/*
 * Copyright 2016-present 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.opencord.cordvtn.impl.handler;

import com.google.common.collect.ImmutableSet;
import org.onlab.osgi.DefaultServiceDirectory;
import org.onlab.osgi.ServiceDirectory;
import org.onosproject.core.ApplicationId;
import org.onosproject.core.CoreService;
import org.onosproject.mastership.MastershipService;
import org.onosproject.net.Host;
import org.onosproject.net.host.HostEvent;
import org.onosproject.net.host.HostListener;
import org.onosproject.net.host.HostService;
import org.opencord.cordvtn.api.Constants;
import org.opencord.cordvtn.api.CordVtnService;
import org.opencord.cordvtn.api.Instance;
import org.opencord.cordvtn.api.InstanceHandler;
import org.opencord.cordvtn.api.NetworkId;
import org.opencord.cordvtn.api.ServiceNetwork.ServiceNetworkType;
import org.opencord.cordvtn.api.VtnNetwork;
import org.opencord.cordvtn.api.VtnPort;
import org.slf4j.Logger;

import java.util.Objects;
import java.util.Set;
import java.util.concurrent.ExecutorService;
import java.util.stream.Collectors;
import java.util.stream.StreamSupport;

import static java.util.concurrent.Executors.newSingleThreadExecutor;
import static org.onlab.util.Tools.groupedThreads;
import static org.slf4j.LoggerFactory.getLogger;

/**
 * Provides default virtual network connectivity for service instances.
 */
public abstract class AbstractInstanceHandler implements InstanceHandler {

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

    protected static final String ERR_VTN_NETWORK = "Failed to get VTN network for %s";
    protected static final String ERR_VTN_PORT = "Failed to get VTN port for %s";

    protected CoreService coreService;
    protected MastershipService mastershipService;
    protected HostService hostService;
    protected CordVtnService vtnService;
    protected ApplicationId appId;
    protected Set<ServiceNetworkType> netTypes = ImmutableSet.of();

    protected HostListener hostListener = new InternalHostListener();

    protected final ExecutorService eventExecutor = newSingleThreadExecutor(
            groupedThreads(this.getClass().getSimpleName(), "event-handler", log));

    protected void activate() {
        ServiceDirectory services = new DefaultServiceDirectory();
        coreService = services.get(CoreService.class);
        mastershipService = services.get(MastershipService.class);
        hostService = services.get(HostService.class);
        vtnService = services.get(CordVtnService.class);

        appId = coreService.registerApplication(Constants.CORDVTN_APP_ID);
        hostService.addListener(hostListener);

        log.info("Started");
    }

    protected void deactivate() {
        hostService.removeListener(hostListener);
        eventExecutor.shutdown();

        log.info("Stopped");
    }

    @Override
    public void instanceUpdated(Instance instance) {
        instanceDetected(instance);
    }

    protected Set<Instance> getInstances(NetworkId netId) {
        return StreamSupport.stream(hostService.getHosts().spliterator(), false)
                .filter(host -> Objects.equals(
                        netId.id(),
                        host.annotations().value(Instance.NETWORK_ID)))
                .map(Instance::of)
                .collect(Collectors.toSet());
    }

    protected VtnNetwork getVtnNetwork(Instance instance) {
        VtnNetwork vtnNet = vtnService.vtnNetwork(instance.netId());
        if (vtnNet == null) {
            final String error = String.format(ERR_VTN_NETWORK, instance);
            throw new IllegalStateException(error);
        }
        return vtnNet;
    }

    protected VtnPort getVtnPort(Instance instance) {
        VtnPort vtnPort = vtnService.vtnPort(instance.portId());
        if (vtnPort == null) {
            final String error = String.format(ERR_VTN_PORT, instance);
            throw new IllegalStateException(error);
        }
        return vtnPort;
    }

    private class InternalHostListener implements HostListener {

        @Override
        public void event(HostEvent event) {
            Host host = event.subject();
            if (!mastershipService.isLocalMaster(host.location().deviceId())) {
                // do not allow to proceed without mastership
                return;
            }

            Instance instance = Instance.of(host);
            if (!netTypes.isEmpty() && !netTypes.contains(instance.netType())) {
                // not my service network instance, do nothing
                return;
            }

            switch (event.type()) {
                case HOST_UPDATED:
                    eventExecutor.execute(() -> instanceUpdated(instance));
                    break;
                case HOST_ADDED:
                    eventExecutor.execute(() -> instanceDetected(instance));
                    break;
                case HOST_REMOVED:
                    eventExecutor.execute(() -> instanceRemoved(instance));
                    break;
                default:
                    break;
            }
        }
    }
}