Offline commenting

.jshintignore

@@ -2,3 +2,5 @@ wp-includes/js/service-worker.js
 wp-includes/js/service-worker-navigation-routing.js
 wp-includes/js/service-worker-precaching.js
 wp-includes/js/service-worker-stream-combiner.js
+amp/amp-service-worker-offline-commenting.js
+wp-includes/js/service-worker-offline-commenting.js

amp/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'
+	);
+}

amp/class-amp-service-worker.php

@@ -38,6 +38,7 @@ public function init() {
 		add_action( 'wp', array( $this, 'add_install_hooks' ) );
 		add_action( 'wp_front_service_worker', array( $this, 'add_amp_runtime_caching' ) );
 		add_action( 'wp_front_service_worker', array( $this, 'add_image_runtime_caching' ) );
+		add_action( 'wp_front_service_worker', array( $this, 'add_live_list_offline_commenting' ) );
 	}
 
 	/**
@@ -124,6 +125,43 @@ public function add_image_runtime_caching( $service_workers ) {
 		);
 	}
 
+	/**
+	 * Add live list offline commenting service worker script.
+	 *
+	 * @param object $service_workers WP Service Workers object.
+	 */
+	public function add_live_list_offline_commenting( $service_workers ) {
+		if ( ! ( $service_workers instanceof WP_Service_Worker_Scripts ) ) {
+			_doing_it_wrong( __METHOD__, esc_html__( 'Expected argument to be WP_Service_Worker_Scripts.', 'amp' ), '1.0' );
+			return;
+		}
+
+		$theme_support = AMP_Theme_Support::get_theme_support_args();
+		if ( empty( $theme_support['comments_live_list'] ) ) {
+			return;
+		}
+
+		$service_workers->register(
+			'amp-offline-commenting',
+			function() {
+				$js = file_get_contents( dirname( __FILE__ ) . '/amp-service-worker-offline-commenting.js' ); // phpcs:ignore WordPress.WP.AlternativeFunctions.file_get_contents_file_get_contents, WordPress.WP.AlternativeFunctions.file_system_read_file_get_contents
+				$js = preg_replace( '#/\*\s*global.+?\*/#', '', $js );
+				$js = str_replace(
+					'ERROR_MESSAGES',
+					wp_json_encode( wp_service_worker_get_error_messages() ),
+					$js
+				);
+				$js = str_replace(
+					'SITE_URL',
+					wp_json_encode( site_url() ),
+					$js
+				);
+				return $js;
+			}
+		);
+
+	}
+
 	/**
 	 * Register URLs that will be precached in the runtime cache. (Yes, this sounds somewhat strange.)
 	 *

wp-includes/components/class-wp-service-worker-navigation-routing-component.php

@@ -358,11 +358,19 @@ public function serve( WP_Service_Worker_Scripts $scripts ) {
 			);
 		}
 
+		$scripts->register(
+			'wp-offline-commenting',
+			array(
+				'src'  => array( $this, 'get_offline_commenting_script' ),
+				'deps' => array( 'wp-base-config' ),
+			)
+		);
+
 		$scripts->register(
 			'wp-navigation-routing',
 			array(
 				'src'  => array( $this, 'get_script' ),
-				'deps' => array( 'wp-base-config' ),
+				'deps' => array( 'wp-base-config', 'wp-offline-commenting' ),
 			)
 		);
 
@@ -424,6 +432,7 @@ public function serve( WP_Service_Worker_Scripts $scripts ) {
 			'BLACKLIST_PATTERNS'               => wp_service_worker_json_encode( $this->get_blacklist_patterns() ),
 			'SHOULD_STREAM_RESPONSE'           => wp_service_worker_json_encode( $should_stream_response ),
 			'STREAM_HEADER_FRAGMENT_QUERY_VAR' => wp_service_worker_json_encode( self::STREAM_FRAGMENT_QUERY_VAR ),
+			'ERROR_MESSAGES'                   => wp_service_worker_json_encode( wp_service_worker_get_error_messages() ),
 		);
 	}
 
@@ -466,7 +475,7 @@ public function get_blacklist_patterns() {
 	 * @return int Hook priority. A higher number means a lower priority.
 	 */
 	public function get_priority() {
-		return -99999;
+		return 99;
 	}
 
 	/**
@@ -484,4 +493,20 @@ public function get_script() {
 			$script
 		);
 	}
+
+	/**
+	 * Get script for offline commenting requests.
+	 *
+	 * @return string Script.
+	 */
+	public function get_offline_commenting_script() {
+		$script = file_get_contents( PWA_PLUGIN_DIR . '/wp-includes/js/service-worker-offline-commenting.js' ); // phpcs:ignore WordPress.WP.AlternativeFunctions.file_get_contents_file_get_contents
+		$script = preg_replace( '#/\*\s*global.+?\*/#', '', $script );
+
+		return str_replace(
+			array_keys( $this->replacements ),
+			array_values( $this->replacements ),
+			$script
+		);
+	}
 }