/*
 * Copyright 2014-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.net.device.impl;

import com.google.common.collect.ImmutableList;
import com.google.common.collect.Lists;
import com.google.common.collect.Maps;
import com.google.common.collect.Multimap;
import com.google.common.util.concurrent.Futures;
import org.onlab.util.KryoNamespace;
import org.onlab.util.Tools;
import org.onosproject.cluster.ClusterService;
import org.onosproject.cluster.ControllerNode;
import org.onosproject.cluster.NodeId;
import org.onosproject.mastership.MastershipAdminService;
import org.onosproject.mastership.MastershipEvent;
import org.onosproject.mastership.MastershipListener;
import org.onosproject.mastership.MastershipService;
import org.onosproject.mastership.MastershipTerm;
import org.onosproject.mastership.MastershipTermService;
import org.onosproject.net.ConnectPoint;
import org.onosproject.net.Device;
import org.onosproject.net.Device.Type;
import org.onosproject.net.DeviceId;
import org.onosproject.net.MastershipRole;
import org.onosproject.net.Port;
import org.onosproject.net.PortNumber;
import org.onosproject.net.config.Config;
import org.onosproject.net.config.NetworkConfigEvent;
import org.onosproject.net.config.NetworkConfigListener;
import org.onosproject.net.config.NetworkConfigService;
import org.onosproject.net.config.PortConfigOperator;
import org.onosproject.net.config.PortConfigOperatorRegistry;
import org.onosproject.net.config.basics.BasicDeviceConfig;
import org.onosproject.net.config.basics.DeviceAnnotationConfig;
import org.onosproject.net.config.basics.PortAnnotationConfig;
import org.onosproject.net.config.basics.PortDescriptionsConfig;
import org.onosproject.net.device.DefaultPortDescription;
import org.onosproject.net.device.DeviceAdminService;
import org.onosproject.net.device.DeviceDescription;
import org.onosproject.net.device.DeviceEvent;
import org.onosproject.net.device.DeviceListener;
import org.onosproject.net.device.DeviceProvider;
import org.onosproject.net.device.DeviceProviderRegistry;
import org.onosproject.net.device.DeviceProviderService;
import org.onosproject.net.device.DeviceService;
import org.onosproject.net.device.DeviceStore;
import org.onosproject.net.device.DeviceStoreDelegate;
import org.onosproject.net.device.PortDescription;
import org.onosproject.net.device.PortStatistics;
import org.onosproject.net.provider.AbstractListenerProviderRegistry;
import org.onosproject.net.provider.AbstractProviderService;
import org.onosproject.net.provider.Provider;
import org.onosproject.net.provider.ProviderId;
import org.onosproject.store.cluster.messaging.ClusterCommunicationService;
import org.onosproject.store.cluster.messaging.MessageSubject;
import org.onosproject.store.serializers.KryoNamespaces;
import org.onosproject.store.service.Serializer;
import org.onosproject.upgrade.UpgradeService;
import org.osgi.service.component.annotations.Activate;
import org.osgi.service.component.annotations.Component;
import org.osgi.service.component.annotations.Deactivate;
import org.osgi.service.component.annotations.Reference;
import org.osgi.service.component.annotations.ReferenceCardinality;
import org.slf4j.Logger;

import java.time.Instant;
import java.util.Collection;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Objects;
import java.util.Optional;
import java.util.Set;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.stream.Collectors;

import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.base.Preconditions.checkState;
import static com.google.common.collect.Multimaps.newListMultimap;
import static com.google.common.collect.Multimaps.synchronizedListMultimap;
import static java.util.concurrent.Executors.newSingleThreadExecutor;
import static java.util.concurrent.Executors.newSingleThreadScheduledExecutor;
import static java.lang.System.currentTimeMillis;
import static org.onlab.util.Tools.groupedThreads;
import static org.onosproject.net.MastershipRole.MASTER;
import static org.onosproject.net.MastershipRole.NONE;
import static org.onosproject.net.MastershipRole.STANDBY;
import static org.onosproject.security.AppGuard.checkPermission;
import static org.onosproject.security.AppPermission.Type.DEVICE_READ;
import static org.slf4j.LoggerFactory.getLogger;

/**
 * Provides implementation of the device SB &amp; NB APIs.
 */
@Component(immediate = true,
           service = {DeviceService.class, DeviceAdminService.class,
                      DeviceProviderRegistry.class, PortConfigOperatorRegistry.class })
public class DeviceManager
        extends AbstractListenerProviderRegistry<DeviceEvent, DeviceListener, DeviceProvider, DeviceProviderService>
        implements DeviceService, DeviceAdminService, DeviceProviderRegistry, PortConfigOperatorRegistry {

    private static final String DEVICE_ID_NULL = "Device ID cannot be null";
    private static final String PORT_NUMBER_NULL = "Port number cannot be null";
    private static final String DEVICE_DESCRIPTION_NULL = "Device description cannot be null";
    private static final String PORT_DESCRIPTION_NULL = "Port description cannot be null";
    private static final String PORT_DESC_LIST_NULL = "Port description list cannot be null";
    private static final String EVENT_NON_MASTER = "Non-master node cannot handle this event";

    private final Logger log = getLogger(getClass());

    private final DeviceStoreDelegate delegate = new InternalStoreDelegate();

    private final MastershipListener mastershipListener = new InternalMastershipListener();
    private NodeId localNodeId;

    private ScheduledExecutorService backgroundService;

    private final NetworkConfigListener networkConfigListener = new InternalNetworkConfigListener();

    @Reference(cardinality = ReferenceCardinality.MANDATORY)
    protected DeviceStore store;

    @Reference(cardinality = ReferenceCardinality.MANDATORY)
    protected ClusterService clusterService;

    @Reference(cardinality = ReferenceCardinality.MANDATORY)
    protected MastershipService mastershipService;

    @Reference(cardinality = ReferenceCardinality.MANDATORY)
    protected MastershipAdminService mastershipAdminService;

    @Reference(cardinality = ReferenceCardinality.MANDATORY)
    protected MastershipTermService termService;

    @Reference(cardinality = ReferenceCardinality.MANDATORY)
    protected UpgradeService upgradeService;

    @Reference(cardinality = ReferenceCardinality.MANDATORY)
    protected NetworkConfigService networkConfigService;

    @Reference(cardinality = ReferenceCardinality.MANDATORY)
    protected ClusterCommunicationService communicationService;

    private ExecutorService clusterRequestExecutor;
    /**
     * List of all registered PortConfigOperator.
     */
    private final List<PortConfigOperator> portOps = new CopyOnWriteArrayList<>();

    /**
     * Index to look up PortConfigOperator from Config each PortConfigOperator uses.
     */
    private final Multimap<Class<? extends Config<ConnectPoint>>, PortConfigOperator> portOpsIndex
            = synchronizedListMultimap(
            newListMultimap(new ConcurrentHashMap<>(), CopyOnWriteArrayList::new));

    // not part of portOps. must be executed at the end
    private PortAnnotationOperator portAnnotationOp;
    private DeviceAnnotationOperator deviceAnnotationOp;

    private static final MessageSubject PORT_UPDOWN_SUBJECT =
            new MessageSubject("port-updown-req");

    private static final MessageSubject PROBE_SUBJECT =
            new MessageSubject("probe-req");
    private static final long PROBE_TIMEOUT_MILLIS = 5000;
    private static final int PROBE_ATTEMPTS = 3;

    private static final Serializer SERIALIZER = Serializer.using(
            KryoNamespace.newBuilder()
                    .register(KryoNamespaces.API)
                    .register(InternalPortUpDownEvent.class)
                    .nextId(KryoNamespaces.BEGIN_USER_CUSTOM_ID)
                    .build("DeviceManager"));

    /**
     * Local storage for connectivity status of devices.
     */
    private class LocalStatus {
        boolean connected;
        Instant dateTime;

        public LocalStatus(boolean b, Instant now) {
            connected = b;
            dateTime = now;
        }
    }

    private final Map<DeviceId, LocalStatus> deviceLocalStatus =
            Maps.newConcurrentMap();

    // To remember whether or not the role was acknowledged by the device
    private final Map<DeviceId, Long> roleToAcknowledge =
            Maps.newConcurrentMap();
    private ScheduledExecutorService backgroundRoleChecker;
    private static final int ROLE_TIMEOUT_SECONDS = 10;

    @Activate
    public void activate() {
        portAnnotationOp = new PortAnnotationOperator(networkConfigService);
        deviceAnnotationOp = new DeviceAnnotationOperator(networkConfigService);
        portOpsIndex.put(PortAnnotationConfig.class, portAnnotationOp);

        backgroundService = newSingleThreadScheduledExecutor(
                groupedThreads("onos/device", "manager-background", log));
        localNodeId = clusterService.getLocalNode().id();

        store.setDelegate(delegate);
        eventDispatcher.addSink(DeviceEvent.class, listenerRegistry);
        mastershipService.addListener(mastershipListener);
        networkConfigService.addListener(networkConfigListener);

        backgroundService.scheduleWithFixedDelay(() -> {
            try {
                mastershipCheck();
            } catch (Exception e) {
                log.error("Exception thrown during mastership integrity check", e);
            }
        }, 1, 1, TimeUnit.MINUTES);

        clusterRequestExecutor = newSingleThreadExecutor();

        communicationService.addSubscriber(
                PORT_UPDOWN_SUBJECT,
                SERIALIZER::decode,
                this::handlePortRequest,
                clusterRequestExecutor);

        communicationService.addSubscriber(
                PROBE_SUBJECT,
                SERIALIZER::decode,
                this::handleProbeRequest,
                SERIALIZER::encode,
                clusterRequestExecutor);

        backgroundRoleChecker = newSingleThreadScheduledExecutor(
                groupedThreads("onos/device", "manager-role", log));
        backgroundRoleChecker.scheduleAtFixedRate(() -> {
            try {
                roleCheck();
            } catch (Exception e) {
                log.error("Exception thrown while verifying role acknowledgement from all devices", e);
            }
        }, 0, 10, TimeUnit.SECONDS);

        log.info("Started");
    }

    @Deactivate
    public void deactivate() {
        backgroundService.shutdown();
        networkConfigService.removeListener(networkConfigListener);
        store.unsetDelegate(delegate);
        mastershipService.removeListener(mastershipListener);
        eventDispatcher.removeSink(DeviceEvent.class);
        communicationService.removeSubscriber(PORT_UPDOWN_SUBJECT);
        clusterRequestExecutor.shutdown();
        backgroundRoleChecker.shutdown();
        log.info("Stopped");
    }

    @Override
    public int getDeviceCount() {
        checkPermission(DEVICE_READ);
        return store.getDeviceCount();
    }

    @Override
    public int getAvailableDeviceCount() {
        checkPermission(DEVICE_READ);
        return store.getAvailableDeviceCount();
    }

    @Override
    public Iterable<Device> getDevices() {
        checkPermission(DEVICE_READ);
        return store.getDevices();
    }

    @Override
    public Iterable<Device> getAvailableDevices() {
        checkPermission(DEVICE_READ);
        return store.getAvailableDevices();
    }

    @Override
    public Device getDevice(DeviceId deviceId) {
        checkPermission(DEVICE_READ);
        checkNotNull(deviceId, DEVICE_ID_NULL);
        return store.getDevice(deviceId);
    }

    @Override
    public MastershipRole getRole(DeviceId deviceId) {
        checkPermission(DEVICE_READ);
        checkNotNull(deviceId, DEVICE_ID_NULL);
        return mastershipService.getLocalRole(deviceId);
    }

    @Override
    public List<Port> getPorts(DeviceId deviceId) {
        checkPermission(DEVICE_READ);
        checkNotNull(deviceId, DEVICE_ID_NULL);
        return store.getPorts(deviceId);
    }

    @Override
    public List<PortStatistics> getPortStatistics(DeviceId deviceId) {
        checkPermission(DEVICE_READ);
        checkNotNull(deviceId, DEVICE_ID_NULL);
        return store.getPortStatistics(deviceId);
    }

    @Override
    public List<PortStatistics> getPortDeltaStatistics(DeviceId deviceId) {
        checkPermission(DEVICE_READ);
        checkNotNull(deviceId, DEVICE_ID_NULL);
        return store.getPortDeltaStatistics(deviceId);
    }

    @Override
    public PortStatistics getStatisticsForPort(DeviceId deviceId, PortNumber portNumber) {
        checkPermission(DEVICE_READ);
        checkNotNull(deviceId, DEVICE_ID_NULL);
        checkNotNull(portNumber, PORT_NUMBER_NULL);
        return store.getStatisticsForPort(deviceId, portNumber);
    }

    @Override
    public PortStatistics getDeltaStatisticsForPort(DeviceId deviceId, PortNumber portNumber) {
        checkPermission(DEVICE_READ);
        checkNotNull(deviceId, DEVICE_ID_NULL);
        checkNotNull(portNumber, PORT_NUMBER_NULL);
        return store.getDeltaStatisticsForPort(deviceId, portNumber);
    }

    @Override
    public Port getPort(DeviceId deviceId, PortNumber portNumber) {
        checkPermission(DEVICE_READ);
        checkNotNull(deviceId, DEVICE_ID_NULL);
        checkNotNull(portNumber, PORT_NUMBER_NULL);
        return store.getPort(deviceId, portNumber);
    }

    @Override
    public boolean isAvailable(DeviceId deviceId) {
        checkPermission(DEVICE_READ);

        checkNotNull(deviceId, DEVICE_ID_NULL);
        return store.isAvailable(deviceId);
    }

    @Override
    public String localStatus(DeviceId deviceId) {
        LocalStatus ls = deviceLocalStatus.get(deviceId);
        if (ls == null) {
            return "No Record";
        }
        String timeAgo = Tools.timeAgo(ls.dateTime.toEpochMilli());
        return (ls.connected) ? "connected " + timeAgo : "disconnected " + timeAgo;
    }

    private boolean isLocallyConnected(DeviceId deviceId) {
        LocalStatus ls = deviceLocalStatus.get(deviceId);
        if (ls == null) {
            return false;
        }
        return ls.connected;
    }

    @Override
    public long getLastUpdatedInstant(DeviceId deviceId) {
        LocalStatus ls = deviceLocalStatus.get(deviceId);
        if (ls == null) {
            return 0;
        }
        return ls.dateTime.toEpochMilli();
    }

    // Check a device for control channel connectivity
    // and changes local-status appropriately.
    private boolean isReachable(DeviceId deviceId) {
        if (deviceId == null) {
            return false;
        }
        DeviceProvider provider = getProvider(deviceId);
        if (provider != null) {
            boolean reachable = probeReachability(deviceId);
            if (reachable && !isLocallyConnected(deviceId)) {
                deviceLocalStatus.put(deviceId, new LocalStatus(true, Instant.now()));
            } else if (!reachable && isLocallyConnected(deviceId)) {
                deviceLocalStatus.put(deviceId, new LocalStatus(false, Instant.now()));
            }
            return reachable;
        } else {
            log.debug("Provider not found for {}", deviceId);
            return false;
        }
    }

    @Override
    public void removeDevice(DeviceId deviceId) {
        checkNotNull(deviceId, DEVICE_ID_NULL);
        DeviceEvent event = store.removeDevice(deviceId);
        if (event != null) {
            log.info("Device {} administratively removed", deviceId);
        }
    }

    @Override
    public void removeDevicePorts(DeviceId deviceId) {
        checkNotNull(deviceId, DEVICE_ID_NULL);
        if (isAvailable(deviceId)) {
            log.debug("Cannot remove ports of device {} while it is available.", deviceId);
            return;
        }

        List<PortDescription> portDescriptions = ImmutableList.of();
        List<DeviceEvent> events = store.updatePorts(getProvider(deviceId).id(),
                                                     deviceId, portDescriptions);
        if (events != null) {
            for (DeviceEvent event : events) {
                post(event);
            }
        }
    }

    private void handlePortRequest(InternalPortUpDownEvent event) {
        DeviceId deviceId = event.deviceId();
        checkNotNull(deviceId, DEVICE_ID_NULL);
        checkNotNull(event.portNumber(), PORT_NUMBER_NULL);
        checkState(mastershipService.isLocalMaster(deviceId), EVENT_NON_MASTER);
        changePortStateAtMaster(event.deviceId(), event.portNumber(), event.isEnable());
    }

    private void changePortStateAtMaster(DeviceId deviceId, PortNumber portNumber,
                                       boolean enable) {
        DeviceProvider provider = getProvider(deviceId);
        if (provider != null) {
            log.info("Port {} on device {} being administratively brought {}",
                     portNumber, deviceId,
                     (enable) ? "UP" : "DOWN");
            provider.changePortState(deviceId, portNumber, enable);
        } else {
            log.warn("Provider not found for {}", deviceId);
        }
    }

    @Override
    public void changePortState(DeviceId deviceId, PortNumber portNumber,
                                boolean enable) {
        checkNotNull(deviceId, DEVICE_ID_NULL);
        checkNotNull(portNumber, PORT_NUMBER_NULL);
        NodeId masterId = mastershipService.getMasterFor(deviceId);

        if (masterId == null) {
            // No master found; device is offline
            log.info("No master found for port state change for {}", deviceId);
            return;
        }

        if (!masterId.equals(localNodeId)) {
            //Send the request to the master node for the device
            log.info("Device {} is managed by {}, forwarding the request to the MASTER",
                     deviceId, masterId);
            communicationService.unicast(
                    new InternalPortUpDownEvent(deviceId, portNumber, enable),
                    PORT_UPDOWN_SUBJECT,
                    SERIALIZER::encode,
                    masterId).whenComplete((r, error) -> {
                if (error != null) {
                    log.warn("Failed to send packet-updown-req to {}", masterId, error);
                }
            });
        } else {
            changePortStateAtMaster(deviceId, portNumber, enable);
        }
    }

    @Override
    protected DeviceProviderService createProviderService(
            DeviceProvider provider) {
        return new InternalDeviceProviderService(provider);
    }

    /**
     * Checks if all the reachable devices have a valid mastership role.
     */
    private void mastershipCheck() {
        log.debug("Checking mastership");
        for (Device device : getDevices()) {
            final DeviceId deviceId = device.id();
            MastershipRole myRole = mastershipService.getLocalRole(deviceId);
            log.trace("Checking device {}. Current role is {}", deviceId, myRole);
            if (!isReachable(deviceId)) {
                if (myRole != NONE) {
                    // Verify if the device is fully disconnected from the cluster
                    if (updateMastershipFor(deviceId) == null
                            && myRole == MASTER && isAvailable(deviceId)) {
                        log.info("Local Role {}, Marking unreachable device {} offline", MASTER, deviceId);
                        post(store.markOffline(deviceId));
                    }
                } else {
                    /* Firstly get a role and then check if the device is available in the store.
                       if it is, if this node is the master and the device is fully disconnected
                       from the cluster mark the device offline. In principle, this condition should
                       never be hit unless in a device removed phase for NONE mastership roles. */
                    try {
                        mastershipService.requestRoleFor(deviceId).get();
                    } catch (InterruptedException e) {
                        Thread.currentThread().interrupt();
                        log.error("Interrupted waiting for Mastership", e);
                    } catch (ExecutionException e) {
                        log.error("Encountered an error waiting for Mastership", e);
                    }

                    MastershipTerm term = termService.getMastershipTerm(deviceId);
                    if (updateMastershipFor(deviceId) == null &&
                            term != null && localNodeId.equals(term.master()) &&
                            isAvailable(deviceId)) {
                        log.info("Marking unreachable device {} offline", deviceId);
                        post(store.markOffline(deviceId));
                    }
                }
                roleToAcknowledge.remove(deviceId);
                continue;
            }

            // If this node is the master, ensure the device is marked online.
            if (myRole == MASTER && canMarkOnline(device)) {
                post(store.markOnline(deviceId));
            }

            log.info("{} is reachable - reasserting the role", deviceId);

            /* Device is still reachable. It is useful for some protocols
               to reassert the role. Note: NONE triggers request to MastershipService */
            reassertRole(deviceId, myRole);
        }
    }

    /**
     * Checks if all the devices have acknowledged the mastership role.
     */
    private void roleCheck() {
        log.debug("Checking role");
        for (Device device : getDevices()) {
            final DeviceId deviceId = device.id();
            MastershipRole myRole = mastershipService.getLocalRole(deviceId);
            log.trace("Checking device {}. Current role is {}", deviceId, myRole);
            final AtomicBoolean exists = new AtomicBoolean(false);
            final Long ts = roleToAcknowledge.compute(deviceId, (key, value) -> {
                if (value == null) {
                    return null;
                }
                exists.set(true);
                if (currentTimeMillis() - value < (ROLE_TIMEOUT_SECONDS * 1000)) {
                    return value;
                }
                return null;
            });
            // Nobody applied the role recently
            if (!exists.get()) {
                log.trace("Role was not applied or it has been acknowledged for device {}", deviceId);
                continue;
            }
            // Timeout still on
            if (ts != null) {
                log.debug("Timeout expires in {} ms", ((ROLE_TIMEOUT_SECONDS * 1000) - currentTimeMillis() + ts));
                continue;
            }
            if (myRole != MASTER) {
                log.debug("Timeout is expired but current role is not MASTER ({}), nothing to do", myRole);
                continue;
            }
            /* Switch failed to acknowledge master role we asked for.
               Yield mastership to other instance*/
            log.warn("Failed to assert role onto device {}. requested={}, no response",
                    deviceId, myRole);
            updateMastershipFor(deviceId);
        }
    }

    // Personalized device provider service issued to the supplied provider.
    private class InternalDeviceProviderService
            extends AbstractProviderService<DeviceProvider>
            implements DeviceProviderService {

        InternalDeviceProviderService(DeviceProvider provider) {
            super(provider);
        }

        /**
         * Apply role in reaction to provider event.
         *
         * @param deviceId device identifier
         * @param newRole  new role to apply to the device
         * @return true if the request was sent to provider
         */
        private boolean applyRole(DeviceId deviceId, MastershipRole newRole) {

            if (newRole.equals(MastershipRole.NONE)) {
                //no-op
                return true;
            }

            DeviceProvider provider = provider();
            if (provider == null) {
                log.warn("Provider for {} was not found. Cannot apply role {}",
                         deviceId, newRole);
                return false;
            }
            // Start the timer
            roleToAcknowledge.put(deviceId, currentTimeMillis());
            provider.roleChanged(deviceId, newRole);
            // not triggering probe when triggered by provider service event
            return true;
        }

        @Override
        public void deviceConnected(DeviceId deviceId,
                                    DeviceDescription deviceDescription) {
            checkNotNull(deviceId, DEVICE_ID_NULL);
            checkNotNull(deviceDescription, DEVICE_DESCRIPTION_NULL);
            checkValidity();

            deviceLocalStatus.put(deviceId, new LocalStatus(true, Instant.now()));

            BasicDeviceConfig cfg = networkConfigService.getConfig(deviceId, BasicDeviceConfig.class);
            if (!isAllowed(cfg)) {
                log.warn("Device {} is not allowed", deviceId);
                return;
            }
            PortDescriptionsConfig portConfig = networkConfigService.getConfig(deviceId, PortDescriptionsConfig.class);
            // Generate updated description and establish my Role
            deviceDescription = BasicDeviceOperator.combine(cfg, deviceDescription);
            DeviceAnnotationConfig annoConfig = networkConfigService.getConfig(deviceId, DeviceAnnotationConfig.class);
            if (annoConfig != null) {
                deviceDescription = deviceAnnotationOp.combine(deviceId, deviceDescription, Optional.of(annoConfig));
            }

            // Wait for the end of the election. sync call of requestRoleFor
            // wait only 3s and it is not entirely safe since the leadership
            // election timer can be higher.
            MastershipRole role = Futures.getUnchecked(mastershipService.requestRoleFor(deviceId));
            log.info("Local role is {} for {}", role, deviceId);
            store.createOrUpdateDevice(provider().id(), deviceId, deviceDescription);
            applyRole(deviceId, role);

            if (portConfig != null) {
                //updating the ports if configration exists
                List<PortDescription> complete = store.getPortDescriptions(provider().id(), deviceId)
                        .collect(Collectors.toList());
                complete.addAll(portConfig.portDescriptions());
                List<PortDescription> portDescriptions = complete.stream()
                        .map(e -> applyAllPortOps(deviceId, e))
                        .collect(Collectors.toList());
                store.updatePorts(provider().id(), deviceId, portDescriptions);
            }

            if (deviceDescription.isDefaultAvailable()) {
                log.info("Device {} connected", deviceId);
            } else {
                log.info("Device {} registered", deviceId);
            }
        }

        private PortDescription ensurePortEnabledState(PortDescription desc, boolean enabled) {
            if (desc.isEnabled() != enabled) {
                return DefaultPortDescription.builder(desc)
                        .isEnabled(enabled)
                        .build();
            }
            return desc;
        }

        @Override
        public void deviceDisconnected(DeviceId deviceId) {
            checkNotNull(deviceId, DEVICE_ID_NULL);
            checkValidity();
            // Update the local status
            deviceLocalStatus.put(deviceId, new LocalStatus(false, Instant.now()));
            log.info("Device {} disconnected from this node: {}", deviceId,
                     clusterService.getLocalNode().id());

            /* If none can reach the device, we will continue with the disconnection logic.
               If there is one instance that reported device is still reachable, we hand over
               the mastership to it if we are the current master, otherwise if we are a backup
               we demote ourselves to the bottom of the backups list */
            if (updateMastershipFor(deviceId) == null) {
                log.info("Device {} is fully disconnected from the cluster", deviceId);
                List<PortDescription> descs = store.getPortDescriptions(provider().id(), deviceId)
                        .map(desc -> ensurePortEnabledState(desc, false))
                        .collect(Collectors.toList());
                store.updatePorts(this.provider().id(), deviceId, descs);

                try {
                    if (mastershipService.isLocalMaster(deviceId)) {
                        post(store.markOffline(deviceId));
                    }
                } catch (IllegalStateException e) {
                    log.warn("Failed to mark {} offline", deviceId);
                    // only the MASTER should be marking off-line in normal cases,
                    // but if I was the last STANDBY connection, etc. and no one else
                    // was there to mark the device offline, this instance may need to
                    // temporarily request for Master Role and mark offline.

                    //there are times when this node will correctly have mastership, BUT
                    //that isn't reflected in the ClockManager before the device disconnects.
                    //we want to let go of the device anyways, so make sure this happens.

                    // FIXME: Store semantics leaking out as IllegalStateException.
                    //  Consider revising store API to handle this scenario.
                    CompletableFuture<MastershipRole> roleFuture = mastershipService.requestRoleFor(deviceId);
                    roleFuture.whenComplete((role, error) -> {
                        MastershipTerm term = termService.getMastershipTerm(deviceId);
                        // TODO: Move this type of check inside device clock manager, etc.
                        if (term != null && localNodeId.equals(term.master())) {
                            log.info("Retry marking {} offline", deviceId);
                            post(store.markOffline(deviceId));
                        } else {
                            log.info("Failed again marking {} offline. {}", deviceId, role);
                        }
                    });
                } finally {
                    roleToAcknowledge.remove(deviceId);
                }
            }

        }

        @Override
        public void updatePorts(DeviceId deviceId,
                                List<PortDescription> portDescriptions) {
            checkNotNull(deviceId, DEVICE_ID_NULL);
            checkNotNull(portDescriptions, PORT_DESC_LIST_NULL);
            checkValidity();
            if (!mastershipService.isLocalMaster(deviceId)) {
                // Never been a master for this device
                // any update will be ignored.
                log.trace("Ignoring {} port updates on standby node. {}", deviceId, portDescriptions);
                return;
            }
            PortDescriptionsConfig portConfig = networkConfigService.getConfig(deviceId, PortDescriptionsConfig.class);
            if (portConfig != null) {
                // Updating the ports if configuration exists (on new lists as
                // the passed one might be immutable)
                portDescriptions = Lists.newArrayList(portDescriptions);
                portDescriptions.addAll(portConfig.portDescriptions());
            }
            portDescriptions = portDescriptions.stream()
                    .map(e -> applyAllPortOps(deviceId, e))
                    .collect(Collectors.toList());
            List<DeviceEvent> events = store.updatePorts(this.provider().id(),
                                                         deviceId, portDescriptions);
            if (events != null) {
                for (DeviceEvent event : events) {
                    post(event);
                }
            }
        }

        @Override
        public void portStatusChanged(DeviceId deviceId,
                                      PortDescription portDescription) {
            checkNotNull(deviceId, DEVICE_ID_NULL);
            checkNotNull(portDescription, PORT_DESCRIPTION_NULL);
            checkValidity();

            if (!mastershipService.isLocalMaster(deviceId)) {
                // Never been a master for this device
                // any update will be ignored.
                log.trace("Ignoring {} port update on standby node. {}", deviceId,
                          portDescription);
                return;
            }
            Device device = getDevice(deviceId);
            if (device == null) {
                log.trace("Device not found: {}", deviceId);
                return;
            }
            if ((Type.ROADM.equals(device.type())) || (Type.OTN.equals(device.type())) ||
                    (Type.OLS.equals(device.type())) || (Type.TERMINAL_DEVICE.equals(device.type()))) {
                // FIXME This is ignoring all other info in portDescription given as input??
                PortDescription storedPortDesc = store.getPortDescription(provider().id(),
                                                                          deviceId,
                                                                          portDescription.portNumber());
                portDescription = ensurePortEnabledState(storedPortDesc,
                                                         portDescription.isEnabled());
            }

            portDescription = applyAllPortOps(deviceId, portDescription);
            final DeviceEvent event = store.updatePortStatus(this.provider().id(),
                                                             deviceId,
                                                             portDescription);
            if (event != null) {
                log.info("Device {} port {} status changed (enabled={})",
                         deviceId, event.port().number(), portDescription.isEnabled());
                post(event);
            }
        }

        @Override
        public void deletePort(DeviceId deviceId, PortDescription basePortDescription) {

            checkNotNull(deviceId, DEVICE_ID_NULL);
            checkNotNull(basePortDescription, PORT_DESCRIPTION_NULL);
            checkValidity();

            if (!mastershipService.isLocalMaster(deviceId)) {
                // Never been a master for this device
                // any update will be ignored.
                log.trace("Ignoring {} port update on standby node. {}", deviceId,
                          basePortDescription);
                return;
            }

            Device device = getDevice(deviceId);
            if (device == null) {
                log.trace("Device not found: {}", deviceId);
            }

            PortDescription newPortDescription = DefaultPortDescription.builder(basePortDescription)
                .isRemoved(true)
                .build();

            final DeviceEvent event = store.updatePortStatus(this.provider().id(),
                                                             deviceId,
                                                             newPortDescription);
            if (event != null) {
                log.info("Device {} port {} status changed", deviceId, event.port().number());
                post(event);
            }
        }

        @Override
        public void receivedRoleReply(DeviceId deviceId, MastershipRole requested,
                                      MastershipRole response) {
            // Several things can happen here:
            // 1. request and response match
            // 2. request and response don't match
            // 3. MastershipRole and requested match (and 1 or 2 are true)
            // 4. MastershipRole and requested don't match (and 1 or 2 are true)
            //
            // 2, 4, and 3 with case 2 are failure modes.

            // FIXME: implement response to this notification

            log.debug("got reply to a role request for {}: asked for {}, and got {}",
                      deviceId, requested, response);

            if (requested == null && response == null) {
                // something was off with DeviceProvider, maybe check channel too?
                log.warn("Failed to assert role onto Device {}", deviceId);
                roleToAcknowledge.remove(deviceId);
                updateMastershipFor(deviceId);
                return;
            }

            final MastershipRole expected = mastershipService.getLocalRole(deviceId);

            if (requested == null) {
                // Provider is not able to reconcile role responses with
                // requests. We assume what was requested is what we expect.
                // This will work only if mastership doesn't change too often,
                // and devices are left enough time to provide responses before
                // a different role is requested.
                requested = expected;
            }

            if (Objects.equals(requested, response)) {
                if (Objects.equals(requested, expected)) {
                    // Stop the timer
                    log.info("Role has been acknowledged for device {}", deviceId);
                    roleToAcknowledge.remove(deviceId);
                } else {
                    log.warn("Role mismatch on {}. Set to {}, but store demands {}",
                             deviceId, response, expected);
                    // roleManager got the device to comply, but doesn't agree with
                    // the store; use the store's view, then try to reassert.
                    backgroundService.execute(() -> reassertRole(deviceId, expected));
                }
            } else {
                // we didn't get back what we asked for. Reelect someone else.
                log.warn("Failed to assert role onto device {}. requested={}, response={}",
                         deviceId, requested, response);
                if (requested == MastershipRole.MASTER) {
                    // Stop the timer
                    roleToAcknowledge.remove(deviceId);
                    updateMastershipFor(deviceId);
                } else if (requested ==  MastershipRole.STANDBY) {
                    // For P4RT devices, the response role will be NONE when this node is expected to be STANDBY
                    // but the stream channel is not opened correctly.
                    // Calling reassertRole will trigger the mechanism in GeneralDeviceProvider that
                    // attempts to re-establish the stream channel
                    backgroundService.execute(() -> reassertRole(deviceId, expected));
                }
            }
        }

        @Override
        public void updatePortStatistics(DeviceId deviceId, Collection<PortStatistics> portStatistics) {
            checkNotNull(deviceId, DEVICE_ID_NULL);
            checkNotNull(portStatistics, "Port statistics list cannot be null");
            checkValidity();

            DeviceEvent event = store.updatePortStatistics(this.provider().id(),
                                                           deviceId, portStatistics);
            post(event);
        }

        @Override
        public DeviceDescription getDeviceDescription(DeviceId deviceId) {
            checkNotNull(deviceId, DEVICE_ID_NULL);
            checkValidity();

            return store.getDeviceDescription(provider().id(), deviceId);
        }
    }

    // by default allowed, otherwise check flag
    private boolean isAllowed(BasicDeviceConfig cfg) {
        return (cfg == null || cfg.isAllowed());
    }

    private boolean canMarkOnline(Device device) {
        DeviceProvider provider = getProvider(device.id());
        if (provider == null) {
            log.warn("Provider for {} was not found. Cannot evaluate availability", device.id());
            return false;
        }
        return provider.isAvailable(device.id());
    }

    // Applies the specified role to the device; ignores NONE

    /**
     * Apply role to device and send probe if MASTER.
     *
     * @param deviceId device identifier
     * @param newRole  new role to apply to the device
     * @return true if the request was sent to provider
     */
    private boolean applyRoleAndProbe(DeviceId deviceId, MastershipRole newRole) {
        if (newRole.equals(MastershipRole.NONE)) {
            //no-op
            return true;
        }

        DeviceProvider provider = getProvider(deviceId);
        if (provider == null) {
            log.warn("Provider for {} was not found. Cannot apply role {}", deviceId, newRole);
            return false;
        }
        // Start the timer
        roleToAcknowledge.put(deviceId, currentTimeMillis());
        provider.roleChanged(deviceId, newRole);

        if (newRole.equals(MastershipRole.MASTER)) {
            log.debug("sent TriggerProbe({})", deviceId);
            // only trigger event when request was sent to provider
            provider.triggerProbe(deviceId);
        }
        return true;
    }

    private boolean probeReachability(DeviceId deviceId) {
        DeviceProvider provider = getProvider(deviceId);
        if (provider == null) {
            log.warn("Provider for {} was not found. Cannot probe reachability", deviceId);
            return false;
        }
        return provider.isReachable(deviceId) && Tools.futureGetOrElse(provider.probeReachability(deviceId),
                PROBE_TIMEOUT_MILLIS, TimeUnit.MILLISECONDS, Boolean.FALSE);
    }

    /**
     * Reassert role for specified device connected to this node.
     *
     * @param did      device identifier
     * @param nextRole role to apply. If NONE is specified,
     *                 it will ask mastership service for a role and apply it.
     */
    private void reassertRole(final DeviceId did,
                              final MastershipRole nextRole) {

        MastershipRole myNextRole = nextRole;
        if (myNextRole == NONE && upgradeService.isLocalActive()) {
            try {
                mastershipService.requestRoleFor(did).get();
                MastershipTerm term = termService.getMastershipTerm(did);
                if (term != null && localNodeId.equals(term.master())) {
                    myNextRole = MASTER;
                } else {
                    myNextRole = STANDBY;
                }
            } catch (InterruptedException e) {
                Thread.currentThread().interrupt();
                log.error("Interrupted waiting for Mastership", e);
            } catch (ExecutionException e) {
                log.error("Encountered an error waiting for Mastership", e);
            }
        }

        switch (myNextRole) {
            case MASTER:
                final Device device = getDevice(did);
                if (device != null && !isAvailable(did) && canMarkOnline(device)) {
                    post(store.markOnline(did));
                }
                // TODO: should apply role only if there is mismatch
                log.debug("Applying role {} to {}", myNextRole, did);
                if (!applyRoleAndProbe(did, MASTER)) {
                    log.warn("Unsuccessful applying role {} to {}", myNextRole, did);
                    // immediately failed to apply role
                    updateMastershipFor(did);
                    // FIXME disconnect?
                }
                break;
            case STANDBY:
                log.debug("Applying role {} to {}", myNextRole, did);
                if (!applyRoleAndProbe(did, STANDBY)) {
                    log.warn("Unsuccessful applying role {} to {}", myNextRole, did);
                    // immediately failed to apply role
                    updateMastershipFor(did);
                    // FIXME disconnect?
                }
                break;
            case NONE:
                break;
            default:
                // should never reach here
                log.error("You didn't see anything. I did not exist.");
                break;
        }
    }

    private void handleMastershipEvent(MastershipEvent event) {
        final DeviceId did = event.subject();

        // myNextRole suggested by MastershipService event
        MastershipRole myNextRole;
        if (event.type() == MastershipEvent.Type.SUSPENDED) {
            myNextRole = NONE; // FIXME STANDBY OR NONE?
        } else if (localNodeId.equals(event.roleInfo().master())) {
            // confirm latest info
            MastershipTerm term = termService.getMastershipTerm(did);
            final boolean iHaveControl = term != null && localNodeId.equals(term.master());
            if (iHaveControl) {
                myNextRole = MASTER;
            } else {
                myNextRole = STANDBY;
            }
        } else if (event.roleInfo().backups().contains(localNodeId)) {
            myNextRole = STANDBY;
        } else {
            myNextRole = NONE;
        }

        final boolean isReachable = isReachable(did);
        if (!isReachable) {
            // device is not connected to this node, nevertheless we should get a role
            if (mastershipService.getLocalRole(did) == NONE) {
                log.debug("Node was instructed to be {} role for {}, "
                                  + "but this node cannot reach the device "
                                  + "and role is already None. Asking a new role "
                                  + "and then apply the disconnection protocol.",
                          myNextRole, did);
                try {
                    mastershipService.requestRoleFor(did).get();
                } catch (InterruptedException e) {
                    Thread.currentThread().interrupt();
                    log.error("Interrupted waiting for Mastership", e);
                } catch (ExecutionException e) {
                    log.error("Encountered an error waiting for Mastership", e);
                }
            } else if (myNextRole != NONE) {
                log.warn("Node was instructed to be {} role for {}, "
                                 + "but this node cannot reach the device. "
                                 + "Apply the disconnection protocol.",
                         myNextRole, did);
            }
            // Let's put some order in the candidates list
            roleToAcknowledge.remove(did);
            updateMastershipFor(did);
            return;
        }

        /* Device is connected to this node - always reassert the role.
           Ideally, protocols like OpenFlow would not need to reassert the
           role because the instances are only identified by the role. However,
           other protocols like P4RT require to provide also an election id
           which maybe different over time, by reasserting the role will guarantee
           that updated election ids are communicated to the devices. It should not
           cost us a lot as it is equivalent to a probe.*/
        if (store.getDevice(did) != null) {
            reassertRole(did, myNextRole);
        } else {
            log.debug("Device is not yet/no longer in the store: {}", did);
        }
    }

    // Intercepts mastership events
    private class InternalMastershipListener implements MastershipListener {

        @Override
        public void event(MastershipEvent event) {
            backgroundService.execute(() -> {
                try {
                    handleMastershipEvent(event);
                } catch (Exception e) {
                    log.warn("Failed to handle {}", event, e);
                }
            });
        }
    }

    // Store delegate to re-post events emitted from the store.
    private class InternalStoreDelegate implements DeviceStoreDelegate {
        @Override
        public void notify(DeviceEvent event) {
            post(event);
            if (event.type().equals(DeviceEvent.Type.DEVICE_REMOVED)) {
                // When device is administratively removed, force disconnect.
                DeviceId deviceId = event.subject().id();
                deviceLocalStatus.remove(deviceId);

                DeviceProvider provider = getProvider(deviceId);
                if (provider != null) {
                    log.info("Triggering disconnect for device {}", deviceId);
                    try {
                        provider.triggerDisconnect(deviceId);
                    } catch (UnsupportedOperationException e) {
                        log.warn("Unable to trigger disconnect due to {}", e.getMessage());
                    }
                }
            }
        }
    }

    @Override
    public Iterable<Device> getDevices(Type type) {
        checkPermission(DEVICE_READ);
        Set<Device> results = new HashSet<>();
        Iterable<Device> devices = store.getDevices();
        if (devices != null) {
            devices.forEach(d -> {
                if (type.equals(d.type())) {
                    results.add(d);
                }
            });
        }
        return results;
    }

    @Override
    public Iterable<Device> getAvailableDevices(Type type) {
        checkPermission(DEVICE_READ);
        Set<Device> results = new HashSet<>();
        Iterable<Device> availableDevices = store.getAvailableDevices();
        if (availableDevices != null) {
            availableDevices.forEach(d -> {
                if (type.equals(d.type())) {
                    results.add(d);
                }
            });
        }
        return results;
    }

    private class InternalNetworkConfigListener implements NetworkConfigListener {
        private DeviceId extractDeviceId(NetworkConfigEvent event) {
            DeviceId deviceId = null;
            if (event.configClass().equals(PortAnnotationConfig.class)) {
                if (event.subject().getClass() == ConnectPoint.class) {
                    deviceId = ((ConnectPoint) event.subject()).deviceId();
                }
            } else if (event.subject().getClass() == DeviceId.class) {
                deviceId = (DeviceId) event.subject();
            }
            return deviceId;
        }

        @Override
        public boolean isRelevant(NetworkConfigEvent event) {
            DeviceId deviceId = extractDeviceId(event);

            return (event.type() == NetworkConfigEvent.Type.CONFIG_ADDED
                    || event.type() == NetworkConfigEvent.Type.CONFIG_UPDATED
                    || event.type() == NetworkConfigEvent.Type.CONFIG_REMOVED)
                    && (event.configClass().equals(BasicDeviceConfig.class)
                    || portOpsIndex.containsKey(event.configClass())
                    || event.configClass().equals(PortDescriptionsConfig.class)
                    || event.configClass().equals(DeviceAnnotationConfig.class))
                    && deviceId != null && mastershipService.isLocalMaster(deviceId);
        }

        @Override
        public void event(NetworkConfigEvent event) {
            DeviceEvent de = null;
            if (event.configClass().equals(BasicDeviceConfig.class)) {
                log.debug("Detected device network config event {}", event.type());
                DeviceId did = (DeviceId) event.subject();
                DeviceProvider dp = getProvider(did);
                BasicDeviceConfig cfg =
                        networkConfigService.getConfig(did, BasicDeviceConfig.class);

                if (!isAllowed(cfg)) {
                    kickOutBadDevice(did);
                } else {
                    Device dev = getDevice(did);
                    DeviceDescription desc =
                            (dev == null) ? null : BasicDeviceOperator.descriptionOf(dev);
                    desc = BasicDeviceOperator.combine(cfg, desc);
                    if (desc != null && dp != null) {
                        store.createOrUpdateDevice(dp.id(), did, desc);
                    }
                }
            } else if (event.configClass().equals(PortDescriptionsConfig.class)) {
                DeviceId did = (DeviceId) event.subject();
                DeviceProvider dp = getProvider(did);
                if (!event.config().isPresent() ||
                    getDevice(did) == null || dp == null) {
                    // sanity check failed, ignore
                    return;
                }
                PortDescriptionsConfig portConfig = (PortDescriptionsConfig) event.config().get();
                    //updating the ports if configuration exists
                    List<PortDescription> complete = store.getPortDescriptions(dp.id(), did)
                            .collect(Collectors.toList());
                    complete.addAll(portConfig.portDescriptions());
                    store.updatePorts(dp.id(), did, complete);
            } else if (event.configClass().equals(DeviceAnnotationConfig.class)) {
                DeviceId did = (DeviceId) event.subject();
                DeviceProvider dp = getProvider(did);
                Device dev = getDevice(did);
                DeviceDescription desc =
                        (dev == null) ? null : BasicDeviceOperator.descriptionOf(dev);
                Optional<Config> prevConfig = event.prevConfig();
                if (desc != null) { // Fix for NPE due to desc being null
                    desc = deviceAnnotationOp.combine(did, desc, prevConfig);
                }
                if (desc != null && dp != null) {
                    store.createOrUpdateDevice(dp.id(), did, desc);
                }
            } else if (portOpsIndex.containsKey(event.configClass())) {
                ConnectPoint cpt = (ConnectPoint) event.subject();
                DeviceId did = cpt.deviceId();
                DeviceProvider dp = getProvider(did);

                // Note: assuming PortOperator can modify existing port,
                //       but cannot add new port purely from Config.
                de = Optional.ofNullable(dp)
                        .map(provider -> store.getPortDescription(provider.id(), did, cpt.port()))
                        .map(desc -> applyAllPortOps(cpt, desc, event.prevConfig()))
                        .map(desc -> store.updatePortStatus(dp.id(), did, desc))
                        .orElse(null);
            }

            if (de != null) {
                post(de);
            }
        }

        // removes the specified device if it exists
        private void kickOutBadDevice(DeviceId deviceId) {
            Device badDevice = getDevice(deviceId);
            if (badDevice != null) {
                removeDevice(deviceId);
            }
        }
    }

    @Override
    @SafeVarargs
    public final void registerPortConfigOperator(PortConfigOperator portOp,
                                                 Class<? extends Config<ConnectPoint>>... configs) {
        checkNotNull(portOp);

        portOp.bindService(networkConfigService);

        // update both portOpsIndex and portOps
        synchronized (portOpsIndex) {
            for (Class<? extends Config<ConnectPoint>> config : configs) {
                portOpsIndex.put(config, portOp);
            }

            portOps.add(portOp);
        }

        // TODO: Should we be applying to all existing Ports?
        Tools.stream(store.getAvailableDevices())
                .map(Device::id)
                .filter(mastershipService::isLocalMaster)
                // for each locally managed Device, update all port descriptions
                .map(did -> {
                    ProviderId pid = Optional.ofNullable(getProvider(did))
                            .map(Provider::id)
                            .orElse(null);
                    if (pid == null) {
                        log.warn("Provider not found for {}", did);
                        return ImmutableList.<DeviceEvent>of();
                    }
                    List<PortDescription> pds
                            = store.getPortDescriptions(pid, did)
                            .map(pdesc -> applyAllPortOps(did, pdesc))
                            .collect(Collectors.toList());
                    return store.updatePorts(pid, did, pds);
                })
                // ..and port port update event if necessary
                .forEach(evts -> evts.forEach(this::post));
    }

    @Override
    public void unregisterPortConfigOperator(PortConfigOperator portOp) {
        checkNotNull(portOp);


        // remove all portOp
        synchronized (portOpsIndex) {
            portOps.remove(portOp);

            // had to do this since COWArrayList iterator doesn't support remove
            portOpsIndex.keySet().forEach(key -> portOpsIndex.remove(key, portOp));
        }

    }

    /**
     * Merges the appropriate PortConfig with the description.
     *
     * @param did  ID of the Device where the port is attached
     * @param desc {@link PortDescription}
     * @return merged {@link PortDescription}
     */
    private PortDescription applyAllPortOps(DeviceId did, PortDescription desc) {
        return applyAllPortOps(new ConnectPoint(did, desc.portNumber()), desc);
    }

    /**
     * Merges the appropriate PortConfig with the description.
     *
     * @param cpt  ConnectPoint where the port is attached
     * @param desc {@link PortDescription}
     * @return merged {@link PortDescription}
     */
    private PortDescription applyAllPortOps(ConnectPoint cpt, PortDescription desc) {
        PortDescription work = desc;
        for (PortConfigOperator portOp : portOps) {
            work = portOp.combine(cpt, work);
        }
        return portAnnotationOp.combine(cpt, work);
    }

    /**
     * Merges the appropriate PortConfig with the description.
     *
     * @param cpt  ConnectPoint where the port is attached
     * @param desc {@link PortDescription}
     * @param prevConfig previous configuration
     * @return merged {@link PortDescription}
     */
    private PortDescription applyAllPortOps(ConnectPoint cpt, PortDescription desc,
                                            Optional<Config> prevConfig) {
        PortDescription work = desc;
        for (PortConfigOperator portOp : portOps) {
            work = portOp.combine(cpt, work, prevConfig);
        }
        return portAnnotationOp.combine(cpt, work, prevConfig);
    }

    /**
     * Handler for remote probe requests.
     *
     * @param deviceId the device to check
     * @return whether or not the device is reachable
     */
    private boolean handleProbeRequest(DeviceId deviceId) {
        int attempt = 0;
        // Let's do a number of attempts
        while (attempt < PROBE_ATTEMPTS) {
            if (!probeReachability(deviceId)) {
                return false;
            }
            attempt++;
        }
        return true;
    }

    /**
     * Update the mastership for this device. If there is a node able
     * to reach the device and this node is the master move the
     * mastership to the next node still connected to this device.
     * If the current node is a backup, it demotes itself to the bottom
     * of the candidates list
     *
     * @param deviceId the device for which we have to update the mastership
     * @return the NodeId of any node that can reach the device, or null if
     * none of the ONOS instances can reach the device
     */
    private NodeId updateMastershipFor(DeviceId deviceId) {
        Map<NodeId, CompletableFuture<Boolean>> probes = Maps.newHashMap();
        // Request a probe only if the node is ready
        for (ControllerNode onosNode : clusterService.getNodes()) {
            if (!clusterService.getState(onosNode.id()).isReady() || localNodeId.equals(onosNode.id())) {
                continue;
            }
            probes.put(onosNode.id(), communicationService.sendAndReceive(deviceId, PROBE_SUBJECT, SERIALIZER::encode,
                    SERIALIZER::decode, onosNode.id()));
        }

        // Returns the first node able to reach the device
        // FIXME [SDFAB-935] optimize by looking at the MastershipInfo
        boolean isReachable;
        NodeId nextMaster = null;
        // FIXME Should we expose timeout? Understand if there is need to signal to the caller
        for (Map.Entry<NodeId, CompletableFuture<Boolean>> probe : probes.entrySet()) {
            isReachable = Tools.futureGetOrElse(probe.getValue(), PROBE_TIMEOUT_MILLIS,
                    TimeUnit.MILLISECONDS, Boolean.FALSE);
            if (isReachable) {
                nextMaster = probe.getKey();
            }
        }

        // FIXME [SDFAB-935] optimize demote by looking at the MastershipInfo;
        if (nextMaster != null) {
            log.info("Device {} is still connected to {}", deviceId, nextMaster);
            MastershipRole myRole = mastershipService.getLocalRole(deviceId);
            if (myRole == MASTER) {
                log.info("Handing over the mastership of {} to next master {}", deviceId, nextMaster);
                mastershipAdminService.setRole(nextMaster, deviceId, MASTER);
                /* Do not demote here because setRole can return before the mastership has been passed.
                   Current implementation promotes first the nextMaster as top of candidate list and then
                   transfer the leadership. We can use the BACKUP events to do demote or leverage periodic
                   checks.*/
            } else if (myRole == STANDBY) {
                log.info("Demote current instance to the bottom of the candidates list for {}", deviceId);
                mastershipAdminService.demote(localNodeId, deviceId);
            } else {
                log.debug("No valid role for {}", deviceId);
            }
        }

        return nextMaster;
    }


    /**
     * Port Enable/Disable message sent to the device's MASTER node.
     */
    private class InternalPortUpDownEvent {
        private final DeviceId deviceId;
        private final PortNumber portNumber;
        private final boolean enable;

        protected InternalPortUpDownEvent(
                DeviceId deviceId, PortNumber portNumber, boolean enable) {
            this.deviceId = deviceId;
            this.portNumber = portNumber;
            this.enable = enable;
        }

        public DeviceId deviceId() {
            return deviceId;
        }
        public PortNumber portNumber() {
            return portNumber;
        }
        public boolean isEnable() {
            return enable;
        }

        protected InternalPortUpDownEvent() {
            this.deviceId = null;
            this.portNumber = null;
            this.enable = false;
        }
    }
}