130 lines
4.9 KiB
JavaScript
130 lines
4.9 KiB
JavaScript
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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