gatsby-source-prismic/src/lib/getFromCache.ts

Gatsby source plugin for building websites using Prismic as a data source

import * as RTE from "fp-ts/ReaderTaskEither";
import { pipe } from "fp-ts/function";

import { Dependencies } from "../types";

/**
 * Returns a value from the environment's `cache` with the given key.
 *
 * @param key - Key used to get data from the cache.
 *
 * @returns Data from the cache with the given key, if available.
 */
export const getFromCache = <T>(
	key: string,
): RTE.ReaderTaskEither<Dependencies, Error, T> =>
	pipe(
		RTE.ask<Dependencies>(),
		RTE.chain((deps) => RTE.fromTask(() => deps.cache.get(key) as Promise<T>)),
		RTE.chainW(
			RTE.fromPredicate(
				(result) => result != null,
				() => new Error("Cache does not contain a value for the given key"),
			),
		),
	);