/*
 * Copyright 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.store.host.impl;

import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.base.Preconditions.checkState;
import static org.onosproject.net.DefaultAnnotations.merge;
import static org.onosproject.net.host.HostEvent.Type.HOST_ADDED;
import static org.onosproject.net.host.HostEvent.Type.HOST_REMOVED;
import static org.onosproject.net.host.HostEvent.Type.HOST_MOVED;
import static org.onosproject.net.host.HostEvent.Type.HOST_UPDATED;
import static org.onosproject.store.service.EventuallyConsistentMapEvent.Type.PUT;
import static org.onosproject.store.service.EventuallyConsistentMapEvent.Type.REMOVE;
import static org.slf4j.LoggerFactory.getLogger;

import java.util.Collection;
import java.util.HashSet;
import java.util.Objects;
import java.util.Set;
import java.util.concurrent.atomic.AtomicReference;
import java.util.function.Predicate;
import java.util.stream.Collectors;

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.packet.IpAddress;
import org.onlab.packet.MacAddress;
import org.onlab.packet.VlanId;
import org.onlab.util.KryoNamespace;
import org.onosproject.net.Annotations;
import org.onosproject.net.ConnectPoint;
import org.onosproject.net.DefaultAnnotations;
import org.onosproject.net.DefaultHost;
import org.onosproject.net.DeviceId;
import org.onosproject.net.Host;
import org.onosproject.net.HostId;
import org.onosproject.net.HostLocation;
import org.onosproject.net.host.HostDescription;
import org.onosproject.net.host.HostEvent;
import org.onosproject.net.host.HostStore;
import org.onosproject.net.host.HostStoreDelegate;
import org.onosproject.net.host.HostEvent.Type;
import org.onosproject.net.provider.ProviderId;
import org.onosproject.store.AbstractStore;
import org.onosproject.store.serializers.KryoNamespaces;
import org.onosproject.store.service.EventuallyConsistentMap;
import org.onosproject.store.service.EventuallyConsistentMapEvent;
import org.onosproject.store.service.EventuallyConsistentMapListener;
import org.onosproject.store.service.LogicalClockService;
import org.onosproject.store.service.StorageService;
import org.slf4j.Logger;

import com.google.common.collect.HashMultimap;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.Multimaps;
import com.google.common.collect.SetMultimap;
import com.google.common.collect.Sets;

/**
 * Manages the inventory of hosts using a {@code EventuallyConsistentMap}.
 */
@Component(immediate = true)
@Service
public class ECHostStore
    extends AbstractStore<HostEvent, HostStoreDelegate>
    implements HostStore {

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

    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
    protected StorageService storageService;

    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
    protected LogicalClockService clockService;

    // Hosts tracked by their location
    private final SetMultimap<ConnectPoint, Host> locations =
            Multimaps.synchronizedSetMultimap(
                    HashMultimap.<ConnectPoint, Host>create());

    private EventuallyConsistentMap<HostId, DefaultHost> hosts;

    private EventuallyConsistentMapListener<HostId, DefaultHost> hostLocationTracker =
            new HostLocationTracker();

    @Activate
    public void activate() {
        KryoNamespace.Builder hostSerializer = KryoNamespace.newBuilder()
                .register(KryoNamespaces.API);

        hosts = storageService.<HostId, DefaultHost>eventuallyConsistentMapBuilder()
                .withName("onos-hosts")
                .withSerializer(hostSerializer)
                .withTimestampProvider((k, v) -> clockService.getTimestamp())
                .build();

        hosts.addListener(hostLocationTracker);

        log.info("Started");
    }

    @Deactivate
    public void deactivate() {
        hosts.removeListener(hostLocationTracker);
        hosts.destroy();
        locations.clear();

        log.info("Stopped");
    }

    @Override
    public HostEvent createOrUpdateHost(ProviderId providerId,
                                        HostId hostId,
                                        HostDescription hostDescription,
                                        boolean replaceIPs) {
        // TODO: We need a way to detect conflicting changes and abort update.
        //       (BOC) Compute might do this for us.

        final AtomicReference<Type> eventType = new AtomicReference<>();
        final AtomicReference<DefaultHost> oldHost = new AtomicReference<>();
        DefaultHost host = hosts.compute(hostId, (id, existingHost) -> {
            if (existingHost != null) {
                oldHost.set(existingHost);
                checkState(Objects.equals(hostDescription.hwAddress(), existingHost.mac()),
                           "Existing and new MAC addresses differ.");
                checkState(Objects.equals(hostDescription.vlan(), existingHost.vlan()),
                           "Existing and new VLANs differ.");
            }

            // TODO do we ever want the existing location?
            HostLocation location = hostDescription.location();

            final Set<IpAddress> addresses;
            if (existingHost == null || replaceIPs) {
                addresses = ImmutableSet.copyOf(hostDescription.ipAddress());
            } else {
                addresses = Sets.newHashSet(existingHost.ipAddresses());
                addresses.addAll(hostDescription.ipAddress());
            }

            final Annotations annotations;
            if (existingHost != null) {
                annotations = merge((DefaultAnnotations) existingHost.annotations(),
                                    hostDescription.annotations());
            } else {
                annotations = hostDescription.annotations();
            }

            if (existingHost == null) {
                eventType.set(HOST_ADDED);
            } else if (!Objects.equals(existingHost.location(), hostDescription.location())) {
                eventType.set(HOST_MOVED);
            } else if (!existingHost.ipAddresses().containsAll(hostDescription.ipAddress()) ||
                    !hostDescription.annotations().keys().isEmpty()) {
                eventType.set(HOST_UPDATED);
            } // else, eventType == null; this means we don't send an event

            return new DefaultHost(providerId,
                                   hostId,
                                   hostDescription.hwAddress(),
                                   hostDescription.vlan(),
                                   location,
                                   addresses,
                                   annotations);
        });

        if (oldHost.get() != null) {
            DefaultHost old = oldHost.get();
            locations.remove(old.location(), old);
        }
        locations.put(host.location(), host);

        return eventType.get() != null ? new HostEvent(eventType.get(), host) : null;
    }

    @Override
    public HostEvent removeHost(HostId hostId) {
        Host host = hosts.remove(hostId);
        return host != null ? new HostEvent(HOST_REMOVED, host) : null;
    }

    @Override
    public HostEvent removeIp(HostId hostId, IpAddress ipAddress) {
        DefaultHost host = hosts.compute(hostId, (id, existingHost) -> {
            if (existingHost != null) {
                checkState(Objects.equals(hostId.mac(), existingHost.mac()),
                        "Existing and new MAC addresses differ.");
                checkState(Objects.equals(hostId.vlanId(), existingHost.vlan()),
                        "Existing and new VLANs differ.");

                Set<IpAddress> addresses = existingHost.ipAddresses();
                if (addresses != null && addresses.contains(ipAddress)) {
                    addresses = new HashSet<>(existingHost.ipAddresses());
                    addresses.remove(ipAddress);
                    return new DefaultHost(existingHost.providerId(),
                            hostId,
                            existingHost.mac(),
                            existingHost.vlan(),
                            existingHost.location(),
                            ImmutableSet.copyOf(addresses),
                            existingHost.annotations());
                } else {
                    return existingHost;
                }
            }
            return null;
        });
        return host != null ? new HostEvent(HOST_UPDATED, host) : null;
    }

    @Override
    public int getHostCount() {
        return hosts.size();
    }

    @Override
    public Iterable<Host> getHosts() {
        return ImmutableSet.copyOf(hosts.values());
    }

    @Override
    public Host getHost(HostId hostId) {
        return hosts.get(hostId);
    }

    @Override
    public Set<Host> getHosts(VlanId vlanId) {
        return filter(hosts.values(), host -> Objects.equals(host.vlan(), vlanId));
    }

    @Override
    public Set<Host> getHosts(MacAddress mac) {
        return filter(hosts.values(), host -> Objects.equals(host.mac(), mac));
    }

    @Override
    public Set<Host> getHosts(IpAddress ip) {
        return filter(hosts.values(), host -> host.ipAddresses().contains(ip));
    }

    @Override
    public Set<Host> getConnectedHosts(ConnectPoint connectPoint) {
        synchronized (locations) {
            return ImmutableSet.copyOf(locations.get(connectPoint));
        }
    }

    @Override
    public Set<Host> getConnectedHosts(DeviceId deviceId) {
        Set<Host> filtered;
        synchronized (locations) {
            filtered = locations
                    .entries()
                    .stream()
                    .filter(entry -> entry.getKey().deviceId().equals(deviceId))
                    .map(entry -> entry.getValue())
                    .collect(Collectors.toSet());
        }
        return ImmutableSet.copyOf(filtered);
    }

    private Set<Host> filter(Collection<DefaultHost> collection, Predicate<DefaultHost> predicate) {
        return collection.stream().filter(predicate).collect(Collectors.toSet());
    }

    private class HostLocationTracker implements EventuallyConsistentMapListener<HostId, DefaultHost> {
        @Override
        public void event(EventuallyConsistentMapEvent<HostId, DefaultHost> event) {
            DefaultHost host = checkNotNull(event.value());
            if (event.type() == PUT) {
                boolean isNew = locations.put(host.location(), host);
                notifyDelegate(new HostEvent(isNew ? HOST_ADDED : HOST_UPDATED, host));
            } else if (event.type() == REMOVE) {
                if (locations.remove(host.location(), host)) {
                    notifyDelegate(new HostEvent(HOST_REMOVED, host));
                }

            }
        }
    }
}