Carousel: improve detection of containers where we should add data

Fixes #13428

Until now we would rely on 2 str_replace to add Carousel data to div and ul containers in post content.
This worked, but wasn't smart enough to know to ignore specific divs like Columns blocks.

By using DOMDocument, we can go through the post content in a more readable way, to detect gallery blocks as well as regular galleries and images.

modules/carousel/jetpack-carousel.php

@@ -540,9 +540,52 @@ class_exists( 'Jetpack_AMP_Support' )
 			 * @param array $extra_data Array of data about the site and the post.
 			 */
 			$extra_data = apply_filters( 'jp_carousel_add_data_to_container', $extra_data );
+
 			foreach ( (array) $extra_data as $data_key => $data_values ) {
-				$html = str_replace( '<div ', '<div ' . esc_attr( $data_key ) . "='" . json_encode( $data_values ) . "' ", $html );
-				$html = str_replace( '<ul class="wp-block-gallery', '<ul ' . esc_attr( $data_key ) . "='" . json_encode( $data_values ) . "' class=\"wp-block-gallery", $html );
+				// Let's grab all containers from the HTML.
+				$dom_doc = new DOMDocument();
+
+				/*
+				 * The @ is not enough to suppress errors when dealing with libxml,
+				 * we have to tell it directly how we want to handle errors.
+				 */
+				libxml_use_internal_errors( true );
+				@$dom_doc->loadHTML( $html ); // phpcs:ignore WordPress.PHP.NoSilencedErrors.Discouraged
+				libxml_use_internal_errors( false );
+
+				// Let's look for lists and divs.
+				$ul_tags  = $dom_doc->getElementsByTagName( 'ul' );
+				$div_tags = $dom_doc->getElementsByTagName( 'div' );
+
+				// Loop through each ul, and add the data to it if it is a gallery block.
+				foreach ( $ul_tags as $ul_tag ) {
+					if ( false !== strpos( $ul_tag->getAttribute( 'class' ), 'wp-block-gallery' ) ) {
+						$ul_tag->setAttribute(
+							esc_attr( $data_key ),
+							wp_json_encode( $data_values )
+						);
+					}
+				}
+
+				/*
+				 * Loop through each div and add the data, only when it's a gallery block div.
+				 * We want to avoid adding data to divs like wp-block-columns.
+				 * We do however want data on divs like wp-block-jetpack-tiled-gallery.
+				 */
+				foreach ( $div_tags as $div_tag ) {
+					if (
+						false === strpos( $div_tag->getAttribute( 'class' ), 'wp-block-' )
+						|| false !== strpos( $div_tag->getAttribute( 'class' ), 'gallery' )
+					) {
+						$div_tag->setAttribute(
+							esc_attr( $data_key ),
+							wp_json_encode( $data_values )
+						);
+					}
+				}
+
+				// Save our updated HTML.
+				$html = $dom_doc->saveHTML();
 			}
 		}