<?php
if ( ! defined( 'ABSPATH' ) ) exit;

/**
 * Class Translangated_Abilities
 *
 * Registers Translangated abilities with the WordPress Abilities API.
 * Only registers if the Abilities API is present (WordPress 6.9+ or the
 * Abilities API feature plugin). Reuses existing settings
 * code paths instead of duplicating logic.
 *
 * Registered abilities (all require `manage_options`):
 *   translangated/add-language                    POST   add a translation language
 *   translangated/remove-language                 POST   remove a translation language
 *   translangated/update-language                 POST   change a language's slug / publish flag
 *   translangated/set-default-language            POST   promote a configured language to default
 *   translangated/list-languages                  GET    list configured languages
 *   translangated/list-available-languages        GET    list the full locale catalog
 *   translangated/enable-automatic-translation    POST   turn on Automatic Translation (Google Translate or DeepL)
 *
 * Calling them from PHP:
 *
 *   $ability = wp_get_ability( 'translangated/add-language' );
 *   $result  = $ability->execute( array( 'language_code' => 'fr_FR' ) );
 *   if ( is_wp_error( $result ) ) { ... }
 *
 * Calling them over REST (requires authentication):
 *
 *   POST /wp-json/wp-abilities/v1/abilities/translangated/add-language/run
 *   Content-Type: application/json
 *   { "input": { "language_code": "fr_FR" } }
 *
 * See the Abilities API docs for schemas, annotations, and execution details:
 *
 * @see https://developer.wordpress.org/apis/abilities-api/
 */
class Translangated_Abilities {

    const CATEGORY = 'translangated';

    public function __construct() {
        if ( ! $this->is_abilities_api_available() ) {
            return;
        }

        add_action( 'wp_abilities_api_categories_init', array( $this, 'register_category' ) );
        add_action( 'wp_abilities_api_init', array( $this, 'register_abilities' ) );
    }

    private function is_abilities_api_available(): bool {
        return class_exists( 'WP_Ability' ) && function_exists( 'wp_register_ability' );
    }

    public function register_category(): void {
        wp_register_ability_category(
            self::CATEGORY,
            array(
                'label'       => __( 'Translangated', 'translangated' ),
                'description' => __( 'Abilities for managing Translangated configuration.', 'translangated' ),
            )
        );
    }

    public function register_abilities(): void {
        wp_register_ability( 'translangated/add-language', array(
            'label'               => __( 'Add a translation language', 'translangated' ),
            'description'         => __( 'Adds a translation language to Translangated. Enforces the same language limit as the settings UI.', 'translangated' ),
            'category'            => self::CATEGORY,
            'input_schema'        => array(
                'type'                 => 'object',
                'properties'           => array(
                    'language_code' => array(
                        'type'        => 'string',
                        'description' => __( 'WordPress locale code (e.g. fr_FR, de_DE).', 'translangated' ),
                        'minLength'   => 1,
                    ),
                    'slug'          => array(
                        'type'        => 'string',
                        'description' => __( 'Optional URL slug. Defaults to the ISO language code if omitted.', 'translangated' ),
                    ),
                ),
                'required'             => array( 'language_code' ),
                'additionalProperties' => false,
            ),
            'output_schema'       => array(
                'type'       => 'object',
                'properties' => array(
                    'added'                 => array( 'type' => 'string' ),
                    'translation_languages' => array(
                        'type'  => 'array',
                        'items' => array( 'type' => 'string' ),
                    ),
                ),
            ),
            'execute_callback'    => array( $this, 'execute_add_language' ),
            'permission_callback' => array( $this, 'permission_manage_options' ),
            'meta'                => array( 'show_in_rest' => true ),
        ) );

        wp_register_ability( 'translangated/enable-automatic-translation', array(
            'label'               => __( 'Enable Automatic Translation', 'translangated' ),
            'description'         => __( 'Turns on Automatic Translation using Google Translate or DeepL (configure the engine API key in the settings). If no engine is passed and none is configured, defaults to google_translate_v2.', 'translangated' ),
            'category'            => self::CATEGORY,
            'input_schema'        => array(
                'type'                 => 'object',
                'properties'           => array(
                    'engine' => array(
                        'type'        => 'string',
                        'description' => __( 'Optional translation-engine slug to select ("google_translate_v2" or "deepl"). When omitted, keeps the already-configured engine, or defaults to "google_translate_v2" if none is configured.', 'translangated' ),
                        'minLength'   => 1,
                    ),
                ),
                'additionalProperties' => false,
                // Empty-object input; the same `default: stdClass` trick used by the
                // GET abilities lets this be called with no `input` payload at all.
                'default'              => new stdClass(),
            ),
            'output_schema'       => array(
                'type'       => 'object',
                'properties' => array(
                    'machine_translation' => array( 'type' => 'string' ),
                    'translation_engine'  => array( 'type' => 'string' ),
                ),
            ),
            'execute_callback'    => array( $this, 'execute_enable_automatic_translation' ),
            'permission_callback' => array( $this, 'permission_manage_options' ),
            'meta'                => array( 'show_in_rest' => true ),
        ) );

        wp_register_ability( 'translangated/list-languages', array(
            'label'               => __( 'List configured languages', 'translangated' ),
            'description'         => __( 'Returns the languages currently configured in Translangated, including the default language and per-language slug/publish state.', 'translangated' ),
            'category'            => self::CATEGORY,
            'input_schema'        => array(
                'type'                 => 'object',
                'properties'           => array(),
                'additionalProperties' => false,
                // GET requests cannot deliver an object via query string (the Abilities
                // API does not JSON-decode `?input=...`). Providing a default lets callers
                // omit the parameter entirely and have normalize_input() fill it in.
                'default'              => new stdClass(),
            ),
            'output_schema'       => array(
                'type'       => 'object',
                'properties' => array(
                    'default_language'      => array( 'type' => 'string' ),
                    'translation_languages' => array(
                        'type'  => 'array',
                        'items' => array(
                            'type'       => 'object',
                            'properties' => array(
                                'code'      => array( 'type' => 'string' ),
                                'name'      => array( 'type' => 'string' ),
                                'slug'      => array( 'type' => 'string' ),
                                'published' => array( 'type' => 'boolean' ),
                                'is_default'=> array( 'type' => 'boolean' ),
                            ),
                        ),
                    ),
                ),
            ),
            'execute_callback'    => array( $this, 'execute_list_languages' ),
            'permission_callback' => array( $this, 'permission_manage_options' ),
            'meta'                => array(
                'show_in_rest' => true,
                'annotations'  => array( 'readonly' => true ),
            ),
        ) );

        wp_register_ability( 'translangated/list-available-languages', array(
            'label'               => __( 'List available language codes', 'translangated' ),
            'description'         => __( 'Returns the full catalog of language codes Translangated recognizes, with their English names.', 'translangated' ),
            'category'            => self::CATEGORY,
            'input_schema'        => array(
                'type'                 => 'object',
                'properties'           => array(),
                'additionalProperties' => false,
                'default'              => new stdClass(),
            ),
            'output_schema'       => array(
                'type'       => 'object',
                'properties' => array(
                    'languages' => array(
                        'type'  => 'array',
                        'items' => array(
                            'type'       => 'object',
                            'properties' => array(
                                'code' => array( 'type' => 'string' ),
                                'name' => array( 'type' => 'string' ),
                            ),
                        ),
                    ),
                ),
            ),
            'execute_callback'    => array( $this, 'execute_list_available_languages' ),
            'permission_callback' => array( $this, 'permission_manage_options' ),
            'meta'                => array(
                'show_in_rest' => true,
                'annotations'  => array( 'readonly' => true ),
            ),
        ) );

        wp_register_ability( 'translangated/remove-language', array(
            'label'               => __( 'Remove a translation language', 'translangated' ),
            'description'         => __( 'Removes a configured translation language. The default language cannot be removed without first reassigning the default.', 'translangated' ),
            'category'            => self::CATEGORY,
            'input_schema'        => array(
                'type'                 => 'object',
                'properties'           => array(
                    'language_code' => array(
                        'type'        => 'string',
                        'description' => __( 'Locale code of the language to remove.', 'translangated' ),
                        'minLength'   => 1,
                    ),
                ),
                'required'             => array( 'language_code' ),
                'additionalProperties' => false,
            ),
            'output_schema'       => array(
                'type'       => 'object',
                'properties' => array(
                    'removed'               => array( 'type' => 'string' ),
                    'translation_languages' => array(
                        'type'  => 'array',
                        'items' => array( 'type' => 'string' ),
                    ),
                ),
            ),
            'execute_callback'    => array( $this, 'execute_remove_language' ),
            'permission_callback' => array( $this, 'permission_manage_options' ),
            'meta'                => array(
                'show_in_rest' => true,
                // Marked destructive for semantic clarity. We deliberately omit
                // 'idempotent' because the Abilities API routes destructive+idempotent
                // to DELETE, whose query-string `input` is not JSON-decoded — so
                // object-shaped input would fail schema validation over the wire.
                'annotations'  => array( 'destructive' => true ),
            ),
        ) );

        wp_register_ability( 'translangated/update-language', array(
            'label'               => __( 'Update a translation language', 'translangated' ),
            'description'         => __( 'Replaces the slug and publish status of an already-configured translation language.', 'translangated' ),
            'category'            => self::CATEGORY,
            'input_schema'        => array(
                'type'                 => 'object',
                'properties'           => array(
                    'language_code' => array(
                        'type'        => 'string',
                        'description' => __( 'Locale code of the language to update.', 'translangated' ),
                        'minLength'   => 1,
                    ),
                    'slug'          => array(
                        'type'        => 'string',
                        'description' => __( 'URL slug for this language.', 'translangated' ),
                        'minLength'   => 1,
                    ),
                    'published'     => array(
                        'type'        => 'boolean',
                        'description' => __( 'Whether this language is published on the front end.', 'translangated' ),
                    ),
                ),
                'required'             => array( 'language_code', 'slug', 'published' ),
                'additionalProperties' => false,
            ),
            'output_schema'       => array(
                'type'       => 'object',
                'properties' => array(
                    'updated'   => array( 'type' => 'string' ),
                    'slug'      => array( 'type' => 'string' ),
                    'published' => array( 'type' => 'boolean' ),
                ),
            ),
            'execute_callback'    => array( $this, 'execute_update_language' ),
            'permission_callback' => array( $this, 'permission_manage_options' ),
            'meta'                => array( 'show_in_rest' => true ),
        ) );

        wp_register_ability( 'translangated/set-default-language', array(
            'label'               => __( 'Set the default language', 'translangated' ),
            'description'         => __( 'Promotes an already-configured language to be the site default. The previous default remains in the translation languages list.', 'translangated' ),
            'category'            => self::CATEGORY,
            'input_schema'        => array(
                'type'                 => 'object',
                'properties'           => array(
                    'language_code' => array(
                        'type'        => 'string',
                        'description' => __( 'Locale code to promote to default. Must already be a configured translation language.', 'translangated' ),
                        'minLength'   => 1,
                    ),
                ),
                'required'             => array( 'language_code' ),
                'additionalProperties' => false,
            ),
            'output_schema'       => array(
                'type'       => 'object',
                'properties' => array(
                    'default_language'         => array( 'type' => 'string' ),
                    'previous_default_language'=> array( 'type' => 'string' ),
                ),
            ),
            'execute_callback'    => array( $this, 'execute_set_default_language' ),
            'permission_callback' => array( $this, 'permission_manage_options' ),
            'meta'                => array( 'show_in_rest' => true ),
        ) );
    }

    public function permission_manage_options() {
        if ( ! current_user_can( 'manage_options' ) ) {
            return new WP_Error(
                'translangated_abilities_forbidden',
                __( 'You do not have permission to manage Translangated settings.', 'translangated' ),
                array( 'status' => 403 )
            );
        }
        return true;
    }

    /**
     * Adds a single translation language by reusing Translangated_Settings::sanitize_settings().
     *
     * Mirrors Translangated_Step_Languages::save_languages() — same option key, same
     * sanitization path — so register_setting() hooks, table creation, etc.
     * all fire identically to a UI save.
     */
    public function execute_add_language( $input ) {
        $language_code = isset( $input['language_code'] ) ? sanitize_text_field( $input['language_code'] ) : '';

        if ( ! translangated_is_valid_language_code( $language_code ) ) {
            return new WP_Error(
                'translangated_invalid_language_code',
                __( 'Invalid language code. Allowed characters: A-Z, a-z, 0-9, hyphen, underscore.', 'translangated' )
            );
        }

        $trp        = Translangated_Plugin::get_translangated_instance();
        $languages  = $trp->get_component( 'languages' )->get_languages();
        $settings_c = $trp->get_component( 'settings' );

        if ( ! array_key_exists( $language_code, $languages ) ) {
            return new WP_Error(
                'translangated_unknown_language',
                sprintf(
                    /* translators: %s: language code */
                    __( 'Language code "%s" is not recognized by Translangated.', 'translangated' ),
                    $language_code
                )
            );
        }

        $translangated_settings          = get_option( 'translangated_settings', array() );
        $default_language      = isset( $translangated_settings['default-language'] ) ? $translangated_settings['default-language'] : 'en_US';
        $translation_languages = isset( $translangated_settings['translation-languages'] ) ? (array) $translangated_settings['translation-languages'] : array();
        $publish_languages     = isset( $translangated_settings['publish-languages'] ) ? (array) $translangated_settings['publish-languages'] : array();
        $url_slugs             = isset( $translangated_settings['url-slugs'] ) ? (array) $translangated_settings['url-slugs'] : array();

        if ( $language_code === $default_language || in_array( $language_code, $translation_languages, true ) ) {
            return new WP_Error(
                'translangated_language_already_added',
                sprintf(
                    /* translators: %s: language code */
                    __( 'Language "%s" is already configured.', 'translangated' ),
                    $language_code
                )
            );
        }

        // Same limit gate the UI uses — the bundled extra-languages add-on raises it via the filter.
        $max_secondary = (int) apply_filters( 'translangated_secondary_languages', 1 );
        $secondary_count = count( array_diff( $translation_languages, array( $default_language ) ) );
        if ( $secondary_count >= $max_secondary ) {
            return new WP_Error(
                'translangated_language_limit_reached',
                sprintf(
                    /* translators: %d: maximum number of secondary languages */
                    __( 'Translangated allows up to %d additional language(s).', 'translangated' ),
                    $max_secondary
                ),
                array( 'max_secondary_languages' => $max_secondary )
            );
        }

        $translation_languages[] = $language_code;
        $publish_languages[]     = $language_code;

        $slug = isset( $input['slug'] ) ? sanitize_title( $input['slug'] ) : '';
        if ( '' === $slug ) {
            $slug = sanitize_title( strtok( $language_code, '_' ) );
        }
        $url_slugs[ $language_code ] = $slug;

        $translangated_settings['default-language']      = $default_language;
        $translangated_settings['translation-languages'] = array_values( array_unique( $translation_languages ) );
        $translangated_settings['publish-languages']     = array_values( array_unique( $publish_languages ) );
        $translangated_settings['url-slugs']             = $url_slugs;

        $sanitized = $settings_c->sanitize_settings( $translangated_settings );

        // sanitize_settings() can short-circuit with a get_option fallback when invalid codes slip through.
        if ( ! is_array( $sanitized ) || ! in_array( $language_code, (array) $sanitized['translation-languages'], true ) ) {
            return new WP_Error(
                'translangated_settings_rejected',
                __( 'Translangated rejected the new language during settings sanitization.', 'translangated' )
            );
        }

        update_option( 'translangated_settings', $sanitized );

        return array(
            'added'                 => $language_code,
            'translation_languages' => array_values( (array) $sanitized['translation-languages'] ),
        );
    }

    /**
     * Turns on Automatic Translation.
     *
     * Engine resolution, in order:
     *   1. `$input['engine']` when provided, wins.
     *   2. Existing `translangated_machine_translation_settings['translation-engine']`, if it is still an available engine.
     *   3. Falls back to 'google_translate_v2'.
     */
    public function execute_enable_automatic_translation( $input = array() ) {
        // Normalize: REST delivers an assoc array; direct PHP callers may pass
        // an stdClass (that's what the `default: new stdClass()` schema produces
        // when no `input` payload is supplied).
        $input = is_array( $input ) ? $input : (array) $input;

        $settings = get_option( 'translangated_machine_translation_settings', array() );
        if ( ! is_array( $settings ) ) {
            $settings = array();
        }

        $requested_engine = isset( $input['engine'] ) ? sanitize_text_field( (string) $input['engine'] ) : '';
        $existing_engine  = isset( $settings['translation-engine'] ) ? (string) $settings['translation-engine'] : '';

        $available_engines = wp_list_pluck( apply_filters( 'translangated_machine_translation_engines', array() ), 'value' );

        if ( '' !== $requested_engine ) {
            if ( ! in_array( $requested_engine, $available_engines, true ) ) {
                return new WP_Error(
                    'translangated_invalid_engine',
                    /* translators: %s: comma-separated list of engine slugs */
                    sprintf( __( 'Unknown translation engine. Available engines: %s.', 'translangated' ), implode( ', ', $available_engines ) )
                );
            }
            $engine = $requested_engine;
        } elseif ( in_array( $existing_engine, $available_engines, true ) ) {
            $engine = $existing_engine;
        } else {
            $engine = 'google_translate_v2';
        }

        $settings['machine-translation'] = 'yes';
        $settings['translation-engine']  = $engine;

        update_option( 'translangated_machine_translation_settings', $settings );

        return array(
            'machine_translation' => 'yes',
            'translation_engine'  => $engine,
        );
    }

    public function execute_list_languages() {
        $translangated_settings = get_option( 'translangated_settings', array() );
        $trp          = Translangated_Plugin::get_translangated_instance();
        $names        = $trp->get_component( 'languages' )->get_languages();

        $default     = isset( $translangated_settings['default-language'] ) ? $translangated_settings['default-language'] : '';
        $translation = isset( $translangated_settings['translation-languages'] ) ? (array) $translangated_settings['translation-languages'] : array();
        $publish     = isset( $translangated_settings['publish-languages'] ) ? (array) $translangated_settings['publish-languages'] : array();
        $url_slugs   = isset( $translangated_settings['url-slugs'] ) ? (array) $translangated_settings['url-slugs'] : array();

        $items = array();
        foreach ( $translation as $code ) {
            $items[] = array(
                'code'       => $code,
                'name'       => isset( $names[ $code ] ) ? $names[ $code ] : $code,
                'slug'       => isset( $url_slugs[ $code ] ) ? $url_slugs[ $code ] : '',
                'published'  => in_array( $code, $publish, true ),
                'is_default' => ( $code === $default ),
            );
        }

        return array(
            'default_language'      => $default,
            'translation_languages' => $items,
        );
    }

    public function execute_list_available_languages() {
        $trp   = Translangated_Plugin::get_translangated_instance();
        $names = $trp->get_component( 'languages' )->get_languages();

        $items = array();
        foreach ( $names as $code => $name ) {
            $items[] = array( 'code' => $code, 'name' => $name );
        }
        return array( 'languages' => $items );
    }

    public function execute_remove_language( $input ) {
        $code = sanitize_text_field( $input['language_code'] );

        if ( ! translangated_is_valid_language_code( $code ) ) {
            return new WP_Error(
                'translangated_invalid_language_code',
                __( 'Invalid language code. Allowed characters: A-Z, a-z, 0-9, hyphen, underscore.', 'translangated' )
            );
        }

        $translangated_settings          = get_option( 'translangated_settings', array() );
        $default_language      = isset( $translangated_settings['default-language'] ) ? $translangated_settings['default-language'] : 'en_US';
        $translation_languages = isset( $translangated_settings['translation-languages'] ) ? (array) $translangated_settings['translation-languages'] : array();
        $publish_languages     = isset( $translangated_settings['publish-languages'] ) ? (array) $translangated_settings['publish-languages'] : array();
        $url_slugs             = isset( $translangated_settings['url-slugs'] ) ? (array) $translangated_settings['url-slugs'] : array();

        if ( ! in_array( $code, $translation_languages, true ) ) {
            return new WP_Error(
                'translangated_language_not_configured',
                sprintf(
                    /* translators: %s: language code */
                    __( 'Language "%s" is not currently configured.', 'translangated' ),
                    $code
                )
            );
        }

        if ( $code === $default_language ) {
            return new WP_Error(
                'translangated_cannot_remove_default',
                __( 'The default language cannot be removed. Set another language as default first.', 'translangated' )
            );
        }

        $translangated_settings['translation-languages'] = array_values( array_diff( $translation_languages, array( $code ) ) );
        $translangated_settings['publish-languages']     = array_values( array_diff( $publish_languages, array( $code ) ) );
        unset( $url_slugs[ $code ] );
        $translangated_settings['url-slugs']             = $url_slugs;

        $sanitized = $this->save_translangated_settings( $translangated_settings );
        if ( is_wp_error( $sanitized ) ) {
            return $sanitized;
        }

        return array(
            'removed'               => $code,
            'translation_languages' => array_values( (array) $sanitized['translation-languages'] ),
        );
    }

    public function execute_update_language( $input ) {
        $code      = sanitize_text_field( $input['language_code'] );
        $slug      = sanitize_title( $input['slug'] );
        $published = (bool) $input['published'];

        if ( ! translangated_is_valid_language_code( $code ) ) {
            return new WP_Error(
                'translangated_invalid_language_code',
                __( 'Invalid language code. Allowed characters: A-Z, a-z, 0-9, hyphen, underscore.', 'translangated' )
            );
        }

        if ( '' === $slug ) {
            return new WP_Error(
                'translangated_invalid_slug',
                __( 'Slug is empty after sanitization. Use only URL-safe characters.', 'translangated' )
            );
        }

        $translangated_settings          = get_option( 'translangated_settings', array() );
        $default_language      = isset( $translangated_settings['default-language'] ) ? $translangated_settings['default-language'] : 'en_US';
        $translation_languages = isset( $translangated_settings['translation-languages'] ) ? (array) $translangated_settings['translation-languages'] : array();
        $publish_languages     = isset( $translangated_settings['publish-languages'] ) ? (array) $translangated_settings['publish-languages'] : array();
        $url_slugs             = isset( $translangated_settings['url-slugs'] ) ? (array) $translangated_settings['url-slugs'] : array();

        if ( ! in_array( $code, $translation_languages, true ) ) {
            return new WP_Error(
                'translangated_language_not_configured',
                sprintf(
                    /* translators: %s: language code */
                    __( 'Language "%s" is not currently configured. Add it first with translangated/add-language.', 'translangated' ),
                    $code
                )
            );
        }

        // The default language is always published; refuse to unpublish it.
        if ( $code === $default_language && ! $published ) {
            return new WP_Error(
                'translangated_cannot_unpublish_default',
                __( 'The default language is always published and cannot be unpublished.', 'translangated' )
            );
        }

        // Reject slug collision with another configured language.
        foreach ( $url_slugs as $other_code => $other_slug ) {
            if ( $other_code !== $code && $other_slug === $slug ) {
                return new WP_Error(
                    'translangated_duplicate_slug',
                    sprintf(
                        /* translators: 1: slug, 2: language code */
                        __( 'Slug "%1$s" is already in use by language "%2$s".', 'translangated' ),
                        $slug,
                        $other_code
                    )
                );
            }
        }

        $url_slugs[ $code ] = $slug;
        $translangated_settings['url-slugs'] = $url_slugs;

        $publish_set = array_flip( $publish_languages );
        if ( $published ) {
            $publish_set[ $code ] = true;
        } else {
            unset( $publish_set[ $code ] );
        }
        $translangated_settings['publish-languages'] = array_keys( $publish_set );

        $sanitized = $this->save_translangated_settings( $translangated_settings );
        if ( is_wp_error( $sanitized ) ) {
            return $sanitized;
        }

        return array(
            'updated'   => $code,
            'slug'      => isset( $sanitized['url-slugs'][ $code ] ) ? $sanitized['url-slugs'][ $code ] : $slug,
            'published' => in_array( $code, (array) $sanitized['publish-languages'], true ),
        );
    }

    public function execute_set_default_language( $input ) {
        $code = sanitize_text_field( $input['language_code'] );

        if ( ! translangated_is_valid_language_code( $code ) ) {
            return new WP_Error(
                'translangated_invalid_language_code',
                __( 'Invalid language code. Allowed characters: A-Z, a-z, 0-9, hyphen, underscore.', 'translangated' )
            );
        }

        $translangated_settings          = get_option( 'translangated_settings', array() );
        $previous_default      = isset( $translangated_settings['default-language'] ) ? $translangated_settings['default-language'] : 'en_US';
        $translation_languages = isset( $translangated_settings['translation-languages'] ) ? (array) $translangated_settings['translation-languages'] : array();

        if ( $code === $previous_default ) {
            return array(
                'default_language'          => $code,
                'previous_default_language' => $previous_default,
            );
        }

        if ( ! in_array( $code, $translation_languages, true ) ) {
            return new WP_Error(
                'translangated_language_not_configured',
                sprintf(
                    /* translators: %s: language code */
                    __( 'Language "%s" is not currently configured. Add it first with translangated/add-language.', 'translangated' ),
                    $code
                )
            );
        }

        $translangated_settings['default-language'] = $code;
        // sanitize_settings() will reinsert the new default at the head and keep the old default in the list.

        $sanitized = $this->save_translangated_settings( $translangated_settings );
        if ( is_wp_error( $sanitized ) ) {
            return $sanitized;
        }

        return array(
            'default_language'          => (string) $sanitized['default-language'],
            'previous_default_language' => $previous_default,
        );
    }

    /**
     * Runs translangated_settings through Translangated_Settings::sanitize_settings() and persists it.
     * Returns the sanitized array on success or WP_Error if sanitization rejected the payload.
     */
    private function save_translangated_settings( array $translangated_settings ) {
        $settings_c = Translangated_Plugin::get_translangated_instance()->get_component( 'settings' );
        $sanitized  = $settings_c->sanitize_settings( $translangated_settings );

        if ( ! is_array( $sanitized ) || ! isset( $sanitized['translation-languages'] ) ) {
            return new WP_Error(
                'translangated_settings_rejected',
                __( 'Translangated rejected the new settings during sanitization.', 'translangated' )
            );
        }

        update_option( 'translangated_settings', $sanitized );
        return $sanitized;
    }
}