/*
 * 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.segmentrouting.grouphandler;

import static com.google.common.base.Preconditions.checkNotNull;
import static org.slf4j.LoggerFactory.getLogger;

import java.net.URI;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Random;
import java.util.Set;

import org.onlab.packet.MacAddress;
import org.onlab.packet.MplsLabel;
import org.onlab.util.KryoNamespace;
import org.onosproject.core.ApplicationId;
import org.onosproject.net.DeviceId;
import org.onosproject.net.Link;
import org.onosproject.net.PortNumber;
import org.onosproject.net.flow.DefaultTrafficTreatment;
import org.onosproject.net.flow.TrafficTreatment;
import org.onosproject.net.flowobjective.DefaultNextObjective;
import org.onosproject.net.flowobjective.FlowObjectiveService;
import org.onosproject.net.flowobjective.NextObjective;
import org.onosproject.net.group.DefaultGroupKey;
import org.onosproject.net.group.GroupKey;
import org.onosproject.net.link.LinkService;
import org.slf4j.Logger;

/**
 * Default ECMP group handler creation module. This component creates a set of
 * ECMP groups for every neighbor that this device is connected to based on
 * whether the current device is an edge device or a transit device.
 */
public class DefaultGroupHandler {
    protected final Logger log = getLogger(getClass());

    protected final DeviceId deviceId;
    protected final ApplicationId appId;
    protected final DeviceProperties deviceConfig;
    protected final List<Integer> allSegmentIds;
    protected final int nodeSegmentId;
    protected final boolean isEdgeRouter;
    protected final MacAddress nodeMacAddr;
    protected LinkService linkService;
    protected FlowObjectiveService flowObjectiveService;

    protected HashMap<DeviceId, Set<PortNumber>> devicePortMap =
            new HashMap<DeviceId, Set<PortNumber>>();
    protected HashMap<PortNumber, DeviceId> portDeviceMap =
            new HashMap<PortNumber, DeviceId>();
    protected HashMap<GroupKey, Integer> deviceNextObjectiveIds =
            new HashMap<GroupKey, Integer>();
    protected Random rand = new Random();

    protected KryoNamespace.Builder kryo = new KryoNamespace.Builder()
            .register(URI.class).register(HashSet.class)
            .register(DeviceId.class).register(PortNumber.class)
            .register(NeighborSet.class).register(PolicyGroupIdentifier.class)
            .register(PolicyGroupParams.class)
            .register(GroupBucketIdentifier.class)
            .register(GroupBucketIdentifier.BucketOutputType.class);

    protected DefaultGroupHandler(DeviceId deviceId, ApplicationId appId,
                                  DeviceProperties config,
                                  LinkService linkService,
                                  FlowObjectiveService flowObjService) {
        this.deviceId = checkNotNull(deviceId);
        this.appId = checkNotNull(appId);
        this.deviceConfig = checkNotNull(config);
        this.linkService = checkNotNull(linkService);
        allSegmentIds = checkNotNull(config.getAllDeviceSegmentIds());
        nodeSegmentId = config.getSegmentId(deviceId);
        isEdgeRouter = config.isEdgeDevice(deviceId);
        nodeMacAddr = checkNotNull(config.getDeviceMac(deviceId));
        this.flowObjectiveService = flowObjService;

        populateNeighborMaps();
    }

    /**
     * Creates a group handler object based on the type of device. If device is
     * of edge type it returns edge group handler, else it returns transit group
     * handler.
     *
     * @param deviceId device identifier
     * @param appId application identifier
     * @param config interface to retrieve the device properties
     * @param linkService link service object
     * @param flowObjService flow objective service object
     * @return default group handler type
     */
    public static DefaultGroupHandler createGroupHandler(DeviceId deviceId,
                                                         ApplicationId appId,
                                                         DeviceProperties config,
                                                         LinkService linkService,
                                                         FlowObjectiveService flowObjService) {
        if (config.isEdgeDevice(deviceId)) {
            return new DefaultEdgeGroupHandler(deviceId, appId, config,
                                               linkService, flowObjService);
        } else {
            return new DefaultTransitGroupHandler(deviceId, appId, config,
                                                  linkService, flowObjService);
        }
    }

    /**
     * Creates the auto created groups for this device based on the current
     * snapshot of the topology.
     */
    // Empty implementations to be overridden by derived classes
    public void createGroups() {
    }

    /**
     * Performs group creation or update procedures when a new link is
     * discovered on this device.
     *
     * @param newLink new neighbor link
     */
    public void linkUp(Link newLink) {

        if (newLink.type() != Link.Type.DIRECT) {
            log.warn("linkUp: unknown link type");
            return;
        }

        if (!newLink.src().deviceId().equals(deviceId)) {
            log.warn("linkUp: deviceId{} doesn't match with link src{}",
                     deviceId, newLink.src().deviceId());
            return;
        }

        log.debug("Device {} linkUp at local port {} to neighbor {}", deviceId,
                  newLink.src().port(), newLink.dst().deviceId());
        if (devicePortMap.get(newLink.dst().deviceId()) == null) {
            // New Neighbor
            newNeighbor(newLink);
        } else {
            // Old Neighbor
            newPortToExistingNeighbor(newLink);
        }
    }

    /**
     * Performs group recovery procedures when a port goes down on this device.
     *
     * @param port port number that has gone down
     */
    public void portDown(PortNumber port) {
        if (portDeviceMap.get(port) == null) {
            log.warn("portDown: unknown port");
            return;
        }
        log.debug("Device {} portDown {} to neighbor {}", deviceId, port,
                  portDeviceMap.get(port));
        Set<NeighborSet> nsSet = computeImpactedNeighborsetForPortEvent(portDeviceMap
                                                                                .get(port),
                                                                        devicePortMap
                                                                                .keySet());
        for (NeighborSet ns : nsSet) {
            // Create the bucket to be removed
            TrafficTreatment.Builder tBuilder = DefaultTrafficTreatment
                    .builder();
            tBuilder.setOutput(port)
                    .setEthDst(deviceConfig.getDeviceMac(portDeviceMap
                                       .get(port))).setEthSrc(nodeMacAddr);
            if (ns.getEdgeLabel() != NeighborSet.NO_EDGE_LABEL) {
                tBuilder.pushMpls().setMpls(MplsLabel.mplsLabel(ns
                                                    .getEdgeLabel()));
            }
            /*
             * GroupBucket removeBucket = DefaultGroupBucket.
             * createSelectGroupBucket(tBuilder.build()); GroupBuckets
             * removeBuckets = new GroupBuckets( Arrays.asList(removeBucket));
             * log.debug("portDown in device{}: " +
             * "groupService.removeBucketsFromGroup " + "for neighborset{}",
             * deviceId, ns); groupService.removeBucketsFromGroup(deviceId,
             * getGroupKey(ns), removeBuckets, getGroupKey(ns), appId);
             */
            //TODO: Use next objective API to update the previously created
            //next objectives.
        }

        devicePortMap.get(portDeviceMap.get(port)).remove(port);
        portDeviceMap.remove(port);
    }

    /**
     * Returns the next objective associated with the neighborset.
     * If there is no next objective for this neighborset, this API
     * would create a next objective and return.
     *
     * @param ns neighborset
     * @return int if found or -1
     */
    public int getNextObjectiveId(NeighborSet ns) {
        Integer nextId = deviceNextObjectiveIds.get(getGroupKey(ns));
        if (nextId == null) {
            createGroupsFromNeighborsets(Collections.singleton(ns));
            nextId = deviceNextObjectiveIds.get(getGroupKey(ns));
            if (nextId == null) {
                log.warn("getNextObjectiveId: unable to create next objective");
                return -1;
            }
        }
        return nextId.intValue();
    }

    // Empty implementation
    protected void newNeighbor(Link newLink) {
    }

    // Empty implementation
    protected void newPortToExistingNeighbor(Link newLink) {
    }

    // Empty implementation
    protected Set<NeighborSet>
        computeImpactedNeighborsetForPortEvent(DeviceId impactedNeighbor,
                                               Set<DeviceId> updatedNeighbors) {
        return null;
    }

    private void populateNeighborMaps() {
        Set<Link> outgoingLinks = linkService.getDeviceEgressLinks(deviceId);
        for (Link link : outgoingLinks) {
            if (link.type() != Link.Type.DIRECT) {
                continue;
            }
            addNeighborAtPort(link.dst().deviceId(), link.src().port());
        }
    }

    protected void addNeighborAtPort(DeviceId neighborId,
                                     PortNumber portToNeighbor) {
        // Update DeviceToPort database
        log.debug("Device {} addNeighborAtPort: neighbor {} at port {}",
                  deviceId, neighborId, portToNeighbor);
        if (devicePortMap.get(neighborId) != null) {
            devicePortMap.get(neighborId).add(portToNeighbor);
        } else {
            Set<PortNumber> ports = new HashSet<PortNumber>();
            ports.add(portToNeighbor);
            devicePortMap.put(neighborId, ports);
        }

        // Update portToDevice database
        if (portDeviceMap.get(portToNeighbor) == null) {
            portDeviceMap.put(portToNeighbor, neighborId);
        }
    }

    protected Set<Set<DeviceId>> getPowerSetOfNeighbors(Set<DeviceId> neighbors) {
        List<DeviceId> list = new ArrayList<DeviceId>(neighbors);
        Set<Set<DeviceId>> sets = new HashSet<Set<DeviceId>>();
        // get the number of elements in the neighbors
        int elements = list.size();
        // the number of members of a power set is 2^n
        // including the empty set
        int powerElements = (1 << elements);

        // run a binary counter for the number of power elements
        // NOTE: Exclude empty set
        for (long i = 1; i < powerElements; i++) {
            Set<DeviceId> neighborSubSet = new HashSet<DeviceId>();
            for (int j = 0; j < elements; j++) {
                if ((i >> j) % 2 == 1) {
                    neighborSubSet.add(list.get(j));
                }
            }
            sets.add(neighborSubSet);
        }
        return sets;
    }

    private boolean isSegmentIdSameAsNodeSegmentId(DeviceId deviceId, int sId) {
        return (deviceConfig.getSegmentId(deviceId) == sId);
    }

    protected List<Integer> getSegmentIdsTobePairedWithNeighborSet(Set<DeviceId> neighbors) {

        List<Integer> nsSegmentIds = new ArrayList<Integer>();

        // Always pair up with no edge label
        // If (neighbors.size() == 1) {
        nsSegmentIds.add(-1);
        // }

        // Filter out SegmentIds matching with the
        // nodes in the combo
        for (Integer sId : allSegmentIds) {
            if (sId.equals(nodeSegmentId)) {
                continue;
            }
            boolean filterOut = false;
            // Check if the edge label being set is of
            // any node in the Neighbor set
            for (DeviceId deviceId : neighbors) {
                if (isSegmentIdSameAsNodeSegmentId(deviceId, sId)) {
                    filterOut = true;
                    break;
                }
            }
            if (!filterOut) {
                nsSegmentIds.add(sId);
            }
        }
        return nsSegmentIds;
    }

    protected void createGroupsFromNeighborsets(Set<NeighborSet> nsSet) {
        for (NeighborSet ns : nsSet) {
            int nextId = flowObjectiveService.allocateNextId();
            NextObjective.Builder nextObjBuilder = DefaultNextObjective
                    .builder().withId(nextId)
                    .withType(NextObjective.Type.HASHED).fromApp(appId);
            for (DeviceId d : ns.getDeviceIds()) {
                for (PortNumber sp : devicePortMap.get(d)) {
                    TrafficTreatment.Builder tBuilder = DefaultTrafficTreatment
                            .builder();
                    tBuilder.setOutput(sp)
                            .setEthDst(deviceConfig.getDeviceMac(d))
                            .setEthSrc(nodeMacAddr);
                    if (ns.getEdgeLabel() != NeighborSet.NO_EDGE_LABEL) {
                        tBuilder.pushMpls().setMpls(MplsLabel.mplsLabel(ns
                                                            .getEdgeLabel()));
                    }
                    nextObjBuilder.addTreatment(tBuilder.build());
                }
            }

            NextObjective nextObj = nextObjBuilder.add();
            flowObjectiveService.next(deviceId, nextObj);
            deviceNextObjectiveIds.put(getGroupKey(ns), nextId);
        }
    }

    public GroupKey getGroupKey(Object obj) {
        return new DefaultGroupKey(kryo.build().serialize(obj));
    }

}