30 lines
757 B
TypeScript
30 lines
757 B
TypeScript
import { merge, Observable } from "kefir";
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export const transform = <
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T,
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Mutations extends [Observable<any, any>, (prev: T, evt: any) => T][]
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>(
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initValue: T,
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...mutations: Mutations
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): Observable<T, unknown> =>
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merge(
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mutations.map(([source, mutation]) =>
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source.map((event) => ({ event, mutation }))
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)
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).scan((prev, { event, mutation }) => mutation(prev, event), initValue);
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export const partition =
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<C extends readonly [...string[]], T, E>(
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classes: C,
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partitionFn: (v: T) => C[number]
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) =>
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(obs: Observable<T, E>) => {
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const assigned = obs.map((obj) => ({ obj, cls: partitionFn(obj) }));
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return Object.fromEntries(
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classes.map((C) => [
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C,
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assigned.filter(({ cls }) => cls == C).map(({ obj }) => obj),
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])
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);
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};
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