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wp/wp-content/plugins/wordpress-seo/src/integrations/front-end/indexing-controls.php

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+<?php
+
+namespace Yoast\WP\SEO\Integrations\Front_End;
+
+use Yoast\WP\SEO\Conditionals\Front_End_Conditional;
+use Yoast\WP\SEO\Helpers\Robots_Helper;
+use Yoast\WP\SEO\Integrations\Integration_Interface;
+
+/**
+ * Class Indexing_Controls.
+ */
+class Indexing_Controls implements Integration_Interface {
+
+	/**
+	 * The robots helper.
+	 *
+	 * @var Robots_Helper
+	 */
+	protected $robots;
+
+	/**
+	 * Returns the conditionals based in which this loadable should be active.
+	 *
+	 * @return array
+	 */
+	public static function get_conditionals() {
+		return [ Front_End_Conditional::class ];
+	}
+
+	/**
+	 * The constructor.
+	 *
+	 * @codeCoverageIgnore Sets the dependencies.
+	 *
+	 * @param Robots_Helper $robots The robots helper.
+	 */
+	public function __construct( Robots_Helper $robots ) {
+		$this->robots = $robots;
+	}
+
+	/**
+	 * Initializes the integration.
+	 *
+	 * This is the place to register hooks and filters.
+	 *
+	 * @codeCoverageIgnore
+	 *
+	 * @return void
+	 */
+	public function register_hooks() {
+		// The option `blog_public` is set in Settings > Reading > Search Engine Visibility.
+		if ( (string) \get_option( 'blog_public' ) === '0' ) {
+			\add_filter( 'wpseo_robots_array', [ $this->robots, 'set_robots_no_index' ] );
+		}
+
+		\add_action( 'template_redirect', [ $this, 'noindex_robots' ] );
+		\add_filter( 'loginout', [ $this, 'nofollow_link' ] );
+		\add_filter( 'register', [ $this, 'nofollow_link' ] );
+
+		// Remove actions that we will handle through our wpseo_head call, and probably change the output of.
+		\remove_action( 'wp_head', 'rel_canonical' );
+		\remove_action( 'wp_head', 'index_rel_link' );
+		\remove_action( 'wp_head', 'start_post_rel_link' );
+		\remove_action( 'wp_head', 'adjacent_posts_rel_link_wp_head' );
+		\remove_action( 'wp_head', 'noindex', 1 );
+	}
+
+	/**
+	 * Sends a Robots HTTP header preventing URL from being indexed in the search results while allowing search engines
+	 * to follow the links in the object at the URL.
+	 *
+	 * @return bool Boolean indicating whether the noindex header was sent.
+	 */
+	public function noindex_robots() {
+		if ( ! \is_robots() ) {
+			return false;
+		}
+
+		return $this->set_robots_header();
+	}
+
+	/**
+	 * Adds rel="nofollow" to a link, only used for login / registration links.
+	 *
+	 * @param string $input The link element as a string.
+	 *
+	 * @return string
+	 */
+	public function nofollow_link( $input ) {
+		return \str_replace( '<a ', '<a rel="nofollow" ', $input );
+	}
+
+	/**
+	 * Sets the x-robots-tag to noindex follow.
+	 *
+	 * @codeCoverageIgnore Too difficult to test.
+	 *
+	 * @return bool
+	 */
+	protected function set_robots_header() {
+		if ( \headers_sent() === false ) {
+			\header( 'X-Robots-Tag: noindex, follow', true );
+
+			return true;
+		}
+
+		return false;
+	}
+}