/*
 * Copyright 2016-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.dhcprelay;

import java.nio.ByteBuffer;
import java.util.Collection;
import java.util.Collections;
import java.util.Dictionary;
import java.util.List;
import java.util.Objects;
import java.util.Optional;
import java.util.Set;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.stream.Stream;

import org.apache.felix.scr.annotations.Activate;
import org.apache.felix.scr.annotations.Component;
import org.apache.felix.scr.annotations.Deactivate;
import org.apache.felix.scr.annotations.Modified;
import org.apache.felix.scr.annotations.Property;
import org.apache.felix.scr.annotations.Reference;
import org.apache.felix.scr.annotations.ReferenceCardinality;
import org.apache.felix.scr.annotations.Service;
import org.onlab.packet.ARP;
import org.onlab.packet.DHCP;
import org.onlab.packet.DHCP6;
import org.onlab.packet.Ethernet;
import org.onlab.packet.IPacket;
import org.onlab.packet.IPv4;
import org.onlab.packet.IPv6;
import org.onlab.packet.Ip4Address;
import org.onlab.packet.MacAddress;
import org.onlab.packet.TpPort;
import org.onlab.packet.UDP;
import org.onlab.packet.VlanId;
import org.onlab.util.Tools;
import org.onosproject.cfg.ComponentConfigService;
import org.onosproject.core.ApplicationId;
import org.onosproject.core.CoreService;
import org.onosproject.dhcprelay.api.DhcpHandler;
import org.onosproject.dhcprelay.api.DhcpRelayService;
import org.onosproject.dhcprelay.config.DefaultDhcpRelayConfig;
import org.onosproject.dhcprelay.config.DhcpServerConfig;
import org.onosproject.dhcprelay.config.IgnoreDhcpConfig;
import org.onosproject.dhcprelay.config.IndirectDhcpRelayConfig;
import org.onosproject.dhcprelay.store.DhcpRecord;
import org.onosproject.dhcprelay.store.DhcpRelayStore;
import org.onosproject.net.ConnectPoint;
import org.onosproject.net.Device;
import org.onosproject.net.DeviceId;
import org.onosproject.net.Host;
import org.onosproject.net.HostId;
import org.onosproject.net.config.Config;
import org.onosproject.net.config.ConfigFactory;
import org.onosproject.net.config.NetworkConfigEvent;
import org.onosproject.net.config.NetworkConfigListener;
import org.onosproject.net.config.NetworkConfigRegistry;
import org.onosproject.net.flow.DefaultTrafficSelector;
import org.onosproject.net.flow.DefaultTrafficTreatment;
import org.onosproject.net.flow.TrafficSelector;
import org.onosproject.net.flow.TrafficTreatment;
import org.onosproject.net.behaviour.Pipeliner;
import org.onosproject.net.device.DeviceEvent;
import org.onosproject.net.device.DeviceListener;
import org.onosproject.net.device.DeviceService;
import org.onosproject.net.flow.criteria.Criterion;
import org.onosproject.net.flow.criteria.UdpPortCriterion;
import org.onosproject.net.flowobjective.DefaultForwardingObjective;
import org.onosproject.net.flowobjective.FlowObjectiveService;
import org.onosproject.net.flowobjective.ForwardingObjective;
import org.onosproject.net.flowobjective.Objective;
import org.onosproject.net.flowobjective.ObjectiveContext;
import org.onosproject.net.flowobjective.ObjectiveError;
import org.onosproject.net.host.HostService;
import org.onosproject.net.intf.Interface;
import org.onosproject.net.intf.InterfaceService;
import org.onosproject.net.packet.DefaultOutboundPacket;
import org.onosproject.net.packet.OutboundPacket;
import org.onosproject.net.packet.PacketContext;
import org.onosproject.net.packet.PacketPriority;
import org.onosproject.net.packet.PacketProcessor;
import org.onosproject.net.packet.PacketService;
import org.onosproject.net.provider.ProviderId;
import org.osgi.service.component.ComponentContext;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.google.common.collect.HashMultimap;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.Multimap;

import static org.onosproject.net.config.basics.SubjectFactories.APP_SUBJECT_FACTORY;
import static org.onosproject.net.flowobjective.Objective.Operation.ADD;
import static org.onosproject.net.flowobjective.Objective.Operation.REMOVE;

/**
 * DHCP Relay Agent Application Component.
 */
@Component(immediate = true)
@Service
public class DhcpRelayManager implements DhcpRelayService {
    public static final String DHCP_RELAY_APP = "org.onosproject.dhcprelay";
    public static final ProviderId PROVIDER_ID = new ProviderId("host", DHCP_RELAY_APP);
    public static final String HOST_LOCATION_PROVIDER =
            "org.onosproject.provider.host.impl.HostLocationProvider";
    public static final String ROUTE_STORE_IMPL =
            "org.onosproject.routeservice.store.RouteStoreImpl";
    private static final TrafficSelector DHCP_SERVER_SELECTOR = DefaultTrafficSelector.builder()
            .matchEthType(Ethernet.TYPE_IPV4)
            .matchIPProtocol(IPv4.PROTOCOL_UDP)
            .matchUdpDst(TpPort.tpPort(UDP.DHCP_SERVER_PORT))
            .build();
    private static final TrafficSelector DHCP_CLIENT_SELECTOR = DefaultTrafficSelector.builder()
            .matchEthType(Ethernet.TYPE_IPV4)
            .matchIPProtocol(IPv4.PROTOCOL_UDP)
            .matchUdpDst(TpPort.tpPort(UDP.DHCP_CLIENT_PORT))
            .build();
    private static final TrafficSelector DHCP6_SERVER_SELECTOR = DefaultTrafficSelector.builder()
            .matchEthType(Ethernet.TYPE_IPV6)
            .matchIPProtocol(IPv4.PROTOCOL_UDP)
            .matchUdpDst(TpPort.tpPort(UDP.DHCP_V6_SERVER_PORT))
            .build();
    private static final TrafficSelector DHCP6_CLIENT_SELECTOR = DefaultTrafficSelector.builder()
            .matchEthType(Ethernet.TYPE_IPV6)
            .matchIPProtocol(IPv4.PROTOCOL_UDP)
            .matchUdpDst(TpPort.tpPort(UDP.DHCP_V6_CLIENT_PORT))
            .build();
    static final List<TrafficSelector> DHCP_SELECTORS = ImmutableList.of(
            DHCP_SERVER_SELECTOR,
            DHCP_CLIENT_SELECTOR,
            DHCP6_SERVER_SELECTOR,
            DHCP6_CLIENT_SELECTOR
    );
    private static final TrafficSelector ARP_SELECTOR = DefaultTrafficSelector.builder()
            .matchEthType(Ethernet.TYPE_ARP)
            .build();
    private static final int IGNORE_CONTROL_PRIORITY = PacketPriority.CONTROL.priorityValue() + 1000;
    private final Logger log = LoggerFactory.getLogger(getClass());
    private final InternalConfigListener cfgListener = new InternalConfigListener();

    private final Set<ConfigFactory> factories = ImmutableSet.of(
            new ConfigFactory<ApplicationId, DefaultDhcpRelayConfig>(APP_SUBJECT_FACTORY,
                                                                     DefaultDhcpRelayConfig.class,
                                                                     DefaultDhcpRelayConfig.KEY,
                                                                     true) {
                @Override
                public DefaultDhcpRelayConfig createConfig() {
                    return new DefaultDhcpRelayConfig();
                }
            },
            new ConfigFactory<ApplicationId, IndirectDhcpRelayConfig>(APP_SUBJECT_FACTORY,
                                                                      IndirectDhcpRelayConfig.class,
                                                                      IndirectDhcpRelayConfig.KEY,
                                                                      true) {
                @Override
                public IndirectDhcpRelayConfig createConfig() {
                    return new IndirectDhcpRelayConfig();
                }
            },
            new ConfigFactory<ApplicationId, IgnoreDhcpConfig>(APP_SUBJECT_FACTORY,
                                                               IgnoreDhcpConfig.class,
                                                               IgnoreDhcpConfig.KEY,
                                                               true) {
                @Override
                public IgnoreDhcpConfig createConfig() {
                    return new IgnoreDhcpConfig();
                }
            }
    );

    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
    protected NetworkConfigRegistry cfgService;

    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
    protected CoreService coreService;

    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
    protected PacketService packetService;

    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
    protected HostService hostService;

    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
    protected InterfaceService interfaceService;

    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
    protected DhcpRelayStore dhcpRelayStore;

    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
    protected ComponentConfigService compCfgService;

    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
    protected FlowObjectiveService flowObjectiveService;

    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
    protected DeviceService deviceService;

    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY,
            target = "(version=4)")
    protected DhcpHandler v4Handler;

    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY,
            target = "(version=6)")
    protected DhcpHandler v6Handler;

    @Property(name = "arpEnabled", boolValue = true,
            label = "Enable Address resolution protocol")
    protected boolean arpEnabled = true;

    protected Multimap<DeviceId, VlanId> ignoredVlans = HashMultimap.create();
    protected DeviceListener deviceListener = new InternalDeviceListener();
    private DhcpRelayPacketProcessor dhcpRelayPacketProcessor = new DhcpRelayPacketProcessor();
    private ApplicationId appId;

    @Activate
    protected void activate(ComponentContext context) {
        //start the dhcp relay agent
        appId = coreService.registerApplication(DHCP_RELAY_APP);

        cfgService.addListener(cfgListener);
        factories.forEach(cfgService::registerConfigFactory);
        //update the dhcp server configuration.
        updateConfig();

        //add the packet processor
        packetService.addProcessor(dhcpRelayPacketProcessor, PacketProcessor.director(0));

        // listen host event for dhcp server or the gateway
        requestDhcpPackets();
        modified(context);

        // disable dhcp from host location provider
        compCfgService.preSetProperty(HOST_LOCATION_PROVIDER,
                                      "useDhcp", Boolean.FALSE.toString());
        // Enable distribute route store
        compCfgService.preSetProperty(ROUTE_STORE_IMPL,
                                      "distributed", Boolean.TRUE.toString());
        compCfgService.registerProperties(getClass());

        deviceService.addListener(deviceListener);
        log.info("DHCP-RELAY Started");
    }

    @Deactivate
    protected void deactivate() {
        cfgService.removeListener(cfgListener);
        factories.forEach(cfgService::unregisterConfigFactory);
        packetService.removeProcessor(dhcpRelayPacketProcessor);
        cancelDhcpPackets();
        cancelArpPackets();
        compCfgService.unregisterProperties(getClass(), false);
        deviceService.removeListener(deviceListener);
        log.info("DHCP-RELAY Stopped");
    }

    @Modified
    protected void modified(ComponentContext context) {
        Dictionary<?, ?> properties = context.getProperties();
        Boolean flag;

        flag = Tools.isPropertyEnabled(properties, "arpEnabled");
        if (flag != null) {
            arpEnabled = flag;
            log.info("Address resolution protocol is {}",
                     arpEnabled ? "enabled" : "disabled");
        }

        if (arpEnabled) {
            requestArpPackets();
        } else {
            cancelArpPackets();
        }
    }

    /**
     * Updates DHCP relay app configuration.
     */
    private void updateConfig() {
        DefaultDhcpRelayConfig defaultConfig =
                cfgService.getConfig(appId, DefaultDhcpRelayConfig.class);
        IndirectDhcpRelayConfig indirectConfig =
                cfgService.getConfig(appId, IndirectDhcpRelayConfig.class);
        IgnoreDhcpConfig ignoreDhcpConfig =
                cfgService.getConfig(appId, IgnoreDhcpConfig.class);

        if (defaultConfig != null) {
            updateConfig(defaultConfig);
        }
        if (indirectConfig != null) {
            updateConfig(indirectConfig);
        }
        if (ignoreDhcpConfig != null) {
            updateConfig(ignoreDhcpConfig);
        }
    }

    /**
     * Updates DHCP relay app configuration with given configuration.
     *
     * @param config the configuration ot update
     */
    protected void updateConfig(Config config) {
        if (config instanceof IndirectDhcpRelayConfig) {
            IndirectDhcpRelayConfig indirectConfig = (IndirectDhcpRelayConfig) config;
            v4Handler.setIndirectDhcpServerConfigs(indirectConfig.dhcpServerConfigs());
            v6Handler.setIndirectDhcpServerConfigs(indirectConfig.dhcpServerConfigs());
        } else if (config instanceof DefaultDhcpRelayConfig) {
            DefaultDhcpRelayConfig defaultConfig = (DefaultDhcpRelayConfig) config;
            v4Handler.setDefaultDhcpServerConfigs(defaultConfig.dhcpServerConfigs());
            v6Handler.setDefaultDhcpServerConfigs(defaultConfig.dhcpServerConfigs());
        }
        if (config instanceof IgnoreDhcpConfig) {
            updateIgnoreVlanRules((IgnoreDhcpConfig) config);
        }
    }

    protected void removeConfig(Config config) {
        if (config instanceof IndirectDhcpRelayConfig) {
            v4Handler.setIndirectDhcpServerConfigs(Collections.emptyList());
            v6Handler.setIndirectDhcpServerConfigs(Collections.emptyList());
        } else if (config instanceof DefaultDhcpRelayConfig) {
            v4Handler.setDefaultDhcpServerConfigs(Collections.emptyList());
            v6Handler.setDefaultDhcpServerConfigs(Collections.emptyList());
        }
        if (config instanceof IgnoreDhcpConfig) {
            ignoredVlans.forEach(((deviceId, vlanId) -> {
                processIgnoreVlanRule(deviceId, vlanId, REMOVE);
            }));
        }
    }

    private void updateIgnoreVlanRules(IgnoreDhcpConfig config) {
        config.ignoredVlans().forEach((deviceId, vlanId) -> {
            if (ignoredVlans.get(deviceId).contains(vlanId)) {
                // don't need to process if it already ignored
                return;
            }
            processIgnoreVlanRule(deviceId, vlanId, ADD);
        });

        ignoredVlans.forEach((deviceId, vlanId) -> {
            if (!config.ignoredVlans().get(deviceId).contains(vlanId)) {
                // not contains in new config, remove it
                processIgnoreVlanRule(deviceId, vlanId, REMOVE);
            }
        });
    }

    /**
     * Process the ignore rules.
     *
     * @param deviceId the device id
     * @param vlanId the vlan to be ignored
     * @param op the operation, ADD to install; REMOVE to uninstall rules
     */
    private void processIgnoreVlanRule(DeviceId deviceId, VlanId vlanId, Objective.Operation op) {
        TrafficTreatment dropTreatment = DefaultTrafficTreatment.emptyTreatment();
        dropTreatment.clearedDeferred();
        AtomicInteger installedCount = new AtomicInteger(DHCP_SELECTORS.size());
        DHCP_SELECTORS.forEach(trafficSelector -> {
            UdpPortCriterion udpDst = (UdpPortCriterion) trafficSelector.getCriterion(Criterion.Type.UDP_DST);
            int udpDstPort = udpDst.udpPort().toInt();
            TrafficSelector selector = DefaultTrafficSelector.builder(trafficSelector)
                    .matchVlanId(vlanId)
                    .build();

            ForwardingObjective.Builder builder = DefaultForwardingObjective.builder()
                    .withFlag(ForwardingObjective.Flag.VERSATILE)
                    .withSelector(selector)
                    .withPriority(IGNORE_CONTROL_PRIORITY)
                    .withTreatment(dropTreatment)
                    .fromApp(appId);


            ObjectiveContext objectiveContext = new ObjectiveContext() {
                @Override
                public void onSuccess(Objective objective) {
                    log.info("Ignore rule {} (Vlan id {}, device {}, UDP dst {})",
                             op, vlanId, deviceId, udpDstPort);
                    int countDown = installedCount.decrementAndGet();
                    if (countDown != 0) {
                        return;
                    }
                    switch (op) {
                        case ADD:

                            ignoredVlans.put(deviceId, vlanId);
                            break;
                        case REMOVE:
                            ignoredVlans.remove(deviceId, vlanId);
                            break;
                        default:
                            log.warn("Unsupported objective operation {}", op);
                            break;
                    }
                }

                @Override
                public void onError(Objective objective, ObjectiveError error) {
                    log.warn("Can't {} ignore rule (vlan id {}, udp dst {}, device {}) due to {}",
                             op, vlanId, udpDstPort, deviceId, error);
                }
            };

            ForwardingObjective fwd;
            switch (op) {
                case ADD:
                    fwd = builder.add(objectiveContext);
                    break;
                case REMOVE:
                    fwd = builder.remove(objectiveContext);
                    break;
                default:
                    log.warn("Unsupported objective operation {}", op);
                    return;
            }

            Device device = deviceService.getDevice(deviceId);
            if (device == null || !device.is(Pipeliner.class)) {
                log.warn("Device {} is not available now, wait until device is available", deviceId);
                return;
            }
            flowObjectiveService.apply(deviceId, fwd);
        });
    }

    /**
     * Request DHCP packet in via PacketService.
     */
    private void requestDhcpPackets() {
        DHCP_SELECTORS.forEach(trafficSelector -> {
            packetService.requestPackets(trafficSelector, PacketPriority.CONTROL, appId);
        });
    }

    /**
     * Cancel requested DHCP packets in via packet service.
     */
    private void cancelDhcpPackets() {
        DHCP_SELECTORS.forEach(trafficSelector -> {
            packetService.cancelPackets(trafficSelector, PacketPriority.CONTROL, appId);
        });
    }

    /**
     * Request ARP packet in via PacketService.
     */
    private void requestArpPackets() {
        packetService.requestPackets(ARP_SELECTOR, PacketPriority.CONTROL, appId);
    }

    /**
     * Cancel requested ARP packets in via packet service.
     */
    private void cancelArpPackets() {
        packetService.cancelPackets(ARP_SELECTOR, PacketPriority.CONTROL, appId);
    }

    @Override
    public Optional<DhcpRecord> getDhcpRecord(HostId hostId) {
        return dhcpRelayStore.getDhcpRecord(hostId);
    }

    @Override
    public Collection<DhcpRecord> getDhcpRecords() {
        return dhcpRelayStore.getDhcpRecords();
    }

    @Override
    public Optional<MacAddress> getDhcpServerMacAddress() {
        // TODO: depreated it
        DefaultDhcpRelayConfig config = cfgService.getConfig(appId, DefaultDhcpRelayConfig.class);
        DhcpServerConfig serverConfig = config.dhcpServerConfigs().get(0);
        Ip4Address serverip = serverConfig.getDhcpServerIp4().get();
        return hostService.getHostsByIp(serverip)
                .stream()
                .map(Host::mac)
                .findFirst();
    }

    /**
     * Gets DHCP data from a packet.
     *
     * @param packet the packet
     * @return the DHCP data; empty if it is not a DHCP packet
     */
    private Optional<DHCP> findDhcp(Ethernet packet) {
        return Stream.of(packet)
                .filter(Objects::nonNull)
                .map(Ethernet::getPayload)
                .filter(p -> p instanceof IPv4)
                .map(IPacket::getPayload)
                .filter(Objects::nonNull)
                .filter(p -> p instanceof UDP)
                .map(IPacket::getPayload)
                .filter(Objects::nonNull)
                .filter(p -> p instanceof DHCP)
                .map(p -> (DHCP) p)
                .findFirst();
    }

    /**
     * Gets DHCPv6 data from a packet.
     *
     * @param packet the packet
     * @return the DHCPv6 data; empty if it is not a DHCPv6 packet
     */
    private Optional<DHCP6> findDhcp6(Ethernet packet) {
        return Stream.of(packet)
                .filter(Objects::nonNull)
                .map(Ethernet::getPayload)
                .filter(p -> p instanceof IPv6)
                .map(IPacket::getPayload)
                .filter(Objects::nonNull)
                .filter(p -> p instanceof UDP)
                .map(IPacket::getPayload)
                .filter(Objects::nonNull)
                .filter(p -> p instanceof DHCP6)
                .map(p -> (DHCP6) p)
                .findFirst();
    }


    private class DhcpRelayPacketProcessor implements PacketProcessor {

        @Override
        public void process(PacketContext context) {
            // process the packet and get the payload
            Ethernet packet = context.inPacket().parsed();
            if (packet == null) {
                return;
            }

            findDhcp(packet).ifPresent(dhcpPayload -> {
                v4Handler.processDhcpPacket(context, dhcpPayload);
            });

            findDhcp6(packet).ifPresent(dhcp6Payload -> {
                v6Handler.processDhcpPacket(context, dhcp6Payload);
            });

            if (packet.getEtherType() == Ethernet.TYPE_ARP && arpEnabled) {
                ARP arpPacket = (ARP) packet.getPayload();
                VlanId vlanId = VlanId.vlanId(packet.getVlanID());
                Set<Interface> interfaces = interfaceService.
                        getInterfacesByPort(context.inPacket().receivedFrom());
                //ignore the packets if dhcp server interface is not configured on onos.
                if (interfaces.isEmpty()) {
                    log.warn("server virtual interface not configured");
                    return;
                }
                if ((arpPacket.getOpCode() != ARP.OP_REQUEST)) {
                    // handle request only
                    return;
                }
                MacAddress interfaceMac = interfaces.stream()
                        .filter(iface -> iface.vlan().equals(vlanId))
                        .map(Interface::mac)
                        .filter(mac -> !mac.equals(MacAddress.NONE))
                        .findFirst()
                        .orElse(MacAddress.ONOS);
                if (interfaceMac == null) {
                    // can't find interface mac address
                    return;
                }
                processArpPacket(context, packet, interfaceMac);
            }
        }

        /**
         * Processes the ARP Payload and initiates a reply to the client.
         *
         * @param context the packet context
         * @param packet the ethernet payload
         * @param replyMac mac address to be replied
         */
        private void processArpPacket(PacketContext context, Ethernet packet, MacAddress replyMac) {
            ARP arpPacket = (ARP) packet.getPayload();
            ARP arpReply = (ARP) arpPacket.clone();
            arpReply.setOpCode(ARP.OP_REPLY);

            arpReply.setTargetProtocolAddress(arpPacket.getSenderProtocolAddress());
            arpReply.setTargetHardwareAddress(arpPacket.getSenderHardwareAddress());
            arpReply.setSenderProtocolAddress(arpPacket.getTargetProtocolAddress());
            arpReply.setSenderHardwareAddress(replyMac.toBytes());

            // Ethernet Frame.
            Ethernet ethReply = new Ethernet();
            ethReply.setSourceMACAddress(replyMac.toBytes());
            ethReply.setDestinationMACAddress(packet.getSourceMAC());
            ethReply.setEtherType(Ethernet.TYPE_ARP);
            ethReply.setVlanID(packet.getVlanID());
            ethReply.setPayload(arpReply);

            ConnectPoint targetPort = context.inPacket().receivedFrom();
            TrafficTreatment t = DefaultTrafficTreatment.builder()
                    .setOutput(targetPort.port()).build();
            OutboundPacket o = new DefaultOutboundPacket(
                    targetPort.deviceId(), t, ByteBuffer.wrap(ethReply.serialize()));
            if (log.isTraceEnabled()) {
                log.trace("Relaying ARP packet {} to {}", packet, targetPort);
            }
            packetService.emit(o);
        }
    }

    /**
     * Listener for network config events.
     */
    private class InternalConfigListener implements NetworkConfigListener {
        @Override
        public void event(NetworkConfigEvent event) {
            switch (event.type()) {
                case CONFIG_UPDATED:
                case CONFIG_ADDED:
                    event.config().ifPresent(config -> {
                        updateConfig(config);
                        log.info("{} updated", config.getClass().getSimpleName());
                    });
                    break;
                case CONFIG_REMOVED:
                    event.prevConfig().ifPresent(config -> {
                        removeConfig(config);
                        log.info("{} removed", config.getClass().getSimpleName());
                    });
                    break;
                default:
                    log.warn("Unsupported event type {}", event.type());
                    break;
            }

        }
    }

    private class InternalDeviceListener implements DeviceListener {

        @Override
        public void event(DeviceEvent event) {
            Device device = event.subject();
            switch (event.type()) {
                case DEVICE_ADDED:
                    deviceAdd(device.id());
                    break;
                case DEVICE_REMOVED:
                    ignoredVlans.removeAll(device.id());
                    break;
                case DEVICE_AVAILABILITY_CHANGED:
                    deviceAvailabilityChanged(device);

                default:
                    break;
            }
        }

        private void deviceAvailabilityChanged(Device device) {
            if (deviceService.isAvailable(device.id())) {
                deviceAdd(device.id());
            } else {
                ignoredVlans.removeAll(device.id());
            }
        }

        private void deviceAdd(DeviceId deviceId) {
            IgnoreDhcpConfig config = cfgService.getConfig(appId, IgnoreDhcpConfig.class);
            Collection<VlanId> vlanIds = config.ignoredVlans().get(deviceId);
            vlanIds.forEach(vlanId -> {
                processIgnoreVlanRule(deviceId, vlanId, ADD);
            });
        }
    }
}