/*
 * 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.driver.pipeline;

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

import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Deque;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.stream.Collectors;

import org.onlab.osgi.ServiceDirectory;
import org.onlab.packet.Ethernet;
import org.onlab.packet.MacAddress;
import org.onlab.packet.MplsLabel;
import org.onlab.packet.VlanId;
import org.onlab.util.KryoNamespace;
import org.onosproject.core.ApplicationId;
import org.onosproject.core.CoreService;
import org.onosproject.core.DefaultGroupId;
import org.onosproject.net.DeviceId;
import org.onosproject.net.Port;
import org.onosproject.net.PortNumber;
import org.onosproject.net.behaviour.NextGroup;
import org.onosproject.net.behaviour.Pipeliner;
import org.onosproject.net.behaviour.PipelinerContext;
import org.onosproject.net.device.DeviceService;
import org.onosproject.net.driver.AbstractHandlerBehaviour;
import org.onosproject.net.flow.DefaultFlowRule;
import org.onosproject.net.flow.DefaultTrafficSelector;
import org.onosproject.net.flow.DefaultTrafficTreatment;
import org.onosproject.net.flow.FlowRule;
import org.onosproject.net.flow.FlowRuleOperations;
import org.onosproject.net.flow.FlowRuleOperationsContext;
import org.onosproject.net.flow.FlowRuleService;
import org.onosproject.net.flow.TrafficSelector;
import org.onosproject.net.flow.TrafficTreatment;
import org.onosproject.net.flow.criteria.Criteria;
import org.onosproject.net.flow.criteria.Criterion;
import org.onosproject.net.flow.criteria.Criterion.Type;
import org.onosproject.net.flow.criteria.EthCriterion;
import org.onosproject.net.flow.criteria.EthTypeCriterion;
import org.onosproject.net.flow.criteria.IPCriterion;
import org.onosproject.net.flow.criteria.MplsBosCriterion;
import org.onosproject.net.flow.criteria.MplsCriterion;
import org.onosproject.net.flow.criteria.PortCriterion;
import org.onosproject.net.flow.criteria.VlanIdCriterion;
import org.onosproject.net.flow.instructions.Instruction;
import org.onosproject.net.flow.instructions.Instructions.OutputInstruction;
import org.onosproject.net.flow.instructions.L2ModificationInstruction;
import org.onosproject.net.flow.instructions.L2ModificationInstruction.L2SubType;
import org.onosproject.net.flow.instructions.L2ModificationInstruction.ModEtherInstruction;
import org.onosproject.net.flow.instructions.L2ModificationInstruction.ModMplsLabelInstruction;
import org.onosproject.net.flow.instructions.L2ModificationInstruction.ModVlanIdInstruction;
import org.onosproject.net.flowobjective.FilteringObjective;
import org.onosproject.net.flowobjective.FlowObjectiveStore;
import org.onosproject.net.flowobjective.ForwardingObjective;
import org.onosproject.net.flowobjective.NextObjective;
import org.onosproject.net.flowobjective.Objective;
import org.onosproject.net.flowobjective.ObjectiveError;
import org.onosproject.net.group.DefaultGroupBucket;
import org.onosproject.net.group.DefaultGroupDescription;
import org.onosproject.net.group.DefaultGroupKey;
import org.onosproject.net.group.Group;
import org.onosproject.net.group.GroupBucket;
import org.onosproject.net.group.GroupBuckets;
import org.onosproject.net.group.GroupDescription;
import org.onosproject.net.group.GroupEvent;
import org.onosproject.net.group.GroupKey;
import org.onosproject.net.group.GroupListener;
import org.onosproject.net.group.GroupService;
import org.onosproject.store.serializers.KryoNamespaces;
import org.slf4j.Logger;

import com.google.common.cache.Cache;
import com.google.common.cache.CacheBuilder;
import com.google.common.cache.RemovalCause;
import com.google.common.cache.RemovalNotification;

/**
 * Driver for Broadcom's OF-DPA v2.0 TTP.
 *
 */
public class OFDPA2Pipeline extends AbstractHandlerBehaviour implements Pipeliner {

    protected static final int PORT_TABLE = 0;
    protected static final int VLAN_TABLE = 10;
    protected static final int TMAC_TABLE = 20;
    protected static final int UNICAST_ROUTING_TABLE = 30;
    protected static final int MULTICAST_ROUTING_TABLE = 40;
    protected static final int MPLS_TABLE_0 = 23;
    protected static final int MPLS_TABLE_1 = 24;
    protected static final int BRIDGING_TABLE = 50;
    protected static final int ACL_TABLE = 60;
    protected static final int MAC_LEARNING_TABLE = 254;
    protected static final long OFPP_MAX = 0xffffff00L;

    private static final int HIGHEST_PRIORITY = 0xffff;
    protected static final int DEFAULT_PRIORITY = 0x8000;
    protected static final int LOWEST_PRIORITY = 0x0;

    /*
     * OFDPA requires group-id's to have a certain form.
     * L2 Interface Groups have <4bits-0><12bits-vlanid><16bits-portid>
     * L3 Unicast Groups have <4bits-2><28bits-index>
     * MPLS Interface Groups have <4bits-9><4bits:0><24bits-index>
     * L3 ECMP Groups have <4bits-7><28bits-index>
     * L2 Flood Groups have <4bits-4><12bits-vlanid><16bits-index>
     * L3 VPN Groups have <4bits-9><4bits-2><24bits-index>
     */
    private static final int L2INTERFACEMASK = 0x0;
    private static final int L3UNICASTMASK = 0x20000000;
    private static final int MPLSINTERFACEMASK = 0x90000000;
    private static final int L3ECMPMASK = 0x70000000;
    private static final int L2FLOODMASK = 0x40000000;
    private static final int L3VPNMASK = 0x92000000;

    private final Logger log = getLogger(getClass());
    private ServiceDirectory serviceDirectory;
    protected FlowRuleService flowRuleService;
    private CoreService coreService;
    protected GroupService groupService;
    protected FlowObjectiveStore flowObjectiveStore;
    protected DeviceId deviceId;
    protected ApplicationId driverId;
    protected DeviceService deviceService;
    protected KryoNamespace appKryo = new KryoNamespace.Builder()
        .register(KryoNamespaces.API)
        .register(GroupKey.class)
        .register(DefaultGroupKey.class)
        .register(OfdpaNextGroup.class)
        .register(byte[].class)
        .register(ArrayDeque.class)
        .build();

    private Cache<GroupKey, List<OfdpaNextGroup>> pendingNextObjectives;
    private ConcurrentHashMap<GroupKey, Set<GroupChainElem>> pendingGroups;

    private ScheduledExecutorService groupChecker =
            Executors.newScheduledThreadPool(2, groupedThreads("onos/pipeliner",
                                                               "ofdpa2-%d"));
    private Set<IPCriterion> sentIpFilters = Collections.newSetFromMap(
                                               new ConcurrentHashMap<IPCriterion, Boolean>());

    // local stores for port-vlan mapping
    Map<PortNumber, VlanId> port2Vlan = new ConcurrentHashMap<PortNumber, VlanId>();
    Map<VlanId, Set<PortNumber>> vlan2Port = new ConcurrentHashMap<VlanId,
                                                        Set<PortNumber>>();

    // local store for pending bucketAdds - by design there can only be one
    // pending bucket for a group
    ConcurrentHashMap<Integer, NextObjective> pendingBuckets = new ConcurrentHashMap<>();

    // index number for group creation
    AtomicInteger l3vpnindex = new AtomicInteger(0);


    @Override
    public void init(DeviceId deviceId, PipelinerContext context) {
        this.serviceDirectory = context.directory();
        this.deviceId = deviceId;

        pendingNextObjectives = CacheBuilder.newBuilder()
                .expireAfterWrite(20, TimeUnit.SECONDS)
                .removalListener((
                     RemovalNotification<GroupKey, List<OfdpaNextGroup>> notification) -> {
                         if (notification.getCause() == RemovalCause.EXPIRED) {
                             notification.getValue().forEach(ofdpaNextGrp ->
                                 fail(ofdpaNextGrp.nextObj,
                                      ObjectiveError.GROUPINSTALLATIONFAILED));

                         }
                }).build();

        groupChecker.scheduleAtFixedRate(new GroupChecker(), 0, 500, TimeUnit.MILLISECONDS);
        pendingGroups = new ConcurrentHashMap<GroupKey, Set<GroupChainElem>>();

        coreService = serviceDirectory.get(CoreService.class);
        flowRuleService = serviceDirectory.get(FlowRuleService.class);
        groupService = serviceDirectory.get(GroupService.class);
        flowObjectiveStore = context.store();
        deviceService = serviceDirectory.get(DeviceService.class);
        groupService.addListener(new InnerGroupListener());

        driverId = coreService.registerApplication(
                "org.onosproject.driver.OFDPA2Pipeline");

        // OF-DPA does not require initializing the pipeline as it puts default
        // rules automatically in the hardware. However emulation of OFDPA in
        // software switches does require table-miss-entries.
        initializePipeline();

    }

    protected void initializePipeline() {

    }

    //////////////////////////////////////
    //  Flow Objectives
    //////////////////////////////////////

    @Override
    public void filter(FilteringObjective filteringObjective) {
        if (filteringObjective.type() == FilteringObjective.Type.PERMIT) {
            processFilter(filteringObjective,
                          filteringObjective.op() == Objective.Operation.ADD,
                          filteringObjective.appId());
        } else {
            // Note that packets that don't match the PERMIT filter are
            // automatically denied. The DENY filter is used to deny packets
            // that are otherwise permitted by the PERMIT filter.
            // Use ACL table flow rules here for DENY filtering objectives
            log.debug("filter objective other than PERMIT currently not supported");
            fail(filteringObjective, ObjectiveError.UNSUPPORTED);
        }
    }

    @Override
    public void forward(ForwardingObjective fwd) {
        Collection<FlowRule> rules;
        FlowRuleOperations.Builder flowOpsBuilder = FlowRuleOperations.builder();

        rules = processForward(fwd);
        switch (fwd.op()) {
            case ADD:
                rules.stream()
                        .filter(rule -> rule != null)
                        .forEach(flowOpsBuilder::add);
                break;
            case REMOVE:
                rules.stream()
                        .filter(rule -> rule != null)
                        .forEach(flowOpsBuilder::remove);
                break;
            default:
                fail(fwd, ObjectiveError.UNKNOWN);
                log.warn("Unknown forwarding type {}", fwd.op());
        }

        flowRuleService.apply(flowOpsBuilder.build(new FlowRuleOperationsContext() {
            @Override
            public void onSuccess(FlowRuleOperations ops) {
                pass(fwd);
            }

            @Override
            public void onError(FlowRuleOperations ops) {
                fail(fwd, ObjectiveError.FLOWINSTALLATIONFAILED);
            }
        }));
    }

    @Override
    public void next(NextObjective nextObjective) {
        NextGroup nextGroup = flowObjectiveStore.getNextGroup(nextObjective.id());
        switch (nextObjective.op()) {
        case ADD:
            if (nextGroup != null) {
                log.warn("Cannot add next {} that already exists in device {}",
                         nextObjective.id(), deviceId);
                return;
            }
            log.debug("Processing NextObjective id{} in dev{} - add group",
                      nextObjective.id(), deviceId);
            addGroup(nextObjective);
            break;
        case ADD_TO_EXISTING:
            if (nextGroup != null) {
                log.debug("Processing NextObjective id{} in dev{} - add bucket",
                          nextObjective.id(), deviceId);
                addBucketToGroup(nextObjective, nextGroup);
            } else {
                // it is possible that group-chain has not been fully created yet
                log.debug("Waiting to add bucket to group for next-id:{} in dev:{}",
                          nextObjective.id(), deviceId);
                // by design only one pending bucket is allowed for the group
                pendingBuckets.put(nextObjective.id(), nextObjective);
            }
            break;
        case REMOVE:
            if (nextGroup == null) {
                log.warn("Cannot remove next {} that does not exist in device {}",
                         nextObjective.id(), deviceId);
                return;
            }
            log.debug("Processing NextObjective id{}  in dev{} - remove group",
                      nextObjective.id(), deviceId);
            removeGroup(nextObjective, nextGroup);
            break;
        case REMOVE_FROM_EXISTING:
            if (nextGroup == null) {
                log.warn("Cannot remove from next {} that does not exist in device {}",
                         nextObjective.id(), deviceId);
                return;
            }
            log.debug("Processing NextObjective id{} in dev{} - remove bucket",
                      nextObjective.id(), deviceId);
            removeBucketFromGroup(nextObjective, nextGroup);
            break;
        default:
            log.warn("Unsupported operation {}", nextObjective.op());
        }
    }

    //////////////////////////////////////
    //  Flow handling
    //////////////////////////////////////

    /**
     * As per OFDPA 2.0 TTP, filtering of VLAN ids, MAC addresses (for routing)
     * and IP addresses configured on switch ports happen in different tables.
     * Note that IP filtering rules need to be added to the ACL table, as there
     * is no mechanism to send to controller via IP table.
     *
     * @param filt      the filtering objective
     * @param install   indicates whether to add or remove the objective
     * @param applicationId     the application that sent this objective
     */
    private void processFilter(FilteringObjective filt,
                               boolean install, ApplicationId applicationId) {
        // This driver only processes filtering criteria defined with switch
        // ports as the key
        PortCriterion portCriterion = null;
        EthCriterion ethCriterion = null;
        VlanIdCriterion vidCriterion = null;
        Collection<IPCriterion> ips = new ArrayList<IPCriterion>();
        if (!filt.key().equals(Criteria.dummy()) &&
                filt.key().type() == Criterion.Type.IN_PORT) {
            portCriterion = (PortCriterion) filt.key();
        } else {
            log.warn("No key defined in filtering objective from app: {}. Not"
                    + "processing filtering objective", applicationId);
            fail(filt, ObjectiveError.UNKNOWN);
            return;
        }
        // convert filtering conditions for switch-intfs into flowrules
        FlowRuleOperations.Builder ops = FlowRuleOperations.builder();
        for (Criterion criterion : filt.conditions()) {
            if (criterion.type() == Criterion.Type.ETH_DST) {
                ethCriterion = (EthCriterion) criterion;
            } else if (criterion.type() == Criterion.Type.VLAN_VID) {
                vidCriterion = (VlanIdCriterion) criterion;
            } else if (criterion.type() == Criterion.Type.IPV4_DST) {
                ips.add((IPCriterion) criterion);
            } else {
                log.error("Unsupported filter {}", criterion);
                fail(filt, ObjectiveError.UNSUPPORTED);
                return;
            }
        }

        VlanId assignedVlan = null;
        if (vidCriterion != null && vidCriterion.vlanId() == VlanId.NONE) {
            // untagged packets are assigned vlans in OF-DPA
            if (filt.meta() == null) {
                log.error("Missing metadata in filtering objective required "
                        + "for vlan assignment in dev {}", deviceId);
                fail(filt, ObjectiveError.BADPARAMS);
                return;
            }
            for (Instruction i : filt.meta().allInstructions()) {
                if (i instanceof ModVlanIdInstruction) {
                    assignedVlan = ((ModVlanIdInstruction) i).vlanId();
                }
            }
            if (assignedVlan == null) {
                log.error("Driver requires an assigned vlan-id to tag incoming "
                        + "untagged packets. Not processing vlan filters on "
                        + "device {}", deviceId);
                fail(filt, ObjectiveError.BADPARAMS);
                return;
            }
        }

        if (ethCriterion == null) {
            log.debug("filtering objective missing dstMac, cannot program TMAC table");
        } else {
            for (FlowRule tmacRule : processEthDstFilter(portCriterion, ethCriterion,
                                                         vidCriterion, assignedVlan,
                                                         applicationId)) {
                log.debug("adding MAC filtering rules in TMAC table: {} for dev: {}",
                          tmacRule, deviceId);
                ops = install ? ops.add(tmacRule) : ops.remove(tmacRule);
            }
        }

        if (ethCriterion == null || vidCriterion == null) {
            log.debug("filtering objective missing dstMac or vlan, cannot program"
                    + "Vlan Table");
        } else {
            for (FlowRule vlanRule : processVlanIdFilter(portCriterion, vidCriterion,
                                                         assignedVlan,
                                                         applicationId)) {
                log.debug("adding VLAN filtering rule in VLAN table: {} for dev: {}",
                          vlanRule, deviceId);
                ops = install ? ops.add(vlanRule) : ops.remove(vlanRule);
            }
        }

        for (IPCriterion ipaddr : ips) {
            // since we ignore port information for IP rules, and the same (gateway) IP
            // can be configured on multiple ports, we make sure that we send
            // only a single rule to the switch.
            if (!sentIpFilters.contains(ipaddr)) {
                sentIpFilters.add(ipaddr);
                log.debug("adding IP filtering rules in ACL table {} for dev: {}",
                          ipaddr, deviceId);
                TrafficSelector.Builder selector = DefaultTrafficSelector.builder();
                TrafficTreatment.Builder treatment = DefaultTrafficTreatment.builder();
                selector.matchEthType(Ethernet.TYPE_IPV4);
                selector.matchIPDst(ipaddr.ip());
                treatment.setOutput(PortNumber.CONTROLLER);
                FlowRule rule = DefaultFlowRule.builder()
                        .forDevice(deviceId)
                        .withSelector(selector.build())
                        .withTreatment(treatment.build())
                        .withPriority(HIGHEST_PRIORITY)
                        .fromApp(applicationId)
                        .makePermanent()
                        .forTable(ACL_TABLE).build();
                ops = install ? ops.add(rule) : ops.remove(rule);
            }
        }

        // apply filtering flow rules
        flowRuleService.apply(ops.build(new FlowRuleOperationsContext() {
            @Override
            public void onSuccess(FlowRuleOperations ops) {
                log.info("Applied {} filtering rules in device {}",
                         ops.stages().get(0).size(), deviceId);
                pass(filt);
            }

            @Override
            public void onError(FlowRuleOperations ops) {
                log.info("Failed to apply all filtering rules in dev {}", deviceId);
                fail(filt, ObjectiveError.FLOWINSTALLATIONFAILED);
            }
        }));

    }

    /**
     * Allows untagged packets into pipeline by assigning a vlan id.
     * Vlan assignment is done by the application.
     * Allows tagged packets into pipeline as per configured port-vlan info.
     *
     * @param portCriterion   port on device for which this filter is programmed
     * @param vidCriterion   vlan assigned to port, or NONE for untagged
     * @param assignedVlan   assigned vlan-id for untagged packets
     * @param applicationId  for application programming this filter
     * @return list of FlowRule for port-vlan filters
     */
    protected List<FlowRule> processVlanIdFilter(PortCriterion portCriterion,
                                                 VlanIdCriterion vidCriterion,
                                                 VlanId assignedVlan,
                                                 ApplicationId applicationId) {
        List<FlowRule> rules = new ArrayList<FlowRule>();
        TrafficSelector.Builder selector = DefaultTrafficSelector.builder();
        TrafficTreatment.Builder treatment = DefaultTrafficTreatment.builder();
        selector.matchVlanId(vidCriterion.vlanId());
        treatment.transition(TMAC_TABLE);

        VlanId storeVlan = null;
        if (vidCriterion.vlanId() == VlanId.NONE) {
            // untagged packets are assigned vlans
            treatment.pushVlan().setVlanId(assignedVlan);
            // XXX ofdpa will require an additional vlan match on the assigned vlan
            // and it may not require the push. This is not in compliance with OF
            // standard. Waiting on what the exact flows are going to look like.
            storeVlan = assignedVlan;
        } else {
            storeVlan = vidCriterion.vlanId();
        }

        // ofdpa cannot match on ALL portnumber, so we need to use separate
        // rules for each port.
        List<PortNumber> portnums = new ArrayList<PortNumber>();
        if (portCriterion.port() == PortNumber.ALL) {
            for (Port port : deviceService.getPorts(deviceId)) {
                if (port.number().toLong() > 0 && port.number().toLong() < OFPP_MAX) {
                    portnums.add(port.number());
                }
            }
        } else {
            portnums.add(portCriterion.port());
        }

        for (PortNumber pnum : portnums) {
            // update storage
            port2Vlan.put(pnum, storeVlan);
            Set<PortNumber> vlanPorts = vlan2Port.get(storeVlan);
            if (vlanPorts == null) {
                vlanPorts = Collections.newSetFromMap(
                                    new ConcurrentHashMap<PortNumber, Boolean>());
                vlanPorts.add(pnum);
                vlan2Port.put(storeVlan, vlanPorts);
            } else {
                vlanPorts.add(pnum);
            }
            // create rest of flowrule
            selector.matchInPort(pnum);
            FlowRule rule = DefaultFlowRule.builder()
                    .forDevice(deviceId)
                    .withSelector(selector.build())
                    .withTreatment(treatment.build())
                    .withPriority(DEFAULT_PRIORITY)
                    .fromApp(applicationId)
                    .makePermanent()
                    .forTable(VLAN_TABLE).build();
            rules.add(rule);
        }
        return rules;
    }

    /**
     * Allows routed packets with correct destination MAC to be directed
     * to unicast-IP routing table or MPLS forwarding table.
     *
     * @param portCriterion  port on device for which this filter is programmed
     * @param ethCriterion   dstMac of device for which is filter is programmed
     * @param vidCriterion   vlan assigned to port, or NONE for untagged
     * @param assignedVlan   assigned vlan-id for untagged packets
     * @param applicationId  for application programming this filter
     * @return list of FlowRule for port-vlan filters

     */
    protected List<FlowRule> processEthDstFilter(PortCriterion portCriterion,
                                                 EthCriterion ethCriterion,
                                                 VlanIdCriterion vidCriterion,
                                                 VlanId assignedVlan,
                                                 ApplicationId applicationId) {
        //handling untagged packets via assigned VLAN
        if (vidCriterion.vlanId() == VlanId.NONE) {
            vidCriterion = (VlanIdCriterion) Criteria.matchVlanId(assignedVlan);
        }
        // ofdpa cannot match on ALL portnumber, so we need to use separate
        // rules for each port.
        List<PortNumber> portnums = new ArrayList<PortNumber>();
        if (portCriterion.port() == PortNumber.ALL) {
            for (Port port : deviceService.getPorts(deviceId)) {
                if (port.number().toLong() > 0 && port.number().toLong() < OFPP_MAX) {
                    portnums.add(port.number());
                }
            }
        } else {
            portnums.add(portCriterion.port());
        }

        List<FlowRule> rules = new ArrayList<FlowRule>();
        for (PortNumber pnum : portnums) {
            // for unicast IP packets
            TrafficSelector.Builder selector = DefaultTrafficSelector.builder();
            TrafficTreatment.Builder treatment = DefaultTrafficTreatment.builder();
            selector.matchInPort(pnum);
            selector.matchVlanId(vidCriterion.vlanId());
            selector.matchEthType(Ethernet.TYPE_IPV4);
            selector.matchEthDst(ethCriterion.mac());
            treatment.transition(UNICAST_ROUTING_TABLE);
            FlowRule rule = DefaultFlowRule.builder()
                    .forDevice(deviceId)
                    .withSelector(selector.build())
                    .withTreatment(treatment.build())
                    .withPriority(DEFAULT_PRIORITY)
                    .fromApp(applicationId)
                    .makePermanent()
                    .forTable(TMAC_TABLE).build();
            rules.add(rule);
            //for MPLS packets
            selector = DefaultTrafficSelector.builder();
            treatment = DefaultTrafficTreatment.builder();
            selector.matchInPort(pnum);
            selector.matchVlanId(vidCriterion.vlanId());
            selector.matchEthType(Ethernet.MPLS_UNICAST);
            selector.matchEthDst(ethCriterion.mac());
            treatment.transition(MPLS_TABLE_0);
            rule = DefaultFlowRule.builder()
                    .forDevice(deviceId)
                    .withSelector(selector.build())
                    .withTreatment(treatment.build())
                    .withPriority(DEFAULT_PRIORITY)
                    .fromApp(applicationId)
                    .makePermanent()
                    .forTable(TMAC_TABLE).build();
            rules.add(rule);
        }
        return rules;
    }

    private Collection<FlowRule> processForward(ForwardingObjective fwd) {
        switch (fwd.flag()) {
            case SPECIFIC:
                return processSpecific(fwd);
            case VERSATILE:
                return processVersatile(fwd);
            default:
                fail(fwd, ObjectiveError.UNKNOWN);
                log.warn("Unknown forwarding flag {}", fwd.flag());
        }
        return Collections.emptySet();
    }

    /**
     * In the OF-DPA 2.0 pipeline, versatile forwarding objectives go to the
     * ACL table.
     * @param fwd  the forwarding objective of type 'versatile'
     * @return     a collection of flow rules to be sent to the switch. An empty
     *             collection may be returned if there is a problem in processing
     *             the flow rule
     */
    private Collection<FlowRule> processVersatile(ForwardingObjective fwd) {
        log.info("Processing versatile forwarding objective");
        TrafficSelector selector = fwd.selector();

        EthTypeCriterion ethType =
                (EthTypeCriterion) selector.getCriterion(Criterion.Type.ETH_TYPE);
        if (ethType == null) {
            log.error("Versatile forwarding objective must include ethType");
            fail(fwd, ObjectiveError.BADPARAMS);
            return Collections.emptySet();
        }
        if (fwd.nextId() == null && fwd.treatment() == null) {
            log.error("Forwarding objective {} from {} must contain "
                    + "nextId or Treatment", fwd.selector(), fwd.appId());
            return Collections.emptySet();
        }
        // XXX driver does not currently do type checking as per Tables 65-67 in
        // OFDPA 2.0 spec. The only allowed treatment is a punt to the controller.
        if (fwd.treatment() != null &&
                fwd.treatment().allInstructions().size() == 1 &&
                fwd.treatment().allInstructions().get(0).type() == Instruction.Type.OUTPUT) {
            OutputInstruction o = (OutputInstruction) fwd.treatment().allInstructions().get(0);
            if (o.port() == PortNumber.CONTROLLER) {
                FlowRule.Builder ruleBuilder = DefaultFlowRule.builder()
                        .fromApp(fwd.appId())
                        .withPriority(fwd.priority())
                        .forDevice(deviceId)
                        .withSelector(fwd.selector())
                        .withTreatment(fwd.treatment())
                        .makePermanent()
                        .forTable(ACL_TABLE);
                return Collections.singletonList(ruleBuilder.build());
            } else {
                log.warn("Only allowed treatments in versatile forwarding "
                        + "objectives are punts to the controller");
                return Collections.emptySet();
            }
        }

        if (fwd.nextId() != null) {
            // XXX overide case
            log.warn("versatile objective --> next Id not yet implemeted");
        }
        return Collections.emptySet();
    }

    /**
     * In the OF-DPA 2.0 pipeline, specific forwarding refers to the IP table
     * (unicast or multicast) or the L2 table (mac + vlan) or the MPLS table.
     *
     * @param fwd the forwarding objective of type 'specific'
     * @return    a collection of flow rules. Typically there will be only one
     *            for this type of forwarding objective. An empty set may be
     *            returned if there is an issue in processing the objective.
     */
    protected Collection<FlowRule> processSpecific(ForwardingObjective fwd) {
        log.trace("Processing specific fwd objective:{} in dev:{} with next:{}",
                  fwd.id(), deviceId, fwd.nextId());
        boolean isEthTypeObj = isSupportedEthTypeObjective(fwd);
        boolean isEthDstObj = isSupportedEthDstObjective(fwd);

        if (isEthTypeObj) {
            return processEthTypeSpecific(fwd);
        } else if (isEthDstObj) {
            return processEthDstSpecific(fwd);
        } else {
            log.warn("processSpecific: Unsupported forwarding objective "
                    + "criteria fwd:{} in dev:{}", fwd.nextId(), deviceId);
            fail(fwd, ObjectiveError.UNSUPPORTED);
            return Collections.emptySet();
        }
    }

    private boolean isSupportedEthTypeObjective(ForwardingObjective fwd) {
        TrafficSelector selector = fwd.selector();
        EthTypeCriterion ethType = (EthTypeCriterion) selector
                .getCriterion(Criterion.Type.ETH_TYPE);
        if ((ethType == null) ||
                ((ethType.ethType().toShort() != Ethernet.TYPE_IPV4) &&
                        (ethType.ethType().toShort() != Ethernet.MPLS_UNICAST))) {
            return false;
        }
        return true;
    }

    private boolean isSupportedEthDstObjective(ForwardingObjective fwd) {
        TrafficSelector selector = fwd.selector();
        EthCriterion ethDst = (EthCriterion) selector
                .getCriterion(Criterion.Type.ETH_DST);
        VlanIdCriterion vlanId = (VlanIdCriterion) selector
                .getCriterion(Criterion.Type.VLAN_VID);
        if (ethDst == null && vlanId == null) {
            return false;
        }
        return true;
    }

    /**
     * Handles forwarding rules to the IP and MPLS tables.
     *
     * @param fwd the forwarding objective
     * @return A collection of flow rules, or an empty set
     */
    protected Collection<FlowRule> processEthTypeSpecific(ForwardingObjective fwd) {
        TrafficSelector selector = fwd.selector();
        EthTypeCriterion ethType =
                (EthTypeCriterion) selector.getCriterion(Criterion.Type.ETH_TYPE);

        int forTableId = -1;
        TrafficSelector.Builder filteredSelector = DefaultTrafficSelector.builder();
        if (ethType.ethType().toShort() == Ethernet.TYPE_IPV4) {
            filteredSelector.matchEthType(Ethernet.TYPE_IPV4)
                .matchIPDst(((IPCriterion)
                        selector.getCriterion(Criterion.Type.IPV4_DST)).ip());
            forTableId = UNICAST_ROUTING_TABLE;
            log.debug("processing IPv4 specific forwarding objective {} -> next:{}"
                    + " in dev:{}", fwd.id(), fwd.nextId(), deviceId);
        } else {
            filteredSelector
                .matchEthType(Ethernet.MPLS_UNICAST)
                .matchMplsLabel(((MplsCriterion)
                        selector.getCriterion(Criterion.Type.MPLS_LABEL)).label());
            MplsBosCriterion bos = (MplsBosCriterion) selector
                                        .getCriterion(Criterion.Type.MPLS_BOS);
            if (bos != null) {
                filteredSelector.matchMplsBos(bos.mplsBos());
            }
            forTableId = MPLS_TABLE_1;
            log.debug("processing MPLS specific forwarding objective {} -> next:{}"
                    + " in dev {}", fwd.id(), fwd.nextId(), deviceId);
        }

        TrafficTreatment.Builder tb = DefaultTrafficTreatment.builder();
        boolean popMpls = false;
        if (fwd.treatment() != null) {
            for (Instruction i : fwd.treatment().allInstructions()) {
                /*
                 * NOTE: OF-DPA does not support immediate instruction in
                 * L3 unicast and MPLS table.
                 */
                tb.deferred().add(i);
                if (i instanceof L2ModificationInstruction &&
                    ((L2ModificationInstruction) i).subtype() == L2SubType.MPLS_POP) {
                        popMpls = true;
                }
            }
        }

        if (fwd.nextId() != null) {
            if (forTableId == MPLS_TABLE_1 && !popMpls) {
                log.warn("SR CONTINUE case cannot be handled as MPLS ECMP "
                        + "is not implemented in OF-DPA yet. Aborting this flow "
                        + "in this device {}", deviceId);
                // XXX We could convert to forwarding to a single-port, via a
                // MPLS interface, or a MPLS SWAP (with-same) but that would
                // have to be handled in the next-objective. Also the pop-mpls
                // logic used here won't work in non-BoS case.
                fail(fwd, ObjectiveError.FLOWINSTALLATIONFAILED);
                return Collections.emptySet();
            }

            NextGroup next = getGroupForNextObjective(fwd.nextId());
            if (next != null) {
                List<Deque<GroupKey>> gkeys = appKryo.deserialize(next.data());
                // we only need the top level group's key to point the flow to it
                Group group = groupService.getGroup(deviceId, gkeys.get(0).peekFirst());
                if (group == null) {
                    log.warn("Group with key:{} for next-id:{} not found in dev:{}",
                             gkeys.get(0).peekFirst(), fwd.nextId(), deviceId);
                    fail(fwd, ObjectiveError.GROUPMISSING);
                    return Collections.emptySet();
                }
                tb.deferred().group(group.id());
            }
        }
        tb.transition(ACL_TABLE);
        FlowRule.Builder ruleBuilder = DefaultFlowRule.builder()
                .fromApp(fwd.appId())
                .withPriority(fwd.priority())
                .forDevice(deviceId)
                .withSelector(filteredSelector.build())
                .withTreatment(tb.build())
                .forTable(forTableId);

        if (fwd.permanent()) {
            ruleBuilder.makePermanent();
        } else {
            ruleBuilder.makeTemporary(fwd.timeout());
        }

        return Collections.singletonList(ruleBuilder.build());
    }

    /**
     * Handles forwarding rules to the L2 bridging table. Flow actions are not
     * allowed in the bridging table - instead we use L2 Interface group or
     * L2 flood group
     *
     * @param fwd the forwarding objective
     * @return A collection of flow rules, or an empty set
     */
    protected Collection<FlowRule> processEthDstSpecific(ForwardingObjective fwd) {
        List<FlowRule> rules = new ArrayList<>();

        // Build filtered selector
        TrafficSelector selector = fwd.selector();
        EthCriterion ethCriterion = (EthCriterion) selector
                .getCriterion(Criterion.Type.ETH_DST);
        VlanIdCriterion vlanIdCriterion = (VlanIdCriterion) selector
                .getCriterion(Criterion.Type.VLAN_VID);

        if (vlanIdCriterion == null) {
            log.warn("Forwarding objective for bridging requires vlan. Not "
                    + "installing fwd:{} in dev:{}", fwd.id(), deviceId);
            fail(fwd, ObjectiveError.BADPARAMS);
            return Collections.emptySet();
        }

        TrafficSelector.Builder filteredSelectorBuilder =
                DefaultTrafficSelector.builder();
        // Do not match MacAddress for subnet broadcast entry
        if (!ethCriterion.mac().equals(MacAddress.NONE)) {
            filteredSelectorBuilder.matchEthDst(ethCriterion.mac());
            log.debug("processing L2 forwarding objective:{} -> next:{} in dev:{}",
                      fwd.id(), fwd.nextId(), deviceId);
        } else {
            log.debug("processing L2 Broadcast forwarding objective:{} -> next:{} "
                    + "in dev:{} for vlan:{}",
                      fwd.id(), fwd.nextId(), deviceId, vlanIdCriterion.vlanId());
        }
        filteredSelectorBuilder.matchVlanId(vlanIdCriterion.vlanId());
        TrafficSelector filteredSelector = filteredSelectorBuilder.build();

        if (fwd.treatment() != null) {
            log.warn("Ignoring traffic treatment in fwd rule {} meant for L2 table"
                    + "for dev:{}. Expecting only nextId", fwd.id(), deviceId);
        }

        TrafficTreatment.Builder treatmentBuilder = DefaultTrafficTreatment.builder();
        if (fwd.nextId() != null) {
            NextGroup next = getGroupForNextObjective(fwd.nextId());
            if (next != null) {
                List<Deque<GroupKey>> gkeys = appKryo.deserialize(next.data());
                // we only need the top level group's key to point the flow to it
                Group group = groupService.getGroup(deviceId, gkeys.get(0).peekFirst());
                if (group != null) {
                    treatmentBuilder.deferred().group(group.id());
                } else {
                    log.warn("Group with key:{} for next-id:{} not found in dev:{}",
                             gkeys.get(0).peekFirst(), fwd.nextId(), deviceId);
                    fail(fwd, ObjectiveError.GROUPMISSING);
                    return Collections.emptySet();
                }
            }
        }
        treatmentBuilder.immediate().transition(ACL_TABLE);
        TrafficTreatment filteredTreatment = treatmentBuilder.build();

        // Build bridging table entries
        FlowRule.Builder flowRuleBuilder = DefaultFlowRule.builder();
        flowRuleBuilder.fromApp(fwd.appId())
                .withPriority(fwd.priority())
                .forDevice(deviceId)
                .withSelector(filteredSelector)
                .withTreatment(filteredTreatment)
                .forTable(BRIDGING_TABLE);
        if (fwd.permanent()) {
            flowRuleBuilder.makePermanent();
        } else {
            flowRuleBuilder.makeTemporary(fwd.timeout());
        }
        rules.add(flowRuleBuilder.build());
        return rules;
    }

    protected NextGroup getGroupForNextObjective(Integer nextId) {
        NextGroup next = flowObjectiveStore.getNextGroup(nextId);
        if (next != null) {
            List<Deque<GroupKey>> gkeys = appKryo.deserialize(next.data());
            if (gkeys != null && !gkeys.isEmpty()) {
                return next;
            } else {
               log.warn("Empty next group found in FlowObjective store for "
                       + "next-id:{} in dev:{}", nextId, deviceId);
            }
        } else {
            log.warn("next-id {} not found in Flow objective store for dev:{}",
                     nextId, deviceId);
        }
        return null;
    }

    private void pass(Objective obj) {
        if (obj.context().isPresent()) {
            obj.context().get().onSuccess(obj);
        }
    }

    protected void fail(Objective obj, ObjectiveError error) {
        if (obj.context().isPresent()) {
            obj.context().get().onError(obj, error);
        }
    }

    //////////////////////////////////////
    //  Group handling
    //////////////////////////////////////

    private void addGroup(NextObjective nextObjective) {
        switch (nextObjective.type()) {
        case SIMPLE:
            Collection<TrafficTreatment> treatments = nextObjective.next();
            if (treatments.size() != 1) {
                log.error("Next Objectives of type Simple should only have a "
                        + "single Traffic Treatment. Next Objective Id:{}",
                        nextObjective.id());
               fail(nextObjective, ObjectiveError.BADPARAMS);
               return;
            }
            processSimpleNextObjective(nextObjective);
            break;
        case BROADCAST:
            processBroadcastNextObjective(nextObjective);
            break;
        case HASHED:
            processHashedNextObjective(nextObjective);
            break;
        case FAILOVER:
            fail(nextObjective, ObjectiveError.UNSUPPORTED);
            log.warn("Unsupported next objective type {}", nextObjective.type());
            break;
        default:
            fail(nextObjective, ObjectiveError.UNKNOWN);
            log.warn("Unknown next objective type {}", nextObjective.type());
        }
    }

    /**
     * As per the OFDPA 2.0 TTP, packets are sent out of ports by using
     * a chain of groups. The simple Next Objective passed
     * in by the application has to be broken up into a group chain
     * comprising of an L3 Unicast Group that points to an L2 Interface
     * Group which in-turn points to an output port. In some cases, the simple
     * next Objective can just be an L2 interface without the need for chaining.
     *
     * @param nextObj  the nextObjective of type SIMPLE
     */
    private void processSimpleNextObjective(NextObjective nextObj) {
        TrafficTreatment treatment = nextObj.next().iterator().next();
        // determine if plain L2 or L3->L2
        boolean plainL2 = true;
        for (Instruction ins : treatment.allInstructions()) {
            if (ins.type() == Instruction.Type.L2MODIFICATION) {
                L2ModificationInstruction l2ins = (L2ModificationInstruction) ins;
                if (l2ins.subtype() == L2SubType.ETH_DST ||
                        l2ins.subtype() == L2SubType.ETH_SRC) {
                    plainL2 = false;
                    break;
                }
            }
        }

        if (plainL2) {
            createL2InterfaceGroup(nextObj);
            return;
        }

        // break up simple next objective to GroupChain objects
        GroupInfo groupInfo = createL2L3Chain(treatment, nextObj.id(),
                                              nextObj.appId(), false,
                                              nextObj.meta());
        if (groupInfo == null) {
            log.error("Could not process nextObj={} in dev:{}", nextObj.id(), deviceId);
            return;
        }
        // create object for local and distributed storage
        Deque<GroupKey> gkeyChain = new ArrayDeque<>();
        gkeyChain.addFirst(groupInfo.innerGrpDesc.appCookie());
        gkeyChain.addFirst(groupInfo.outerGrpDesc.appCookie());
        OfdpaNextGroup ofdpaGrp = new OfdpaNextGroup(
                                           Collections.singletonList(gkeyChain),
                                           nextObj);

        // store l3groupkey with the ofdpaNextGroup for the nextObjective that depends on it
        updatePendingNextObjective(groupInfo.outerGrpDesc.appCookie(), ofdpaGrp);

        // now we are ready to send the l2 groupDescription (inner), as all the stores
        // that will get async replies have been updated. By waiting to update
        // the stores, we prevent nasty race conditions.
        groupService.addGroup(groupInfo.innerGrpDesc);
    }

    private void updatePendingNextObjective(GroupKey key, OfdpaNextGroup value) {
        List<OfdpaNextGroup> nextList = new CopyOnWriteArrayList<OfdpaNextGroup>();
        nextList.add(value);
        List<OfdpaNextGroup> ret = pendingNextObjectives.asMap()
                .putIfAbsent(key, nextList);
        if (ret != null) {
            ret.add(value);
        }
    }

    private void updatePendingGroups(GroupKey gkey, GroupChainElem gce) {
        Set<GroupChainElem> gceSet = Collections.newSetFromMap(
                                         new ConcurrentHashMap<GroupChainElem, Boolean>());
        gceSet.add(gce);
        Set<GroupChainElem> retval = pendingGroups.putIfAbsent(gkey, gceSet);
        if (retval != null) {
            retval.add(gce);
        }
    }

    /**
     * Creates a simple L2 Interface Group.
     *
     * @param nextObj the next Objective
     */
    private void createL2InterfaceGroup(NextObjective nextObj) {
        // only allowed actions are vlan pop and outport
        TrafficTreatment.Builder ttb = DefaultTrafficTreatment.builder();
        PortNumber portNum = null;
        for (Instruction ins : nextObj.next().iterator().next().allInstructions()) {
            if (ins.type() == Instruction.Type.L2MODIFICATION) {
                L2ModificationInstruction l2ins = (L2ModificationInstruction) ins;
                switch (l2ins.subtype()) {
                case VLAN_POP:
                    ttb.add(l2ins);
                    break;
                default:
                    break;
                }
            } else if (ins.type() == Instruction.Type.OUTPUT) {
                portNum = ((OutputInstruction) ins).port();
                ttb.add(ins);
            } else {
                log.warn("Driver does not handle this type of TrafficTreatment"
                        + " instruction in simple nextObjectives:  {}", ins.type());
            }
        }
        //use the vlanid associated with the port
        VlanId vlanid = port2Vlan.get(portNum);

        if (vlanid == null && nextObj.meta() != null) {
            // use metadata vlan info if available
            Criterion vidCriterion = nextObj.meta().getCriterion(Type.VLAN_VID);
            if (vidCriterion != null) {
                vlanid = ((VlanIdCriterion) vidCriterion).vlanId();
            }
        }

        if (vlanid == null) {
            log.error("Driver cannot process an L2/L3 group chain without "
                    + "egress vlan information for dev: {} port:{}",
                    deviceId, portNum);
            return;
        }

        // assemble information for ofdpa l2interface group
        Integer l2groupId = L2INTERFACEMASK | (vlanid.toShort() << 16) | (int) portNum.toLong();
        // a globally unique groupkey that is different for ports in the same devices
        // but different for the same portnumber on different devices. Also different
        // for the various group-types created out of the same next objective.
        int l2gk = 0x0ffffff & (deviceId.hashCode() << 8 | (int) portNum.toLong());
        final GroupKey l2groupkey = new DefaultGroupKey(appKryo.serialize(l2gk));

        // create group description for the l2interfacegroup
        GroupBucket l2interfaceGroupBucket =
                DefaultGroupBucket.createIndirectGroupBucket(ttb.build());
        GroupDescription l2groupDescription =
                             new DefaultGroupDescription(
                                     deviceId,
                                     GroupDescription.Type.INDIRECT,
                                     new GroupBuckets(Collections.singletonList(
                                                          l2interfaceGroupBucket)),
                                     l2groupkey,
                                     l2groupId,
                                     nextObj.appId());
        log.debug("Trying L2Interface: device:{} gid:{} gkey:{} nextId:{}",
                  deviceId, Integer.toHexString(l2groupId),
                  l2groupkey, nextObj.id());

        // create object for local and distributed storage
        Deque<GroupKey> singleKey = new ArrayDeque<>();
        singleKey.addFirst(l2groupkey);
        OfdpaNextGroup ofdpaGrp = new OfdpaNextGroup(
                                           Collections.singletonList(singleKey),
                                           nextObj);

        // store l2groupkey for the nextObjective that depends on it
        updatePendingNextObjective(l2groupkey, ofdpaGrp);
        // send the group description to the group service
        groupService.addGroup(l2groupDescription);
    }

    /**
     * Creates one of two possible group-chains from the treatment
     * passed in. Depending on the MPLS boolean, this method either creates
     * an L3Unicast Group --> L2Interface Group, if mpls is false;
     * or MPLSInterface Group --> L2Interface Group, if mpls is true;
     * The returned 'inner' group description is always the L2 Interface group.
     *
     * @param treatment that needs to be broken up to create the group chain
     * @param nextId of the next objective that needs this group chain
     * @param appId of the application that sent this next objective
     * @param mpls determines if L3Unicast or MPLSInterface group is created
     * @param meta metadata passed in by the application as part of the nextObjective
     * @return GroupInfo containing the GroupDescription of the
     *         L2Interface group(inner) and the GroupDescription of the (outer)
     *         L3Unicast/MPLSInterface group. May return null if there is an
     *         error in processing the chain
     */
    private GroupInfo createL2L3Chain(TrafficTreatment treatment, int nextId,
                                      ApplicationId appId, boolean mpls,
                                      TrafficSelector meta) {
        // for the l2interface group, get vlan and port info
        // for the outer group, get the src/dst mac, and vlan info
        TrafficTreatment.Builder outerTtb = DefaultTrafficTreatment.builder();
        TrafficTreatment.Builder innerTtb = DefaultTrafficTreatment.builder();
        VlanId vlanid = null;
        long portNum = 0;
        boolean setVlan = false, popVlan = false;
        for (Instruction ins : treatment.allInstructions()) {
            if (ins.type() == Instruction.Type.L2MODIFICATION) {
                L2ModificationInstruction l2ins = (L2ModificationInstruction) ins;
                switch (l2ins.subtype()) {
                case ETH_DST:
                    outerTtb.setEthDst(((ModEtherInstruction) l2ins).mac());
                    break;
                case ETH_SRC:
                    outerTtb.setEthSrc(((ModEtherInstruction) l2ins).mac());
                    break;
                case VLAN_ID:
                    vlanid = ((ModVlanIdInstruction) l2ins).vlanId();
                    outerTtb.setVlanId(vlanid);
                    setVlan = true;
                    break;
                case VLAN_POP:
                    innerTtb.popVlan();
                    popVlan = true;
                    break;
                case DEC_MPLS_TTL:
                case MPLS_LABEL:
                case MPLS_POP:
                case MPLS_PUSH:
                case VLAN_PCP:
                case VLAN_PUSH:
                default:
                    break;
                }
            } else if (ins.type() == Instruction.Type.OUTPUT) {
                portNum = ((OutputInstruction) ins).port().toLong();
                innerTtb.add(ins);
            } else {
                log.warn("Driver does not handle this type of TrafficTreatment"
                        + " instruction in nextObjectives:  {}", ins.type());
            }
        }

        if (vlanid == null && meta != null) {
            // use metadata if available
            Criterion vidCriterion = meta.getCriterion(Type.VLAN_VID);
            if (vidCriterion != null) {
                vlanid = ((VlanIdCriterion) vidCriterion).vlanId();
            }
            // if vlan is not set, use the vlan in metadata for outerTtb
            if (vlanid != null && !setVlan) {
                outerTtb.setVlanId(vlanid);
            }
        }

        if (vlanid == null) {
            log.error("Driver cannot process an L2/L3 group chain without "
                    + "egress vlan information for dev: {} port:{}",
                    deviceId, portNum);
            return null;
        }

        if (!setVlan && !popVlan) {
            // untagged outgoing port
            TrafficTreatment.Builder temp = DefaultTrafficTreatment.builder();
            temp.popVlan();
            innerTtb.build().allInstructions().forEach(i -> temp.add(i));
            innerTtb = temp;
        }

        // assemble information for ofdpa l2interface group
        Integer l2groupId = L2INTERFACEMASK | (vlanid.toShort() << 16) | (int) portNum;
        // a globally unique groupkey that is different for ports in the same devices
        // but different for the same portnumber on different devices. Also different
        // for the various group-types created out of the same next objective.
        int l2gk = 0x0ffffff & (deviceId.hashCode() << 8 | (int) portNum);
        final GroupKey l2groupkey = new DefaultGroupKey(appKryo.serialize(l2gk));

        // assemble information for outer group
        GroupDescription outerGrpDesc = null;
        if (mpls) {
            // outer group is MPLSInteface
            Integer mplsgroupId = MPLSINTERFACEMASK | (int) portNum;
            // using mplsinterfacemask in groupkey to differentiate from l2interface
            int mplsgk = MPLSINTERFACEMASK | (0x0ffffff & (deviceId.hashCode() << 8 | (int) portNum));
            final GroupKey mplsgroupkey = new DefaultGroupKey(appKryo.serialize(mplsgk));
            outerTtb.group(new DefaultGroupId(l2groupId));
            // create the mpls-interface group description to wait for the
            // l2 interface group to be processed
            GroupBucket mplsinterfaceGroupBucket =
                    DefaultGroupBucket.createIndirectGroupBucket(outerTtb.build());
            outerGrpDesc = new DefaultGroupDescription(
                                   deviceId,
                                   GroupDescription.Type.INDIRECT,
                                   new GroupBuckets(Collections.singletonList(
                                                        mplsinterfaceGroupBucket)),
                                   mplsgroupkey,
                                   mplsgroupId,
                                   appId);
            log.debug("Trying MPLS-Interface: device:{} gid:{} gkey:{} nextid:{}",
                      deviceId, Integer.toHexString(mplsgroupId),
                      mplsgroupkey, nextId);
        } else {
            // outer group is L3Unicast
            Integer l3groupId = L3UNICASTMASK | (int) portNum;
            int l3gk = L3UNICASTMASK | (0x0ffffff & (deviceId.hashCode() << 8 | (int) portNum));
            final GroupKey l3groupkey = new DefaultGroupKey(appKryo.serialize(l3gk));
            outerTtb.group(new DefaultGroupId(l2groupId));
            // create the l3unicast group description to wait for the
            // l2 interface group to be processed
            GroupBucket l3unicastGroupBucket =
                    DefaultGroupBucket.createIndirectGroupBucket(outerTtb.build());
            outerGrpDesc = new DefaultGroupDescription(
                                   deviceId,
                                   GroupDescription.Type.INDIRECT,
                                   new GroupBuckets(Collections.singletonList(
                                                        l3unicastGroupBucket)),
                                   l3groupkey,
                                   l3groupId,
                                   appId);
            log.debug("Trying L3Unicast: device:{} gid:{} gkey:{} nextid:{}",
                      deviceId, Integer.toHexString(l3groupId),
                      l3groupkey, nextId);
        }

        // store l2groupkey with the groupChainElem for the outer-group that depends on it
        GroupChainElem gce = new GroupChainElem(outerGrpDesc, 1, false);
        updatePendingGroups(l2groupkey, gce);

        // create group description for the inner l2interfacegroup
        GroupBucket l2interfaceGroupBucket =
                DefaultGroupBucket.createIndirectGroupBucket(innerTtb.build());
        GroupDescription l2groupDescription =
                             new DefaultGroupDescription(
                                     deviceId,
                                     GroupDescription.Type.INDIRECT,
                                     new GroupBuckets(Collections.singletonList(
                                                          l2interfaceGroupBucket)),
                                     l2groupkey,
                                     l2groupId,
                                     appId);
        log.debug("Trying L2Interface: device:{} gid:{} gkey:{} nextId:{}",
                  deviceId, Integer.toHexString(l2groupId),
                  l2groupkey, nextId);
        return new GroupInfo(l2groupDescription, outerGrpDesc);

    }

    /**
     * As per the OFDPA 2.0 TTP, packets are sent out of ports by using
     * a chain of groups. The broadcast Next Objective passed in by the application
     * has to be broken up into a group chain comprising of an
     * L2 Flood group whose buckets point to L2 Interface groups.
     *
     * @param nextObj  the nextObjective of type BROADCAST
     */
    private void processBroadcastNextObjective(NextObjective nextObj) {
        // break up broadcast next objective to multiple groups
        Collection<TrafficTreatment> buckets = nextObj.next();

        // each treatment is converted to an L2 interface group
        VlanId vlanid = null;
        List<GroupDescription> l2interfaceGroupDescs = new ArrayList<>();
        List<Deque<GroupKey>> allGroupKeys = new ArrayList<>();
        for (TrafficTreatment treatment : buckets) {
            TrafficTreatment.Builder newTreatment = DefaultTrafficTreatment.builder();
            PortNumber portNum = null;
            // ensure that the only allowed treatments are pop-vlan and output
            for (Instruction ins : treatment.allInstructions()) {
                if (ins.type() == Instruction.Type.L2MODIFICATION) {
                    L2ModificationInstruction l2ins = (L2ModificationInstruction) ins;
                    switch (l2ins.subtype()) {
                    case VLAN_POP:
                        newTreatment.add(l2ins);
                        break;
                    default:
                        log.debug("action {} not permitted for broadcast nextObj",
                                  l2ins.subtype());
                        break;
                    }
                } else if (ins.type() == Instruction.Type.OUTPUT) {
                    portNum = ((OutputInstruction) ins).port();
                    newTreatment.add(ins);
                } else {
                    log.debug("TrafficTreatment of type {} not permitted in "
                            + " broadcast nextObjective", ins.type());
                }
            }

            // also ensure that all ports are in the same vlan
            // XXX maybe HA issue here?
            VlanId thisvlanid = port2Vlan.get(portNum);
            if (vlanid == null) {
                vlanid = thisvlanid;
            } else {
                if (!vlanid.equals(thisvlanid)) {
                    log.error("Driver requires all ports in a broadcast nextObj "
                            + "to be in the same vlan. Different vlans found "
                            + "{} and {}. Aborting group creation", vlanid, thisvlanid);
                    return;
                }
            }

            // assemble info for l2 interface group
            int l2gk = 0x0ffffff & (deviceId.hashCode() << 8 | (int) portNum.toLong());
            final GroupKey l2groupkey = new DefaultGroupKey(appKryo.serialize(l2gk));
            Integer l2groupId = L2INTERFACEMASK | (vlanid.toShort() << 16) |
                                    (int) portNum.toLong();
            GroupBucket l2interfaceGroupBucket =
                    DefaultGroupBucket.createIndirectGroupBucket(newTreatment.build());
            GroupDescription l2interfaceGroupDescription =
                        new DefaultGroupDescription(
                                                    deviceId,
                            GroupDescription.Type.INDIRECT,
                            new GroupBuckets(Collections.singletonList(
                                                 l2interfaceGroupBucket)),
                            l2groupkey,
                            l2groupId,
                            nextObj.appId());
            log.debug("Trying L2-Interface: device:{} gid:{} gkey:{} nextid:{}",
                      deviceId, Integer.toHexString(l2groupId),
                      l2groupkey, nextObj.id());

            Deque<GroupKey> gkeyChain = new ArrayDeque<>();
            gkeyChain.addFirst(l2groupkey);

            // store the info needed to create this group
            l2interfaceGroupDescs.add(l2interfaceGroupDescription);
            allGroupKeys.add(gkeyChain);
        }

        // assemble info for l2 flood group
        Integer l2floodgroupId = L2FLOODMASK | (vlanid.toShort() << 16) | nextObj.id();
        int l2floodgk = L2FLOODMASK | nextObj.id() << 12;
        final GroupKey l2floodgroupkey = new DefaultGroupKey(appKryo.serialize(l2floodgk));
        // collection of group buckets pointing to all the l2 interface groups
        List<GroupBucket> l2floodBuckets = new ArrayList<>();
        for (GroupDescription l2intGrpDesc : l2interfaceGroupDescs) {
            TrafficTreatment.Builder ttb = DefaultTrafficTreatment.builder();
            ttb.group(new DefaultGroupId(l2intGrpDesc.givenGroupId()));
            GroupBucket abucket = DefaultGroupBucket.createAllGroupBucket(ttb.build());
            l2floodBuckets.add(abucket);
        }
        // create the l2flood group-description to wait for all the
        // l2interface groups to be processed
        GroupDescription l2floodGroupDescription =
                                new DefaultGroupDescription(
                                        deviceId,
                                        GroupDescription.Type.ALL,
                                        new GroupBuckets(l2floodBuckets),
                                        l2floodgroupkey,
                                        l2floodgroupId,
                                        nextObj.appId());
        GroupChainElem gce = new GroupChainElem(l2floodGroupDescription,
                                                l2interfaceGroupDescs.size(),
                                                false);
        log.debug("Trying L2-Flood: device:{} gid:{} gkey:{} nextid:{}",
                  deviceId, Integer.toHexString(l2floodgroupId),
                  l2floodgroupkey, nextObj.id());

        // create objects for local and distributed storage
        allGroupKeys.forEach(gkeyChain -> gkeyChain.addFirst(l2floodgroupkey));
        OfdpaNextGroup ofdpaGrp = new OfdpaNextGroup(allGroupKeys, nextObj);

        // store l2floodgroupkey with the ofdpaGroupChain for the nextObjective
        // that depends on it
        updatePendingNextObjective(l2floodgroupkey, ofdpaGrp);

        for (GroupDescription l2intGrpDesc : l2interfaceGroupDescs) {
            // store all l2groupkeys with the groupChainElem for the l2floodgroup
            // that depends on it
            updatePendingGroups(l2intGrpDesc.appCookie(), gce);
            // send groups for all l2 interface groups
            groupService.addGroup(l2intGrpDesc);
        }
    }

    /**
     * Utility class for moving group information around.
     *
     */
    private class GroupInfo {
        private GroupDescription innerGrpDesc;
        private GroupDescription outerGrpDesc;

        GroupInfo(GroupDescription innerGrpDesc, GroupDescription outerGrpDesc) {
            this.innerGrpDesc = innerGrpDesc;
            this.outerGrpDesc = outerGrpDesc;
        }
    }

    /**
     * As per the OFDPA 2.0 TTP, packets are sent out of ports by using
     * a chain of groups. The hashed Next Objective passed in by the application
     * has to be broken up into a group chain comprising of an
     * L3 ECMP group as the top level group. Buckets of this group can point
     * to a variety of groups in a group chain, depending on the whether
     * MPLS labels are being pushed or not.
     * <p>
     * NOTE: We do not create MPLS ECMP groups as they are unimplemented in
     *       OF-DPA 2.0 (even though it is in the spec). Therefore we do not
     *       check the nextObjective meta to see what is matching before being
     *       sent to this nextObjective.
     *
     * @param nextObj  the nextObjective of type HASHED
     */
    private void processHashedNextObjective(NextObjective nextObj) {
        // storage for all group keys in the chain of groups created
        List<Deque<GroupKey>> allGroupKeys = new ArrayList<>();
        List<GroupInfo> unsentGroups = new ArrayList<>();
        createHashBucketChains(nextObj, allGroupKeys, unsentGroups);

        // now we can create the outermost L3 ECMP group
        List<GroupBucket> l3ecmpGroupBuckets = new ArrayList<>();
        for (GroupInfo gi : unsentGroups) {
            // create ECMP bucket to point to the outer group
            TrafficTreatment.Builder ttb = DefaultTrafficTreatment.builder();
            ttb.group(new DefaultGroupId(gi.outerGrpDesc.givenGroupId()));
            GroupBucket sbucket = DefaultGroupBucket
                    .createSelectGroupBucket(ttb.build());
            l3ecmpGroupBuckets.add(sbucket);
        }
        int l3ecmpGroupId = L3ECMPMASK | nextObj.id() << 12;
        GroupKey l3ecmpGroupKey = new DefaultGroupKey(appKryo.serialize(l3ecmpGroupId));
        GroupDescription l3ecmpGroupDesc =
                new DefaultGroupDescription(
                        deviceId,
                        GroupDescription.Type.SELECT,
                        new GroupBuckets(l3ecmpGroupBuckets),
                        l3ecmpGroupKey,
                        l3ecmpGroupId,
                        nextObj.appId());
        GroupChainElem l3ecmpGce = new GroupChainElem(l3ecmpGroupDesc,
                                                      l3ecmpGroupBuckets.size(),
                                                      false);

        // create objects for local and distributed storage
        allGroupKeys.forEach(gkeyChain -> gkeyChain.addFirst(l3ecmpGroupKey));
        OfdpaNextGroup ofdpaGrp = new OfdpaNextGroup(allGroupKeys, nextObj);

        // store l3ecmpGroupKey with the ofdpaGroupChain for the nextObjective
        // that depends on it
        updatePendingNextObjective(l3ecmpGroupKey, ofdpaGrp);

        log.debug("Trying L3ECMP: device:{} gid:{} gkey:{} nextId:{}",
                  deviceId, Integer.toHexString(l3ecmpGroupId),
                  l3ecmpGroupKey, nextObj.id());
        // finally we are ready to send the innermost groups
        for (GroupInfo gi : unsentGroups) {
            log.debug("Sending innermost group {} in group chain on device {} ",
                      Integer.toHexString(gi.innerGrpDesc.givenGroupId()), deviceId);
            updatePendingGroups(gi.outerGrpDesc.appCookie(), l3ecmpGce);
            groupService.addGroup(gi.innerGrpDesc);
        }

    }

    /**
     * Creates group chains for all buckets in a hashed group, and stores the
     * GroupInfos and GroupKeys for all the groups in the lists passed in, which
     * should be empty.
     * <p>
     * Does not create the top level ECMP group. Does not actually send the
     * groups to the groupService.
     *
     * @param nextObj  the Next Objective with buckets that need to be converted
     *                  to group chains
     * @param allGroupKeys  a list to store groupKey for each bucket-group-chain
     * @param unsentGroups  a list to store GroupInfo for each bucket-group-chain
     */
    private void createHashBucketChains(NextObjective nextObj,
                                        List<Deque<GroupKey>> allGroupKeys,
                                        List<GroupInfo> unsentGroups) {
        // break up hashed next objective to multiple groups
        Collection<TrafficTreatment> buckets = nextObj.next();

        for (TrafficTreatment bucket : buckets) {
            //figure out how many labels are pushed in each bucket
            int labelsPushed = 0;
            MplsLabel innermostLabel = null;
            for (Instruction ins : bucket.allInstructions()) {
                if (ins.type() == Instruction.Type.L2MODIFICATION) {
                    L2ModificationInstruction l2ins = (L2ModificationInstruction) ins;
                    if (l2ins.subtype() == L2SubType.MPLS_PUSH) {
                        labelsPushed++;
                    }
                    if (l2ins.subtype() == L2SubType.MPLS_LABEL) {
                        if (innermostLabel == null) {
                            innermostLabel = ((ModMplsLabelInstruction) l2ins).mplsLabel();
                        }
                    }
                }
            }

            Deque<GroupKey> gkeyChain = new ArrayDeque<>();
            // XXX we only deal with 0 and 1 label push right now
            if (labelsPushed == 0) {
                GroupInfo nolabelGroupInfo = createL2L3Chain(bucket, nextObj.id(),
                                                             nextObj.appId(), false,
                                                             nextObj.meta());
                if (nolabelGroupInfo == null) {
                    log.error("Could not process nextObj={} in dev:{}",
                              nextObj.id(), deviceId);
                    return;
                }
                gkeyChain.addFirst(nolabelGroupInfo.innerGrpDesc.appCookie());
                gkeyChain.addFirst(nolabelGroupInfo.outerGrpDesc.appCookie());

                // we can't send the inner group description yet, as we have to
                // create the dependent ECMP group first. So we store..
                unsentGroups.add(nolabelGroupInfo);

            } else if (labelsPushed == 1) {
                GroupInfo onelabelGroupInfo = createL2L3Chain(bucket, nextObj.id(),
                                                              nextObj.appId(), true,
                                                              nextObj.meta());
                if (onelabelGroupInfo == null) {
                    log.error("Could not process nextObj={} in dev:{}",
                              nextObj.id(), deviceId);
                    return;
                }
                // we need to add another group to this chain - the L3VPN group
                TrafficTreatment.Builder l3vpnTtb = DefaultTrafficTreatment.builder();
                l3vpnTtb.pushMpls()
                            .setMpls(innermostLabel)
                            .setMplsBos(true)
                            .copyTtlOut()
                            .group(new DefaultGroupId(
                                 onelabelGroupInfo.outerGrpDesc.givenGroupId()));
                GroupBucket l3vpnGrpBkt  =
                        DefaultGroupBucket.createIndirectGroupBucket(l3vpnTtb.build());
                int l3vpngroupId = L3VPNMASK | l3vpnindex.incrementAndGet();
                int l3vpngk = L3VPNMASK | nextObj.id() << 12 | l3vpnindex.get();
                GroupKey l3vpngroupkey = new DefaultGroupKey(appKryo.serialize(l3vpngk));
                GroupDescription l3vpnGroupDesc =
                        new DefaultGroupDescription(
                                deviceId,
                                GroupDescription.Type.INDIRECT,
                                new GroupBuckets(Collections.singletonList(
                                                     l3vpnGrpBkt)),
                                l3vpngroupkey,
                                l3vpngroupId,
                                nextObj.appId());
                GroupChainElem l3vpnGce = new GroupChainElem(l3vpnGroupDesc, 1, false);
                updatePendingGroups(onelabelGroupInfo.outerGrpDesc.appCookie(), l3vpnGce);

                gkeyChain.addFirst(onelabelGroupInfo.innerGrpDesc.appCookie());
                gkeyChain.addFirst(onelabelGroupInfo.outerGrpDesc.appCookie());
                gkeyChain.addFirst(l3vpngroupkey);

                //now we can replace the outerGrpDesc with the one we just created
                onelabelGroupInfo.outerGrpDesc = l3vpnGroupDesc;

                // we can't send the innermost group yet, as we have to create
                // the dependent ECMP group first. So we store ...
                unsentGroups.add(onelabelGroupInfo);

                log.debug("Trying L3VPN: device:{} gid:{} gkey:{} nextId:{}",
                          deviceId, Integer.toHexString(l3vpngroupId),
                          l3vpngroupkey, nextObj.id());

            } else {
                log.warn("Driver currently does not handle more than 1 MPLS "
                        + "labels. Not processing nextObjective {}", nextObj.id());
                return;
            }

            // all groups in this chain
            allGroupKeys.add(gkeyChain);
        }
    }

    /**
     *  Adds a bucket to the top level group of a group-chain, and creates the chain.
     *
     * @param nextObjective the next group to add a bucket to
     * @param next the representation of the existing group-chain for this next objective
     */
    private void addBucketToGroup(NextObjective nextObjective, NextGroup next) {
        if (nextObjective.type() != NextObjective.Type.HASHED) {
            log.warn("AddBuckets not applied to nextType:{} in dev:{} for next:{}",
                     nextObjective.type(), deviceId, nextObjective.id());
            return;
        }
        if (nextObjective.next().size() > 1) {
            log.warn("Only one bucket can be added at a time");
            return;
        }
        // storage for all group keys in the chain of groups created
        List<Deque<GroupKey>> allGroupKeys = new ArrayList<>();
        List<GroupInfo> unsentGroups = new ArrayList<>();
        createHashBucketChains(nextObjective, allGroupKeys, unsentGroups);

        // now we can create the outermost L3 ECMP group bucket to add
        GroupInfo gi = unsentGroups.get(0); // only one bucket, so only one group-chain
        TrafficTreatment.Builder ttb = DefaultTrafficTreatment.builder();
        ttb.group(new DefaultGroupId(gi.outerGrpDesc.givenGroupId()));
        GroupBucket sbucket = DefaultGroupBucket.createSelectGroupBucket(ttb.build());

        // recreate the original L3 ECMP group id and description
        int l3ecmpGroupId = L3ECMPMASK | nextObjective.id() << 12;
        GroupKey l3ecmpGroupKey = new DefaultGroupKey(appKryo.serialize(l3ecmpGroupId));

        // Although GroupDescriptions are not necessary for adding buckets to
        // existing groups, we use one in the GroupChainElem. When the latter is
        // processed, the info will be extracted for the bucketAdd call to groupService
        GroupDescription l3ecmpGroupDesc =
                new DefaultGroupDescription(
                        deviceId,
                        GroupDescription.Type.SELECT,
                        new GroupBuckets(Collections.singletonList(sbucket)),
                        l3ecmpGroupKey,
                        l3ecmpGroupId,
                        nextObjective.appId());
        GroupChainElem l3ecmpGce = new GroupChainElem(l3ecmpGroupDesc, 1, true);

        // update original NextGroup with new bucket-chain
        // don't need to update pendingNextObjectives -- group already exists
        Deque<GroupKey> newBucketChain = allGroupKeys.get(0);
        newBucketChain.addFirst(l3ecmpGroupKey);
        List<Deque<GroupKey>> allOriginalKeys = appKryo.deserialize(next.data());
        allOriginalKeys.add(newBucketChain);
        flowObjectiveStore.putNextGroup(nextObjective.id(),
                                        new OfdpaNextGroup(allOriginalKeys, nextObjective));

        log.debug("Adding to L3ECMP: device:{} gid:{} gkey:{} nextId:{}",
                  deviceId, Integer.toHexString(l3ecmpGroupId),
                  l3ecmpGroupKey, nextObjective.id());
        // send the innermost group
        log.debug("Sending innermost group {} in group chain on device {} ",
                  Integer.toHexString(gi.innerGrpDesc.givenGroupId()), deviceId);
        updatePendingGroups(gi.outerGrpDesc.appCookie(), l3ecmpGce);
        groupService.addGroup(gi.innerGrpDesc);

    }

    /**
     * Removes the bucket in the top level group of a possible group-chain. Does
     * not remove the groups in a group-chain pointed to by this bucket, as they
     * may be in use (referenced by other groups) elsewhere.
     *
     * @param nextObjective the next group to remove a bucket from
     * @param next the representation of the existing group-chain for this next objective
     */
    private void removeBucketFromGroup(NextObjective nextObjective, NextGroup next) {
        if (nextObjective.type() != NextObjective.Type.HASHED) {
            log.warn("RemoveBuckets not applied to nextType:{} in dev:{} for next:{}",
                     nextObjective.type(), deviceId, nextObjective.id());
            return;
        }
        Collection<TrafficTreatment> treatments = nextObjective.next();
        TrafficTreatment treatment = treatments.iterator().next();
        // find the bucket to remove by noting the outport, and figuring out the
        // top-level group in the group-chain that indirectly references the port
        PortNumber outport = null;
        for (Instruction ins : treatment.allInstructions()) {
            if (ins instanceof OutputInstruction) {
                outport = ((OutputInstruction) ins).port();
                break;
            }
        }
        if (outport == null) {
            log.error("next objective {} has no outport", nextObjective.id());
            return;
        }

        List<Deque<GroupKey>> allgkeys = appKryo.deserialize(next.data());
        Deque<GroupKey> foundChain = null;
        int index = 0;
        for (Deque<GroupKey> gkeys : allgkeys) {
            GroupKey groupWithPort = gkeys.peekLast();
            Group group = groupService.getGroup(deviceId, groupWithPort);
            if (group == null) {
                log.warn("Inconsistent group chain");
                continue;
            }
            // last group in group chain should have a single bucket pointing to port
            List<Instruction> lastIns = group.buckets().buckets().iterator()
                                            .next().treatment().allInstructions();
            for (Instruction i : lastIns) {
                if (i instanceof OutputInstruction) {
                    PortNumber lastport = ((OutputInstruction) i).port();
                    if (lastport.equals(outport)) {
                        foundChain = gkeys;
                        break;
                    }
                }
            }
            if (foundChain != null) {
                break;
            }
            index++;
        }
        if (foundChain != null) {
            //first groupkey is the one we want to modify
            GroupKey modGroupKey = foundChain.peekFirst();
            Group modGroup = groupService.getGroup(deviceId, modGroupKey);
            //second groupkey is the one we wish to remove the reference to
            GroupKey pointedGroupKey = null;
            int i = 0;
            for (GroupKey gk : foundChain) {
                if (i++ == 1) {
                    pointedGroupKey = gk;
                    break;
                }
            }
            Group pointedGroup = groupService.getGroup(deviceId, pointedGroupKey);
            GroupBucket bucket = DefaultGroupBucket.createSelectGroupBucket(
                                     DefaultTrafficTreatment.builder()
                                         .group(pointedGroup.id())
                                         .build());
            GroupBuckets removeBuckets = new GroupBuckets(Collections
                                                          .singletonList(bucket));
            log.debug("Removing buckets from group id {} for next id {} in device {}",
                      modGroup.id(), nextObjective.id(), deviceId);
            groupService.removeBucketsFromGroup(deviceId, modGroupKey,
                                                removeBuckets, modGroupKey,
                                                nextObjective.appId());
            //update store
            allgkeys.remove(index);
            flowObjectiveStore.putNextGroup(nextObjective.id(),
                                            new OfdpaNextGroup(allgkeys, nextObjective));
        } else {
            log.warn("Could not find appropriate group-chain for removing bucket"
                    + " for next id {} in dev:{}", nextObjective.id(), deviceId);
        }
    }

    /**
     * Removes all groups in multiple possible group-chains that represent the next
     * objective.
     *
     * @param nextObjective the next objective to remove
     * @param next the NextGroup that represents the existing group-chain for
     *             this next objective
     */
    private void removeGroup(NextObjective nextObjective, NextGroup next) {
        List<Deque<GroupKey>> allgkeys = appKryo.deserialize(next.data());
        allgkeys.forEach(groupChain -> {
            groupChain.forEach(groupKey ->
            groupService.removeGroup(deviceId, groupKey, nextObjective.appId()));
        });
        flowObjectiveStore.removeNextGroup(nextObjective.id());
    }

    /**
     * Processes next element of a group chain. Assumption is that if this
     * group points to another group, the latter has already been created
     * and this driver has received notification for it. A second assumption is
     * that if there is another group waiting for this group then the appropriate
     * stores already have the information to act upon the notification for the
     * creation of this group.
     * <p>
     * The processing of the GroupChainElement depends on the number of groups
     * this element is waiting on. For all group types other than SIMPLE, a
     * GroupChainElement could be waiting on multiple groups.
     *
     * @param gce the group chain element to be processed next
     */
    private void processGroupChain(GroupChainElem gce) {
        int waitOnGroups = gce.decrementAndGetGroupsWaitedOn();
        if (waitOnGroups != 0) {
            log.debug("GCE: {} not ready to be processed", gce);
            return;
        }
        log.debug("GCE: {} ready to be processed", gce);
        if (gce.addBucketToGroup) {
            groupService.addBucketsToGroup(gce.groupDescription.deviceId(),
                                           gce.groupDescription.appCookie(),
                                           gce.groupDescription.buckets(),
                                           gce.groupDescription.appCookie(),
                                           gce.groupDescription.appId());
        } else {
            groupService.addGroup(gce.groupDescription);
        }
    }

    private class GroupChecker implements Runnable {
        @Override
        public void run() {
            Set<GroupKey> keys = pendingGroups.keySet().stream()
                    .filter(key -> groupService.getGroup(deviceId, key) != null)
                    .collect(Collectors.toSet());
            Set<GroupKey> otherkeys = pendingNextObjectives.asMap().keySet().stream()
                    .filter(otherkey -> groupService.getGroup(deviceId, otherkey) != null)
                    .collect(Collectors.toSet());
            keys.addAll(otherkeys);

            keys.stream().forEach(key ->
                processPendingGroupsOrNextObjectives(key, false));
        }
    }

    private void processPendingGroupsOrNextObjectives(GroupKey key, boolean added) {
        //first check for group chain
        Set<GroupChainElem> gceSet = pendingGroups.remove(key);
        if (gceSet != null) {
            for (GroupChainElem gce : gceSet) {
                log.info("Group service {} group key {} in device {}. "
                        + "Processing next group in group chain with group id {}",
                        (added) ? "ADDED" : "processed",
                        key, deviceId,
                        Integer.toHexString(gce.groupDescription.givenGroupId()));
                processGroupChain(gce);
            }
        } else {
            // otherwise chain complete - check for waiting nextObjectives
            List<OfdpaNextGroup> nextGrpList = pendingNextObjectives.getIfPresent(key);
            if (nextGrpList != null) {
                pendingNextObjectives.invalidate(key);
                nextGrpList.forEach(nextGrp -> {
                    log.info("Group service {} group key {} in device:{}. "
                            + "Done implementing next objective: {} <<-->> gid:{}",
                            (added) ? "ADDED" : "processed",
                            key, deviceId, nextGrp.nextObjective().id(),
                            Integer.toHexString(groupService.getGroup(deviceId, key)
                                                .givenGroupId()));
                    pass(nextGrp.nextObjective());
                    flowObjectiveStore.putNextGroup(nextGrp.nextObjective().id(), nextGrp);
                    // check if addBuckets waiting for this completion
                    NextObjective pendBkt = pendingBuckets
                                                .remove(nextGrp.nextObjective().id());
                    if (pendBkt != null) {
                        addBucketToGroup(pendBkt, nextGrp);
                    }
                });
            }
        }
    }

    private class InnerGroupListener implements GroupListener {
        @Override
        public void event(GroupEvent event) {
            log.trace("received group event of type {}", event.type());
            if (event.type() == GroupEvent.Type.GROUP_ADDED) {
                GroupKey key = event.subject().appCookie();
                processPendingGroupsOrNextObjectives(key, true);
            }
        }
    }

    /**
     * Represents an entire group-chain that implements a Next-Objective from
     * the application. The objective is represented as a list of deques, where
     * each deque is a separate chain of groups.
     * <p>
     * For example, an ECMP group with 3 buckets, where each bucket points to
     * a group chain of L3 Unicast and L2 interface groups will look like this:
     * <ul>
     * <li>List[0] is a Deque of GroupKeyECMP(first)-GroupKeyL3(middle)-GroupKeyL2(last)
     * <li>List[1] is a Deque of GroupKeyECMP(first)-GroupKeyL3(middle)-GroupKeyL2(last)
     * <li>List[2] is a Deque of GroupKeyECMP(first)-GroupKeyL3(middle)-GroupKeyL2(last)
     * </ul>
     * where the first element of each deque is the same, representing the
     * top level ECMP group, while every other element represents a unique groupKey.
     * <p>
     * Also includes information about the next objective that
     * resulted in this group-chain.
     *
     */
    private class OfdpaNextGroup implements NextGroup {
        private final NextObjective nextObj;
        private final List<Deque<GroupKey>> gkeys;

        public OfdpaNextGroup(List<Deque<GroupKey>> gkeys, NextObjective nextObj) {
            this.gkeys = gkeys;
            this.nextObj = nextObj;
        }

        @SuppressWarnings("unused")
        public List<Deque<GroupKey>> groupKey() {
            return gkeys;
        }

        public NextObjective nextObjective() {
            return nextObj;
        }

        @Override
        public byte[] data() {
            return appKryo.serialize(gkeys);
        }

    }

    /**
     * Represents a group element that is part of a chain of groups.
     * Stores enough information to create a Group Description to add the group
     * to the switch by requesting the Group Service. Objects instantiating this
     * class are meant to be temporary and live as long as it is needed to wait for
     * preceding groups in the group chain to be created.
     */
    private class GroupChainElem {
        private GroupDescription groupDescription;
        private AtomicInteger waitOnGroups;
        private boolean addBucketToGroup;

        GroupChainElem(GroupDescription groupDescription, int waitOnGroups,
                       boolean addBucketToGroup) {
            this.groupDescription = groupDescription;
            this.waitOnGroups = new AtomicInteger(waitOnGroups);
            this.addBucketToGroup = addBucketToGroup;
        }

        /**
         * This methods atomically decrements the counter for the number of
         * groups this GroupChainElement is waiting on, for notifications from
         * the Group Service. When this method returns a value of 0, this
         * GroupChainElement is ready to be processed.
         *
         * @return integer indication of the number of notifications being waited on
         */
        int decrementAndGetGroupsWaitedOn() {
            return waitOnGroups.decrementAndGet();
        }

        @Override
        public String toString() {
            return (Integer.toHexString(groupDescription.givenGroupId()) +
                    " groupKey: " + groupDescription.appCookie() +
                    " waiting-on-groups: " + waitOnGroups.get() +
                    " addBucketToGroup: " + addBucketToGroup +
                    " device: " + deviceId);
        }
    }

}