Solid.js cached resource tied to the navigation entry

solid-navigation-resource.ts

/// <reference types="navigation-api-types" />

import {
	type ResourceFetcher,
	type ResourceReturn,
	type ResourceSource,
	createResource,
	onCleanup,
} from 'solid-js';

export const createCachedResource = <T, S, R = unknown>(fetcher: ResourceFetcher<S, T, R>) => {
	const entries = new WeakMap<NavigationHistoryEntry, T>();

	const create = (source: ResourceSource<S>) => {
		const entry = navigation!.currentEntry!;
		const exists = entries.has(entry);

		const [resource, actions] = createResource(
			source,
			fetcher,
			exists ? { initialValue: entries.get(entry) } : {},
		);

		onCleanup(() => {
			const $state = resource.state;

			if ($state === 'ready' || $state === 'refreshing') {
				entries.set(entry, resource.latest);
			} else {
				entries.delete(entry);
			}
		});

		return [resource, actions] as ResourceReturn<T, R>;
	};

	return create;
};