one/dist/esm/background/useBackgroundComputation.mjs

One is a React framework for web, iOS, and Android apps.

import { useCallback, useLayoutEffect, useRef, useState } from "react";
import { createLatestComputation } from "./createLatestComputation.mjs";

function useBackgroundComputation(definition, input) {
	const [state, setState] = useState({
		phase: "idle",
		revision: 0
	});
	const owner = useRef(null);
	const submitted = useRef(null);
	const active = input !== null;
	useLayoutEffect(() => {
		if (!active) return;
		const computation = createLatestComputation(definition, (changed) => {
			setState(changed.phase === "ready" ? {
				phase: "ready",
				revision: changed.result.revision
			} : changed);
		});
		owner.current = computation;
		return () => {
			owner.current = null;
			submitted.current = null;
			computation.dispose();
		};
	}, [active, definition]);
	useLayoutEffect(() => {
		if (input === null) return;
		submitted.current = {
			input,
			factory: definition
		};
		owner.current?.update(input);
	}, [
		active,
		definition,
		input
	]);
	const getCurrent = useCallback(() => owner.current?.getCurrent() ?? null, []);
	const matches = active && submitted.current?.input === input && submitted.current.factory === definition;
	if (matches && state.phase === "failed") throw state.error;
	const current = owner.current?.getCurrent();
	const result = matches && state.phase === "ready" && current && state.revision === current.revision ? current : null;
	return {
		result,
		getCurrent
	};
}

export { useBackgroundComputation };
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