Dynamic RSAA (redux-api-middleware) cache middleware. Must come before rssa in middleware order.

rsaa-cache-middleware.js

import { RSAA } from 'redux-api-middleware';
import get from 'lodash/get';

/**
 * Intercept redux api middleware actions and bailout of api resource requests
 * if the resource is already in the store.
 *
 * NOTE: State always gets updated on non-GET requests, essentially updating our "cache"
 *
 * Examples of resource routes that we want to cache:
 * - /collection
 * - /collection/<primary-key>
 *
 * Note: <primary-key> has to be something with non-alpha characters. guids, eth address, integer,
 * mongoid's would all work, but it's not a perfect science. Adjust the regex accordingly.
 *
 * @see {@link https://github.com/agraboso/redux-api-middleware#bailing-out}
 */
export default function cacheMiddleware() {
  return next => action => {
    // if action is an api GET request for a resource we already have, prevent the request
    if (action[RSAA] && action[RSAA].method === 'GET' && !action[RSAA].bailout) {
      const url = new URL(action[RSAA].endpoint);
      const pathParts = url.pathname.split('/').slice(1);

      // if it's not a resource route then just keep moving
      // NOTE: For "resource" routes, the last item in the url path should be an address
      // and the second to last item should be the resource name/type.
      let resource = pathParts[pathParts.length - 2];
      let primaryKey = pathParts[pathParts.length - 1];
      if (!resource || primaryKey.match(/^[a-zA-Z-_]+$/)) {
        resource = pathParts[pathParts.length - 1];
        primaryKey = null;
      }

      // Set the bailout property of the RSAA action object. Should be a function that returns
      // a boolean. If it's true the request will NOT happen. Function takes redux state as a param.
      // @see {@link https://github.com/agraboso/redux-api-middleware#bailing-out}
      // eslint-disable-next-line no-param-reassign
      action[RSAA].bailout = state => get(state, `entities.${resource}${primaryKey && `.${primaryKey}`}`, false) !== false;
    }

    return next(action);
  };
}