/*
 * Copyright 2017-present Open Networking Foundation
 *
 * 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.t3.impl;

import com.google.common.base.Preconditions;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.Lists;
import com.google.common.collect.Sets;
import org.apache.commons.lang.StringUtils;
import org.apache.commons.lang3.tuple.Pair;
import org.onlab.packet.IpAddress;
import org.onlab.packet.VlanId;
import org.onosproject.cluster.NodeId;
import org.onosproject.net.ConnectPoint;
import org.onosproject.net.DeviceId;
import org.onosproject.net.Host;
import org.onosproject.net.HostId;
import org.onosproject.net.Link;
import org.onosproject.net.Port;
import org.onosproject.net.PortNumber;
import org.onosproject.net.config.ConfigException;
import org.onosproject.net.config.basics.InterfaceConfig;
import org.onosproject.net.flow.DefaultTrafficSelector;
import org.onosproject.net.flow.FlowEntry;
import org.onosproject.net.flow.FlowRule;
import org.onosproject.net.flow.IndexTableId;
import org.onosproject.net.flow.TableId;
import org.onosproject.net.flow.TrafficSelector;
import org.onosproject.net.flow.criteria.Criteria;
import org.onosproject.net.flow.criteria.Criterion;
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.VlanIdCriterion;
import org.onosproject.net.flow.instructions.Instruction;
import org.onosproject.net.flow.instructions.Instructions;
import org.onosproject.net.flow.instructions.Instructions.OutputInstruction;
import org.onosproject.net.flow.instructions.L2ModificationInstruction;
import org.onosproject.net.group.Group;
import org.onosproject.net.group.GroupBucket;
import org.onosproject.net.host.InterfaceIpAddress;
import org.onosproject.net.intf.Interface;
import org.onosproject.routeservice.ResolvedRoute;
import org.onosproject.segmentrouting.config.SegmentRoutingDeviceConfig;
import org.onosproject.t3.api.DeviceNib;
import org.onosproject.t3.api.DriverNib;
import org.onosproject.t3.api.EdgePortNib;
import org.onosproject.t3.api.FlowNib;
import org.onosproject.t3.api.GroupNib;
import org.onosproject.t3.api.GroupsInDevice;
import org.onosproject.t3.api.HostNib;
import org.onosproject.t3.api.LinkNib;
import org.onosproject.t3.api.MastershipNib;
import org.onosproject.t3.api.MulticastRouteNib;
import org.onosproject.t3.api.NetworkConfigNib;
import org.onosproject.t3.api.NibProfile;
import org.onosproject.t3.api.RouteNib;
import org.onosproject.t3.api.StaticPacketTrace;
import org.onosproject.t3.api.TroubleshootService;
import org.osgi.service.component.annotations.Component;
import org.slf4j.Logger;

import java.net.UnknownHostException;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashSet;
import java.util.List;
import java.util.Optional;
import java.util.Set;
import java.util.stream.Collectors;
import java.util.stream.Stream;
import java.util.stream.StreamSupport;

import static org.onlab.packet.EthType.EtherType;
import static org.onosproject.net.flow.TrafficSelector.Builder;
import static org.onosproject.net.flow.instructions.Instructions.GroupInstruction;
import static org.onosproject.net.flow.instructions.L2ModificationInstruction.ModEtherInstruction;
import static org.onosproject.net.flow.instructions.L2ModificationInstruction.ModMplsHeaderInstruction;
import static org.onosproject.net.flow.instructions.L2ModificationInstruction.ModMplsLabelInstruction;
import static org.onosproject.net.flow.instructions.L2ModificationInstruction.ModVlanIdInstruction;
import static org.onosproject.t3.impl.TroubleshootUtils.compareMac;
import static org.slf4j.LoggerFactory.getLogger;

/**
 * Manager to troubleshoot packets inside the network.
 * Given a representation of a packet follows it's path in the network according to the existing flows and groups in
 * the devices.
 */
@Component(immediate = true, service = TroubleshootService.class)
public class TroubleshootManager implements TroubleshootService {

    private static final Logger log = getLogger(TroubleshootManager.class);

    static final String PACKET_TO_CONTROLLER = "Packet goes to the controller";

    // uses a snapshot (cache) of NIBs instead of interacting with ONOS core in runtime
    protected FlowNib flowNib = FlowNib.getInstance();
    protected GroupNib groupNib = GroupNib.getInstance();
    protected LinkNib linkNib = LinkNib.getInstance();
    protected HostNib hostNib = HostNib.getInstance();
    protected DeviceNib deviceNib = DeviceNib.getInstance();
    protected DriverNib driverNib = DriverNib.getInstance();
    protected MastershipNib mastershipNib = MastershipNib.getInstance();
    protected EdgePortNib edgePortNib = EdgePortNib.getInstance();
    protected RouteNib routeNib = RouteNib.getInstance();
    protected NetworkConfigNib networkConfigNib = NetworkConfigNib.getInstance();
    protected MulticastRouteNib mcastRouteNib = MulticastRouteNib.getInstance();

    @Override
    public boolean checkNibValidity() {
        return Stream.of(flowNib, groupNib, linkNib, hostNib, deviceNib, driverNib,
                mastershipNib, edgePortNib, routeNib, networkConfigNib, mcastRouteNib)
                .allMatch(nib -> nib != null && nib.isValid());
    }

    @Override
    public String printNibSummary() {
        StringBuilder summary = new StringBuilder().append("*** Current NIB in valid: ***\n");
        Stream.of(flowNib, groupNib, linkNib, hostNib, deviceNib, driverNib,
                mastershipNib, edgePortNib, routeNib, networkConfigNib, mcastRouteNib)
                .forEach(nib -> {
                    NibProfile profile = nib.getProfile();
                    summary.append(String.format(
                            nib.getClass().getName() + " created %s from %s\n",
                            profile.date(), profile.sourceType()));
                });

        return summary.append(StringUtils.rightPad("", 125, '-')).toString();
    }

    @Override
    public List<StaticPacketTrace> pingAll(EtherType type) {
        ImmutableList.Builder<StaticPacketTrace> tracesBuilder = ImmutableList.builder();
        hostNib.getHosts().forEach(host -> {
            List<IpAddress> ipAddresses = getIpAddresses(host, type, false);
            if (ipAddresses.size() > 0) {
                //check if the host has only local IPs of that ETH type
                boolean onlyLocalSrc = ipAddresses.size() == 1 && ipAddresses.get(0).isLinkLocal();
                hostNib.getHosts().forEach(hostToPing -> {
                    List<IpAddress> ipAddressesToPing = getIpAddresses(hostToPing, type, false);
                    //check if the other host has only local IPs of that ETH type
                    boolean onlyLocalDst = ipAddressesToPing.size() == 1 && ipAddressesToPing.get(0).isLinkLocal();
                    boolean sameLocation = Sets.intersection(host.locations(), hostToPing.locations()).size() > 0;
                    //Trace is done only if they are both local and under the same location
                    // or not local and if they are not the same host.
                    if (((sameLocation && onlyLocalDst && onlyLocalSrc) ||
                            (!onlyLocalSrc && !onlyLocalDst && ipAddressesToPing.size() > 0))
                            && !host.equals(hostToPing)) {
                        tracesBuilder.addAll(trace(host.id(), hostToPing.id(), type));
                    }
                });
            }
        });
        return tracesBuilder.build();
    }

    @Override
    public Generator<Set<StaticPacketTrace>> pingAllGenerator(EtherType type) {
        return new PingAllGenerator(type, hostNib, this);
    }

    @Override
    public Generator<Set<StaticPacketTrace>> traceMcast(VlanId vlanId) {
        return new McastGenerator(mcastRouteNib, this, vlanId);
    }

    @Override
    public Set<StaticPacketTrace> trace(HostId sourceHost, HostId destinationHost, EtherType etherType) {
        Host source = hostNib.getHost(sourceHost);
        Host destination = hostNib.getHost(destinationHost);

        //Temporary trace to fail in case we don't have enough information or what is provided is incoherent
        StaticPacketTrace failTrace = new StaticPacketTrace(null, null, Pair.of(source, destination));

        if (source == null) {
            failTrace.addResultMessage("Source Host " + sourceHost + " does not exist");
            failTrace.setSuccess(false);

            return ImmutableSet.of(failTrace);
        }

        if (destination == null) {
            failTrace.addResultMessage("Destination Host " + destinationHost + " does not exist");
            failTrace.setSuccess(false);
            return ImmutableSet.of(failTrace);
        }

        TrafficSelector.Builder selectorBuilder = DefaultTrafficSelector.builder()
                .matchEthType(etherType.ethType().toShort())
                .matchEthDst(source.mac())
                .matchVlanId(source.vlan());


        try {
            ImmutableSet.Builder<StaticPacketTrace> traces = ImmutableSet.builder();
            //if the location deviceId is the same, the two hosts are under same subnet and vlan on the interface
            // we are under same leaf so it's L2 Unicast.
            if (areBridged(source, destination)) {
                selectorBuilder.matchEthDst(destination.mac());
                source.locations().forEach(hostLocation -> {
                    selectorBuilder.matchInPort(hostLocation.port());
                    StaticPacketTrace trace = trace(selectorBuilder.build(), hostLocation);
                    trace.addEndpointHosts(Pair.of(source, destination));
                    traces.add(trace);
                });
                //The destination host is not dual homed, if it is the other path might be done through routing.
                if (destination.locations().size() == 1) {
                    return traces.build();
                }
            }
            //handle the IPs for src and dst in case of L3
            if (etherType.equals(EtherType.IPV4) || etherType.equals(EtherType.IPV6)) {

                //Match on the source IP
                if (!matchIP(source, failTrace, selectorBuilder, etherType, true)) {
                    return ImmutableSet.of(failTrace);
                }

                //Match on destination IP
                if (!matchIP(destination, failTrace, selectorBuilder, etherType, false)) {
                    return ImmutableSet.of(failTrace);
                }

            } else {
                failTrace.addResultMessage("Host based trace supports only IPv4 or IPv6 as EtherType, " +
                        "please use packet based");
                failTrace.setSuccess(false);
                return ImmutableSet.of(failTrace);
            }

            //l3 unicast, we get the dst mac of the leaf the source is connected to from netcfg
            SegmentRoutingDeviceConfig segmentRoutingConfig = networkConfigNib.getConfig(source.location()
                    .deviceId(), SegmentRoutingDeviceConfig.class);
            if (segmentRoutingConfig != null) {
                selectorBuilder.matchEthDst(segmentRoutingConfig.routerMac());
            } else {
                failTrace.addResultMessage("Can't get " + source.location().deviceId() +
                        " router MAC from segment routing config can't perform L3 tracing.");
                failTrace.setSuccess(false);
            }
            source.locations().forEach(hostLocation -> {
                selectorBuilder.matchInPort(hostLocation.port());
                StaticPacketTrace trace = trace(selectorBuilder.build(), hostLocation);
                trace.addEndpointHosts(Pair.of(source, destination));
                traces.add(trace);
            });
            return traces.build();

        } catch (ConfigException e) {
            failTrace.addResultMessage("Can't get config " + e.getMessage());
            return ImmutableSet.of(failTrace);
        }
    }

    /**
     * Matches src and dst IPs based on host information.
     *
     * @param host            the host
     * @param failTrace       the trace to use in case of failure
     * @param selectorBuilder the packet we are building to trace
     * @param etherType       the traffic type
     * @param src             is this src host or dst host
     * @return true if properly matched
     */
    private boolean matchIP(Host host, StaticPacketTrace failTrace, Builder selectorBuilder,
                            EtherType etherType, boolean src) {
        List<IpAddress> ips = getIpAddresses(host, etherType, true);

        if (ips.size() > 0) {
            if (etherType.equals(EtherType.IPV4)) {
                if (src) {
                    selectorBuilder.matchIPSrc(ips.get(0).toIpPrefix());
                } else {
                    selectorBuilder.matchIPDst(ips.get(0).toIpPrefix());
                }
            } else if (etherType.equals(EtherType.IPV6)) {
                if (src) {
                    selectorBuilder.matchIPv6Src(ips.get(0).toIpPrefix());
                } else {
                    selectorBuilder.matchIPv6Dst(ips.get(0).toIpPrefix());
                }
            }
        } else {
            failTrace.addResultMessage("Host " + host + " has no " + etherType + " address");
            failTrace.setSuccess(false);
            return false;
        }
        return true;
    }

    List<IpAddress> getIpAddresses(Host host, EtherType etherType, boolean checklocal) {
        return host.ipAddresses().stream().filter(ipAddress -> {
            boolean correctIp = false;
            if (etherType.equals(EtherType.IPV4)) {
                correctIp = ipAddress.isIp4();
            } else if (etherType.equals(EtherType.IPV6)) {
                correctIp = ipAddress.isIp6();
            }
            if (checklocal) {
                correctIp = correctIp && !ipAddress.isLinkLocal();
            }
            return correctIp;
        }).collect(Collectors.toList());
    }

    /**
     * Checks that two hosts are bridged (L2Unicast).
     *
     * @param source      the source host
     * @param destination the destination host
     * @return true if bridged.
     * @throws ConfigException if config can't be properly retrieved
     */
    private boolean areBridged(Host source, Host destination) throws ConfigException {

        //If the locations is not the same we don't even check vlan or subnets
        if (Collections.disjoint(source.locations(), destination.locations())) {
            return false;
        }

        if (!source.vlan().equals(VlanId.NONE) && !destination.vlan().equals(VlanId.NONE)
                && !source.vlan().equals(destination.vlan())) {
            return false;
        }

        InterfaceConfig interfaceCfgH1 = networkConfigNib.getConfig(source.location(), InterfaceConfig.class);
        InterfaceConfig interfaceCfgH2 = networkConfigNib.getConfig(destination.location(), InterfaceConfig.class);
        if (interfaceCfgH1 != null && interfaceCfgH2 != null) {

            //following can be optimized but for clarity is left as is
            Interface intfH1 = interfaceCfgH1.getInterfaces().stream().findFirst().get();
            Interface intfH2 = interfaceCfgH2.getInterfaces().stream().findFirst().get();

            if (source.vlan().equals(VlanId.NONE) && !destination.vlan().equals(VlanId.NONE)) {
                return intfH1.vlanUntagged().equals(destination.vlan()) ||
                        intfH1.vlanNative().equals(destination.vlan());
            }

            if (!source.vlan().equals(VlanId.NONE) && destination.vlan().equals(VlanId.NONE)) {
                return intfH2.vlanUntagged().equals(source.vlan()) ||
                        intfH2.vlanNative().equals(source.vlan());
            }

            if (!intfH1.vlanNative().equals(intfH2.vlanNative())) {
                return false;
            }

            if (!intfH1.vlanUntagged().equals(intfH2.vlanUntagged())) {
                return false;
            }

            List<InterfaceIpAddress> intersection = new ArrayList<>(intfH1.ipAddressesList());
            intersection.retainAll(intfH2.ipAddressesList());
            if (intersection.size() == 0) {
                return false;
            }
        }
        return true;
    }

    @Override
    public StaticPacketTrace trace(TrafficSelector packet, ConnectPoint in) {
        log.info("Tracing packet {} coming in through {}", packet, in);
        //device must exist in ONOS
        Preconditions.checkNotNull(deviceNib.getDevice(in.deviceId()),
                "Device " + in.deviceId() + " must exist in ONOS");

        StaticPacketTrace trace = new StaticPacketTrace(packet, in);
        boolean isDualHomed = getHosts(trace).stream().anyMatch(host -> host.locations().size() > 1);
        //FIXME this can be done recursively
        //Building output connect Points
        List<ConnectPoint> path = new ArrayList<>();
        trace = traceInDevice(trace, packet, in, isDualHomed, path);
        trace = getTrace(path, in, trace, isDualHomed);
        return trace;
    }

    @Override
    public List<Set<StaticPacketTrace>> getMulitcastTrace(VlanId vlanId) {
        Generator<Set<StaticPacketTrace>> gen = new McastGenerator(mcastRouteNib, this, vlanId);
        List<Set<StaticPacketTrace>> multicastTraceList =
                StreamSupport.stream(gen.spliterator(), false).collect(Collectors.toList());
        return multicastTraceList;
    }

    /**
     * Computes a trace for a give packet that start in the network at the given connect point.
     *
     * @param completePath the path traversed by the packet
     * @param in           the input connect point
     * @param trace        the trace to build
     * @param isDualHomed  true if the trace we are doing starts or ends in a dual homed host
     * @return the build trace for that packet.
     */
    private StaticPacketTrace getTrace(List<ConnectPoint> completePath, ConnectPoint in, StaticPacketTrace trace,
                                       boolean isDualHomed) {

        log.debug("------------------------------------------------------------");

        //if the trace already contains the input connect point there is a loop
        if (pathContainsDevice(completePath, in.deviceId())) {
            trace.addResultMessage("Loop encountered in device " + in.deviceId());
            completePath.add(in);
            trace.addCompletePath(completePath);
            trace.setSuccess(false);
            return trace;
        }

        //let's add the input connect point
        completePath.add(in);

        //If the trace has no outputs for the given input we stop here
        if (trace.getGroupOuputs(in.deviceId()) == null) {
            computePath(completePath, trace, null);
            trace.addResultMessage("No output out of device " + in.deviceId() + ". Packet is dropped");
            trace.setSuccess(false);
            return trace;
        }

        //If the trace has outputs we analyze them all
        for (GroupsInDevice outputPath : trace.getGroupOuputs(in.deviceId())) {

            ConnectPoint cp = outputPath.getOutput();
            log.debug("Connect point in {}", in);
            log.debug("Output path {}", cp);
            log.debug("{}", outputPath.getFinalPacket());

            //Hosts for the the given output
            Set<Host> hostsList = hostNib.getConnectedHosts(cp);
            //Hosts queried from the original ip or mac
            Set<Host> hosts = getHosts(trace);

            if (in.equals(cp) && trace.getInitialPacket().getCriterion(Criterion.Type.VLAN_VID) != null &&
                    outputPath.getFinalPacket().getCriterion(Criterion.Type.VLAN_VID) != null
                    && ((VlanIdCriterion) trace.getInitialPacket().getCriterion(Criterion.Type.VLAN_VID)).vlanId()
                    .equals(((VlanIdCriterion) outputPath.getFinalPacket().getCriterion(Criterion.Type.VLAN_VID))
                            .vlanId())) {
                if (trace.getGroupOuputs(in.deviceId()).size() == 1 &&
                        computePath(completePath, trace, outputPath.getOutput())) {
                    trace.addResultMessage("Connect point out " + cp + " is same as initial input " + in);
                    trace.setSuccess(false);
                }
            } else if (!Collections.disjoint(hostsList, hosts)) {
                //If the two host collections contain the same item it means we reached the proper output
                log.debug("Stopping here because host is expected destination {}, reached through", completePath);
                if (computePath(completePath, trace, outputPath.getOutput())) {
                    trace.addResultMessage("Reached required destination Host " + cp);
                    trace.setSuccess(true);
                }
                break;
            } else if (cp.port().equals(PortNumber.CONTROLLER)) {

                //Getting the master when the packet gets sent as packet in
                NodeId master = mastershipNib.getMasterFor(cp.deviceId());
                // TODO if we don't need to print master node id, exclude mastership NIB which is used only here
                trace.addResultMessage(PACKET_TO_CONTROLLER + " " + master.id());
                computePath(completePath, trace, outputPath.getOutput());
                handleVlanToController(outputPath, trace);

            } else if (linkNib.getEgressLinks(cp).size() > 0) {

                //TODO this can be optimized if we use a Tree structure for paths.
                //if we already have outputs let's check if the one we are considering starts from one of the devices
                // in any of the ones we have.
                if (trace.getCompletePaths().size() > 0) {
                    ConnectPoint inputForOutput = null;
                    List<ConnectPoint> previousPath = new ArrayList<>();
                    for (List<ConnectPoint> path : trace.getCompletePaths()) {
                        for (ConnectPoint connect : path) {
                            //if the path already contains the input for the output we've found we use it
                            if (connect.equals(in)) {
                                inputForOutput = connect;
                                previousPath = path;
                                break;
                            }
                        }
                    }

                    //we use the pre-existing path up to the point we fork to a new output
                    if (inputForOutput != null && completePath.contains(inputForOutput)) {
                        List<ConnectPoint> temp = new ArrayList<>(previousPath);
                        temp = temp.subList(0, previousPath.indexOf(inputForOutput) + 1);
                        if (completePath.containsAll(temp)) {
                            completePath = temp;
                        }
                    }
                }

                //let's add the ouput for the input
                completePath.add(cp);
                //let's compute the links for the given output
                Set<Link> links = linkNib.getEgressLinks(cp);
                log.debug("Egress Links {}", links);
                //For each link we trace the corresponding device
                for (Link link : links) {
                    ConnectPoint dst = link.dst();
                    //change in-port to the dst link in port
                    Builder updatedPacket = DefaultTrafficSelector.builder();
                    outputPath.getFinalPacket().criteria().forEach(updatedPacket::add);
                    updatedPacket.add(Criteria.matchInPort(dst.port()));
                    log.debug("DST Connect Point {}", dst);
                    //build the elements for that device
                    traceInDevice(trace, updatedPacket.build(), dst, isDualHomed, completePath);
                    //continue the trace along the path
                    getTrace(completePath, dst, trace, isDualHomed);
                }
            } else if (edgePortNib.isEdgePoint(outputPath.getOutput()) &&
                    trace.getInitialPacket().getCriterion(Criterion.Type.ETH_DST) != null &&
                    ((EthCriterion) trace.getInitialPacket().getCriterion(Criterion.Type.ETH_DST))
                            .mac().isMulticast()) {
                trace.addResultMessage("Packet is multicast and reached output " + outputPath.getOutput() +
                        " which is enabled and is edge port");
                trace.setSuccess(true);
                computePath(completePath, trace, outputPath.getOutput());
                if (!hasOtherOutput(in.deviceId(), trace, outputPath.getOutput())) {
                    return trace;
                }
            } else if (deviceNib.getPort(cp) != null && deviceNib.getPort(cp).isEnabled()) {
                EthTypeCriterion ethTypeCriterion = (EthTypeCriterion) trace.getInitialPacket()
                        .getCriterion(Criterion.Type.ETH_TYPE);
                //We treat as correct output only if it's not LLDP or BDDP
                if (!(ethTypeCriterion.ethType().equals(EtherType.LLDP.ethType())
                        && !ethTypeCriterion.ethType().equals(EtherType.BDDP.ethType()))) {
                    if (computePath(completePath, trace, outputPath.getOutput())) {
                        if (hostsList.isEmpty()) {
                            trace.addResultMessage("Packet is " + ((EthTypeCriterion) outputPath.getFinalPacket()
                                    .getCriterion(Criterion.Type.ETH_TYPE)).ethType() + " and reached " +
                                    cp + " with no hosts connected ");
                        } else {
                            IpAddress ipAddress = null;
                            if (trace.getInitialPacket().getCriterion(Criterion.Type.IPV4_DST) != null) {
                                ipAddress = ((IPCriterion) trace.getInitialPacket()
                                        .getCriterion(Criterion.Type.IPV4_DST)).ip().address();
                            } else if (trace.getInitialPacket().getCriterion(Criterion.Type.IPV6_DST) != null) {
                                ipAddress = ((IPCriterion) trace.getInitialPacket()
                                        .getCriterion(Criterion.Type.IPV6_DST)).ip().address();
                            }
                            if (ipAddress != null) {
                                IpAddress finalIpAddress = ipAddress;
                                if (hostsList.stream().anyMatch(host -> host.ipAddresses().contains(finalIpAddress)) ||
                                        hostNib.getHostsByIp(finalIpAddress).isEmpty()) {
                                    trace.addResultMessage("Packet is " +
                                            ((EthTypeCriterion) outputPath.getFinalPacket()
                                                    .getCriterion(Criterion.Type.ETH_TYPE)).ethType() +
                                            " and reached " + cp + " with hosts " + hostsList);
                                } else {
                                    trace.addResultMessage("Wrong output " + cp + " for required destination ip " +
                                            ipAddress);
                                    trace.setSuccess(false);
                                }
                            } else {
                                trace.addResultMessage("Packet is " + ((EthTypeCriterion) outputPath.getFinalPacket()
                                        .getCriterion(Criterion.Type.ETH_TYPE)).ethType() + " and reached " +
                                        cp + " with hosts " + hostsList);
                            }
                        }
                        trace.setSuccess(true);
                    }
                }

            } else {
                computePath(completePath, trace, cp);
                trace.setSuccess(false);
                if (deviceNib.getPort(cp) == null) {
                    //Port is not existent on device.
                    log.warn("Port {} is not available on device.", cp);
                    trace.addResultMessage("Port " + cp + "is not available on device. Packet is dropped");
                } else {
                    //No links means that the packet gets dropped.
                    log.warn("No links out of {}", cp);
                    trace.addResultMessage("No links depart from " + cp + ". Packet is dropped");
                }
            }
        }
        return trace;
    }


    /**
     * If the initial packet comes tagged with a Vlan we output it with that to ONOS.
     * If ONOS applied a vlan we remove it.
     *
     * @param outputPath the output
     * @param trace      the trace we are building
     */

    private void handleVlanToController(GroupsInDevice outputPath, StaticPacketTrace trace) {

        VlanIdCriterion initialVid = (VlanIdCriterion) trace.getInitialPacket().getCriterion(Criterion.Type.VLAN_VID);
        VlanIdCriterion finalVid = (VlanIdCriterion) outputPath.getFinalPacket().getCriterion(Criterion.Type.VLAN_VID);

        if (initialVid != null && !initialVid.equals(finalVid) && initialVid.vlanId().equals(VlanId.NONE)) {

            Set<Criterion> finalCriteria = new HashSet<>(outputPath.getFinalPacket().criteria());
            //removing the final vlanId
            finalCriteria.remove(finalVid);
            Builder packetUpdated = DefaultTrafficSelector.builder();
            finalCriteria.forEach(packetUpdated::add);
            //Initial was none so we set it to that
            packetUpdated.add(Criteria.matchVlanId(VlanId.NONE));
            //Update final packet
            outputPath.setFinalPacket(packetUpdated.build());
        }
    }

    /**
     * Checks if the device has other outputs than the given connect point.
     *
     * @param inDeviceId the device
     * @param trace      the trace we are building
     * @param cp         an output connect point
     * @return true if the device has other outputs.
     */
    private boolean hasOtherOutput(DeviceId inDeviceId, StaticPacketTrace trace, ConnectPoint cp) {
        return trace.getGroupOuputs(inDeviceId).stream().filter(groupsInDevice -> {
            return !groupsInDevice.getOutput().equals(cp);
        }).count() > 0;
    }

    /**
     * Checks if the path contains the device.
     *
     * @param completePath the path
     * @param deviceId     the device to check
     * @return true if the path contains the device
     */
    //TODO might prove costly, improvement: a class with both CPs and DeviceIds point.
    private boolean pathContainsDevice(List<ConnectPoint> completePath, DeviceId deviceId) {
        for (ConnectPoint cp : completePath) {
            if (cp.deviceId().equals(deviceId)) {
                return true;
            }
        }
        return false;
    }

    /**
     * Gets the hosts for the given initial packet.
     *
     * @param trace the trace we are building
     * @return set of the hosts we are trying to reach
     */
    private Set<Host> getHosts(StaticPacketTrace trace) {
        IPCriterion ipv4Criterion = ((IPCriterion) trace.getInitialPacket()
                .getCriterion(Criterion.Type.IPV4_DST));
        IPCriterion ipv6Criterion = ((IPCriterion) trace.getInitialPacket()
                .getCriterion(Criterion.Type.IPV6_DST));
        Set<Host> hosts = new HashSet<>();
        if (ipv4Criterion != null) {
            hosts.addAll(hostNib.getHostsByIp(ipv4Criterion.ip().address()));
        }
        if (ipv6Criterion != null) {
            hosts.addAll(hostNib.getHostsByIp(ipv6Criterion.ip().address()));
        }
        EthCriterion ethCriterion = ((EthCriterion) trace.getInitialPacket()
                .getCriterion(Criterion.Type.ETH_DST));
        if (ethCriterion != null) {
            hosts.addAll(hostNib.getHostsByMac(ethCriterion.mac()));
        }
        return hosts;
    }

    /**
     * Computes the list of traversed connect points.
     *
     * @param completePath the list of devices
     * @param trace        the trace we are building
     * @param output       the final output connect point
     */
    private boolean computePath(List<ConnectPoint> completePath, StaticPacketTrace trace, ConnectPoint output) {
        List<ConnectPoint> traverseList = new ArrayList<>();
        if (!completePath.contains(trace.getInitialConnectPoint())) {
            traverseList.add(trace.getInitialConnectPoint());
        }

        if (output != null && trace.getInitialConnectPoint().deviceId().equals(output.deviceId())) {
            trace.addCompletePath(ImmutableList.of(trace.getInitialConnectPoint(), output));
            return true;
        }

        traverseList.addAll(completePath);
        if (output != null && !completePath.contains(output)) {
            traverseList.add(output);
        }
        if (!trace.getCompletePaths().contains(traverseList)) {
            trace.addCompletePath(ImmutableList.copyOf(traverseList));
            return true;
        }
        return false;
    }

    /**
     * Traces the packet inside a device starting from an input connect point.
     *
     * @param trace        the trace we are building
     * @param packet       the packet we are tracing
     * @param in           the input connect point.
     * @param isDualHomed  true if the trace we are doing starts or ends in a dual homed host
     * @param completePath the path up until this device
     * @return updated trace
     */
    private StaticPacketTrace traceInDevice(StaticPacketTrace trace, TrafficSelector packet, ConnectPoint in,
                                            boolean isDualHomed, List<ConnectPoint> completePath) {

        boolean multipleRoutes = false;
        if (trace.getGroupOuputs(in.deviceId()) != null) {
            multipleRoutes = multipleRoutes(trace);
        }
        if (trace.getGroupOuputs(in.deviceId()) != null && !isDualHomed && !multipleRoutes) {
            log.debug("Trace already contains device and given outputs");
            return trace;
        }

        log.debug("Packet {} coming in from {}", packet, in);

        //if device is not available exit here.
        if (!deviceNib.isAvailable(in.deviceId())) {
            trace.addResultMessage("Device is offline " + in.deviceId());
            computePath(completePath, trace, null);
            return trace;
        }

        //handle when the input is the controller
        //NOTE, we are using the input port as a convenience to carry the CONTROLLER port number even if
        // a packet in from the controller will not actually traverse the pipeline and have no such notion
        // as the input port.
        if (in.port().equals(PortNumber.CONTROLLER)) {
            StaticPacketTrace outputTrace = inputFromController(trace, in);
            if (outputTrace != null) {
                return trace;
            }
        }

        List<FlowEntry> flows = new ArrayList<>();
        List<FlowEntry> outputFlows = new ArrayList<>();
        List<Instruction> deferredInstructions = new ArrayList<>();

        FlowEntry nextTableIdEntry = findNextTableIdEntry(in.deviceId(), -1);
        if (nextTableIdEntry == null) {
            trace.addResultMessage("No flow rules for device " + in.deviceId() + ". Aborting");
            computePath(completePath, trace, null);
            trace.setSuccess(false);
            return trace;
        }
        TableId tableId = nextTableIdEntry.table();
        FlowEntry flowEntry;
        boolean output = false;
        while (!output) {
            log.debug("Searching a Flow Entry on table {} for packet {}", tableId, packet);
            //get the rule that matches the incoming packet
            flowEntry = matchHighestPriority(packet, in, tableId);
            log.debug("Found Flow Entry {}", flowEntry);

            boolean isOfdpaHardware = TroubleshootUtils.hardwareOfdpaMap
                    .getOrDefault(driverNib.getDriverName(in.deviceId()), false);

            //if the flow entry on a table is null and we are on hardware we treat as table miss, with few exceptions
            if (flowEntry == null && isOfdpaHardware) {
                log.debug("Ofdpa Hw setup, no flow rule means table miss");

                if (((IndexTableId) tableId).id() == 27) {
                    //Apparently a miss but Table 27 on OFDPA is a fixed table
                    packet = handleOfdpa27FixedTable(trace, packet);
                }

                //Finding next table to go In case of miss
                nextTableIdEntry = findNextTableIdEntry(in.deviceId(), ((IndexTableId) tableId).id());
                log.debug("Next table id entry {}", nextTableIdEntry);

                //FIXME find better solution that enable granularity greater than 0 or all rules
                //(another possibility is max tableId)
                if (nextTableIdEntry == null && flows.size() == 0) {
                    trace.addResultMessage("No matching flow rules for device " + in.deviceId() + ". Aborting");
                    computePath(completePath, trace, null);
                    trace.setSuccess(false);
                    return trace;

                } else if (nextTableIdEntry == null) {
                    //Means that no more flow rules are present
                    output = true;

                } else if (((IndexTableId) tableId).id() == 20) {
                    //if the table is 20 OFDPA skips to table 50
                    log.debug("A miss on Table 20 on OFDPA means that we skip directly to table 50");
                    tableId = IndexTableId.of(50);

                } else if (((IndexTableId) tableId).id() == 40) {
                    //if the table is 40 OFDPA skips to table 60
                    log.debug("A miss on Table 40 on OFDPA means that we skip directly to table 60");
                    tableId = IndexTableId.of(60);
                } else {
                    tableId = nextTableIdEntry.table();
                }

            } else if (flowEntry == null) {
                trace.addResultMessage("Packet has no match on table " + tableId + " in device " +
                        in.deviceId() + ". Dropping");
                computePath(completePath, trace, null);
                trace.setSuccess(false);
                return trace;
            } else {

                //IF the table has a transition
                if (flowEntry.treatment().tableTransition() != null) {
                    //update the next table we transitions to
                    tableId = IndexTableId.of(flowEntry.treatment().tableTransition().tableId());
                    log.debug("Flow Entry has transition to table Id {}", tableId);
                    flows.add(flowEntry);
                } else {
                    //table has no transition so it means that it's an output rule if on the last table
                    log.debug("Flow Entry has no transition to table, treating as last rule {}", flowEntry);
                    flows.add(flowEntry);
                    outputFlows.add(flowEntry);
                    output = true;
                }
                //update the packet according to the immediate actions of this flow rule.
                packet = updatePacket(packet, flowEntry.treatment().immediate()).build();

                //save the deferred rules for later
                deferredInstructions.addAll(flowEntry.treatment().deferred());

                //If the flow requires to clear deferred actions we do so for all the ones we encountered.
                if (flowEntry.treatment().clearedDeferred()) {
                    deferredInstructions.clear();
                }

                //On table 10 OFDPA needs two rules to apply the vlan if none and then to transition to the next table.
                if (needsSecondTable10Flow(flowEntry, isOfdpaHardware)) {

                    //Let's get the packet vlanId instruction
                    VlanIdCriterion packetVlanIdCriterion =
                            (VlanIdCriterion) packet.getCriterion(Criterion.Type.VLAN_VID);

                    //Let's get the flow entry vlan mod instructions
                    ModVlanIdInstruction entryModVlanIdInstruction = (ModVlanIdInstruction) flowEntry.treatment()
                            .immediate().stream()
                            .filter(instruction -> instruction instanceof ModVlanIdInstruction)
                            .findFirst().orElse(null);

                    //If the entry modVlan is not null we need to make sure that the packet has been updated and there
                    // is a flow rule that matches on same criteria and with updated vlanId
                    if (entryModVlanIdInstruction != null) {

                        FlowEntry secondVlanFlow = getSecondFlowEntryOnTable10(packet, in,
                                packetVlanIdCriterion, entryModVlanIdInstruction);

                        //We found the flow that we expected
                        if (secondVlanFlow != null) {
                            flows.add(secondVlanFlow);
                        } else {
                            trace.addResultMessage("Missing forwarding rule for tagged packet on " + in);
                            computePath(completePath, trace, null);
                            return trace;
                        }
                    }

                }

            }
        }

        //Creating a modifiable builder for the output packet
        Builder builder = DefaultTrafficSelector.builder();
        packet.criteria().forEach(builder::add);

        //Adding all the flows to the trace
        trace.addFlowsForDevice(in.deviceId(), ImmutableList.copyOf(flows));

        List<PortNumber> outputPorts = new ArrayList<>();
        List<FlowEntry> outputFlowEntries = handleFlows(trace, packet, in, outputFlows, builder, outputPorts);


        log.debug("Handling Groups");
        //Analyze Groups
        List<Group> groups = new ArrayList<>();

        Collection<FlowEntry> nonOutputFlows = flows;
        nonOutputFlows.removeAll(outputFlowEntries);

        //Handling groups pointed at by immediate instructions
        for (FlowEntry entry : flows) {
            getGroupsFromInstructions(trace, groups, entry.treatment().immediate(),
                    entry.deviceId(), builder, outputPorts, in, completePath);
        }

        //If we have deferred instructions at this point we handle them.
        if (deferredInstructions.size() > 0) {
            builder = handleDeferredActions(trace, packet, in, deferredInstructions, outputPorts, groups, completePath);

        }
        packet = builder.build();

        log.debug("Output Packet {}", packet);
        return trace;
    }

    private List<FlowEntry> handleFlows(StaticPacketTrace trace, TrafficSelector packet, ConnectPoint in,
                                        List<FlowEntry> outputFlows, Builder builder, List<PortNumber> outputPorts) {
        //TODO optimization
        //outputFlows contains also last rule of device, so we need filtering for OUTPUT instructions.
        List<FlowEntry> outputFlowEntries = outputFlows.stream().filter(flow -> flow.treatment()
                .allInstructions().stream().filter(instruction -> instruction.type()
                        .equals(Instruction.Type.OUTPUT)).count() > 0).collect(Collectors.toList());

        if (outputFlowEntries.size() > 1) {
            trace.addResultMessage("More than one flow rule with OUTPUT instruction");
            log.warn("There cannot be more than one flow entry with OUTPUT instruction for {}", packet);
        }

        if (outputFlowEntries.size() == 1) {

            OutputInstruction outputInstruction = (OutputInstruction) outputFlowEntries.get(0).treatment()
                    .allInstructions().stream()
                    .filter(instruction -> {
                        return instruction.type().equals(Instruction.Type.OUTPUT);
                    }).findFirst().get();

            //FIXME using GroupsInDevice for output even if flows.
            buildOutputFromDevice(trace, in, builder, outputPorts, outputInstruction, ImmutableList.of());

        }
        return outputFlowEntries;
    }

    private boolean multipleRoutes(StaticPacketTrace trace) {
        boolean multipleRoutes = false;
        IPCriterion ipCriterion = ((IPCriterion) trace.getInitialPacket().getCriterion(Criterion.Type.IPV4_DST));
        IpAddress ip = null;
        if (ipCriterion != null) {
            ip = ipCriterion.ip().address();
        } else if (trace.getInitialPacket().getCriterion(Criterion.Type.IPV6_DST) != null) {
            ip = ((IPCriterion) trace.getInitialPacket().getCriterion(Criterion.Type.IPV6_DST)).ip().address();
        }
        if (ip != null) {
            Optional<ResolvedRoute> optionalRoute = routeNib.longestPrefixLookup(ip);
            if (optionalRoute.isPresent()) {
                ResolvedRoute route = optionalRoute.get();
                multipleRoutes = routeNib.getAllResolvedRoutes(route.prefix()).size() > 1;
            }
        }
        return multipleRoutes;
    }

    /**
     * Handles the specific case where the Input is the controller.
     * Note that the in port is used as a convenience to store the port of the controller even if the packet in
     * from a controller should not have a physical input port. The in port from the Controller is used to make sure
     * the flood to all active physical ports of the device.
     *
     * @param trace the trace
     * @param in    the controller port
     * @return the augmented trace.
     */
    private StaticPacketTrace inputFromController(StaticPacketTrace trace, ConnectPoint in) {
        EthTypeCriterion ethTypeCriterion = (EthTypeCriterion) trace.getInitialPacket()
                .getCriterion(Criterion.Type.ETH_TYPE);
        //If the packet is LLDP or BDDP we flood it on all active ports of the switch.
        if (ethTypeCriterion != null && (ethTypeCriterion.ethType().equals(EtherType.LLDP.ethType())
                || ethTypeCriterion.ethType().equals(EtherType.BDDP.ethType()))) {
            //get the active ports
            List<Port> enabledPorts = deviceNib.getPorts(in.deviceId()).stream()
                    .filter(Port::isEnabled)
                    .collect(Collectors.toList());
            //build an output from each one
            enabledPorts.forEach(port -> {
                GroupsInDevice output = new GroupsInDevice(new ConnectPoint(port.element().id(), port.number()),
                        ImmutableList.of(), trace.getInitialPacket());
                trace.addGroupOutputPath(in.deviceId(), output);
            });
            return trace;
        }
        return null;
    }

    private boolean needsSecondTable10Flow(FlowEntry flowEntry, boolean isOfdpaHardware) {
        return isOfdpaHardware && flowEntry.table().equals(IndexTableId.of(10))
                && flowEntry.selector().getCriterion(Criterion.Type.VLAN_VID) != null
                && ((VlanIdCriterion) flowEntry.selector().getCriterion(Criterion.Type.VLAN_VID))
                .vlanId().equals(VlanId.NONE);
    }

    /**
     * Method that finds a flow rule on table 10 that matches the packet and the VLAN of the already
     * found rule on table 10. This is because OFDPA needs two rules on table 10, first to apply the rule,
     * second to transition to following table
     *
     * @param packet                    the incoming packet
     * @param in                        the input connect point
     * @param packetVlanIdCriterion     the vlan criterion from the packet
     * @param entryModVlanIdInstruction the entry vlan instruction
     * @return the second flow entry that matched
     */
    private FlowEntry getSecondFlowEntryOnTable10(TrafficSelector packet, ConnectPoint in,
                                                  VlanIdCriterion packetVlanIdCriterion,
                                                  ModVlanIdInstruction entryModVlanIdInstruction) {
        FlowEntry secondVlanFlow = null;
        //Check the packet has been update from the first rule.
        if (packetVlanIdCriterion.vlanId().equals(entryModVlanIdInstruction.vlanId())) {
            //find a rule on the same table that matches the vlan and
            // also all the other elements of the flow such as input port
            secondVlanFlow = Lists.newArrayList(flowNib.getFlowEntriesByState(in.deviceId(),
                    FlowEntry.FlowEntryState.ADDED)
                    .iterator()).stream()
                    .filter(entry -> {
                        return entry.table().equals(IndexTableId.of(10));
                    })
                    .filter(entry -> {
                        VlanIdCriterion criterion = (VlanIdCriterion) entry.selector()
                                .getCriterion(Criterion.Type.VLAN_VID);
                        return criterion != null && match(packet, entry)
                                && criterion.vlanId().equals(entryModVlanIdInstruction.vlanId());
                    }).findFirst().orElse(null);

        }
        return secondVlanFlow;
    }


    /**
     * Handles table 27 in Ofpda which is a fixed table not visible to any controller that handles Mpls Labels.
     *
     * @param packet the incoming packet
     * @return the updated packet
     */
    private TrafficSelector handleOfdpa27FixedTable(StaticPacketTrace trace, TrafficSelector packet) {
        log.debug("Handling table 27 on OFDPA, removing mpls ETH Type and change mpls label");
        Criterion mplsCriterion = packet.getCriterion(Criterion.Type.ETH_TYPE);
        ImmutableList.Builder<Instruction> builder = ImmutableList.builder();

        //If the pakcet comes in with the expected elements we update it as per OFDPA spec.
        if (mplsCriterion != null && ((EthTypeCriterion) mplsCriterion).ethType()
                .equals(EtherType.MPLS_UNICAST.ethType())) {
            //TODO update with parsing with eth MPLS pop Instruction for treating label an bos
            Instruction ethInstruction = Instructions.popMpls(((EthTypeCriterion) trace.getInitialPacket()
                    .getCriterion(Criterion.Type.ETH_TYPE)).ethType());
            //FIXME what do we use as L3_Unicast mpls Label ?
            //translateInstruction(builder, ethInstruction);
            builder.add(ethInstruction);
        }
        packet = updatePacket(packet, builder.build()).build();
        return packet;
    }

    /**
     * Finds the flow entry with the minimun next table Id.
     *
     * @param deviceId  the device to search
     * @param currentId the current id. the search will use this as minimum
     * @return the flow entry with the minimum table Id after the given one.
     */
    private FlowEntry findNextTableIdEntry(DeviceId deviceId, int currentId) {

        final Comparator<FlowEntry> comparator = Comparator.comparing((FlowEntry f) -> ((IndexTableId) f.table()).id());
        return Lists.newArrayList(flowNib.getFlowEntriesByState(deviceId, FlowEntry.FlowEntryState.ADDED)
                .iterator()).stream()
                .filter(f -> ((IndexTableId) f.table()).id() > currentId).min(comparator).orElse(null);
    }

    private Builder handleDeferredActions(StaticPacketTrace trace, TrafficSelector packet,
                                          ConnectPoint in, List<Instruction> deferredInstructions,
                                          List<PortNumber> outputPorts, List<Group> groups,
                                          List<ConnectPoint> completePath) {

        //Update the packet with the deferred instructions
        Builder builder = updatePacket(packet, deferredInstructions);

        //Gather any output instructions from the deferred instruction
        List<Instruction> outputFlowInstruction = deferredInstructions.stream().filter(instruction -> {
            return instruction.type().equals(Instruction.Type.OUTPUT);
        }).collect(Collectors.toList());

        //We are considering deferred instructions from flows, there can only be one output.
        if (outputFlowInstruction.size() > 1) {
            trace.addResultMessage("More than one flow rule with OUTPUT instruction");
            log.warn("There cannot be more than one flow entry with OUTPUT instruction for {}", packet);
        }
        //If there is one output let's go through that
        if (outputFlowInstruction.size() == 1) {
            buildOutputFromDevice(trace, in, builder, outputPorts, (OutputInstruction) outputFlowInstruction.get(0),
                    ImmutableList.of());
        }
        //If there is no output let's see if there any deferred instruction point to groups.
        if (outputFlowInstruction.size() == 0) {
            getGroupsFromInstructions(trace, groups, deferredInstructions,
                    in.deviceId(), builder, outputPorts, in, completePath);
        }
        return builder;
    }

    /**
     * Gets group information from instructions.
     *
     * @param trace           the trace we are building
     * @param groupsForDevice the set of groups for this device
     * @param instructions    the set of instructions we are searching for groups.
     * @param deviceId        the device we are considering
     * @param builder         the builder of the input packet
     * @param outputPorts     the output ports for that packet
     */
    private void getGroupsFromInstructions(StaticPacketTrace trace, List<Group> groupsForDevice,
                                           List<Instruction> instructions, DeviceId deviceId,
                                           Builder builder, List<PortNumber> outputPorts,
                                           ConnectPoint in, List<ConnectPoint> completePath) {
        List<Instruction> groupInstructionlist = new ArrayList<>();
        // sort instructions according to priority (larger Instruction.Type ENUM constant first)
        // which enables to treat other actions before the OUTPUT action
        //TODO improve the priority scheme according to the OpenFlow ActionSet spec
        List<Instruction> instructionsSorted = new ArrayList<>();
        instructionsSorted.addAll(instructions);
        instructionsSorted.sort((instr1, instr2) -> {
            return Integer.compare(instr2.type().ordinal(), instr1.type().ordinal());
        });

        for (Instruction instruction : instructionsSorted) {
            log.debug("Considering Instruction {}", instruction);
            //if the instruction is not group we need to update the packet or add the output
            //to the possible outputs for this packet
            if (!instruction.type().equals(Instruction.Type.GROUP)) {
                //if the instruction is not group we need to update the packet or add the output
                //to the possible outputs for this packet
                if (instruction.type().equals(Instruction.Type.OUTPUT)) {
                    buildOutputFromDevice(trace, in, builder, outputPorts,
                            (OutputInstruction) instruction, ImmutableList.copyOf(groupsForDevice));
                    //clearing the groups because we start from the top.
                    groupsForDevice.clear();
                } else {
                    builder = translateInstruction(builder, instruction);
                }
            } else {
                //if the instuction is pointing to a group we need to get the group
                groupInstructionlist.add(instruction);
            }
        }
        //handle all the internal instructions pointing to a group.
        for (Instruction instr : groupInstructionlist) {
            GroupInstruction groupInstruction = (GroupInstruction) instr;
            Group group = Lists.newArrayList(groupNib.getGroups(deviceId)).stream().filter(groupInternal -> {
                return groupInternal.id().equals(groupInstruction.groupId());
            }).findAny().orElse(null);
            if (group == null) {
                trace.addResultMessage("Null group for Instruction " + instr);
                trace.setSuccess(false);
                break;
            }
            if (group.buckets().buckets().size() == 0) {
                trace.addResultMessage("Group " + group.id() + " has no buckets");
                trace.setSuccess(false);
                computePath(completePath, trace, null);
                break;
            }

            //Cycle in each of the group's buckets and add them to the groups for this Device.
            for (GroupBucket bucket : group.buckets().buckets()) {

                //add the group to the traversed groups
                if (!groupsForDevice.contains(group)) {
                    groupsForDevice.add(group);
                }

                getGroupsFromInstructions(trace, groupsForDevice, bucket.treatment().allInstructions(),
                        deviceId, builder, outputPorts, in, completePath);
            }
        }
    }

    /**
     * Check if the output is the input port, if so adds a dop result message, otherwise builds
     * a possible output from this device.
     *
     * @param trace             the trace
     * @param in                the input connect point
     * @param builder           the packet builder
     * @param outputPorts       the list of output ports for this device
     * @param outputInstruction the output instruction
     * @param groupsForDevice   the groups we output from
     */
    private void buildOutputFromDevice(StaticPacketTrace trace, ConnectPoint in, Builder builder,
                                       List<PortNumber> outputPorts, OutputInstruction outputInstruction,
                                       List<Group> groupsForDevice) {
        ConnectPoint output = new ConnectPoint(in.deviceId(), outputInstruction.port());

        outputPorts.add(outputInstruction.port());

        GroupsInDevice device = new GroupsInDevice(output, groupsForDevice, builder.build());
        if (trace.getGroupOuputs(output.deviceId()) != null
                && trace.getGroupOuputs(output.deviceId()).contains(device)) {
            return;
        }
        trace.addGroupOutputPath(in.deviceId(),
                new GroupsInDevice(output, groupsForDevice, builder.build()));
    }

    /**
     * Applies all give instructions to the input packet.
     *
     * @param packet       the input packet
     * @param instructions the set of instructions
     * @return the packet with the applied instructions
     */
    private Builder updatePacket(TrafficSelector packet, List<Instruction> instructions) {
        Builder newSelector = DefaultTrafficSelector.builder();
        packet.criteria().forEach(newSelector::add);
        //FIXME optimize
        for (Instruction instruction : instructions) {
            newSelector = translateInstruction(newSelector, instruction);
        }
        return newSelector;
    }

    /**
     * Applies an instruction to the packet in the form of a selector.
     *
     * @param newSelector the packet selector
     * @param instruction the instruction to be translated
     * @return the new selector with the applied instruction
     */
    private Builder translateInstruction(Builder newSelector, Instruction instruction) {
        log.debug("Translating instruction {}", instruction);
        log.debug("New Selector {}", newSelector.build());
        //TODO add as required
        Criterion criterion = null;
        switch (instruction.type()) {
            case L2MODIFICATION:
                L2ModificationInstruction l2Instruction = (L2ModificationInstruction) instruction;
                switch (l2Instruction.subtype()) {
                    case VLAN_ID:
                        ModVlanIdInstruction vlanIdInstruction =
                                (ModVlanIdInstruction) instruction;
                        VlanId id = vlanIdInstruction.vlanId();
                        criterion = Criteria.matchVlanId(id);
                        break;
                    case VLAN_POP:
                        criterion = Criteria.matchVlanId(VlanId.NONE);
                        break;
                    case MPLS_PUSH:
                        ModMplsHeaderInstruction mplsEthInstruction =
                                (ModMplsHeaderInstruction) instruction;
                        criterion = Criteria.matchEthType(mplsEthInstruction.ethernetType().toShort());
                        break;
                    case MPLS_POP:
                        ModMplsHeaderInstruction mplsPopInstruction =
                                (ModMplsHeaderInstruction) instruction;
                        criterion = Criteria.matchEthType(mplsPopInstruction.ethernetType().toShort());

                        //When popping MPLS we remove label and BOS
                        TrafficSelector temporaryPacket = newSelector.build();
                        if (temporaryPacket.getCriterion(Criterion.Type.MPLS_LABEL) != null) {
                            Builder noMplsSelector = DefaultTrafficSelector.builder();
                            temporaryPacket.criteria().stream().filter(c -> {
                                return !c.type().equals(Criterion.Type.MPLS_LABEL) &&
                                        !c.type().equals(Criterion.Type.MPLS_BOS);
                            }).forEach(noMplsSelector::add);
                            newSelector = noMplsSelector;
                        }

                        break;
                    case MPLS_LABEL:
                        ModMplsLabelInstruction mplsLabelInstruction =
                                (ModMplsLabelInstruction) instruction;
                        criterion = Criteria.matchMplsLabel(mplsLabelInstruction.label());
                        newSelector.matchMplsBos(true);
                        break;
                    case ETH_DST:
                        ModEtherInstruction modEtherDstInstruction =
                                (ModEtherInstruction) instruction;
                        criterion = Criteria.matchEthDst(modEtherDstInstruction.mac());
                        break;
                    case ETH_SRC:
                        ModEtherInstruction modEtherSrcInstruction =
                                (ModEtherInstruction) instruction;
                        criterion = Criteria.matchEthSrc(modEtherSrcInstruction.mac());
                        break;
                    default:
                        log.debug("Unsupported L2 Instruction");
                        break;
                }
                break;
            default:
                log.debug("Unsupported Instruction");
                break;
        }
        if (criterion != null) {
            log.debug("Adding criterion {}", criterion);
            newSelector.add(criterion);
        }
        return newSelector;
    }

    /**
     * Finds the rule in the device that mathces the input packet and has the highest priority.
     *
     * @param packet  the input packet
     * @param in      the connect point the packet comes in from
     * @param tableId the table to search
     * @return the flow entry
     */
    private FlowEntry matchHighestPriority(TrafficSelector packet, ConnectPoint in, TableId tableId) {
        //Computing the possible match rules.
        final Comparator<FlowEntry> comparator = Comparator.comparing(FlowRule::priority);
        return Lists.newArrayList(flowNib.getFlowEntriesByState(in.deviceId(), FlowEntry.FlowEntryState.ADDED)
                .iterator()).stream()
                .filter(flowEntry -> {
                    return flowEntry.table().equals(tableId);
                })
                .filter(flowEntry -> {
                    return match(packet, flowEntry);
                }).max(comparator).orElse(null);
    }

    /**
     * Matches the packet with the given flow entry.
     *
     * @param packet    the packet to match
     * @param flowEntry the flow entry to match the packet against
     * @return true if the packet matches the flow.
     */
    private boolean match(TrafficSelector packet, FlowEntry flowEntry) {
        return flowEntry.selector().criteria().stream().allMatch(criterion -> {
            Criterion.Type type = criterion.type();
            //If the criterion has IP we need to do LPM to establish matching.
            if (type.equals(Criterion.Type.IPV4_SRC) || type.equals(Criterion.Type.IPV4_DST) ||
                    type.equals(Criterion.Type.IPV6_SRC) || type.equals(Criterion.Type.IPV6_DST)) {
                return matchIp(packet, (IPCriterion) criterion);
                //we check that the packet contains the criterion provided by the flow rule.
            } else if (type.equals(Criterion.Type.ETH_SRC_MASKED)) {
                return matchMac(packet, (EthCriterion) criterion, false);
            } else if (type.equals(Criterion.Type.ETH_DST_MASKED)) {
                return matchMac(packet, (EthCriterion) criterion, true);
            } else {
                return packet.criteria().contains(criterion);
            }
        });
    }

    /**
     * Checks if the packet has an dst or src IP and if that IP matches the subnet of the ip criterion.
     *
     * @param packet    the incoming packet
     * @param criterion the criterion to match
     * @return true if match
     */
    private boolean matchIp(TrafficSelector packet, IPCriterion criterion) {
        IPCriterion matchCriterion = (IPCriterion) packet.getCriterion(criterion.type());
        //if the packet does not have an IPv4 or IPv6 criterion we return true
        if (matchCriterion == null) {
            return false;
        }
        try {
            log.debug("Checking if {} is under {}", matchCriterion.ip(), criterion.ip());
            Subnet subnet = Subnet.createInstance(criterion.ip().toString());
            return subnet.isInSubnet(matchCriterion.ip().address().toInetAddress());
        } catch (UnknownHostException e) {
            return false;
        }
    }

    /**
     * Checks if the packet has a dst or src MAC and if that Mac matches the mask of the mac criterion.
     *
     * @param packet       the incoming packet
     * @param hitCriterion the criterion to match
     * @param dst          true if we are checking DST MAC
     * @return true if match
     */
    private boolean matchMac(TrafficSelector packet, EthCriterion hitCriterion, boolean dst) {
        //Packet can have only one EthCriterion
        EthCriterion matchCriterion;
        if (dst) {
            matchCriterion = (EthCriterion) packet.criteria().stream().filter(criterion1 -> {
                return criterion1.type().equals(Criterion.Type.ETH_DST_MASKED) ||
                        criterion1.type().equals(Criterion.Type.ETH_DST);
            }).findFirst().orElse(null);
        } else {
            matchCriterion = (EthCriterion) packet.criteria().stream().filter(criterion1 -> {
                return criterion1.type().equals(Criterion.Type.ETH_SRC_MASKED) ||
                        criterion1.type().equals(Criterion.Type.ETH_SRC);
            }).findFirst().orElse(null);
        }
        //if the packet does not have an ETH criterion we return true
        if (matchCriterion == null) {
            return true;
        }
        log.debug("Checking if {} is under {}/{}", matchCriterion.mac(), hitCriterion.mac(), hitCriterion.mask());
        return compareMac(matchCriterion.mac(), hitCriterion.mac(), hitCriterion.mask());
    }
}