/*
 * Copyright 2018-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.openstacktelemetry.impl;

import com.google.common.collect.Sets;
import org.apache.felix.scr.annotations.Activate;
import org.apache.felix.scr.annotations.Component;
import org.apache.felix.scr.annotations.Deactivate;
import org.apache.felix.scr.annotations.Modified;
import org.apache.felix.scr.annotations.Property;
import org.apache.felix.scr.annotations.Reference;
import org.apache.felix.scr.annotations.ReferenceCardinality;
import org.apache.felix.scr.annotations.Service;
import org.onlab.packet.IpAddress;
import org.onlab.packet.IpPrefix;
import org.onlab.packet.MacAddress;
import org.onlab.packet.VlanId;
import org.onlab.util.SharedScheduledExecutors;
import org.onosproject.cfg.ComponentConfigService;
import org.onosproject.core.ApplicationId;
import org.onosproject.core.CoreService;
import org.onosproject.mastership.MastershipService;
import org.onosproject.net.DeviceId;
import org.onosproject.net.Host;
import org.onosproject.net.PortNumber;
import org.onosproject.net.device.DeviceService;
import org.onosproject.net.device.PortStatistics;
import org.onosproject.net.flow.DefaultFlowRule;
import org.onosproject.net.flow.DefaultTrafficSelector;
import org.onosproject.net.flow.DefaultTrafficTreatment;
import org.onosproject.net.flow.FlowEntry;
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.IndexTableId;
import org.onosproject.net.flow.TrafficSelector;
import org.onosproject.net.flow.TrafficTreatment;
import org.onosproject.net.flow.criteria.IPCriterion;
import org.onosproject.net.flow.criteria.IPProtocolCriterion;
import org.onosproject.net.flow.criteria.TcpPortCriterion;
import org.onosproject.net.flow.criteria.UdpPortCriterion;
import org.onosproject.net.host.HostService;
import org.onosproject.openstacknetworking.api.InstancePort;
import org.onosproject.openstacknetworking.api.InstancePortService;
import org.onosproject.openstacknetworking.api.OpenstackNetworkService;
import org.onosproject.openstacknode.api.OpenstackNode;
import org.onosproject.openstacknode.api.OpenstackNodeService;
import org.onosproject.openstacktelemetry.api.FlowInfo;
import org.onosproject.openstacktelemetry.api.OpenstackTelemetryService;
import org.onosproject.openstacktelemetry.api.StatsFlowRule;
import org.onosproject.openstacktelemetry.api.StatsFlowRuleAdminService;
import org.onosproject.openstacktelemetry.api.StatsInfo;
import org.osgi.service.component.ComponentContext;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.Dictionary;
import java.util.List;
import java.util.Optional;
import java.util.Set;
import java.util.concurrent.ScheduledFuture;
import java.util.concurrent.TimeUnit;
import java.util.stream.Collectors;

import static org.onlab.packet.Ethernet.TYPE_IPV4;
import static org.onlab.packet.IPv4.PROTOCOL_TCP;
import static org.onlab.packet.IPv4.PROTOCOL_UDP;
import static org.onosproject.net.flow.criteria.Criterion.Type.IPV4_DST;
import static org.onosproject.net.flow.criteria.Criterion.Type.IPV4_SRC;
import static org.onosproject.net.flow.criteria.Criterion.Type.IP_PROTO;
import static org.onosproject.net.flow.criteria.Criterion.Type.TCP_DST;
import static org.onosproject.net.flow.criteria.Criterion.Type.TCP_SRC;
import static org.onosproject.net.flow.criteria.Criterion.Type.UDP_DST;
import static org.onosproject.net.flow.criteria.Criterion.Type.UDP_SRC;
import static org.onosproject.openstacknetworking.api.Constants.STAT_FLAT_OUTBOUND_TABLE;
import static org.onosproject.openstacknetworking.api.Constants.STAT_INBOUND_TABLE;
import static org.onosproject.openstacknetworking.api.Constants.STAT_OUTBOUND_TABLE;
import static org.onosproject.openstacknetworking.api.Constants.VTAP_FLAT_OUTBOUND_TABLE;
import static org.onosproject.openstacknetworking.api.Constants.VTAP_INBOUND_TABLE;
import static org.onosproject.openstacknetworking.api.Constants.VTAP_OUTBOUND_TABLE;
import static org.onosproject.openstacknode.api.OpenstackNode.NodeType.COMPUTE;
import static org.onosproject.openstacktelemetry.api.Constants.FLAT;
import static org.onosproject.openstacktelemetry.api.Constants.OPENSTACK_TELEMETRY_APP_ID;
import static org.onosproject.openstacktelemetry.api.Constants.VLAN;
import static org.onosproject.openstacktelemetry.api.Constants.VXLAN;
import static org.onosproject.openstacktelemetry.util.OpenstackTelemetryUtil.getBooleanProperty;

/**
 * Flow rule manager for network statistics of a VM.
 */
@Component(immediate = true)
@Service
public class StatsFlowRuleManager implements StatsFlowRuleAdminService {

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

    private static final byte FLOW_TYPE_SONA = 1; // VLAN

    private static final long MILLISECONDS = 1000L;
    private static final long INITIAL_DELAY = 5L;
    private static final long REFRESH_INTERVAL = 5L;
    private static final TimeUnit TIME_UNIT_SECOND = TimeUnit.SECONDS;

    private static final String REVERSE_PATH_STATS = "reversePathStats";
    private static final String EGRESS_STATS = "egressStats";
    private static final String PORT_STATS = "portStats";

    private static final boolean DEFAULT_REVERSE_PATH_STATS = false;
    private static final boolean DEFAULT_EGRESS_STATS = false;
    private static final boolean DEFAULT_PORT_STATS = true;

    private static final String MAC_NOT_NULL = "MAC should not be null";

    private static final String ARBITRARY_IP = "0.0.0.0/32";
    private static final int ARBITRARY_LENGTH = 32;
    private static final String ARBITRARY_MAC = "00:00:00:00:00:00";
    private static final int ARBITRARY_IN_INTF = 0;
    private static final int ARBITRARY_OUT_INTF = 0;

    private static final boolean RECOVER_FROM_FAILURE = true;

    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
    protected CoreService coreService;

    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
    protected FlowRuleService flowRuleService;

    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
    protected HostService hostService;

    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
    protected DeviceService deviceService;

    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
    protected ComponentConfigService componentConfigService;

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

    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
    protected OpenstackNetworkService osNetworkService;

    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
    protected InstancePortService instPortService;

    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
    protected OpenstackNodeService osNodeService;

    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
    protected OpenstackTelemetryService telemetryService;

    @Property(name = REVERSE_PATH_STATS, boolValue = DEFAULT_REVERSE_PATH_STATS,
            label = "A flag which indicates whether to install the rules for " +
                    "collecting the flow-based stats for reversed path.")
    private boolean reversePathStats = DEFAULT_REVERSE_PATH_STATS;

    @Property(name = EGRESS_STATS, boolValue = DEFAULT_EGRESS_STATS,
            label = "A flag which indicates whether to install the rules for " +
                    "collecting the flow-based stats for egress port.")
    private boolean egressStats = DEFAULT_EGRESS_STATS;

    @Property(name = PORT_STATS, boolValue = DEFAULT_PORT_STATS,
            label = "A flag which indicates whether to collect port TX & RX stats.")
    private boolean portStats = DEFAULT_PORT_STATS;

    private ApplicationId appId;
    private TelemetryCollector collector;
    private ScheduledFuture result;

    private final Set<FlowInfo> gFlowInfoSet = Sets.newHashSet();

    private static final int SOURCE_ID = 1;
    private static final int TARGET_ID = 2;
    private static final int PRIORITY_BASE = 10000;
    private static final int METRIC_PRIORITY_SOURCE  = SOURCE_ID * PRIORITY_BASE;
    private static final int METRIC_PRIORITY_TARGET  = TARGET_ID * PRIORITY_BASE;

    private static final MacAddress NO_HOST_MAC = MacAddress.valueOf("00:00:00:00:00:00");

    @Activate
    protected void activate() {
        appId = coreService.registerApplication(OPENSTACK_TELEMETRY_APP_ID);
        componentConfigService.registerProperties(getClass());
        start();

        log.info("Started");
    }

    @Deactivate
    protected void deactivate() {
        componentConfigService.unregisterProperties(getClass(), false);
        flowRuleService.removeFlowRulesById(appId);
        stop();

        log.info("Stopped");
    }

    @Modified
    protected void modified(ComponentContext context) {
        readComponentConfiguration(context);

        log.info("Modified");
    }

    @Override
    public void start() {
        log.info("Start publishing thread");
        collector = new TelemetryCollector();

        result = SharedScheduledExecutors.getSingleThreadExecutor()
                    .scheduleAtFixedRate(collector, INITIAL_DELAY,
                        REFRESH_INTERVAL, TIME_UNIT_SECOND, RECOVER_FROM_FAILURE);
    }

    @Override
    public void stop() {
        log.info("Stop data publishing thread");
        result.cancel(true);
        collector = null;
    }

    @Override
    public void createStatFlowRule(StatsFlowRule statsFlowRule) {

        setStatFlowRule(statsFlowRule, true);
    }

    @Override
    public void deleteStatFlowRule(StatsFlowRule statsFlowRule) {

        setStatFlowRule(statsFlowRule, false);
    }

    /**
     * Gets a set of the flow infos.
     *
     * @return a set of flow infos
     */
    @Override
    public Set<FlowInfo> getFlowInfos() {
        Set<FlowInfo> flowInfos = Sets.newConcurrentHashSet();

        // obtain all flow rule entries installed by telemetry app
        for (FlowEntry entry : flowRuleService.getFlowEntriesById(appId)) {
            FlowInfo.Builder fBuilder = new DefaultFlowInfo.DefaultBuilder();
            TrafficSelector selector = entry.selector();

            IPCriterion srcIp = (IPCriterion) selector.getCriterion(IPV4_SRC);
            IPCriterion dstIp = (IPCriterion) selector.getCriterion(IPV4_DST);
            IPProtocolCriterion ipProtocol =
                    (IPProtocolCriterion) selector.getCriterion(IP_PROTO);

            log.debug("[FlowInfo]  TableID:{}  SRC_IP:{}  DST_IP:{}  Pkt:{}  Byte:{}",
                    ((IndexTableId) entry.table()).id(),
                    srcIp.ip().toString(),
                    dstIp.ip().toString(),
                    entry.packets(),
                    entry.bytes());

            fBuilder.withFlowType(FLOW_TYPE_SONA)
                    .withSrcIp(srcIp.ip())
                    .withDstIp(dstIp.ip());

            if (ipProtocol != null) {
                fBuilder.withProtocol((byte) ipProtocol.protocol());

                if (ipProtocol.protocol() == PROTOCOL_TCP) {
                    TcpPortCriterion tcpSrc =
                            (TcpPortCriterion) selector.getCriterion(TCP_SRC);
                    TcpPortCriterion tcpDst =
                            (TcpPortCriterion) selector.getCriterion(TCP_DST);

                    log.debug("TCP SRC Port: {}, DST Port: {}",
                            tcpSrc.tcpPort().toInt(),
                            tcpDst.tcpPort().toInt());

                    fBuilder.withSrcPort(tcpSrc.tcpPort());
                    fBuilder.withDstPort(tcpDst.tcpPort());

                } else if (ipProtocol.protocol() == PROTOCOL_UDP) {

                    UdpPortCriterion udpSrc =
                            (UdpPortCriterion) selector.getCriterion(UDP_SRC);
                    UdpPortCriterion udpDst =
                            (UdpPortCriterion) selector.getCriterion(UDP_DST);

                    log.debug("UDP SRC Port: {}, DST Port: {}",
                                                    udpSrc.udpPort().toInt(),
                                                    udpDst.udpPort().toInt());

                    fBuilder.withSrcPort(udpSrc.udpPort());
                    fBuilder.withDstPort(udpDst.udpPort());
                } else {
                    log.debug("Other protocol: {}", ipProtocol.protocol());
                }
            }

            fBuilder.withSrcMac(getMacAddress(srcIp.ip().address()))
                    .withDstMac(getMacAddress(dstIp.ip().address()))
                    .withInputInterfaceId(getInterfaceId(srcIp.ip().address()))
                    .withOutputInterfaceId(getInterfaceId(dstIp.ip().address()))
                    .withVlanId(getVlanId(srcIp.ip().address()))
                    .withDeviceId(entry.deviceId());

            StatsInfo.Builder sBuilder = new DefaultStatsInfo.DefaultBuilder();

            // TODO: need to collect error and drop packets stats
            // TODO: need to make the refresh interval configurable
            sBuilder.withStartupTime(System.currentTimeMillis())
                    .withFstPktArrTime(System.currentTimeMillis())
                    .withLstPktOffset((int) (REFRESH_INTERVAL * MILLISECONDS))
                    .withCurrAccPkts((int) entry.packets())
                    .withCurrAccBytes(entry.bytes())
                    .withErrorPkts((short) 0)
                    .withDropPkts((short) 0);

            fBuilder.withStatsInfo(sBuilder.build());

            FlowInfo flowInfo = mergeFlowInfo(fBuilder.build(), fBuilder, sBuilder);

            flowInfos.add(flowInfo);

            log.debug("FlowInfo: \n{}", flowInfo.toString());
        }

        return flowInfos;
    }

    /**
     * Gets a set of flow infos by referring to destination VM port.
     *
     * @return flow infos
     */
    private Set<FlowInfo> getDstPortBasedFlowInfos() {
        Set<FlowInfo> flowInfos = Sets.newConcurrentHashSet();
        Set<PortNumber> instPortNums = instPortService.instancePorts()
                                                .stream()
                                                .map(InstancePort::portNumber)
                                                .collect(Collectors.toSet());
        Set<DeviceId> deviceIds = osNodeService.completeNodes(COMPUTE)
                                                .stream()
                                                .map(OpenstackNode::intgBridge)
                                                .collect(Collectors.toSet());

        deviceIds.forEach(d -> {
            List<PortStatistics> stats =
                                deviceService.getPortStatistics(d)
                                .stream()
                                .filter(s -> instPortNums.contains(s.portNumber()))
                                .collect(Collectors.toList());

            stats.forEach(s -> {
                InstancePort instPort = getInstancePort(d, s.portNumber());
                flowInfos.add(buildTxPortInfo(instPort, s));
                flowInfos.add(buildRxPortInfo(instPort, s));
            });
        });

        return flowInfos;
    }

    /**
     * Obtains the flow info generated by TX port.
     *
     * @param instPort instance port
     * @param stat port statistics
     * @return flow info
     */
    private FlowInfo buildTxPortInfo(InstancePort instPort, PortStatistics stat) {
        FlowInfo.Builder fBuilder = new DefaultFlowInfo.DefaultBuilder();

        fBuilder.withFlowType(FLOW_TYPE_SONA)
                .withSrcIp(IpPrefix.valueOf(instPort.ipAddress(), ARBITRARY_LENGTH))
                .withDstIp(IpPrefix.valueOf(ARBITRARY_IP))
                .withSrcMac(instPort.macAddress())
                .withDstMac(MacAddress.valueOf(ARBITRARY_MAC))
                .withDeviceId(instPort.deviceId())
                .withInputInterfaceId(ARBITRARY_IN_INTF)
                .withOutputInterfaceId(ARBITRARY_OUT_INTF)
                .withVlanId(VlanId.vlanId());

        StatsInfo.Builder sBuilder = new DefaultStatsInfo.DefaultBuilder();
        sBuilder.withStartupTime(System.currentTimeMillis())
                .withFstPktArrTime(System.currentTimeMillis())
                .withLstPktOffset((int) (REFRESH_INTERVAL * MILLISECONDS))
                .withCurrAccPkts((int) stat.packetsSent())
                .withCurrAccBytes(stat.bytesSent())
                .withErrorPkts((short) stat.packetsTxErrors())
                .withDropPkts((short) stat.packetsTxDropped());

        fBuilder.withStatsInfo(sBuilder.build());

        return mergeFlowInfo(fBuilder.build(), fBuilder, sBuilder);
    }

    /**
     * Obtains the flow info generated by RX port.
     *
     * @param instPort instance port
     * @param stat port statistics
     * @return flow info
     */
    private FlowInfo buildRxPortInfo(InstancePort instPort, PortStatistics stat) {
        FlowInfo.Builder fBuilder = new DefaultFlowInfo.DefaultBuilder();

        fBuilder.withFlowType(FLOW_TYPE_SONA)
                .withSrcIp(IpPrefix.valueOf(ARBITRARY_IP))
                .withDstIp(IpPrefix.valueOf(instPort.ipAddress(), ARBITRARY_LENGTH))
                .withSrcMac(MacAddress.valueOf(ARBITRARY_MAC))
                .withDstMac(instPort.macAddress())
                .withDeviceId(instPort.deviceId())
                .withInputInterfaceId(ARBITRARY_IN_INTF)
                .withOutputInterfaceId(ARBITRARY_OUT_INTF)
                .withVlanId(VlanId.vlanId());

        StatsInfo.Builder sBuilder = new DefaultStatsInfo.DefaultBuilder();
        sBuilder.withStartupTime(System.currentTimeMillis())
                .withFstPktArrTime(System.currentTimeMillis())
                .withLstPktOffset((int) (REFRESH_INTERVAL * MILLISECONDS))
                .withCurrAccPkts((int) stat.packetsReceived())
                .withCurrAccBytes(stat.bytesReceived())
                .withErrorPkts((short) stat.packetsRxErrors())
                .withDropPkts((short) stat.packetsRxDropped());

        fBuilder.withStatsInfo(sBuilder.build());

        return mergeFlowInfo(fBuilder.build(), fBuilder, sBuilder);
    }

    /**
     * Obtains instance port which associated with the given device identifier
     * and port number.
     *
     * @param deviceId      device identifier
     * @param portNumber    port number
     * @return instance port
     */
    private InstancePort getInstancePort(DeviceId deviceId, PortNumber portNumber) {
        return instPortService.instancePorts().stream()
                                .filter(p -> p.deviceId().equals(deviceId))
                                .filter(p -> p.portNumber().equals(portNumber))
                                .findFirst().orElse(null);
    }

    private void connectTables(DeviceId deviceId, int fromTable, int toTable,
                               StatsFlowRule statsFlowRule, int rulePriority,
                               boolean install) {

        log.debug("Table Transition: {} -> {}", fromTable, toTable);
        int srcPrefixLength = statsFlowRule.srcIpPrefix().prefixLength();
        int dstPrefixLength = statsFlowRule.dstIpPrefix().prefixLength();
        int prefixLength = rulePriority + srcPrefixLength + dstPrefixLength;
        byte protocol = statsFlowRule.ipProtocol();

        TrafficSelector.Builder selectorBuilder =
                DefaultTrafficSelector.builder()
                        .matchEthType(TYPE_IPV4)
                        .matchIPSrc(statsFlowRule.srcIpPrefix())
                        .matchIPDst(statsFlowRule.dstIpPrefix());

        if (protocol == PROTOCOL_TCP) {
            selectorBuilder = selectorBuilder
                    .matchIPProtocol(statsFlowRule.ipProtocol())
                    .matchTcpSrc(statsFlowRule.srcTpPort())
                    .matchTcpDst(statsFlowRule.dstTpPort());

        } else if (protocol == PROTOCOL_UDP) {
            selectorBuilder = selectorBuilder
                    .matchIPProtocol(statsFlowRule.ipProtocol())
                    .matchUdpSrc(statsFlowRule.srcTpPort())
                    .matchUdpDst(statsFlowRule.dstTpPort());
        } else {
            log.warn("Unsupported protocol {}", statsFlowRule.ipProtocol());
        }

        TrafficTreatment.Builder treatmentBuilder = DefaultTrafficTreatment.builder();

        treatmentBuilder.transition(toTable);

        FlowRule flowRule = DefaultFlowRule.builder()
                .forDevice(deviceId)
                .withSelector(selectorBuilder.build())
                .withTreatment(treatmentBuilder.build())
                .withPriority(prefixLength)
                .fromApp(appId)
                .makePermanent()
                .forTable(fromTable)
                .build();

        applyRule(flowRule, install);
    }

    /**
     * Installs stats related flow rule to switch.
     *
     * @param flowRule flow rule
     * @param install flag to install or not
     */
    private void applyRule(FlowRule flowRule, boolean install) {
        FlowRuleOperations.Builder flowOpsBuilder = FlowRuleOperations.builder();
        flowOpsBuilder = install ?
                flowOpsBuilder.add(flowRule) : flowOpsBuilder.remove(flowRule);

        flowRuleService.apply(flowOpsBuilder.build(new FlowRuleOperationsContext() {
            @Override
            public void onSuccess(FlowRuleOperations ops) {
                log.debug("Install rules for telemetry stats: \n {}",
                                                                ops.toString());
            }

            @Override
            public void onError(FlowRuleOperations ops) {
                log.debug("Failed to install rules for telemetry stats: \n {}",
                                                                ops.toString());
            }
        }));
    }

    /**
     * Merges old FlowInfo.StatsInfo and current FlowInfo.StatsInfo.
     *
     * @param flowInfo current FlowInfo object
     * @param fBuilder Builder for FlowInfo
     * @param sBuilder Builder for StatsInfo
     * @return Merged FlowInfo object
     */
    private FlowInfo mergeFlowInfo(FlowInfo flowInfo,
                                   FlowInfo.Builder fBuilder,
                                   StatsInfo.Builder sBuilder) {
        for (FlowInfo gFlowInfo : gFlowInfoSet) {
            log.debug("Old FlowInfo:\n{}", gFlowInfo.toString());
            if (gFlowInfo.roughEquals(flowInfo)) {

                // Get old StatsInfo object and merge the value to current object.
                StatsInfo oldStatsInfo = gFlowInfo.statsInfo();
                sBuilder.withPrevAccPkts(oldStatsInfo.currAccPkts());
                sBuilder.withPrevAccBytes(oldStatsInfo.currAccBytes());
                FlowInfo newFlowInfo = fBuilder.withStatsInfo(sBuilder.build())
                        .build();

                gFlowInfoSet.remove(gFlowInfo);
                gFlowInfoSet.add(newFlowInfo);
                log.debug("Old FlowInfo found, Merge this {}", newFlowInfo.toString());
                return newFlowInfo;
            }
        }

        // No such record, then build the FlowInfo object and return this object.
        log.debug("No FlowInfo found, add new FlowInfo {}", flowInfo.toString());
        FlowInfo newFlowInfo = fBuilder.withStatsInfo(sBuilder.build()).build();
        gFlowInfoSet.add(newFlowInfo);
        return newFlowInfo;
    }

    /**
     * Installs flow rules for collecting both normal and reverse path flow stats.
     *
     * @param statsFlowRule flow rule used for collecting stats
     * @param install flow rule installation flag
     */
    private void setStatFlowRule(StatsFlowRule statsFlowRule, boolean install) {
        setStatFlowRuleBase(statsFlowRule, install);

        // if reverse path stats is enabled, we will install flow rules for
        // collecting reverse path vFlow stats
        if (reversePathStats) {
            StatsFlowRule reverseFlowRule = DefaultStatsFlowRule.builder()
                                            .srcIpPrefix(statsFlowRule.dstIpPrefix())
                                            .dstIpPrefix(statsFlowRule.srcIpPrefix())
                                            .ipProtocol(statsFlowRule.ipProtocol())
                                            .srcTpPort(statsFlowRule.dstTpPort())
                                            .dstTpPort(statsFlowRule.srcTpPort())
                                            .build();
            setStatFlowRuleBase(reverseFlowRule, install);
        }
    }

    /**
     * A base method which is for installing flow rules for collecting stats.
     *
     * @param statsFlowRule flow rule used for collecting stats
     * @param install flow rule installation flag
     */
    private void setStatFlowRuleBase(StatsFlowRule statsFlowRule, boolean install) {

        IpPrefix srcIp = statsFlowRule.srcIpPrefix();
        IpPrefix dstIp = statsFlowRule.dstIpPrefix();
        DeviceId srcDeviceId = getDeviceId(srcIp.address());
        DeviceId dstDeviceId = getDeviceId(dstIp.address());

        if (srcDeviceId == null && dstDeviceId == null) {
            return;
        }

        if (srcDeviceId != null) {
            connectTables(srcDeviceId, STAT_INBOUND_TABLE, VTAP_INBOUND_TABLE,
                    statsFlowRule, METRIC_PRIORITY_SOURCE, install);

            if (install) {
                log.info("Install ingress stat flow rule for SrcIp:{} DstIp:{}",
                                            srcIp.toString(), dstIp.toString());
            } else {
                log.info("Remove ingress stat flow rule for SrcIp:{} DstIp:{}",
                                            srcIp.toString(), dstIp.toString());
            }
        }

        Set<IpPrefix> vxlanIps = osNetworkService.getFixedIpsByNetworkType(VXLAN);
        Set<IpPrefix> vlanIps = osNetworkService.getFixedIpsByNetworkType(VLAN);
        Set<IpPrefix> flatIps = osNetworkService.getFixedIpsByNetworkType(FLAT);

        int fromTable, toTable;

        if (dstDeviceId != null && egressStats) {

            IpPrefix dstIpPrefix = statsFlowRule.dstIpPrefix();

            if (vxlanIps.contains(dstIpPrefix) || vlanIps.contains(dstIpPrefix)) {
                fromTable = STAT_OUTBOUND_TABLE;
                toTable = VTAP_OUTBOUND_TABLE;
            } else if (flatIps.contains(dstIpPrefix)) {
                fromTable = STAT_FLAT_OUTBOUND_TABLE;
                toTable = VTAP_FLAT_OUTBOUND_TABLE;
            } else {
                return;
            }

            connectTables(dstDeviceId, fromTable, toTable,
                    statsFlowRule, METRIC_PRIORITY_TARGET, install);

            if (install) {
                log.info("Install egress stat flow rule for SrcIp:{} DstIp:{}",
                                            srcIp.toString(), dstIp.toString());
            } else {
                log.info("Remove egress stat flow rule for SrcIp:{} DstIp:{}",
                                            srcIp.toString(), dstIp.toString());
            }
        }
    }

    /**
     * Get Device ID which the VM is located.
     *
     * @param ipAddress IP Address of host
     * @return Device ID
     */
    private DeviceId getDeviceId(IpAddress ipAddress) {
        if (!hostService.getHostsByIp(ipAddress).isEmpty()) {
            Optional<Host> host = hostService.getHostsByIp(ipAddress).stream().findAny();
            return host.map(host1 -> host1.location().deviceId()).orElse(null);
        } else {
            log.debug("No DeviceID is associated to {}", ipAddress.toString());
            return null;
        }
    }

    /**
     * Get VLAN ID with respect to IP Address.
     *
     * @param ipAddress IP Address of host
     * @return VLAN ID
     */
    private VlanId getVlanId(IpAddress ipAddress) {
        if (!hostService.getHostsByIp(ipAddress).isEmpty()) {
            Host host = hostService.getHostsByIp(ipAddress).stream().findAny().get();
            return host.vlan();
        }
        return VlanId.vlanId();
    }

    /**
     * Get Interface ID of Switch which is connected to a host.
     *
     * @param ipAddress IP Address of host
     * @return Interface ID of Switch
     */
    private int getInterfaceId(IpAddress ipAddress) {
        if (!hostService.getHostsByIp(ipAddress).isEmpty()) {
            Host host = hostService.getHostsByIp(ipAddress).stream().findAny().get();
            return (int) host.location().port().toLong();
        }
        return -1;
    }

    /**
     * Get MAC Address of host.
     *
     * @param ipAddress IP Address of host
     * @return MAC Address of host
     */
    private MacAddress getMacAddress(IpAddress ipAddress) {
        if (!hostService.getHostsByIp(ipAddress).isEmpty()) {
            Host host = hostService.getHostsByIp(ipAddress).stream().findAny().get();
            return host.mac();
        }

        return NO_HOST_MAC;
    }

    /**
     * Extracts properties from the component configuration context.
     *
     * @param context the component context
     */
    private void readComponentConfiguration(ComponentContext context) {
        Dictionary<?, ?> properties = context.getProperties();

        Boolean reversePathStatsConfigured =
                            getBooleanProperty(properties, REVERSE_PATH_STATS);
        if (reversePathStatsConfigured == null) {
            reversePathStats = DEFAULT_REVERSE_PATH_STATS;
            log.info("Reversed path stats flag is NOT " +
                     "configured, default value is {}", reversePathStats);
        } else {
            reversePathStats = reversePathStatsConfigured;
            log.info("Configured. Reversed path stats flag is {}", reversePathStats);
        }

        Boolean egressStatsConfigured = getBooleanProperty(properties, EGRESS_STATS);
        if (egressStatsConfigured == null) {
            egressStats = DEFAULT_EGRESS_STATS;
            log.info("Egress stats flag is NOT " +
                     "configured, default value is {}", egressStats);
        } else {
            egressStats = egressStatsConfigured;
            log.info("Configured. Egress stats flag is {}", egressStats);
        }

        Boolean portStatsConfigured = getBooleanProperty(properties, PORT_STATS);
        if (portStatsConfigured == null) {
            portStats = DEFAULT_PORT_STATS;
            log.info("Port stats flag is NOT " +
                    "configured, default value is {}", portStats);
        } else {
            portStats = portStatsConfigured;
            log.info("Configured. Port stats flag is {}", portStats);
        }
    }

    private class TelemetryCollector implements Runnable {
        @Override
        public void run() {
            Set<FlowInfo> filteredFlowInfos = Sets.newConcurrentHashSet();

            // we only let the master controller of the device where the
            // stats flow rules are installed send stats message
            getFlowInfos().forEach(f -> {
                if (checkSrcDstLocalMaster(f)) {
                    filteredFlowInfos.add(f);
                }
            });

            // we only let the master controller of the device where the port
            // is located to send stats message
            if (portStats) {
                getDstPortBasedFlowInfos().forEach(f -> {
                    if (checkSrcDstLocalMaster(f)) {
                        filteredFlowInfos.add(f);
                    }
                });
            }

            telemetryService.publish(filteredFlowInfos);
        }

        private boolean checkSrcDstLocalMaster(FlowInfo info) {
            DeviceId srcDeviceId = getDeviceId(info.srcIp().address());
            DeviceId dstDeviceId = getDeviceId(info.dstIp().address());

            boolean isSrcLocalMaster = srcDeviceId != null &&
                    mastershipService.isLocalMaster(srcDeviceId);
            boolean isDstLocalMaster = dstDeviceId != null &&
                    mastershipService.isLocalMaster(dstDeviceId);

            return isSrcLocalMaster || isDstLocalMaster;
        }
    }
}