Revert #725: Abstract notion of AMP Actions

amp.php

@@ -150,12 +150,13 @@ function amp_load_classes() {
 }
 
 function amp_add_frontend_actions() {
-	AMP_Frontend_Actions::register_hooks();
+	require_once AMP__DIR__ . '/includes/amp-frontend-actions.php';
 }
 
 function amp_add_post_template_actions() {
-	AMP_Paired_Post_Actions::register_hooks();
-	require_once( AMP__DIR__ . '/includes/amp-post-template-functions.php' );
+	require_once AMP__DIR__ . '/includes/amp-post-template-actions.php';
+	require_once AMP__DIR__ . '/includes/amp-post-template-functions.php';
+	amp_post_template_init_hooks();
 }
 
 function amp_prepare_render() {

includes/amp-frontend-actions.php

@@ -0,0 +1,28 @@
+<?php
+/**
+ * Callbacks for adding AMP-related things to the main theme.
+ *
+ * @package AMP
+ */
+
+add_action( 'wp_head', 'amp_frontend_add_canonical' );
+
+/**
+ * Add amphtml link to frontend.
+ *
+ * @since 0.2
+ */
+function amp_frontend_add_canonical() {
+
+	/**
+	 * Filters whether to show the amphtml link on the frontend.
+	 *
+	 * @since 0.2
+	 */
+	if ( false === apply_filters( 'amp_frontend_show_canonical', true ) ) {
+		return;
+	}
+
+	$amp_url = amp_get_permalink( get_queried_object_id() );
+	printf( '<link rel="amphtml" href="%s">', esc_url( $amp_url ) );
+}