82 lines
1.7 KiB
TypeScript
82 lines
1.7 KiB
TypeScript
import { ReactiveController, ReactiveControllerHost } from 'lit';
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export class CachedValueController<T> implements ReactiveController {
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protected _value?: T;
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protected _host: ReactiveControllerHost;
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protected _timerSeconds: number;
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protected _callback: () => T;
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protected _timerID?: number;
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constructor(host: ReactiveControllerHost, timerSeconds: number, callback: () => T) {
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this._timerSeconds = timerSeconds;
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this._callback = callback;
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(this._host = host).addController(this);
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}
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/**
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* Remove the controller for the host.
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*/
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public removeController(): void {
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this._host.removeController(this);
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}
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/**
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* Get the value.
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*/
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get value(): T | undefined {
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return this._value;
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}
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/**
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* Update the cached value (and reset the timer).
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*/
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public updateValue(): void {
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this._value = this._callback();
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this._startTimer();
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}
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/**
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* Clear the cached value.
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*/
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public clearValue(): void {
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this._value = undefined;
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this._stopTimer();
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}
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/**
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* Disable the timer.
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*/
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protected _stopTimer(): void {
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clearInterval(this._timerID);
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this._timerID = undefined;
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}
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/**
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* Enable the timer. Repeated calls will have no effect.
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*/
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protected _startTimer(): void {
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this._stopTimer();
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if (this._timerSeconds > 0) {
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this._timerID = window.setInterval(() => {
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this.updateValue();
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this._host.requestUpdate();
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}, this._timerSeconds * 1000);
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}
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}
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/**
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* Host has connected to the cache.
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*/
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hostConnected(): void {
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this.updateValue();
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this._host.requestUpdate();
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}
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/**
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* Host has disconnected from the cache.
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*/
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hostDisconnected(): void {
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this.clearValue();
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}
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}
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