<?php
namespace Digiter\BuilderStudio;
defined('ABSPATH') || exit;

/** Local interface catalogues. Never translates authored documents or field values. */
final class Language {
    private const OPTION = 'digibl_interface_language';
    private static array $catalogs = [];

    public static function boot(): void {
        add_action('rest_api_init', [self::class, 'routes']);
        add_action('admin_menu', [self::class, 'menu'], 30);
        add_action('admin_post_digibl_interface_language', [self::class, 'save_form']);
        add_filter('gettext_digiter-builder-lite', [self::class, 'gettext'], 10, 3);
        add_filter('rest_post_dispatch', [self::class, 'translate_error'], 10, 3);
    }

    public static function policy(): array {
        static $policy;
        return $policy ??= json_decode(file_get_contents(DIGIBL_PATH . 'data/languages.json'), true);
    }

    public static function resolve(string $locale): string {
        $value = strtolower(str_replace(['-', '@'], '_', trim($locale)));
        $policy = self::policy();
        $value = $policy['aliases'][$value] ?? $value;
        $base = explode('_', $value)[0];
        $base = $policy['aliases'][$base] ?? $base;
        if (in_array($base, $policy['excluded'], true)) { return 'en'; }
        if ($base === 'sr' && preg_match('/(?:^|_)(?:latn|latin)(?:_|$)/', $value)) { return 'sr_latn'; }
        if (isset($policy['languages'][$value])) { return $value; }
        return isset($policy['languages'][$base]) ? $base : 'en';
    }

    public static function valid_mode($mode): bool {
        return is_string($mode) && ($mode === 'auto' || $mode === 'site' || isset(self::policy()['languages'][$mode]));
    }

    public static function mode(): string {
        $mode = get_current_user_id() ? get_user_option(self::OPTION) : false;
        return self::valid_mode($mode) ? $mode : 'auto';
    }

    public static function site_locale(): string {
        $locale = get_option('WPLANG', null);
        if ($locale === null && is_multisite()) { $locale = get_site_option('WPLANG', null); }
        if ($locale === null && defined('WPLANG')) { $locale = WPLANG; }
        return is_string($locale) && $locale !== '' ? $locale : 'en_US';
    }

    public static function current(): string {
        $mode = self::mode();
        return self::resolve($mode === 'auto' ? get_user_locale() : ($mode === 'site' ? self::site_locale() : $mode));
    }

    public static function state(): array {
        $stored = get_current_user_id() ? get_user_option(self::OPTION) : false;
        return [
            'mode' => self::mode(), 'language' => self::current(),
            'automatic' => self::resolve(get_user_locale()), 'siteLanguage' => self::resolve(self::site_locale()),
            'hasPreference' => self::valid_mode($stored),
        ];
    }

    /** Per user and per site; no change to WordPress, another user, or page content. */
    public static function save($mode, bool $migrate = false) {
        if (!get_current_user_id() || !PostTypes::can_edit()) {
            return new \WP_Error('digibl_language_forbidden', self::text('Access denied.'), ['status' => 403]);
        }
        if (!self::valid_mode($mode)) {
            return new \WP_Error('digibl_language_invalid', self::text('Choose a supported interface language.'), ['status' => 400]);
        }
        $lockKey = 'digibl_language_lock_' . get_current_user_id();
        $lock = \Digiter\Diagnostics\ProtocolV1::lock($lockKey, 30);
        if (!$lock) {
            return new \WP_Error('digibl_language_busy', self::text('A language change is already being saved.'), ['status' => 409]);
        }
        try {
            // Refresh after taking the lock: another browser may have saved a choice.
            wp_cache_delete(get_current_user_id(), 'user_meta');
            if ($migrate && self::state()['hasPreference']) { return self::state(); }
            if (!update_user_option(get_current_user_id(), self::OPTION, $mode, false)
                && get_user_option(self::OPTION) !== $mode) {
                return new \WP_Error('digibl_language_storage', self::text('Language could not be saved. Please try again.'), ['status' => 500]);
            }
            return self::state();
        } finally {
            \Digiter\Diagnostics\ProtocolV1::unlock($lockKey, $lock);
        }
    }

    public static function routes(): void {
        register_rest_route('digiter-builder/v1', '/interface-language', [
            'methods' => 'POST',
            'permission_callback' => static fn() => get_current_user_id() && PostTypes::can_edit(),
            'callback' => static function ($request) {
                $result = self::save($request->get_param('mode'), $request->get_param('migrate') === true);
                if (is_wp_error($result)) { return $result; }
                $response = new \WP_REST_Response($result);
                $response->header('Cache-Control', 'no-store, private');
                return $response;
            },
        ]);
    }

    public static function menu(): void {
        add_submenu_page('digiter-builder', self::text('Interface language'), self::text('Interface language'),
            PostTypes::menu_capability(), 'digibl-interface-language', [self::class, 'screen']);
    }

    public static function screen(): void {
        if (!PostTypes::can_edit()) { wp_die(esc_html(self::text('Access denied.'))); }
        echo '<div class="wrap" id="dbs-language-settings" lang="' . esc_attr(str_replace('_', '-', self::current())) . '"><h1>' . esc_html(self::text('Interface language')) . '</h1>';
        if (isset($_GET['language_saved'])) { echo '<div class="notice notice-success"><p>' . esc_html(self::text('Interface language saved.')) . '</p></div>'; }
        echo '<p>' . esc_html(self::text('This choice is saved to your account on this site and applies on every device.')) . '</p>';
        echo '<form method="post" action="' . esc_url(admin_url('admin-post.php')) . '"><input type="hidden" name="action" value="digibl_interface_language">';
        wp_nonce_field('digibl_interface_language');
        echo '<label for="dbs-language-mode"><strong>' . esc_html(self::text('Interface language')) . '</strong></label><p><select id="dbs-language-mode" name="mode">';
        $options = ['auto' => self::text('Automatic — WordPress'), 'site' => self::text('Follow site language')] + self::policy()['languages'];
        foreach ($options as $value => $label) {
            echo '<option value="' . esc_attr($value) . '" ' . selected(self::mode(), $value, false) . '>' . esc_html($label) . '</option>';
        }
        echo '</select></p><p>' . esc_html(self::text('Automatic follows your WordPress profile language, or the site language when your profile uses the site default.')) . '</p>';
        echo '<p>' . esc_html(self::text('Follow site language uses the site setting regardless of your profile language.')) . '</p>';
        echo '<p>' . esc_html(self::text('Page content and field values are not translated.')) . '</p>';
        submit_button(self::text('Save language'));
        echo '</form></div>';
    }

    public static function save_form(): void {
        if (!PostTypes::can_edit()) { wp_die(esc_html(self::text('Access denied.')), '', ['response' => 403]); }
        check_admin_referer('digibl_interface_language');
        $result = self::save(isset($_POST['mode']) && is_string($_POST['mode']) ? wp_unslash($_POST['mode']) : null);
        if (is_wp_error($result)) { wp_die(esc_html($result->get_error_message()), '', ['response' => (int) $result->get_error_data()['status']]); }
        wp_safe_redirect(add_query_arg('language_saved', '1', admin_url('admin.php?page=digibl-interface-language')));
        exit;
    }

    public static function catalog(string $language): array {
        $language = self::resolve($language);
        if (!isset(self::$catalogs[$language])) {
            $path = DIGIBL_PATH . 'languages/' . $language . '.json';
            $value = is_readable($path) ? json_decode(file_get_contents($path), true) : [];
            self::$catalogs[$language] = is_array($value) ? $value : [];
        }
        return self::$catalogs[$language];
    }

    public static function text(string $message): string {
        $language = self::current();
        $own = self::catalog($language);
        if (isset($own[$message]) && is_string($own[$message]) && $own[$message] !== '') { return $own[$message]; }
        return self::catalog('en')[$message] ?? $message;
    }

    public static function gettext(string $translation, string $message, string $domain): string {
        return self::text($message);
    }

    /** Only Builder error messages, never successful data or authored documents. */
    public static function translate_error($response, $server, $request) {
        if (!str_starts_with($request->get_route(), '/digiter-builder/v1/') || $response->get_status() < 400) { return $response; }
        $data = $response->get_data();
        if (is_array($data) && isset($data['message']) && is_string($data['message'])) {
            $data['message'] = self::text($data['message']);
            $response->set_data($data);
        }
        return $response;
    }

    public static function wordpress_locale(): string {
        $language = self::current();
        if ($language === 'en') { return 'en_US'; }
        foreach (array_unique(array_merge([get_user_locale(), self::site_locale()], get_available_languages())) as $locale) {
            if (self::resolve($locale) === $language) { return $locale; }
        }
        return 'en_US';
    }

    public static function enqueue(): void {
        wp_enqueue_script('digibl-i18n', DIGIBL_URL . 'assets/i18n.js', [], DIGIBL_VERSION, true);
        wp_enqueue_script('digibl-language', DIGIBL_URL . 'assets/language.js', ['digibl-i18n'], DIGIBL_VERSION, true);
        $state = self::state();
        wp_add_inline_script('digibl-language', 'window.DIGIBL_LANGUAGE_CONFIG=' . wp_json_encode($state + [
            'policy' => self::policy(), 'catalog' => self::catalog($state['language']),
            'baseUrl' => DIGIBL_URL . 'languages/', 'version' => DIGIBL_VERSION,
            'endpoint' => rest_url('digiter-builder/v1/interface-language'), 'nonce' => wp_create_nonce('wp_rest'),
            'storageKey' => 'dbs-language-v2-' . get_current_blog_id() . '-' . get_current_user_id(),
        ], JSON_HEX_TAG | JSON_HEX_AMP | JSON_HEX_APOS | JSON_HEX_QUOT) . ';', 'before');
    }
}