WIP - add extractor, generate snippet_data

node_modules/workbox-cache-expiration/Plugin.mjs

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+/*
+ Copyright 2016 Google Inc. All Rights Reserved.
+ Licensed under the Apache License, Version 2.0 (the "License");
+ you may not use this file except in compliance with the License.
+ You may obtain a copy of the License at
+     http://www.apache.org/licenses/LICENSE-2.0
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+*/
+
+import {CacheExpiration} from './CacheExpiration.mjs';
+import {WorkboxError} from 'workbox-core/_private/WorkboxError.mjs';
+import {assert} from 'workbox-core/_private/assert.mjs';
+import {cacheNames} from 'workbox-core/_private/cacheNames.mjs';
+import {registerQuotaErrorCallback} from 'workbox-core/index.mjs';
+
+import './_version.mjs';
+
+/**
+ * This plugin can be used in the Workbox APIs to regularly enforce a
+ * limit on the age and / or the number of cached requests.
+ *
+ * Whenever a cached request is used or updated, this plugin will look
+ * at the used Cache and remove any old or extra requests.
+ *
+ * When using `maxAgeSeconds`, requests may be used *once* after expiring
+ * because the expiration clean up will not have occurred until *after* the
+ * cached request has been used. If the request has a "Date" header, then
+ * a light weight expiration check is performed and the request will not be
+ * used immediately.
+ *
+ * When using `maxEntries`, the last request to be used will be the request
+ * that is removed from the Cache.
+ *
+ * @memberof workbox.expiration
+ */
+class Plugin {
+  /**
+   * @param {Object} config
+   * @param {number} [config.maxEntries] The maximum number of entries to cache.
+   * Entries used the least will be removed as the maximum is reached.
+   * @param {number} [config.maxAgeSeconds] The maximum age of an entry before
+   * it's treated as stale and removed.
+   * @param {boolean} [config.purgeOnQuotaError] Whether to opt this cache in to
+   * automatic deletion if the available storage quota has been exceeded.
+   */
+  constructor(config = {}) {
+    if (process.env.NODE_ENV !== 'production') {
+      if (!(config.maxEntries || config.maxAgeSeconds)) {
+        throw new WorkboxError('max-entries-or-age-required', {
+          moduleName: 'workbox-cache-expiration',
+          className: 'Plugin',
+          funcName: 'constructor',
+        });
+      }
+
+      if (config.maxEntries) {
+        assert.isType(config.maxEntries, 'number', {
+          moduleName: 'workbox-cache-expiration',
+          className: 'Plugin',
+          funcName: 'constructor',
+          paramName: 'config.maxEntries',
+        });
+      }
+
+      if (config.maxAgeSeconds) {
+        assert.isType(config.maxAgeSeconds, 'number', {
+          moduleName: 'workbox-cache-expiration',
+          className: 'Plugin',
+          funcName: 'constructor',
+          paramName: 'config.maxAgeSeconds',
+        });
+      }
+    }
+
+    this._config = config;
+    this._maxAgeSeconds = config.maxAgeSeconds;
+    this._cacheExpirations = new Map();
+
+    if (config.purgeOnQuotaError) {
+      registerQuotaErrorCallback(() => this.deleteCacheAndMetadata());
+    }
+  }
+
+  /**
+   * A simple helper method to return a CacheExpiration instance for a given
+   * cache name.
+   *
+   * @param {string} cacheName
+   * @return {CacheExpiration}
+   *
+   * @private
+   */
+  _getCacheExpiration(cacheName) {
+    if (cacheName === cacheNames.getRuntimeName()) {
+      throw new WorkboxError('expire-custom-caches-only');
+    }
+
+    let cacheExpiration = this._cacheExpirations.get(cacheName);
+    if (!cacheExpiration) {
+      cacheExpiration = new CacheExpiration(cacheName, this._config);
+      this._cacheExpirations.set(cacheName, cacheExpiration);
+    }
+    return cacheExpiration;
+  }
+
+  /**
+   * A "lifecycle" callback that will be triggered automatically by the
+   * `workbox.runtimeCaching` handlers when a `Response` is about to be returned
+   * from a [Cache](https://developer.mozilla.org/en-US/docs/Web/API/Cache) to
+   * the handler. It allows the `Response` to be inspected for freshness and
+   * prevents it from being used if the `Response`'s `Date` header value is
+   * older than the configured `maxAgeSeconds`.
+   *
+   * @param {Object} options
+   * @param {string} options.cacheName Name of the cache the response is in.
+   * @param {Response} options.cachedResponse The `Response` object that's been
+   *     read from a cache and whose freshness should be checked.
+   * @return {Response} Either the `cachedResponse`, if it's
+   *     fresh, or `null` if the `Response` is older than `maxAgeSeconds`.
+   *
+   * @private
+   */
+  cachedResponseWillBeUsed({cacheName, cachedResponse}) {
+    if (!cachedResponse) {
+      return null;
+    }
+
+    let isFresh = this._isResponseDateFresh(cachedResponse);
+
+    // Expire entries to ensure that even if the expiration date has
+    // expired, it'll only be used once.
+    const cacheExpiration = this._getCacheExpiration(cacheName);
+    cacheExpiration.expireEntries();
+
+    return isFresh ? cachedResponse : null;
+  }
+
+  /**
+   * @param {Response} cachedResponse
+   * @return {boolean}
+   *
+   * @private
+   */
+  _isResponseDateFresh(cachedResponse) {
+    if (!this._maxAgeSeconds) {
+      // We aren't expiring by age, so return true, it's fresh
+      return true;
+    }
+
+    // Check if the 'date' header will suffice a quick expiration check.
+    // See https://github.com/GoogleChromeLabs/sw-toolbox/issues/164 for
+    // discussion.
+    const dateHeaderTimestamp = this._getDateHeaderTimestamp(cachedResponse);
+    if (dateHeaderTimestamp === null) {
+      // Unable to parse date, so assume it's fresh.
+      return true;
+    }
+
+    // If we have a valid headerTime, then our response is fresh iff the
+    // headerTime plus maxAgeSeconds is greater than the current time.
+    const now = Date.now();
+    return dateHeaderTimestamp >= now - (this._maxAgeSeconds * 1000);
+  }
+
+  /**
+   * This method will extract the data header and parse it into a useful
+   * value.
+   *
+   * @param {Response} cachedResponse
+   * @return {number}
+   *
+   * @private
+   */
+  _getDateHeaderTimestamp(cachedResponse) {
+    if (!cachedResponse.headers.has('date')) {
+      return null;
+    }
+
+    const dateHeader = cachedResponse.headers.get('date');
+    const parsedDate = new Date(dateHeader);
+    const headerTime = parsedDate.getTime();
+
+    // If the Date header was invalid for some reason, parsedDate.getTime()
+    // will return NaN.
+    if (isNaN(headerTime)) {
+      return null;
+    }
+
+    return headerTime;
+  }
+
+  /**
+   * A "lifecycle" callback that will be triggered automatically by the
+   * `workbox.runtimeCaching` handlers when an entry is added to a cache.
+   *
+   * @param {Object} options
+   * @param {string} options.cacheName Name of the cache that was updated.
+   * @param {string} options.request The Request for the cached entry.
+   *
+   * @private
+   */
+  async cacheDidUpdate({cacheName, request}) {
+    if (process.env.NODE_ENV !== 'production') {
+      assert.isType(cacheName, 'string', {
+        moduleName: 'workbox-cache-expiration',
+        className: 'Plugin',
+        funcName: 'cacheDidUpdate',
+        paramName: 'cacheName',
+      });
+      assert.isInstance(request, Request, {
+        moduleName: 'workbox-cache-expiration',
+        className: 'Plugin',
+        funcName: 'cacheDidUpdate',
+        paramName: 'request',
+      });
+    }
+
+    const cacheExpiration = this._getCacheExpiration(cacheName);
+    await cacheExpiration.updateTimestamp(request.url);
+    await cacheExpiration.expireEntries();
+  }
+
+
+  /**
+   * This is a helper method that performs two operations:
+   *
+   * - Deletes *all* the underlying Cache instances associated with this plugin
+   * instance, by calling caches.delete() on you behalf.
+   * - Deletes the metadata from IndexedDB used to keep track of expiration
+   * details for each Cache instance.
+   *
+   * When using cache expiration, calling this method is preferable to calling
+   * `caches.delete()` directly, since this will ensure that the IndexedDB
+   * metadata is also cleanly removed and open IndexedDB instances are deleted.
+   *
+   * Note that if you're *not* using cache expiration for a given cache, calling
+   * `caches.delete()` and passing in the cache's name should be sufficient.
+   * There is no Workbox-specific method needed for cleanup in that case.
+   */
+  async deleteCacheAndMetadata() {
+    // Do this one at a time instead of all at once via `Promise.all()` to
+    // reduce the chance of inconsistency if a promise rejects.
+    for (const [cacheName, cacheExpiration] of this._cacheExpirations) {
+      await caches.delete(cacheName);
+      await cacheExpiration.delete();
+    }
+
+    // Reset this._cacheExpirations to its initial state.
+    this._cacheExpirations = new Map();
+  }
+}
+
+export {Plugin};