<?php

declare(strict_types=1);

namespace LIT\MCP\Integrations\Divi\Release;

use Closure;
use LIT\MCP\Admin\SettingsPage;
use LIT\MCP\Integrations\Divi\Admin\DiviTab;
use LIT\MCP\Log;
use Throwable;
use WP_REST_Response;

defined('ABSPATH') || exit;

/**
 * "Prüfung starten" of the Divi tab (spec §6.1): POST /wp-json/lit-mcp/v1/divi-check. A REST request on purpose –
 * not admin-post – so the check runs in the same context as MCP calls (Divi renders its blocks in REST requests,
 * lit-page-render-summary). The form sends the wp_rest nonce as _wpnonce (cookie authentication); only manage_options.
 * One check at a time: an atomic "INSERT IGNORE" on the options table (self::LOCK) is the lock – add_option() reads
 * then writes (wp-includes/option.php) and is not atomic, so two simultaneous requests could both "acquire" it. A
 * lock older than LOCK_TTL is a dead check's, taken over with a conditional UPDATE (compare-and-swap on the value
 * just read) so only one of several concurrent takers wins. A check that throws still releases the lock (finally)
 * and redirects with divi_check_failed (logged, never shown to the browser as an unhandled 500). Answers 303 back
 * to the tab.
 */
final class DiviCheckRoute
{
    public const NAMESPACE = 'lit-mcp/v1';
    public const ROUTE = '/divi-check';
    public const LOCK = 'lit_mcp_divi_check_lock';

    private const LOCK_TTL = 600;

    /** @param Closure(): CompatibilityCheck $check */
    public function __construct(private Closure $check, private ?CheckReportStore $reports = null)
    {
    }

    public function register(): void
    {
        add_action('rest_api_init', [$this, 'registerRoute']);
    }

    public function registerRoute(): void
    {
        register_rest_route(self::NAMESPACE, self::ROUTE, [
            'methods' => 'POST',
            'callback' => [$this, 'handle'],
            'permission_callback' => static fn (): bool => current_user_can('manage_options'),
        ]);
    }

    public static function url(): string
    {
        return rest_url(self::NAMESPACE . self::ROUTE);
    }

    public function handle(): WP_REST_Response
    {
        $notice = 'divi_check_running';
        if (self::lock()) {
            try {
                $report = ($this->check)()->run(get_current_user_id());
                ($this->reports ?? new CheckReportStore())->save($report);
                ReleaseGate::invalidate();
                $notice = 'divi_checked';
            } catch (Throwable $e) {
                Log::failure('divi check', $e);
                $notice = 'divi_check_failed';
            } finally {
                delete_option(self::LOCK);
            }
        }

        return new WP_REST_Response(
            null,
            303,
            ['Location' => SettingsPage::url(DiviTab::SLUG, ['lit_mcp_notice' => $notice])]
        );
    }

    private static function lock(): bool
    {
        global $wpdb;

        if (self::insertLock($wpdb, time())) {
            return true;
        }

        // get_var(), not get_option(): the row was written with raw SQL, bypassing the options cache.
        $since = $wpdb->get_var($wpdb->prepare(
            "SELECT option_value FROM {$wpdb->options} WHERE option_name = %s",
            self::LOCK
        ));
        if ($since === null) {
            // The lock was released between our failed insert and this read; try once more.
            return self::insertLock($wpdb, time());
        }
        if (time() - (int) $since < self::LOCK_TTL) {
            return false;
        }

        $taken = $wpdb->query($wpdb->prepare(
            "UPDATE {$wpdb->options} SET option_value = %s WHERE option_name = %s AND option_value = %s",
            (string) time(),
            self::LOCK,
            $since
        ));

        return (int) $taken === 1;
    }

    /** INSERT IGNORE: 1 row affected = the lock did not exist and is now ours; 0 = someone else holds it. */
    private static function insertLock(\wpdb $wpdb, int $now): bool
    {
        $inserted = $wpdb->query($wpdb->prepare(
            "INSERT IGNORE INTO {$wpdb->options} (option_name, option_value, autoload) VALUES (%s, %s, 'no')",
            self::LOCK,
            (string) $now
        ));

        return (int) $inserted === 1;
    }
}