Issue 959: cache post processor response

includes/class-amp-theme-support.php

@@ -19,6 +19,13 @@ class AMP_Theme_Support {
 	 */
 	const SCRIPTS_PLACEHOLDER = '<!-- AMP:SCRIPTS_PLACEHOLDER -->';
 
+	/**
+	 * Response cache group name.
+	 *
+	 * @var string
+	 */
+	const RESPONSE_CACHE_GROUP = 'amp-reponse';
+
 	/**
 	 * Sanitizer classes.
 	 *
@@ -970,8 +977,6 @@ public static function is_output_buffering() {
 	 * @return string Processed Response.
 	 */
 	public static function finish_output_buffering( $response ) {
-		AMP_Response_Headers::send_server_timing( 'amp_output_buffer', -self::$init_start_time, 'AMP Output Buffer' );
-
 		self::$is_output_buffering = false;
 		return self::prepare_response( $response );
 	}
@@ -1036,10 +1041,35 @@ public static function prepare_response( $response, $args = array() ) {
 				'allow_dirty_styles'      => self::is_customize_preview_iframe(), // Dirty styles only needed when editing (e.g. for edit shortcodes).
 				'allow_dirty_scripts'     => is_customize_preview(), // Scripts are always needed to inject changeset UUID.
 				'disable_invalid_removal' => $is_validation_debug_mode,
+				'enable_response_caching' => (
+					( ! defined( 'WP_DEBUG' ) || true !== WP_DEBUG )
+					&&
+					! AMP_Validation_Utils::should_validate_response()
+				),
 			),
 			$args
 		);
 
+		// Return cache if enabled and found.
+		if ( true === $args['enable_response_caching'] ) {
+			// Set response cache hash, the data values dictates whether a new hash key should be generated or not.
+			$response_cache_key = md5( wp_json_encode( array(
+				$args,
+				$response,
+				self::$sanitizer_classes,
+				self::$embed_handlers,
+				AMP__VERSION,
+			) ) );
+
+			$response_cache = wp_cache_get( $response_cache_key, self::RESPONSE_CACHE_GROUP );
+
+			if ( ! empty( $response_cache ) ) {
+				return $response_cache;
+			}
+		}
+
+		AMP_Response_Headers::send_server_timing( 'amp_output_buffer', -self::$init_start_time, 'AMP Output Buffer' );
+
 		$dom_parse_start = microtime( true );
 
 		/*
@@ -1140,6 +1170,11 @@ public static function prepare_response( $response, $args = array() ) {
 
 		AMP_Response_Headers::send_server_timing( 'amp_dom_serialize', -$dom_serialize_start, 'AMP DOM Serialize' );
 
+		// Cache response if enabled.
+		if ( true === $args['enable_response_caching'] ) {
+			wp_cache_set( $response_cache_key, $response, self::RESPONSE_CACHE_GROUP, MONTH_IN_SECONDS );
+		}
+
 		return $response;
 	}
 

tests/test-class-amp-theme-support.php

@@ -1050,6 +1050,44 @@ public function test_prepare_response() {
 		$this->assertInstanceOf( 'DOMElement', $removed_nodes['script'] );
 		$this->assertInstanceOf( 'DOMAttr', $removed_nodes['onclick'] );
 		$this->assertInstanceOf( 'DOMAttr', $removed_nodes['handle'] );
+
+		$call_response = function() use ( $original_html ) {
+			return AMP_Theme_Support::prepare_response( $original_html, array(
+				'enable_response_caching' => true,
+			) );
+		};
+
+		// Test that first response isn't cached.
+		$first_response = $call_response();
+		$this->assertGreaterThan( 0, count( array_filter(
+			AMP_Response_Headers::$headers_sent,
+			function( $header ) {
+				return 'Server-Timing' === $header['name'];
+			}
+		) ) );
+
+		// Test that response cache is return upon second call.
+		AMP_Response_Headers::$headers_sent = array();
+		$this->assertEquals( $first_response, $call_response() );
+		$this->assertSame( 0, count( array_filter(
+			AMP_Response_Headers::$headers_sent,
+			function( $header ) {
+				return 'Server-Timing' === $header['name'];
+			}
+		) ) );
+
+		// Test new cache upon argument change.
+		AMP_Response_Headers::$headers_sent = array();
+		AMP_Theme_Support::prepare_response( $original_html, array(
+			'enable_response_caching' => true,
+			'test_reset_by_arg'       => true,
+		) );
+		$this->assertGreaterThan( 0, count( array_filter(
+			AMP_Response_Headers::$headers_sent,
+			function( $header ) {
+				return 'Server-Timing' === $header['name'];
+			}
+		) ) );
 	}
 
 	/**