StaleWhileRevalidate.ts

/*
  Copyright 2018 Google LLC

  Use of this source code is governed by an MIT-style
  license that can be found in the LICENSE file or at
  https://opensource.org/licenses/MIT.
*/

import {assert} from 'workbox-core/_private/assert.js';
import {logger} from 'workbox-core/_private/logger.js';
import {WorkboxError} from 'workbox-core/_private/WorkboxError.js';

import {cacheOkAndOpaquePlugin} from './plugins/cacheOkAndOpaquePlugin.js';
import {Strategy, StrategyOptions} from './Strategy.js';
import {StrategyHandler} from './StrategyHandler.js';
import {messages} from './utils/messages.js';
import './_version.js';

/**
 * An implementation of a
 * [stale-while-revalidate]{@link https://developers.google.com/web/fundamentals/instant-and-offline/offline-cookbook/#stale-while-revalidate}
 * request strategy.
 *
 * Resources are requested from both the cache and the network in parallel.
 * The strategy will respond with the cached version if available, otherwise
 * wait for the network response. The cache is updated with the network response
 * with each successful request.
 *
 * By default, this strategy will cache responses with a 200 status code as
 * well as [opaque responses]{@link https://developers.google.com/web/tools/workbox/guides/handle-third-party-requests}.
 * Opaque responses are cross-origin requests where the response doesn't
 * support [CORS]{@link https://enable-cors.org/}.
 *
 * If the network request fails, and there is no cache match, this will throw
 * a `WorkboxError` exception.
 *
 * @extends workbox-strategies.Strategy
 * @memberof workbox-strategies
 */
class StaleWhileRevalidate extends Strategy {
  /**
   * @param {Object} [options]
   * @param {string} [options.cacheName] Cache name to store and retrieve
   * requests. Defaults to cache names provided by
   * {@link workbox-core.cacheNames}.
   * @param {Array<Object>} [options.plugins] [Plugins]{@link https://developers.google.com/web/tools/workbox/guides/using-plugins}
   * to use in conjunction with this caching strategy.
   * @param {Object} [options.fetchOptions] Values passed along to the
   * [`init`](https://developer.mozilla.org/en-US/docs/Web/API/WindowOrWorkerGlobalScope/fetch#Parameters)
   * of [non-navigation](https://github.com/GoogleChrome/workbox/issues/1796)
   * `fetch()` requests made by this strategy.
   * @param {Object} [options.matchOptions] [`CacheQueryOptions`](https://w3c.github.io/ServiceWorker/#dictdef-cachequeryoptions)
   */
  constructor(options: StrategyOptions = {}) {
    super(options);

    // If this instance contains no plugins with a 'cacheWillUpdate' callback,
    // prepend the `cacheOkAndOpaquePlugin` plugin to the plugins list.
    if (!this.plugins.some((p) => 'cacheWillUpdate' in p)) {
      this.plugins.unshift(cacheOkAndOpaquePlugin);
    }
  }

  /**
   * @private
   * @param {Request|string} request A request to run this strategy for.
   * @param {workbox-strategies.StrategyHandler} handler The event that
   *     triggered the request.
   * @return {Promise<Response>}
   */
  async _handle(request: Request, handler: StrategyHandler): Promise<Response> {
    const logs = [];

    if (process.env.NODE_ENV !== 'production') {
      assert!.isInstance(request, Request, {
        moduleName: 'workbox-strategies',
        className: this.constructor.name,
        funcName: 'handle',
        paramName: 'request',
      });
    }

    const fetchAndCachePromise = handler.fetchAndCachePut(request).catch(() => {
      // Swallow this error because a 'no-response' error will be thrown in
      // main handler return flow. This will be in the `waitUntil()` flow.
    });
    void handler.waitUntil(fetchAndCachePromise);

    let response = await handler.cacheMatch(request);

    let error;
    if (response) {
      if (process.env.NODE_ENV !== 'production') {
        logs.push(
          `Found a cached response in the '${this.cacheName}'` +
            ` cache. Will update with the network response in the background.`,
        );
      }
    } else {
      if (process.env.NODE_ENV !== 'production') {
        logs.push(
          `No response found in the '${this.cacheName}' cache. ` +
            `Will wait for the network response.`,
        );
      }
      try {
        // NOTE(philipwalton): Really annoying that we have to type cast here.
        // https://github.com/microsoft/TypeScript/issues/20006
        response = (await fetchAndCachePromise) as Response | undefined;
      } catch (err) {
        if (err instanceof Error) {
          error = err;
        }
      }
    }

    if (process.env.NODE_ENV !== 'production') {
      logger.groupCollapsed(
        messages.strategyStart(this.constructor.name, request),
      );
      for (const log of logs) {
        logger.log(log);
      }
      messages.printFinalResponse(response);
      logger.groupEnd();
    }

    if (!response) {
      throw new WorkboxError('no-response', {url: request.url, error});
    }
    return response;
  }
}

export {StaleWhileRevalidate};