<?php
/**
 * Sorts every piece of a WordPress site into a sync class.
 *
 * The class decides whether something can be synced at all. Configuration and
 * content made on staging can go live; environment settings, user data and
 * caches never do. Anything the rules do not know stays "unassigned" and is
 * never synced automatically.
 *
 * @package WonderfulSync
 */

namespace WonderfulPlugins\WonderfulSync;

if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

/**
 * Rule-based classifier for options, post types, post meta and tables.
 */
class Classifier {

	const CODE        = 'code';
	const DESIGN      = 'design';
	const LAYOUT      = 'layout';
	const CONTENT     = 'content';
	const SITE        = 'site';
	const ENVIRONMENT = 'environment';
	const USER_DATA   = 'user_data';
	const CACHE       = 'cache';
	const UNASSIGNED  = 'unassigned';

	/**
	 * Classes whose objects may be part of a changeset.
	 */
	const SYNCABLE = array( self::CODE, self::DESIGN, self::LAYOUT, self::CONTENT, self::SITE );

	/**
	 * Option rules: exact names first, then prefixes (longest prefix wins).
	 *
	 * @var array<string, array<string, string>>
	 */
	private $option_rules = array(
		'exact'  => array(
			// Divi design data.
			'et_divi'                    => self::DESIGN,
			'builder_global_presets_d5'  => self::DESIGN,
			'builder_global_presets_ng'  => self::DESIGN,
			'builder_global_presets'     => self::DESIGN,
			'global_variables'           => self::DESIGN,
			'et_global_data'             => self::DESIGN,
			'et_global_colors'           => self::DESIGN,
			'et_uploaded_fonts'          => self::DESIGN,
			// Order of Divi Library items in the component manager (lists of layout IDs).
			'_et_pb_component_manager_order' => self::LAYOUT,
			'custom_css_post_id'         => self::DESIGN,

			// Site settings that are meant to move with a redesign.
			'page_on_front'              => self::SITE,
			'page_for_posts'             => self::SITE,
			'show_on_front'              => self::SITE,
			'blogname'                   => self::SITE,
			'blogdescription'            => self::SITE,
			'sidebars_widgets'           => self::SITE,
			'nav_menu_options'           => self::SITE,
			'site_icon'                  => self::SITE,
			'posts_per_page'             => self::SITE,
			'date_format'                => self::SITE,
			'time_format'                => self::SITE,
			'timezone_string'            => self::SITE,
			'gmt_offset'                 => self::SITE,
			'WPLANG'                     => self::SITE,

			// Environment: belongs to the installation, never synced.
			'siteurl'                    => self::ENVIRONMENT,
			'home'                       => self::ENVIRONMENT,
			'admin_email'                => self::ENVIRONMENT,
			'new_admin_email'            => self::ENVIRONMENT,
			'active_plugins'             => self::ENVIRONMENT,
			'template'                   => self::ENVIRONMENT,
			'stylesheet'                 => self::ENVIRONMENT,
			'users_can_register'         => self::ENVIRONMENT,
			'default_role'               => self::ENVIRONMENT,
			'db_version'                 => self::ENVIRONMENT,
			'initial_db_version'         => self::ENVIRONMENT,
			'wp_user_roles'              => self::ENVIRONMENT,
			'cron'                       => self::ENVIRONMENT,
			'current_theme'              => self::ENVIRONMENT,
			// Divi Visual Builder workspace layout of the editor, not of the website.
			'et_divi_builder_workspaces' => self::ENVIRONMENT,
			// Visual Builder settings of the editors (product tour, post type integration).
			'et_pb_builder_options'      => self::ENVIRONMENT,
			'wp_calendar_block_has_published_posts' => self::CACHE,
			// Divi's news feed for the builder, fetched from Elegant Themes.
			'et_divi_builder_announcements_cache' => self::CACHE,
			'recently_activated'         => self::ENVIRONMENT,
			'uninstall_plugins'          => self::ENVIRONMENT,
			'auth_key'                   => self::ENVIRONMENT,
			'auth_salt'                  => self::ENVIRONMENT,
			'logged_in_key'              => self::ENVIRONMENT,
			'logged_in_salt'             => self::ENVIRONMENT,
			'nonce_key'                  => self::ENVIRONMENT,
			'nonce_salt'                 => self::ENVIRONMENT,
			'secure_auth_key'            => self::ENVIRONMENT,
			'secure_auth_salt'           => self::ENVIRONMENT,
			'mailserver_url'             => self::ENVIRONMENT,
			'mailserver_login'           => self::ENVIRONMENT,
			'mailserver_pass'            => self::ENVIRONMENT,
			'mailserver_port'            => self::ENVIRONMENT,
			'upload_path'                => self::ENVIRONMENT,
			'upload_url_path'            => self::ENVIRONMENT,
			'et_automatic_updates_options' => self::ENVIRONMENT,
			'wonderful_sync_settings'    => self::ENVIRONMENT,
			'wonderful_sync_baseline'    => self::ENVIRONMENT,
			// Permalinks and discussion rules (moderation, registration, spam lists) are
			// administration of each site: they are never transferred.
			'permalink_structure' => self::ENVIRONMENT,
			'category_base' => self::ENVIRONMENT,
			'tag_base' => self::ENVIRONMENT,
			'close_comments_days_old' => self::ENVIRONMENT,
			'close_comments_for_old_posts' => self::ENVIRONMENT,
			'comment_max_links' => self::ENVIRONMENT,
			'comment_moderation' => self::ENVIRONMENT,
			'comment_previously_approved' => self::ENVIRONMENT,
			'comment_registration' => self::ENVIRONMENT,
			'comments_notify' => self::ENVIRONMENT,
			'default_comment_status' => self::ENVIRONMENT,
			'default_ping_status' => self::ENVIRONMENT,
			'default_pingback_flag' => self::ENVIRONMENT,
			'disallowed_keys' => self::ENVIRONMENT,
			'moderation_keys' => self::ENVIRONMENT,
			'moderation_notify' => self::ENVIRONMENT,
			'require_name_email' => self::ENVIRONMENT,
			'show_comments_cookies_opt_in' => self::ENVIRONMENT,
			'use_trackback' => self::ENVIRONMENT,

			// Core settings screens (reading, discussion, media, writing).
			'comment_order'                   => self::SITE,
			'comments_per_page'               => self::SITE,
			'default_category'                => self::SITE,
			'default_comments_page'           => self::SITE,
			'default_email_category'          => self::SITE,
			'default_link_category'           => self::SITE,
			'default_post_format'             => self::SITE,
			'image_default_align'             => self::SITE,
			'image_default_link_type'         => self::SITE,
			'image_default_size'              => self::SITE,
			'large_size_h'                    => self::SITE,
			'large_size_w'                    => self::SITE,
			'medium_large_size_h'             => self::SITE,
			'medium_large_size_w'             => self::SITE,
			'medium_size_h'                   => self::SITE,
			'medium_size_w'                   => self::SITE,
			'thumbnail_crop'                  => self::SITE,
			'thumbnail_size_h'                => self::SITE,
			'thumbnail_size_w'                => self::SITE,
			'page_comments'                   => self::SITE,
			'posts_per_rss'                   => self::SITE,
			'rss_use_excerpt'                 => self::SITE,
			'show_avatars'                    => self::SITE,
			'avatar_default'                  => self::SITE,
			'avatar_rating'                   => self::SITE,
			'start_of_week'                   => self::SITE,
			'sticky_posts'                    => self::SITE,
			'thread_comments'                 => self::SITE,
			'thread_comments_depth'           => self::SITE,
			'use_smilies'                     => self::SITE,
			'use_balanceTags'                 => self::SITE,
			'wp_attachment_pages_enabled'     => self::SITE,
			'wp_page_for_privacy_policy'      => self::SITE,
			'uploads_use_yearmonth_folders'   => self::SITE,
			'links_updated_date_format'       => self::SITE,
			'link_manager_enabled'            => self::SITE,
			'wp_notes_notify'                 => self::SITE,

			// blog_public is 0 on every staging copy – syncing it would deindex the live site.
			'blog_public'                     => self::ENVIRONMENT,
			// WordPress empties the ping list when search engines are discouraged (staging).
			'ping_sites'                      => self::ENVIRONMENT,
			// WooCommerce image sizes the theme writes on its own when it runs.
			'shop_catalog_image_size'         => self::ENVIRONMENT,
			'shop_single_image_size'          => self::ENVIRONMENT,
			'shop_thumbnail_image_size'       => self::ENVIRONMENT,
			'admin_email_lifespan'            => self::ENVIRONMENT,
			'auto_plugin_theme_update_emails' => self::ENVIRONMENT,
			'blog_charset'                    => self::ENVIRONMENT,
			'html_type'                       => self::ENVIRONMENT,
			'fresh_site'                      => self::ENVIRONMENT,
			'recovery_keys'                   => self::ENVIRONMENT,
			'recovery_mode_email_last_sent'   => self::ENVIRONMENT,
			'hack_file'                       => self::ENVIRONMENT,
			'finished_splitting_shared_terms' => self::ENVIRONMENT,
			'wp_force_deactivated_plugins'    => self::ENVIRONMENT,
			'can_compress_scripts'            => self::ENVIRONMENT,

			// Rebuilt by WordPress on its own.
			'rewrite_rules'                   => self::CACHE,
			'user_count'                      => self::CACHE,
			'recently_edited'                 => self::CACHE,
		),
		'prefix' => array(
			'theme_mods_'        => self::DESIGN,
			'widget_'            => self::SITE,
			'et_divi_'           => self::DESIGN,
			'et_pb_'             => self::DESIGN,

			'_transient_'        => self::CACHE,
			// Wonderful Sync's own state (connection, log, baseline) belongs to each site.
			'wonderful_sync_'    => self::ENVIRONMENT,
			'_site_transient_'   => self::CACHE,
			'et_core_'           => self::CACHE,
			'_et_'               => self::CACHE,
			// Per-form state flags Divi writes on its own (hash suffix).
			'et_pb_contact_form_' => self::CACHE,
			'et_pb_signup_'      => self::CACHE,
			'et_pb_cache_notice' => self::CACHE,
			// Written by ARMember on every request, with a timestamp in the name.
			'arm_is_another_sort_data_mismatched_' => self::CACHE,
			'et_schedule_'       => self::CACHE,
			'et_images_temp_'    => self::CACHE,
			'theme_switched'     => self::CACHE,

			// Divi account, support centre and safe mode belong to the installation.
			'divi_'              => self::ENVIRONMENT,
			'et_account_'        => self::ENVIRONMENT,
			'et_support_'        => self::ENVIRONMENT,
			'et_safe_mode_'      => self::ENVIRONMENT,
			'et_google_api_'     => self::ENVIRONMENT,
			'et_bfb_'            => self::DESIGN,
			'shop_'              => self::SITE,

			// Clone tooling (do-tools) and installation-bound plugins.
			'dt_'                => self::ENVIRONMENT,
			'wfls_'              => self::ENVIRONMENT,
			'fs_'                => self::ENVIRONMENT,
			'postman_'           => self::ENVIRONMENT,
			'jetpack_'           => self::ENVIRONMENT,
			'crontrol_'          => self::ENVIRONMENT,
			'mpsum'              => self::ENVIRONMENT,
			'MPSUM'              => self::ENVIRONMENT,
			'swift_'             => self::ENVIRONMENT,

			// Caches and licences of common plugins.
			'autoptimize_'       => self::ENVIRONMENT,
			'wpseo'              => self::SITE,
			'rank_math'          => self::SITE,
			'woocommerce_'       => self::SITE,
			'wordfence'          => self::ENVIRONMENT,
			'wf_'                => self::ENVIRONMENT,
			'wp_mail_smtp'       => self::ENVIRONMENT,
			'wonderful_smtp_'    => self::ENVIRONMENT,
			'ai1wm_'             => self::ENVIRONMENT,
			'action_scheduler_'  => self::USER_DATA,
			'_wc_session_'       => self::USER_DATA,
		),
	);

	/**
	 * Well-known plugins: option/table prefix => [plugin name, class, plugin slug].
	 *
	 * Lets the inventory name the owner even when the plugin is no longer
	 * installed (orphaned options are common on long-running sites).
	 *
	 * @var array<string, array{0: string, 1: string, 2: string}>
	 */
	private $known_plugins = array(
		'updraft_'            => array( 'UpdraftPlus', self::ENVIRONMENT, 'updraftplus' ),
		'updraftplus_'        => array( 'UpdraftPlus', self::ENVIRONMENT, 'updraftplus' ),
		'siteground_'         => array( 'SiteGround Optimizer', self::ENVIRONMENT, 'sg-cachepress' ),
		'sg_'                 => array( 'SiteGround Security', self::ENVIRONMENT, 'sg-security' ),
		'sgo_'                => array( 'SiteGround Optimizer', self::ENVIRONMENT, 'sg-cachepress' ),
		'sgs_'                => array( 'SiteGround Security', self::ENVIRONMENT, 'sg-security' ),
		'rsssl_'              => array( 'Really Simple Security', self::ENVIRONMENT, 'really-simple-ssl' ),
		'wpsupercache_'       => array( 'WP Super Cache', self::ENVIRONMENT, 'wp-super-cache' ),
		'wpsc_'               => array( 'WP Super Cache', self::ENVIRONMENT, 'wp-super-cache' ),
		'supercache_'         => array( 'WP Super Cache', self::ENVIRONMENT, 'wp-super-cache' ),
		'ossdl_'              => array( 'WP Super Cache (CDN)', self::ENVIRONMENT, 'wp-super-cache' ),
		'acui_'               => array( 'Import Users from CSV', self::ENVIRONMENT, 'import-users-from-csv-with-meta' ),
		'real_queue'          => array( 'devowl.io (Real Cookie Banner)', self::ENVIRONMENT, 'real-cookie-banner' ),
		'real_utils'          => array( 'devowl.io (Real Cookie Banner)', self::ENVIRONMENT, 'real-cookie-banner' ),
		'eum_'                => array( 'Easy Updates Manager', self::ENVIRONMENT, 'stops-core-theme-and-plugin-updates' ),
		'mpsum'               => array( 'Easy Updates Manager', self::ENVIRONMENT, 'stops-core-theme-and-plugin-updates' ),
		'wp-piwik'            => array( 'Connect Matomo', self::ENVIRONMENT, 'wp-piwik' ),
		'cmplz_'              => array( 'Complianz', self::SITE, 'complianz-gdpr' ),
		'rcb-'                => array( 'Real Cookie Banner', self::SITE, 'real-cookie-banner' ),
		'rcb_'                => array( 'Real Cookie Banner', self::SITE, 'real-cookie-banner' ),
		'cookielawinfo_'      => array( 'CookieYes', self::SITE, 'cookie-law-info' ),
		'cookie_notice_'      => array( 'Cookie Notice', self::SITE, 'cookie-notice' ),
		'duplicate_post_'     => array( 'Yoast Duplicate Post', self::SITE, 'duplicate-post' ),
		'arm_'                => array( 'ARMember', self::SITE, 'armember-membership' ),
		'newsletter_'         => array( 'Newsletter', self::SITE, 'newsletter' ),
		'wpcode_'             => array( 'WPCode', self::SITE, 'insert-headers-and-footers' ),
		'autodescription'     => array( 'The SEO Framework', self::SITE, 'autodescription' ),
		'the_seo_framework'   => array( 'The SEO Framework', self::SITE, 'autodescription' ),
		'omgf_'               => array( 'OMGF', self::SITE, 'host-webfonts-local' ),
		'yydev_tagmanager'    => array( 'Tag Manager (yydev)', self::SITE, 'yydev-tag-manager' ),
		'safelayout_'         => array( 'Safelayout Preloader', self::SITE, 'safelayout-elegant-preloader' ),
		'login_designer'      => array( 'Login Designer', self::SITE, 'login-designer' ),
		'monarch_'            => array( 'Monarch', self::SITE, 'monarch' ),
		'foogallery'          => array( 'FooGallery', self::SITE, 'foogallery' ),
		'wc_blocks_'          => array( 'WooCommerce', self::CACHE, 'woocommerce' ),
	);

	/**
	 * Tables of known plugins that hold user data, by prefix after the database prefix.
	 *
	 * @var array<string, string>
	 */
	private $known_user_tables = array(
		'arm_'         => 'ARMember',
		'newsletter'   => 'Newsletter',
		'rcb_consent'  => 'Real Cookie Banner',
		'rcb_stats'    => 'Real Cookie Banner',
		'cmplz_'       => 'Complianz',
		'sgs_log'      => 'SiteGround Security',
		'eum_logs'     => 'Easy Updates Manager',
	);

	/**
	 * Option names that look like secrets are always environment, whatever prefix they carry.
	 */
	/**
	 * Top-level keys of an option that describe the installation, not the design: Divi
	 * writes them itself whenever it runs (e.g. a newer Divi on staging). Bound to the
	 * option; never sent, the receiving site keeps its own values.
	 */
	const ENVIRONMENT_KEYS = array(
		'et_divi' => array(
			'divi_previous_installed_version',
			'divi_latest_installed_version',
			'divi_1_3_images',
			'et_pb_layouts_updated',
			'library_removed_legacy_layouts',
			'divi_email_provider_credentials_migrated',
		),
		'theme_mods_Divi' => array(
			'et_updated_layouts_built_for_post_types',
		),
	);

	/**
	 * Key prefixes per option that belong to the installation or to one editor (Divi keeps
	 * every Visual Builder user preference – toolbar, settings bar … – in et_divi).
	 */
	const ENVIRONMENT_PREFIXES = array(
		'et_divi' => array( 'et_fb_pref_' ),
	);

	const SECRET_PATTERN = '/(licen[cs]e|api[_-]?key|secret|token|password|passwd|_pass$|smtp|private[_-]?key|webhook|stripe|paypal|ppcp|mollie|klarna|braintree|square|gateway|merchant|client[_-]?id)/i';

	/**
	 * Post type rules.
	 *
	 * @var array<string, string>
	 */
	private $post_type_rules = array(
		'page'                => self::CONTENT,
		'post'                => self::CONTENT,
		'attachment'          => self::CONTENT,
		'wp_block'            => self::LAYOUT,
		'wp_template'         => self::LAYOUT,
		'wp_template_part'    => self::LAYOUT,
		'wp_navigation'       => self::LAYOUT,
		'wp_global_styles'    => self::DESIGN,
		'custom_css'          => self::DESIGN,
		'nav_menu_item'       => self::LAYOUT,

		// Divi.
		'et_pb_layout'        => self::LAYOUT,
		'et_theme_builder'    => self::LAYOUT,
		'et_template'         => self::LAYOUT,
		'et_header_layout'    => self::LAYOUT,
		'et_body_layout'      => self::LAYOUT,
		'et_footer_layout'    => self::LAYOUT,
		'et_code_snippet'     => self::LAYOUT,
		'et_tb_item'          => self::LAYOUT,

		// Flatsome UX Builder blocks.
		'blocks'              => self::LAYOUT,
		'et_theme_options'    => self::DESIGN,

		// Revisions and drafts the editor creates on its own.
		'revision'            => self::CACHE,
		'_et_pb_speculation'  => self::CACHE,
		'customize_changeset' => self::CACHE,
		'oembed_cache'        => self::CACHE,
		'user_request'        => self::USER_DATA,
		'wp_font_family'      => self::DESIGN,
		'wp_font_face'        => self::DESIGN,

		// Shop and form data live on the live site only.
		'shop_order'          => self::USER_DATA,
		'shop_order_refund'   => self::USER_DATA,
		'shop_order_placehold' => self::USER_DATA,
		'shop_subscription'   => self::USER_DATA,
		'shop_coupon'         => self::USER_DATA,
		'flamingo_inbound'    => self::USER_DATA,
		'flamingo_contact'    => self::USER_DATA,
		'nf_sub'              => self::USER_DATA,
		'wpcf7_contact_form'  => self::SITE,
		'product'             => self::CONTENT,
		'product_variation'   => self::CONTENT,
	);

	/**
	 * Post meta keys that are caches and must never travel.
	 *
	 * @var string[]
	 */
	private $cache_meta_prefixes = array(
		'_wonderful_sync_release',
		'_et_builder_post_features_cache',
		'_et_dynamic_cached_',
		'_divi_dynamic_assets_',
		'_et_pb_first_image',
		'_et_pb_truncate_post',
		'et_enqueued_post_fonts',
		'_et_builder_dynamic_assets_',
		'_et_pb_ab_',
		'_edit_lock',
		'_edit_last',
		'_wp_old_slug',
		'_wp_old_date',
		'_oembed_',
		'_encloseme',
		'_pingme',
	);

	/**
	 * Post meta written by live traffic (stock, sales, ratings). Kept on the target, never synced.
	 *
	 * @var string[]
	 */
	private $user_meta_keys = array(
		'_stock',
		'_stock_status',
		'total_sales',
		'_wc_average_rating',
		'_wc_rating_count',
		'_wc_review_count',
		'_wp_trash_meta_status',
		'_wp_trash_meta_time',
		'_wp_desired_post_slug',
	);

	/**
	 * Table rules without the database prefix.
	 *
	 * @var array<string, string>
	 */
	private $table_rules = array(
		'options'                  => self::SITE,
		'posts'                    => self::CONTENT,
		'postmeta'                 => self::CONTENT,
		'terms'                    => self::CONTENT,
		'term_taxonomy'            => self::CONTENT,
		'term_relationships'       => self::CONTENT,
		'termmeta'                 => self::CONTENT,
		'links'                    => self::CONTENT,
		'users'                    => self::USER_DATA,
		'usermeta'                 => self::USER_DATA,
		'comments'                 => self::USER_DATA,
		'commentmeta'              => self::USER_DATA,
		'wc_orders'                => self::USER_DATA,
		'wc_orders_meta'           => self::USER_DATA,
		'wc_order_addresses'       => self::USER_DATA,
		'wc_order_operational_data' => self::USER_DATA,
		'wc_order_stats'           => self::USER_DATA,
		'wc_order_product_lookup'  => self::USER_DATA,
		'wc_customer_lookup'       => self::USER_DATA,
		'woocommerce_sessions'     => self::USER_DATA,
		'woocommerce_order_items'  => self::USER_DATA,
		'woocommerce_order_itemmeta' => self::USER_DATA,
		'woocommerce_payment_tokens' => self::USER_DATA,
		'woocommerce_api_keys'     => self::ENVIRONMENT,
		'actionscheduler_actions'  => self::USER_DATA,
		'actionscheduler_logs'     => self::USER_DATA,
		'actionscheduler_claims'   => self::USER_DATA,
		'actionscheduler_groups'   => self::USER_DATA,
	);

	/**
	 * Table prefixes (after the database prefix) for plugin tables.
	 *
	 * @var array<string, string>
	 */
	private $table_prefix_rules = array(
		'wf'           => self::USER_DATA,
		'gf_'          => self::USER_DATA,
		'rg_'          => self::USER_DATA,
		'wpforms_'     => self::USER_DATA,
		'e_submissions' => self::USER_DATA,
		'yoast_'       => self::CACHE,
		'rank_math_'   => self::CACHE,
		'redirection_' => self::SITE,
		'wc_'          => self::USER_DATA,
	);

	/**
	 * Classifies an option by name.
	 *
	 * @param string $name Option name.
	 */
	public function option( string $name ): string {
		if ( isset( $this->option_rules['exact'][ $name ] ) ) {
			$class = $this->option_rules['exact'][ $name ];
		} elseif ( preg_match( self::SECRET_PATTERN, $name ) ) {
			$class = self::ENVIRONMENT;
		} else {
			$class = $this->match_prefix( $name, $this->option_rules['prefix'] );
			if ( self::UNASSIGNED === $class ) {
				$known = $this->known_plugin( $name );
				$class = $known ? $known[1] : self::UNASSIGNED;
			}
		}

		/**
		 * Filters the sync class of an option.
		 *
		 * @param string $class One of the Classifier constants.
		 * @param string $name  Option name.
		 * @param string $kind  'option', 'post_type', 'meta' or 'table'.
		 */
		return (string) apply_filters( 'wonderful_sync_classify', $class, $name, 'option' );
	}

	/**
	 * Classifies a post type. Unknown public post types count as content.
	 *
	 * @param string $post_type Post type name.
	 */
	public function post_type( string $post_type ): string {
		if ( in_array( $post_type, Pods::STRUCTURE, true ) ) {
			// Pods, groups and fields: layouts, unless switched off in the settings.
			$class = Pods::structure_enabled() ? self::LAYOUT : self::UNASSIGNED;
		} elseif ( isset( $this->post_type_rules[ $post_type ] ) ) {
			$class = $this->post_type_rules[ $post_type ];
		} else {
			$object = get_post_type_object( $post_type );
			$class  = ( $object && $object->public ) ? self::CONTENT : self::UNASSIGNED;
		}

		return (string) apply_filters( 'wonderful_sync_classify', $class, $post_type, 'post_type' );
	}

	/**
	 * Classifies a post meta key. Everything that is not a cache or live data travels with its post.
	 *
	 * @param string $key Meta key.
	 */
	public function meta( string $key ): string {
		// MySQL compares meta keys case-insensitively, so the rules do too.
		$lower = strtolower( trim( $key ) );
		$class = in_array( $lower, $this->user_meta_keys, true ) ? self::USER_DATA : self::CONTENT;
		foreach ( $this->cache_meta_prefixes as $prefix ) {
			if ( 0 === strpos( $lower, strtolower( $prefix ) ) ) {
				$class = self::CACHE;
				break;
			}
		}

		return (string) apply_filters( 'wonderful_sync_classify', $class, $key, 'meta' );
	}

	/**
	 * Classifies a database table.
	 *
	 * @param string $table     Full table name.
	 * @param string $db_prefix Database prefix of this site.
	 */
	public function table( string $table, string $db_prefix ): string {
		if ( '' !== $db_prefix && 0 !== strpos( $table, $db_prefix ) ) {
			$class = self::UNASSIGNED;
		} else {
			$short = substr( $table, strlen( $db_prefix ) );
			$class = $this->table_rules[ $short ] ?? $this->match_prefix( $short, $this->table_prefix_rules );
			if ( self::UNASSIGNED === $class ) {
				$user  = $this->match_prefix( $short, array_fill_keys( array_keys( $this->known_user_tables ), self::USER_DATA ) );
				$known = $this->known_plugin( $short );
				$class = self::UNASSIGNED !== $user ? $user : ( $known ? $known[1] : self::UNASSIGNED );
			}
		}

		return (string) apply_filters( 'wonderful_sync_classify', $class, $table, 'table' );
	}

	/**
	 * Well-known plugin that owns this option or table name, if any.
	 *
	 * @param string $name Option name or table name without the database prefix.
	 * @return array{0: string, 1: string, 2: string}|null [plugin name, class, plugin slug].
	 */
	public function known_plugin( string $name ): ?array {
		$best = '';
		foreach ( array_keys( $this->known_plugins ) as $prefix ) {
			if ( 0 === strpos( $name, $prefix ) && strlen( $prefix ) > strlen( $best ) ) {
				$best = $prefix;
			}
		}

		return '' === $best ? null : $this->known_plugins[ $best ];
	}

	/**
	 * Classifies a must-use plugin. The do-tools clone helpers belong to the clone only.
	 *
	 * @param string $file Must-use plugin file name.
	 */
	public function mu_plugin( string $file ): string {
		$class = ( 0 === strpos( $file, 'dt-' ) || 'docker-wp-cron-loopback.php' === $file ) ? self::ENVIRONMENT : self::CODE;

		return (string) apply_filters( 'wonderful_sync_classify', $class, $file, 'mu_plugin' );
	}

	/**
	 * Classifies a taxonomy: menus are layout, public taxonomies content, everything else
	 * (internal taxonomies of plugins, product visibility flags …) is never synced.
	 *
	 * @param string $taxonomy Taxonomy name.
	 */
	public function taxonomy( string $taxonomy ): string {
		if ( 'nav_menu' === $taxonomy ) {
			$class = self::LAYOUT;
		} elseif ( in_array( $taxonomy, array( 'category', 'post_tag', 'post_format', 'wp_pattern_category', 'layout_category', 'layout_tag', 'layout_pack', 'layout_type', 'scope', 'module_width' ), true ) ) {
			$class = self::CONTENT;
		} else {
			$object = get_taxonomy( $taxonomy );
			$class  = ( $object && $object->public ) ? self::CONTENT : self::UNASSIGNED;
		}

		return (string) apply_filters( 'wonderful_sync_classify', $class, $taxonomy, 'taxonomy' );
	}

	/**
	 * Whether a nested array key looks like a secret (API key, licence, password …).
	 *
	 * @param string $key Array key.
	 */
	public static function is_secret_key( string $key ): bool {
		return (bool) preg_match( self::SECRET_PATTERN, $key );
	}

	/**
	 * Installation keys of an option (see ENVIRONMENT_KEYS).
	 *
	 * @param string $option Option name.
	 * @return string[]
	 */
	public static function environment_keys( string $option, array $values = array() ): array {
		$keys = self::ENVIRONMENT_KEYS[ $option ] ?? array();
		foreach ( self::ENVIRONMENT_PREFIXES[ $option ] ?? array() as $prefix ) {
			foreach ( $values as $value ) {
				foreach ( is_array( $value ) ? array_keys( $value ) : array() as $key ) {
					if ( is_string( $key ) && 0 === strpos( $key, $prefix ) ) {
						$keys[] = $key;
					}
				}
			}
		}

		return array_values( array_unique( $keys ) );
	}

	/**
	 * Keys whose masked value means "never sent": secret-looking keys and the installation
	 * keys above. Used where a mask is ignored for comparisons.
	 *
	 * @param string $key Array key.
	 */
	public static function is_masked_key( string $key ): bool {
		if ( self::is_secret_key( $key ) ) {
			return true;
		}
		foreach ( self::ENVIRONMENT_KEYS as $keys ) {
			if ( in_array( $key, $keys, true ) ) {
				return true;
			}
		}
		foreach ( self::ENVIRONMENT_PREFIXES as $prefixes ) {
			foreach ( $prefixes as $prefix ) {
				if ( 0 === strpos( $key, $prefix ) ) {
					return true;
				}
			}
		}

		return false;
	}

	/**
	 * Whether objects of this class may be part of a changeset.
	 *
	 * @param string $class Sync class.
	 */
	public static function is_syncable( string $class ): bool {
		return in_array( $class, self::SYNCABLE, true );
	}

	/**
	 * Human readable labels, in display order.
	 *
	 * @return array<string, string>
	 */
	public static function labels(): array {
		return array(
			self::CODE        => __( 'Code (themes, plugins)', 'wonderful-sync' ),
			self::DESIGN      => __( 'Design (Divi options, presets, global colors)', 'wonderful-sync' ),
			self::LAYOUT      => __( 'Layouts (Theme Builder, Divi Library, menus)', 'wonderful-sync' ),
			self::CONTENT     => __( 'Content (pages, posts, media)', 'wonderful-sync' ),
			self::SITE        => __( 'Site settings', 'wonderful-sync' ),
			self::ENVIRONMENT => __( 'Environment (never transferred)', 'wonderful-sync' ),
			self::USER_DATA   => __( 'User data (never transferred)', 'wonderful-sync' ),
			self::CACHE       => __( 'Caches (cleared, never transferred)', 'wonderful-sync' ),
			self::UNASSIGNED  => __( 'Unassigned (never transferred automatically)', 'wonderful-sync' ),
		);
	}

	/**
	 * Returns the class of the longest matching prefix, or UNASSIGNED.
	 *
	 * @param string                $name  Name to test.
	 * @param array<string, string> $rules Prefix => class.
	 */
	private function match_prefix( string $name, array $rules ): string {
		$best = '';
		foreach ( array_keys( $rules ) as $prefix ) {
			if ( 0 === strpos( $name, $prefix ) && strlen( $prefix ) > strlen( $best ) ) {
				$best = $prefix;
			}
		}

		return '' === $best ? self::UNASSIGNED : $rules[ $best ];
	}
}