/*
 * 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.p4runtime.ctl;

import com.google.common.collect.HashMultimap;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.Lists;
import com.google.common.collect.Multimap;
import com.google.protobuf.ByteString;
import com.google.protobuf.InvalidProtocolBufferException;
import io.grpc.Context;
import io.grpc.ManagedChannel;
import io.grpc.Status;
import io.grpc.StatusRuntimeException;
import io.grpc.stub.StreamObserver;
import org.apache.commons.lang3.tuple.ImmutablePair;
import org.onlab.osgi.DefaultServiceDirectory;
import org.onlab.util.SharedExecutors;
import org.onlab.util.Tools;
import org.onosproject.net.DeviceId;
import org.onosproject.net.pi.model.PiActionProfileId;
import org.onosproject.net.pi.model.PiCounterId;
import org.onosproject.net.pi.model.PiMeterId;
import org.onosproject.net.pi.model.PiPipeconf;
import org.onosproject.net.pi.model.PiTableId;
import org.onosproject.net.pi.runtime.PiActionGroup;
import org.onosproject.net.pi.runtime.PiActionGroupMember;
import org.onosproject.net.pi.runtime.PiCounterCellData;
import org.onosproject.net.pi.runtime.PiCounterCellId;
import org.onosproject.net.pi.runtime.PiEntity;
import org.onosproject.net.pi.runtime.PiMeterCellConfig;
import org.onosproject.net.pi.runtime.PiMeterCellId;
import org.onosproject.net.pi.runtime.PiMulticastGroupEntry;
import org.onosproject.net.pi.runtime.PiPacketOperation;
import org.onosproject.net.pi.runtime.PiTableEntry;
import org.onosproject.net.pi.service.PiPipeconfService;
import org.onosproject.p4runtime.api.P4RuntimeClient;
import org.onosproject.p4runtime.api.P4RuntimeEvent;
import org.slf4j.Logger;
import p4.config.v1.P4InfoOuterClass.P4Info;
import p4.tmp.P4Config;
import p4.v1.P4RuntimeGrpc;
import p4.v1.P4RuntimeOuterClass;
import p4.v1.P4RuntimeOuterClass.ActionProfileGroup;
import p4.v1.P4RuntimeOuterClass.ActionProfileMember;
import p4.v1.P4RuntimeOuterClass.Entity;
import p4.v1.P4RuntimeOuterClass.ForwardingPipelineConfig;
import p4.v1.P4RuntimeOuterClass.MasterArbitrationUpdate;
import p4.v1.P4RuntimeOuterClass.MulticastGroupEntry;
import p4.v1.P4RuntimeOuterClass.PacketReplicationEngineEntry;
import p4.v1.P4RuntimeOuterClass.ReadRequest;
import p4.v1.P4RuntimeOuterClass.ReadResponse;
import p4.v1.P4RuntimeOuterClass.SetForwardingPipelineConfigRequest;
import p4.v1.P4RuntimeOuterClass.StreamMessageRequest;
import p4.v1.P4RuntimeOuterClass.StreamMessageResponse;
import p4.v1.P4RuntimeOuterClass.TableEntry;
import p4.v1.P4RuntimeOuterClass.Uint128;
import p4.v1.P4RuntimeOuterClass.Update;
import p4.v1.P4RuntimeOuterClass.WriteRequest;

import java.math.BigInteger;
import java.nio.ByteBuffer;
import java.util.Collection;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Objects;
import java.util.Set;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.Executor;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
import java.util.function.Supplier;
import java.util.stream.Collectors;
import java.util.stream.StreamSupport;

import static com.google.common.base.Preconditions.checkNotNull;
import static java.lang.String.format;
import static org.onlab.util.Tools.groupedThreads;
import static org.slf4j.LoggerFactory.getLogger;
import static p4.v1.P4RuntimeOuterClass.Entity.EntityCase.ACTION_PROFILE_GROUP;
import static p4.v1.P4RuntimeOuterClass.Entity.EntityCase.ACTION_PROFILE_MEMBER;
import static p4.v1.P4RuntimeOuterClass.Entity.EntityCase.PACKET_REPLICATION_ENGINE_ENTRY;
import static p4.v1.P4RuntimeOuterClass.Entity.EntityCase.TABLE_ENTRY;
import static p4.v1.P4RuntimeOuterClass.PacketIn;
import static p4.v1.P4RuntimeOuterClass.PacketOut;
import static p4.v1.P4RuntimeOuterClass.PacketReplicationEngineEntry.TypeCase.MULTICAST_GROUP_ENTRY;
import static p4.v1.P4RuntimeOuterClass.SetForwardingPipelineConfigRequest.Action.VERIFY_AND_COMMIT;

/**
 * Implementation of a P4Runtime client.
 */
final class P4RuntimeClientImpl implements P4RuntimeClient {

    // Timeout in seconds to obtain the request lock.
    private static final int LOCK_TIMEOUT = 60;

    private static final Map<WriteOperationType, Update.Type> UPDATE_TYPES = ImmutableMap.of(
            WriteOperationType.UNSPECIFIED, Update.Type.UNSPECIFIED,
            WriteOperationType.INSERT, Update.Type.INSERT,
            WriteOperationType.MODIFY, Update.Type.MODIFY,
            WriteOperationType.DELETE, Update.Type.DELETE
    );

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

    private final Lock requestLock = new ReentrantLock();
    private final Context.CancellableContext cancellableContext =
            Context.current().withCancellation();

    private final DeviceId deviceId;
    private final long p4DeviceId;
    private final P4RuntimeControllerImpl controller;
    private final P4RuntimeGrpc.P4RuntimeBlockingStub blockingStub;
    private final ExecutorService executorService;
    private final Executor contextExecutor;
    private final StreamObserver<StreamMessageRequest> streamRequestObserver;

    // Used by this client for write requests.
    private Uint128 clientElectionId = Uint128.newBuilder().setLow(1).build();

    /**
     * Default constructor.
     *
     * @param deviceId   the ONOS device id
     * @param p4DeviceId the P4 device id
     * @param channel    gRPC channel
     * @param controller runtime client controller
     */
    P4RuntimeClientImpl(DeviceId deviceId, long p4DeviceId, ManagedChannel channel,
                        P4RuntimeControllerImpl controller) {
        this.deviceId = deviceId;
        this.p4DeviceId = p4DeviceId;
        this.controller = controller;
        this.executorService = Executors.newFixedThreadPool(15, groupedThreads(
                "onos-p4runtime-client-" + deviceId.toString(), "%d"));
        this.contextExecutor = this.cancellableContext.fixedContextExecutor(executorService);
        //TODO Investigate use of stub deadlines instead of timeout in supplyInContext
        this.blockingStub = P4RuntimeGrpc.newBlockingStub(channel);
        this.streamRequestObserver = P4RuntimeGrpc.newStub(channel)
                .streamChannel(new StreamChannelResponseObserver());
    }

    /**
     * Submits a task for async execution via the given executor. All tasks
     * submitted with this method will be executed sequentially.
     */
    private <U> CompletableFuture<U> supplyWithExecutor(
            Supplier<U> supplier, String opDescription, Executor executor) {
        return CompletableFuture.supplyAsync(() -> {
            // TODO: explore a more relaxed locking strategy.
            try {
                if (!requestLock.tryLock(LOCK_TIMEOUT, TimeUnit.SECONDS)) {
                    log.error("LOCK TIMEOUT! This is likely a deadlock, "
                                      + "please debug (executing {})",
                              opDescription);
                    throw new IllegalThreadStateException("Lock timeout");
                }
            } catch (InterruptedException e) {
                log.warn("Thread interrupted while waiting for lock (executing {})",
                         opDescription);
                throw new IllegalStateException(e);
            }
            try {
                return supplier.get();
            } catch (StatusRuntimeException ex) {
                log.warn("Unable to execute {} on {}: {}",
                         opDescription, deviceId, ex.toString());
                throw ex;
            } catch (Throwable ex) {
                log.error("Exception in client of {}, executing {}",
                          deviceId, opDescription, ex);
                throw ex;
            } finally {
                requestLock.unlock();
            }
        }, executor);
    }

    /**
     * Equivalent of supplyWithExecutor using the gRPC context executor of this
     * client, such that if the context is cancelled (e.g. client shutdown) the
     * RPC is automatically cancelled.
     */
    private <U> CompletableFuture<U> supplyInContext(
            Supplier<U> supplier, String opDescription) {
        return supplyWithExecutor(supplier, opDescription, contextExecutor);
    }

    @Override
    public CompletableFuture<Boolean> start() {
        return supplyInContext(this::doBecomeMaster,
                               "start-initStreamChannel");
    }

    @Override
    public CompletableFuture<Void> shutdown() {
        return supplyWithExecutor(this::doShutdown, "shutdown",
                                  SharedExecutors.getPoolThreadExecutor());
    }

    @Override
    public CompletableFuture<Boolean> becomeMaster() {
        return supplyInContext(this::doBecomeMaster,
                               "becomeMaster");
    }

    @Override
    public CompletableFuture<Boolean> setPipelineConfig(PiPipeconf pipeconf, ByteBuffer deviceData) {
        return supplyInContext(() -> doSetPipelineConfig(pipeconf, deviceData), "setPipelineConfig");
    }

    @Override
    public CompletableFuture<Boolean> writeTableEntries(Collection<PiTableEntry> piTableEntries,
                                                        WriteOperationType opType, PiPipeconf pipeconf) {
        return supplyInContext(() -> doWriteTableEntries(piTableEntries, opType, pipeconf),
                               "writeTableEntries-" + opType.name());
    }

    @Override
    public CompletableFuture<Collection<PiTableEntry>> dumpTable(PiTableId piTableId, PiPipeconf pipeconf) {
        return supplyInContext(() -> doDumpTable(piTableId, pipeconf), "dumpTable-" + piTableId);
    }

    @Override
    public CompletableFuture<Collection<PiTableEntry>> dumpAllTables(PiPipeconf pipeconf) {
        return supplyInContext(() -> doDumpTable(null, pipeconf), "dumpAllTables");
    }

    @Override
    public CompletableFuture<Boolean> packetOut(PiPacketOperation packet, PiPipeconf pipeconf) {
        return supplyInContext(() -> doPacketOut(packet, pipeconf), "packetOut");
    }

    @Override
    public CompletableFuture<Collection<PiCounterCellData>> readCounterCells(Set<PiCounterCellId> cellIds,
                                                                             PiPipeconf pipeconf) {
        return supplyInContext(() -> doReadCounterCells(cellIds, pipeconf),
                               "readCounterCells-" + cellIds.hashCode());
    }

    @Override
    public CompletableFuture<Collection<PiCounterCellData>> readAllCounterCells(Set<PiCounterId> counterIds,
                                                                                PiPipeconf pipeconf) {
        return supplyInContext(() -> doReadAllCounterCells(counterIds, pipeconf),
                               "readAllCounterCells-" + counterIds.hashCode());
    }

    @Override
    public CompletableFuture<Boolean> writeActionGroupMembers(PiActionProfileId profileId,
                                                              Collection<PiActionGroupMember> members,
                                                              WriteOperationType opType,
                                                              PiPipeconf pipeconf) {
        return supplyInContext(() -> doWriteActionGroupMembers(profileId, members, opType, pipeconf),
                               "writeActionGroupMembers-" + opType.name());
    }


    @Override
    public CompletableFuture<Boolean> writeActionGroup(PiActionGroup group,
                                                       WriteOperationType opType,
                                                       PiPipeconf pipeconf) {
        return supplyInContext(() -> doWriteActionGroup(group, opType, pipeconf),
                               "writeActionGroup-" + opType.name());
    }

    @Override
    public CompletableFuture<Collection<PiActionGroup>> dumpGroups(PiActionProfileId actionProfileId,
                                                                   PiPipeconf pipeconf) {
        return supplyInContext(() -> doDumpGroups(actionProfileId, pipeconf),
                               "dumpGroups-" + actionProfileId.id());
    }

    @Override
    public CompletableFuture<Boolean> writeMeterCells(Collection<PiMeterCellConfig> cellIds, PiPipeconf pipeconf) {

        return supplyInContext(() -> doWriteMeterCells(cellIds, pipeconf),
                               "writeMeterCells");
    }

    @Override
    public CompletableFuture<Boolean> writePreMulticastGroupEntries(
            Collection<PiMulticastGroupEntry> entries,
            WriteOperationType opType) {
        return supplyInContext(() -> doWriteMulticastGroupEntries(entries, opType),
                               "writePreMulticastGroupEntries");
    }

    @Override
    public CompletableFuture<Collection<PiMulticastGroupEntry>> readAllMulticastGroupEntries() {
        return supplyInContext(this::doReadAllMulticastGroupEntries,
                               "readAllMulticastGroupEntries");
    }

    @Override
    public CompletableFuture<Collection<PiMeterCellConfig>> readMeterCells(Set<PiMeterCellId> cellIds,
                                                                           PiPipeconf pipeconf) {
        return supplyInContext(() -> doReadMeterCells(cellIds, pipeconf),
                               "readMeterCells-" + cellIds.hashCode());
    }

    @Override
    public CompletableFuture<Collection<PiMeterCellConfig>> readAllMeterCells(Set<PiMeterId> meterIds,
                                                                              PiPipeconf pipeconf) {
        return supplyInContext(() -> doReadAllMeterCells(meterIds, pipeconf),
                               "readAllMeterCells-" + meterIds.hashCode());
    }

    /* Blocking method implementations below */

    private boolean doBecomeMaster() {
        final Uint128 newId = bigIntegerToUint128(
                controller.newMasterElectionId(deviceId));
        if (sendMasterArbitrationUpdate(newId)) {
            clientElectionId = newId;
            return true;
        }
        return false;
    }

    private boolean sendMasterArbitrationUpdate(Uint128 electionId) {
        log.info("Sending arbitration update to {}... electionId={}",
                 deviceId, uint128ToBigInteger(electionId));
        try {
            streamRequestObserver.onNext(
                    StreamMessageRequest.newBuilder()
                            .setArbitration(
                                    MasterArbitrationUpdate
                                            .newBuilder()
                                            .setDeviceId(p4DeviceId)
                                            .setElectionId(electionId)
                                            .build())
                            .build());
            return true;
        } catch (StatusRuntimeException e) {
            log.error("Unable to perform arbitration update on {}: {}", deviceId, e.getMessage());
        }
        return false;
    }

    private boolean doSetPipelineConfig(PiPipeconf pipeconf, ByteBuffer deviceData) {

        log.info("Setting pipeline config for {} to {}...", deviceId, pipeconf.id());

        checkNotNull(deviceData, "deviceData cannot be null");

        P4Info p4Info = PipeconfHelper.getP4Info(pipeconf);
        if (p4Info == null) {
            // Problem logged by PipeconfHelper.
            return false;
        }

        P4Config.P4DeviceConfig p4DeviceConfigMsg = P4Config.P4DeviceConfig
                .newBuilder()
                .setExtras(P4Config.P4DeviceConfig.Extras.getDefaultInstance())
                .setReassign(true)
                .setDeviceData(ByteString.copyFrom(deviceData))
                .build();

        ForwardingPipelineConfig pipelineConfig = ForwardingPipelineConfig
                .newBuilder()
                .setP4Info(p4Info)
                .setP4DeviceConfig(p4DeviceConfigMsg.toByteString())
                .build();

        SetForwardingPipelineConfigRequest request = SetForwardingPipelineConfigRequest
                .newBuilder()
                .setDeviceId(p4DeviceId)
                .setElectionId(clientElectionId)
                .setAction(VERIFY_AND_COMMIT)
                .setConfig(pipelineConfig)
                .build();

        try {
            this.blockingStub.setForwardingPipelineConfig(request);
            return true;
        } catch (StatusRuntimeException ex) {
            log.warn("Unable to set pipeline config on {}: {}", deviceId, ex.getMessage());
            return false;
        }
    }

    private boolean doWriteTableEntries(Collection<PiTableEntry> piTableEntries, WriteOperationType opType,
                                        PiPipeconf pipeconf) {
        if (piTableEntries.size() == 0) {
            return true;
        }

        Collection<Update> updateMsgs;
        try {
            updateMsgs = TableEntryEncoder.encode(piTableEntries, pipeconf)
                    .stream()
                    .map(tableEntryMsg ->
                                 Update.newBuilder()
                                         .setEntity(Entity.newBuilder()
                                                            .setTableEntry(tableEntryMsg)
                                                            .build())
                                         .setType(UPDATE_TYPES.get(opType))
                                         .build())
                    .collect(Collectors.toList());
        } catch (EncodeException e) {
            log.error("Unable to encode table entries, aborting {} operation: {}",
                      opType.name(), e.getMessage());
            return false;
        }

        return write(updateMsgs, piTableEntries, opType, "table entry");
    }

    private Collection<PiTableEntry> doDumpTable(PiTableId piTableId, PiPipeconf pipeconf) {

        log.debug("Dumping table {} from {} (pipeconf {})...", piTableId, deviceId, pipeconf.id());

        int tableId;
        if (piTableId == null) {
            // Dump all tables.
            tableId = 0;
        } else {
            P4InfoBrowser browser = PipeconfHelper.getP4InfoBrowser(pipeconf);
            if (browser == null) {
                log.warn("Unable to get a P4Info browser for pipeconf {}", pipeconf);
                return Collections.emptyList();
            }
            try {
                tableId = browser.tables().getByName(piTableId.id()).getPreamble().getId();
            } catch (P4InfoBrowser.NotFoundException e) {
                log.warn("Unable to dump table: {}", e.getMessage());
                return Collections.emptyList();
            }
        }

        ReadRequest requestMsg = ReadRequest.newBuilder()
                .setDeviceId(p4DeviceId)
                .addEntities(Entity.newBuilder()
                                     .setTableEntry(TableEntry.newBuilder()
                                                            .setTableId(tableId)
                                                            .build())
                                     .build())
                .build();

        Iterator<ReadResponse> responses;
        try {
            responses = blockingStub.read(requestMsg);
        } catch (StatusRuntimeException e) {
            log.warn("Unable to dump table {} from {}: {}", piTableId, deviceId, e.getMessage());
            return Collections.emptyList();
        }

        Iterable<ReadResponse> responseIterable = () -> responses;
        List<TableEntry> tableEntryMsgs = StreamSupport
                .stream(responseIterable.spliterator(), false)
                .map(ReadResponse::getEntitiesList)
                .flatMap(List::stream)
                .filter(entity -> entity.getEntityCase() == TABLE_ENTRY)
                .map(Entity::getTableEntry)
                .collect(Collectors.toList());

        log.debug("Retrieved {} entries from table {} on {}...", tableEntryMsgs.size(), piTableId, deviceId);

        return TableEntryEncoder.decode(tableEntryMsgs, pipeconf);
    }

    private boolean doPacketOut(PiPacketOperation packet, PiPipeconf pipeconf) {
        try {
            //encode the PiPacketOperation into a PacketOut
            PacketOut packetOut = PacketIOCodec.encodePacketOut(packet, pipeconf);

            //Build the request
            StreamMessageRequest packetOutRequest = StreamMessageRequest
                    .newBuilder().setPacket(packetOut).build();

            //Send the request
            streamRequestObserver.onNext(packetOutRequest);

        } catch (P4InfoBrowser.NotFoundException e) {
            log.error("Cant find expected metadata in p4Info file. {}", e.getMessage());
            log.debug("Exception", e);
            return false;
        }
        return true;
    }

    private void doPacketIn(PacketIn packetInMsg) {

        // Retrieve the pipeconf for this client's device.
        PiPipeconfService pipeconfService = DefaultServiceDirectory.getService(PiPipeconfService.class);
        if (pipeconfService == null) {
            throw new IllegalStateException("PiPipeconfService is null. Can't handle packet in.");
        }
        final PiPipeconf pipeconf;
        if (pipeconfService.ofDevice(deviceId).isPresent() &&
                pipeconfService.getPipeconf(pipeconfService.ofDevice(deviceId).get()).isPresent()) {
            pipeconf = pipeconfService.getPipeconf(pipeconfService.ofDevice(deviceId).get()).get();
        } else {
            log.warn("Unable to get pipeconf of {}. Can't handle packet in", deviceId);
            return;
        }
        // Decode packet message and post event.
        PiPacketOperation packetOperation = PacketIOCodec.decodePacketIn(packetInMsg, pipeconf, deviceId);
        PacketInEvent packetInEventSubject = new PacketInEvent(deviceId, packetOperation);
        P4RuntimeEvent event = new P4RuntimeEvent(P4RuntimeEvent.Type.PACKET_IN, packetInEventSubject);
        log.debug("Received packet in: {}", event);
        controller.postEvent(event);
    }

    private void doArbitrationResponse(MasterArbitrationUpdate msg) {
        // From the spec...
        // - Election_id: The stream RPC with the highest election_id is the
        // master. Switch populates with the highest election ID it
        // has received from all connected controllers.
        // - Status: Switch populates this with OK for the client that is the
        // master, and with an error status for all other connected clients (at
        // every mastership change).
        if (!msg.hasElectionId() || !msg.hasStatus()) {
            return;
        }
        final boolean isMaster = msg.getStatus().getCode() == Status.OK.getCode().value();
        log.info("Received arbitration update from {}: isMaster={}, electionId={}",
                 deviceId, isMaster, uint128ToBigInteger(msg.getElectionId()));
        controller.postEvent(new P4RuntimeEvent(
                P4RuntimeEvent.Type.ARBITRATION_RESPONSE,
                new ArbitrationResponse(deviceId, isMaster)));
    }

    private Collection<PiCounterCellData> doReadAllCounterCells(
            Collection<PiCounterId> counterIds, PiPipeconf pipeconf) {
        return doReadCounterEntities(
                CounterEntryCodec.readAllCellsEntities(counterIds, pipeconf),
                pipeconf);
    }

    private Collection<PiCounterCellData> doReadCounterCells(
            Collection<PiCounterCellId> cellIds, PiPipeconf pipeconf) {
        return doReadCounterEntities(
                CounterEntryCodec.encodePiCounterCellIds(cellIds, pipeconf),
                pipeconf);
    }

    private Collection<PiCounterCellData> doReadCounterEntities(
            Collection<Entity> counterEntities, PiPipeconf pipeconf) {

        if (counterEntities.size() == 0) {
            return Collections.emptyList();
        }

        final ReadRequest request = ReadRequest.newBuilder()
                .setDeviceId(p4DeviceId)
                .addAllEntities(counterEntities)
                .build();

        final Iterable<ReadResponse> responses;
        try {
            responses = () -> blockingStub.read(request);
        } catch (StatusRuntimeException e) {
            log.warn("Unable to read counter cells from {}: {}", deviceId, e.getMessage());
            return Collections.emptyList();
        }

        List<Entity> entities = StreamSupport.stream(responses.spliterator(), false)
                .map(ReadResponse::getEntitiesList)
                .flatMap(List::stream)
                .collect(Collectors.toList());

        return CounterEntryCodec.decodeCounterEntities(entities, pipeconf);
    }

    private boolean doWriteActionGroupMembers(PiActionProfileId profileId, Collection<PiActionGroupMember> members,
                                              WriteOperationType opType, PiPipeconf pipeconf) {
        final Collection<ActionProfileMember> actionProfileMembers = Lists.newArrayList();

        for (PiActionGroupMember member : members) {
            try {
                actionProfileMembers.add(ActionProfileMemberEncoder.encode(profileId, member, pipeconf));
            } catch (EncodeException | P4InfoBrowser.NotFoundException e) {
                log.warn("Unable to encode group member, aborting {} operation: {} [{}]",
                         opType.name(), e.getMessage(), member.toString());
                return false;
            }
        }

        final Collection<Update> updateMsgs = actionProfileMembers.stream()
                .map(actionProfileMember ->
                             Update.newBuilder()
                                     .setEntity(Entity.newBuilder()
                                                        .setActionProfileMember(actionProfileMember)
                                                        .build())
                                     .setType(UPDATE_TYPES.get(opType))
                                     .build())
                .collect(Collectors.toList());

        if (updateMsgs.size() == 0) {
            // Nothing to update.
            return true;
        }

        return write(updateMsgs, members, opType, "group member");
    }

    private Collection<PiActionGroup> doDumpGroups(PiActionProfileId piActionProfileId, PiPipeconf pipeconf) {
        log.debug("Dumping groups from action profile {} from {} (pipeconf {})...",
                  piActionProfileId.id(), deviceId, pipeconf.id());

        final P4InfoBrowser browser = PipeconfHelper.getP4InfoBrowser(pipeconf);
        if (browser == null) {
            log.warn("Unable to get a P4Info browser for pipeconf {}, aborting dump action profile", pipeconf);
            return Collections.emptySet();
        }

        final int actionProfileId;
        try {
            actionProfileId = browser
                    .actionProfiles()
                    .getByName(piActionProfileId.id())
                    .getPreamble()
                    .getId();
        } catch (P4InfoBrowser.NotFoundException e) {
            log.warn("Unable to dump groups: {}", e.getMessage());
            return Collections.emptySet();
        }

        // Prepare read request to read all groups from the given action profile.
        final ReadRequest groupRequestMsg = ReadRequest.newBuilder()
                .setDeviceId(p4DeviceId)
                .addEntities(Entity.newBuilder()
                                     .setActionProfileGroup(
                                             ActionProfileGroup.newBuilder()
                                                     .setActionProfileId(actionProfileId)
                                                     .build())
                                     .build())
                .build();

        // Read groups.
        final Iterator<ReadResponse> groupResponses;
        try {
            groupResponses = blockingStub.read(groupRequestMsg);
        } catch (StatusRuntimeException e) {
            log.warn("Unable to dump action profile {} from {}: {}", piActionProfileId, deviceId, e.getMessage());
            return Collections.emptySet();
        }

        final List<ActionProfileGroup> groupMsgs = Tools.stream(() -> groupResponses)
                .map(ReadResponse::getEntitiesList)
                .flatMap(List::stream)
                .filter(entity -> entity.getEntityCase() == ACTION_PROFILE_GROUP)
                .map(Entity::getActionProfileGroup)
                .collect(Collectors.toList());

        log.debug("Retrieved {} groups from action profile {} on {}...",
                  groupMsgs.size(), piActionProfileId.id(), deviceId);

        // Returned groups contain only a minimal description of their members.
        // We need to issue a new request to get the full description of each member.

        // Keep a map of all member IDs for each group ID, will need it later.
        final Multimap<Integer, Integer> groupIdToMemberIdsMap = HashMultimap.create();
        groupMsgs.forEach(g -> groupIdToMemberIdsMap.putAll(
                g.getGroupId(),
                g.getMembersList().stream()
                        .map(ActionProfileGroup.Member::getMemberId)
                        .collect(Collectors.toList())));

        // Prepare one big read request to read all members in one shot.
        final Set<Entity> entityMsgs = groupMsgs.stream()
                .flatMap(g -> g.getMembersList().stream())
                .map(ActionProfileGroup.Member::getMemberId)
                // Prevent issuing many read requests for the same member.
                .distinct()
                .map(id -> ActionProfileMember.newBuilder()
                        .setActionProfileId(actionProfileId)
                        .setMemberId(id)
                        .build())
                .map(m -> Entity.newBuilder()
                        .setActionProfileMember(m)
                        .build())
                .collect(Collectors.toSet());
        final ReadRequest memberRequestMsg = ReadRequest.newBuilder().setDeviceId(p4DeviceId)
                .addAllEntities(entityMsgs)
                .build();

        // Read members.
        final Iterator<ReadResponse> memberResponses;
        try {
            memberResponses = blockingStub.read(memberRequestMsg);
        } catch (StatusRuntimeException e) {
            log.warn("Unable to read members of action profile {} from {}: {}",
                     piActionProfileId, deviceId, e.getMessage());
            return Collections.emptyList();
        }

        final Multimap<Integer, ActionProfileMember> groupIdToMembersMap = HashMultimap.create();
        Tools.stream(() -> memberResponses)
                .map(ReadResponse::getEntitiesList)
                .flatMap(List::stream)
                .filter(e -> e.getEntityCase() == ACTION_PROFILE_MEMBER)
                .map(Entity::getActionProfileMember)
                .forEach(member -> groupIdToMemberIdsMap.asMap()
                        // Get all group IDs that contain this member.
                        .entrySet()
                        .stream()
                        .filter(entry -> entry.getValue().contains(member.getMemberId()))
                        .map(Map.Entry::getKey)
                        .forEach(gid -> groupIdToMembersMap.put(gid, member)));

        log.debug("Retrieved {} group members from action profile {} on {}...",
                  groupIdToMembersMap.size(), piActionProfileId.id(), deviceId);

        return groupMsgs.stream()
                .map(groupMsg -> {
                    try {
                        return ActionProfileGroupEncoder.decode(groupMsg,
                                                                groupIdToMembersMap.get(groupMsg.getGroupId()),
                                                                pipeconf);
                    } catch (P4InfoBrowser.NotFoundException | EncodeException e) {
                        log.warn("Unable to decode group: {}\n {}", e.getMessage(), groupMsg);
                        return null;
                    }
                })
                .filter(Objects::nonNull)
                .collect(Collectors.toList());
    }

    private boolean doWriteActionGroup(PiActionGroup group, WriteOperationType opType, PiPipeconf pipeconf) {
        final ActionProfileGroup actionProfileGroup;
        try {
            actionProfileGroup = ActionProfileGroupEncoder.encode(group, pipeconf);
        } catch (EncodeException | P4InfoBrowser.NotFoundException e) {
            log.warn("Unable to encode group, aborting {} operation: {}", e.getMessage(), opType.name());
            return false;
        }

        final Update updateMsg = Update.newBuilder()
                .setEntity(Entity.newBuilder()
                                   .setActionProfileGroup(actionProfileGroup)
                                   .build())
                .setType(UPDATE_TYPES.get(opType))
                .build();

        return write(Collections.singleton(updateMsg), Collections.singleton(group),
                     opType, "group");
    }

    private Collection<PiMeterCellConfig> doReadAllMeterCells(
            Collection<PiMeterId> meterIds, PiPipeconf pipeconf) {
        return doReadMeterEntities(MeterEntryCodec.readAllCellsEntities(
                meterIds, pipeconf), pipeconf);
    }

    private Collection<PiMeterCellConfig> doReadMeterCells(
            Collection<PiMeterCellId> cellIds, PiPipeconf pipeconf) {

        final Collection<PiMeterCellConfig> piMeterCellConfigs = cellIds.stream()
                .map(cellId -> PiMeterCellConfig.builder()
                        .withMeterCellId(cellId)
                        .build())
                .collect(Collectors.toList());

        return doReadMeterEntities(MeterEntryCodec.encodePiMeterCellConfigs(
                piMeterCellConfigs, pipeconf), pipeconf);
    }

    private Collection<PiMeterCellConfig> doReadMeterEntities(
            Collection<Entity> entitiesToRead, PiPipeconf pipeconf) {

        if (entitiesToRead.size() == 0) {
            return Collections.emptyList();
        }

        final ReadRequest request = ReadRequest.newBuilder()
                .setDeviceId(p4DeviceId)
                .addAllEntities(entitiesToRead)
                .build();

        final Iterable<ReadResponse> responses;
        try {
            responses = () -> blockingStub.read(request);
        } catch (StatusRuntimeException e) {
            log.warn("Unable to read meter cells: {}", e.getMessage());
            log.debug("exception", e);
            return Collections.emptyList();
        }

        List<Entity> responseEntities = StreamSupport
                .stream(responses.spliterator(), false)
                .map(ReadResponse::getEntitiesList)
                .flatMap(List::stream)
                .collect(Collectors.toList());

        return MeterEntryCodec.decodeMeterEntities(responseEntities, pipeconf);
    }

    private boolean doWriteMeterCells(Collection<PiMeterCellConfig> cellConfigs, PiPipeconf pipeconf) {

        Collection<Update> updateMsgs = MeterEntryCodec.encodePiMeterCellConfigs(cellConfigs, pipeconf)
                .stream()
                .map(meterEntryMsg ->
                             Update.newBuilder()
                                     .setEntity(meterEntryMsg)
                                     .setType(UPDATE_TYPES.get(WriteOperationType.MODIFY))
                                     .build())
                .collect(Collectors.toList());

        if (updateMsgs.size() == 0) {
            return true;
        }

        return write(updateMsgs, cellConfigs, WriteOperationType.MODIFY, "meter cell config");
    }

    private boolean doWriteMulticastGroupEntries(
            Collection<PiMulticastGroupEntry> entries,
            WriteOperationType opType) {

        final List<Update> updateMsgs = entries.stream()
                .map(MulticastGroupEntryCodec::encode)
                .map(mcMsg -> PacketReplicationEngineEntry.newBuilder()
                        .setMulticastGroupEntry(mcMsg)
                        .build())
                .map(preMsg -> Entity.newBuilder()
                        .setPacketReplicationEngineEntry(preMsg)
                        .build())
                .map(entityMsg -> Update.newBuilder()
                        .setEntity(entityMsg)
                        .setType(UPDATE_TYPES.get(opType))
                        .build())
                .collect(Collectors.toList());
        return write(updateMsgs, entries, opType, "multicast group entry");
    }

    private Collection<PiMulticastGroupEntry> doReadAllMulticastGroupEntries() {

        final Entity entity = Entity.newBuilder()
                .setPacketReplicationEngineEntry(
                        PacketReplicationEngineEntry.newBuilder()
                                .setMulticastGroupEntry(
                                        MulticastGroupEntry.newBuilder()
                                                .build())
                                .build())
                .build();

        final ReadRequest req = ReadRequest.newBuilder()
                .setDeviceId(p4DeviceId)
                .addEntities(entity)
                .build();

        Iterator<ReadResponse> responses;
        try {
            responses = blockingStub.read(req);
        } catch (StatusRuntimeException e) {
            log.warn("Unable to read multicast group entries from {}: {}", deviceId, e.getMessage());
            return Collections.emptyList();
        }

        Iterable<ReadResponse> responseIterable = () -> responses;
        final List<PiMulticastGroupEntry> mcEntries = StreamSupport
                .stream(responseIterable.spliterator(), false)
                .map(ReadResponse::getEntitiesList)
                .flatMap(List::stream)
                .filter(e -> e.getEntityCase()
                        .equals(PACKET_REPLICATION_ENGINE_ENTRY))
                .map(Entity::getPacketReplicationEngineEntry)
                .filter(e -> e.getTypeCase().equals(MULTICAST_GROUP_ENTRY))
                .map(PacketReplicationEngineEntry::getMulticastGroupEntry)
                .map(MulticastGroupEntryCodec::decode)
                .collect(Collectors.toList());

        log.debug("Retrieved {} multicast group entries from {}...",
                  mcEntries.size(), deviceId);

        return mcEntries;
    }

    private <E extends PiEntity> boolean write(Collection<Update> updates,
                                               Collection<E> writeEntities,
                                               WriteOperationType opType,
                                               String entryType) {
        try {
            blockingStub.write(writeRequest(updates));
            return true;
        } catch (StatusRuntimeException e) {
            checkAndLogWriteErrors(writeEntities, e, opType, entryType);
            return false;
        }
    }

    private WriteRequest writeRequest(Iterable<Update> updateMsgs) {
        return WriteRequest.newBuilder()
                .setDeviceId(p4DeviceId)
                .setElectionId(clientElectionId)
                .addAllUpdates(updateMsgs)
                .build();
    }

    private Void doShutdown() {
        log.info("Shutting down client for {}...", deviceId);
        if (streamRequestObserver != null) {
            try {
                streamRequestObserver.onCompleted();
            } catch (IllegalStateException e) {
                // Thrown if stream channel is already completed. Can ignore.
                log.debug("Ignored expection: {}", e);
            }
            cancellableContext.cancel(new InterruptedException(
                    "Requested client shutdown"));
        }
        this.executorService.shutdown();
        try {
            executorService.awaitTermination(5, TimeUnit.SECONDS);
        } catch (InterruptedException e) {
            log.warn("Executor service didn't shutdown in time.");
            Thread.currentThread().interrupt();
        }
        return null;
    }

    private <E extends PiEntity> void checkAndLogWriteErrors(
            Collection<E> writeEntities, StatusRuntimeException ex,
            WriteOperationType opType, String entryType) {

        checkGrpcException(ex);

        List<P4RuntimeOuterClass.Error> errors = null;
        String description = null;
        try {
            errors = extractWriteErrorDetails(ex);
        } catch (InvalidProtocolBufferException e) {
            description = ex.getStatus().getDescription();
        }

        log.warn("Unable to {} {} {}(s) on {}: {}{} (detailed errors might be logged below)",
                 opType.name(), writeEntities.size(), entryType, deviceId,
                 ex.getStatus().getCode().name(),
                 description == null ? "" : " - " + description);

        if (errors == null || errors.isEmpty()) {
            return;
        }

        // FIXME: we are assuming entities is an ordered collection, e.g. a list,
        // and that errors are reported in the same order as the corresponding
        // written entity. Write RPC methods should be refactored to accept an
        // order list of entities, instead of a collection.
        if (errors.size() == writeEntities.size()) {
            Iterator<E> entityIterator = writeEntities.iterator();
            errors.stream()
                    .map(e -> ImmutablePair.of(e, entityIterator.next()))
                    .filter(p -> p.left.getCanonicalCode() != Status.OK.getCode().value())
                    .forEach(p -> log.warn("Unable to {} {}: {} [{}]",
                                           opType.name(), entryType, parseP4Error(p.getLeft()),
                                           p.getRight().toString()));
        } else {
            log.error("Unable to reconcile error details to updates " +
                              "(sent {} updates, but device returned {} errors)",
                      entryType, writeEntities.size(), errors.size());
            errors.stream()
                    .filter(err -> err.getCanonicalCode() != Status.OK.getCode().value())
                    .forEach(err -> log.warn("Unable to {} {} (unknown): {}",
                                             opType.name(), entryType, parseP4Error(err)));
        }
    }

    private List<P4RuntimeOuterClass.Error> extractWriteErrorDetails(
            StatusRuntimeException ex) throws InvalidProtocolBufferException {
        String statusString = ex.getStatus().getDescription();
        if (statusString == null) {
            return Collections.emptyList();
        }
        com.google.rpc.Status status = com.google.rpc.Status
                .parseFrom(statusString.getBytes());
        return status.getDetailsList().stream()
                .map(any -> {
                    try {
                        return any.unpack(P4RuntimeOuterClass.Error.class);
                    } catch (InvalidProtocolBufferException e) {
                        log.warn("Unable to unpack P4Runtime Error: {}",
                                 any.toString());
                        return null;
                    }
                })
                .filter(Objects::nonNull)
                .collect(Collectors.toList());

    }

    private String parseP4Error(P4RuntimeOuterClass.Error err) {
        return format("%s %s (%s code %d)%s",
                      Status.fromCodeValue(err.getCanonicalCode()),
                      err.getMessage(),
                      err.getSpace(),
                      err.getCode(),
                      err.hasDetails() ? "\n" + err.getDetails().toString() : "");
    }

    private void checkGrpcException(StatusRuntimeException ex) {
        switch (ex.getStatus().getCode()) {
            case OK:
                break;
            case CANCELLED:
                break;
            case UNKNOWN:
                break;
            case INVALID_ARGUMENT:
                break;
            case DEADLINE_EXCEEDED:
                break;
            case NOT_FOUND:
                break;
            case ALREADY_EXISTS:
                break;
            case PERMISSION_DENIED:
                // Notify upper layers that this node is not master.
                controller.postEvent(new P4RuntimeEvent(
                        P4RuntimeEvent.Type.ARBITRATION_RESPONSE,
                        new ArbitrationResponse(deviceId, false)));
                break;
            case RESOURCE_EXHAUSTED:
                break;
            case FAILED_PRECONDITION:
                break;
            case ABORTED:
                break;
            case OUT_OF_RANGE:
                break;
            case UNIMPLEMENTED:
                break;
            case INTERNAL:
                break;
            case UNAVAILABLE:
                // Channel might be closed.
                controller.postEvent(new P4RuntimeEvent(
                        P4RuntimeEvent.Type.CHANNEL_EVENT,
                        new ChannelEvent(deviceId, ChannelEvent.Type.ERROR)));
                break;
            case DATA_LOSS:
                break;
            case UNAUTHENTICATED:
                break;
            default:
                break;
        }
    }

    private Uint128 bigIntegerToUint128(BigInteger value) {
        final byte[] arr = value.toByteArray();
        final ByteBuffer bb = ByteBuffer.allocate(Long.BYTES * 2)
                .put(new byte[Long.BYTES * 2 - arr.length])
                .put(arr);
        bb.rewind();
        return Uint128.newBuilder()
                .setHigh(bb.getLong())
                .setLow(bb.getLong())
                .build();
    }

    private BigInteger uint128ToBigInteger(Uint128 value) {
        return new BigInteger(
                ByteBuffer.allocate(Long.BYTES * 2)
                        .putLong(value.getHigh())
                        .putLong(value.getLow())
                        .array());
    }

    /**
     * Handles messages received from the device on the stream channel.
     */
    private class StreamChannelResponseObserver
            implements StreamObserver<StreamMessageResponse> {

        @Override
        public void onNext(StreamMessageResponse message) {
            executorService.submit(() -> doNext(message));
        }

        private void doNext(StreamMessageResponse message) {
            try {
                log.debug("Received message on stream channel from {}: {}",
                          deviceId, message.getUpdateCase());
                switch (message.getUpdateCase()) {
                    case PACKET:
                        doPacketIn(message.getPacket());
                        return;
                    case ARBITRATION:
                        doArbitrationResponse(message.getArbitration());
                        return;
                    default:
                        log.warn("Unrecognized stream message from {}: {}",
                                 deviceId, message.getUpdateCase());
                }
            } catch (Throwable ex) {
                log.error("Exception while processing stream message from {}",
                          deviceId, ex);
            }
        }

        @Override
        public void onError(Throwable throwable) {
            log.warn("Error on stream channel for {}: {}",
                     deviceId, Status.fromThrowable(throwable));
            controller.postEvent(new P4RuntimeEvent(
                    P4RuntimeEvent.Type.CHANNEL_EVENT,
                    new ChannelEvent(deviceId, ChannelEvent.Type.ERROR)));
        }

        @Override
        public void onCompleted() {
            log.warn("Stream channel for {} has completed", deviceId);
            controller.postEvent(new P4RuntimeEvent(
                    P4RuntimeEvent.Type.CHANNEL_EVENT,
                    new ChannelEvent(deviceId, ChannelEvent.Type.CLOSED)));
        }
    }
}