alexion
6081e3e325
Imported as a linear vendor commit so forge rebases do not replay the upstream root tree. git-subtree-dir: third_party/pi git-subtree-split: 71023aec1546d6d677a65669c5665c0927ce0dd0
39 lines
1.7 KiB
TypeScript
39 lines
1.7 KiB
TypeScript
import type { Ctx } from "./types.ts";
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// What a factory declares through `self` besides state cells: the shapes of resources and listeners.
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export interface Subscribable<E> {
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subscribe(listener: (event: E) => void): () => void;
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}
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/** `self.resource(name, declaration)`: something the object opens and later closes (a database, a watch, a socket). */
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export interface ResourceDeclaration<T> {
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/** Bump to replace the resource at the next reload (a native value has no schema to detect a change). */
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readonly version: number;
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/** References or resources that must be live/open first. A change replaces the resource. */
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readonly deps?: readonly unknown[];
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/** Exclusive resources are replaced at the gate: old closed before new opened. */
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readonly exclusive?: boolean;
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open(options: { readonly signal: AbortSignal }): T | Promise<T>;
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close?(value: T): void | Promise<void>;
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}
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export interface Resource<T> {
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readonly key: string;
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/** Throws not_ready until opened. */
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readonly value: T;
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}
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/** A listener as `self.on` declares it. */
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export interface ListenerDecl {
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readonly source: unknown;
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readonly select: ((value: never) => Subscribable<unknown>) | undefined;
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readonly fn: (event: unknown, ctx: Ctx) => void | Promise<void>;
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}
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// A cell has a `key` and a `value` too: sources are matched before resources.
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/** What `self.on(name, source, …)` passes to `select`: a resource's opened value, or the source itself. */
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export type ValueOf<S> = S extends Subscribable<unknown> ? S : S extends Resource<infer T> ? T : S;
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/** What `self.on(name, source, handler)` delivers: a readable's values, an event source's events. */
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export type EventOf<S> = S extends Subscribable<infer E> ? E : S extends Resource<infer T> ? EventOf<T> : never;
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