<?php

/**
 * webtrees: online genealogy
 * Copyright (C) 2023 webtrees development team
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 * You should have received a copy of the GNU General Public License
 * along with this program. If not, see <https://www.gnu.org/licenses/>.
 */

declare(strict_types=1);

namespace Fisharebest\Webtrees\Http\Middleware;

use Fig\Http\Message\StatusCodeInterface;
use Fisharebest\Webtrees\Registry;
use Fisharebest\Webtrees\Validator;
use GuzzleHttp\Client;
use GuzzleHttp\Exception\GuzzleException;
use Iodev\Whois\Loaders\CurlLoader;
use Iodev\Whois\Modules\Asn\AsnRouteInfo;
use Iodev\Whois\Whois;
use IPLib\Address\AddressInterface;
use IPLib\Factory as IPFactory;
use IPLib\Range\RangeInterface;
use Psr\Http\Message\ResponseInterface;
use Psr\Http\Message\ServerRequestInterface;
use Psr\Http\Server\MiddlewareInterface;
use Psr\Http\Server\RequestHandlerInterface;
use Throwable;

use function array_filter;
use function array_map;
use function assert;
use function gethostbyaddr;
use function gethostbyname;
use function preg_match_all;
use function random_int;
use function response;
use function str_contains;
use function str_ends_with;

/**
 * Middleware to block bad robots before they waste our valuable CPU cycles.
 */
class BadBotBlocker implements MiddlewareInterface
{
    private const REGEX_OCTET = '(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)';
    private const REGEX_IPV4  = '/\\b' . self::REGEX_OCTET . '(?:\\.' . self::REGEX_OCTET . '){3}\\b/';

    // Cache whois requests.  Try to avoid all caches expiring at the same time.
    private const WHOIS_TTL_MIN = 28 * 86400;
    private const WHOIS_TTL_MAX = 35 * 86400;
    private const WHOIS_TIMEOUT = 5;

    // Bad robots - SEO optimisers, advertisers, etc.  This list is shared with robots.txt.
    public const BAD_ROBOTS = [
        'admantx',
        'Adsbot',
        'AhrefsBot',
        'Amazonbot', // Until it understands crawl-delay and noindex / nofollow
        'AspiegelBot',
        'Awario', // Brand management
        'Barkrowler',
        'BLEXBot',
        'Bytespider',
        'DataForSEO',
        'DataForSeoBot', // https://dataforseo.com/dataforseo-bot
        'DotBot',
        'Grapeshot',
        'Honolulu-bot', // Aggressive crawer, no info available
        'ia_archiver',
        'linabot', // Aggressive crawer, no info available
        'Linguee',
        'MegaIndex.ru',
        'MJ12bot',
        'netEstate NE',
        'panscient',
        'PetalBot',
        'proximic',
        'SeekportBot', // Pretends to be a search engine - but isn't
        'SemrushBot',
        'serpstatbot',
        'SEOkicks',
        'SiteKiosk',
        'Turnitin',
        'wp_is_mobile', // Nothing to do with wordpress
        'XoviBot',
        'ZoominfoBot',
    ];

    /**
     * Some search engines use reverse/forward DNS to verify the IP address.
     *
     * @see https://developer.amazon.com/support/amazonbot
     * @see https://support.google.com/webmasters/answer/80553?hl=en
     * @see https://www.bing.com/webmaster/help/which-crawlers-does-bing-use-8c184ec0
     * @see https://www.bing.com/webmaster/help/how-to-verify-bingbot-3905dc26
     * @see https://yandex.com/support/webmaster/robot-workings/check-yandex-robots.html
     * @see https://www.mojeek.com/bot.html
     * @see https://support.apple.com/en-gb/HT204683
     */
    private const ROBOT_REV_FWD_DNS = [
        'Amazonbot'        => ['.crawl.amazon.com'],
        'Applebot'         => ['.applebot.apple.com'],
        'BingPreview'      => ['.search.msn.com'],
        'Google'           => ['.google.com', '.googlebot.com'],
        'Mail.RU_Bot'      => ['.mail.ru'],
        'MicrosoftPreview' => ['.search.msn.com'],
        'MojeekBot'        => ['.mojeek.com'],
        'Qwantify'         => ['.search.qwant.com'],
        'Sogou'            => ['.crawl.sogou.com'],
        'Yahoo'            => ['.crawl.yahoo.net'],
        'Yandex'           => ['.yandex.ru', '.yandex.net', '.yandex.com'],
        'bingbot'          => ['.search.msn.com'],
        'msnbot'           => ['.search.msn.com'],
    ];

    /**
     * Some search engines only use reverse DNS to verify the IP address.
     *
     * @see https://help.baidu.com/question?prod_id=99&class=0&id=3001
     * @see https://napoveda.seznam.cz/en/full-text-search/seznambot-crawler
     * @see https://www.ionos.de/terms-gtc/faq-crawler
     */
    private const ROBOT_REV_ONLY_DNS = [
        'Baiduspider' => ['.baidu.com', '.baidu.jp'],
        'FreshBot'    => ['.seznam.cz'],
        'IonCrawl'    => ['.1und1.org'],
        'Neevabot'    => ['.neeva.com'],
        'SeznamBot'   => ['.seznam.cz'],
    ];

    /**
     * Some search engines operate from designated IP addresses.
     *
     * @see https://www.apple.com/go/applebot
     * @see https://help.duckduckgo.com/duckduckgo-help-pages/results/duckduckbot
     */
    private const ROBOT_IPS = [
        'AppleBot'    => [
            '17.0.0.0/8',
        ],
        'Ask Jeeves'  => [
            '65.214.45.143',
            '65.214.45.148',
            '66.235.124.192',
            '66.235.124.7',
            '66.235.124.101',
            '66.235.124.193',
            '66.235.124.73',
            '66.235.124.196',
            '66.235.124.74',
            '63.123.238.8',
            '202.143.148.61',
        ],
        'DuckDuckBot' => [
            '23.21.227.69',
            '50.16.241.113',
            '50.16.241.114',
            '50.16.241.117',
            '50.16.247.234',
            '52.204.97.54',
            '52.5.190.19',
            '54.197.234.188',
            '54.208.100.253',
            '54.208.102.37',
            '107.21.1.8',
        ],
    ];

    /**
     * Some search engines operate from designated IP addresses.
     *
     * @see https://bot.seekport.com/
     */
    private const ROBOT_IP_FILES = [
        'SeekportBot' => 'https://bot.seekport.com/seekportbot_ips.txt',
    ];

    /**
     * Some search engines operate from within a designated autonomous system.
     *
     * @see https://developers.facebook.com/docs/sharing/webmasters/crawler
     * @see https://www.facebook.com/peering/
     */
    private const ROBOT_ASNS = [
        'facebook' => ['AS32934', 'AS63293'],
        'twitter'  => ['AS13414'],
    ];

    /**
     * @param ServerRequestInterface  $request
     * @param RequestHandlerInterface $handler
     *
     * @return ResponseInterface
     */
    public function process(ServerRequestInterface $request, RequestHandlerInterface $handler): ResponseInterface
    {
        $ua      = Validator::serverParams($request)->string('HTTP_USER_AGENT', '');
        $ip      = Validator::attributes($request)->string('client-ip');
        $address = IPFactory::parseAddressString($ip);
        assert($address instanceof AddressInterface);

        foreach (self::BAD_ROBOTS as $robot) {
            if (str_contains($ua, $robot)) {
                return $this->response();
            }
        }

        foreach (self::ROBOT_REV_FWD_DNS as $robot => $valid_domains) {
            if (str_contains($ua, $robot) && !$this->checkRobotDNS($ip, $valid_domains, false)) {
                return $this->response();
            }
        }

        foreach (self::ROBOT_REV_ONLY_DNS as $robot => $valid_domains) {
            if (str_contains($ua, $robot) && !$this->checkRobotDNS($ip, $valid_domains, true)) {
                return $this->response();
            }
        }

        foreach (self::ROBOT_IPS as $robot => $valid_ip_ranges) {
            if (str_contains($ua, $robot)) {
                foreach ($valid_ip_ranges as $ip_range) {
                    $range = IPFactory::parseRangeString($ip_range);

                    if ($range instanceof RangeInterface && $range->contains($address)) {
                        continue 2;
                    }
                }

                return $this->response();
            }
        }

        foreach (self::ROBOT_IP_FILES as $robot => $url) {
            if (str_contains($ua, $robot)) {
                $valid_ip_ranges = $this->fetchIpRangesForUrl($robot, $url);

                foreach ($valid_ip_ranges as $ip_range) {
                    $range = IPFactory::parseRangeString($ip_range);

                    if ($range instanceof RangeInterface && $range->contains($address)) {
                        continue 2;
                    }
                }

                return $this->response();
            }
        }

        foreach (self::ROBOT_ASNS as $robot => $asns) {
            foreach ($asns as $asn) {
                if (str_contains($ua, $robot)) {
                    foreach ($this->fetchIpRangesForAsn($asn) as $range) {
                        if ($range->contains($address)) {
                            continue 2;
                        }
                    }

                    return $this->response();
                }
            }
        }

        // Allow sites to block access from entire networks.
        $block_asn = Validator::attributes($request)->string('block_asn', '');
        preg_match_all('/(AS\d+)/', $block_asn, $matches);

        foreach ($matches[1] as $asn) {
            foreach ($this->fetchIpRangesForAsn($asn) as $range) {
                if ($range->contains($address)) {
                    return $this->response();
                }
            }
        }

        return $handler->handle($request);
    }

    /**
     * Check that an IP address belongs to a robot operator using a forward/reverse DNS lookup.
     *
     * @param string        $ip
     * @param array<string> $valid_domains
     * @param bool          $reverse_only
     *
     * @return bool
     */
    private function checkRobotDNS(string $ip, array $valid_domains, bool $reverse_only): bool
    {
        $host = gethostbyaddr($ip);

        if ($host === false) {
            return false;
        }

        foreach ($valid_domains as $domain) {
            if (str_ends_with($host, $domain)) {
                return $reverse_only || $ip === gethostbyname($host);
            }
        }

        return false;
    }

    /**
     * Perform a whois search for an ASN.
     *
     * @param string $asn The autonomous system number to query
     *
     * @return array<RangeInterface>
     */
    private function fetchIpRangesForAsn(string $asn): array
    {
        return Registry::cache()->file()->remember('whois-asn-' . $asn, static function () use ($asn): array {
            $mapper = static fn (AsnRouteInfo $route_info): ?RangeInterface => IPFactory::parseRangeString($route_info->route ?: $route_info->route6);

            try {
                $loader = new CurlLoader(self::WHOIS_TIMEOUT);
                $whois  = new Whois($loader);
                $info   = $whois->loadAsnInfo($asn);
                $routes = $info->routes;
                $ranges = array_map($mapper, $routes);

                return array_filter($ranges);
            } catch (Throwable) {
                return [];
            }
        }, random_int(self::WHOIS_TTL_MIN, self::WHOIS_TTL_MAX));
    }

    /**
     * Fetch a list of IP addresses from a remote file.
     *
     * @param string $ua
     * @param string $url
     *
     * @return array<string>
     */
    private function fetchIpRangesForUrl(string $ua, string $url): array
    {
        return Registry::cache()->file()->remember('url-ip-list-' . $ua, static function () use ($url): array {
            try {
                $client   = new Client();
                $response = $client->get($url, ['timeout' => 5]);
                $contents = $response->getBody()->getContents();

                preg_match_all(self::REGEX_IPV4, $contents, $matches);

                return $matches[0];
            } catch (GuzzleException) {
                return [];
            }
        }, random_int(self::WHOIS_TTL_MIN, self::WHOIS_TTL_MAX));
    }

    /**
     * @return ResponseInterface
     */
    private function response(): ResponseInterface
    {
        return response('Not acceptable', StatusCodeInterface::STATUS_NOT_ACCEPTABLE);
    }
}