tranzak-node/compat/lib/simple-cache.js

TRANZAK API client for Nodejs

"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.default = void 0;
/**
 * Copyright 2022 HolyCorn Software
 * This module (simple-cache) allows components to maintain a simple cache.
 * 
 * The cache works by defining a fetch function, and a timeout.
 * If the cache is querried when the data in it is older than the timeout, it fetches new data, stores it, and returns it. Subsequent fetches will return the
 * newly fetched data, till it's old enough to be obsolete
 */

const cacheData = Symbol();
const cacheDataLastRefresh = Symbol();
const fetchPromise = Symbol();

/**
 * @template Type
 */
class SimpleCache {
  /**
   * 
   * @param {object} param0 
   * @param {typeof this.get} param0.get
   * @param {number} param0.timeout
   */
  constructor({
    get,
    timeout = 60 * 1000
  }) {
    Object.assign(this, arguments[0]);
    this.timeout = timeout;

    /**
     * @returns {Promise<Type>}
     */
    this.get = async () => {
      if (this[cacheData] && Date.now() - (this[cacheDataLastRefresh] || 0) < this.timeout /**/) {
        return this[cacheData];
      }
      const fetchAnew = async () => {
        this[cacheData] = await get();
        this[cacheDataLastRefresh] = Date.now();
        return this[cacheData];
      };
      if (this[fetchPromise]) {
        try {
          const results = await this[fetchPromise];
          delete this[fetchPromise];
          return results;
        } catch {
          const results = await (this[fetchPromise] = fetchAnew());
          delete this[fetchPromise];
          return results;
        }
      } else {
        return await (this[fetchPromise] = fetchAnew());
      }
    };
  }
  /**
   * This method invalidates the data stored in the cache
   */
  invalidate() {
    delete this[cacheData];
    delete this[cacheDataLastRefresh];
  }
}
exports.default = SimpleCache;