/*
 * Copyright 2017-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.opencord.aaa.impl;

import org.onlab.packet.DeserializationException;
import org.onlab.packet.EthType;
import org.onlab.packet.Ethernet;
import org.onlab.packet.RADIUS;
import org.onosproject.core.ApplicationId;
import org.onosproject.net.flow.DefaultTrafficSelector;
import org.onosproject.net.flow.TrafficSelector;
import org.onosproject.net.packet.InboundPacket;
import org.onosproject.net.packet.PacketContext;
import org.onosproject.net.packet.PacketService;
import org.opencord.aaa.AaaConfig;
import org.opencord.aaa.RadiusCommunicator;
import org.slf4j.Logger;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.InetSocketAddress;
import java.net.SocketException;
import java.net.UnknownHostException;
import java.util.concurrent.ExecutorService;

import static java.util.concurrent.Executors.newSingleThreadExecutor;
import static org.onlab.util.Tools.groupedThreads;
import static org.onosproject.net.packet.PacketPriority.CONTROL;
import static org.slf4j.LoggerFactory.getLogger;

/**
 * Handles Socket based communication with the RADIUS server.
 */
public class SocketBasedRadiusCommunicator implements RadiusCommunicator {

    // for verbose output
    private final Logger log = getLogger(getClass());

    // our unique identifier
    private ApplicationId appId;

    // to receive Packet-in events that we'll respond to
    PacketService packetService;

    // Socket used for UDP communications with RADIUS server
    private DatagramSocket radiusSocket;

    private String radiusHost;

    // Parsed RADIUS server addresses
    protected InetAddress radiusIpAddress;

    // RADIUS server TCP port number
    protected short radiusServerPort;

    // Executor for RADIUS communication thread
    private ExecutorService executor;

    // Worker thread for RADIUS communication
    private ExecutorService worker;

    // To track the received packets
    int packetNumber = 1;

    AaaManager aaaManager;

    SocketBasedRadiusCommunicator(ApplicationId appId, PacketService pktService,
                                  AaaManager aaaManager) {
        this.appId = appId;
        this.packetService = pktService;
        this.aaaManager = aaaManager;
    }

    @Override
    public void initializeLocalState(AaaConfig newCfg) {
        if (newCfg.radiusIp() != null) {
            radiusIpAddress = newCfg.radiusIp();
        }
        radiusServerPort = newCfg.radiusServerUdpPort();
        radiusHost = newCfg.radiusHostName();

        try {
            radiusSocket = new DatagramSocket(null);
            radiusSocket.setReuseAddress(true);
            radiusSocket.bind(new InetSocketAddress(radiusServerPort));
        } catch (Exception ex) {
            log.error("Can't open RADIUS socket", ex);
        }

        log.info("Remote RADIUS Server: {}:{}", radiusIpAddress, radiusServerPort);

        executor = newSingleThreadExecutor(groupedThreads("onos/aaa", "radius-%d", log));
        executor.execute(radiusListener);
        worker = newSingleThreadExecutor(groupedThreads("onos/aaa", "radius-packet-%d", log));
    }

    @Override
    public void clearLocalState() {
        log.info("Closing RADIUS socket: {}:{}", radiusIpAddress, radiusServerPort);
        radiusSocket.close();
        executor.shutdownNow();
        worker.shutdownNow();
    }

    @Override
    public void deactivate() {
       clearLocalState();
    }

    @Override
    public void requestIntercepts() {
        TrafficSelector.Builder selector = DefaultTrafficSelector.builder();
        selector.matchEthType(EthType.EtherType.EAPOL.ethType().toShort());
        packetService.requestPackets(selector.build(), CONTROL, appId);
    }

    @Override
    public void withdrawIntercepts() {
        TrafficSelector.Builder selector = DefaultTrafficSelector.builder();
        selector.matchEthType(EthType.EtherType.EAPOL.ethType().toShort());
        packetService.cancelPackets(selector.build(), CONTROL, appId);
    }

    @Override
    public void sendRadiusPacket(RADIUS radiusPacket, InboundPacket inPkt) {
        try {
            final byte[] data = radiusPacket.serialize();
            final DatagramSocket socket = radiusSocket;

            try {
                InetAddress address;
                if (radiusHost != null) {
                    address = InetAddress.getByName(radiusHost);
                } else {
                    address = radiusIpAddress;
                }
                DatagramPacket packet =
                        new DatagramPacket(data, data.length, address, radiusServerPort);
                if (log.isTraceEnabled()) {
                    log.trace("Sending packet {} to Radius Server {}:{} using socket",
                              radiusPacket, address, radiusServerPort);
                }
                socket.send(packet);
                aaaManager.radiusOperationalStatusService.setStatusServerReqSent(true);
            } catch (UnknownHostException uhe) {
                log.warn("Unable to resolve host {}", radiusHost);
                aaaManager.radiusOperationalStatusService.setStatusServerReqSent(false);
            }
        } catch (IOException e) {
            log.error("Cannot send packet to RADIUS server", e);
        }
    }

    // in the socket base case we don't care about packets coming from the server as nothing meaningful will be
    // received from the southbound
    @Override
    public void handlePacketFromServer(PacketContext context) {
        InboundPacket pkt = context.inPacket();
        Ethernet ethPkt = pkt.parsed();
        if (log.isTraceEnabled() && ethPkt.getEtherType() != Ethernet.TYPE_LLDP
                && ethPkt.getEtherType() != Ethernet.TYPE_BSN) {
            log.trace("Skipping Ethernet packet type {}",
                      EthType.EtherType.lookup(ethPkt.getEtherType()));
        }
    }

    // Handle radius packet for further processing
    private void handleRadiusPacketInternal(DatagramPacket inboundBasePacket) {
        RADIUS inboundRadiusPacket;
        aaaManager.checkForPacketFromUnknownServer(inboundBasePacket.getAddress().getHostAddress());
        log.debug("Packet #{} received", packetNumber++);
        try {
            inboundRadiusPacket = RADIUS.deserializer().deserialize(inboundBasePacket.getData(),
                    0, inboundBasePacket.getLength());
            if (log.isTraceEnabled()) {
                log.trace("Handling inboundRadiusPacket {} with identifier {}", inboundRadiusPacket,
                    inboundRadiusPacket.getIdentifier() & 0xff);
            }
            aaaManager.aaaStatisticsManager.handleRoundtripTime(inboundRadiusPacket.getIdentifier());
            aaaManager.handleRadiusPacket(inboundRadiusPacket);
        } catch (DeserializationException dex) {
            aaaManager.aaaStatisticsManager.getAaaStats().increaseMalformedResponsesRx();
            log.warn("Cannot deserialize packet", dex);
        }
    }

    class RadiusListener implements Runnable {

        @Override
        public void run() {
            boolean done = false;
            try {
                log.info("UDP listener thread starting up, socket buffer size {}",
                         radiusSocket.getReceiveBufferSize());
            } catch (SocketException e) {
                log.error("Socket exception", e);
            }
            while (!done) {
                try {
                    byte[] packetBuffer = new byte[RADIUS.RADIUS_MAX_LENGTH];
                    DatagramPacket inboundBasePacket = new DatagramPacket(packetBuffer, packetBuffer.length);
                    DatagramSocket socket = radiusSocket;
                    socket.receive(inboundBasePacket);
                    worker.execute(() -> handleRadiusPacketInternal(inboundBasePacket));

                } catch (IOException e) {
                    log.warn("Socket was closed, exiting listener thread");
                    done = true;
                } catch (Exception e) {
                    log.error("RadiusListener thread thrown an exception: {}", e.getMessage(), e);
                }
            }
            log.info("UDP listener thread shutting down");
        }
    }

    RadiusListener radiusListener = new RadiusListener();
}