delayed, which delays |
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// scheduling the next `setTimeout`, and so on. `setInterval` attempts to |
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// guarantee the interval callback will be invoked more precisely to the |
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// interval period, regardless of load. |
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// |
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// Therefore, we use `setInterval` to schedule single and repeat actions. |
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// If the action reschedules itself with the same delay, the interval is not |
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// canceled. If the action doesn't reschedule, or reschedules with a |
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// different delay, the interval will be canceled after scheduled callback |
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// execution. |
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// |
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if (id != null) { |
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this.id = this.recycleAsyncId(scheduler, id, delay); |
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} |
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this.delay = delay; |
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// If this action has already an async Id, don't request a new one. |
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this.id = this.id || this.requestAsyncId(scheduler, this.id, delay); |
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return this; |
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} |
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requestAsyncId(scheduler, id, delay = 0) { |
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return root.setInterval(scheduler.flush.bind(scheduler, this), delay); |
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} |
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recycleAsyncId(scheduler, id, delay = 0) { |
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// If this action is rescheduled with the same delay time, don't clear the interval id. |
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if (delay !== null && this.delay === delay && this.pending === false) { |
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return id; |
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} |
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// Otherwise, if the action's delay time is different from the current delay, |
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// or the action has been rescheduled before it's executed, clear the interval id |
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return root.clearInterval(id) && undefined || undefined; |
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} |
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/** |
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* Immediately executes this action and the `work` it contains. |
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* @return {any} |
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*/ |
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execute(state, delay) { |
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if (this.closed) { |
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return new Error('executing a cancelled action'); |
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} |
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this.pending = false; |
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const error = this._execute(state, delay); |
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if (error) { |
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return error; |
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} |
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else if (this.pending === false && this.id != null) { |
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// Dequeue if the action didn't reschedule itself. Don't call |
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// unsubscribe(), because the action could reschedule later. |
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// For example: |
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// ``` |
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// scheduler.schedule(function doWork(counter) { |
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// /* ... I'm a busy worker bee ... */ |
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// var originalAction = this; |
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// /* wait 100ms before rescheduling the action */ |
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// setTimeout(function () { |
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// originalAction.schedule(counter + 1); |
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// }, 100); |
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// }, 1000); |
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// ``` |
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this.id = this.recycleAsyncId(this.scheduler, this.id, null); |
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} |
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} |
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_execute(state, delay) { |
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let errored = false; |
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let errorValue = undefined; |
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try { |
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this.work(state); |
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} |
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catch (e) { |
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errored = true; |
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errorValue = !!e && e || new Error(e); |
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} |
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if (errored) { |
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this.unsubscribe(); |
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return errorValue; |
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} |
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} |
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/** @deprecated internal use only */ _unsubscribe() { |
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const id = this.id; |
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const scheduler = this.scheduler; |
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const actions = scheduler.actions; |
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const index = actions.indexOf(this); |
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this.work = null; |
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this.state = null; |
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this.pending = false; |
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this.scheduler = null; |
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if (index !== -1) { |
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actions.splice(index, 1); |
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} |
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if (id != null) { |
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this.id = this.recycleAsyncId(scheduler, id, null); |
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} |
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this.delay = null; |
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} |
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} |
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//# sourceMappingURL=AsyncAction.js.map
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