package org.onlab.onos.net.device.impl;

import static com.google.common.base.Preconditions.checkNotNull;
import static org.onlab.onos.net.device.DeviceEvent.Type.DEVICE_MASTERSHIP_CHANGED;
import static org.slf4j.LoggerFactory.getLogger;

import java.util.List;

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.onlab.onos.cluster.ClusterService;
import org.onlab.onos.cluster.MastershipEvent;
import org.onlab.onos.cluster.MastershipListener;
import org.onlab.onos.cluster.MastershipService;
import org.onlab.onos.cluster.MastershipTerm;
import org.onlab.onos.event.AbstractListenerRegistry;
import org.onlab.onos.event.EventDeliveryService;
import org.onlab.onos.net.Device;
import org.onlab.onos.net.DeviceId;
import org.onlab.onos.net.MastershipRole;
import org.onlab.onos.net.Port;
import org.onlab.onos.net.PortNumber;
import org.onlab.onos.net.device.DeviceAdminService;
import org.onlab.onos.net.device.DeviceDescription;
import org.onlab.onos.net.device.DeviceEvent;
import org.onlab.onos.net.device.DeviceListener;
import org.onlab.onos.net.device.DeviceProvider;
import org.onlab.onos.net.device.DeviceProviderRegistry;
import org.onlab.onos.net.device.DeviceProviderService;
import org.onlab.onos.net.device.DeviceService;
import org.onlab.onos.net.device.DeviceStore;
import org.onlab.onos.net.device.DeviceStoreDelegate;
import org.onlab.onos.net.device.PortDescription;
import org.onlab.onos.net.provider.AbstractProviderRegistry;
import org.onlab.onos.net.provider.AbstractProviderService;
import org.onlab.onos.store.common.ClockService;
import org.slf4j.Logger;

/**
 * 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 static final String ROLE_NULL = "Role cannot be null";

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

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

    private final DeviceStoreDelegate delegate = new InternalStoreDelegate();

    private final MastershipListener mastershipListener = new InternalMastershipListener();

    @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 ClockService clockService;

    @Activate
    public void activate() {
        store.setDelegate(delegate);
        eventDispatcher.addSink(DeviceEvent.class, listenerRegistry);
        mastershipService.addListener(mastershipListener);
        log.info("Started");
    }

    @Deactivate
    public void deactivate() {
        store.unsetDelegate(delegate);
        mastershipService.removeListener(mastershipListener);
        eventDispatcher.removeSink(DeviceEvent.class);
        log.info("Stopped");
    }

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

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

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

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

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

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

    @Override
    public boolean isAvailable(DeviceId deviceId) {
        checkNotNull(deviceId, DEVICE_ID_NULL);
        return store.isAvailable(deviceId);
    }

    // Applies the specified role to the device; ignores NONE
    private void applyRole(DeviceId deviceId, MastershipRole newRole) {
        if (newRole != MastershipRole.NONE) {
            Device device = store.getDevice(deviceId);
            DeviceProvider provider = getProvider(device.providerId());
            if (provider != null) {
                provider.roleChanged(device, newRole);
            }
            post(new DeviceEvent(DEVICE_MASTERSHIP_CHANGED, device));
        }
    }

    @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) {
        listenerRegistry.addListener(listener);
    }

    @Override
    public void removeListener(DeviceListener listener) {
        listenerRegistry.removeListener(listener);
    }

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

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

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

        @Override
        public void deviceConnected(DeviceId deviceId, DeviceDescription deviceDescription) {
            checkNotNull(deviceId, DEVICE_ID_NULL);
            checkNotNull(deviceDescription, DEVICE_DESCRIPTION_NULL);
            checkValidity();
            DeviceEvent event = store.createOrUpdateDevice(provider().id(),
                    deviceId, deviceDescription);

            // If there was a change of any kind, trigger role selection process.
            if (event != null) {
                log.info("Device {} connected", deviceId);
                mastershipService.requestRoleFor(deviceId);
                provider().roleChanged(event.subject(),
                        mastershipService.getLocalRole(deviceId));
                post(event);
            }
        }

        @Override
        public void deviceDisconnected(DeviceId deviceId) {
            checkNotNull(deviceId, DEVICE_ID_NULL);
            checkValidity();
            DeviceEvent event = store.markOffline(deviceId);
            if (event != null) {
                log.info("Device {} disconnected", deviceId);
                post(event);
            }
        }

        @Override
        public void updatePorts(DeviceId deviceId, List<PortDescription> portDescriptions) {
            checkNotNull(deviceId, DEVICE_ID_NULL);
            checkNotNull(portDescriptions, "Port descriptions list cannot be null");
            checkValidity();
            List<DeviceEvent> events = store.updatePorts(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();
            DeviceEvent event = store.updatePortStatus(deviceId, portDescription);
            if (event != null) {
                log.info("Device {} port {} status changed", deviceId,
                        event.port().number());
                post(event);
            }
        }

        @Override
        public void unableToAssertRole(DeviceId deviceId, MastershipRole role) {
            // FIXME: implement response to this notification
            log.warn("Failed to assert role [{}] onto Device {}",
                    role, deviceId);
        }
    }

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

    // Intercepts mastership events
    private class InternalMastershipListener implements MastershipListener {
        @Override
        public void event(MastershipEvent event) {
            if (event.master().equals(clusterService.getLocalNode().id())) {
                MastershipTerm term = mastershipService.requestTermService().getMastershipTerm(event.subject());
                clockService.setMastershipTerm(event.subject(), term);
                applyRole(event.subject(), MastershipRole.MASTER);
            } else {
                applyRole(event.subject(), MastershipRole.STANDBY);
            }
        }
    }

    // Store delegate to re-post events emitted from the store.
    private class InternalStoreDelegate implements DeviceStoreDelegate {
        @Override
        public void notify(DeviceEvent event) {
            post(event);
        }
    }
}