Ensure required AMP component scripts are printed when content is ser…

…ved in non-AMP response (dirty AMP)

includes/admin/class-amp-editor-blocks.php

@@ -11,13 +11,39 @@
  */
 class AMP_Editor_Blocks {
 
+	/**
+	 * List of AMP scripts that need to be printed when AMP components are used in non-AMP document context ("dirty AMP").
+	 *
+	 * @var array
+	 */
+	public $content_required_amp_scripts = array();
+
+	/**
+	 * AMP components that have blocks.
+	 *
+	 * @var array
+	 */
+	public $amp_blocks = array(
+		'amp-mathml',
+		'amp-o2-player',
+		'amp-ooyala-player',
+		'amp-reach-player',
+		'amp-springboard-player',
+		'amp-jwplayer',
+		'amp-brid-player',
+		'amp-ima-video',
+		'amp-fit-text',
+	);
+
 	/**
 	 * Init.
 	 */
 	public function init() {
 		if ( function_exists( 'gutenberg_init' ) ) {
 			add_action( 'enqueue_block_editor_assets', array( $this, 'enqueue_block_editor_assets' ) );
 			add_filter( 'wp_kses_allowed_html', array( $this, 'whitelist_block_atts_in_wp_kses_allowed_html' ), 10, 2 );
+			add_filter( 'the_content', array( $this, 'tally_content_requiring_amp_scripts' ) );
+			add_action( 'wp_print_footer_scripts', array( $this, 'print_dirty_amp_scripts' ) );
 		}
 	}
 
@@ -40,19 +66,7 @@ public function whitelist_block_atts_in_wp_kses_allowed_html( $tags, $context )
 			$tag['data-amp-noloading'] = true;
 		}
 
-		$amp_blocks = array(
-			'amp-mathml',
-			'amp-o2-player',
-			'amp-ooyala-player',
-			'amp-reach-player',
-			'amp-springboard-player',
-			'amp-jwplayer',
-			'amp-brid-player',
-			'amp-ima-video',
-			'amp-fit-text',
-		);
-
-		foreach ( $amp_blocks as $amp_block ) {
+		foreach ( $this->amp_blocks as $amp_block ) {
 			if ( ! isset( $tags[ $amp_block ] ) ) {
 				$tags[ $amp_block ] = array();
 			}
@@ -117,4 +131,32 @@ public function enqueue_block_editor_assets() {
 
 		wp_add_inline_script( 'amp-editor-blocks', sprintf( 'ampEditorBlocks.boot();' ) );
 	}
+
+	/**
+	 * Tally the AMP component scripts that are needed in a dirty AMP document.
+	 *
+	 * @param string $content Content.
+	 * @return string Content (unmodified).
+	 */
+	public function tally_content_requiring_amp_scripts( $content ) {
+		if ( ! is_amp_endpoint() ) {
+			$pattern = sprintf( '/<(%s)\b.*?>/s', join( '|', $this->amp_blocks ) );
+			if ( preg_match_all( $pattern, $content, $matches ) ) {
+				$this->content_required_amp_scripts = array_merge(
+					$this->content_required_amp_scripts,
+					$matches[1]
+				);
+			}
+		}
+		return $content;
+	}
+
+	/**
+	 * Print AMP scripts required for AMP components used in a non-AMP document (dirty AMP).
+	 */
+	public function print_dirty_amp_scripts() {
+		if ( ! is_amp_endpoint() && ! empty( $this->content_required_amp_scripts ) ) {
+			wp_scripts()->do_items( $this->content_required_amp_scripts );
+		}
+	}
 }