unique-title-checker.php

<?php
/**
 * Unique Title Checker
 *
 * @package     unique-title-checker
 * @author      Bernhard Kau
 * @license     GPLv3
 *
 * @wordpress-plugin
 * Plugin Name: Unique Title Checker
 * Plugin URI: https://github.com/2ndkauboy/unique-title-checker
 * Description: Checks if the title of a post, page or custom post type is unique and warn the editor if not
 * Version: 2.1.0
 * Author: Bernhard Kau
 * Author URI: http://kau-boys.de
 * Text Domain: unique-title-checker
 * License: GPLv3
 * License URI: http://www.gnu.org/licenses/gpl-3.0
 */

add_action(
	'plugins_loaded',
	array( Unique_Title_Checker::get_instance(), 'plugin_setup' )
);

/**
 * Class Unique_Title_Checker.
 */
class Unique_Title_Checker {

	/**
	 * Plugin instance.
	 *
	 * @see   get_instance()
	 * @var  object
	 */
	protected static $instance = null;

	/**
	 * URL to this plugin's directory.
	 *
	 * @var  string
	 */
	public $plugin_url = '';

	/**
	 * Path to this plugin's directory.
	 *
	 * @var  string
	 */
	public $plugin_path = '';

	/**
	 * The nonce action.
	 *
	 * @var  string
	 */
	public $nonce_action = 'unique_title_check_nonce';

	/**
	 * The AJAX nonce.
	 *
	 * @var  string
	 */
	public $ajax_nonce = '';

	/**
	 * The `post_title` to be checked
	 *
	 * @var  string
	 */
	public $post_title = '';

	/**
	 * Access this plugin’s working instance.
	 *
	 * @wp-hook plugins_loaded
	 *
	 * @return object The current instance of this class.
	 */
	public static function get_instance() {
		if ( null === self::$instance ) {
			self::$instance = new self();
		}

		return self::$instance;
	}

	/**
	 * Used for regular plugin work.
	 *
	 * @wp-hook plugins_loaded
	 *
	 * @return void
	 */
	public function plugin_setup() {
		$this->plugin_url  = plugins_url( '/', __FILE__ );
		$this->plugin_path = plugin_dir_path( __FILE__ );

		// Enqueue the main JavaScript file.
		add_action( 'admin_enqueue_scripts', array( $this, 'enqueue_scripts' ) );

		// Add the AJAX callback function.
		add_action( 'wp_ajax_unique_title_check', array( $this, 'unique_title_check' ) );

		// Check the uniqueness when a post is edited.
		add_action( 'admin_notices', array( $this, 'uniqueness_admin_notice' ) );

		// Generate the AJAX nonce.
		$this->ajax_nonce = wp_create_nonce( $this->nonce_action );
	}

	/**
	 * Constructor.
	 * Intentionally left empty and public.
	 *
	 * @see plugin_setup()
	 */
	public function __construct() {
	}

	/**
	 * Add the JavaScript files to the admin pages.
	 *
	 * @wp-hook admin_enqueue_scripts
	 *
	 * @param string $hook The current admin page script.
	 *
	 * @return void
	 */
	public function enqueue_scripts( $hook ) {
		// Only enable it on new posts/pages/CPTs.
		if ( ! in_array( $hook, array( 'post.php', 'post-new.php' ), true ) ) {
			return;
		}

		// Enqueue the script.
		$current_screen = get_current_screen();
		if ( method_exists( $current_screen, 'is_block_editor' ) && $current_screen->is_block_editor() ) {
			wp_enqueue_script(
				'unique_title_checker',
				plugins_url( 'js/unique-title-checker-block-editor.js', __FILE__ ),
				array( 'jquery', 'wp-data', 'wp-notices' ),
				filemtime( plugin_dir_path( __FILE__ ) . 'js/unique-title-checker-block-editor.js' ),
				true
			);
		} else {
			wp_enqueue_script(
				'unique_title_checker',
				plugins_url( 'js/unique-title-checker.js', __FILE__ ),
				array( 'jquery' ),
				filemtime( plugin_dir_path( __FILE__ ) . 'js/unique-title-checker.js' ),
				true
			);
		}

		$plugin_options = array(
			'nonce'             => $this->ajax_nonce,
			'only_unique_error' => apply_filters( 'unique_title_checker_only_unique_error', false ),
		);

		// Add the nonce to the form.
		wp_localize_script( 'unique_title_checker', 'unique_title_checker', $plugin_options );
		wp_enqueue_script( 'unique_title_checker' );
	}

	/**
	 * Check the uniqueness and return the result.
	 *
	 * @wp-hook wp_ajax_(action)
	 *
	 * @return void
	 */
	public function unique_title_check() {
		// Verify the ajax request.
		check_ajax_referer( $this->nonce_action, 'ajax_nonce' );

		$args = wp_parse_args(
			$_REQUEST, // WPCS: input var OK.
			array(
				'action',
				'ajax_nonce',
				'post_id',
				'post_type',
				'post_title',
			)
		);

		$response = $this->check_uniqueness( $args );

		echo wp_json_encode( $response );

		die();
	}

	/**
	 * Show an initial warning if the title of a saved post is not unique.
	 *
	 * @wp-hook admin_notices
	 *
	 * @return void
	 */
	public function uniqueness_admin_notice() {
		global $post, $pagenow;

		// Don't show an initial warning on a new post.
		if ( 'post.php' !== $pagenow ) {
			return;
		}

		// Show no warning, when the title is empty.
		if ( empty( $post->post_title ) ) {
			return;
		}

		// phpcs:disable WordPressVIPMinimum.Performance.WPQueryParams.PostNotIn_post__not_in
		// Build the necessary args for the initial uniqueness check.
		$args = array(
			'post__not_in' => array( $post->ID ),
			'post_type'    => $post->post_type,
			'post_title'   => $post->post_title,
		);
		// phpcs:enable WordPressVIPMinimum.Performance.WPQueryParams.PostNotIn_post__not_in

		$response = $this->check_uniqueness( $args );

		// Don't show a message on init, if title is unique.
		if ( 'error' !== $response['status'] ) {
			return;
		}

		printf(
			'<div id="unique-title-message" class="%s"><p>%s</p></div>',
			esc_attr( $response['status'] ),
			esc_html( $response['message'] )
		);
	}

	/**
	 * Check for the uniqueness of the post.
	 *
	 * @param array|string $args The WP_QUERY arguments array or query string.
	 *
	 * @return array The status and message for the response
	 */
	public function check_uniqueness( $args ) {
		// Use the posts_where hook to add the filter for the post_title, as it is not available through WP_Query args.
		add_filter( 'posts_where', array( $this, 'post_title_where' ), 10, 1 );

		// phpcs:disable WordPressVIPMinimum.Performance.WPQueryParams.PostNotIn_post__not_in
		// Use the `post_id` parameter for an excluding post filter.
		if ( isset( $args['post_id'] ) ) {
			$args['post__not_in'][] = $args['post_id'];
			unset( $args['post_id'] );
		}

		// Make sure `post__not_in` is an array.
		if ( ! is_array( $args['post__not_in'] ) ) {
			$args['post__not_in'] = array( $args['post__not_in'] );
		}
		// phpcs:enable WordPressVIPMinimum.Performance.WPQueryParams.PostNotIn_post__not_in

		// Providing a filter to overwrite the search arguments.
		$args = apply_filters( 'unique_title_checker_arguments', $args );

		$post_type_object = get_post_type_object( $args['post_type'] );
		if ( $post_type_object ) {
			$post_type_singular_name = $post_type_object->labels->singular_name;
			$post_type_name          = $post_type_object->labels->name;
		} else {
			$post_type_singular_name = esc_html__( 'post', 'unique-title-checker' );
			$post_type_name          = esc_html__( 'posts', 'unique-title-checker' );
		}

		// Set the `post_title` to be checked.
		$this->post_title = $args['post_title'];

		$query       = new WP_Query( $args );
		$posts_count = $query->post_count;

		if ( empty( $posts_count ) ) {
			$response = array(
				'message' => esc_html__( 'The chosen title is unique.', 'unique-title-checker' ),
				'status'  => 'updated',
			);
		} else {
			if ( 1 === $posts_count ) {
				$message = esc_html(
					sprintf(
					// Translators: %1$s: `post_type` singular name.
						__( 'There is one %1$s with the same title!', 'unique-title-checker' ),
						$post_type_singular_name
					)
				);
			} else {
				// phpcs:disable WordPress.WP.I18n.MismatchedPlaceholders
				$message = esc_html(
					sprintf(
					// Translators: %1$d: posts count, %2$s: `post_type` singular name, %3$s: `post_type` plural name.
						_n(
							'There is %1$d %2$s with the same title!',
							'There are %1$d other %3$s with the same title!',
							$posts_count,
							'unique-title-checker'
						),
						$posts_count,
						$post_type_singular_name,
						$post_type_name
					)
				);
				// phpcs:enable WordPress.WP.I18n.MismatchedPlaceholders
			}
			$response = array(
				'message' => $message,
				'status'  => 'error',
			);
		}

		// Remove filter for post_title.
		remove_filter( 'posts_where', array( $this, 'post_title_where' ), 10 );

		return $response;
	}

	/**
	 * Add the filter for the post_title to the WHERE clause
	 *
	 * @wp-hook wp_ajax_(action)
	 *
	 * @global wpdb  $wpdb  The database object
	 *
	 * @param string $where The WHERE clause.
	 *
	 * @return string The new WHERE clause.
	 */
	public function post_title_where( $where ) {
		global $wpdb;

		return $where . " AND $wpdb->posts.post_title = '" . esc_sql( $this->post_title ) . "'";
	}
}