class IpUtils

class IpUtils {
    public const PRIVATE_SUBNETS = [
        '127.0.0.0/8',
        // RFC1700 (Loopback)
'10.0.0.0/8',
        // RFC1918
'192.168.0.0/16',
        // RFC1918
'172.16.0.0/12',
        // RFC1918
'169.254.0.0/16',
        // RFC3927
'0.0.0.0/8',
        // RFC5735
'240.0.0.0/4',
        // RFC1112
'::1/128',
        // Loopback
'fc00::/7',
        // Unique Local Address
'fe80::/10',
        // Link Local Address
'::ffff:0:0/96',
        // IPv4 translations
'::/128',
    ];
    private static array $checkedIps = [];
    
    /**
     * This class should not be instantiated.
     */
    private function __construct() {
    }
    
    /**
     * Checks if an IPv4 or IPv6 address is contained in the list of given IPs or subnets.
     *
     * @param string|array $ips List of IPs or subnets (can be a string if only a single one)
     */
    public static function checkIp(string $requestIp, string|array $ips) : bool {
        if (!\is_array($ips)) {
            $ips = [
                $ips,
            ];
        }
        $method = substr_count($requestIp, ':') > 1 ? 'checkIp6' : 'checkIp4';
        foreach ($ips as $ip) {
            if (self::$method($requestIp, $ip)) {
                return true;
            }
        }
        return false;
    }
    
    /**
     * Compares two IPv4 addresses.
     * In case a subnet is given, it checks if it contains the request IP.
     *
     * @param string $ip IPv4 address or subnet in CIDR notation
     *
     * @return bool Whether the request IP matches the IP, or whether the request IP is within the CIDR subnet
     */
    public static function checkIp4(string $requestIp, string $ip) : bool {
        $cacheKey = $requestIp . '-' . $ip . '-v4';
        if (null !== ($cacheValue = self::getCacheResult($cacheKey))) {
            return $cacheValue;
        }
        if (!filter_var($requestIp, \FILTER_VALIDATE_IP, \FILTER_FLAG_IPV4)) {
            return self::setCacheResult($cacheKey, false);
        }
        if (str_contains($ip, '/')) {
            [
                $address,
                $netmask,
            ] = explode('/', $ip, 2);
            if ('0' === $netmask) {
                return self::setCacheResult($cacheKey, false !== filter_var($address, \FILTER_VALIDATE_IP, \FILTER_FLAG_IPV4));
            }
            if ($netmask < 0 || $netmask > 32) {
                return self::setCacheResult($cacheKey, false);
            }
        }
        else {
            $address = $ip;
            $netmask = 32;
        }
        if (false === ip2long($address)) {
            return self::setCacheResult($cacheKey, false);
        }
        return self::setCacheResult($cacheKey, 0 === substr_compare(\sprintf('%032b', ip2long($requestIp)), \sprintf('%032b', ip2long($address)), 0, $netmask));
    }
    
    /**
     * Compares two IPv6 addresses.
     * In case a subnet is given, it checks if it contains the request IP.
     *
     * @author David Soria Parra <dsp at php dot net>
     *
     * @see https://github.com/dsp/v6tools
     *
     * @param string $ip IPv6 address or subnet in CIDR notation
     *
     * @throws \RuntimeException When IPV6 support is not enabled
     */
    public static function checkIp6(string $requestIp, string $ip) : bool {
        $cacheKey = $requestIp . '-' . $ip . '-v6';
        if (null !== ($cacheValue = self::getCacheResult($cacheKey))) {
            return $cacheValue;
        }
        if (!(\extension_loaded('sockets') && \defined('AF_INET6') || @inet_pton('::1'))) {
            throw new \RuntimeException('Unable to check Ipv6. Check that PHP was not compiled with option "disable-ipv6".');
        }
        // Check to see if we were given a IP4 $requestIp or $ip by mistake
        if (!filter_var($requestIp, \FILTER_VALIDATE_IP, \FILTER_FLAG_IPV6)) {
            return self::setCacheResult($cacheKey, false);
        }
        if (str_contains($ip, '/')) {
            [
                $address,
                $netmask,
            ] = explode('/', $ip, 2);
            if (!filter_var($address, \FILTER_VALIDATE_IP, \FILTER_FLAG_IPV6)) {
                return self::setCacheResult($cacheKey, false);
            }
            if ('0' === $netmask) {
                return (bool) unpack('n*', @inet_pton($address));
            }
            if ($netmask < 1 || $netmask > 128) {
                return self::setCacheResult($cacheKey, false);
            }
        }
        else {
            if (!filter_var($ip, \FILTER_VALIDATE_IP, \FILTER_FLAG_IPV6)) {
                return self::setCacheResult($cacheKey, false);
            }
            $address = $ip;
            $netmask = 128;
        }
        $bytesAddr = unpack('n*', @inet_pton($address));
        $bytesTest = unpack('n*', @inet_pton($requestIp));
        if (!$bytesAddr || !$bytesTest) {
            return self::setCacheResult($cacheKey, false);
        }
        for ($i = 1, $ceil = ceil($netmask / 16); $i <= $ceil; ++$i) {
            $left = $netmask - 16 * ($i - 1);
            $left = $left <= 16 ? $left : 16;
            $mask = ~(0xffff >> $left) & 0xffff;
            if (($bytesAddr[$i] & $mask) != ($bytesTest[$i] & $mask)) {
                return self::setCacheResult($cacheKey, false);
            }
        }
        return self::setCacheResult($cacheKey, true);
    }
    
    /**
     * Anonymizes an IP/IPv6.
     *
     * Removes the last bytes of IPv4 and IPv6 addresses (1 byte for IPv4 and 8 bytes for IPv6 by default).
     *
     * @param int<0, 4>  $v4Bytes
     * @param int<0, 16> $v6Bytes
     */
    public static function anonymize(string $ip) : string {
        $v4Bytes = 1 < \func_num_args() ? func_get_arg(1) : 1;
        $v6Bytes = 2 < \func_num_args() ? func_get_arg(2) : 8;
        if ($v4Bytes < 0 || $v6Bytes < 0) {
            throw new \InvalidArgumentException('Cannot anonymize less than 0 bytes.');
        }
        if ($v4Bytes > 4 || $v6Bytes > 16) {
            throw new \InvalidArgumentException('Cannot anonymize more than 4 bytes for IPv4 and 16 bytes for IPv6.');
        }
        $wrappedIPv6 = false;
        if (str_starts_with($ip, '[') && str_ends_with($ip, ']')) {
            $wrappedIPv6 = true;
            $ip = substr($ip, 1, -1);
        }
        $mappedIpV4MaskGenerator = function (string $mask, int $bytesToAnonymize) {
            $mask .= str_repeat('ff', 4 - $bytesToAnonymize);
            $mask .= str_repeat('00', $bytesToAnonymize);
            return '::' . implode(':', str_split($mask, 4));
        };
        $packedAddress = inet_pton($ip);
        if (4 === \strlen($packedAddress)) {
            $mask = rtrim(str_repeat('255.', 4 - $v4Bytes) . str_repeat('0.', $v4Bytes), '.');
        }
        elseif ($ip === inet_ntop($packedAddress & inet_pton('::ffff:ffff:ffff'))) {
            $mask = $mappedIpV4MaskGenerator('ffff', $v4Bytes);
        }
        elseif ($ip === inet_ntop($packedAddress & inet_pton('::ffff:ffff'))) {
            $mask = $mappedIpV4MaskGenerator('', $v4Bytes);
        }
        else {
            $mask = str_repeat('ff', 16 - $v6Bytes) . str_repeat('00', $v6Bytes);
            $mask = implode(':', str_split($mask, 4));
        }
        $ip = inet_ntop($packedAddress & inet_pton($mask));
        if ($wrappedIPv6) {
            $ip = '[' . $ip . ']';
        }
        return $ip;
    }
    
    /**
     * Checks if an IPv4 or IPv6 address is contained in the list of private IP subnets.
     */
    public static function isPrivateIp(string $requestIp) : bool {
        return self::checkIp($requestIp, self::PRIVATE_SUBNETS);
    }
    private static function getCacheResult(string $cacheKey) : ?bool {
        if (isset(self::$checkedIps[$cacheKey])) {
            // Move the item last in cache (LRU)
            $value = self::$checkedIps[$cacheKey];
            unset(self::$checkedIps[$cacheKey]);
            self::$checkedIps[$cacheKey] = $value;
            return self::$checkedIps[$cacheKey];
        }
        return null;
    }
    private static function setCacheResult(string $cacheKey, bool $result) : bool {
        if (1000 < \count(self::$checkedIps)) {
            // stop memory leak if there are many keys
            self::$checkedIps = \array_slice(self::$checkedIps, 500, null, true);
        }
        return self::$checkedIps[$cacheKey] = $result;
    }

}