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

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.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.PortDescription;
import org.onlab.onos.net.provider.AbstractProviderRegistry;
import org.onlab.onos.net.provider.AbstractProviderService;
import org.slf4j.Logger;

import java.util.List;
import java.util.concurrent.ExecutorService;

import static com.google.common.base.Preconditions.checkNotNull;
import static java.util.concurrent.Executors.newSingleThreadExecutor;
import static org.onlab.util.Tools.namedThreads;
import static org.slf4j.LoggerFactory.getLogger;

/**
 * Provides basic implementation of the device SB &amp; NB APIs.
 */
@Component(immediate = true)
@Service
public class SimpleDeviceManager
        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());

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

    private final SimpleDeviceStore store = new SimpleDeviceStore();

    private final ExecutorService executor =
            newSingleThreadExecutor(namedThreads("onos-device-%d"));

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

    @Activate
    public void activate() {
        eventDispatcher.addSink(DeviceEvent.class, listenerRegistry);
        log.info("Started");
    }

    @Deactivate
    public void deactivate() {
        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 store.getRole(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);
    }

    @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);
    }

    @Override
    public void setRole(DeviceId deviceId, MastershipRole newRole) {
        checkNotNull(deviceId, DEVICE_ID_NULL);
        checkNotNull(newRole, ROLE_NULL);
        DeviceEvent event = store.setRole(deviceId, newRole);
        if (event != null) {
            Device device = event.subject();
            DeviceProvider provider = getProvider(device.providerId());
            if (provider != null) {
                provider.roleChanged(device, newRole);
            }
            post(event);
        }
    }

    @Override
    public void removeDevice(DeviceId deviceId) {
        checkNotNull(deviceId, DEVICE_ID_NULL);
        DeviceEvent event = store.removeDevice(deviceId);
        post(event);
    }

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

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

        @Override
        public void deviceConnected(DeviceId deviceId, DeviceDescription deviceDescription) {
            checkNotNull(deviceId, DEVICE_ID_NULL);
            checkNotNull(deviceDescription, DEVICE_DESCRIPTION_NULL);
            checkValidity();
            log.info("Device {} connected", deviceId);
            DeviceEvent event = store.createOrUpdateDevice(provider().id(),
                                                           deviceId, deviceDescription);
            post(event);

            // If there was a change of any kind, trigger role selection process.
            if (event != null) {
                triggerRoleSelection(event.subject(), provider());
            }
        }

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

    /**
     * Triggers asynchronous role selection.
     *
     * @param device   device
     * @param provider device provider
     */
    private void triggerRoleSelection(final Device device,
                                      final DeviceProvider provider) {
        executor.execute(new Runnable() {
            @Override
            public void run() {
                provider.roleChanged(device, store.getRole(device.id()));
            }
        });
    }

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

}