Add support for comments

amp.php

@@ -71,6 +71,7 @@ function amp_after_setup_theme() {
 	}
 
 	add_action( 'init', 'amp_init' );
+	add_action( 'rest_api_init', 'amp_rest_init' );
 	add_action( 'admin_init', 'AMP_Options_Manager::register_settings' );
 	add_filter( 'amp_post_template_analytics', 'amp_add_custom_analytics' );
 	add_action( 'wp_loaded', 'amp_post_meta_box' );
@@ -109,6 +110,16 @@ function amp_init() {
 	}
 }
 
+/**
+ * Init AMP Rest endpoints.
+ *
+ * @since 0.1
+ */
+function amp_rest_init() {
+	require_once AMP__DIR__ . '/includes/amp-rest-functions.php';
+	amp_register_endpoints();
+}
+
 // Make sure the `amp` query var has an explicit value.
 // Avoids issues when filtering the deprecated `query_string` hook.
 function amp_force_query_var_value( $query_vars ) {

includes/amp-rest-functions.php

@@ -0,0 +1,69 @@
+<?php
+/**
+ * AMP Rest Functions
+ *
+ * @package AMP
+ */
+
+/**
+ * Register the comments REST endpoint.
+ *
+ * @since 0.7
+ */
+function amp_register_endpoints() {
+
+	register_rest_route( 'amp/v1', '/comments/(?P<id>\d+)', array(
+		'methods'  => 'GET',
+		'callback' => 'amp_get_comments',
+	) );
+
+}
+
+/**
+ * Get comments for the Post and Parent
+ *
+ * @since 0.7
+ * @param WP_REST_Request $request The REST request.
+ *
+ * @return array The array of comments.
+ */
+function amp_get_comments( $request ) {
+
+	$id     = $request->get_param( 'id' );
+	$return = array(
+		'items' => array(
+			'comment' => amp_get_comments_recursive( $id, 0 ),
+		),
+	);
+
+	return $return;
+}
+
+/**
+ * Recursively get comments for the Post and Parent
+ *
+ * @since 0.7
+ * @param int $id The post ID.
+ * @param int $parent The comment parent.
+ *
+ * @return array The array of comments.
+ */
+function amp_get_comments_recursive( $id, $parent ) {
+
+	$comments = get_comments( array(
+		'post_ID' => $id,
+		'parent'  => $parent,
+		'order'   => 'ASC',
+	) );
+
+	$return = array();
+	foreach ( $comments as $comment ) {
+		$GLOBALS['comment']    = $comment; // WPCS: override ok.
+		$comment->comment_date = get_comment_date();
+		$comment->comment_time = get_comment_time();
+		$comment->comment      = amp_get_comments_recursive( $id, $comment->comment_ID );
+		$return[]              = $comment;
+	}
+
+	return $return;
+}

includes/class-amp-autoloader.php

@@ -30,6 +30,7 @@ class AMP_Autoloader {
 	 */
 	private static $_classmap = array(
 		'AMP_Theme_Support'                           => 'includes/class-amp-theme-support',
+		'AMP_Comment_Walker'                          => 'includes/class-amp-comment-walker',
 		'AMP_Template_Customizer'                     => 'includes/admin/class-amp-customizer',
 		'AMP_Post_Meta_Box'                           => 'includes/admin/class-amp-post-meta-box',
 		'AMP_Post_Type_Support'                       => 'includes/class-amp-post-type-support',
@@ -64,6 +65,8 @@ class AMP_Autoloader {
 		'AMP_Blacklist_Sanitizer'                     => 'includes/sanitizers/class-amp-blacklist-sanitizer',
 		'AMP_Iframe_Sanitizer'                        => 'includes/sanitizers/class-amp-iframe-sanitizer',
 		'AMP_Img_Sanitizer'                           => 'includes/sanitizers/class-amp-img-sanitizer',
+		'AMP_Form_Sanitizer'                          => 'includes/sanitizers/class-amp-form-sanitizer',
+		'AMP_Comments_Sanitizer'                      => 'includes/sanitizers/class-amp-comments-sanitizer',
 		'AMP_Playbuzz_Sanitizer'                      => 'includes/sanitizers/class-amp-playbuzz-sanitizer',
 		'AMP_Style_Sanitizer'                         => 'includes/sanitizers/class-amp-style-sanitizer',
 		'AMP_Tag_And_Attribute_Sanitizer'             => 'includes/sanitizers/class-amp-tag-and-attribute-sanitizer',

includes/class-amp-comment-walker.php

@@ -0,0 +1,107 @@
+<?php
+/**
+ * Class AMP_Comment_Walker
+ *
+ * @package AMP
+ */
+
+/**
+ * Class AMP_Comment_Walker
+ *
+ * Walker to wrap comments in mustache tags for amp-template.
+ */
+class AMP_Comment_Walker extends Walker_Comment {
+
+	/**
+	 * The original comments arguments.
+	 *
+	 * @since 0.7
+	 * @var array
+	 */
+	public $args;
+
+	/**
+	 * Starts the element output.
+	 *
+	 * @since 2.7.0
+	 *
+	 * @see Walker::start_el()
+	 * @see wp_list_comments()
+	 * @global int        $comment_depth
+	 * @global WP_Comment $comment
+	 *
+	 * @param string     $output  Used to append additional content. Passed by reference.
+	 * @param WP_Comment $comment Comment data object.
+	 * @param int        $depth   Optional. Depth of the current comment in reference to parents. Default 0.
+	 * @param array      $args    Optional. An array of arguments. Default empty array.
+	 * @param int        $id      Optional. ID of the current comment. Default 0 (unused).
+	 */
+	public function start_el( &$output, $comment, $depth = 0, $args = array(), $id = 0 ) {
+		$output .= '{{#comment}}';
+		parent::start_el( $output, $comment, $depth, $args, $id );
+	}
+	/**
+	 * Ends the element output, if needed.
+	 *
+	 * @since 2.7.0
+	 *
+	 * @see Walker::end_el()
+	 * @see wp_list_comments()
+	 *
+	 * @param string     $output  Used to append additional content. Passed by reference.
+	 * @param WP_Comment $comment The current comment object. Default current comment.
+	 * @param int        $depth   Optional. Depth of the current comment. Default 0.
+	 * @param array      $args    Optional. An array of arguments. Default empty array.
+	 */
+	public function end_el( &$output, $comment, $depth = 0, $args = array() ) {
+		if ( ! empty( $args['end-callback'] ) ) {
+			ob_start();
+			call_user_func( $args['end-callback'], $comment, $args, $depth );
+			$output .= ob_get_clean();
+		} else {
+			if ( 'div' === $args['style'] ) {
+				$output .= "</div><!-- #comment-## -->\n";
+			} else {
+				$output .= "</li><!-- #comment-## -->\n";
+			}
+		}
+		$output .= '{{/comment}}';
+	}
+
+	/**
+	 * Output amp-list template code and place holder for comments.
+	 *
+	 * @see Walker::paged_walk()
+	 * @param array $elements List of comment Elements.
+	 * @param int   $max_depth The maximum hierarchical depth.
+	 * @param int   $page_num The specific page number, beginning with 1.
+	 * @param int   $per_page Per page counter.
+	 *
+	 * @return string XHTML of the specified page of elements.
+	 */
+	public function paged_walk( $elements, $max_depth, $page_num, $per_page ) {
+		if ( empty( $elements ) || $max_depth < - 1 ) {
+			return '';
+		}
+
+		$args = array_slice( func_get_args(), 4 );
+		if ( ! empty( $args[0]['comments_template_placeholder'] ) ) {
+			return $args[0]['comments_template_placeholder'];
+		}
+
+		$template  = '<comments-template>';
+		$template .= parent::paged_walk( $elements, $max_depth, $page_num, $per_page, $args[0] );
+		$template .= '</comments-template>';
+
+		$url = get_rest_url( get_current_blog_id(), 'amp/v1/comments/' . get_the_ID() );
+		if ( strpos( $url, 'http:' ) === 0 ) {
+			$url = substr( $url, 5 );
+		}
+		// @todo Identify arguments and make filterable/settable.
+		$template .= '<amp-list src="' . esc_attr( $url ) . '" height="400" single-item="true" layout="fixed-height">';
+		$template .= '<template type="amp-mustache"></template>';
+		$template .= '</amp-list>';
+
+		return $template;
+	}
+}

includes/class-amp-theme-support.php

@@ -26,6 +26,13 @@ class AMP_Theme_Support {
 	 */
 	const CUSTOM_STYLES_PLACEHOLDER = '/* AMP:CUSTOM_STYLES_PLACEHOLDER */';
 
+	/**
+	 * Replaced with the comments template.
+	 *
+	 * @var string
+	 */
+	const COMMENTS_TEMPLATE_PLACEHOLDER = '/* AMP:COMMENTS_TEMPLATE_PLACEHOLDER */';
+
 	/**
 	 * AMP Scripts.
 	 *
@@ -189,6 +196,8 @@ public static function register_hooks() {
 
 		add_filter( 'the_content', array( __CLASS__, 'filter_the_content' ), PHP_INT_MAX );
 
+		// Add Comments hooks.
+		add_filter( 'wp_list_comments_args', array( __CLASS__, 'add_amp_comments_template' ), PHP_INT_MAX );
 		// @todo Add character conversion.
 	}
 
@@ -301,6 +310,100 @@ public static function add_amp_component_scripts() {
 		echo self::COMPONENT_SCRIPTS_PLACEHOLDER; // phpcs:ignore WordPress.Security.EscapeOutput, WordPress.XSS.EscapeOutput
 	}
 
+	/**
+	 * Add the comments template placeholder marker
+	 *
+	 * @param array $args the args for the comments list..
+	 * @return array Args to return.
+	 */
+	public static function add_amp_comments_template( $args ) {
+		if ( ! isset( $args['amp_comments'] ) ) {
+			$amp_walker           = new AMP_Comment_Walker();
+			$args['walker']       = $amp_walker;
+			$args['amp_comments'] = true;
+			$template             = self::get_comments_template( $args );
+			wp_cache_add( 'amp_comments_template', $template, 'amp' );
+			$args['comments_template_placeholder'] = self::COMMENTS_TEMPLATE_PLACEHOLDER;
+		}
+
+		return $args;
+	}
+
+	/**
+	 * Generate a threaded mustache template based on the themes settings.
+	 *
+	 * @param array $args the args for the comments list.
+	 * @return string HTML mustache template.
+	 */
+	public static function get_comments_template( $args ) {
+
+		$_comment = array(
+			'comment_ID'           => '{{comment_ID}}',
+			'comment_post_ID'      => get_the_ID(),
+			'comment_author'       => '{{comment_author}}',
+			'comment_author_email' => '{{comment_author_email}}',
+			'comment_author_url'   => '{{comment_author_url}}',
+			'comment_author_IP'    => '{{comment_author_IP}}',
+			'comment_date'         => '{{comment_date}}',
+			'comment_date_gmt'     => '{{comment_date_gmt}}',
+			'comment_content'      => '{{comment_content}}',
+			'comment_karma'        => '{{comment_karma}}',
+			'comment_approved'     => '{{comment_approved}}',
+			'comment_agent'        => '{{comment_agent}}',
+			'comment_type'         => '{{comment_type}}',
+			'comment_parent'       => '',
+			'user_id'              => '{{user_id}}',
+		);
+
+		$comments = array();
+		$depth    = ( $args['max_depth'] ? $args['max_depth'] : 5 );
+		for ( $i = 0; $i < $depth; $i ++ ) {
+			$comment = new stdClass();
+			foreach ( $_comment as $key => $value ) {
+				if ( 'comment_ID' === $key ) {
+					$value = $i + 1;
+				}
+				if ( 'comment_parent' === $key && $i > 0 ) {
+					$value = $i;
+				}
+				$comment->{$key} = $value;
+			}
+			$comments[] = $comment;
+		}
+
+		$args['echo']     = false;
+		$args['amp_pass'] = true;
+		if ( empty( $args['walker'] ) ) {
+			$args['walker'] = new AMP_Comment_Walker();
+		}
+
+		// Filter dynamic data with musatche variable strings.
+		// @todo add additional filters for dynamic data like "get_comment_author_link", "get_comment_author_IP" etc...
+		add_filter( 'get_comment_date', array( __CLASS__, 'get_comment_date_template_string' ) );
+		add_filter( 'get_comment_time', array( __CLASS__, 'get_comment_time_template_string' ) );
+
+		return wp_list_comments( $args, $comments );
+
+	}
+
+	/**
+	 * Get somment date string for template.
+	 *
+	 * @return string Mustache template string.
+	 */
+	public static function get_comment_date_template_string() {
+		return '{{comment_date}}';
+	}
+
+	/**
+	 * Get somment time string for template.
+	 *
+	 * @return string Mustache template string.
+	 */
+	public static function get_comment_time_template_string() {
+		return '{{comment_time}}';
+	}
+
 	/**
 	 * Get canonical URL for current request.
 	 *
@@ -525,7 +628,25 @@ public static function finish_output_buffering( $output ) {
 			1
 		);
 
+		// Inject comments template.
+		$output   = preg_replace(
+			'#' . preg_quote( self::COMMENTS_TEMPLATE_PLACEHOLDER, '#' ) . '#',
+			$args = wp_cache_get( 'amp_comments_template', 'amp' ),
+			$output,
+			1
+		);
+
+		$dom = AMP_DOM_Utils::get_dom( $output );
+		// Sanitize forms in the document.
+		$sanitizer = new AMP_Form_Sanitizer( $dom );
+		$sanitizer->sanitize();
+
+		$sanitizer = new AMP_Comments_Sanitizer( $dom );
+		$sanitizer->sanitize();
+
 		// @todo Add more validation checking and potentially the whitelist sanitizer.
+		$output = $dom->saveHTML();
+
 		return $output;
 	}
 }