cache.js

/**
 *  @file Common cache methods
 *  @author Avana Vana <avana@esovdb.org>
 *  @module cache
 */

const fs = require('fs');

/** @constant {number} cacheInterval - The duration, in seconds after which a cache file is considered stale (default: 300s = 5m) */
let cacheInterval = 60 * 5;

module.exports = {
  
  /**
   *  Sets the cache interval (in integer seconds)
   *
   *  @method setCacheInterval
   *  @param {number} interval - The number of seconds to set the cache interval to
   */
  
  setCacheInterval: (interval) => {
    cacheInterval = interval;
  },
  
  /**
   *  Uses a request's path to write a response as a file to the cache
   *
   *  @method writeCacheWithPath
   *  @param {string} path - The request's URL, with query params
   *  @param {Object} data - The response, as a Javascript Object, from the request
   */
  
  writeCacheWithPath: (path, data) => {
    const queryPath = path.replace('?', '/');
    
    `/${queryPath}`
      .split('/')
      .splice(0, `/${queryPath}`.split('/').length - 1)
      .reduce((p, c) => {
        p += `${c}/`;
        !fs.existsSync(p) && fs.mkdirSync(p);
        return p;
      });

    fs.writeFile(queryPath, JSON.stringify(data), (err) => {
      if (err) throw new Error(err);
      else console.log(`Cache write succeeded: ${path}`);
    });
  },
  
  /**
   *  Uses a request's path to read a file from the cache if it exists or is still fresh
   *
   *  @method writeCacheWithPath
   *  @param {string} path - The request's URL, with query params
   *  @returns {?Object} Returns cache JSON data as an object if it exists and is still fresh, else null
   */
  
  readCacheWithPath: (path, stale = true) => {
    if (stale) {
      path = path.replace('?', '/');

      if (fs.existsSync(path)) {
        const cachedTime = fs.statSync(path).ctime;
        stale = (new Date().getTime() - cachedTime) / 1000 > cacheInterval ? true : false;
      }
    }

    return stale ? null : JSON.parse(fs.readFileSync(path, 'utf8'));
  }
};