<?php

declare(strict_types=1);

namespace LIT\MCP\Integrations\WordPress\Settings;

use WP_Post;

/**
 * The WordPress options LIT MCP may read and write (spec §6.5), with validation.
 *
 * validate() arms are delegated to one-purpose helper methods rather than inline
 * ternaries: PHPCompatibility's RemovedTernaryAssociativity sniff misreads a `match`
 * whose arms are themselves ternaries as chained ternaries and rejects them, even
 * though PHP itself parses them fine (controller ruling P3).
 */
final class SettingsWhitelist
{
    /** key => [group, type, description] */
    public const SETTINGS = [
        'blogname' => ['general', 'string', 'Titel der Website'],
        'blogdescription' => ['general', 'string', 'Untertitel der Website'],
        'WPLANG' => ['general', 'string', 'Sprache (Locale, z. B. de_DE; en_US = Englisch); nur installierte Sprachen'],
        'timezone_string' => ['general', 'string', 'Zeitzone, z. B. Europe/Berlin'],
        'date_format' => ['general', 'string', 'Datumsformat (PHP), z. B. j. F Y'],
        'time_format' => ['general', 'string', 'Zeitformat (PHP), z. B. H:i'],
        'show_on_front' => ['reading', 'string', 'Startseite: posts (neueste Beiträge) oder page (statische Seite)'],
        'page_on_front' => ['reading', 'integer', 'ID der statischen Startseite (0 = keine)'],
        'page_for_posts' => ['reading', 'integer', 'ID der Beitragsseite (0 = keine)'],
        'posts_per_page' => ['reading', 'integer', 'Beiträge pro Seite (1–100)'],
        'default_comment_status' => ['discussion', 'string', 'Kommentare für neue Beiträge: open oder closed'],
        'default_ping_status' => ['discussion', 'string', 'Pingbacks für neue Beiträge: open oder closed'],
        'permalink_structure' => ['permalinks', 'string', 'Permalink-Struktur, z. B. /%postname%/ (leer = einfach)'],
        'site_icon' => ['site_icon', 'integer', 'Anhang-ID des Website-Icons (Bild, empfohlen 512×512; 0 = keins)'],
    ];

    public const BLOCKED = ['admin_email', 'users_can_register', 'default_role', 'siteurl', 'home'];
    public const GROUPS = ['general', 'reading', 'discussion', 'permalinks', 'site_icon'];

    private const INTEGER_KEYS = ['page_on_front', 'page_for_posts', 'posts_per_page', 'site_icon'];

    public function current(string $key): mixed
    {
        $value = get_option($key);
        if ($key === 'WPLANG') {
            return $value === '' || $value === false ? 'en_US' : (string) $value;
        }

        if (in_array($key, self::INTEGER_KEYS, true)) {
            return (int) $value;
        }

        return (string) $value;
    }

    /**
     * @param array<string, mixed> $pending All values of the current call.
     * @return string|null Error message, null when valid.
     */
    public function validate(string $key, mixed $value, array $pending): ?string
    {
        if (in_array($key, self::BLOCKED, true)) {
            return 'Gesperrt: aus Sicherheitsgründen nicht über LIT MCP änderbar.';
        }

        if (! isset(self::SETTINGS[$key])) {
            return 'Nicht freigegeben; erlaubt: ' . implode(', ', array_keys(self::SETTINGS)) . '.';
        }

        return match ($key) {
            'blogname', 'blogdescription' => $this->checkText($value),
            'WPLANG' => $this->checkLanguage($value),
            'timezone_string' => $this->checkTimezone($value),
            'date_format', 'time_format' => $this->checkFormat($value),
            'show_on_front' => $this->checkShowOnFront($value, $pending),
            'page_on_front', 'page_for_posts' => $this->checkPage($key, $value, $pending),
            'posts_per_page' => $this->checkPostsPerPage($value),
            'default_comment_status', 'default_ping_status' => $this->checkOpenClosed($value),
            'permalink_structure' => $this->checkPermalink($value),
            'site_icon' => $this->checkSiteIcon($value),
        };
    }

    public function normalize(string $key, mixed $value): mixed
    {
        if ($key === 'WPLANG' && $value === 'en_US') {
            return '';
        }

        return $value;
    }

    private function checkText(mixed $value): ?string
    {
        if (is_string($value) && mb_strlen($value) <= 200) {
            return null;
        }

        return 'Text bis 200 Zeichen erwartet.';
    }

    private function checkLanguage(mixed $value): ?string
    {
        // Clients say en_US for English; '' is WordPress' internal storage form for it
        // (see normalize()) and is not accepted as input.
        if ($value === 'en_US') {
            return null;
        }

        $installed = get_available_languages();
        if (is_string($value) && in_array($value, $installed, true)) {
            return null;
        }

        return sprintf('Sprache nicht installiert; verfügbar: en_US, %s.', implode(', ', $installed));
    }

    private function checkTimezone(mixed $value): ?string
    {
        if (is_string($value) && in_array($value, timezone_identifiers_list(), true)) {
            return null;
        }

        return 'Zeitzonen-Kennung wie Europe/Berlin erwartet.';
    }

    private function checkFormat(mixed $value): ?string
    {
        if (is_string($value) && trim($value) !== '' && mb_strlen($value) <= 50) {
            return null;
        }

        return 'Nicht leeres Format bis 50 Zeichen erwartet.';
    }

    /** @param array<string, mixed> $pending */
    private function checkShowOnFront(mixed $value, array $pending): ?string
    {
        if ($value === 'posts') {
            return null;
        }

        if ($value !== 'page') {
            return 'posts oder page erwartet.';
        }

        $front = (int) ($pending['page_on_front'] ?? get_option('page_on_front'));
        if ($front > 0) {
            return null;
        }

        return 'Für page zuerst page_on_front setzen (im selben Aufruf möglich).';
    }

    /** @param array<string, mixed> $pending */
    private function checkPage(string $key, mixed $value, array $pending): ?string
    {
        if (! is_int($value) || $value < 0) {
            return 'Seiten-ID (0 = keine) erwartet.';
        }

        if ($value === 0) {
            return null;
        }

        $page = get_post($value);
        if (! $page instanceof WP_Post || $page->post_type !== 'page' || $page->post_status !== 'publish') {
            return sprintf('%d ist keine veröffentlichte Seite.', $value);
        }

        $other = $key === 'page_on_front' ? 'page_for_posts' : 'page_on_front';
        $otherValue = (int) ($pending[$other] ?? get_option($other));
        if ($otherValue === $value) {
            return 'Startseite und Beitragsseite müssen verschiedene Seiten sein.';
        }

        return null;
    }

    private function checkPostsPerPage(mixed $value): ?string
    {
        if (is_int($value) && $value >= 1 && $value <= 100) {
            return null;
        }

        return 'Ganzzahl von 1 bis 100 erwartet.';
    }

    private function checkOpenClosed(mixed $value): ?string
    {
        if (in_array($value, ['open', 'closed'], true)) {
            return null;
        }

        return 'open oder closed erwartet.';
    }

    private function checkPermalink(mixed $value): ?string
    {
        if ($value === '') {
            return null;
        }

        if (
            is_string($value)
            && str_starts_with($value, '/')
            && str_contains($value, '%')
            && mb_strlen($value) <= 200
            && preg_match('/\s/', $value) !== 1
        ) {
            return null;
        }

        return 'Leer oder eine Struktur wie /%postname%/ erwartet.';
    }

    private function checkSiteIcon(mixed $value): ?string
    {
        if (! is_int($value) || $value < 0) {
            return 'Anhang-ID (0 = keins) erwartet.';
        }

        if ($value === 0 || wp_attachment_is_image($value)) {
            return null;
        }

        return sprintf('%d ist kein Bild der Mediathek.', $value);
    }
}