private OptionalInt getUID()

in emr-user-role-mapper-application/src/main/java/com/amazon/aws/emr/common/system/user/LinuxUserIdService.java [127:167]
35 lines of code
14 McCabe index (conditional complexity)

    private OptionalInt getUID(String line, String remoteAddr,
                               int reqLocalPort, int reqRemotePort,
                               boolean isNativeIMDSApi) {
        Matcher matcher = pattern.matcher(line);
        if (!matcher.matches()) {
            return OptionalInt.empty();
        }

        int groupCount = matcher.groupCount();
        if (groupCount <= 5) {
            return OptionalInt.empty();
        }

        long procLocalPort = Long.parseLong(matcher.group(2), 16);
        String procRemoteAddress = matcher.group(3);
        long procRemotePort = Long.parseLong(matcher.group(4), 16);
        long state = Long.parseLong(matcher.group(5), 16);
        int uid = Integer.parseInt(matcher.group(6));

        if (isNativeIMDSApi) {
            if ((procRemoteAddress.equals(Constants.Network.IPV4_IMDS_ADDR_IN_HEX_REVERSED_BYTE_ORDER) ||
                    procRemoteAddress.equals(Constants.Network.IPV6_IMDS_ADDR_IN_HEX_REVERSED_BYTE_ORDER))
                    && procLocalPort == reqRemotePort
                    && procRemotePort == 80
                    && state == TCP_ESTABLISHED
            ) {
                return OptionalInt.of(uid);
            }
        } else {
            // Socket established directly from caller process to the server for below use cases:
            // 1/ impersonation request from EMR-FS
            if ((procLocalPort == reqRemotePort && procRemotePort == Constants.JETTY_PORT)
                    && (procRemoteAddress.equals(Constants.Network.IPV4_LOCALHOST_ADDR_IN_HEX_REVERSED_BYTE_ORDER)
                    || procRemoteAddress.equals(Constants.Network.IPV6_LOCALHOST_ADDR_IN_HEX_REVERSED_BYTE_ORDER)
                    || procRemoteAddress.equals(Constants.Network.IPV4_MAPPED_IPV6_LOCALHOST_ADDR_IN_HEX_REVERSED_BYTE_ORDER))) {
                return OptionalInt.of(uid);
            }
        }

        return OptionalInt.empty();
    }