/*
 * Copyright DataStax, Inc.
 *
 * 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 com.datastax.oss.driver.internal.core.channel;

import com.datastax.oss.driver.api.core.CqlIdentifier;
import com.datastax.oss.driver.api.core.ProtocolVersion;
import com.datastax.oss.driver.api.core.metadata.EndPoint;
import com.datastax.oss.driver.internal.core.util.concurrent.UncaughtExceptions;
import com.datastax.oss.protocol.internal.Message;
import io.netty.channel.Channel;
import io.netty.channel.ChannelConfig;
import io.netty.channel.ChannelFuture;
import io.netty.channel.EventLoop;
import io.netty.util.AttributeKey;
import io.netty.util.concurrent.Future;
import io.netty.util.concurrent.Promise;
import java.net.SocketAddress;
import java.nio.ByteBuffer;
import java.util.List;
import java.util.Map;
import java.util.concurrent.atomic.AtomicBoolean;
import net.jcip.annotations.ThreadSafe;

A thin wrapper around a Netty Channel, to send requests to a Cassandra node and receive responses. /**
 * A thin wrapper around a Netty {@link Channel}, to send requests to a Cassandra node and receive
 * responses.
 */
@ThreadSafe
public class DriverChannel {

  static final AttributeKey<String> CLUSTER_NAME_KEY = AttributeKey.newInstance("cluster_name");
  static final AttributeKey<Map<String, List<String>>> OPTIONS_KEY =
      AttributeKey.newInstance("options");

  @SuppressWarnings("RedundantStringConstructorCall")
  static final Object GRACEFUL_CLOSE_MESSAGE = new String("GRACEFUL_CLOSE_MESSAGE");

  @SuppressWarnings("RedundantStringConstructorCall")
  static final Object FORCEFUL_CLOSE_MESSAGE = new String("FORCEFUL_CLOSE_MESSAGE");

  private final EndPoint endPoint;
  private final Channel channel;
  private final InFlightHandler inFlightHandler;
  private final WriteCoalescer writeCoalescer;
  private final ProtocolVersion protocolVersion;
  private final AtomicBoolean closing = new AtomicBoolean();
  private final AtomicBoolean forceClosing = new AtomicBoolean();

  DriverChannel(
      EndPoint endPoint,
      Channel channel,
      WriteCoalescer writeCoalescer,
      ProtocolVersion protocolVersion) {
    this.endPoint = endPoint;
    this.channel = channel;
    this.inFlightHandler = channel.pipeline().get(InFlightHandler.class);
    this.writeCoalescer = writeCoalescer;
    this.protocolVersion = protocolVersion;
  }

  
Returns:
a future that succeeds when the request frame was successfully written on the channel. Beyond that, the caller will be notified through the responseCallback./**
   * @return a future that succeeds when the request frame was successfully written on the channel.
   *     Beyond that, the caller will be notified through the {@code responseCallback}.
   */
  public Future<Void> write(
      Message request,
      boolean tracing,
      Map<String, ByteBuffer> customPayload,
      ResponseCallback responseCallback) {
    if (closing.get()) {
      return channel.newFailedFuture(new IllegalStateException("Driver channel is closing"));
    }
    RequestMessage message = new RequestMessage(request, tracing, customPayload, responseCallback);
    return writeCoalescer.writeAndFlush(channel, message);
  }

  
Cancels a callback, indicating that the client that wrote it is no longer interested in the
answer.
Note that this does not cancel the request server-side (but might in the future if Cassandra
supports it).
/**
   * Cancels a callback, indicating that the client that wrote it is no longer interested in the
   * answer.
   *
   * <p>Note that this does not cancel the request server-side (but might in the future if Cassandra
   * supports it).
   */
  public void cancel(ResponseCallback responseCallback) {
    // To avoid creating an extra message, we adopt the convention that writing the callback
    // directly means cancellation
    writeCoalescer.writeAndFlush(channel, responseCallback).addListener(UncaughtExceptions::log);
  }

  
Switches the underlying Cassandra connection to a new keyspace (as if a USE ... statement was issued). 
The future will complete once the change is effective. Only one change may run at a given
time, concurrent attempts will fail.
Changing the keyspace is inherently thread-unsafe: if other queries are running at the same
time, the keyspace they will use is unpredictable.
/**
   * Switches the underlying Cassandra connection to a new keyspace (as if a {@code USE ...}
   * statement was issued).
   *
   * <p>The future will complete once the change is effective. Only one change may run at a given
   * time, concurrent attempts will fail.
   *
   * <p>Changing the keyspace is inherently thread-unsafe: if other queries are running at the same
   * time, the keyspace they will use is unpredictable.
   */
  public Future<Void> setKeyspace(CqlIdentifier newKeyspace) {
    Promise<Void> promise = channel.eventLoop().newPromise();
    channel.pipeline().fireUserEventTriggered(new SetKeyspaceEvent(newKeyspace, promise));
    return promise;
  }

  
Returns:
the name of the Cassandra cluster as returned by system.local.cluster_name on this connection./**
   * @return the name of the Cassandra cluster as returned by {@code system.local.cluster_name} on
   *     this connection.
   */
  public String getClusterName() {
    return channel.attr(CLUSTER_NAME_KEY).get();
  }

  public Map<String, List<String>> getOptions() {
    return channel.attr(OPTIONS_KEY).get();
  }

  
Returns:
the number of available stream ids on the channel. This is used to weigh channels in
    pools that have a size bigger than 1, in the load balancing policy, and for monitoring
    purposes./**
   * @return the number of available stream ids on the channel. This is used to weigh channels in
   *     pools that have a size bigger than 1, in the load balancing policy, and for monitoring
   *     purposes.
   */
  public int getAvailableIds() {
    return inFlightHandler.getAvailableIds();
  }

  
Returns:
the number of requests currently executing on this channel (including orphaned ids)./**
   * @return the number of requests currently executing on this channel (including {@link
   *     #getOrphanedIds() orphaned ids}).
   */
  public int getInFlight() {
    return inFlightHandler.getInFlight();
  }

  
Returns:
the number of stream ids for requests that have either timed out or been cancelled, but
    for which we can't release the stream id because a request might still come from the
    server./**
   * @return the number of stream ids for requests that have either timed out or been cancelled, but
   *     for which we can't release the stream id because a request might still come from the
   *     server.
   */
  public int getOrphanedIds() {
    return inFlightHandler.getOrphanIds();
  }

  public EventLoop eventLoop() {
    return channel.eventLoop();
  }

  public ProtocolVersion protocolVersion() {
    return protocolVersion;
  }

  
The endpoint that was used to establish the connection. /** The endpoint that was used to establish the connection. */
  public EndPoint getEndPoint() {
    return endPoint;
  }

  public SocketAddress localAddress() {
    return channel.localAddress();
  }

  
Returns:
The configuration of this channel./** @return The {@link ChannelConfig configuration} of this channel. */
  public ChannelConfig config() {
    return channel.config();
  }

  
Initiates a graceful shutdown: no new requests will be accepted, but all pending requests will
be allowed to complete before the underlying channel is closed.
/**
   * Initiates a graceful shutdown: no new requests will be accepted, but all pending requests will
   * be allowed to complete before the underlying channel is closed.
   */
  public Future<Void> close() {
    if (closing.compareAndSet(false, true) && channel.isOpen()) {
      // go through the coalescer: this guarantees that we won't reject writes that were submitted
      // before, but had not been coalesced yet.
      writeCoalescer
          .writeAndFlush(channel, GRACEFUL_CLOSE_MESSAGE)
          .addListener(UncaughtExceptions::log);
    }
    return channel.closeFuture();
  }

  
Initiates a forced shutdown: any pending request will be aborted and the underlying channel
will be closed.
/**
   * Initiates a forced shutdown: any pending request will be aborted and the underlying channel
   * will be closed.
   */
  public Future<Void> forceClose() {
    this.close();
    if (forceClosing.compareAndSet(false, true) && channel.isOpen()) {
      writeCoalescer
          .writeAndFlush(channel, FORCEFUL_CLOSE_MESSAGE)
          .addListener(UncaughtExceptions::log);
    }
    return channel.closeFuture();
  }

  
Returns a future that will complete when a graceful close has started, but not yet completed.
In other words, the channel has stopped accepting new requests, but is still waiting for pending requests to finish. Once the last response has been received, the channel will really close and closeFuture() will be completed. 
If there were no pending requests when the graceful shutdown was initiated, or if forceClose() is called first, this future will never complete. /**
   * Returns a future that will complete when a graceful close has started, but not yet completed.
   *
   * <p>In other words, the channel has stopped accepting new requests, but is still waiting for
   * pending requests to finish. Once the last response has been received, the channel will really
   * close and {@link #closeFuture()} will be completed.
   *
   * <p>If there were no pending requests when the graceful shutdown was initiated, or if {@link
   * #forceClose()} is called first, this future will never complete.
   */
  public ChannelFuture closeStartedFuture() {
    return this.inFlightHandler.closeStartedFuture;
  }

  
Does not close the channel, but returns a future that will complete when it is completely
closed.
/**
   * Does not close the channel, but returns a future that will complete when it is completely
   * closed.
   */
  public ChannelFuture closeFuture() {
    return channel.closeFuture();
  }

  @Override
  public String toString() {
    return channel.toString();
  }

  // This is essentially a stripped-down Frame. We can't materialize the frame before writing,
  // because we need the stream id, which is assigned from within the event loop.
  static class RequestMessage {
    final Message request;
    final boolean tracing;
    final Map<String, ByteBuffer> customPayload;
    final ResponseCallback responseCallback;

    RequestMessage(
        Message message,
        boolean tracing,
        Map<String, ByteBuffer> customPayload,
        ResponseCallback responseCallback) {
      this.request = message;
      this.tracing = tracing;
      this.customPayload = customPayload;
      this.responseCallback = responseCallback;
    }
  }

  static class SetKeyspaceEvent {
    final CqlIdentifier keyspaceName;
    final Promise<Void> promise;

    public SetKeyspaceEvent(CqlIdentifier keyspaceName, Promise<Void> promise) {
      this.keyspaceName = keyspaceName;
      this.promise = promise;
    }
  }
}