gatsby-source-prismic/src/lib/getFromOrSetToCache.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";

import { getFromCache } from "./getFromCache";
import { setToCache } from "./setToCache";

/**
 * Get value from the cache using a given key. If a value for the given key does
 * not exist, set it with a given value.
 *
 * @param key - Key used to get data from the cache.
 * @param f - Function to compute the cached value if a value does not already exist.
 *
 * @returns Data from the cache with the given key.
 */
export const getFromOrSetToCache = <T>(
	key: string,
	f: RTE.ReaderTaskEither<Dependencies, Error, T>,
): RTE.ReaderTaskEither<Dependencies, Error, T> =>
	pipe(
		RTE.ask<Dependencies>(),
		RTE.chain(() => getFromCache<T>(key)),
		RTE.orElse(() => pipe(f, RTE.chainFirstW(setToCache(key)))),
	);