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/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.apache.ratis.protocol;

import org.apache.ratis.proto.RaftProtos.DataStreamRequestTypeProto;
import org.apache.ratis.proto.RaftProtos.ForwardRequestTypeProto;
import org.apache.ratis.proto.RaftProtos.MessageStreamRequestTypeProto;
import org.apache.ratis.proto.RaftProtos.RaftClientRequestProto.TypeCase;
import org.apache.ratis.proto.RaftProtos.ReadRequestTypeProto;
import org.apache.ratis.proto.RaftProtos.ReplicationLevel;
import org.apache.ratis.proto.RaftProtos.SlidingWindowEntry;
import org.apache.ratis.proto.RaftProtos.StaleReadRequestTypeProto;
import org.apache.ratis.proto.RaftProtos.WatchRequestTypeProto;
import org.apache.ratis.proto.RaftProtos.WriteRequestTypeProto;
import org.apache.ratis.util.Preconditions;
import org.apache.ratis.util.ProtoUtils;

import java.util.Collections;
import java.util.EnumMap;
import java.util.Map;
import java.util.Objects;
import java.util.Optional;

/**
 * Request from client to server
 */
public class RaftClientRequest extends RaftClientMessage {
  private static final Type DATA_STREAM_DEFAULT = new Type(DataStreamRequestTypeProto.getDefaultInstance());
  private static final Type FORWARD_DEFAULT = new Type(ForwardRequestTypeProto.getDefaultInstance());
  private static final Type WATCH_DEFAULT = new Type(
      WatchRequestTypeProto.newBuilder().setIndex(0L).setReplication(ReplicationLevel.MAJORITY).build());

  private static final Type READ_AFTER_WRITE_CONSISTENT_DEFAULT
      = new Type(ReadRequestTypeProto.newBuilder().setReadAfterWriteConsistent(true).build());
  private static final Type READ_DEFAULT = new Type(ReadRequestTypeProto.getDefaultInstance());
  private static final Type READ_NONLINEARIZABLE_DEFAULT
      = new Type(ReadRequestTypeProto.newBuilder().setPreferNonLinearizable(true).build());
  private static final Type STALE_READ_DEFAULT = new Type(StaleReadRequestTypeProto.getDefaultInstance());

  private static final Map WRITE_REQUEST_TYPES;

  static {
    final EnumMap map = new EnumMap<>(ReplicationLevel.class);
    for(ReplicationLevel replication : ReplicationLevel.values()) {
      if (replication == ReplicationLevel.UNRECOGNIZED) {
        continue;
      }
      final WriteRequestTypeProto write = WriteRequestTypeProto.newBuilder().setReplication(replication).build();
      map.put(replication, new Type(write));
    }
    WRITE_REQUEST_TYPES = Collections.unmodifiableMap(map);
  }

  public static Type writeRequestType(ReplicationLevel replication) {
    return WRITE_REQUEST_TYPES.get(replication);
  }

  public static Type writeRequestType() {
    return writeRequestType(ReplicationLevel.MAJORITY);
  }

  public static Type dataStreamRequestType() {
    return DATA_STREAM_DEFAULT;
  }

  public static Type forwardRequestType() {
    return FORWARD_DEFAULT;
  }

  public static Type messageStreamRequestType(long streamId, long messageId, boolean endOfRequest) {
    return new Type(MessageStreamRequestTypeProto.newBuilder()
        .setStreamId(streamId)
        .setMessageId(messageId)
        .setEndOfRequest(endOfRequest)
        .build());
  }

  public static Type readAfterWriteConsistentRequestType() {
    return READ_AFTER_WRITE_CONSISTENT_DEFAULT;
  }

  public static Type readRequestType() {
    return READ_DEFAULT;
  }

  public static Type readRequestType(boolean nonLinearizable) {
    return nonLinearizable? READ_NONLINEARIZABLE_DEFAULT: readRequestType();
  }

  public static Type staleReadRequestType(long minIndex) {
    return minIndex == 0L? STALE_READ_DEFAULT
        : new Type(StaleReadRequestTypeProto.newBuilder().setMinIndex(minIndex).build());
  }

  public static Type watchRequestType() {
    return WATCH_DEFAULT;
  }
  public static Type watchRequestType(long index, ReplicationLevel replication) {
    return new Type(WatchRequestTypeProto.newBuilder().setIndex(index).setReplication(replication).build());
  }

  /** The type of {@link RaftClientRequest} corresponding to {@link TypeCase}. */
  public static final class Type {
    public static Type valueOf(WriteRequestTypeProto write) {
      return writeRequestType(write.getReplication());
    }

    public static Type valueOf(DataStreamRequestTypeProto dataStream) {
      return DATA_STREAM_DEFAULT;
    }

    public static Type valueOf(ForwardRequestTypeProto forward) {
      return FORWARD_DEFAULT;
    }

    public static Type valueOf(ReadRequestTypeProto read) {
      return read.getPreferNonLinearizable()? READ_NONLINEARIZABLE_DEFAULT
          : read.getReadAfterWriteConsistent()? READ_AFTER_WRITE_CONSISTENT_DEFAULT
          : READ_DEFAULT;
    }

    public static Type valueOf(StaleReadRequestTypeProto staleRead) {
      return staleRead.getMinIndex() == 0? STALE_READ_DEFAULT: new Type(staleRead);
    }

    public static Type valueOf(WatchRequestTypeProto watch) {
      return watchRequestType(watch.getIndex(), watch.getReplication());
    }

    public static Type valueOf(MessageStreamRequestTypeProto messageStream) {
      return messageStreamRequestType(
          messageStream.getStreamId(), messageStream.getMessageId(), messageStream.getEndOfRequest());
    }

    /**
     * The type case of the proto.
     * Only the corresponding proto (must be non-null) is used.
     * The other protos are ignored.
     */
    private final TypeCase typeCase;
    private final Object proto;

    private Type(TypeCase typeCase, Object proto) {
      this.typeCase = Objects.requireNonNull(typeCase, "typeCase == null");
      this.proto = Objects.requireNonNull(proto, "proto == null");
    }

    private Type(WriteRequestTypeProto write) {
      this(TypeCase.WRITE, write);
    }

    private Type(DataStreamRequestTypeProto dataStream) {
      this(TypeCase.DATASTREAM, dataStream);
    }

    private Type(ForwardRequestTypeProto forward) {
      this(TypeCase.FORWARD, forward);
    }

    private Type(MessageStreamRequestTypeProto messageStream) {
      this(TypeCase.MESSAGESTREAM, messageStream);
    }

    private Type(ReadRequestTypeProto read) {
      this(TypeCase.READ, read);
    }

    private Type(StaleReadRequestTypeProto staleRead) {
      this(TypeCase.STALEREAD, staleRead);
    }

    private Type(WatchRequestTypeProto watch) {
      this(TypeCase.WATCH, watch);
    }

    public boolean is(TypeCase t) {
      return getTypeCase() == t;
    }

    public boolean isReadOnly() {
      switch (getTypeCase()) {
        case READ:
        case STALEREAD:
        case WATCH:
          return true;
        case WRITE:
        case MESSAGESTREAM:
        case DATASTREAM:
        case FORWARD:
          return false;
        default:
          throw new IllegalStateException("Unexpected type case: " + getTypeCase());
      }
    }

    public TypeCase getTypeCase() {
      return typeCase;
    }

    private void assertType(TypeCase expected) {
      Preconditions.assertSame(expected, getTypeCase(), "type");
    }

    public WriteRequestTypeProto getWrite() {
      assertType(TypeCase.WRITE);
      return (WriteRequestTypeProto)proto;
    }

    public DataStreamRequestTypeProto getDataStream() {
      assertType(TypeCase.DATASTREAM);
      return (DataStreamRequestTypeProto)proto;
    }

    public ForwardRequestTypeProto getForward() {
      assertType(TypeCase.FORWARD);
      return (ForwardRequestTypeProto)proto;
    }

    public MessageStreamRequestTypeProto getMessageStream() {
      assertType(TypeCase.MESSAGESTREAM);
      return (MessageStreamRequestTypeProto)proto;
    }

    public ReadRequestTypeProto getRead() {
      assertType(TypeCase.READ);
      return (ReadRequestTypeProto)proto;
    }

    public StaleReadRequestTypeProto getStaleRead() {
      assertType(TypeCase.STALEREAD);
      return (StaleReadRequestTypeProto)proto;
    }

    public WatchRequestTypeProto getWatch() {
      assertType(TypeCase.WATCH);
      return (WatchRequestTypeProto)proto;
    }

    public static String toString(ReplicationLevel replication) {
      return replication == ReplicationLevel.MAJORITY? "": "-" + replication;
    }

    public static String toString(WatchRequestTypeProto w) {
      return "Watch" + toString(w.getReplication()) + "(" + w.getIndex() + ")";
    }

    public static String toString(MessageStreamRequestTypeProto s) {
      return "MessageStream" + s.getStreamId() + "-" + s.getMessageId() + (s.getEndOfRequest()? "-eor": "");
    }

    @Override
    public String toString() {
      switch (typeCase) {
        case WRITE:
          return "RW";
        case DATASTREAM:
          return "DataStream";
        case FORWARD:
          return "Forward";
        case MESSAGESTREAM:
          return toString(getMessageStream());
        case READ:
          final ReadRequestTypeProto read = getRead();
          return read.getReadAfterWriteConsistent()? "RaW"
              : read.getPreferNonLinearizable()? "RO(pNL)"
              : "RO";
        case STALEREAD:
          return "StaleRead(" + getStaleRead().getMinIndex() + ")";
        case WATCH:
          return toString(getWatch());
        default:
          throw new IllegalStateException("Unexpected request type: " + typeCase);
      }
    }
  }

  /**
   * To build {@link RaftClientRequest}
   */
  public static class Builder {
    private ClientId clientId;
    private RaftPeerId serverId;
    private RaftGroupId groupId;
    private long callId;
    private boolean toLeader;
    private Iterable repliedCallIds = Collections.emptyList();

    private Message message;
    private Type type;
    private SlidingWindowEntry slidingWindowEntry;
    private RoutingTable routingTable;
    private long timeoutMs;

    public RaftClientRequest build() {
      return new RaftClientRequest(this);
    }

    public Builder setClientId(ClientId clientId) {
      this.clientId = clientId;
      return this;
    }

    public Builder setLeaderId(RaftPeerId leaderId) {
      this.serverId = leaderId;
      this.toLeader = true;
      return this;
    }

    public Builder setServerId(RaftPeerId serverId) {
      this.serverId = serverId;
      this.toLeader = false;
      return this;
    }

    public Builder setGroupId(RaftGroupId groupId) {
      this.groupId = groupId;
      return this;
    }

    public Builder setCallId(long callId) {
      this.callId = callId;
      return this;
    }

    public Builder setRepliedCallIds(Iterable repliedCallIds) {
      this.repliedCallIds = repliedCallIds;
      return this;
    }

    public Builder setMessage(Message message) {
      this.message = message;
      return this;
    }

    public Builder setType(Type type) {
      this.type = type;
      return this;
    }

    public Builder setSlidingWindowEntry(SlidingWindowEntry slidingWindowEntry) {
      this.slidingWindowEntry = slidingWindowEntry;
      return this;
    }

    public Builder setRoutingTable(RoutingTable routingTable) {
      this.routingTable = routingTable;
      return this;
    }

    public Builder setTimeoutMs(long timeoutMs) {
      this.timeoutMs = timeoutMs;
      return this;
    }
  }

  public static Builder newBuilder() {
    return new Builder();
  }

  /** Convert the given request to a write request with the given message. */
  public static RaftClientRequest toWriteRequest(RaftClientRequest r, Message message) {
    return RaftClientRequest.newBuilder()
        .setClientId(r.getClientId())
        .setServerId(r.getServerId())
        .setGroupId(r.getRaftGroupId())
        .setCallId(r.getCallId())
        .setMessage(message)
        .setType(RaftClientRequest.writeRequestType())
        .setSlidingWindowEntry(r.getSlidingWindowEntry())
        .build();
  }

  private final Message message;
  private final Type type;

  private final Iterable repliedCallIds;
  private final SlidingWindowEntry slidingWindowEntry;

  private final RoutingTable routingTable;

  private final long timeoutMs;

  private final boolean toLeader;

  /** Construct a request for sending to the given server. */
  protected RaftClientRequest(ClientId clientId, RaftPeerId serverId, RaftGroupId groupId, long callId, Type type) {
    this(newBuilder()
        .setClientId(clientId)
        .setServerId(serverId)
        .setGroupId(groupId)
        .setCallId(callId)
        .setType(type));
  }

  /** Construct a request for sending to the Leader. */
  protected RaftClientRequest(ClientId clientId, RaftPeerId leaderId, RaftGroupId groupId, long callId, Type type,
      long timeoutMs) {
    this(newBuilder()
        .setClientId(clientId)
        .setLeaderId(leaderId)
        .setGroupId(groupId)
        .setCallId(callId)
        .setType(type)
        .setTimeoutMs(timeoutMs));
  }

  private RaftClientRequest(Builder b) {
    super(b.clientId, b.serverId, b.groupId, b.callId);
    this.toLeader = b.toLeader;

    this.message = b.message;
    this.type = b.type;
    this.repliedCallIds = Optional.ofNullable(b.repliedCallIds).orElseGet(Collections::emptyList);
    this.slidingWindowEntry = b.slidingWindowEntry;
    this.routingTable = b.routingTable;
    this.timeoutMs = b.timeoutMs;
  }

  @Override
  public final boolean isRequest() {
    return true;
  }

  public boolean isToLeader() {
    return toLeader;
  }

  public Iterable getRepliedCallIds() {
    return repliedCallIds;
  }

  public SlidingWindowEntry getSlidingWindowEntry() {
    return slidingWindowEntry;
  }

  public Message getMessage() {
    return message;
  }

  public Type getType() {
    return type;
  }

  public boolean is(TypeCase typeCase) {
    return getType().is(typeCase);
  }

  public boolean isReadOnly() {
    return getType().isReadOnly();
  }

  public RoutingTable getRoutingTable() {
    return routingTable;
  }

  public long getTimeoutMs() {
    return timeoutMs;
  }

  @Override
  public String toString() {
    return super.toString() + ", seq=" + ProtoUtils.toString(slidingWindowEntry) + ", "
        + type + ", " + getMessage();
  }
}