MacPro
57 lines
2.1 KiB
TypeScript
57 lines
2.1 KiB
TypeScript
import { Effects } from '../Effects';
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export declare abstract class Watchable<Raw, Mapped = Raw> {
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readonly effects: Effects;
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protected readonly mapFn: (value: Raw) => Mapped;
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protected readonly eqFn: (a: Mapped, b: Mapped) => boolean;
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constructor(effects: Effects, options?: {
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map?: (value: Raw) => Mapped;
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eq?: (a: Mapped, b: Mapped) => boolean;
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});
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/**
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* Fetch the current value, optionally registering a callback for change notification.
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* The callback should be invoked when the underlying data changes.
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*/
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protected abstract fetch(callback?: () => void): Promise<Raw>;
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protected abstract readonly label: string;
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/**
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* Produce a stream of raw values. Default implementation uses fetch() with
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* effects callback in a loop. Override for custom subscription mechanisms
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* (e.g. fs.watch).
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*/
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protected produce(abort: AbortSignal): AsyncGenerator<Raw, void>;
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/**
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* Lifecycle hook called when const() registers a subscription.
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* Return a cleanup function to be called when the subscription ends.
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* Override for side effects like FileHelper's consts tracking.
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*/
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protected onConstRegistered(_value: Mapped): (() => void) | void;
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/**
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* Internal generator that maps raw values and deduplicates using eq.
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*/
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private watchGen;
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/**
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* Returns the value. Reruns the context from which it has been called if the underlying value changes
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*/
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const(): Promise<Mapped>;
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/**
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* Returns the value. Does nothing if the value changes
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*/
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once(): Promise<Mapped>;
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/**
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* Watches the value. Returns an async iterator that yields whenever the value changes
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*/
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watch(abort?: AbortSignal): AsyncGenerator<Mapped, never, unknown>;
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/**
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* Watches the value. Takes a custom callback function to run whenever the value changes
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*/
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onChange(callback: (value: Mapped | undefined, error?: Error) => {
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cancel: boolean;
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} | Promise<{
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cancel: boolean;
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}>): void;
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/**
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* Watches the value. Returns when the predicate is true
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*/
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waitFor(pred: (value: Mapped) => boolean): Promise<Mapped>;
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}
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