<?php
/**
 * Language settings.
 *
 * @package SiteLangWC
 */

namespace SiteLangWC;

defined( 'ABSPATH' ) || exit;

/**
 * Handles enabled language configuration and current language state.
 */
final class Languages {
	/**
	 * Language option names.
	 */
	private const LANGUAGES_OPTION          = 'sitelang_languages';
	private const LANGUAGES_BACKUP_OPTION   = 'sitelang_languages_backup';
	private const LANGUAGES_CHECKSUM_OPTION = 'sitelang_languages_checksum';
	private const LANGUAGES_RECOVERY_OPTION = 'sitelang_languages_recovered_at';

	/**
	 * Current frontend language code.
	 *
	 * @var string|null
	 */
	private $current_language = null;

	/**
	 * Built-in language suggestions.
	 *
	 * Flag codes reference SiteLang's bundled SVG allowlist.
	 *
	 * @var array<string,array<string,mixed>>
	 */
	private $presets = array(
		'af' => array( 'english_label' => 'Afrikaans', 'native_label' => 'Afrikaans', 'flag' => 'za', 'rtl' => 0, 'wp_locale' => 'af' ),
		'sq' => array( 'english_label' => 'Albanian', 'native_label' => 'Shqip', 'flag' => 'al', 'rtl' => 0, 'wp_locale' => 'sq' ),
		'am' => array( 'english_label' => 'Amharic', 'native_label' => 'Amharic', 'flag' => 'et', 'rtl' => 0, 'wp_locale' => 'am' ),
		'ar' => array( 'english_label' => 'Arabic', 'native_label' => 'العربية', 'flag' => 'sa', 'rtl' => 1, 'wp_locale' => 'ar' ),
		'hy' => array( 'english_label' => 'Armenian', 'native_label' => 'Հայերեն', 'flag' => 'am', 'rtl' => 0, 'wp_locale' => 'hy' ),
		'az' => array( 'english_label' => 'Azerbaijani', 'native_label' => 'Azərbaycan dili', 'flag' => 'az', 'rtl' => 0, 'wp_locale' => 'az' ),
		'eu' => array( 'english_label' => 'Basque', 'native_label' => 'Euskara', 'flag' => 'es', 'rtl' => 0, 'wp_locale' => 'eu' ),
		'be' => array( 'english_label' => 'Belarusian', 'native_label' => 'Беларуская', 'flag' => 'by', 'rtl' => 0, 'wp_locale' => 'bel' ),
		'bn' => array( 'english_label' => 'Bengali', 'native_label' => 'বাংলা', 'flag' => 'bd', 'rtl' => 0, 'wp_locale' => 'bn_BD' ),
		'bs' => array( 'english_label' => 'Bosnian', 'native_label' => 'Bosanski', 'flag' => 'ba', 'rtl' => 0, 'wp_locale' => 'bs_BA' ),
		'bg' => array( 'english_label' => 'Bulgarian', 'native_label' => 'Български', 'flag' => 'bg', 'rtl' => 0, 'wp_locale' => 'bg_BG' ),
		'ca' => array( 'english_label' => 'Catalan', 'native_label' => 'Català', 'flag' => 'es', 'rtl' => 0, 'wp_locale' => 'ca' ),
		'zh' => array( 'english_label' => 'Chinese (Simplified)', 'native_label' => '简体中文', 'flag' => 'cn', 'rtl' => 0, 'wp_locale' => 'zh_CN' ),
		'zh-tw' => array( 'english_label' => 'Chinese (Traditional)', 'native_label' => '繁體中文', 'flag' => 'tw', 'rtl' => 0, 'wp_locale' => 'zh_TW' ),
		'hr' => array( 'english_label' => 'Croatian', 'native_label' => 'Hrvatski', 'flag' => 'hr', 'rtl' => 0, 'wp_locale' => 'hr' ),
		'cs' => array( 'english_label' => 'Czech', 'native_label' => 'Čeština', 'flag' => 'cz', 'rtl' => 0, 'wp_locale' => 'cs_CZ' ),
		'da' => array( 'english_label' => 'Danish', 'native_label' => 'Dansk', 'flag' => 'dk', 'rtl' => 0, 'wp_locale' => 'da_DK' ),
		'nl' => array( 'english_label' => 'Dutch', 'native_label' => 'Nederlands', 'flag' => 'nl', 'rtl' => 0, 'wp_locale' => 'nl_NL' ),
		'et' => array( 'english_label' => 'Estonian', 'native_label' => 'Eesti', 'flag' => 'ee', 'rtl' => 0, 'wp_locale' => 'et' ),
		'fa' => array( 'english_label' => 'Persian', 'native_label' => 'فارسی', 'flag' => 'ir', 'rtl' => 1, 'wp_locale' => 'fa_IR' ),
		'fi' => array( 'english_label' => 'Finnish', 'native_label' => 'Suomi', 'flag' => 'fi', 'rtl' => 0, 'wp_locale' => 'fi' ),
		'fr' => array( 'english_label' => 'French', 'native_label' => 'Français', 'flag' => 'fr', 'rtl' => 0, 'wp_locale' => 'fr_FR' ),
		'ka' => array( 'english_label' => 'Georgian', 'native_label' => 'ქართული', 'flag' => 'ge', 'rtl' => 0, 'wp_locale' => 'ka_GE' ),
		'de' => array( 'english_label' => 'German', 'native_label' => 'Deutsch', 'flag' => 'de', 'rtl' => 0, 'wp_locale' => 'de_DE' ),
		'el' => array( 'english_label' => 'Greek', 'native_label' => 'Ελληνικά', 'flag' => 'gr', 'rtl' => 0, 'wp_locale' => 'el' ),
		'en' => array( 'english_label' => 'English', 'native_label' => 'English', 'flag' => 'us', 'rtl' => 0, 'wp_locale' => 'en_US' ),
		'gu' => array( 'english_label' => 'Gujarati', 'native_label' => 'ગુજરાતી', 'flag' => 'in', 'rtl' => 0, 'wp_locale' => 'gu' ),
		'he' => array( 'english_label' => 'Hebrew', 'native_label' => 'עברית', 'flag' => 'il', 'rtl' => 1, 'wp_locale' => 'he_IL' ),
		'hi' => array( 'english_label' => 'Hindi', 'native_label' => 'हिन्दी', 'flag' => 'in', 'rtl' => 0, 'wp_locale' => 'hi_IN' ),
		'hu' => array( 'english_label' => 'Hungarian', 'native_label' => 'Magyar', 'flag' => 'hu', 'rtl' => 0, 'wp_locale' => 'hu_HU' ),
		'is' => array( 'english_label' => 'Icelandic', 'native_label' => 'Íslenska', 'flag' => 'is', 'rtl' => 0, 'wp_locale' => 'is_IS' ),
		'id' => array( 'english_label' => 'Indonesian', 'native_label' => 'Bahasa Indonesia', 'flag' => 'id', 'rtl' => 0, 'wp_locale' => 'id_ID' ),
		'ga' => array( 'english_label' => 'Irish', 'native_label' => 'Gaeilge', 'flag' => 'ie', 'rtl' => 0, 'wp_locale' => 'ga' ),
		'it' => array( 'english_label' => 'Italian', 'native_label' => 'Italiano', 'flag' => 'it', 'rtl' => 0, 'wp_locale' => 'it_IT' ),
		'ja' => array( 'english_label' => 'Japanese', 'native_label' => '日本語', 'flag' => 'jp', 'rtl' => 0, 'wp_locale' => 'ja' ),
		'ko' => array( 'english_label' => 'Korean', 'native_label' => '한국어', 'flag' => 'kr', 'rtl' => 0, 'wp_locale' => 'ko_KR' ),
		'lv' => array( 'english_label' => 'Latvian', 'native_label' => 'Latviešu', 'flag' => 'lv', 'rtl' => 0, 'wp_locale' => 'lv' ),
		'lt' => array( 'english_label' => 'Lithuanian', 'native_label' => 'Lietuvių', 'flag' => 'lt', 'rtl' => 0, 'wp_locale' => 'lt_LT' ),
		'ms' => array( 'english_label' => 'Malay', 'native_label' => 'Bahasa Melayu', 'flag' => 'my', 'rtl' => 0, 'wp_locale' => 'ms_MY' ),
		'mr' => array( 'english_label' => 'Marathi', 'native_label' => 'मराठी', 'flag' => 'in', 'rtl' => 0, 'wp_locale' => 'mr' ),
		'no' => array( 'english_label' => 'Norwegian', 'native_label' => 'Norsk', 'flag' => 'no', 'rtl' => 0, 'wp_locale' => 'nb_NO' ),
		'ps' => array( 'english_label' => 'Pashto', 'native_label' => 'پښتو', 'flag' => 'af', 'rtl' => 1, 'wp_locale' => 'ps' ),
		'pl' => array( 'english_label' => 'Polish', 'native_label' => 'Polski', 'flag' => 'pl', 'rtl' => 0, 'wp_locale' => 'pl_PL' ),
		'pt' => array( 'english_label' => 'Portuguese', 'native_label' => 'Português', 'flag' => 'pt', 'rtl' => 0, 'wp_locale' => 'pt_PT' ),
		'pt-br' => array( 'english_label' => 'Portuguese (Brazil)', 'native_label' => 'Português do Brasil', 'flag' => 'br', 'rtl' => 0, 'wp_locale' => 'pt_BR' ),
		'ro' => array( 'english_label' => 'Romanian', 'native_label' => 'Română', 'flag' => 'ro', 'rtl' => 0, 'wp_locale' => 'ro_RO' ),
		'ru' => array( 'english_label' => 'Russian', 'native_label' => 'Русский', 'flag' => 'ru', 'rtl' => 0, 'wp_locale' => 'ru_RU' ),
		'sr' => array( 'english_label' => 'Serbian', 'native_label' => 'Српски', 'flag' => 'rs', 'rtl' => 0, 'wp_locale' => 'sr_RS' ),
		'sk' => array( 'english_label' => 'Slovak', 'native_label' => 'Slovenčina', 'flag' => 'sk', 'rtl' => 0, 'wp_locale' => 'sk_SK' ),
		'sl' => array( 'english_label' => 'Slovenian', 'native_label' => 'Slovenščina', 'flag' => 'si', 'rtl' => 0, 'wp_locale' => 'sl_SI' ),
		'es' => array( 'english_label' => 'Spanish', 'native_label' => 'Español', 'flag' => 'es', 'rtl' => 0, 'wp_locale' => 'es_ES' ),
		'sw' => array( 'english_label' => 'Swahili', 'native_label' => 'Kiswahili', 'flag' => 'ke', 'rtl' => 0, 'wp_locale' => 'sw' ),
		'sv' => array( 'english_label' => 'Swedish', 'native_label' => 'Svenska', 'flag' => 'se', 'rtl' => 0, 'wp_locale' => 'sv_SE' ),
		'ta' => array( 'english_label' => 'Tamil', 'native_label' => 'தமிழ்', 'flag' => 'in', 'rtl' => 0, 'wp_locale' => 'ta_IN' ),
		'te' => array( 'english_label' => 'Telugu', 'native_label' => 'తెలుగు', 'flag' => 'in', 'rtl' => 0, 'wp_locale' => 'te' ),
		'th' => array( 'english_label' => 'Thai', 'native_label' => 'ไทย', 'flag' => 'th', 'rtl' => 0, 'wp_locale' => 'th' ),
		'tr' => array( 'english_label' => 'Turkish', 'native_label' => 'Türkçe', 'flag' => 'tr', 'rtl' => 0, 'wp_locale' => 'tr_TR' ),
		'uk' => array( 'english_label' => 'Ukrainian', 'native_label' => 'Українська', 'flag' => 'ua', 'rtl' => 0, 'wp_locale' => 'uk' ),
		'ur' => array( 'english_label' => 'Urdu', 'native_label' => 'اردو', 'flag' => 'pk', 'rtl' => 1, 'wp_locale' => 'ur' ),
		'uz' => array( 'english_label' => 'Uzbek', 'native_label' => 'Oʻzbekcha', 'flag' => 'uz', 'rtl' => 0, 'wp_locale' => 'uz_UZ' ),
		'vi' => array( 'english_label' => 'Vietnamese', 'native_label' => 'Tiếng Việt', 'flag' => 'vn', 'rtl' => 0, 'wp_locale' => 'vi' ),
		'cy' => array( 'english_label' => 'Welsh', 'native_label' => 'Cymraeg', 'flag' => 'gb', 'rtl' => 0, 'wp_locale' => 'cy' ),
	);

	/**
	 * Map short language codes to WordPress locale identifiers.
	 *
	 * @var array<string,string>
	 */
	private $wp_locale_map = array(
		'en' => 'en_US',
		'de' => 'de_DE',
		'es' => 'es_ES',
		'fr' => 'fr_FR',
		'ar' => 'ar',
	);

	/**
	 * Minimal frontend UI fallback dictionary for common commerce strings.
	 *
	 * Used only when translated text still equals source text.
	 *
	 * @var array<string,array<string,string>>
	 */
	private $ui_fallback_dictionary = array(
		'de' => array(
			'Add to cart'          => 'In den Warenkorb',
			'Read more'            => 'Mehr erfahren',
			'Select options'       => 'Optionen auswählen',
			'View cart'            => 'Warenkorb ansehen',
			'Proceed to checkout'  => 'Zur Kasse',
			'Checkout'             => 'Kasse',
			'Place order'          => 'Bestellung aufgeben',
			'Buy now'              => 'Jetzt kaufen',
			'Related products'     => 'Ähnliche Produkte',
			'You may also like'    => 'Das könnte Ihnen auch gefallen',
			'Out of stock'         => 'Nicht vorrätig',
			'In stock'             => 'Auf Lager',
			'People watching this product now!' => 'Personen sehen sich dieses Produkt gerade an!',
		),
		'es' => array(
			'Add to cart'          => 'Añadir al carrito',
			'Read more'            => 'Leer más',
			'Select options'       => 'Seleccionar opciones',
			'View cart'            => 'Ver carrito',
			'Proceed to checkout'  => 'Finalizar compra',
			'Checkout'             => 'Pagar',
			'Place order'          => 'Realizar pedido',
			'Buy now'              => 'Comprar ahora',
			'Related products'     => 'Productos relacionados',
			'You may also like'    => 'También te puede gustar',
			'Out of stock'         => 'Agotado',
			'In stock'             => 'En stock',
			'People watching this product now!' => 'Personas están viendo este producto ahora!',
		),
		'fr' => array(
			'Add to cart'          => 'Ajouter au panier',
			'Read more'            => 'En savoir plus',
			'Select options'       => 'Choisir les options',
			'View cart'            => 'Voir le panier',
			'Proceed to checkout'  => 'Passer à la caisse',
			'Checkout'             => 'Paiement',
			'Place order'          => 'Passer la commande',
			'Buy now'              => 'Acheter maintenant',
			'Related products'     => 'Produits similaires',
			'You may also like'    => 'Vous aimerez aussi',
			'Out of stock'         => 'Rupture de stock',
			'In stock'             => 'En stock',
			'People watching this product now!' => 'Des personnes regardent ce produit en ce moment !',
		),
		'ar' => array(
			'Add to cart'          => 'أضف إلى السلة',
			'Read more'            => 'اقرأ المزيد',
			'Select options'       => 'اختر الخيارات',
			'View cart'            => 'عرض السلة',
			'Proceed to checkout'  => 'متابعة الدفع',
			'Checkout'             => 'الدفع',
			'Place order'          => 'إتمام الطلب',
			'Buy now'              => 'اشتر الآن',
			'Related products'     => 'منتجات ذات صلة',
			'You may also like'    => 'قد يعجبك أيضًا',
			'Out of stock'         => 'غير متوفر',
			'In stock'             => 'متوفر',
			'People watching this product now!' => 'أشخاص يشاهدون هذا المنتج الآن!',
		),
	);

	/**
	 * Register hooks.
	 *
	 * @return void
	 */
	public function init() {
		$this->ensure_options();
		add_filter( 'determine_locale', array( $this, 'filter_determine_locale' ), 20 );
		add_filter( 'gettext', array( $this, 'filter_gettext_fallback' ), 20, 3 );
		add_filter( 'the_content', array( $this, 'filter_rendered_html_fallback' ), 20 );
		add_filter( 'elementor/frontend/the_content', array( $this, 'filter_rendered_html_fallback' ), 20 );
		add_filter( 'woocommerce_short_description', array( $this, 'filter_rendered_html_fallback' ), 20 );
		add_filter( 'language_attributes', array( $this, 'filter_language_attributes' ) );
		add_filter( 'body_class', array( $this, 'body_classes' ) );
	}

	/**
	 * Ensure options exist even after restoring a production database.
	 *
	 * @return void
	 */
	private function ensure_options() {
		$this->ensure_language_integrity();

		if ( false === get_option( 'sitelang_settings', false ) ) {
			add_option( 'sitelang_settings', $this->get_default_settings(), '', false );
			return;
		}

		$settings = $this->get_settings();
		$merged   = array_merge( $this->get_default_settings(), $settings );
		if ( false === get_option( 'sitelang_manual_switcher_placement_migrated', false ) ) {
			$legacy_hook = ! empty( $merged['hook_name'] ) && 'woodmart_after_header' === $merged['hook_name'];
			if ( ! empty( $merged['hook_enabled'] ) && $legacy_hook ) {
				$merged['hook_enabled'] = 0;
				$merged['hook_name']    = '';
			}
			add_option( 'sitelang_manual_switcher_placement_migrated', 1, '', false );
		}

		if ( $merged !== $settings ) {
			update_option( 'sitelang_settings', $merged, false );
		}
	}

	/**
	 * Get enabled language rows.
	 *
	 * @return array<string,array<string,mixed>>
	 */
	public function get_enabled() {
		$languages = get_option( self::LANGUAGES_OPTION, array() );
		return is_array( $languages ) ? $languages : array();
	}

	/**
	 * Get enabled language codes.
	 *
	 * @return array<int,string>
	 */
	public function get_enabled_codes() {
		return array_keys( $this->get_enabled() );
	}

	/**
	 * Get language data by code.
	 *
	 * @param string $code Language code.
	 * @return array<string,mixed>|null
	 */
	public function get_language( $code ) {
		$code      = $this->sanitize_code( $code );
		$languages = $this->get_enabled();
		return isset( $languages[ $code ] ) ? $languages[ $code ] : null;
	}

	/**
	 * Is language enabled.
	 *
	 * @param string $code Language code.
	 * @return bool
	 */
	public function is_enabled( $code ) {
		return null !== $this->get_language( $code );
	}

	/**
	 * Get default language code.
	 *
	 * @return string
	 */
	public function get_default_code() {
		$settings = $this->get_settings();
		return ! empty( $settings['default_language'] ) ? $this->sanitize_code( $settings['default_language'] ) : 'en';
	}

	/**
	 * Get default language label.
	 *
	 * @return string
	 */
	public function get_default_label() {
		$settings = $this->get_settings();
		$presets = $this->get_presets();
		$default = $presets[ $this->get_default_code() ]['english_label'] ?? 'English';
		return ! empty( $settings['default_label'] ) ? sanitize_text_field( $settings['default_label'] ) : $default;
	}

	/**
	 * Get default language native label.
	 *
	 * @return string
	 */
	public function get_default_native_label() {
		$settings = $this->get_settings();
		$presets = $this->get_presets();
		$default = $presets[ $this->get_default_code() ]['native_label'] ?? $this->get_default_label();
		return ! empty( $settings['default_native'] ) ? sanitize_text_field( $settings['default_native'] ) : $default;
	}

	/**
	 * Get all languages including default.
	 *
	 * @return array<string,array<string,mixed>>
	 */
	public function get_all() {
		$settings     = $this->get_settings();
		$default_code = $this->get_default_code();
		$all          = array(
			$default_code => array(
				'code'          => $default_code,
				'english_label' => $this->get_default_label(),
				'native_label'  => $this->get_default_native_label(),
				'flag'          => ! empty( $settings['default_flag'] ) ? sanitize_text_field( $settings['default_flag'] ) : ( $this->presets[ $default_code ]['flag'] ?? 'us' ),
				'rtl'           => isset( $settings['default_rtl'] ) ? (int) $settings['default_rtl'] : (int) ( $this->presets[ $default_code ]['rtl'] ?? 0 ),
				'wp_locale'     => $this->presets[ $default_code ]['wp_locale'] ?? '',
				'is_default'    => 1,
			),
		);

		foreach ( $this->get_enabled() as $code => $language ) {
			$language['code']       = $code;
			$language['is_default'] = 0;
			$all[ $code ]          = $language;
		}

		return $all;
	}

	/**
	 * Save enabled languages.
	 *
	 * @param array<int,array<string,mixed>> $rows Posted rows.
	 * @param bool                          $allow_empty Allow every added language to be disabled.
	 * @return true|\WP_Error
	 */
	public function save_languages( array $rows, $allow_empty = false ) {
		$languages = $this->normalize_languages( $rows );
		$current   = $this->get_enabled();
		if ( empty( $languages ) && ! empty( $current ) && ! $allow_empty ) {
			return new \WP_Error(
				'sitelang_languages_empty_not_confirmed',
				__( 'SiteLang prevented all languages from being removed. Confirm the remove-all option if this is intentional.', 'sitelang' )
			);
		}

		$this->persist_languages( $languages );
		update_option( 'sitelang_rewrite_flush_needed', 1, false );
		update_option( 'sitelang_hard_rewrite_flush_needed', 1, false );

		return true;
	}

	/**
	 * Validate language rows and normalize them by code.
	 *
	 * Accepts both form rows and the associative format used by settings exports.
	 *
	 * @param array<mixed> $rows Language rows.
	 * @return array<string,array<string,mixed>>
	 */
	public function normalize_languages( array $rows ) {
		$languages = array();

		foreach ( $rows as $row_key => $row ) {
			if ( ! is_array( $row ) ) {
				continue;
			}

			$raw_code = isset( $row['code'] ) ? $row['code'] : ( is_string( $row_key ) ? $row_key : '' );
			$code     = $this->sanitize_code( $raw_code );

			if ( '' === $code || $code === $this->get_default_code() ) {
				continue;
			}

			$preset = isset( $this->presets[ $code ] ) ? $this->presets[ $code ] : array();

			$languages[ $code ] = array(
				'code'          => $code,
				'english_label' => isset( $row['english_label'] ) && '' !== trim( (string) $row['english_label'] ) ? sanitize_text_field( $row['english_label'] ) : ( $preset['english_label'] ?? strtoupper( $code ) ),
				'native_label'  => isset( $row['native_label'] ) && '' !== trim( (string) $row['native_label'] ) ? sanitize_text_field( $row['native_label'] ) : ( $preset['native_label'] ?? strtoupper( $code ) ),
				'flag'          => isset( $row['flag'] ) && '' !== trim( (string) $row['flag'] ) ? sanitize_key( $row['flag'] ) : ( $preset['flag'] ?? '' ),
				'rtl'           => ! empty( $row['rtl'] ) ? 1 : 0,
				'wp_locale'     => isset( $row['wp_locale'] ) && '' !== trim( (string) $row['wp_locale'] ) ? sanitize_text_field( $row['wp_locale'] ) : ( $preset['wp_locale'] ?? '' ),
			);
		}

		ksort( $languages );
		return $languages;
	}

	/**
	 * Restore an unexpectedly missing/corrupt registry from a last-known-good
	 * copy or, on upgrade, from authoritative translation relationships.
	 *
	 * @return void
	 */
	private function ensure_language_integrity() {
		$raw             = get_option( self::LANGUAGES_OPTION, false );
		$backup          = get_option( self::LANGUAGES_BACKUP_OPTION, false );
		$stored_checksum = (string) get_option( self::LANGUAGES_CHECKSUM_OPTION, '' );
		$languages       = is_array( $raw ) ? $this->normalize_languages( $raw ) : array();
		$backup          = is_array( $backup ) ? $this->normalize_languages( $backup ) : array();

		if ( ! empty( $languages ) ) {
			$checksum = $this->languages_checksum( $languages );

			// Initialize integrity metadata for installs upgraded from an older release.
			if ( '' === $stored_checksum ) {
				$this->persist_languages( $languages );
				return;
			}

			// An out-of-band or interrupted write changed only the primary option.
			// Restore the last complete registry when its checksum is still valid.
			if ( $checksum !== $stored_checksum && ! empty( $backup ) && $this->languages_checksum( $backup ) === $stored_checksum ) {
				$this->persist_languages( $backup );
				$this->record_language_recovery( 'checksum' );
				return;
			}

			if ( $checksum === $stored_checksum && ( $languages !== $raw || $backup !== $languages ) ) {
				$this->persist_languages( $languages );
			}
			return;
		}

		if ( ! empty( $backup ) ) {
			$this->persist_languages( $backup );
			$this->record_language_recovery( 'backup' );
			return;
		}

		// Existing installs did not have integrity metadata. Recover their language
		// codes once from mappings instead of leaving valid translations unreachable.
		if ( '' === $stored_checksum ) {
			$discovered = $this->discover_mapped_languages();
			$this->persist_languages( $discovered );
			if ( ! empty( $discovered ) ) {
				$this->record_language_recovery( 'mappings' );
			}
			return;
		}

		// A checksum for an empty registry records an intentional remove-all save.
		$this->persist_languages( array() );
	}

	/**
	 * Persist the primary registry and its recovery metadata together.
	 *
	 * @param array<string,array<string,mixed>> $languages Languages.
	 * @return void
	 */
	private function persist_languages( array $languages ) {
		update_option( self::LANGUAGES_OPTION, $languages, false );
		update_option( self::LANGUAGES_BACKUP_OPTION, $languages, false );
		update_option( self::LANGUAGES_CHECKSUM_OPTION, $this->languages_checksum( $languages ), false );
	}

	/**
	 * Build a stable checksum for the normalized registry.
	 *
	 * @param array<string,array<string,mixed>> $languages Languages.
	 * @return string
	 */
	private function languages_checksum( array $languages ) {
		return hash( 'sha256', (string) wp_json_encode( $languages ) );
	}

	/**
	 * Discover language codes already used by mapped translations.
	 *
	 * @return array<string,array<string,mixed>>
	 */
	private function discover_mapped_languages() {
		global $wpdb;

		$codes = array();
		$table = $wpdb->prefix . 'sitelang_translations';

		if ( $table === $wpdb->get_var( $wpdb->prepare( 'SHOW TABLES LIKE %s', $wpdb->esc_like( $table ) ) ) ) {
			$mapped_codes = $wpdb->get_col( $wpdb->prepare( "SELECT DISTINCT language_code FROM %i WHERE language_code <> ''", $table ) );
			$codes        = is_array( $mapped_codes ) ? $mapped_codes : array();
		}

		if ( empty( $codes ) ) {
			$meta_codes = $wpdb->get_col(
				$wpdb->prepare(
					"SELECT DISTINCT meta_value FROM {$wpdb->postmeta} WHERE meta_key = %s AND meta_value <> ''",
					'_sitelang_language'
				)
			);
			$codes = is_array( $meta_codes ) ? $meta_codes : array();
		}

		$rows = array();
		foreach ( $codes as $code ) {
			$code = $this->sanitize_code( $code );
			if ( '' === $code || $code === $this->get_default_code() ) {
				continue;
			}
			$rows[ $code ] = array( 'code' => $code );
		}

		return $this->normalize_languages( $rows );
	}

	/**
	 * Record a recovery for an administrator-facing notice and diagnostics.
	 *
	 * @param string $source Recovery source.
	 * @return void
	 */
	private function record_language_recovery( $source ) {
		update_option( 'sitelang_rewrite_flush_needed', 1, false );
		update_option( 'sitelang_hard_rewrite_flush_needed', 1, false );
		update_option(
			self::LANGUAGES_RECOVERY_OPTION,
			array(
				'time'   => time(),
				'source' => sanitize_key( $source ),
			),
			false
		);
	}

	/**
	 * Get settings.
	 *
	 * @return array<string,mixed>
	 */
	public function get_settings() {
		$settings = get_option( 'sitelang_settings', array() );
		return is_array( $settings ) ? $settings : array();
	}

	/**
	 * Default plugin settings.
	 *
	 * @return array<string,mixed>
	 */
	public function get_default_settings() {
		return array(
			'default_language'          => 'en',
			'default_label'             => 'English',
			'default_native'            => 'English',
			'default_flag'              => 'us',
			'switcher_mode'             => 'dropdown',
			'switcher_preset'           => 'minimal',
			'switcher_show_flag'        => 1,
			'switcher_show_name'        => 0,
			'switcher_radius'           => 6,
			'switcher_bg'               => '#ffffff',
			'switcher_text'             => '#1f2937',
			'switcher_accent'           => '#b68b2d',
			'switcher_custom_hover'     => 0,
			'switcher_hover_bg'         => '#eaf3f5',
			'switcher_hover_text'       => '#045f78',
			'switcher_placement'        => 'header-floating',
			'hook_enabled'              => 0,
			'hook_name'                 => '',
			'mobile_switcher_enabled'   => 0,
			'mobile_switcher_mode'      => 'dropdown',
			'mobile_switcher_target'    => '',
			'homepages'                 => array(),
			'auto_publish_system_pages' => 0,
			'merchant_exclude_translated_display_ads' => 1,
		);
	}

	/**
	 * Save settings.
	 *
	 * @param array<string,mixed> $settings Settings to merge.
	 * @return void
	 */
	public function save_settings( array $settings ) {
		$current = $this->get_settings();
		update_option( 'sitelang_settings', array_merge( $current, $settings ), false );
	}

	/** Save the source language and its display metadata. */
	public function save_default_language( $code ) {
		$code    = $this->sanitize_code( $code );
		$presets = $this->get_presets();
		if ( '' === $code || ! isset( $presets[ $code ] ) ) {
			return new \WP_Error( 'sitelang_invalid_default_language', __( 'Choose a valid original language.', 'sitelang' ) );
		}

		$preset = $presets[ $code ];
		$this->save_settings(
			array(
				'default_language' => $code,
				'default_label'    => $preset['english_label'],
				'default_native'   => $preset['native_label'],
				'default_flag'     => $preset['flag'],
				'default_rtl'      => ! empty( $preset['rtl'] ) ? 1 : 0,
			)
		);

		return true;
	}

	/**
	 * Get language presets.
	 *
	 * @return array<string,array<string,mixed>>
	 */
	public function get_presets() {
		return $this->presets;
	}

	/**
	 * Set current language.
	 *
	 * @param string $code Language code.
	 * @return void
	 */
	public function set_current( $code ) {
		$this->current_language = $this->sanitize_code( $code );
	}

	/**
	 * Get current language.
	 *
	 * @return string
	 */
	public function get_current() {
		return $this->current_language ? $this->current_language : $this->get_default_code();
	}

	/**
	 * Is current language RTL.
	 *
	 * @param string|null $code Optional language code.
	 * @return bool
	 */
	public function is_rtl( $code = null ) {
		$code = $code ? $this->sanitize_code( $code ) : $this->get_current();
		if ( $code === $this->get_default_code() ) {
			$all = $this->get_all();
			return ! empty( $all[ $code ]['rtl'] );
		}
		$lang = $this->get_language( $code );

		return $lang ? ! empty( $lang['rtl'] ) : false;
	}

	/**
	 * Sanitize language code.
	 *
	 * @param string $code Language code.
	 * @return string
	 */
	public function sanitize_code( $code ) {
		return strtolower( preg_replace( '/[^a-zA-Z0-9_-]/', '', (string) $code ) );
	}

	/**
	 * Add lang and dir attributes.
	 *
	 * @param string $output Language attributes.
	 * @return string
	 */
	public function filter_language_attributes( $output ) {
		if ( $this->should_bypass_frontend_language_filters() ) {
			return $output;
		}

		$current = $this->get_current();
		$output  = preg_replace( '/\s?lang=("|\')[^"\']*("|\')/', '', $output );
		$output  = preg_replace( '/\s?dir=("|\')[^"\']*("|\')/', '', $output );
		$output .= ' lang="' . esc_attr( str_replace( '_', '-', $current ) ) . '"';
		$output .= ' dir="' . ( $this->is_rtl( $current ) ? 'rtl' : 'ltr' ) . '"';

		return trim( $output );
	}

	/**
	 * Add frontend body classes.
	 *
	 * @param array<int,string> $classes Body classes.
	 * @return array<int,string>
	 */
	public function body_classes( $classes ) {
		if ( $this->should_bypass_frontend_language_filters() ) {
			return $classes;
		}

		$current   = $this->get_current();
		$classes[] = 'sitelang-language';
		$classes[] = 'lang-' . sanitize_html_class( $current );

		if ( $this->is_rtl( $current ) ) {
			$classes[] = 'rtl-language';
		}

		return $classes;
	}

	/**
	 * Force frontend locale from current SiteLang language.
	 *
	 * @param string $locale Existing locale.
	 * @return string
	 */
	public function filter_determine_locale( $locale ) {
		if ( $this->should_bypass_frontend_language_filters() ) {
			return $locale;
		}

		$language = $this->resolve_frontend_language();
		if ( ! $language || $language === $this->get_default_code() ) {
			return $locale;
		}

		$mapped = $this->map_language_to_wp_locale( $language );
		return $mapped ? $mapped : $locale;
	}

	/**
	 * Translate common frontend commerce strings when no textdomain translation is available.
	 *
	 * @param string $translated Already translated text.
	 * @param string $text Original text.
	 * @param string $domain Text domain.
	 * @return string
	 */
	public function filter_gettext_fallback( $translated, $text, $domain ) {
		if ( $this->should_bypass_frontend_language_filters() || '' === $text ) {
			return $translated;
		}

		$language = $this->resolve_frontend_language();
		if ( ! $language || $language === $this->get_default_code() ) {
			return $translated;
		}

		if ( $translated !== $text ) {
			return $translated;
		}

		$dictionary = isset( $this->ui_fallback_dictionary[ $language ] ) ? $this->ui_fallback_dictionary[ $language ] : array();
		if ( isset( $dictionary[ $text ] ) ) {
			return $dictionary[ $text ];
		}

		return $translated;
	}

	/**
	 * Fallback replacement for hardcoded frontend widget strings.
	 *
	 * Some builder/theme widgets print raw HTML strings that never hit gettext.
	 *
	 * @param string $html Rendered HTML.
	 * @return string
	 */
	public function filter_rendered_html_fallback( $html ) {
		if ( $this->should_bypass_frontend_language_filters() || ! is_string( $html ) || '' === $html ) {
			return $html;
		}

		$language = $this->resolve_frontend_language();
		if ( ! $language || $language === $this->get_default_code() ) {
			return $html;
		}

		$dictionary = isset( $this->ui_fallback_dictionary[ $language ] ) ? $this->ui_fallback_dictionary[ $language ] : array();
		if ( empty( $dictionary ) ) {
			return $html;
		}

		return strtr( $html, $dictionary );
	}

	/**
	 * Get active frontend language from current state or request path.
	 *
	 * @return string
	 */
	private function resolve_frontend_language() {
		$current = $this->get_current();
		if ( $current && $current !== $this->get_default_code() && $this->is_enabled( $current ) ) {
			return $this->sanitize_code( $current );
		}

		if ( $this->is_frontend_woocommerce_ajax() ) {
			$referrer_language = $this->get_frontend_referrer_language();
			if ( null !== $referrer_language ) {
				return $referrer_language;
			}
		}

		$request_uri = isset( $_SERVER['REQUEST_URI'] ) ? sanitize_text_field( wp_unslash( $_SERVER['REQUEST_URI'] ) ) : '';
		if ( '' === $request_uri ) {
			return $this->get_default_code();
		}

		$path = wp_parse_url( $request_uri, PHP_URL_PATH );
		if ( ! is_string( $path ) || '' === $path ) {
			return $this->get_default_code();
		}

		$parts = array_values( array_filter( explode( '/', trim( $path, '/' ) ) ) );
		if ( empty( $parts ) ) {
			return $this->get_default_code();
		}

		$candidate = $this->sanitize_code( $parts[0] );
		return $this->is_enabled( $candidate ) ? $candidate : $this->get_default_code();
	}

	/**
	 * Avoid language rewrites/translations during admin, auth, AJAX, REST, and cron requests.
	 *
	 * @return bool
	 */
	private function should_bypass_frontend_language_filters() {
		if ( $this->is_frontend_woocommerce_ajax() ) {
			return false;
		}

		if ( is_admin() || ( defined( 'DOING_CRON' ) && DOING_CRON ) ) {
			return true;
		}

		if ( function_exists( 'wp_doing_ajax' ) && wp_doing_ajax() ) {
			return true;
		}

		if ( defined( 'REST_REQUEST' ) && REST_REQUEST ) {
			return true;
		}

		global $pagenow;
		if ( isset( $pagenow ) && in_array( $pagenow, array( 'wp-login.php', 'wp-register.php' ), true ) ) {
			return true;
		}

		$script = isset( $_SERVER['SCRIPT_NAME'] ) ? sanitize_text_field( wp_unslash( $_SERVER['SCRIPT_NAME'] ) ) : '';
		$uri    = isset( $_SERVER['REQUEST_URI'] ) ? sanitize_text_field( wp_unslash( $_SERVER['REQUEST_URI'] ) ) : '';

		return false !== strpos( $script, 'wp-login.php' )
			|| false !== strpos( $uri, '/wp-login.php' )
			|| false !== strpos( $uri, '/wp-admin/' );
	}

	/**
	 * Whether the current AJAX request belongs to the customer-facing store.
	 *
	 * @return bool
	 */
	private function is_frontend_woocommerce_ajax() {
		if ( defined( 'WC_AJAX' ) && WC_AJAX ) {
			return true;
		}

		if ( ! empty( $_REQUEST['wc-ajax'] ) ) { // phpcs:ignore WordPress.Security.NonceVerification.Recommended -- Read-only request context.
			return true;
		}

		if ( ! function_exists( 'wp_doing_ajax' ) || ! wp_doing_ajax() ) {
			return false;
		}

		return null !== $this->get_frontend_referrer_language();
	}

	/**
	 * Resolve an internal frontend referrer to its explicit language context.
	 *
	 * @return string|null
	 */
	private function get_frontend_referrer_language() {
		$referrer = wp_get_referer();
		if ( ! $referrer && ! empty( $_SERVER['HTTP_REFERER'] ) ) {
			$referrer = esc_url_raw( wp_unslash( $_SERVER['HTTP_REFERER'] ) );
		}

		if ( ! $referrer ) {
			return null;
		}

		$home_parts     = wp_parse_url( home_url( '/' ) );
		$referrer_parts = wp_parse_url( $referrer );
		if ( empty( $home_parts['host'] ) || empty( $referrer_parts['host'] ) || strtolower( $home_parts['host'] ) !== strtolower( $referrer_parts['host'] ) ) {
			return null;
		}

		$path      = isset( $referrer_parts['path'] ) ? trim( $referrer_parts['path'], '/' ) : '';
		$home_path = isset( $home_parts['path'] ) ? trim( $home_parts['path'], '/' ) : '';
		if ( '' !== $home_path && ( $path === $home_path || 0 === strpos( $path, $home_path . '/' ) ) ) {
			$path = ltrim( substr( $path, strlen( $home_path ) ), '/' );
		}

		$first_segment = strtok( $path, '/' );
		if ( in_array( $first_segment, array( 'wp-admin', 'wp-login.php', 'wp-json' ), true ) ) {
			return null;
		}

		$candidate = $this->sanitize_code( $first_segment ? $first_segment : '' );
		return $candidate && $this->is_enabled( $candidate ) ? $candidate : $this->get_default_code();
	}

	/**
	 * Map SiteLang language code to WordPress locale.
	 *
	 * @param string $language_code Language code.
	 * @return string
	 */
	private function map_language_to_wp_locale( $language_code ) {
		$language_code = $this->sanitize_code( $language_code );
		if ( isset( $this->wp_locale_map[ $language_code ] ) ) {
			return $this->wp_locale_map[ $language_code ];
		}

		$language = $this->get_language( $language_code );
		if ( is_array( $language ) && ! empty( $language['wp_locale'] ) ) {
			return sanitize_text_field( $language['wp_locale'] );
		}

		return '';
	}
}