<?php
namespace Mince;

use stdClass;
use RuntimeException;
use Socket;
use Index\AString;
use Index\Net\EndPoint;
use Index\Net\IPAddress;
use Index\Net\IPEndPoint;
use Index\Net\DnsEndPoint;

class ServerQuery { // rewrite this to use https://wiki.vg/Server_List_Ping query is kinda useless
    public const PORT = 25565;

    private string $addr;
    private int $port;
    private Socket $socket;
    private int $sessionId;
    private int $challengeToken = 0;

    public function __construct(IPAddress $addr, int $port) {
        $this->addr = (string)$addr;
        $this->port = $port;
        $this->sessionId = random_int(0, 0x7FFFFFFF) & 0x0F0F0F0F;
        $this->socket = socket_create($addr->isV6() ? AF_INET6 : AF_INET, SOCK_DGRAM, SOL_UDP);
        $this->handshake();
    }

    public function __destruct() {
        socket_close($this->socket);
    }

    public function handshake(): void {
        $response = $this->send(9);
        $length = strlen($response);
        $token = '';

        for($i = 0; $i < $length; ++$i) {
            $char = $response[$i];
            if($char === "\0")
                break;
            $token .= $char;
        }

        $this->challengeToken = intval($token);
    }

    public function stats(): object {
        $response = $this->send(0, pack('N', $this->challengeToken));

        $offset = 0;
        $data = new stdClass;

        $data->motd = self::readString($response, $offset);
        $data->gametype = self::readString($response, $offset);
        $data->map = self::readString($response, $offset);
        $data->numplayers = self::readString($response, $offset);
        $data->maxplayers = self::readString($response, $offset);
        $data->hostport = unpack('v', substr($response, $offset, 2))[1];
        $offset += 2;
        $data->hostip = self::readString($response, $offset);

        return $data;
    }

    private static function readString(string $source, int &$offset): string {
        $length = strlen($source);
        $string = '';

        for(; $offset < $length; ++$offset) {
            $char = $source[$offset];
            if($char === "\0")
                break;
            $string .= $char;
        }

        ++$offset;

        return $string;
    }

    private function send(int $type, string $payload = ''): string {
        $payload = "\xFE\xFD" . pack('CN', $type, $this->sessionId) . $payload;
        socket_sendto($this->socket, $payload, strlen($payload), 0, $this->addr, $this->port);
        socket_recv($this->socket, $response, 1024, MSG_WAITALL);

        $data = unpack('Ctype/Nsession', $response);
        
        if($data['type'] !== $type)
            throw new RuntimeException('Type does not match.');
        if($data['session'] !== $this->sessionId)
            throw new RuntimeException('Session id does not match.');

        return substr($response, 5);
    }

    public static function create(AString|string $endPoint): ServerQuery {
        $endPoint = AString::cast($endPoint);
        $firstChar = $endPoint[0];

        if($firstChar === '[') { // IPv6
            if($endPoint->contains(']:'))
                $endPoint = IPEndPoint::parse($endPoint);
            else
                $endPoint = new IPEndPoint(IPAddress::parse($endPoint->trim('[]')), self::PORT);

            return new ServerQuery($endPoint->getAddress(), $endPoint->getPort());
        } elseif(is_numeric($firstChar)) { // IPv4
            if($endPoint->contains(':'))
                $endPoint = IPEndPoint::parse($endPoint);
            else
                $endPoint = new IPEndPoint(IPAddress::parse($endPoint), self::PORT);

            return new ServerQuery($endPoint->getAddress(), $endPoint->getPort());
        } else { // DNS
            if($endPoint->contains(':'))
                $endPoint = DnsEndPoint::parse($endPoint);
            else {
                $endPoint = new DnsEndPoint($endPoint, self::PORT);

                $records = dns_get_record('_minecraft._tcp.' . (string)$endPoint->getHost(), DNS_SRV);

                if(!empty($records)) {
                    usort($records, function($a, $b) {
                        $priority = $a['pri'] <=> $b['pri'];
                        if($priority !== 0)
                            return $priority;
                        $weight = $a['weight'] <=> $b['weight'];
                        if($weight !== 0)
                            return $priority;
                        return 0;
                    });

                    foreach($records as $record) {
                        try {
                            return ServerQuery::create($record['target'] . ':' . $record['port']);
                        } catch(Exception $ex) {}
                    }
                }
            }

            $records = dns_get_record((string)$endPoint->getHost(), DNS_A);

            if(!empty($records)) {
                foreach($records as $record) {
                    try {
                        return new ServerQuery(IPAddress::parse($record['ip']), $endPoint->getPort());
                    } catch(Exception $ex) {}
                }
            }

            $records = dns_get_record((string)$endPoint->getHost(), DNS_AAAA);

            if(!empty($records)) {
                foreach($records as $record) {
                    try {
                        return new ServerQuery(IPAddress::parse($record['ipv6']), $endPoint->getPort());
                    } catch(Exception $ex) {}
                }
            }
        }

        throw new RuntimeException('Failed to connect.');
    }
}