/*
 * Copyright 2014-2015 Open Networking Laboratory
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.onosproject.net.device.impl;

import static com.google.common.base.Preconditions.checkNotNull;
import static java.util.concurrent.Executors.newSingleThreadScheduledExecutor;
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.slf4j.LoggerFactory.getLogger;

import java.util.Collection;
import java.util.HashSet;
import java.util.List;
import java.util.Objects;
import java.util.Set;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;

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.Reference;
import org.apache.felix.scr.annotations.ReferenceCardinality;
import org.apache.felix.scr.annotations.Service;
import org.onosproject.cluster.ClusterService;
import org.onosproject.cluster.NodeId;
import org.onosproject.core.Permission;
import org.onosproject.event.EventDeliveryService;
import org.onosproject.event.ListenerRegistry;
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.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.device.DefaultDeviceDescription;
import org.onosproject.net.device.DefaultPortDescription;
import org.onosproject.net.device.DeviceAdminService;
import org.onosproject.net.device.DeviceClockProviderService;
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.AbstractProviderRegistry;
import org.onosproject.net.provider.AbstractProviderService;
import org.slf4j.Logger;

import com.google.common.collect.Lists;

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

    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 final Logger log = getLogger(getClass());

    protected final ListenerRegistry<DeviceEvent, DeviceListener> listenerRegistry = new ListenerRegistry<>();

    private final DeviceStoreDelegate delegate = new InternalStoreDelegate();

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

    private ScheduledExecutorService backgroundService;

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

    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
    protected EventDeliveryService eventDispatcher;

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

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

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

    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
    protected DeviceClockProviderService deviceClockProviderService;

    @Activate
    public void activate() {
        backgroundService = newSingleThreadScheduledExecutor(groupedThreads("onos/device",
                                                                            "manager-background"));
        localNodeId = clusterService.getLocalNode().id();

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

        backgroundService.scheduleWithFixedDelay(new Runnable() {

            @Override
            public void run() {
                try {
                    mastershipCheck();
                } catch (Exception e) {
                    log.error("Exception thrown during integrity check", e);
                }
            }
        }, 1, 1, TimeUnit.MINUTES);
        log.info("Started");
    }

    @Deactivate
    public void deactivate() {
        backgroundService.shutdown();

        store.unsetDelegate(delegate);
        mastershipService.removeListener(mastershipListener);
        eventDispatcher.removeSink(DeviceEvent.class);
        log.info("Stopped");
    }

    @Override
    public int getDeviceCount() {
        checkPermission(Permission.DEVICE_READ);

        return store.getDeviceCount();
    }

    @Override
    public Iterable<Device> getDevices() {
        checkPermission(Permission.DEVICE_READ);

        return store.getDevices();
    }

    @Override
    public Iterable<Device> getAvailableDevices() {
        checkPermission(Permission.DEVICE_READ);

        return store.getAvailableDevices();
    }

    @Override
    public Device getDevice(DeviceId deviceId) {
        checkPermission(Permission.DEVICE_READ);

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

    @Override
    public MastershipRole getRole(DeviceId deviceId) {
        checkPermission(Permission.DEVICE_READ);

        checkNotNull(deviceId, DEVICE_ID_NULL);
        return mastershipService.getLocalRole(deviceId);
    }

    @Override
    public List<Port> getPorts(DeviceId deviceId) {
        checkPermission(Permission.DEVICE_READ);

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

    @Override
    public List<PortStatistics> getPortStatistics(DeviceId deviceId) {
        checkPermission(Permission.DEVICE_READ);

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

    @Override
    public Port getPort(DeviceId deviceId, PortNumber portNumber) {
        checkPermission(Permission.DEVICE_READ);

        checkNotNull(deviceId, DEVICE_ID_NULL);
        checkNotNull(portNumber, PORT_NUMBER_NULL);
        return store.getPort(deviceId, portNumber);
    }

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

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

    // Check a device for control channel connectivity.
    private boolean isReachable(DeviceId deviceId) {
        if (deviceId == null) {
            return false;
        }
        DeviceProvider provider = getProvider(deviceId);
        if (provider != null) {
            return provider.isReachable(deviceId);
        } 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);
            post(event);
        }
    }

    @Override
    public void addListener(DeviceListener listener) {
        checkPermission(Permission.DEVICE_EVENT);

        listenerRegistry.addListener(listener);
    }

    @Override
    public void removeListener(DeviceListener listener) {
        checkPermission(Permission.DEVICE_EVENT);

        listenerRegistry.removeListener(listener);
    }

    @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();
            log.trace("Checking device {}", deviceId);

            if (!isReachable(deviceId)) {
                continue;
            }

            if (mastershipService.getLocalRole(deviceId) != NONE) {
                continue;
            }

            log.info("{} is reachable but did not have a valid role, reasserting",
                     deviceId);

            // isReachable but was not MASTER or STANDBY, get a role and apply
            // Note: NONE triggers request to MastershipService
            reassertRole(deviceId, NONE);
        }
    }

    // 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;
            }
            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();

            log.info("Device {} connected", deviceId);
            // check my Role
            CompletableFuture<MastershipRole> role = mastershipService
                    .requestRoleFor(deviceId);
            try {
                // Device subsystem must wait for role assignment
                // to avoid losing Device information.
                // (This node could be the only Node connected to the Device.)
                role.get();
            } catch (InterruptedException e) {
                log.warn("Interrupted while waiting role-assignment for {}",
                         deviceId);
                Thread.currentThread().interrupt();
            } catch (ExecutionException e) {
                log.error("Exception thrown while waiting role-assignment for {}",
                          deviceId, e);
            }

            final MastershipTerm term = termService.getMastershipTerm(deviceId);
            if (term == null || !localNodeId.equals(term.master())) {
                log.info("Role of this node is STANDBY for {}", deviceId);
                applyRole(deviceId, MastershipRole.STANDBY);
            } else {
                log.info("Role of this node is MASTER for {}", deviceId);
                // tell clock provider if this instance is the master
                deviceClockProviderService.setMastershipTerm(deviceId, term);
                applyRole(deviceId, MastershipRole.MASTER);
            }

            DeviceEvent event = store.createOrUpdateDevice(provider().id(),
                                                           deviceId,
                                                           deviceDescription);

            if (event != null) {
                log.trace("event: {} {}", event.type(), event);
                post(event);
            }
        }

        @Override
        public void deviceDisconnected(DeviceId deviceId) {
            checkNotNull(deviceId, DEVICE_ID_NULL);
            checkValidity();

            log.info("Device {} disconnected from this node", deviceId);

            List<Port> ports = store.getPorts(deviceId);
            List<PortDescription> descs = Lists.newArrayList();
            ports.forEach(port -> descs.add(new DefaultPortDescription(port
                    .number(), false, port.type(), port.portSpeed())));
            store.updatePorts(this.provider().id(), deviceId, descs);
            try {
                if (mastershipService.getLocalRole(deviceId) == MASTER) {
                    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);
                            deviceClockProviderService
                                    .setMastershipTerm(deviceId, term);
                            post(store.markOffline(deviceId));
                        } else {
                            log.info("Failed again marking {} offline. {}",
                                     deviceId, role);
                        }
                    });
            } finally {
                try {
                    // relinquish master role and ability to be backup.
                    mastershipService.relinquishMastership(deviceId).get();
                } catch (InterruptedException e) {
                    log.warn("Interrupted while reliquishing role for {}",
                             deviceId);
                    Thread.currentThread().interrupt();
                } catch (ExecutionException e) {
                    log.error("Exception thrown while relinquishing role for {}",
                              deviceId, e);
                }
            }
        }

        @Override
        public void updatePorts(DeviceId deviceId,
                                List<PortDescription> portDescriptions) {
            checkNotNull(deviceId, DEVICE_ID_NULL);
            checkNotNull(portDescriptions,
                         "Port descriptions list cannot be null");
            checkValidity();
            if (!deviceClockProviderService.isTimestampAvailable(deviceId)) {
                // Never been a master for this device
                // any update will be ignored.
                log.trace("Ignoring {} port updates on standby node. {}",
                          deviceId, portDescriptions);
                return;
            }

            List<DeviceEvent> events = store.updatePorts(this.provider().id(),
                                                         deviceId,
                                                         portDescriptions);
            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 (!deviceClockProviderService.isTimestampAvailable(deviceId)) {
                // Never been a master for this device
                // any update will be ignored.
                log.trace("Ignoring {} port update on standby node. {}",
                          deviceId, portDescription);
                return;
            }

            final DeviceEvent event = store.updatePortStatus(this.provider()
                    .id(), deviceId, portDescription);
            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 {}",
                         requested, deviceId);
                mastershipService.relinquishMastership(deviceId);
                return;
            }

            if (Objects.equals(requested, response)) {
                if (Objects.equals(requested,
                                   mastershipService.getLocalRole(deviceId))) {
                    return;
                } else {
                    return;
                    // FIXME roleManager got the device to comply, but doesn't
                    // agree with
                    // the store; use the store's view, then try to reassert.
                }
            } else {
                // we didn't get back what we asked for. Reelect someone else.
                log.warn("Failed to assert role [{}] onto Device {}", response,
                         deviceId);
                if (response == MastershipRole.MASTER) {
                    mastershipService.relinquishMastership(deviceId);
                    // TODO: Shouldn't we be triggering event?
                    // final Device device = getDevice(deviceId);
                    // post(new DeviceEvent(DEVICE_MASTERSHIP_CHANGED, device));
                }
            }
        }

        @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);
        }
    }

    // Posts the specified event to the local event dispatcher.
    private void post(DeviceEvent event) {
        if (event != null && eventDispatcher != null) {
            eventDispatcher.post(event);
        }
    }

    // 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;
        }
        provider.roleChanged(deviceId, newRole);

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

    /**
     * Reaasert 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) {
            mastershipService.requestRoleFor(did);
            MastershipTerm term = termService.getMastershipTerm(did);
            if (term != null && localNodeId.equals(term.master())) {
                myNextRole = MASTER;
            } else {
                myNextRole = STANDBY;
            }
        }

        switch (myNextRole) {
        case MASTER:
            final Device device = getDevice(did);
            if ((device != null) && !isAvailable(did)) {
                // flag the device as online. Is there a better way to do this?
                DefaultDeviceDescription deviceDescription = new DefaultDeviceDescription(
                                                                                          did.uri(),
                                                                                          device.type(),
                                                                                          device.manufacturer(),
                                                                                          device.hwVersion(),
                                                                                          device.swVersion(),
                                                                                          device.serialNumber(),
                                                                                          device.chassisId());
                DeviceEvent devEvent = store.createOrUpdateDevice(device
                        .providerId(), did, deviceDescription);
                post(devEvent);
            }
            // 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
                mastershipService.relinquishMastership(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
                mastershipService.relinquishMastership(did);
                // FIXME disconnect?
            }
            break;
        case NONE:
        default:
            // should never reach here
            log.error("You didn't see anything. I did not exist.");
            break;
        }
    }

    private void handleMastershipEvent(MastershipEvent event) {
        if (event.type() != MastershipEvent.Type.MASTER_CHANGED) {
            // Don't care if backup list changed.
            return;
        }

        final DeviceId did = event.subject();

        // myRole suggested by MastershipService
        MastershipRole myNextRole;
        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) {
                deviceClockProviderService.setMastershipTerm(did, term);
                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
            if (myNextRole != NONE) {
                log.warn("Node was instructed to be {} role for {}, "
                        + "but this node cannot reach the device.  "
                        + "Relinquishing role.  ", myNextRole, did);
                mastershipService.relinquishMastership(did);
            }
            return;
        }

        // device is connected to this node:
        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.submit(() -> {
                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);
        }
    }

    @Override
    public Iterable<Device> getDevices(Type type) {
        checkPermission(Permission.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(Permission.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;
    }
}