/*
 * Copyright 2016-present Open Networking Laboratory
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.onosproject.lisp.ctl;

import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import org.onosproject.lisp.msg.authentication.LispAuthenticationFactory;
import org.onosproject.lisp.msg.exceptions.LispWriterException;
import org.onosproject.lisp.msg.protocols.DefaultLispMapNotify.DefaultNotifyBuilder;
import org.onosproject.lisp.msg.protocols.DefaultLispMapRegister.DefaultRegisterBuilder;
import org.onosproject.lisp.msg.protocols.LispEidRecord;
import org.onosproject.lisp.msg.protocols.LispMapNotify;
import org.onosproject.lisp.msg.protocols.LispMapNotify.NotifyBuilder;
import org.onosproject.lisp.msg.protocols.LispMapRegister;
import org.onosproject.lisp.msg.protocols.LispMapRegister.RegisterBuilder;
import org.onosproject.lisp.msg.protocols.LispMessage;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.net.InetSocketAddress;
import java.util.Arrays;

import static org.onosproject.lisp.msg.authentication.LispAuthenticationKeyEnum.valueOf;

/**
 * LISP map server class.
 * Handles map-register message and acknowledges with map-notify message.
 */
public class LispMapServer {

    private static final int NOTIFY_PORT = 4342;

    // TODO: need to be configurable
    private static final String AUTH_KEY = "onos";

    private static final short AUTH_DATA_LENGTH = 20;

    // TODO: need to be configurable
    private static final short AUTH_METHOD = 1;

    private static final Logger log = LoggerFactory.getLogger(LispMapServer.class);

    private LispAuthenticationFactory factory;
    private LispEidRlocMap mapInfo;

    public LispMapServer() {
        factory = LispAuthenticationFactory.getInstance();
        mapInfo = LispEidRlocMap.getInstance();
    }

    /**
     * Handles map-register message and replies with map-notify message.
     *
     * @param message map-register message
     * @return map-notify message
     */
    public LispMapNotify processMapRegister(LispMessage message) {

        LispMapRegister register = (LispMapRegister) message;

        if (!checkAuthData(register)) {
            log.warn("Unmatched authentication data of Map-Register");
            return null;
        }

        // build temp notify message
        NotifyBuilder authNotifyBuilder = new DefaultNotifyBuilder();
        authNotifyBuilder.withKeyId(AUTH_METHOD);
        authNotifyBuilder.withAuthDataLength(AUTH_DATA_LENGTH);
        authNotifyBuilder.withNonce(register.getNonce());
        authNotifyBuilder.withMapRecords(register.getMapRecords());

        byte[] authData = new byte[AUTH_DATA_LENGTH];
        Arrays.fill(authData, (byte) 0);
        authNotifyBuilder.withAuthenticationData(authData);

        ByteBuf byteBuf = Unpooled.buffer();
        try {
            authNotifyBuilder.build().writeTo(byteBuf);
        } catch (LispWriterException e) {
            e.printStackTrace();
        }

        byte[] bytes = new byte[byteBuf.readableBytes()];
        byteBuf.readBytes(bytes);

        byte[] sha1AuthData =
                factory.createAuthenticationData(valueOf(register.getKeyId()), AUTH_KEY, bytes);

        NotifyBuilder notifyBuilder = new DefaultNotifyBuilder();
        notifyBuilder.withKeyId(AUTH_METHOD);
        notifyBuilder.withAuthDataLength((short) sha1AuthData.length);
        notifyBuilder.withAuthenticationData(sha1AuthData);
        notifyBuilder.withNonce(register.getNonce());
        notifyBuilder.withMapRecords(register.getMapRecords());

        LispMapNotify notify = notifyBuilder.build();

        InetSocketAddress address =
                new InetSocketAddress(register.getSender().getAddress(), NOTIFY_PORT);
        notify.configSender(address);

        register.getMapRecords().forEach(record -> {
            LispEidRecord eidRecord =
                    new LispEidRecord(record.getMaskLength(), record.getEidPrefixAfi());
            mapInfo.insertMapRecord(eidRecord, record);
        });

        return notify;
    }

    /**
     * Checks the integrity of the received Map-Register message by calculating
     * authentication data from received Map-Register message.
     *
     * @param register Map-Register message
     * @return evaluation result
     */
    private boolean checkAuthData(LispMapRegister register) {
        ByteBuf byteBuf = Unpooled.buffer();
        RegisterBuilder registerBuilder = new DefaultRegisterBuilder();
        registerBuilder.withKeyId(register.getKeyId());
        registerBuilder.withAuthDataLength(register.getAuthDataLength());
        registerBuilder.withNonce(register.getNonce());
        registerBuilder.withIsProxyMapReply(register.isProxyMapReply());
        registerBuilder.withIsWantMapNotify(register.isWantMapNotify());
        registerBuilder.withMapRecords(register.getMapRecords());

        byte[] authData = register.getAuthenticationData();
        if (authData != null) {
            authData = authData.clone();
            Arrays.fill(authData, (byte) 0);
        }
        registerBuilder.withAuthenticationData(authData);
        try {
            registerBuilder.build().writeTo(byteBuf);
        } catch (LispWriterException e) {
            e.printStackTrace();
        }

        byte[] bytes = new byte[byteBuf.readableBytes()];
        byteBuf.readBytes(bytes);

        byte[] calculatedAuthData =
                factory.createAuthenticationData(valueOf(register.getKeyId()), AUTH_KEY, bytes);
        return Arrays.equals(calculatedAuthData, register.getAuthenticationData());
    }
}