<?php
/**
 * @package Polylang
 */

use WP_Syntex\Polylang\Capabilities\Capabilities;

/**
 * Setup features available on all admin pages.
 *
 * @since 1.8
 */
abstract class PLL_Admin_Base extends PLL_Base {
	/**
	 * @since 3.8
	 */
	public const SCREEN_PREFIX = 'languages';

	/**
	 * Current language (used to filter the content).
	 *
	 * @var PLL_Language|null
	 */
	public $curlang;

	/**
	 * Language selected in the admin language filter.
	 *
	 * @var PLL_Language|null
	 */
	public $filter_lang;

	/**
	 * Preferred language to assign to new contents.
	 *
	 * @var PLL_Language|null
	 */
	public $pref_lang;

	/**
	 * @var PLL_Filters_Links|null
	 */
	public $filters_links;

	/**
	 * @var PLL_Admin_Links|null
	 */
	public $links;

	/**
	 * @var PLL_Admin_Notices|null
	 */
	public $notices;

	/**
	 * @var PLL_Admin_Static_Pages|null
	 */
	public $static_pages;

	/**
	 * @var PLL_Admin_Default_Term|null
	 */
	public $default_term;

	/**
	 * Setups actions needed on all admin pages.
	 *
	 * @since 1.8
	 *
	 * @param PLL_Links_Model $links_model Reference to the links model.
	 */
	public function __construct( &$links_model ) {
		parent::__construct( $links_model );

		// Adds the link to the languages panel in the WordPress admin menu
		add_action( 'admin_menu', array( $this, 'add_menus' ) );

		add_action( 'admin_menu', array( $this, 'remove_customize_submenu' ) );

		// Setup js scripts and css styles
		add_action( 'admin_enqueue_scripts', array( $this, 'admin_enqueue_scripts' ), 0 ); // High priority in case an ajax request is sent by an immediately invoked function

		add_action( 'customize_controls_enqueue_scripts', array( $this, 'customize_controls_enqueue_scripts' ) );

		// Early instantiated to be able to correctly initialize language properties.
		$this->static_pages = new PLL_Admin_Static_Pages( $this );
		$this->model->set_languages_ready();
	}

	/**
	 * Setups filters and action needed on all admin pages and on plugins page
	 * Loads the settings pages or the filters base on the request
	 *
	 * @since 1.2
	 */
	public function init() {
		parent::init();

		$this->notices = new PLL_Admin_Notices( $this );

		$this->default_term = new PLL_Admin_Default_Term( $this );
		$this->default_term->add_hooks();

		if ( ! $this->model->has_languages() ) {
			return;
		}

		$this->links = new PLL_Admin_Links( $this ); // FIXME needed here ?
		$this->filters_links = new PLL_Filters_Links( $this ); // FIXME needed here ?

		// Filter admin language for users
		// We must not call user info before WordPress defines user roles in wp-settings.php
		add_action( 'setup_theme', array( $this, 'init_user' ) );
		add_filter( 'request', array( $this, 'request' ) );

		// Adds the languages in admin bar
		add_action( 'admin_bar_menu', array( $this, 'admin_bar_menu' ), 100 ); // 100 determines the position
	}

	/**
	 * Adds links to Polylang's admin panels to the WordPress admin menu.
	 *
	 * @since 0.1
	 *
	 * @return void
	 */
	public function add_menus(): void {
		global $admin_page_hooks;

		$parent    = '';
		$first_tab = '';

		foreach ( $this->get_menu_items() as $tab => $title ) {
			$page = self::get_screen_slug( $tab );
			$capa = $this->get_menu_capability( $tab );

			if ( empty( $parent ) ) {
				$parent    = $page;
				$first_tab = $tab;

				/*
				 * WP actually doesn't care about the user capability used here, as long as it has sub-menus: it will
				 * use the ones from the sub-menus. See `_wp_menu_output()`.
				 * Ex: a user with `manage_translations` will still be able to access the Translations page, even if the
				 * main menu has `manage_options`.
				 */
				add_menu_page( $title, __( 'Languages', 'polylang' ), $capa, $parent, '__return_null', 'dashicons-translation' );
				$admin_page_hooks[ $parent ] = self::SCREEN_PREFIX; // Hack to avoid the localization of the hook name. See: https://core.trac.wordpress.org/ticket/18857
			}

			add_submenu_page( $parent, $title, $title, $capa, $page, array( $this, 'languages_page' ) );
		}

		/*
		 * Get rid of the `toplevel` prefix in hook names.
		 *
		 * In the WP admin, if an admin screen is the first of its menu (like the PLL's "Languages" screen), the hooks
		 * fired in the screen get a `toplevel` prefix (ex: `toplevel_page_mlang`) while all the other screens get a
		 * slug based on the parent screen title (ex: `languages_page_mlang_strings`, where `languages` is the parent
		 * screen's slug). This will not prevent the `toplevel` hooks to fire, but it will fire the `languages` hooks in
		 * addition: this way, screens can be removed or moved around without the need of hooking both prefixes: using
		 * the hooks with the `languages` prefix will work in both cases.
		 *
		 * @see get_plugin_page_hookname()
		 */
		foreach ( array( 'load-', 'admin_print_styles-', 'admin_print_scripts-', 'admin_head-', '', 'admin_print_footer_scripts-', 'admin_footer-' ) as $prefix ) {
			add_action(
				"{$prefix}toplevel_page_{$parent}",
				static function () use ( $prefix, $first_tab ) {
					do_action( $prefix . self::get_screen_id( $first_tab ) );
				}
			);
		}

		/*
		 * Ensure a common CSS class to the `<body>` tag.
		 *
		 * Due to the `toplevel` "issue" described earlier, the CSS class `toplevel_page_mlang` (for example) is added
		 * to the body. This adds a class with the `languages` prefix. This ensures we have a common CSS class, even if
		 * the screen is moved to the 1st position in the menu.
		 */
		add_action(
			// Target the screen in 1st position only.
			"admin_head-toplevel_page_{$parent}",
			static function () use ( $first_tab ) {
				add_filter(
					'admin_body_class',
					static function ( $admin_body_classes ) use ( $first_tab ) {
						return $admin_body_classes . ' ' . self::get_screen_id( $first_tab );
					}
				);
			}
		);

		/**
		 * Also modify the screen ID and base.
		 *
		 * Note: the global variables `$page_hook` and `$hook_suffix` are not changed, their value is still
		 * `toplevel_page_mlang`. Changing them breaks things because we can't filter `get_plugin_page_hookname()`.
		 * This is why the above hooks are still needed.
		 */
		add_action(
			'current_screen',
			static function ( $current_screen ) use ( $parent, $first_tab ) {
				if ( "toplevel_page_{$parent}" !== $current_screen->id ) {
					return;
				}

				$current_screen->id   = self::get_screen_id( $first_tab );
				$current_screen->base = self::get_screen_id( $first_tab );
			}
		);
	}

	/**
	 * Dummy method to display the 3 tabs pages: languages, strings translations, settings.
	 * Overwritten in `PLL_Settings`.
	 *
	 * @since 3.7
	 *
	 * @return void
	 */
	public function languages_page() {}

	/**
	 * Setup js scripts & css styles ( only on the relevant pages )
	 *
	 * @since 0.6
	 *
	 * @return void
	 */
	public function admin_enqueue_scripts() {
		$suffix = defined( 'SCRIPT_DEBUG' ) && SCRIPT_DEBUG ? '' : '.min';

		wp_enqueue_script( 'pll_admin', plugins_url( "/js/build/admin{$suffix}.js", POLYLANG_ROOT_FILE ), array( 'jquery' ), POLYLANG_VERSION, true );
		$inline_script = sprintf( 'let pll_admin = %s;', wp_json_encode( array( 'ajax_filter' => $this->get_ajax_filter_data() ) ) );
		wp_add_inline_script( 'pll_admin', $inline_script, 'before' );

		$screen = get_current_screen();
		if ( empty( $screen ) ) {
			return;
		}

		/*
		 * For each script:
		 * 0 => the pages on which to load the script
		 * 1 => the scripts it needs to work
		 * 2 => true if loaded even if languages have not been defined yet, false otherwise
		 * 3 => true if loaded in footer
		 */
		$scripts = array(
			'user'    => array( array( 'profile', 'user-edit' ), array( 'jquery' ), false, false ),
			'widgets' => array( array( 'widgets' ), array( 'jquery' ), false, false ),
		);

		$block_screens = array( 'widgets', 'site-editor' );

		if ( ! empty( $screen->post_type ) && $this->model->is_translated_post_type( $screen->post_type ) ) {
			$scripts['post'] = array( array( 'edit' ), array( 'jquery', 'wp-ajax-response' ), false, true );

			// Classic editor.
			if ( ! method_exists( $screen, 'is_block_editor' ) || ! $screen->is_block_editor() ) {
				$scripts['classic-editor'] = array( array( 'post', 'media', 'async-upload' ), array( 'jquery', 'wp-ajax-response', 'post', 'jquery-ui-dialog', 'wp-i18n' ), false, true );
			}

			// Block editor with legacy metabox in WP 5.0+.
			$block_screens[] = 'post';
		}

		if ( $this->options['media_support'] ) {
			$scripts['media'] = array( array( 'upload' ), array( 'jquery' ), false, true );
		}

		if ( $this->is_block_editor( $screen ) ) {
			$scripts['block-editor'] = array( $block_screens, array( 'jquery', 'wp-ajax-response', 'wp-api-fetch', 'jquery-ui-dialog', 'wp-i18n' ), false, true );
		}

		if ( ! empty( $screen->taxonomy ) && $this->model->is_translated_taxonomy( $screen->taxonomy ) ) {
			$scripts['term'] = array( array( 'edit-tags', 'term' ), array( 'jquery', 'wp-ajax-response', 'jquery-ui-autocomplete' ), false, true );
		}

		foreach ( $scripts as $script => $v ) {
			if ( in_array( $screen->base, $v[0] ) && ( $v[2] || $this->model->has_languages() ) ) {
				wp_enqueue_script( "pll_{$script}", plugins_url( "/js/build/{$script}{$suffix}.js", POLYLANG_ROOT_FILE ), $v[1], POLYLANG_VERSION, $v[3] );
				if ( 'classic-editor' === $script || 'block-editor' === $script ) {
					wp_set_script_translations( "pll_{$script}", 'polylang' );
				}
			}
		}

		wp_register_style( 'polylang_admin', plugins_url( "/css/build/admin{$suffix}.css", POLYLANG_ROOT_FILE ), array( 'wp-jquery-ui-dialog' ), POLYLANG_VERSION );
		wp_enqueue_style( 'polylang_dialog', plugins_url( "/css/build/dialog{$suffix}.css", POLYLANG_ROOT_FILE ), array( 'polylang_admin' ), POLYLANG_VERSION );

		$this->add_inline_scripts();
	}

	/**
	 * Tells whether or not the given screen is block editor kind.
	 * e.g. widget, site or post editor.
	 *
	 * @since 3.3
	 *
	 * @param WP_Screen $screen Screen object.
	 * @return bool True if the screen is a block editor, false otherwise.
	 */
	protected function is_block_editor( $screen ) {
		return method_exists( $screen, 'is_block_editor' ) && $screen->is_block_editor() && ! pll_use_block_editor_plugin();
	}

	/**
	 * Enqueue scripts to the WP Customizer.
	 *
	 * @since 2.4.0
	 *
	 * @return void
	 */
	public function customize_controls_enqueue_scripts() {
		if ( $this->model->has_languages() ) {
			$suffix = defined( 'SCRIPT_DEBUG' ) && SCRIPT_DEBUG ? '' : '.min';
			wp_enqueue_script( 'pll_widgets', plugins_url( '/js/build/widgets' . $suffix . '.js', POLYLANG_ROOT_FILE ), array( 'jquery' ), POLYLANG_VERSION, true );
			$this->add_inline_scripts();
		}
	}

	/**
	 * Adds inline scripts to set the default language in JS
	 * and localizes scripts.
	 *
	 * @since 3.3
	 *
	 * @return void
	 */
	private function add_inline_scripts() {
		if ( wp_script_is( 'pll_block-editor', 'enqueued' ) ) {
			$default_lang_script = 'const pllDefaultLanguage = "' . $this->options['default_lang'] . '";';
			wp_add_inline_script(
				'pll_block-editor',
				$default_lang_script,
				'before'
			);
		}
		if ( wp_script_is( 'pll_widgets', 'enqueued' ) ) {
			wp_localize_script(
				'pll_widgets',
				'pll_widgets',
				array(
					'flags' => wp_list_pluck( $this->model->get_languages_list(), 'flag', 'slug' ),
				)
			);
		}
	}

	/**
	 * Returns the data to use with the AJAX filter.
	 * The final goal is to detect if an ajax request is made on admin or frontend.
	 *
	 * Takes care to various situations:
	 * - When the AJAX request has no `options.data` thanks to ScreenfeedFr.
	 *   See: https://wordpress.org/support/topic/ajaxprefilter-may-not-work-as-expected.
	 * - When `options.data` is a JSON string.
	 *   See: https://wordpress.org/support/topic/polylang-breaking-third-party-ajax-requests-on-admin-panels.
	 * - When `options.data` is an empty string (GET request with the method 'load').
	 *   See: https://wordpress.org/support/topic/invalid-url-during-wordpress-new-dashboard-widget-operation.
	 *
	 * @since 3.7
	 *
	 * @return array
	 */
	public function get_ajax_filter_data(): array {
		global $post, $tag;

		$params = array( 'pll_ajax_backend' => 1 );
		if ( $post instanceof WP_Post && $this->model->post_types->is_translated( $post->post_type ) ) {
			$params['pll_post_id'] = $post->ID;
		}

		if ( $tag instanceof WP_Term && $this->model->taxonomies->is_translated( $tag->taxonomy ) ) {
			$params['pll_term_id'] = $tag->term_id;
		}

		/**
		 * Filters the list of parameters to add to the admin ajax request.
		 *
		 * @since 3.4.5
		 *
		 * @param array $params List of parameters to add to the admin ajax request.
		 */
		return (array) apply_filters( 'pll_admin_ajax_params', $params );
	}

	/**
	 * Sets the admin current language, used to filter the content
	 *
	 * @since 2.0
	 *
	 * @return void
	 */
	public function set_current_language() {
		$this->curlang = $this->filter_lang;

		// Edit Post
		if ( isset( $_REQUEST['pll_post_id'] ) && $lang = $this->model->post->get_language( (int) $_REQUEST['pll_post_id'] ) ) { // phpcs:ignore WordPress.Security.NonceVerification
			$this->curlang = $lang;
		} elseif ( 'post.php' === $GLOBALS['pagenow'] && isset( $_GET['post'] ) && $this->model->is_translated_post_type( get_post_type( (int) $_GET['post'] ) ) && $lang = $this->model->post->get_language( (int) $_GET['post'] ) ) { // phpcs:ignore WordPress.Security.NonceVerification
			$this->curlang = $lang;
		} elseif ( 'post-new.php' === $GLOBALS['pagenow'] && ( empty( $_GET['post_type'] ) || $this->model->is_translated_post_type( sanitize_key( $_GET['post_type'] ) ) ) ) { // phpcs:ignore WordPress.Security.NonceVerification
			$this->curlang = empty( $_GET['new_lang'] ) ? $this->pref_lang : $this->model->get_language( sanitize_key( $_GET['new_lang'] ) ); // phpcs:ignore WordPress.Security.NonceVerification
		}

		// Edit Term
		elseif ( isset( $_REQUEST['pll_term_id'] ) && $lang = $this->model->term->get_language( (int) $_REQUEST['pll_term_id'] ) ) { // phpcs:ignore WordPress.Security.NonceVerification
			$this->curlang = $lang;
		} elseif ( in_array( $GLOBALS['pagenow'], array( 'edit-tags.php', 'term.php' ) ) && isset( $_GET['taxonomy'] ) && $this->model->is_translated_taxonomy( sanitize_key( $_GET['taxonomy'] ) ) ) { // phpcs:ignore WordPress.Security.NonceVerification
			if ( isset( $_GET['tag_ID'] ) && $lang = $this->model->term->get_language( (int) $_GET['tag_ID'] ) ) { // phpcs:ignore WordPress.Security.NonceVerification
				$this->curlang = $lang;
			} elseif ( ! empty( $_GET['new_lang'] ) ) { // phpcs:ignore WordPress.Security.NonceVerification
				$this->curlang = $this->model->get_language( sanitize_key( $_GET['new_lang'] ) ); // phpcs:ignore WordPress.Security.NonceVerification
			} elseif ( empty( $this->curlang ) ) {
				$this->curlang = $this->pref_lang;
			}
		}

		// Ajax
		if ( wp_doing_ajax() && ! empty( $_REQUEST['lang'] ) ) { // phpcs:ignore WordPress.Security.NonceVerification
			$this->curlang = $this->model->get_language( sanitize_key( $_REQUEST['lang'] ) ); // phpcs:ignore WordPress.Security.NonceVerification
		}

		/**
		 * Filters the current language used by Polylang in the admin context.
		 *
		 * @since 3.2
		 *
		 * @param PLL_Language|false|null $curlang  Instance of the current language.
		 * @param PLL_Admin_Base          $polylang Instance of the main Polylang's object.
		 */
		$this->curlang = apply_filters( 'pll_admin_current_language', $this->curlang, $this );

		// Inform that the admin language has been set.
		if ( $this->curlang instanceof PLL_Language ) {
			/** This action is documented in src/frontend/choose-lang.php */
			do_action( 'pll_language_defined', $this->curlang->slug, $this->curlang );
		} else {
			/** This action is documented in src/class-polylang.php */
			do_action( 'pll_no_language_defined' ); // To load overridden textdomains.
		}
	}

	/**
	 * Defines the backend language and the admin language filter based on user preferences.
	 *
	 * @since 1.2.3
	 *
	 * @return void
	 */
	public function init_user() {
		/*
		 *  $_GET['lang'] is numeric when editing a language, not when selecting a new language in the filter.
		 *  We intentionally don't use a nonce to update the language filter.
		 */
		if ( ! wp_doing_ajax() && ! empty( $_GET['lang'] ) && ! is_numeric( sanitize_key( $_GET['lang'] ) ) ) { // phpcs:ignore WordPress.Security.NonceVerification
			$user_id = get_current_user_id();
			if ( current_user_can( 'edit_user', $user_id ) ) {
				$lang = $this->model->get_language( sanitize_key( $_GET['lang'] ) ); // phpcs:ignore WordPress.Security.NonceVerification
				update_user_meta( $user_id, 'pll_filter_content', $lang ? $lang->slug : '' );
			}
		}

		$this->filter_lang = $this->model->get_language( get_user_meta( get_current_user_id(), 'pll_filter_content', true ) );

		// Set preferred language for use when saving posts and terms: must not be empty.
		$this->pref_lang = empty( $this->filter_lang ) ? $this->model->get_default_language() : $this->filter_lang;

		/**
		 * Filters the preferred language on admin side.
		 * The preferred language is used for example to determine the language of a new post.
		 *
		 * @since 1.2.3
		 *
		 * @param PLL_Language $pref_lang Preferred language.
		 */
		$this->pref_lang = apply_filters( 'pll_admin_preferred_language', $this->pref_lang );

		$this->set_current_language();
	}

	/**
	 * Avoids parsing a tax query when all languages are requested
	 * Fixes https://wordpress.org/support/topic/notice-undefined-offset-0-in-wp-includesqueryphp-on-line-3877 introduced in WP 4.1
	 *
	 * @see https://core.trac.wordpress.org/ticket/31246 the suggestion of @boonebgorges.
	 *
	 * @since 1.6.5
	 *
	 * @param array $qvars The array of requested query variables.
	 * @return array
	 */
	public function request( $qvars ) {
		if ( isset( $qvars['lang'] ) && 'all' === $qvars['lang'] ) {
			unset( $qvars['lang'] );
		}

		return $qvars;
	}

	/**
	 * Adds the languages list in admin bar for the admin languages filter.
	 *
	 * @since 0.9
	 *
	 * @param WP_Admin_Bar $wp_admin_bar WP_Admin_Bar global object.
	 * @return void
	 */
	public function admin_bar_menu( $wp_admin_bar ) {
		$all_item = (object) array(
			'slug' => 'all',
			'name' => __( 'Show all languages', 'polylang' ),
			'flag' => '<span class="ab-icon"></span>',
		);

		$selected = empty( $this->filter_lang ) ? $all_item : $this->filter_lang;

		$title = sprintf(
			'<span class="ab-label"%1$s><span class="screen-reader-text">%2$s</span>%3$s</span>',
			$selected instanceof PLL_Language ? sprintf( ' lang="%s"', esc_attr( $selected->get_locale( 'display' ) ) ) : '',
			__( 'Filters content by language', 'polylang' ),
			esc_html( $selected->name )
		);

		$all_items = array_merge( array( $all_item ), $this->model->get_languages_list() );
		$items     = $all_items;

		if ( $this->should_hide_admin_bar_menu() ) {
			$items = array();
		}

		/**
		 * Filters the admin bar language filter submenu items.
		 *
		 * @since 2.6
		 * @since 3.8 Added `$all_items` parameter.
		 *
		 * @param array $items     The items of the admin languages filter to display (may be empty if menu hidden).
		 * @param array $all_items Complete unfiltered list of all available language items.
		 */
		$items = apply_filters( 'pll_admin_languages_filter', $items, $all_items );

		if ( empty( $items ) ) {
			return;
		}

		$wp_admin_bar->add_menu(
			array(
				'id'    => 'languages',
				'title' => $selected->flag . $title,
				'href'  => esc_url( add_query_arg( 'lang', $selected->slug, remove_query_arg( 'paged' ) ) ),
				'meta'  => array(
					'title' => __( 'Filters content by language', 'polylang' ),
					'class' => 'all' === $selected->slug ? '' : 'pll-filtered-languages',
				),
			)
		);

		foreach ( $items as $lang ) {
			if ( $selected->slug === $lang->slug ) {
				continue;
			}

			$wp_admin_bar->add_menu(
				array(
					'parent' => 'languages',
					'id'     => $lang->slug,
					'title'  => $lang->flag . esc_html( $lang->name ),
					'href'   => esc_url( add_query_arg( 'lang', $lang->slug, remove_query_arg( 'paged' ) ) ),
					'meta'   => 'all' === $lang->slug ? array() : array( 'lang' => esc_attr( $lang->get_locale( 'display' ) ) ),
				)
			);
		}
	}

	/**
	 * Remove the customize submenu when using a block theme.
	 *
	 * WordPress removes the Customizer menu if a block theme is activated and no other plugins interact with it.
	 * As Polylang interacts with the Customizer, we have to delete this menu ourselves in the case of a block theme,
	 * unless another plugin than Polylang interacts with the Customizer.
	 *
	 * @since 3.2
	 *
	 * @return void
	 */
	public function remove_customize_submenu() {
		if ( ! $this->should_customize_menu_be_removed() ) {
			return;
		}

		global $submenu;

		if ( ! empty( $submenu['themes.php'] ) ) {
			foreach ( $submenu['themes.php'] as $submenu_item ) {
				if ( 'customize' === $submenu_item[1] ) {
					remove_submenu_page( 'themes.php', $submenu_item[2] );
				}
			}
		}
	}

	/**
	 * Tells if the Polylang's admin bar menu should be hidden for the current page.
	 * Conventionally, it should be hidden on edition pages.
	 *
	 * @since 3.8
	 *
	 * @return bool
	 */
	public function should_hide_admin_bar_menu(): bool {
		global $pagenow, $typenow, $taxnow;

		if ( in_array( $pagenow, array( 'post.php', 'post-new.php' ), true ) ) {
			return ! empty( $typenow );
		}

		if ( 'term.php' === $pagenow ) {
			return ! empty( $taxnow );
		}

		return false;
	}

	/**
	 * Returns the ID of a Polylang's settings screen.
	 *
	 * @since 3.8
	 *
	 * @param string $tab The name of the screen (`lang`, `strings`, `settings`).
	 * @return string
	 *
	 * @phpstan-return non-empty-string
	 */
	public static function get_screen_id( string $tab ): string {
		return sprintf( '%s_page_%s', self::SCREEN_PREFIX, self::get_screen_slug( $tab ) );
	}

	/**
	 * Returns the slug of a Polylang's settings screen, as seen in the URL.
	 *
	 * @since 3.8
	 *
	 * @param string $tab The name of the screen (`lang`, `strings`, `settings`).
	 * @return string
	 *
	 * @phpstan-return non-empty-string
	 */
	public static function get_screen_slug( string $tab ): string {
		return 'lang' === $tab ? 'mlang' : "mlang_$tab";
	}

	/**
	 * Returns the list of sub-menu items.
	 *
	 * @since 3.8
	 *
	 * @return string[] List of sub-menu items with page slugs as array keys, and sub-menu titles as array values.
	 *
	 * @phpstan-return array<non-empty-string, string>
	 */
	protected function get_menu_items(): array {
		$tabs = array(
			'lang' => __( 'Languages', 'polylang' ),
		);

		// Only if at least one language has been created.
		if ( ! empty( $this->model->languages->filter( 'translator' )->get_list() ) ) {
			$tabs['strings'] = __( 'Translations', 'polylang' );
		}

		$tabs['settings'] = __( 'Settings', 'polylang' );

		/**
		 * Filter the list of sub-menu items in Polylang settings.
		 *
		 * @since 1.5.1
		 *
		 * @param string[] $tabs List of sub-menu items with page slugs as array keys and titles as array values.
		 */
		return (array) apply_filters( 'pll_settings_tabs', $tabs );
	}

	/**
	 * Returns the user capability required to access the given menu page.
	 *
	 * @since 3.8
	 *
	 * @param string $menu Menu slug.
	 * @return string
	 */
	protected function get_menu_capability( string $menu ): string {
		switch ( $menu ) {
			case 'lang':
				return Capabilities::LANGUAGES;

			case 'strings':
				return Capabilities::TRANSLATIONS;
		}

		return 'manage_options';
	}
}