/*
 * Copyright 2015-present Open Networking Foundation
 *
 * 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.ovsdb.controller.impl;

import io.netty.bootstrap.Bootstrap;
import io.netty.bootstrap.ServerBootstrap;
import io.netty.buffer.PooledByteBufAllocator;
import io.netty.channel.Channel;
import io.netty.channel.ChannelDuplexHandler;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelFutureListener;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelOption;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.EventLoop;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.ServerChannel;
import io.netty.channel.group.ChannelGroup;
import io.netty.channel.group.DefaultChannelGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;
import io.netty.handler.codec.string.StringEncoder;
import io.netty.handler.timeout.IdleState;
import io.netty.handler.timeout.IdleStateEvent;
import io.netty.handler.timeout.IdleStateHandler;
import io.netty.util.CharsetUtil;

import static org.onlab.util.Tools.groupedThreads;

import java.io.FileInputStream;
import java.io.IOException;
import java.net.InetSocketAddress;
import java.security.KeyManagementException;
import java.security.KeyStore;
import java.security.KeyStoreException;
import java.security.NoSuchAlgorithmException;
import java.security.UnrecoverableKeyException;
import java.security.cert.CertificateException;
import java.util.Objects;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.function.Consumer;

import io.netty.util.concurrent.GlobalEventExecutor;
import org.onlab.packet.IpAddress;
import org.onlab.packet.TpPort;
import org.onlab.util.Tools;
import org.onosproject.ovsdb.controller.OvsdbConstant;
import org.onosproject.ovsdb.controller.OvsdbNodeId;
import org.onosproject.ovsdb.controller.driver.DefaultOvsdbClient;
import org.onosproject.ovsdb.controller.driver.OvsdbAgent;
import org.onosproject.ovsdb.controller.driver.OvsdbProviderService;
import org.onosproject.ovsdb.rfc.jsonrpc.Callback;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import javax.net.ssl.KeyManagerFactory;
import javax.net.ssl.SSLContext;
import javax.net.ssl.TrustManagerFactory;

/**
 * The main controller class. Handles all setup and network listeners -
 * distributed OVSDBClient.
 */
public class Controller {
    private static final Logger log = LoggerFactory
            .getLogger(Controller.class);

    private int ovsdbPort = OvsdbConstant.OVSDBPORT;

    private OvsdbAgent agent;
    private Callback monitorCallback;

    private final ExecutorService executorService = Executors
            .newFixedThreadPool(10, groupedThreads("OVSDB-C", "executor-%d", log));

    private EventLoopGroup bossGroup;
    private EventLoopGroup workerGroup;
    private Class<? extends ServerChannel> serverChannelClass;

    private static final int MAX_RETRY = 5;
    private static final int IDLE_TIMEOUT_SEC = 10;

    private ChannelGroup cg;

    protected static final int SEND_BUFFER_SIZE = 4 * 1024 * 1024;

    protected TlsParams tlsParams = new TlsParams();
    protected SSLContext sslContext;
    protected KeyStore keyStore;

    protected static final short MIN_KS_LENGTH = 6;
    private static final String JAVA_KEY_STORE = "JKS";

    /**
     * Initialization.
     */
    private void initEventLoopGroup() {
        bossGroup = new NioEventLoopGroup(0, Tools.groupedThreads("OVSDB-C", "boss-%d", log));
        workerGroup = new NioEventLoopGroup(0, Tools.groupedThreads("OVSDB-C", "worker-%d", log));
        serverChannelClass = NioServerSocketChannel.class;
    }

    /**
     * Accepts incoming connections.
     */
    private void startAcceptingConnections() throws InterruptedException {
        if (cg == null) {
            return;
        }
        final ServerBootstrap b = new ServerBootstrap();

        b.group(bossGroup, workerGroup).channel(serverChannelClass)
                .childHandler(new OvsdbChannelInitializer(this, sslContext));
        b.option(ChannelOption.SO_REUSEADDR, true);
        b.option(ChannelOption.SO_BACKLOG, 128);
        b.option(ChannelOption.ALLOCATOR, PooledByteBufAllocator.DEFAULT);
        b.childOption(ChannelOption.SO_SNDBUF, Controller.SEND_BUFFER_SIZE);
        b.childOption(ChannelOption.SO_KEEPALIVE, true);

        cg.add(b.bind(ovsdbPort).syncUninterruptibly().channel());
    }

    /**
     * Tells controller that we're ready to accept OVSDB node loop.
     * @throws InterruptedException if thread is interrupted
     */
    public void run() throws InterruptedException {
        initEventLoopGroup();
        startAcceptingConnections();
    }

    /**
     * Adds channel pipeline to handle a new connected node.
     */
    private class OnosCommunicationChannelInitializer
            extends ChannelInitializer<SocketChannel> {
        @Override
        protected void initChannel(SocketChannel channel) throws Exception {
            log.info("New channel created");
            channel.pipeline().addLast(new StringEncoder(CharsetUtil.UTF_8));
            channel.pipeline().addLast(new MessageDecoder());
            handleNewNodeConnection(channel);

        }
    }

    /**
     * Sets new TLS parameters.
     *
     * @param newTlsParams Modified Tls Params
     * @return true if restart is required
     */
    protected boolean setTlsParameters(TlsParams newTlsParams) {
        TlsParams oldParams = this.tlsParams;
        this.tlsParams = newTlsParams;
        return !Objects.equals(this.tlsParams, oldParams); // restart if TLS params change
    }

    /**
     * Handles the new connection of node.
     *
     * @param channel the channel to use.
     */
    protected void handleNewNodeConnection(final Channel channel) {
        executorService.execute(() -> {
            log.info("Handle new node connection");

            IpAddress ipAddress = IpAddress
                    .valueOf(((InetSocketAddress) channel.remoteAddress())
                            .getAddress().getHostAddress());
            long port = ((InetSocketAddress) channel.remoteAddress())
                    .getPort();

            log.info("Get connection from ip address {} : {}",
                     ipAddress.toString(), port);

            OvsdbNodeId nodeId = new OvsdbNodeId(ipAddress, port);
            OvsdbProviderService ovsdbProviderService = getNodeInstance(nodeId,
                                                                        agent,
                                                                        monitorCallback,
                                                                        channel);
            ovsdbProviderService.setConnection(true);
            OvsdbJsonRpcHandler ovsdbJsonRpcHandler = new OvsdbJsonRpcHandler(
                                                                              nodeId);
            ovsdbJsonRpcHandler
                    .setOvsdbProviderService(ovsdbProviderService);
            channel.pipeline().addLast(ovsdbJsonRpcHandler);

            ovsdbProviderService.nodeAdded();
            ChannelFuture closeFuture = channel.closeFuture();
            closeFuture
                    .addListener(new ChannelConnectionListener(
                                                               ovsdbProviderService));
        });
    }

    /**
     * Gets an OVSDB client instance.
     *
     * @param nodeId data OVSDB node id
     * @param agent OvsdbAgent
     * @param monitorCallback Callback
     * @param channel Channel
     * @return OvsdbProviderService instance
     */
    protected OvsdbProviderService getNodeInstance(OvsdbNodeId nodeId,
                                                   OvsdbAgent agent,
                                                   Callback monitorCallback,
                                                   Channel channel) {
        OvsdbProviderService ovsdbProviderService = new DefaultOvsdbClient(
                                                                           nodeId);
        ovsdbProviderService.setAgent(agent);
        ovsdbProviderService.setCallback(monitorCallback);
        ovsdbProviderService.setChannel(channel);
        return ovsdbProviderService;
    }

    /**
     * Starts controller.
     *
     * @param agent OvsdbAgent
     * @param monitorCallback Callback
     * @param mode OVSDB server mode flag
     */
    public void start(OvsdbAgent agent, Callback monitorCallback, boolean mode) {
        this.agent = agent;
        this.monitorCallback = monitorCallback;
        // if the OVSDB server flag is configured as false, we do NOT listen on 6640 port
        // therefore, ONOS only runs as an OVSDB client
        if (mode) {
            try {
                this.init();
                this.run();
            } catch (InterruptedException e) {
                log.warn("Interrupted while waiting to start");
                Thread.currentThread().interrupt();
            }
        }
    }

    /**
     * Stops controller.
     *
     */
    public void stop() {
        if (cg != null) {
            cg.close();
            cg = null;

            workerGroup.shutdownGracefully();
            bossGroup.shutdownGracefully();
            // Wait until all threads are terminated.
            try {
                bossGroup.terminationFuture().sync();
                workerGroup.terminationFuture().sync();
            } catch (InterruptedException e) {
                log.warn("Interrupted while stopping", e);
                Thread.currentThread().interrupt();
            }
        }
    }

    /**
     * Connect to the ovsdb server with given ip address and port number.
     *
     * @param ip ip address
     * @param port port number
     */
    public void connect(IpAddress ip, TpPort port) {
        connect(ip, port, e -> log.warn("Connection to the ovsdb {}:{} failed(cause: {})", ip, port, e));
    }

    /**
     * Connect to the ovsdb server with given ip address, port number, and failhandler.
     *
     * @param ip ip address
     * @param port port number
     * @param failhandler connection failure handler
     */
    public void connect(IpAddress ip, TpPort port, Consumer<Exception> failhandler) {
        ChannelFutureListener listener = new ConnectionListener(this, ip, port, failhandler);
        try {
            connectRetry(ip, port, listener);
        } catch (Exception e) {
            failhandler.accept(e);
        }
    }

    private void connectRetry(IpAddress ip, TpPort port, ChannelFutureListener listener) {
        Bootstrap b = new Bootstrap();
        b.group(workerGroup)
                .channel(NioSocketChannel.class)
                .option(ChannelOption.TCP_NODELAY, true)
                .handler(new ChannelInitializer<SocketChannel>() {

                    @Override
                    protected void initChannel(SocketChannel channel) throws Exception {
                        ChannelPipeline pipeline = channel.pipeline();
                        pipeline.addLast(new StringEncoder(CharsetUtil.UTF_8));
                        pipeline.addLast(new MessageDecoder());
                        pipeline.addLast(new IdleStateHandler(IDLE_TIMEOUT_SEC, 0, 0));
                        pipeline.addLast(new ConnectionHandler());
                    }
                });
        b.remoteAddress(ip.toString(), port.toInt());
        b.connect().addListener(listener);
    }

    private class ConnectionListener implements ChannelFutureListener {
        private Controller controller;
        private IpAddress ip;
        private TpPort port;
        private AtomicInteger count = new AtomicInteger();
        private Consumer<Exception> failhandler;

        public ConnectionListener(Controller controller,
                                  IpAddress ip,
                                  TpPort port,
                                  Consumer<Exception> failhandler) {
            this.controller = controller;
            this.ip = ip;
            this.port = port;
            this.failhandler = failhandler;
        }

        @Override
        public void operationComplete(ChannelFuture channelFuture) throws Exception {
            if (!channelFuture.isSuccess()) {
                channelFuture.channel().close();

                if (count.incrementAndGet() < MAX_RETRY) {
                    final EventLoop loop = channelFuture.channel().eventLoop();

                    loop.schedule(() -> {
                        try {
                            controller.connectRetry(this.ip, this.port, this);
                        } catch (Exception e) {
                            log.warn("Connection to the ovsdb server {}:{} failed(cause: {})", ip, port, e);
                        }
                    }, 1L, TimeUnit.SECONDS);
                } else {
                    failhandler.accept(new Exception("max connection retry(" + MAX_RETRY + ") exceeded"));
                }
            } else {
                handleNewNodeConnection(channelFuture.channel());
            }
        }
    }

    private class ConnectionHandler extends ChannelDuplexHandler {

        @Override
        public void userEventTriggered(ChannelHandlerContext ctx, Object evt) throws Exception {
            IdleStateEvent e = (IdleStateEvent) evt;

            if (e.state() == IdleState.READER_IDLE) {
                ctx.close();
            }
        }
    }

    /**
     * Initialize internal data structures.
     */
    public void init() {
        cg = new DefaultChannelGroup(GlobalEventExecutor.INSTANCE);

        if (tlsParams.isTlsEnabled()) {
            initSsl();
        }

    }

    private void initSsl()  {
        try {
            TrustManagerFactory tmFactory = TrustManagerFactory.getInstance(TrustManagerFactory.getDefaultAlgorithm());
            KeyStore ts = KeyStore.getInstance(JAVA_KEY_STORE);
            ts.load(new FileInputStream(tlsParams.tsLocation), tlsParams.tsPwd());
            tmFactory.init(ts);

            KeyManagerFactory kmf = KeyManagerFactory.getInstance(KeyManagerFactory.getDefaultAlgorithm());
            keyStore = KeyStore.getInstance(JAVA_KEY_STORE);
            keyStore.load(new FileInputStream(tlsParams.ksLocation), tlsParams.ksPwd());
            kmf.init(keyStore, tlsParams.ksPwd());

            sslContext = SSLContext.getInstance("TLS");
            sslContext.init(kmf.getKeyManagers(), tmFactory.getTrustManagers(), null);
        } catch (NoSuchAlgorithmException | KeyStoreException | CertificateException |
                IOException | KeyManagementException | UnrecoverableKeyException ex) {
            log.error("SSL init failed: {}", ex.getMessage());
        }
    }
}