Add capability to generate AMP-only content (AMP-as-Canonical)

amp.php

@@ -20,6 +20,9 @@
 require_once( AMP__DIR__ . '/includes/admin/functions.php' );
 require_once( AMP__DIR__ . '/includes/settings/class-amp-customizer-settings.php' );
 require_once( AMP__DIR__ . '/includes/settings/class-amp-customizer-design-settings.php' );
+require_once( AMP__DIR__ . '/includes/utils/class-amp-dom-utils.php');
+require_once( AMP__DIR__ . '/option.php' );
+require_once(AMP__DIR__ . '/post-processing/class-amp-sanitize-tweentyseventeen-theme-plain.php');
 
 register_activation_hook( __FILE__, 'amp_activate' );
 function amp_activate() {
@@ -48,15 +51,20 @@ function amp_init() {
 	if ( false === apply_filters( 'amp_is_enabled', true ) ) {
 		return;
 	}
+	error_log("AMP INIT");
 
 	define( 'AMP_QUERY_VAR', apply_filters( 'amp_query_var', 'amp' ) );
 
 	do_action( 'amp_init' );
 
 	load_plugin_textdomain( 'amp', false, plugin_basename( AMP__DIR__ ) . '/languages' );
 
-	add_rewrite_endpoint( AMP_QUERY_VAR, EP_PERMALINK );
-	add_post_type_support( 'post', AMP_QUERY_VAR );
+	// If the amp_canonical option has not been setup, or the current
+	// theme does not provide AMP support, then follow the "paired" approach
+	if ( ! get_option('amp_canonical') || ! get_theme_support('amp')) {
+		add_rewrite_endpoint( AMP_QUERY_VAR, EP_PERMALINK );
+		add_post_type_support( 'post', AMP_QUERY_VAR );
+	}
 
 	add_filter( 'request', 'amp_force_query_var_value' );
 	add_action( 'wp', 'amp_maybe_add_actions' );
@@ -67,6 +75,7 @@ function amp_init() {
 	if ( class_exists( 'Jetpack' ) && ! ( defined( 'IS_WPCOM' ) && IS_WPCOM ) ) {
 		require_once( AMP__DIR__ . '/jetpack-helper.php' );
 	}
+
 }
 
 // Make sure the `amp` query var has an explicit value.
@@ -79,28 +88,30 @@ function amp_force_query_var_value( $query_vars ) {
 }
 
 function amp_maybe_add_actions() {
-	if ( ! is_singular() || is_feed() ) {
+	if ( is_feed() || (!get_option('amp_canonical') && !is_singular())) {
 		return;
 	}
 
 	$is_amp_endpoint = is_amp_endpoint();
-
-	// Cannot use `get_queried_object` before canonical redirect; see https://core.trac.wordpress.org/ticket/35344
-	global $wp_query;
-	$post = $wp_query->post;
-
-	$supports = post_supports_amp( $post );
-
-	if ( ! $supports ) {
-		if ( $is_amp_endpoint ) {
-			wp_safe_redirect( get_permalink( $post->ID ) );
-			exit;
+	$supports = true;
+	if (is_singular()) {
+		// Cannot use `get_queried_object` before canonical redirect; see https://core.trac.wordpress.org/ticket/35344
+		global $wp_query;
+		$post = $wp_query->post;
+		$supports = post_supports_amp($post);
+		if ( ! $supports ) {
+			if ( $is_amp_endpoint ) {
+				wp_safe_redirect( get_permalink( $post->ID ) );
+				exit;
+			}
+			return;
 		}
-		return;
 	}
 
 	if ( $is_amp_endpoint ) {
 		amp_prepare_render();
+	} else if( get_option('amp_canonical') && $supports && get_theme_support('amp') && is_singular() ) {
+		amp_add_canonical_actions();
 	} else {
 		amp_add_frontend_actions();
 	}
@@ -144,6 +155,65 @@ function amp_render_post( $post_id ) {
 	$template->load();
 }
 
+function amp_add_canonical_actions() {
+	// Load AMP canonical actions
+	require_once( AMP__DIR__ . '/includes/amp-canonical-actions.php');
+	// Load high-priority filters for canonical AMP
+	require_once( AMP__DIR__ . '/includes/amp-canonical-filters.php');
+	// Template redirect to postprocessing actions
+	add_action( 'template_redirect', 'amp_maybe_init_postprocess_html' );
+}
+
+function amp_maybe_init_postprocess_html() {
+	ob_start( 'amp_canonical_postprocess_html' );
+}
+
+/**
+ * Convert generated $html (plain 2017 Theme) to valid-AMP format
+ */
+function amp_canonical_postprocess_html( $html ) {
+
+	$dom = new DOMDocument();
+	libxml_use_internal_errors(true);
+	$dom->loadHTML($html);
+	libxml_use_internal_errors(false);
+
+	// TODO (@amedina): Define how specific theme sanitations
+	// will be executed; user can select a specific one or a
+	// generic one could be executed
+
+	// Add amp attribute to html tag
+	AMP_Sanitize_TweentySeventeen_Theme::add_amp_attr($dom);
+	// Eliminate 3p JS
+	AMP_Sanitize_TweentySeventeen_Theme::eliminate_3p_js($dom);
+	// Eliminate external stylesheets
+	AMP_Sanitize_TweentySeventeen_Theme::eliminate_ext_css($dom);
+	// Eliminate sidebars
+	//AMP_Sanitize_TweentySeventeen_Theme::eliminate_sidebars($dom);
+	// Eliminate entry footers
+	AMP_Sanitize_TweentySeventeen_Theme::eliminate_entry_footers($dom);
+	// Eliminate overall footer
+	AMP_Sanitize_TweentySeventeen_Theme::eliminate_overall_footer($dom);
+	// Eliminate post navigation
+	//AMP_Sanitize_TweentySeventeen_Theme::eliminate_post_navigation($dom);
+	// Eliminate comments section
+	AMP_Sanitize_TweentySeventeen_Theme::eliminate_comments_section($dom);
+	// Set meta viewport
+	AMP_Sanitize_TweentySeventeen_Theme::set_meta_viewport($dom);
+	// Eliminate non-amp-custom Stylesheets
+	AMP_Sanitize_TweentySeventeen_Theme::eliminate_non_amp_custom_styles($dom);
+	// Inline theme CSS
+	AMP_Sanitize_TweentySeventeen_Theme::inline_theme_css($dom);
+	// AMP Custom-header img
+	AMP_Sanitize_TweentySeventeen_Theme::amp_custom_header_img($dom);
+	// Remove styled SVGs
+	AMP_Sanitize_TweentySeventeen_Theme::remove_styled_svgs($dom);
+	// Save new HTML contents
+	$amp_html = $dom->saveHTML();
+
+	return $amp_html;
+}
+
 /**
  * Bootstraps the AMP customizer.
  *

includes/amp-canonical-actions.php

@@ -0,0 +1,126 @@
+<?php
+require_once( AMP__DIR__ . '/includes/utils/class-amp-dom-utils.php');
+require_once( AMP__DIR__ . '/includes/utils/class-amp-html-utils.php');
+require_once( AMP__DIR__ . '/includes/utils/class-amp-string-utils.php');
+
+require_once( AMP__DIR__ . '/includes/class-amp-content.php');
+
+require_once( AMP__DIR__ . '/includes/sanitizers/class-amp-blacklist-sanitizer.php');
+require_once( AMP__DIR__ . '/includes/sanitizers/class-amp-img-sanitizer.php');
+require_once( AMP__DIR__ . '/includes/sanitizers/class-amp-video-sanitizer.php');
+require_once( AMP__DIR__ . '/includes/sanitizers/class-amp-iframe-sanitizer.php');
+require_once( AMP__DIR__ . '/includes/sanitizers/class-amp-audio-sanitizer.php');
+require_once( AMP__DIR__ . '/includes/sanitizers/class-amp-style-sanitizer.php');
+
+require_once( AMP__DIR__ . '/includes/embeds/class-amp-twitter-embed.php');
+require_once( AMP__DIR__ . '/includes/embeds/class-amp-youtube-embed.php');
+require_once( AMP__DIR__ . '/includes/embeds/class-amp-gallery-embed.php');
+require_once( AMP__DIR__ . '/includes/embeds/class-amp-instagram-embed.php');
+require_once( AMP__DIR__ . '/includes/embeds/class-amp-vine-embed.php');
+require_once( AMP__DIR__ . '/includes/embeds/class-amp-facebook-embed.php');
+require_once( AMP__DIR__ . '/includes/embeds/class-amp-dailymotion-embed.php');
+require_once( AMP__DIR__ . '/includes/embeds/class-amp-soundcloud-embed.php');
+
+function amp_canonical_retrieve_content() {
+
+	$post = get_post();
+
+	$content_max_width = 1200;
+
+	if ( isset( $GLOBALS['content_width']) && $GLOBALS['content_width'] > 0 ) {
+		$content_max_width = $GLOBALS['content_width'];
+	}
+
+	$amp_content = new AMP_Content(
+		$post->post_content,
+		array(
+			'AMP_Twitter_Embed_Handler' => array(),
+			'AMP_YouTube_Embed_Handler' => array(),
+			'AMP_DailyMotion_Embed_Handler' => array(),
+			'AMP_SoundCloud_Embed_Handler' => array(),
+			'AMP_Instagram_Embed_Handler' => array(),
+			'AMP_Vine_Embed_Handler' => array(),
+			'AMP_Facebook_Embed_Handler' => array(),
+			'AMP_Gallery_Embed_Handler' => array(),
+		),
+		array(
+			'AMP_Style_Sanitizer' => array(),
+			'AMP_Blacklist_Sanitizer' => array(),
+			'AMP_Img_Sanitizer' => array(),
+			'AMP_Video_Sanitizer' => array(),
+			'AMP_Audio_Sanitizer' => array(),
+			'AMP_Iframe_Sanitizer' => array(
+				'add_placeholder' => true,
+            ),
+		),
+		array(
+			'content_max_width' => $content_max_width,
+		)
+	);
+
+	return $amp_content;
+
+}
+
+// Generate the AMP post content early on
+// Runs the filters for the_content, but skips our filters below
+$GLOBALS['amp_content'] = amp_canonical_retrieve_content();
+
+// The filter for the_content hook was already invoked,
+// attempt to remove all filters
+remove_all_filters('the_content');
+
+add_action( 'wp_head', 'amp_canonical_add_scripts' );
+add_action( 'wp_head', 'amp_canonical_add_boilerplate_css' );
+add_action( 'wp_footer', 'amp_deregister_scripts' );
+
+// Add the filter that replaces the content, and ensure
+// that no content filters run afterwards
+add_filter( 'the_content', 'amp_the_content_filter', PHP_INT_MAX);
+function amp_the_content_filter($content) {
+	if (isset($GLOBALS['amp_content'])) {
+		return $GLOBALS['amp_content']->get_amp_content();
+	} else {
+		return $content;
+	}
+}
+
+function amp_deregister_scripts() {
+	wp_deregister_script( 'wp_embed');
+}
+
+function amp_canonical_add_boilerplate_css() {
+	?>
+	<style amp-boilerplate>body{-webkit-animation:-amp-start 8s steps(1,end) 0s 1 normal both;-moz-animation:-amp-start 8s steps(1,end) 0s 1 normal both;-ms-animation:-amp-start 8s steps(1,end) 0s 1 normal both;animation:-amp-start 8s steps(1,end) 0s 1 normal both}@-webkit-keyframes -amp-start{from{visibility:hidden}to{visibility:visible}}@-moz-keyframes -amp-start{from{visibility:hidden}to{visibility:visible}}@-ms-keyframes -amp-start{from{visibility:hidden}to{visibility:visible}}@-o-keyframes -amp-start{from{visibility:hidden}to{visibility:visible}}@keyframes -amp-start{from{visibility:hidden}to{visibility:visible}}</style><noscript><style amp-boilerplate>body{-webkit-animation:none;-moz-animation:none;-ms-animation:none;animation:none}</style></noscript>
+	<?php
+}
+
+function amp_canonical_add_scripts() {
+
+	$amp_runtime_script = 'https://cdn.ampproject.org/v0.js';
+
+	// Always include AMP form & analytics, as almost every template includes
+	// a search form and is tracking page views
+	$scripts = array_merge(
+		array('amp-form' => 'https://cdn.ampproject.org/v0/amp-form-0.1.js'),
+		array('amp-analytics' => 'https://cdn.ampproject.org/v0/amp-analytics-0.1.js'),
+		$GLOBALS['amp_content']->get_amp_scripts()
+	);
+
+	foreach ( $scripts as $element => $script) : ?>
+		<script custom-element="<?php echo esc_attr( $element ); ?>" src="<?php echo esc_url( $script ); ?>" async></script>
+	<?php endforeach; ?>
+	<script src="<?php echo esc_url( $amp_runtime_script ); ?>" async></script>
+	<?php
+}
+
+// TODO (@amedina) Get the canonical URL [Check!]
+if (!is_singular()) {
+	add_action( 'wp_head', 'amp_post_template_add_canonical');
+}
+function amp_post_template_add_canonical() {
+    error_log("CANONICAL: Adding canonical link")
+	?>
+    <link rel="canonical" href="<?php echo esc_url( get_site_url() ); ?>" />
+	<?php
+}

includes/amp-canonical-filters.php

@@ -0,0 +1,15 @@
+<?php
+
+// before Jetpack ever gets loaded, we need to remove a
+// link rel prefetch for canonical AMP support
+// TODO[@amedina] These will be allowed by the validator in the future
+// TODO[@amedina]  remove as soon as it works
+
+function amp_canonical_disable_jetpack_dns_fetch() {
+
+	if ( class_exists( 'Jetpack') ) {
+		remove_action( 'wp_head', array( 'Jetpack', 'dns_prefetch' ) );
+	}
+}
+// Hook action early on so we can unhook Jetpack
+add_action( 'wp_head', 'amp_canonical_disable_jetpack_dns_fetch', 0);

includes/amp-helper-functions.php

@@ -19,7 +19,7 @@ function amp_get_permalink( $post_id ) {
 
 function post_supports_amp( $post ) {
 	// Because `add_rewrite_endpoint` doesn't let us target specific post_types :(
-	if ( ! post_type_supports( $post->post_type, AMP_QUERY_VAR ) ) {
+	if ( ! get_option( 'amp_canonical' ) && ! post_type_supports( $post->post_type, AMP_QUERY_VAR ) ) {
 		return false;
 	}
 

includes/utils/class-amp-css-utils.php

@@ -0,0 +1,18 @@
+<?php
+
+class AMP_CSS_Utils
+{
+	public static function extract_and_minify_css_file($cssFile)
+	{
+		// Load CSS file contents
+		$minified_css = file_get_contents($cssFile);
+		// Remove comments
+		$minified_css = preg_replace('!/\*[^*]*\*+([^/][^*]*\*+)*/!', '', $minified_css);
+		// Remove space after colons
+		$minified_css = str_replace(': ', ':', $minified_css);
+		// Remove whitespace
+		$minified_css = str_replace(array("\r\n", "\r", "\n", "\t", '  ', '    ', '    '), '', $minified_css);
+
+		return $minified_css;
+	}
+}

includes/utils/class-amp-dom-utils.php

@@ -118,4 +118,14 @@ private static function is_self_closing_tag( $tag ) {
 
 		return in_array( $tag, $self_closing_tags, true );
 	}
+
+	/**
+	 * Remove nodes from DOM element
+	 */
+	public static function remove_dom_nodes($nodes_to_remove) {
+		foreach ($nodes_to_remove as $node) {
+			$node->parentNode->removeChild($node);
+		}
+	}
+
 }