/*
 * 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.store.packet.impl;

import com.google.common.collect.ImmutableSet;
import com.google.common.collect.Lists;
import com.google.common.collect.Sets;
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.util.KryoNamespace;
import org.onosproject.cluster.ClusterService;
import org.onosproject.cluster.NodeId;
import org.onosproject.mastership.MastershipService;
import org.onosproject.net.flow.TrafficSelector;
import org.onosproject.net.packet.OutboundPacket;
import org.onosproject.net.packet.PacketEvent;
import org.onosproject.net.packet.PacketEvent.Type;
import org.onosproject.net.packet.PacketRequest;
import org.onosproject.net.packet.PacketStore;
import org.onosproject.net.packet.PacketStoreDelegate;
import org.onosproject.store.AbstractStore;
import org.onosproject.store.cluster.messaging.ClusterCommunicationService;
import org.onosproject.store.cluster.messaging.MessageSubject;
import org.onosproject.store.serializers.KryoNamespaces;
import org.onosproject.store.serializers.KryoSerializer;
import org.onosproject.store.service.ConsistentMap;
import org.onosproject.store.service.Serializer;
import org.onosproject.store.service.StorageService;
import org.slf4j.Logger;

import java.util.List;
import java.util.Set;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.atomic.AtomicBoolean;

import static org.onlab.util.Tools.groupedThreads;
import static org.slf4j.LoggerFactory.getLogger;

/**
 * Distributed packet store implementation allowing packets to be sent to
 * remote instances.
 */
@Component(immediate = true)
@Service
public class DistributedPacketStore
        extends AbstractStore<PacketEvent, PacketStoreDelegate>
        implements PacketStore {

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

    // TODO: make this configurable.
    private static final int MESSAGE_HANDLER_THREAD_POOL_SIZE = 4;

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

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

    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
    protected ClusterCommunicationService communicationService;

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

    private PacketRequestTracker tracker;

    private static final MessageSubject PACKET_OUT_SUBJECT =
            new MessageSubject("packet-out");

    private static final KryoSerializer SERIALIZER = new KryoSerializer() {
        @Override
        protected void setupKryoPool() {
            serializerPool = KryoNamespace.newBuilder()
                    .register(KryoNamespaces.API)
                    .nextId(KryoNamespaces.BEGIN_USER_CUSTOM_ID)
                    .build();
        }
    };

    private ExecutorService messageHandlingExecutor;

    @Activate
    public void activate() {
        messageHandlingExecutor = Executors.newFixedThreadPool(
                MESSAGE_HANDLER_THREAD_POOL_SIZE,
                groupedThreads("onos/store/packet", "message-handlers"));

        communicationService.<OutboundPacket>addSubscriber(PACKET_OUT_SUBJECT,
                SERIALIZER::decode,
                packet -> notifyDelegate(new PacketEvent(Type.EMIT, packet)),
                messageHandlingExecutor);

        tracker = new PacketRequestTracker();

        log.info("Started");
    }

    @Deactivate
    public void deactivate() {
        communicationService.removeSubscriber(PACKET_OUT_SUBJECT);
        messageHandlingExecutor.shutdown();
        tracker = null;
        log.info("Stopped");
    }

    @Override
    public void emit(OutboundPacket packet) {
        NodeId myId = clusterService.getLocalNode().id();
        NodeId master = mastershipService.getMasterFor(packet.sendThrough());

        if (master == null) {
            return;
        }

        if (myId.equals(master)) {
            notifyDelegate(new PacketEvent(Type.EMIT, packet));
            return;
        }

        communicationService.unicast(packet, PACKET_OUT_SUBJECT, SERIALIZER::encode, master)
                            .whenComplete((r, error) -> {
                                if (error != null) {
                                    log.warn("Failed to send packet-out to {}", master, error);
                                }
                            });
    }

    @Override
    public void requestPackets(PacketRequest request) {
        tracker.add(request);
    }

    @Override
    public void cancelPackets(PacketRequest request) {
        tracker.remove(request);
    }

    @Override
    public List<PacketRequest> existingRequests() {
        return tracker.requests();
    }

    private class PacketRequestTracker {

        private ConsistentMap<TrafficSelector, Set<PacketRequest>> requests;

        public PacketRequestTracker() {
            requests = storageService.<TrafficSelector, Set<PacketRequest>>consistentMapBuilder()
                    .withName("onos-packet-requests")
                    .withPartitionsDisabled()
                    .withSerializer(Serializer.using(KryoNamespaces.API))
                    .build();
        }

        public void add(PacketRequest request) {
            AtomicBoolean firstRequest = new AtomicBoolean(false);
            requests.compute(request.selector(), (s, existingRequests) -> {
                if (existingRequests == null) {
                    firstRequest.set(true);
                    return ImmutableSet.of(request);
                } else if (!existingRequests.contains(request)) {
                    return ImmutableSet.<PacketRequest>builder()
                                       .addAll(existingRequests)
                                       .add(request)
                                       .build();
                } else {
                    return existingRequests;
                }
            });

            if (firstRequest.get() && delegate != null) {
                // The instance that makes the first request will push to all devices
                delegate.requestPackets(request);
            }
        }

        public void remove(PacketRequest request) {
            AtomicBoolean removedLast = new AtomicBoolean(false);
            requests.computeIfPresent(request.selector(), (s, existingRequests) -> {
                if (existingRequests.contains(request)) {
                    Set<PacketRequest> newRequests = Sets.newHashSet(existingRequests);
                    newRequests.remove(request);
                    if (newRequests.size() > 0) {
                        return ImmutableSet.copyOf(newRequests);
                    } else {
                        removedLast.set(true);
                        return null;
                    }
                } else {
                    return existingRequests;
                }
            });

            if (removedLast.get() && delegate != null) {
                // The instance that removes the last request will remove from all devices
                delegate.cancelPackets(request);
            }

        }

        public List<PacketRequest> requests() {
            List<PacketRequest> list = Lists.newArrayList();
            requests.values().forEach(v -> list.addAll(v.value()));
            list.sort((o1, o2) -> o1.priority().priorityValue() - o2.priority().priorityValue());
            return list;
        }
    }
}