From 2286587c41d1033c3b15cb3c5fca58a5f0018a52 Mon Sep 17 00:00:00 2001
From: Sebastian Benz <sebastian.benz@gmail.com>
Date: Mon, 4 Feb 2019 16:29:15 +0100
Subject: [PATCH] implement caching strategy (#1366)

---
 boilerplate/templates/index.html      |  2 +-
 platform/lib/platform.js              |  4 ++
 platform/lib/utils/CachingStrategy.js | 66 +++++++++++++++++++++++++++
 platform/lib/utils/cacheHelpers.js    | 49 ++++++++++++++++++++
 playground/backend/api.js             |  3 ++
 playground/backend/index.js           | 13 +++++-
 6 files changed, 135 insertions(+), 2 deletions(-)
 create mode 100644 platform/lib/utils/CachingStrategy.js
 create mode 100644 platform/lib/utils/cacheHelpers.js

diff --git a/boilerplate/templates/index.html b/boilerplate/templates/index.html
index a7d2c81fd54..ea9b6208de6 100644
--- a/boilerplate/templates/index.html
+++ b/boilerplate/templates/index.html
@@ -65,7 +65,7 @@
       {{> 'amp-stories.svg' }}
       {{> 'amp-websites.svg' }}
       {{> 'amp-ads.svg' }}
-      {{> 'amp-emails.svg' }}
+      {{> 'amp-email.svg' }}
     </svg>
     <amp-state id="config">
       <script type="application/json">
diff --git a/platform/lib/platform.js b/platform/lib/platform.js
index a031476ed32..51600a2a197 100644
--- a/platform/lib/platform.js
+++ b/platform/lib/platform.js
@@ -18,7 +18,9 @@
 
 const signale = require('signale');
 const express = require('express');
+const compression = require('compression');
 const ampCors = require('amp-toolbox-cors');
+const defaultCachingStrategy = require('./utils/CachingStrategy.js').defaultStrategy;
 
 const config = require('./config.js');
 const routers = {
@@ -54,6 +56,8 @@ class Platform {
       });
     }
 
+    this.server.use(compression());
+    this.server.use(defaultCachingStrategy);
     this._enableCors();
 
     this._check();
diff --git a/platform/lib/utils/CachingStrategy.js b/platform/lib/utils/CachingStrategy.js
new file mode 100644
index 00000000000..ea883d6f539
--- /dev/null
+++ b/platform/lib/utils/CachingStrategy.js
@@ -0,0 +1,66 @@
+/**
+ * Copyright 2018 The AMP HTML Authors. 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.
+ */
+
+const mime = require('mime-types');
+const ms = require('ms');
+const {setMaxAge, setImmutable} = require('./cacheHelpers.js');
+
+const IMMUTABLE = 'immutable';
+
+const maxAgePerMimeType = [
+  [/text\/.+$/i, maxAge('1h')],
+  [/image\/.+$/i, maxAge('1d')],
+  [/video\/.+$/i, maxAge('1w')],
+  [/application\/json$/i, maxAge('1h')],
+  [/application\/javascript$/i, maxAge('1h')],
+  [/font\/.+$/i, IMMUTABLE],
+];
+
+const defaultMaxAge = maxAge('1m');
+
+function defaultStrategy(request, response, next) {
+  const mimeType = mime.lookup(request.path) ||
+    extractMimeFromAcceptHeader(request.headers.accept);
+  if (!mimeType) {
+    setMaxAge(response, defaultMaxAge);
+    next();
+    return;
+  }
+  const maxAgeMapping = maxAgePerMimeType.find((mapping) => mapping[0].test(mimeType));
+  const maxAge = maxAgeMapping ? maxAgeMapping[1] : defaultMaxAge;
+  if (maxAge === IMMUTABLE) {
+    setImmutable(response);
+  } else {
+    setMaxAge(response, maxAge);
+  }
+  next();
+}
+
+function extractMimeFromAcceptHeader(string) {
+  if (!string) {
+    return '';
+  }
+  return string.split(',')[0];
+}
+
+function maxAge(string) {
+  return Math.floor(ms(string) / 1000);
+}
+
+module.exports = {
+  defaultStrategy,
+};
+
diff --git a/platform/lib/utils/cacheHelpers.js b/platform/lib/utils/cacheHelpers.js
new file mode 100644
index 00000000000..8e683927c86
--- /dev/null
+++ b/platform/lib/utils/cacheHelpers.js
@@ -0,0 +1,49 @@
+/**
+ * Copyright 2018 The AMP HTML Authors. 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.
+ */
+
+function setNoCache(response) {
+  response.setHeader('Cache-Control', 'private, no-cache, no-store, must-revalidate');
+}
+
+function setMaxAge(response, maxAge) {
+  response.setHeader('Cache-Control', `public, max-age=${maxAge}`);
+}
+
+function setImmutable(response) {
+  response.setHeader('Cache-Control', `max-age=365000000, immutable`);
+}
+
+function setNoSniff(response) {
+  response.setHeader('x-content-type-options', 'nosniff');
+}
+
+function setHsts(response) {
+  response.setHeader('strict-transport-security', 'max-age=31536000; includeSubDomains; preload');
+}
+
+function setXssProtection(response) {
+  response.setHeader('x-xss-protection', '1; mode=block');
+}
+
+function setAmpCSP(response) {
+  response.setHeader('content-security-policy', `default-src * blob: data:; script-src blob: https://cdn.ampproject.org/esm/ https://cdn.ampproject.org/mp/ https://cdn.ampproject.org/rtv/ https://cdn.ampproject.org/sp/ https://cdn.ampproject.org/sw/ https://cdn.ampproject.org/v0.js https://cdn.ampproject.org/v0/ https://cdn.ampproject.org/viewer/; object-src 'none'; style-src 'unsafe-inline' https://cdn.ampproject.org/rtv/ https://cdn.materialdesignicons.com https://cloud.typography.com https://fast.fonts.net https://fonts.googleapis.com https://maxcdn.bootstrapcdn.com https://p.typekit.net https://pro.fontawesome.com https://use.fontawesome.com https://use.typekit.net; report-uri https://csp-collector.appspot.com/csp/amp`)
+}
+
+module.exports = {
+  setNoCache,
+  setMaxAge,
+  setImmutable,
+};
diff --git a/playground/backend/api.js b/playground/backend/api.js
index 07851c36b6f..92a828b96fc 100644
--- a/playground/backend/api.js
+++ b/playground/backend/api.js
@@ -17,9 +17,11 @@
 const express = require('express');
 const fetch = require('node-fetch');
 const URL = require('url').URL;
+const {setMaxAge} = require('../../platform/lib/utils/cacheHelpers.js');
 // eslint-disable-next-line new-cap
 const api = express.Router();
 
+const ONE_HOUR = 60 * 60;
 const VALID_ORIGINS = new Set([
   'amp.dev',
   'api.amp.dev',
@@ -40,6 +42,7 @@ api.get('/fetch', async (request, response) => {
   try {
     const doc = await fetchDocument(url, request.headers.host);
     response.send(doc);
+    setMaxAge(response, ONE_HOUR);
   } catch (error) {
     console.error('Could not fetch URL', error);
     response.send(`Could not fetch URL ${url}`).status(400).end();
diff --git a/playground/backend/index.js b/playground/backend/index.js
index 7c4b36065d2..ee65d40e0d8 100644
--- a/playground/backend/index.js
+++ b/playground/backend/index.js
@@ -16,13 +16,24 @@
 
 const path = require('path');
 const express = require('express');
+const {setImmutable} = require('../../platform/lib/utils/cacheHelpers.js');
 // eslint-disable-next-line new-cap
 const playground = express.Router();
 
 playground.use(express.static(
     path.join(__dirname, '../dist'),
-    {extensions: ['html']},
+    {
+      extensions: ['html'],
+      setHeaders: setCustomCacheControl,
+    },
 ));
 playground.use('/api', require('./api.js'));
 
+function setCustomCacheControl(response, path) {
+  // playground assets are versioned
+  if (path.endsWith('.js') || path.endsWith('.css')) {
+    setImmutable(response);
+  }
+}
+
 module.exports = playground;