<?php

declare(strict_types=1);

namespace Evomedien\Vitec\Middleware;

use Psr\Http\Message\ResponseInterface;
use Psr\Http\Message\ServerRequestInterface;
use Psr\Http\Server\MiddlewareInterface;
use Psr\Http\Server\RequestHandlerInterface;
use TYPO3\CMS\Core\Database\ConnectionPool;
use TYPO3\CMS\Core\Http\NormalizedParams;
use TYPO3\CMS\Core\Http\Response;
use TYPO3\CMS\Core\RateLimiter\RateLimiterFactory;

/**
 * Client error endpoint: POST /api/vitec/client-error
 *
 * The React frontend reports browser-side failures here (window.onerror,
 * unhandledrejection, chunk reloads after a deploy, element error
 * boundaries) - contract 0072-FE section 4, accepted in 0077-BE:
 *
 *   {url, message, stack, release, userAgent}  ->  204 No Content
 *
 * Guards, all answered with a 4xx and no body:
 *   405  method other than POST
 *   413  body larger than 8 KB (Content-Length or actual bytes)
 *   400  not a JSON object, or "message" missing/empty
 *   429  more than 30 reports per minute from one IP (sliding window
 *        via TYPO3's rate limiter, cache "ratelimiter")
 *
 * Entries land in tx_vitec_clienterrorlog with the IP anonymized (IPv4
 * last octet zeroed, IPv6 cut to /48); the full IP is only the key of
 * the rate limiter and is never stored. No session, no cookies - a
 * navigator.sendBeacon() call must get through unchanged. Rows older
 * than 30 days are removed by vitec:client-error-cleanup.
 */
final class ClientErrorMiddleware implements MiddlewareInterface
{
    private const PATH = '/api/vitec/client-error';
    private const MAX_BODY_BYTES = 8192;
    private const LIMIT_PER_MINUTE = 30;
    private const TABLE = 'tx_vitec_clienterrorlog';

    public function __construct(
        private readonly ConnectionPool $connectionPool,
        private readonly RateLimiterFactory $rateLimiterFactory,
    ) {}

    public function process(ServerRequestInterface $request, RequestHandlerInterface $handler): ResponseInterface
    {
        $path = rtrim($request->getUri()->getPath(), '/');
        if ($path !== self::PATH) {
            return $handler->handle($request);
        }

        $method = strtoupper($request->getMethod());
        if ($method === 'OPTIONS') {
            return $this->empty(204)->withHeader('Allow', 'POST, OPTIONS');
        }
        if ($method !== 'POST') {
            return $this->empty(405)->withHeader('Allow', 'POST, OPTIONS');
        }

        $declared = (int)$request->getHeaderLine('Content-Length');
        if ($declared > self::MAX_BODY_BYTES) {
            return $this->empty(413);
        }

        // Rate limit first, so a flood of oversized or broken bodies is
        // cheap to refuse as well.
        $ip = '';
        try {
            $normalized = $request->getAttribute('normalizedParams') ?? NormalizedParams::createFromRequest($request);
            $ip = (string)$normalized->getRemoteAddress();
            $limiter = $this->rateLimiterFactory->createLimiter([
                'id' => 'vitec-client-error',
                'policy' => 'sliding_window',
                'limit' => self::LIMIT_PER_MINUTE,
                'interval' => '1 minute',
            ], $ip);
            $limit = $limiter->consume(1);
            if (!$limit->isAccepted()) {
                $retry = max(1, $limit->getRetryAfter()->getTimestamp() - time());
                return $this->empty(429)->withHeader('Retry-After', (string)$retry);
            }
        } catch (\Throwable) {
            // A broken limiter must not take the endpoint down; the
            // body limit and the 30-day cleanup still bound the damage.
        }

        $body = $request->getBody();
        if ($body->isSeekable()) {
            $body->rewind();
        }
        $raw = $body->read(self::MAX_BODY_BYTES + 1);
        if (strlen($raw) > self::MAX_BODY_BYTES) {
            return $this->empty(413);
        }

        try {
            $data = json_decode($raw, true, 32, JSON_THROW_ON_ERROR);
        } catch (\JsonException) {
            return $this->empty(400);
        }
        if (!\is_array($data) || array_is_list($data)) {
            return $this->empty(400);
        }
        $message = trim($this->str($data['message'] ?? ''));
        if ($message === '') {
            return $this->empty(400);
        }

        $row = [
            'pid' => 0,
            'crdate' => time(),
            'url' => $this->cut($this->str($data['url'] ?? ''), 1024),
            'message' => $this->cut($message, 2000),
            'stack' => $this->cut($this->str($data['stack'] ?? ''), 6000),
            'release' => $this->cut($this->str($data['release'] ?? ''), 100),
            'user_agent' => $this->cut($this->str($data['userAgent'] ?? $request->getHeaderLine('User-Agent')), 500),
            'ip' => self::anonymizeIp($ip),
        ];
        try {
            $this->connectionPool->getConnectionForTable(self::TABLE)->insert(self::TABLE, $row);
        } catch (\Throwable) {
            // Table missing (extension:setup not run yet) or DB hiccup:
            // the client gets its 204 anyway - a reporting endpoint must
            // never turn into a second error in the browser console.
        }

        return $this->empty(204);
    }

    /**
     * IPv4: last octet zeroed (192.0.2.0). IPv6: first three groups
     * kept (2001:db8:1::). Anything else: empty.
     */
    public static function anonymizeIp(string $ip): string
    {
        if (filter_var($ip, FILTER_VALIDATE_IP, FILTER_FLAG_IPV4) !== false) {
            $parts = explode('.', $ip);
            $parts[3] = '0';
            return implode('.', $parts);
        }
        if (filter_var($ip, FILTER_VALIDATE_IP, FILTER_FLAG_IPV6) !== false) {
            $packed = inet_pton($ip);
            if ($packed === false) {
                return '';
            }
            $hex = bin2hex($packed);
            $groups = [];
            for ($i = 0; $i < 3; $i++) {
                $groups[] = ltrim(substr($hex, $i * 4, 4), '0') ?: '0';
            }
            return implode(':', $groups) . '::';
        }
        return '';
    }

    private function str(mixed $value): string
    {
        if (\is_string($value)) {
            return $value;
        }
        if (\is_int($value) || \is_float($value) || \is_bool($value)) {
            return (string)$value;
        }
        return '';
    }

    private function cut(string $value, int $max): string
    {
        $value = str_replace("\0", '', $value);
        return mb_strlen($value) > $max ? mb_substr($value, 0, $max) : $value;
    }

    private function empty(int $status): ResponseInterface
    {
        return (new Response())
            ->withStatus($status)
            ->withHeader('Cache-Control', 'no-store');
    }
}