Add support for comments

amp.php

@@ -88,6 +88,7 @@ function amp_after_setup_theme() {
 	}
 
 	add_action( 'init', 'amp_init' );
+	add_action( 'rest_api_init', 'amp_rest_init' );
 	add_action( 'widgets_init', 'AMP_Theme_Support::register_widgets' );
 	add_action( 'admin_init', 'AMP_Options_Manager::register_settings' );
 	add_filter( 'amp_post_template_analytics', 'amp_add_custom_analytics' );
@@ -125,6 +126,18 @@ function amp_init() {
 	if ( class_exists( 'Jetpack' ) && ! ( defined( 'IS_WPCOM' ) && IS_WPCOM ) ) {
 		require_once( AMP__DIR__ . '/jetpack-helper.php' );
 	}
+
+	amp_hook_comments_maybe();
+}
+
+/**
+ * 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.
@@ -361,3 +374,64 @@ function amp_redirect_old_slug_to_new_url( $link ) {
 
 	return $link;
 }
+
+/**
+ * Hook into a comment submission if an AMP xhr post request.
+ */
+function amp_hook_comments_maybe() {
+
+	$method        = filter_input( INPUT_SERVER, 'REQUEST_METHOD', FILTER_SANITIZE_STRING );
+	$is_amp_submit = filter_input( INPUT_GET, '__amp_source_origin', FILTER_VALIDATE_URL );
+
+	if ( 'post' !== strtolower( $method ) || is_null( $is_amp_submit ) ) {
+		return;
+	}
+
+	// Add amp comment hooks.
+	add_filter( 'comment_post_redirect', 'amp_comment_post_redirect', PHP_INT_MAX, 2 );
+	add_filter( 'wp_die_handler', 'amp_set_comment_submit_die_handler' );
+
+	// Send amp header.
+	header( 'AMP-Access-Control-Allow-Source-Origin: ' . $is_amp_submit, true );
+
+}
+
+/**
+ * Set the die handler on comment submit to output the error in json and send AMP headers.
+ */
+function amp_set_comment_submit_die_handler() {
+	return 'amp_send_error_json';
+}
+
+/**
+ * Send error creating message.
+ *
+ * @param string $message The error message to send.
+ */
+function amp_send_error_json( $message ) {
+	header( 'HTTP/1.1 400 BAD REQUEST' );
+	wp_send_json( array( 'error' => strip_tags( $message, 'strong' ) ) );
+}
+
+/**
+ * Redirect after comment submission.
+ *
+ * @param string     $location The location to redirect to.
+ * @param WP_Comment $comment The comment that was posted.
+ * @return string The location URL or void if send json.
+ */
+function amp_comment_post_redirect( $location, $comment ) {
+	$is_amp_submit = filter_input( INPUT_GET, '__amp_source_origin', FILTER_VALIDATE_URL );
+	if ( is_null( $is_amp_submit ) ) {
+		return $location;
+	}
+
+	// AMP-Redirect only works if https. If not, we simply render the success.
+	if ( is_ssl() ) {
+		$location = strtok( $location, '#' );
+		header( 'AMP-Redirect-To: ' . $location );
+		header( 'Access-Control-Expose-Headers: AMP-Redirect-To', false );
+	}
+	$comment->comment_link = get_comment_link( $comment->comment_ID );
+	wp_send_json( $comment );
+}

includes/amp-helper-functions.php

@@ -222,6 +222,8 @@ function amp_get_content_sanitizers( $post = null ) {
 			'AMP_Video_Sanitizer'             => array(),
 			'AMP_Audio_Sanitizer'             => array(),
 			'AMP_Playbuzz_Sanitizer'          => array(),
+			'AMP_Form_Sanitizer'              => array(),
+			'AMP_Comments_Sanitizer'          => array(),
 			'AMP_Iframe_Sanitizer'            => array(
 				'add_placeholder' => true,
 			),

includes/amp-rest-functions.php

@@ -0,0 +1,71 @@
+<?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' );
+	$comments = get_comments( array(
+		'post_ID' => $id,
+		'order'   => 'ASC',
+	) );
+	$return   = array(
+		'items' => array(
+			'comment' => amp_get_comments_recursive( 0, $comments ),
+		),
+	);
+
+	return $return;
+}
+
+/**
+ * Recursively get comments for the Post and Parent
+ *
+ * @since 0.7
+ * @param int   $parent The comment parent.
+ * @param array $comments The list of comments.
+ *
+ * @return array The array of comments.
+ */
+function amp_get_comments_recursive( $parent, $comments ) {
+
+	$return = array();
+	foreach ( $comments as $comment ) {
+		if ( (int) $parent !== (int) $comment->comment_parent ) {
+			continue;
+		}
+		$GLOBALS['comment']          = $comment; // WPCS: override ok.
+		$comment->comment_date       = get_comment_date();
+		$comment->comment_time       = get_comment_time();
+		$comment->comment_avatar_url = get_avatar_url( $comment->comment_author_email );
+		$comment->comment            = amp_get_comments_recursive( $comment->comment_ID, $comments );
+		$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_WP_Styles'                               => 'includes/class-amp-wp-styles',
 		'AMP_Template_Customizer'                     => 'includes/admin/class-amp-customizer',
 		'AMP_Post_Meta_Box'                           => 'includes/admin/class-amp-post-meta-box',
@@ -65,6 +66,8 @@ 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 +1,105 @@
+<?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 );
+
+		$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.
+		$output  = '<amp-list src="' . esc_attr( $url ) . '" height="200" width="auto" single-item="true" layout="flex-item">';
+		$output .= '<template type="amp-mustache"></template>';
+		$output .= '<div overflow role="button" aria-label="' . esc_attr__( 'Show more', 'amp' ) . '" class="list-overflow ampstart-btn caps">' . esc_html__( 'Show more', 'amp' ) . '</div>';
+		$output .= '<div fallback class="amp-fallback amp-comments-notice amp-error"><p>' . esc_html__( 'Could not load comments.', 'amp' ) . '</p></div>';
+		$output .= '</amp-list>';
+		$output .= '<comment-template>';
+		$output .= parent::paged_walk( $elements, $max_depth, $page_num, $per_page, $args[0] );
+		$output .= '</comment-template>';
+
+		return $output;
+	}
+}