Add support for app shell navigation via AMP Shadow DOM

.eslintrc

@@ -16,7 +16,8 @@
 		"react"
 	],
 	"env": {
-		"browser": true
+		"browser": true,
+		"es6": true
 	},
 	"globals": {
 		"wp": true,

.jshintignore

@@ -1,4 +1,7 @@
 **/*.min.js
 **/node_modules/**
 **/vendor/**
-**/assets/js/*-compiled.js
+**/assets/js/*-compiled.js
+**/assets/js/amp-wp-app-shell.js
+**/assets/js/amp-service-worker-offline-commenting.js
+**/assets/js/amp-service-worker-runtime-precaching.js

amp.php

@@ -162,9 +162,14 @@ function amp_init() {
 	 */
 	do_action( 'amp_init' );
 
+	global $amp_service_worker;
+	$amp_service_worker = new AMP_Service_Worker();
+	$amp_service_worker->init();
+
 	add_rewrite_endpoint( amp_get_slug(), EP_PERMALINK );
 
 	add_filter( 'allowed_redirect_hosts', array( 'AMP_HTTP', 'filter_allowed_redirect_hosts' ) );
+	add_filter( 'wp_redirect', array( 'AMP_HTTP', 'add_purged_query_vars' ) );
 	AMP_HTTP::purge_amp_query_vars();
 	AMP_HTTP::send_cors_headers();
 	AMP_HTTP::handle_xhr_request();
@@ -509,6 +514,7 @@ function _amp_bootstrap_customizer() {
  * Redirects the old AMP URL to the new AMP URL.
  *
  * If post slug is updated the amp page with old post slug will be redirected to the updated url.
+ * Also includes all original query vars.
  *
  * @since 0.5
  * @deprecated This function is irrelevant when 'amp' theme support is added.

assets/js/amp-service-worker-offline-commenting.js

@@ -0,0 +1,45 @@
+/* global ERROR_MESSAGES, SITE_URL */
+{
+	const queue = new wp.serviceWorker.backgroundSync.Queue( 'amp-wpPendingComments' );
+	const errorMessages = ERROR_MESSAGES;
+
+	const commentHandler = ( { event } ) => {
+		const clonedRequest = event.request.clone();
+		return fetch( event.request ).catch( () => {
+			return clonedRequest.blob().then( ( body ) => {
+				const queuedRequest = new Request( event.request.url, {
+					method: event.request.method,
+					headers: event.request.headers,
+					mode: event.request.mode,
+					credentials: event.request.credentials,
+					referrer: event.request.referrer,
+					redirect: 'follow',
+					body: body
+				} );
+
+				// Add request to queue. @todo Replace when upgrading to Workbox v4!
+				queue.addRequest( queuedRequest );
+
+				const jsonBody = JSON.stringify( { message: errorMessages.comment } );
+				return new Response( jsonBody, {
+					status: 202,
+					statusText: 'Accepted',
+					headers: {
+						'Access-Control-Allow-Origin': SITE_URL,
+						'Access-Control-Allow-Credentials': 'true',
+						'Content-Type': 'application/json; charset=UTF-8',
+						'Access-Control-Expose-Headers': 'AMP-Access-Control-Allow-Source-Origin',
+						'AMP-Access-Control-Allow-Source-Origin': SITE_URL,
+						'Cache-Control': 'no-cache, must-revalidate, max-age=0'
+					}
+				} );
+			} );
+		} );
+	};
+
+	wp.serviceWorker.routing.registerRoute(
+		/\/wp-comments-post\.php\?.*_wp_amp_action_xhr_converted.*/,
+		commentHandler,
+		'POST'
+	);
+}

assets/js/amp-service-worker-runtime-precaching.js

@@ -0,0 +1,9 @@
+/* global URLS */
+// See AMP_Service_Workers::add_amp_runtime_caching() and <https://github.com/ampproject/amp-by-example/blob/a4d798cac6a534e0c46e78944a2718a8dab3c057/boilerplate-generator/templates/files/serviceworkerJs.js#L9-L22>.
+{
+	self.addEventListener( 'install', event => {
+		event.waitUntil(
+			caches.open( wp.serviceWorker.core.cacheNames.runtime ).then( cache => cache.addAll( URLS ) )
+		);
+	} );
+}