40 lines
1.3 KiB
TypeScript
40 lines
1.3 KiB
TypeScript
import { InputMessage, OutputMessage, Policy } from './types.ts';
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/** A policy function with opts to run it with. Used by the pipeline. */
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type PolicyTuple<P extends Policy = Policy> = [policy: P, opts?: InferPolicyOpts<P>];
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/** Infer opts from the policy. */
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type InferPolicyOpts<P> = P extends Policy<infer Opts> ? Opts : never;
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/** Helper type for proper type inference of PolicyTuples. */
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// https://stackoverflow.com/a/75806165
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// https://stackoverflow.com/a/54608401
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type Policies<T extends any[]> = {
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[K in keyof T]: PolicyTuple<T[K]> | Policy<T[K]>;
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};
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/** Processes messages through multiple policies, bailing early on rejection. */
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async function pipeline<T extends unknown[]>(msg: InputMessage, policies: [...Policies<T>]): Promise<OutputMessage> {
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for (const item of policies as (Policy | PolicyTuple)[]) {
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const [policy, opts] = toTuple(item);
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const result = await policy(msg, opts);
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if (result.action !== 'accept') {
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return result;
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}
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}
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return {
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id: msg.event.id,
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action: 'accept',
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msg: '',
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};
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}
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/** Coerce item into a tuple if it isn't already. */
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function toTuple<P extends Policy>(item: PolicyTuple<P> | P): PolicyTuple<P> {
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return typeof item === 'function' ? [item] : item;
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}
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export default pipeline;
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export type { PolicyTuple };
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