<?php
/**
 * Sensor: Content
 *
 * Content sensor class file.
 *
 * @since     4.6.0
 * @package   wsal
 * @subpackage sensors
 */

declare(strict_types=1);

namespace WSAL\WP_Sensors;

use WSAL\Helpers\WP_Helper;
use WSAL\Controllers\Alert_Manager;
use WSAL\Entities\Occurrences_Entity;

// Exit if accessed directly.
if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

if ( ! class_exists( '\WSAL\WP_Sensors\WP_Content_Sensor' ) ) {
	/**
	 * WordPress contents (posts, pages and custom posts).
	 *
	 * Apart from some other events, the following were migrated from plugins & themes sensor:
	 * 5019 A plugin created a post
	 * 5025 A plugin deleted a post
	 *
	 * @package    wsal
	 * @subpackage sensors
	 *
	 * @since 4.5.0
	 */
	class WP_Content_Sensor {

		/**
		 * Holds the name of the meta used to setting the lock status of the post
		 */
		const LOCK_META_NAME = '_edit_lock';

		/**
		 * Old post.
		 *
		 * @var stdClass
		 *
		 * @since 4.5.0
		 */
		private static $old_post = null;

		/**
		 * Old permalink.
		 *
		 * @var string
		 *
		 * @since 4.5.0
		 */
		private static $old_link = null;

		/**
		 * Old categories.
		 *
		 * @var array
		 *
		 * @since 4.5.0
		 */
		private static $old_cats = null;

		/**
		 * Old tags.
		 *
		 * @var array
		 *
		 * @since 4.5.0
		 */
		private static $old_tags = null;

		/**
		 * Old path to file.
		 *
		 * @var string
		 *
		 * @since 4.5.0
		 */
		private static $old_tmpl = null;

		/**
		 * Old post is marked as sticky.
		 *
		 * @var boolean
		 *
		 * @since 4.5.0
		 */
		private static $old_sticky = null;

		/**
		 * Old Post Status.
		 *
		 * @var string
		 *
		 * @since 4.5.0
		 */
		private static $old_status = null;

		/**
		 * Old Post Meta.
		 *
		 * @var string
		 *
		 * @since 4.5.0
		 */
		private static $old_meta = null;

		/**
		 * Inits the main hooks
		 *
		 * @return void
		 *
		 * @since 4.5.0
		 */
		public static function init() {
			add_action( 'pre_post_update', array( __CLASS__, 'get_before_post_edit_data' ), 10, 2 );
			add_action( 'save_post', array( __CLASS__, 'post_changed' ), 10, 3 );
			add_action( 'set_object_terms', array( __CLASS__, 'post_terms_changed' ), 10, 4 );
			add_action( 'post_stuck', array( __CLASS__, 'post_stuck_event' ), 10, 1 );
			add_action( 'post_unstuck', array( __CLASS__, 'post_unstuck_event' ), 10, 1 );
			add_action( 'delete_post', array( __CLASS__, 'event_post_deleted' ), 10, 1 );
			add_action( 'wp_trash_post', array( __CLASS__, 'event_post_trashed' ), 10, 1 );
			add_action( 'untrash_post', array( __CLASS__, 'event_post_untrashed' ) );
			add_action( 'future_to_publish', array( __CLASS__, 'event_publish_future' ), 10, 1 );
			add_action( 'admin_action_edit', array( __CLASS__, 'edit_post_in_gutenberg' ), 10 );
			add_filter( 'post_edit_form_tag', array( __CLASS__, 'edit_post_in_classic' ), 10, 1 );
			add_action( 'wp_head', array( __CLASS__, 'viewing_post' ), 10 );
			add_action( 'create_category', array( __CLASS__, 'event_category_creation' ), 10, 1 );
			add_action( 'create_post_tag', array( __CLASS__, 'event_tag_creation' ), 10, 1 );
			add_action( 'pre_delete_term', array( __CLASS__, 'check_taxonomy_term_deletion' ), 10, 2 );
			add_filter( 'wp_update_term_data', array( __CLASS__, 'event_update_term_data' ), 10, 4 );
			add_filter( 'add_post_metadata', array( __CLASS__, 'check_added_meta' ), 10, 5 );
			add_filter( 'delete_post_metadata', array( __CLASS__, 'check_deleted_meta' ), 10, 5 );
			add_action( 'update_post_meta', array( __CLASS__, 'before_changing_meta' ), 10, 4 );
			add_action( 'updated_post_meta', array( __CLASS__, 'check_changed_meta' ), 10, 4 );

			// Check if MainWP Child Plugin exists.
			if ( \WpSecurityAuditLog::is_mainwp_active() ) {
				add_action( 'mainwp_before_post_update', array( __CLASS__, 'event_mainwp_init' ), 10, 2 );
			}
		}

		/**
		 * Get Post Data.
		 *
		 * Collect old post data before post update event.
		 *
		 * @param int $post_id - Post ID.
		 */
		public static function get_before_post_edit_data( $post_id ) {
			$post_id = (int) $post_id; // Making sure that the post id is integer.
			$post    = get_post( $post_id ); // Get post.

			// If post exists.
			if ( ! empty( $post ) && $post instanceof \WP_Post ) {
				self::$old_post   = $post;
				self::$old_link   = get_permalink( $post_id );
				self::$old_tmpl   = self::get_post_template( self::$old_post );
				self::$old_cats   = self::get_post_categories( self::$old_post );
				self::$old_tags   = self::get_post_tags( self::$old_post );
				self::$old_sticky = in_array( $post_id, get_option( 'sticky_posts' ), true );
				self::$old_status = $post->post_status;
				self::$old_meta   = get_post_meta( $post_id );
			}
		}

		/**
		 * Check all the post changes.
		 *
		 * @param integer $post_id - Post ID.
		 * @param WP_Post $post    - WP Post object.
		 * @param boolean $update  - True if post update, false if post is new.
		 *
		 * @since 4.5.0
		 */
		public static function post_changed( $post_id, $post, $update ) {
			// Ignore if post type is empty, revision or trash.
			if ( empty( $post->post_type ) || 'revision' === $post->post_type || 'trash' === $post->post_status ) {
				return;
			}

			if ( null === self::$old_post ) {
				return;
			}

			// Ignorable states.
			if ( defined( 'DOING_AUTOSAVE' ) && DOING_AUTOSAVE ) {
				// Check post creation event.
				if ( self::$old_post && 'auto-draft' === self::$old_post->post_status && 'draft' === $post->post_status ) {
					self::check_post_creation( self::$old_post, $post );
				}
				return;
			}

			/**
			 * Post Changed.
			 *
			 * Don't let the second request for meta update from Gutenberg pass this checkpoint.
			 *
			 * Only pass these requests:
			 *   1. Rest request from Gutenberg.
			 *   2. Classic editor request.
			 *   3. Quick edit ajax request.
			 *
			 * @since 3.4
			 */
			if ( ! defined( 'REST_REQUEST' ) && ! defined( 'DOING_AJAX' ) ) {
				// Either Gutenberg's second post request or classic editor's request.
				if ( ! isset( $_REQUEST['classic-editor'] ) ) {
					$editor_replace = get_option( 'classic-editor-replace', 'classic' );
					$allow_users    = get_option( 'classic-editor-allow-users', 'disallow' );

					// If block editor is selected and users are not allowed to switch editors then it is Gutenberg's second request.
					if ( 'block' === $editor_replace && 'disallow' === $allow_users ) {
						return;
					}

					if ( 'allow' === $allow_users ) { // if users are allowed to switch then it is Gutenberg's second request.
						return;
					}
				}
			}

			if ( $update ) {
				$status_event = self::check_status_change( self::$old_post, $post );

				if ( 2001 !== $status_event && 'auto-draft' !== self::$old_post->post_status ) {
					// Handle update post events.
					$changes = 0;
					$changes = self::check_author_change( self::$old_post, $post )
					+ self::check_parent_change( self::$old_post, $post )
					+ self::check_visibility_change( self::$old_post, $post, self::$old_status, $post->post_status )
					+ self::check_date_change( self::$old_post, $post )
					+ self::check_permalink_change( self::$old_link, get_permalink( $post->ID ), $post )
					+ self::check_comments_pings( self::$old_post, $post );

					// If a status change event has occurred, then don't log event 2002 (post modified).
					$changes = $status_event ? true : $changes;
					if ( '1' === $changes ) {
						remove_action( 'save_post', array( __CLASS__, 'post_changed' ), 10, 3 );
					}
					self::check_modification_change( $post->ID, self::$old_post, $post, $changes );
				}
			} else {
				// If not update then check post creation.
				self::check_post_creation( self::$old_post, $post );
			}
		}

		/**
		 * Check if post terms changed via Gutenberg.
		 *
		 * @param int    $post_id  - Post ID.
		 * @param array  $terms    - Array of terms.
		 * @param array  $tt_ids   - Array of taxonomy term ids.
		 * @param string $taxonomy - Taxonomy slug.
		 *
		 * @since 4.5.0
		 */
		public static function post_terms_changed( $post_id, $terms, $tt_ids, $taxonomy ) {
			$post = get_post( $post_id );

			if ( is_wp_error( $post ) ) {
				return;
			}

			if ( null === $post ) {
				return;
			}

			if ( 'auto-draft' === $post->post_status ) {
				return;
			}

			// Support for Admin Columns Pro plugin and its add-on.
			if ( isset( $_POST['_ajax_nonce'] ) && ! wp_verify_nonce( sanitize_text_field( wp_unslash( $_POST['_ajax_nonce'] ) ), 'ac-ajax' ) ) {
				return;
			}

			if ( isset( $_POST['action'] ) && 'acp_editing_single_request' === sanitize_text_field( wp_unslash( $_POST['action'] ) ) ) {
				return;
			}

			if ( 'post_tag' === $taxonomy ) {
				// Check tags change event.
				self::check_tags_change( self::$old_tags, self::get_post_tags( $post ), $post );
			} else {
				// Check categories change event.
				self::check_categories_change( self::$old_cats, self::get_post_categories( $post ), $post );
			}
		}

		/**
		 * Post Stuck Event.
		 *
		 * @param integer $post_id - Post ID.
		 *
		 * @since 4.5.0
		 */
		public static function post_stuck_event( $post_id ) {
			self::log_sticky_post_event( $post_id, 2049 );
		}

		/**
		 * Post Unstuck Event.
		 *
		 * @param integer $post_id - Post ID.
		 *
		 * @since 4.5.0
		 */
		public static function post_unstuck_event( $post_id ) {
			self::log_sticky_post_event( $post_id, 2050 );
		}

		/**
		 * Post permanently deleted.
		 *
		 * @param integer $post_id - Post ID.
		 *
		 * @since 4.5.0
		 */
		public static function event_post_deleted( $post_id ) {
			// Exclude CPTs from external plugins.
			$post = get_post( $post_id );

			$event = 2008;
			// Check WordPress backend operations.
			if ( self::check_auto_draft( $event, $post->post_title ) ) {
				return;
			}

			$event_data = self::get_post_event_data( $post ); // Get event data.

			// Check if this was initiated by a plugin.
			$request_params = \WSAL\Helpers\PHP_Helper::get_filtered_request_data();
			if ( empty( $request_params['action'] ) && isset( $request_params['page'] ) ) {
				$event      = 5025;
				$event_data = array(
					'PostID'     => $post->ID,
					'PostType'   => $post->post_type,
					'PostTitle'  => $post->post_title,
					'PostStatus' => $post->post_status,
					'Username'   => 'Plugins',
				);
			}

			Alert_Manager::trigger_event( $event, $event_data ); // Log event.
		}

		/**
		 * Post moved to the trash.
		 *
		 * @param integer $post_id - Post ID.
		 *
		 * @since 4.5.0
		 */
		public static function event_post_trashed( $post_id ) {
			$post        = get_post( $post_id );
			$editor_link = self::get_editor_link( $post_id );

			Alert_Manager::trigger_event(
				2012,
				array(
					'PostID'             => $post->ID,
					'PostType'           => $post->post_type,
					'PostTitle'          => $post->post_title,
					'PostStatus'         => $post->post_status,
					'PostDate'           => $post->post_date,
					'PostUrl'            => get_permalink( $post->ID ),
					$editor_link['name'] => $editor_link['value'],
				)
			);
		}

		/**
		 * Post restored from trash.
		 *
		 * @param integer $post_id - Post ID.
		 *
		 * @since 4.5.0
		 */
		public static function event_post_untrashed( $post_id ) {
			$post        = get_post( $post_id );
			$editor_link = self::get_editor_link( $post_id );

			Alert_Manager::trigger_event(
				2014,
				array(
					'PostID'             => $post->ID,
					'PostType'           => $post->post_type,
					'PostTitle'          => $post->post_title,
					'PostStatus'         => $post->post_status,
					'PostDate'           => $post->post_date,
					'PostUrl'            => get_permalink( $post->ID ),
					$editor_link['name'] => $editor_link['value'],
				)
			);
			remove_action( 'save_post', array( __CLASS__, 'post_changed' ), 10, 3 );
		}

		/**
		 * Post future publishing.
		 *
		 * @param integer $post_id - Post ID.
		 *
		 * @since 4.5.0
		 */
		public static function event_publish_future( $post_id ) {
			$post = get_post( $post_id );

			$editor_link = self::get_editor_link( $post_id );

			Alert_Manager::trigger_event(
				2001,
				array(
					'PostID'             => $post->ID,
					'PostType'           => $post->post_type,
					'PostTitle'          => $post->post_title,
					'PostStatus'         => $post->post_status,
					'PostDate'           => $post->post_date,
					'PostUrl'            => get_permalink( $post->ID ),
					$editor_link['name'] => $editor_link['value'],
				)
			);
			remove_action( 'save_post', array( __CLASS__, 'post_changed' ), 10, 3 );
		}

		/**
		 * Alert for Editing of Posts and Custom Post Types in Gutenberg.
		 *
		 * @since 4.5.0
		 */
		public static function edit_post_in_gutenberg() {
			global $pagenow;

			if ( 'post.php' !== $pagenow ) {
				return;
			}

			$post_id = isset( $_GET['post'] ) ? (int) sanitize_text_field( wp_unslash( $_GET['post'] ) ) : false;

			// Check post id.
			if ( empty( $post_id ) ) {
				return;
			}

			if ( is_user_logged_in() && is_admin() ) {
				// Get post.
				$post = get_post( $post_id );

				// Log event.
				self::post_opened_in_editor( $post );
			}
		}

		/**
		 * Alerts for Editing of Posts, Pages and Custom Post Types.
		 *
		 * @param WP_Post $post - Post.
		 *
		 * @since 4.5.0
		 */
		public static function edit_post_in_classic( $post ) {
			if ( is_user_logged_in() && is_admin() ) {
				// Log event.
				self::post_opened_in_editor( $post );
			}
			return $post;
		}

		/**
		 * Post View Event.
		 *
		 * Alerts for Viewing of Posts and Custom Post Types.
		 *
		 * @since 4.5.0
		 */
		public static function viewing_post() {
			// Retrieve the current post object.
			$post = get_queried_object();

			if ( is_user_logged_in() && ! is_admin() ) {
				$current_path = isset( $_SERVER['REQUEST_URI'] ) ? sanitize_text_field( wp_unslash( $_SERVER['REQUEST_URI'] ) ) : false;

				if (
				! empty( $_SERVER['HTTP_REFERER'] )
				&& ! empty( $current_path )
				&& false !== strpos( sanitize_text_field( wp_unslash( $_SERVER['HTTP_REFERER'] ) ), $current_path )
				) {
					// Ignore this if we were on the same page so we avoid double audit entries.
					return;
				}

				if ( ! empty( $post->post_title ) ) {
					$edit_link = self::get_editor_link( $post->ID ); // Get editor link.
					$post_data = self::get_post_event_data( $post ); // Get event post data.

					// Update post URL based on current actual path.
					if ( WP_Helper::is_multisite() && ! is_subdomain_install() ) {
						// For multisite using subfolders, remove the subfolder.
						$subdir_path = parse_url( home_url(), PHP_URL_PATH ); // phpcs:ignore
						if ( ! is_null( $subdir_path ) ) {
							$escaped      = str_replace( '/', '\/', preg_quote( $subdir_path ) ); // phpcs:ignore
							$current_path = preg_replace( '/' . $escaped . '/', '', $current_path );
						}
					}

					// Bail if this don't have this, as it's probably an archive.
					if ( ! isset( $post_data['PostUrl'] ) ) {
						return;
					}

					$full_current_path = home_url( $current_path );
					if ( $full_current_path !== $post_data['PostUrl'] ) {
						$post_data['PostUrl'] = esc_url( $full_current_path );
					}

					// Set editor link.
					$post_data[ $edit_link['name'] ] = $edit_link['value'];
					Alert_Manager::trigger_event( 2101, $post_data );
				}
			}
		}

		/**
		 * New category created.
		 *
		 * @param integer $category_id - Category ID.
		 *
		 * @since 4.5.0
		 */
		public static function event_category_creation( $category_id ) {
			$category      = get_category( $category_id );
			$category_link = self::get_taxonomy_edit_link( $category_id, 'category' );
			Alert_Manager::trigger_event(
				2023,
				array(
					'CategoryName' => $category->name,
					'Slug'         => $category->slug,
					'CategoryLink' => $category_link,
				)
			);
		}

		/**
		 * New tag created.
		 *
		 * @param int $tag_id - Tag ID.
		 *
		 * @since 4.5.0
		 */
		public static function event_tag_creation( $tag_id ) {
			$tag      = get_tag( $tag_id );
			$tag_link = self::get_taxonomy_edit_link( $tag_id );
			Alert_Manager::trigger_event(
				2121,
				array(
					'TagName' => $tag->name,
					'Slug'    => $tag->slug,
					'TagLink' => $tag_link,
				)
			);
		}

		/**
		 * Taxonomy Terms Deleted Events.
		 *
		 * @param integer $term_id  - Term ID.
		 * @param string  $taxonomy - Taxonomy Name.
		 *
		 * @since 4.5.0
		 */
		public static function check_taxonomy_term_deletion( $term_id, $taxonomy ) {
			if ( 'post_tag' === $taxonomy ) {
				$tag = get_tag( $term_id );
				Alert_Manager::trigger_event(
					2122,
					array(
						'TagID'   => $term_id,
						'TagName' => $tag->name,
						'Slug'    => $tag->slug,
					)
				);
			} elseif ( 'category' === $taxonomy ) {
				$category      = get_category( $term_id );
				$category_link = self::get_taxonomy_edit_link( $term_id, $taxonomy );
				Alert_Manager::trigger_event(
					2024,
					array(
						'CategoryID'   => $term_id,
						'CategoryName' => $category->cat_name,
						'Slug'         => $category->slug,
						'CategoryLink' => $category_link,
					)
				);
			}
		}

		/**
		 * Triggered when term data is updated.
		 *
		 * @param array  $data     Term data to be updated.
		 * @param int    $term_id  Term ID.
		 * @param string $taxonomy Taxonomy slug.
		 * @param array  $args     Arguments passed to wp_update_term().
		 *
		 * @since 4.5.0
		 */
		public static function event_update_term_data( $data, $term_id, $taxonomy, $args ) {
			// Get new data.
			$new_name   = isset( $data['name'] ) ? $data['name'] : false;
			$new_slug   = isset( $data['slug'] ) ? $data['slug'] : false;
			$new_desc   = isset( $args['description'] ) ? $args['description'] : false;
			$new_parent = isset( $args['parent'] ) ? $args['parent'] : false;

			// Get old data.
			$term       = get_term( $term_id, $taxonomy );
			$old_name   = $term->name;
			$old_slug   = $term->slug;
			$old_desc   = $term->description;
			$old_parent = $term->parent;
			$term_link  = self::get_taxonomy_edit_link( $term_id, $taxonomy );

			// Check if the taxonomy is `post tag`.
			if ( 'post_tag' === $taxonomy ) {
				// Update if both names are not same.
				if ( $old_name !== $new_name ) {
					Alert_Manager::trigger_event(
						2123,
						array(
							'old_name' => $old_name,
							'new_name' => $new_name,
							'TagLink'  => $term_link,
							'Slug'     => $new_slug,
						)
					);
				}

				// Update if both slugs are not same.
				if ( $old_slug !== $new_slug ) {
					Alert_Manager::trigger_event(
						2124,
						array(
							'tag'      => $new_name,
							'old_slug' => $old_slug,
							'new_slug' => $new_slug,
							'TagLink'  => $term_link,
						)
					);
				}

				// Update if both descriptions are not same.
				if ( $old_desc !== $new_desc ) {
					Alert_Manager::trigger_event(
						2125,
						array(
							'tag'      => $new_name,
							'TagLink'  => $term_link,
							'old_desc' => $old_desc,
							'new_desc' => $new_desc,
						)
					);
				}
			} elseif ( 'category' === $taxonomy ) { // Check if the taxonomy is `category`.
				// Log event if both names are not same.
				if ( $old_name !== $new_name ) {
					Alert_Manager::trigger_event(
						2127,
						array(
							'old_name' => $old_name,
							'new_name' => $new_name,
							'slug'     => $new_slug,
							'cat_link' => $term_link,
						)
					);
				}

				// Log event if both slugs are not same.
				if ( $old_slug !== $new_slug ) {
					Alert_Manager::trigger_event(
						2128,
						array(
							'CategoryName' => $new_name,
							'old_slug'     => $old_slug,
							'new_slug'     => $new_slug,
							'cat_link'     => $term_link,
						)
					);
				}

				if ( 0 !== $old_parent ) {
					$old_parent_obj  = get_category( $old_parent );
					$old_parent_name = empty( $old_parent_obj ) ? 'no parent' : $old_parent_obj->name;
				} else {
					$old_parent_name = 'no parent';
				}
				if ( 0 !== $new_parent ) {
					$new_parent_obj  = get_category( $new_parent );
					$new_parent_name = empty( $new_parent_obj ) ? 'no parent' : $new_parent_obj->name;
				} else {
					$new_parent_name = 'no parent';
				}

				if ( $old_parent_name !== $new_parent_name ) {
					Alert_Manager::trigger_event(
						2052,
						array(
							'CategoryName' => $new_name,
							'OldParent'    => $old_parent_name,
							'NewParent'    => $new_parent_name,
							'CategoryLink' => $term_link,
							'Slug'         => $new_slug,
						)
					);
				}
			}
			return $data; // Return data for the filter.
		}

		/**
		 * Checks if selected metadata items have changed. Function is called from different contexts.
		 *
		 * @param int    $post_id        Post ID.
		 * @param string $meta_key       Meta key.
		 * @param mixed  $meta_value     Meta value.
		 * @param mixed  $default_result Default result. The name is misleading - it holds the meta ID value.
		 *
		 * @return int - The meta ID.
		 *
		 * @since 4.5.0
		 */
		private static function check_selected_meta_change( $post_id, $meta_key, $meta_value, $default_result ) {
			if ( ! $post_id ) {
				return $default_result;
			}

			switch ( $meta_key ) {
				case '_wp_page_template':
					self::check_template_change( $post_id, $meta_value );
					break;
				case '_thumbnail_id':
					self::check_featured_image_change( $post_id, $meta_value );
					break;
				default:
					return $default_result;
			}

			return $default_result;
		}

		/**
		 * Check Page Template Update.
		 *
		 * @param int    $meta_id    ID of updated metadata entry.
		 * @param int    $post_id    Post ID.
		 * @param string $meta_key   Meta key.
		 * @param mixed  $meta_value Meta value.
		 *
		 * @return int ID of updated metadata entry.
		 *
		 * @since 4.5.0
		 */
		public static function check_changed_meta( $meta_id, $post_id, $meta_key, $meta_value ) {
			return self::check_selected_meta_change( $post_id, $meta_key, $meta_value, $meta_id );
		}

		/**
		 * Check Page Template Update for deletions.
		 *
		 * @param null|bool $delete     Whether to allow metadata deletion of the given type.
		 * @param int       $object_id  ID of the object metadata is for.
		 * @param string    $meta_key   Metadata key.
		 * @param mixed     $meta_value Metadata value. Must be serializable if non-scalar.
		 * @param bool      $delete_all Whether to delete the matching metadata entries
		 *                              for all objects, ignoring the specified $object_id.
		 *                              Default false.
		 *
		 * @return bool|null Whether to allow metadata deletion of the given type.
		 *
		 * @since 4.5.0
		 */
		public static function check_deleted_meta( $delete, $object_id, $meta_key, $meta_value, $delete_all ) {
			return self::check_selected_meta_change( $object_id, $meta_key, $meta_value, $delete );
		}

		/**
		 * Check Page Template Update for additions.
		 *
		 * @param null|bool $check      Whether to allow adding metadata for the given type.
		 * @param int       $object_id  ID of the object metadata is for.
		 * @param string    $meta_key   Metadata key.
		 * @param mixed     $meta_value Metadata value. Must be serializable if non-scalar.
		 * @param bool      $unique     Whether the specified meta key should be unique for the object.
		 *
		 * @return bool|null    Whether to allow metadata addition of the given type.
		 *
		 * @since 4.5.0
		 */
		public static function check_added_meta( $check, $object_id, $meta_key, $meta_value, $unique ) {
			return self::check_selected_meta_change( $object_id, $meta_key, $meta_value, $check );
		}

		/**
		 * Check Page Template Update.
		 *
		 * @param int   $post_id    Post ID.
		 * @param mixed $meta_value Meta value.
		 *
		 * @since 4.5.0
		 */
		public static function check_template_change( $post_id, $meta_value ) {
			$post     = get_post( $post_id );
			$old_tmpl = ( self::$old_tmpl && 'page' !== basename( self::$old_tmpl, '.php' ) ) ? ucwords( str_replace( array( '-', '_' ), ' ', basename( self::$old_tmpl, '.php' ) ) ) : __( 'Default template', 'wp-security-audit-log' );
			$new_tmpl = ( $meta_value ) ? ucwords( str_replace( array( '-', '_' ), ' ', basename( $meta_value ) ) ) : __( 'Default', 'wp-security-audit-log' );
			if ( $old_tmpl !== $new_tmpl ) {
				$editor_link = self::get_editor_link( $post_id );
				Alert_Manager::trigger_event(
					2048,
					array(
						'PostID'             => $post->ID,
						'PostType'           => $post->post_type,
						'PostTitle'          => $post->post_title,
						'PostStatus'         => $post->post_status,
						'PostDate'           => $post->post_date,
						'OldTemplate'        => $old_tmpl,
						'NewTemplate'        => $new_tmpl,
						$editor_link['name'] => $editor_link['value'],
					)
				);
			}
		}

		/**
		 * Fires immediately before updating a post's metadata.
		 *
		 * @param int    $meta_id    ID of metadata entry to update.
		 * @param int    $object_id  Post ID.
		 * @param string $meta_key   Metadata key.
		 * @param mixed  $meta_value Metadata value. This will be a PHP-serialized string representation of the value
		 *                           if the value is an array, an object, or itself a PHP-serialized string.
		 *
		 * @since 4.5.0
		 */
		public static function before_changing_meta( $meta_id, $object_id, $meta_key, $meta_value ) {
			if ( self::LOCK_META_NAME === $meta_key ) {
				self::fire_lock_change( (int) $object_id, (string) $meta_value );
			}
		}

		/**
		 * Fires lock owner changing.
		 *
		 * @param integer $post_id   - The ID of the post.
		 * @param string  $meta_value - The meta value - that is in format "1649934679:2"
		 *                             where the "1649934679" is the timestamp of the locking
		 *                             and "2" is the ID of the \WP_User which currently editing the post.
		 *
		 * @return void
		 *
		 * @since 4.5.0
		 */
		public static function fire_lock_change( int $post_id, string $meta_value ) {

			if ( $meta_value ) {
				if ( ! function_exists( 'wp_check_post_lock' ) ) {
					require_once ABSPATH . 'wp-admin/includes/post.php';
				}
				$user_id = \wp_check_post_lock( $post_id ); // The id of the user currently editing the post.

				/**
				 * The post is currently edited by someone - proceed with extracting the new user editor
				 */
				if ( $user_id ) {
					$lock        = explode( ':', $meta_value );
					$new_user_id = $lock[1];

					if ( $new_user_id ) {
						if ( $new_editor_user = get_userdata( $new_user_id ) ) { //phpcs:ignore
							$post        = get_post( $post_id );
							$editor_link = self::get_editor_link( $post_id );
							Alert_Manager::trigger_event(
								2133,
								array(
									'PostID'             => $post->ID,
									'PostType'           => $post->post_type,
									'PostTitle'          => $post->post_title,
									'PostStatus'         => $post->post_status,
									$editor_link['name'] => $editor_link['value'],
									'user'               => get_userdata( $user_id )->display_name,
								)
							);
						}
					}
				}
			}
		}

		/**
		 * Check Post Featured Image Update.
		 *
		 * @param int   $post_id    Post ID.
		 * @param mixed $meta_value Meta value.
		 *
		 * @since 4.5.0
		 */
		public static function check_featured_image_change( $post_id, $meta_value ) {
			$previous_featured_image = ( isset( self::$old_meta['_thumbnail_id'][0] ) ) ? wp_get_attachment_metadata( self::$old_meta['_thumbnail_id'][0] ) : false;
			$new_featured_image      = wp_get_attachment_metadata( $meta_value );

			if ( empty( $new_featured_image['file'] ) && empty( $previous_featured_image['file'] ) ) {
				return;
			}

			$event_type = 'modified';

			if ( empty( $previous_featured_image['file'] ) && ! empty( $new_featured_image['file'] ) ) {
				$event_type = 'added';
			} elseif ( ! empty( $previous_featured_image['file'] ) && empty( $new_featured_image['file'] ) ) {
				$event_type = 'removed';
			}

			$previous_image = is_array( $previous_featured_image ) && array_key_exists( 'file', $previous_featured_image ) ? $previous_featured_image['file'] : __( 'No previous image', 'wp-security-audit-log' );
			$new_image      = is_array( $new_featured_image ) && array_key_exists( 'file', $new_featured_image ) ? $new_featured_image['file'] : __( 'No image', 'wp-security-audit-log' );

			$post        = get_post( $post_id );
			$editor_link = self::get_editor_link( $post_id );
			Alert_Manager::trigger_event(
				2130,
				array(
					'PostID'             => $post->ID,
					'PostType'           => $post->post_type,
					'PostTitle'          => $post->post_title,
					'PostStatus'         => $post->post_status,
					'PostDate'           => $post->post_date,
					'previous_image'     => $previous_image,
					'new_image'          => $new_image,
					$editor_link['name'] => $editor_link['value'],
					'EventType'          => $event_type,
				)
			);
		}

		/**
		 * Collect old post data before MainWP Post update event.
		 *
		 * @param array $new_post    - Array of new post data.
		 * @param array $post_custom - Array of data related to MainWP.
		 *
		 * @since 4.5.0
		 */
		public static function event_mainwp_init( $new_post, $post_custom ) {
			// Get post id.
			$post_id = isset( $post_custom['_mainwp_edit_post_id'][0] ) ? $post_custom['_mainwp_edit_post_id'][0] : false;
			$post_id = (int) $post_id;

			// Check if ID exists.
			if ( $post_id ) {
				// Get post.
				$post = get_post( $post_id );

				// If post exists.
				if ( ! empty( $post ) ) {
					self::$old_post   = $post;
					self::$old_link   = get_permalink( $post_id );
					self::$old_tmpl   = self::get_post_template( self::$old_post );
					self::$old_cats   = self::get_post_categories( self::$old_post );
					self::$old_tags   = self::get_post_tags( self::$old_post );
					self::$old_sticky = in_array( $post_id, get_option( 'sticky_posts' ), true );
				}
			}
		}

		/**
		 * Get the template path.
		 *
		 * @param WP_Post $post - The post.
		 * @return string - Full path to file.
		 *
		 * @since 4.5.0
		 */
		private static function get_post_template( $post ) {
			if ( ! isset( $post->ID ) ) {
				return '';
			}

			$id       = $post->ID;
			$template = get_page_template_slug( $id );
			$pagename = $post->post_name;

			$templates = array();
			if ( $template && 0 === validate_file( $template ) ) {
				$templates[] = $template;
			}
			if ( $pagename ) {
				$templates[] = "page-$pagename.php";
			}
			if ( $id ) {
				$templates[] = "page-$id.php";
			}
			$templates[] = 'page.php';

			return get_query_template( 'page', $templates );
		}

		/**
		 * Get post categories (array of category names).
		 *
		 * @param stdClass $post - The post.
		 * @return array - List of categories.
		 *
		 * @since 4.5.0
		 */
		private static function get_post_categories( $post ) {
			return ! isset( $post->ID ) ? array() : wp_get_post_categories( $post->ID, array( 'fields' => 'names' ) );
		}

		/**
		 * Get post tags (array of tag names).
		 *
		 * @param stdClass $post - The post.
		 * @return array - List of tags.
		 *
		 * @since 4.5.0
		 */
		private static function get_post_tags( $post ) {
			return ! isset( $post->ID ) ? array() : wp_get_post_tags( $post->ID, array( 'fields' => 'names' ) );
		}

		/**
		 * Check post creation.
		 *
		 * @global array $_POST
		 *
		 * @param WP_Post $old_post - Old post.
		 * @param WP_Post $new_post - New post.
		 *
		 * @since 4.5.0
		 */
		private static function check_post_creation( $old_post, $new_post ) {
			if ( ! empty( $new_post ) && $new_post instanceof \WP_Post ) {
				$event        = 0;
				$is_scheduled = false;
				switch ( $new_post->post_status ) {
					case 'publish':
						$event = 2001;
						break;
					case 'draft':
						$event = 2000;
						break;
					case 'future':
						$event        = 2074;
						$is_scheduled = true;
						break;
					case 'pending':
						$event = 2073;
						break;
					default:
						break;
				}
				if ( $event ) {
					$editor_link = self::get_editor_link( $new_post->ID ); // Editor link.
					$event_data  = self::get_post_event_data( $new_post ); // Post event data.

					// Set editor link in the event data.
					$event_data[ $editor_link['name'] ] = $editor_link['value'];

					if ( $is_scheduled ) {
						$event_data['PublishingDate'] = $new_post->post_date;
						Alert_Manager::trigger_event( $event, $event_data );
					} else {

						// So far we assume that the action is initiated by a user, let's check if it was actually initiated
						// by a plugin.
						$request_params = \WSAL\Helpers\PHP_Helper::get_filtered_request_data();
						if ( array_key_exists( 'plugin', $request_params ) && ! empty( $request_params['plugin'] ) ) {
							// Event initiated by a plugin.
							$plugin_name = $request_params['plugin'];
							$plugin_data = get_plugin_data( trailingslashit( WP_PLUGIN_DIR ) . $plugin_name );
							$event_data  = array(
								'PluginName'         => ( $plugin_data && isset( $plugin_data['Name'] ) ) ? $plugin_data['Name'] : false,
								'PostID'             => $new_post->ID,
								'PostType'           => $new_post->post_type,
								'PostTitle'          => $new_post->post_title,
								'PostStatus'         => $new_post->post_status,
								'Username'           => 'Plugins',
								$editor_link['name'] => $editor_link['value'],
							);
						}

						Alert_Manager::trigger_event( $event, $event_data );
					}
				}
			}
		}

		/**
		 * Get editor link.
		 *
		 * @param int $post_id - The \WP_Post post ID.
		 *
		 * @return array $editor_link - Name and value link.
		 *
		 * @since 4.5.0
		 */
		public static function get_editor_link( $post_id ): array {
			$post_id = is_int( $post_id ) ? intval( $post_id ) : $post_id->ID;
			return array(
				'name'  => 'EditorLinkPost',
				'value' => get_edit_post_link( $post_id ),
			);
		}

		/**
		 * Return Post Event Data.
		 *
		 * @param WP_Post $post - WP Post object.
		 * @return array
		 *
		 * @since 4.5.0
		 */
		public static function get_post_event_data( $post ) {
			if ( ! empty( $post ) && $post instanceof \WP_Post ) {
				$event_data = array(
					'PostID'     => $post->ID,
					'PostType'   => $post->post_type,
					'PostTitle'  => $post->post_title,
					'PostStatus' => $post->post_status,
					'PostDate'   => $post->post_date,
					'PostUrl'    => get_permalink( $post->ID ),
				);
				return $event_data;
			}
			return array();
		}

		/**
		 * Author changed.
		 *
		 * @param stdClass $oldpost - Old post.
		 * @param stdClass $newpost - New post.
		 *
		 * @since 4.5.0
		 */
		private static function check_author_change( $oldpost, $newpost ) {
			if ( $oldpost->post_author !== $newpost->post_author ) {
				$editor_link = self::get_editor_link( $oldpost->ID );
				$old_author  = get_userdata( $oldpost->post_author );
				$old_author  = ( is_object( $old_author ) ) ? $old_author->user_login : 'N/A';
				$new_author  = get_userdata( $newpost->post_author );
				$new_author  = ( is_object( $new_author ) ) ? $new_author->user_login : 'N/A';
				Alert_Manager::trigger_event(
					2019,
					array(
						'PostID'             => $oldpost->ID,
						'PostType'           => $oldpost->post_type,
						'PostTitle'          => $oldpost->post_title,
						'PostStatus'         => $oldpost->post_status,
						'PostDate'           => $oldpost->post_date,
						'PostUrl'            => get_permalink( $oldpost->ID ),
						'OldAuthor'          => $old_author,
						'NewAuthor'          => $new_author,
						$editor_link['name'] => $editor_link['value'],
					)
				);
				return 1;
			}
		}

		/**
		 * Status changed.
		 *
		 * @param stdClass $oldpost - Old post.
		 * @param stdClass $newpost - New post.
		 *
		 * @return integer
		 *
		 * @since 4.5.0
		 */
		private static function check_status_change( $oldpost, $newpost ) {
			if ( $oldpost->post_status !== $newpost->post_status ) {
				$event        = 0;
				$is_scheduled = false;

				if ( 'auto-draft' === $oldpost->post_status && 'draft' === $newpost->post_status ) {
					$event = 2000;
				} elseif ( 'publish' === $newpost->post_status ) {
					$event = 2001;
				} elseif ( 'pending' === $newpost->post_status ) {
					$event = 2073;
				} elseif ( 'future' === $newpost->post_status ) {
					$event        = 2074;
					$is_scheduled = true;
				} else {
					$event = 2021;
				}

				if ( $event ) {
					$editor_link = self::get_editor_link( $newpost->ID ); // Editor link.
					$event_data  = self::get_post_event_data( $newpost ); // Post event data.

					// Set editor link in the event data.
					$event_data[ $editor_link['name'] ] = $editor_link['value'];

					if ( $is_scheduled ) {
						$event_data['PublishingDate'] = $newpost->post_date;
						Alert_Manager::trigger_event( $event, $event_data );
					} elseif ( 2021 === $event ) {
						$event_data['OldStatus'] = $oldpost->post_status;
						$event_data['NewStatus'] = $newpost->post_status;
						Alert_Manager::trigger_event( $event, $event_data );
					} else {
						// NOTE: this triggers if NOT firing event 5019.
						Alert_Manager::trigger_event_if( $event, $event_data, array( __CLASS__, 'plugin_not_created_post' ) );
					}
				}

				return $event;
			}
		}

		/**
		 * Post parent changed.
		 *
		 * @param stdClass $oldpost - Old post.
		 * @param stdClass $newpost - New post.
		 *
		 * @since 4.5.0
		 */
		private static function check_parent_change( $oldpost, $newpost ) {
			if ( $oldpost->post_parent !== $newpost->post_parent && 'page' === $newpost->post_type ) {
				$editor_link = self::get_editor_link( $oldpost->ID );
				Alert_Manager::trigger_event(
					2047,
					array(
						'PostID'             => $oldpost->ID,
						'PostType'           => $oldpost->post_type,
						'PostTitle'          => $oldpost->post_title,
						'PostStatus'         => $oldpost->post_status,
						'PostDate'           => $oldpost->post_date,
						'OldParent'          => $oldpost->post_parent,
						'NewParent'          => $newpost->post_parent,
						'OldParentName'      => $oldpost->post_parent ? get_the_title( $oldpost->post_parent ) : 'no parent',
						'NewParentName'      => $newpost->post_parent ? get_the_title( $newpost->post_parent ) : 'no parent',
						$editor_link['name'] => $editor_link['value'],
					)
				);
				return 1;
			}
		}

		/**
		 * Permalink changed.
		 *
		 * @param string   $old_link - Old permalink.
		 * @param string   $new_link - New permalink.
		 *
		 * @param stdClass $post - The post.
		 *
		 * @since 4.5.0
		 */
		private static function check_permalink_change( $old_link, $new_link, $post ) {
			if ( in_array( $post->post_status, array( 'draft', 'pending' ), true ) ) {
				$old_link = self::$old_post->post_name;
				$new_link = $post->post_name;
			}

			if ( $old_link !== $new_link ) {
				$editor_link = self::get_editor_link( $post->ID );
				Alert_Manager::trigger_event(
					2017,
					array(
						'PostID'             => $post->ID,
						'PostType'           => $post->post_type,
						'PostTitle'          => $post->post_title,
						'PostStatus'         => $post->post_status,
						'PostDate'           => $post->post_date,
						'OldUrl'             => $old_link,
						'NewUrl'             => $new_link,
						$editor_link['name'] => $editor_link['value'],
					)
				);
				return 1;
			}
			return 0;
		}

		/**
		 * Post visibility changed.
		 *
		 * @param WP_Post $oldpost - Old post.
		 * @param WP_Post $newpost - New post.
		 * @param string  $old_status - Old status.
		 * @param string  $new_status - New status.
		 *
		 * @since 4.5.0
		 */
		private static function check_visibility_change( $oldpost, $newpost, $old_status, $new_status ) {
			$old_visibility = '';
			$new_visibility = '';

			if ( $oldpost->post_password ) {
				$old_visibility = esc_html__( 'Password Protected', 'wp-security-audit-log' );
			} elseif ( 'private' === $oldpost->post_status ) {
				$old_visibility = esc_html__( 'Private', 'wp-security-audit-log' );
			} else {
				$old_visibility = esc_html__( 'Public', 'wp-security-audit-log' );
			}

			if ( $newpost->post_password ) {
				$new_visibility = esc_html__( 'Password Protected', 'wp-security-audit-log' );
			} elseif ( 'private' === $newpost->post_status ) {
				$new_visibility = esc_html__( 'Private', 'wp-security-audit-log' );
			} else {
				$new_visibility = esc_html__( 'Public', 'wp-security-audit-log' );
			}

			if ( $old_visibility && $new_visibility && ( $old_visibility !== $new_visibility ) ) {
				$editor_link = self::get_editor_link( $oldpost->ID );
				Alert_Manager::trigger_event(
					2025,
					array(
						'PostID'             => $oldpost->ID,
						'PostType'           => $oldpost->post_type,
						'PostTitle'          => $oldpost->post_title,
						'PostStatus'         => $newpost->post_status,
						'PostDate'           => $oldpost->post_date,
						'PostUrl'            => get_permalink( $oldpost->ID ),
						'OldVisibility'      => $old_visibility,
						'NewVisibility'      => $new_visibility,
						$editor_link['name'] => $editor_link['value'],
					)
				);
				return 1;
			}
		}

		/**
		 * Post date changed.
		 *
		 * @param \WP_Post $oldpost - Old post.
		 * @param \WP_Post $newpost - New post.
		 *
		 * @since 4.5.0
		 */
		private static function check_date_change( $oldpost, $newpost ) {
			$from = 0;
			$to = 0;
			if ( isset( $oldpost->post_date ) && null !== $oldpost->post_date ) {
				$from = strtotime( $oldpost->post_date );
			}
			if ( isset( $newpost->post_date ) && null !== $newpost->post_date ) {
				$to   = strtotime( $newpost->post_date );
			}

			if ( 'pending' === $oldpost->post_status ) {
				return 0;
			}

			/*
			 * Return early if this looks like a re-save on a draft.
			 */
			if ( self::is_draft_resave( $oldpost, $newpost ) ) {
				return 0;
			}

			if ( $from !== $to ) {
				$editor_link = self::get_editor_link( $oldpost->ID );
				Alert_Manager::trigger_event(
					2027,
					array(
						'PostID'             => $oldpost->ID,
						'PostType'           => $oldpost->post_type,
						'PostTitle'          => $oldpost->post_title,
						'PostStatus'         => $oldpost->post_status,
						'PostDate'           => $newpost->post_date,
						'PostUrl'            => get_permalink( $oldpost->ID ),
						'OldDate'            => $oldpost->post_date,
						'NewDate'            => $newpost->post_date,
						$editor_link['name'] => $editor_link['value'],
					)
				);
				return 1;
			}
			return 0;
		}

		/**
		 * Comments/Trackbacks and Pingbacks check.
		 *
		 * @param stdClass $oldpost - Old post.
		 * @param stdClass $newpost - New post.
		 *
		 * @since 4.5.0
		 */
		private static function check_comments_pings( $oldpost, $newpost ) {
			$result      = 0;
			$editor_link = self::get_editor_link( $newpost->ID );

			// Comments.
			if ( $oldpost->comment_status !== $newpost->comment_status ) {
				Alert_Manager::trigger_event(
					2111,
					array(
						'PostID'             => $newpost->ID,
						'PostType'           => $newpost->post_type,
						'PostStatus'         => $newpost->post_status,
						'PostDate'           => $newpost->post_date,
						'PostTitle'          => $newpost->post_title,
						'PostUrl'            => get_permalink( $newpost->ID ),
						$editor_link['name'] => $editor_link['value'],
						'EventType'          => 'open' === $newpost->comment_status ? 'enabled' : 'disabled',
					)
				);
				$result = 1;
			}

			// Trackbacks and Pingbacks.
			if ( $oldpost->ping_status !== $newpost->ping_status ) {
				Alert_Manager::trigger_event(
					2112,
					array(
						'PostID'             => $newpost->ID,
						'PostType'           => $newpost->post_type,
						'PostTitle'          => $newpost->post_title,
						'PostStatus'         => $newpost->post_status,
						'PostDate'           => $newpost->post_date,
						'PostUrl'            => get_permalink( $newpost->ID ),
						$editor_link['name'] => $editor_link['value'],
						'EventType'          => 'open' === $newpost->ping_status ? 'enabled' : 'disabled',
					)
				);
				$result = 1;
			}
			return $result;
		}

		/**
		 * Categories changed.
		 *
		 * @param array   $old_cats - Old categories.
		 * @param array   $new_cats - New categories.
		 * @param WP_Post $post     - The post.
		 *
		 * @since 4.5.0
		 */
		private static function check_categories_change( $old_cats, $new_cats, $post ) {
			$old_cats = implode( ', ', (array) $old_cats );
			$new_cats = implode( ', ', (array) $new_cats );

			if ( $old_cats !== $new_cats && 'page' !== $post->post_type ) {
				$editor_link = self::get_editor_link( $post->ID );
				$alert_data  = array(
					'PostID'             => $post->ID,
					'PostType'           => $post->post_type,
					'PostTitle'          => $post->post_title,
					'PostStatus'         => $post->post_status,
					'PostDate'           => $post->post_date,
					'PostUrl'            => get_permalink( $post->ID ),
					'OldCategories'      => $old_cats ? $old_cats : 'no categories',
					'NewCategories'      => $new_cats ? $new_cats : 'no categories',
					$editor_link['name'] => $editor_link['value'],
				);
				Alert_Manager::trigger_event( 2016, $alert_data );
			}
		}

		/**
		 * Reports tags change event. This could be tags addition, removal and possibly other in the future.
		 *
		 * @param int      $event_code   Event code.
		 * @param WP_Post  $post         WordPress post object.
		 * @param string[] $tags_changed Changed tags.
		 *
		 * @since 4.5.0
		 */
		private static function report_tags_change_event( $event_code, $post, $tags_changed ) {
			$editor_link = self::get_editor_link( $post->ID );
			$post_status = ( 'publish' === $post->post_status ) ? 'published' : $post->post_status;
			Alert_Manager::trigger_event(
				$event_code,
				array(
					'PostID'             => $post->ID,
					'PostType'           => $post->post_type,
					'PostStatus'         => $post_status,
					'PostTitle'          => $post->post_title,
					'PostDate'           => $post->post_date,
					'PostUrl'            => get_permalink( $post->ID ),
					'tag'                => ! empty( $tags_changed ) ? implode( ', ', $tags_changed ) : esc_html__( 'no tags', 'wp-security-audit-log' ),
					$editor_link['name'] => $editor_link['value'],
				)
			);
		}

		/**
		 * Tags changed.
		 *
		 * @param array   $old_tags - Old tags.
		 * @param array   $new_tags - New tags.
		 * @param WP_Post $post - The post.
		 *
		 * @since 4.5.0
		 */
		private static function check_tags_change( $old_tags, $new_tags, $post ) {
			// Ensure old_tags is not null.
			if ( ! $old_tags ) {
				$old_tags = array();
			}
			$intersection = array_intersect( $old_tags, $new_tags );
			if ( count( $intersection ) === count( $old_tags ) && count( $old_tags ) === count( $new_tags ) ) {
				// No change, let's leave.
				return;
			}

			// Check for added tags.
			$added_tags = array_diff( (array) $new_tags, (array) $old_tags );
			if ( ! empty( $added_tags ) ) {
				self::report_tags_change_event( 2119, $post, $added_tags );
			}

			// Check for removed tags.
			$removed_tags = array_diff( (array) $old_tags, (array) $new_tags );
			if ( ! empty( $removed_tags ) ) {
				self::report_tags_change_event( 2120, $post, $removed_tags );
			}
		}

		/**
		 * Post modified content.
		 *
		 * @param integer  $post_id – Post ID.
		 * @param stdClass $oldpost – Old post.
		 * @param stdClass $newpost – New post.
		 * @param int      $modified – Set to 0 if no changes done to the post.
		 *
		 * @return int|void
		 *
		 * @since 4.5.0
		 */
		public static function check_modification_change( $post_id, $oldpost, $newpost, $modified ) {
			self::check_title_change( $oldpost, $newpost );

			$content_changed = $oldpost->post_content !== $newpost->post_content;

			/*
			 * If the content hasn't changed and this looks to be a draft resave
			 * then we won't track anything for this modification.
			 */
			if ( ! $content_changed && self::is_draft_resave( $oldpost, $newpost ) ) {
				return;
			}

			if ( $oldpost->post_modified !== $newpost->post_modified ) {
				$event = 0;

				if ( $content_changed ) { // Check if content changed.
					$event = 2065;
				} elseif ( ! $modified ) {
					$event = 2002;
				}

				if ( $event ) {
					if ( 2002 === $event ) {
						// Get Yoast alerts.
						$yoast_alerts         = Alert_Manager::get_alerts_by_category( 'Yoast SEO' );
						$yoast_metabox_alerts = Alert_Manager::get_alerts_by_category( 'Yoast SEO Meta Box' );
						$yoast_alerts         = $yoast_alerts + $yoast_metabox_alerts;
						// Check all alerts.
						foreach ( $yoast_alerts as $alert_code => $alert ) {
							if ( Alert_Manager::will_or_has_triggered( $alert_code ) ) {
								return 0; // Return if any Yoast alert has or will trigger.
							}
						}
					}

					$event_data                         = self::get_post_event_data( $oldpost );
					$editor_link                        = self::get_editor_link( $oldpost->ID );
					$event_data[ $editor_link['name'] ] = $editor_link['value'];
					$event_data['RevisionLink']         = self::get_post_revision( $post_id, $oldpost );

					// Check excerpt change.
					$old_post_excerpt = $oldpost->post_excerpt;
					$post_excerpt     = get_post_field( 'post_excerpt', $post_id );

					if ( empty( $old_post_excerpt ) && ! empty( $post_excerpt ) ) {
						$event_data['EventType'] = 'added';
					} elseif ( ! empty( $old_post_excerpt ) && empty( $post_excerpt ) ) {
						$event_data['EventType'] = 'removed';
					} elseif ( $old_post_excerpt !== $post_excerpt ) {
						$event_data['EventType'] = 'modified';
					}

					if ( $old_post_excerpt !== $post_excerpt ) {
						$event = 2129;
						// We are purposefully showing an empty, not NULL value.
						$event_data['old_post_excerpt'] = ( $old_post_excerpt ) ? $old_post_excerpt : ' ';
						$event_data['post_excerpt']     = ( $post_excerpt ) ? $post_excerpt : ' ';
					}

					if ( 2002 === $event ) {
						// If we reach this point, we no longer need to check if the content has changed as we already have
						// an event to handle it. So trigger 2002 regardless and "something" has changed in the post, we
						// just don't detect it elsewhere.
						Alert_Manager::trigger_event_if( $event, $event_data, array( __CLASS__, 'ignore_other_post_events' ) );
					} else {
						Alert_Manager::trigger_event( $event, $event_data );
					}
				}
			}
		}

		/**
		 * Method: Ensure no other post-related events are being fired, or have recently been fired.
		 *
		 * @return bool
		 *
		 * @since 4.5.0
		 */
		public static function ignore_other_post_events() {

			$post_events = array_keys( Alert_Manager::get_alerts_by_sub_category( 'Content' ) );

			$post_events = array_merge( $post_events, array_keys( Alert_Manager::get_alerts_by_sub_category( 'Coupons' ) ) );

			$post_events = array_merge( $post_events, array_keys( Alert_Manager::get_alerts_by_sub_category( 'Tags' ) ) );

			$post_events = array_merge( $post_events, array_keys( Alert_Manager::get_alerts_by_sub_category( 'Categories' ) ) );

			$post_events = array_merge( $post_events, array_keys( Alert_Manager::get_alerts_by_sub_category( 'Custom Fields' ) ) );

			$post_events = array_merge( $post_events, array_keys( Alert_Manager::get_alerts_by_sub_category( 'Custom Fields (ACF)' ) ) );

			$post_events = array_merge( $post_events, array_keys( Alert_Manager::get_alerts_by_sub_category( 'Comments' ) ) );

			$post_events = array_merge( $post_events, array_keys( Alert_Manager::get_alerts_by_sub_category( 'Custom Post Types' ) ) );

			$post_events = array_merge( $post_events, array_keys( Alert_Manager::get_alerts_by_sub_category( 'Pages' ) ) );

			foreach ( $post_events as $event ) {
				if ( Alert_Manager::will_or_has_triggered( $event ) || Alert_Manager::was_triggered_recently( $event ) ) {
					return false;
				}
			}

			return true;
		}

		/**
		 * Changed title of a post.
		 *
		 * @param stdClass $oldpost - Old post.
		 * @param stdClass $newpost - New post.
		 *
		 * @since 4.5.0
		 */
		private static function check_title_change( $oldpost, $newpost ) {
			if ( $oldpost->post_title !== $newpost->post_title ) {
				$editor_link = self::get_editor_link( $oldpost->ID );
				Alert_Manager::trigger_event(
					2086,
					array(
						'PostID'             => $newpost->ID,
						'PostType'           => $newpost->post_type,
						'PostTitle'          => $newpost->post_title,
						'PostStatus'         => $newpost->post_status,
						'PostDate'           => $newpost->post_date,
						'PostUrl'            => get_permalink( $newpost->ID ),
						'OldTitle'           => $oldpost->post_title,
						'NewTitle'           => $newpost->post_title,
						$editor_link['name'] => $editor_link['value'],
					)
				);
				return 1;
			}
			return 0;
		}

		/**
		 * Return post revision link.
		 *
		 * @param integer $post_id - Post ID.
		 * @param WP_Post $post    - WP Post object.
		 *
		 * @return string
		 *
		 * @since 4.5.0
		 */
		private static function get_post_revision( $post_id, $post ) {
			$revisions = wp_get_post_revisions( $post_id );
			if ( ! empty( $revisions ) ) {
				$revision = array_shift( $revisions );
				return self::get_revision_link( $revision->ID );
			}
		}

		/**
		 * Builds revision link.
		 *
		 * @param integer $revision_id - Revision ID.
		 *
		 * @return string|null - Link.
		 *
		 * @since 4.5.0
		 */
		private static function get_revision_link( $revision_id ) {
			return ! empty( $revision_id ) ? add_query_arg( 'revision', $revision_id, admin_url( 'revision.php' ) ) : null;
		}

		/**
		 * Log post stuck/unstuck events.
		 *
		 * @param integer $post_id - Post ID.
		 * @param integer $event   - Event ID.
		 *
		 * @since 4.5.0
		 */
		private static function log_sticky_post_event( $post_id, $event ) {
			// Get post.
			$post = get_post( $post_id );

			if ( is_wp_error( $post ) ) {
				return;
			}

			$editor_link = self::get_editor_link( $post_id ); // Editor link.
			$event_data  = self::get_post_event_data( $post ); // Event data.

			$event_data[ $editor_link['name'] ] = $editor_link['value'];
			Alert_Manager::trigger_event( $event, $event_data );
		}

		/**
		 * Check auto draft and the setting: Hide Plugin in Plugins Page
		 *
		 * @param integer $code  - Alert code.
		 * @param string  $title - Title.
		 *
		 * @return boolean
		 *
		 * @since 4.5.0
		 */
		private static function check_auto_draft( $code, $title ) {
			$ignore = 0;
			if ( 2008 === $code && ( 'auto-draft' === $title || 'Auto Draft' === $title ) ) {
				$ignore = ! \WSAL\Helpers\Settings_Helper::get_boolean_option_value( 'wp-backend' );
			}
			return $ignore;
		}

		/**
		 * Post Opened for Editing in WP Editors.
		 *
		 * @param WP_Post $post – Post object.
		 *
		 * @since 4.5.0
		 */
		public static function post_opened_in_editor( $post ) {
			if ( empty( $post ) || ! $post instanceof \WP_Post ) {
				return;
			}

			$current_path = isset( $_SERVER['SCRIPT_NAME'] ) ? esc_url_raw( wp_unslash( $_SERVER['SCRIPT_NAME'] ) ) . '?post=' . $post->ID : false;
			$referrer     = isset( $_SERVER['HTTP_REFERER'] ) ? esc_url_raw( wp_unslash( $_SERVER['HTTP_REFERER'] ) ) : false;

			// Check referrer URL.
			if ( ! empty( $referrer ) ) {
				// Parse the referrer.
				$parsed_url = wp_parse_url( $referrer );

				// If the referrer is post-new then we can ignore this one.
				if ( isset( $parsed_url['path'] ) && 'post-new' === basename( $parsed_url['path'], '.php' ) ) {
					return $post;
				}
			}

			if ( ! empty( $referrer ) && strpos( $referrer, $current_path ) !== false ) {
				// Ignore this if we were on the same page so we avoid double audit entries.
				return $post;
			}

			if ( ! empty( $post->post_title ) ) {
				$event = 2100;
				if ( ! Alert_Manager::was_triggered( $event ) ) {
					$editor_link = self::get_editor_link( $post->ID );
					Alert_Manager::trigger_event(
						$event,
						array(
							'PostID'             => $post->ID,
							'PostType'           => $post->post_type,
							'PostTitle'          => $post->post_title,
							'PostStatus'         => $post->post_status,
							'PostDate'           => $post->post_date,
							'PostUrl'            => get_permalink( $post->ID ),
							$editor_link['name'] => $editor_link['value'],
						)
					);
				}
			}
		}

		/**
		 * Builds category link.
		 *
		 * @param integer $tag_id   - Tag ID.
		 * @param string  $taxonomy - Taxonomy.
		 *
		 * @return string|null - Link.
		 *
		 * @since 4.5.0
		 */
		private static function get_taxonomy_edit_link( $tag_id, $taxonomy = 'post_tag' ) {
			$tag_args = array(
				'taxonomy' => $taxonomy,
				'tag_ID'   => $tag_id,
			);
			return ! empty( $tag_id ) ? add_query_arg( $tag_args, admin_url( 'term.php' ) ) : null;
		}

		/**
		 * Returns true if this looks like a re-save on a draft.
		 *
		 * @method is_draft_resave
		 *
		 * @param  \WP_Post $oldpost The old post object if one exists.
		 * @param  \WP_Post $newpost The new post object.
		 *
		 * @return boolean
		 *
		 * @since 4.5.0
		 */
		private static function is_draft_resave( $oldpost, $newpost ) {
			/*
			 * If this is a 'draft' and used to be a 'draft' plus the gmt dates
			 * match and it contains only characters that would appear in the
			 * a default unpublished post then...
			 */
			if ( 'draft' === $oldpost->post_status
			&& $oldpost->post_status === $newpost->post_status
			&& $oldpost->post_date_gmt === $newpost->post_date_gmt
			&& preg_match( '/^[0\-\ \:]+$/', $oldpost->post_date_gmt ) ) {
				// Don't track this as a date change.
				return true;
			}
		}

		/**
		 * Callback to test if a post was just made by a plugin.
		 *
		 * NOTE: the return is flipped to handle a double NOT in _CommitItem().
		 *
		 * @method plugin_not_created_post
		 *
		 * @return boolean
		 *
		 * @since 4.5.0
		 */
		public static function plugin_not_created_post() {
			// Ensure no event for a WC coupon.
			if ( Alert_Manager::will_or_has_triggered( 9063 ) ) {
				return false;
			}

			$triggered = Alert_Manager::will_or_has_triggered( 5019 );
			// inverting value here to account for the double NOT in _CommitItem().

			return ! $triggered;
		}
	}
}
