<?php
declare(strict_types=1);
final class Kernel
{
    private string $bootId;
    private int $handled = 0;
    private ?string $currentUser = null;
    private array $requestCache = [];
    private PDO $database;
    public function __construct()
    {
        $this->bootId = bin2hex(random_bytes(6));
        $this->database = new PDO('sqlite::memory:', null, null, [PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION]);
        $this->database->exec('CREATE TABLE products (id INTEGER PRIMARY KEY, name TEXT, price INTEGER)');
        $this->database->exec("INSERT INTO products VALUES (1, 'Аудит', 5000), (2, 'Настройка', 12000), (3, 'Сопровождение', 25000)");
    }
    public function handle(): void
    {
        ++$this->handled;
        $userBefore = $this->currentUser;
        $cacheBefore = count($this->requestCache);
        $requestId = bin2hex(random_bytes(6));
        $base = ['mode'=>getenv('FP_MODE') ?: 'classic','bootId'=>$this->bootId,'handled'=>$this->handled,'requestId'=>$requestId,'userBefore'=>$userBefore,'cacheBefore'=>$cacheBefore,'php'=>PHP_VERSION];
        try {
            $path = parse_url($_SERVER['REQUEST_URI'] ?? '/', PHP_URL_PATH);
            $method = $_SERVER['REQUEST_METHOD'] ?? 'GET';
            if ($path === '/fail') throw new RuntimeException('Intentional training failure');
            if ($path === '/health') { $this->json(200, $base + ['ok'=>true]); return; }
            if ($path === '/customer') {
                $user = $_GET['user'] ?? 'guest';
                if (!is_string($user) || !in_array($user, ['anna','ivan','guest'], true)) { $this->json(422, $base + ['error'=>'INVALID_DEMO_USER']); return; }
                $this->currentUser = $user;
                $this->requestCache['greeting'] = 'Здравствуйте, '.$user;
                $this->json(200, $base + ['user'=>$this->currentUser,'greeting'=>$this->requestCache['greeting']]); return;
            }
            if ($path === '/orders') {
                if ($method !== 'POST') { header('Allow: POST'); $this->json(405, $base + ['error'=>'METHOD_NOT_ALLOWED']); return; }
                if (!preg_match('~^application/json(?:;|$)~i', $_SERVER['CONTENT_TYPE'] ?? '')) { $this->json(415, $base + ['error'=>'JSON_REQUIRED']); return; }
                $raw = file_get_contents('php://input', false, null, 0, 16385);
                if ($raw === false || strlen($raw) > 16384) { $this->json(413, $base + ['error'=>'BODY_TOO_LARGE']); return; }
                try { $body = json_decode($raw, false, 16, JSON_THROW_ON_ERROR); } catch (JsonException) { $this->json(400, $base + ['error'=>'INVALID_JSON']); return; }
                if (!$body instanceof stdClass || !isset($body->title) || !is_string($body->title) || trim($body->title) === '' || strlen($body->title) > 120) { $this->json(422, $base + ['error'=>'INVALID_TITLE']); return; }
                $this->json(201, $base + ['accepted'=>true,'title'=>$body->title,'persisted'=>false]); return;
            }
            if ($path === '/products') {
                $min = filter_var($_GET['min'] ?? '0', FILTER_VALIDATE_INT, ['options'=>['min_range'=>0,'max_range'=>1000000]]);
                if ($min === false) { $this->json(422, $base + ['error'=>'INVALID_MIN']); return; }
                $query = $this->database->prepare('SELECT id, name, price FROM products WHERE price >= :min ORDER BY price');
                $query->bindValue(':min', $min, PDO::PARAM_INT); $query->execute();
                $this->json(200, $base + ['storage'=>'sqlite-memory-demo','items'=>$query->fetchAll(PDO::FETCH_ASSOC)]); return;
            }
            $this->json(404, $base + ['error'=>'NOT_FOUND']);
        } catch (Throwable $error) {
            error_log(json_encode(['event'=>'request_failed','requestId'=>$requestId,'exception'=>$error::class], JSON_THROW_ON_ERROR));
            $this->json(500, $base + ['error'=>'INTERNAL_ERROR']);
        } finally {
            if ($this->database->inTransaction()) $this->database->rollBack();
            $this->currentUser = null;
            $this->requestCache = [];
        }
    }
    private function json(int $status, array $data): void
    {
        http_response_code($status);
        header('Content-Type: application/json; charset=utf-8');
        header('Cache-Control: no-store');
        echo json_encode($data, JSON_UNESCAPED_UNICODE | JSON_THROW_ON_ERROR);
    }
}