Improve handling of WordPress post embeds

includes/amp-helper-functions.php

@@ -1407,6 +1407,7 @@ function amp_get_content_embed_handlers( $post = null ) {
 			AMP_Gfycat_Embed_Handler::class       => [],
 			AMP_Imgur_Embed_Handler::class        => [],
 			AMP_Scribd_Embed_Handler::class       => [],
+			AMP_WordPress_Embed_Handler::class    => [],
 			AMP_WordPress_TV_Embed_Handler::class => [],
 		],
 		$post

includes/class-amp-theme-support.php

@@ -845,9 +845,6 @@ public static function get_supportable_templates( $options = [] ) {
 	 */
 	public static function add_hooks() {
 
-		// This is not needed when post embeds are embedded via <amp-wordpress-embed>. See <https://github.com/ampproject/amp-wp/issues/809>.
-		remove_action( 'wp_head', 'wp_oembed_add_host_js' );
-
 		// Prevent emoji detection and emoji loading since platforms/browsers now support emoji natively (and Twemoji is not AMP-compatible).
 		add_filter( 'wp_resource_hints', [ __CLASS__, 'filter_resource_hints_to_remove_emoji_dns_prefetch' ], 10, 2 );
 		remove_action( 'wp_head', 'print_emoji_detection_script', 7 );

includes/embeds/class-amp-wordpress-embed-handler.php

@@ -0,0 +1,144 @@
+<?php
+/**
+ * Class AMP_WordPress_Embed_Handler
+ *
+ * @package AMP
+ */
+
+use AmpProject\Extension;
+use AmpProject\Dom\Document;
+use AmpProject\Dom\Element;
+use AmpProject\Html\Attribute;
+use AmpProject\Html\Tag;
+use AmpProject\Layout;
+
+/**
+ * Class AMP_WordPress_Embed_Handler
+ *
+ * @since 2.2.2
+ */
+class AMP_WordPress_Embed_Handler extends AMP_Base_Embed_Handler {
+
+	/**
+	 * Default height.
+	 *
+	 * Note that 200px is the minimum that WordPress allows for a post embed. This minimum height is enforced by
+	 * WordPress in the wp.receiveEmbedMessage() function, and the <amp-wordpress-embed> also enforces that same
+	 * minimum height. It is important for the minimum height to be initially used because if the actual post embed
+	 * window is _less_ than the initial, then no overflow button will be presented to resize the iframe to be
+	 * _smaller_. So this ensures that the iframe will only ever overflow to grow in height.
+	 *
+	 * @var int
+	 */
+	protected $DEFAULT_HEIGHT = 200;
+
+	/**
+	 * Tag.
+	 *
+	 * @var string AMP amp-wordpress-embed tag
+	 */
+	private $amp_tag = Extension::WORDPRESS_EMBED;
+
+	/**
+	 * Register embed.
+	 */
+	public function register_embed() {
+		remove_action( 'wp_head', 'wp_oembed_add_host_js' );
+	}
+
+	/**
+	 * Unregister embed.
+	 */
+	public function unregister_embed() {
+		add_action( 'wp_head', 'wp_oembed_add_host_js' );
+	}
+
+	/**
+	 * Sanitize WordPress embed raw embeds.
+	 *
+	 * @param Document $dom Document.
+	 *
+	 * @return void
+	 */
+	public function sanitize_raw_embeds( Document $dom ) {
+
+		$embed_iframes = $dom->xpath->query( '//iframe[ @src and contains( concat( " ", normalize-space( @class ), " " ), " wp-embedded-content " ) ]', $dom->body );
+		foreach ( $embed_iframes as $embed_iframe ) {
+			/** @var Element $embed_iframe */
+
+			// Remove embed script included when user copies HTML Embed code, per get_post_embed_html().
+			$embed_script = $dom->xpath->query( './following-sibling::script[ contains( text(), "wp.receiveEmbedMessage" ) ]', $embed_iframe )->item( 0 );
+			if ( $embed_script instanceof Element ) {
+				$embed_script->parentNode->removeChild( $embed_script );
+			}
+
+			// If the post embed iframe got wrapped in a paragraph by `wpautop()`, unwrap it. This happens not with
+			// the Embed block but it does with the [embed] shortcode.
+			$is_wrapped_in_paragraph = (
+				$embed_iframe->parentNode instanceof Element
+				&&
+				Tag::P === $embed_iframe->parentNode->tagName
+			);
+
+			// If the iframe is wrapped in a paragraph, but it's not the only node, then abort.
+			if ( $is_wrapped_in_paragraph && 1 !== $embed_iframe->parentNode->childNodes->length ) {
+				continue;
+			}
+
+			$embed_blockquote = $dom->xpath->query(
+				'./preceding-sibling::blockquote[ contains( concat( " ", normalize-space( @class ), " " ), " wp-embedded-content " ) ]',
+				$is_wrapped_in_paragraph ? $embed_iframe->parentNode : $embed_iframe
+			)->item( 0 );
+			if ( $embed_blockquote instanceof Element ) {
+
+				// Note that unwrap_p_element() is not being used here because it will do nothing if the paragraph
+				// happens to have an attribute on it, which is possible with the_content filters.
+				if ( $is_wrapped_in_paragraph && $embed_iframe->parentNode->parentNode instanceof Element ) {
+					$embed_iframe->parentNode->parentNode->replaceChild( $embed_iframe, $embed_iframe->parentNode );
+				}
+
+				$this->create_amp_wordpress_embed_and_replace_node( $dom, $embed_blockquote, $embed_iframe );
+			}
+		}
+	}
+
+	/**
+	 * Make final modifications to DOMNode
+	 *
+	 * @param Document $dom        The HTML Document.
+	 * @param Element  $blockquote The blockquote to be moved inside <amp-wordpress-embed>.
+	 * @param Element  $iframe     The iframe to be replaced with <amp-wordpress-embed>.
+	 */
+	private function create_amp_wordpress_embed_and_replace_node( Document $dom, Element $blockquote, Element $iframe ) {
+
+		$attributes = [
+			Attribute::HEIGHT => $this->args['height'],
+			Attribute::LAYOUT => Layout::FIXED_HEIGHT,
+		];
+		if ( $iframe->hasAttribute( Attribute::TITLE ) ) {
+			$attributes[ Attribute::TITLE ] = $iframe->getAttribute( Attribute::TITLE );
+		}
+
+		$src = $iframe->getAttribute( Attribute::SRC );
+
+		// Remove the secret which will be handled by amp-wordpress-embed.
+		$src = preg_replace( '/#\?secret=.+/', '', $src );
+		$blockquote->removeAttribute( 'data-secret' );
+
+		$attributes[ Attribute::DATA_URL ] = $src;
+
+		$amp_wordpress_embed_node = AMP_DOM_Utils::create_node(
+			$dom,
+			$this->amp_tag,
+			$attributes
+		);
+
+		$blockquote->setAttributeNode( $dom->createAttribute( Attribute::PLACEHOLDER ) );
+		$amp_wordpress_embed_node->appendChild( $blockquote );
+		$amp_wordpress_embed_node->appendChild( $this->create_overflow_button_element( $dom ) );
+
+		$iframe->parentNode->replaceChild( $amp_wordpress_embed_node, $iframe );
+
+		$this->did_convert_elements = true;
+	}
+}