/*
 * Copyright 2015 The gRPC Authors
 *
 * 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 io.grpc.internal;

import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.base.Preconditions.checkState;
import static io.grpc.internal.GrpcAttributes.ATTR_SECURITY_LEVEL;
import static io.grpc.internal.GrpcUtil.ACCEPT_ENCODING_SPLITTER;
import static io.grpc.internal.GrpcUtil.CONTENT_LENGTH_KEY;
import static io.grpc.internal.GrpcUtil.MESSAGE_ACCEPT_ENCODING_KEY;
import static io.grpc.internal.GrpcUtil.MESSAGE_ENCODING_KEY;

import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Throwables;
import com.google.common.util.concurrent.MoreExecutors;
import io.grpc.Attributes;
import io.grpc.Codec;
import io.grpc.Compressor;
import io.grpc.CompressorRegistry;
import io.grpc.Context;
import io.grpc.DecompressorRegistry;
import io.grpc.InternalDecompressorRegistry;
import io.grpc.InternalStatus;
import io.grpc.Metadata;
import io.grpc.MethodDescriptor;
import io.grpc.SecurityLevel;
import io.grpc.ServerCall;
import io.grpc.Status;
import io.grpc.StatusRuntimeException;
import io.perfmark.PerfMark;
import io.perfmark.Tag;
import io.perfmark.TaskCloseable;
import java.io.InputStream;
import java.util.logging.Level;
import java.util.logging.Logger;

final class ServerCallImpl<ReqT, RespT> extends ServerCall<ReqT, RespT> {

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

  @VisibleForTesting
  static final String TOO_MANY_RESPONSES = "Too many responses";
  @VisibleForTesting
  static final String MISSING_RESPONSE = "Completed without a response";

  private final ServerStream stream;
  private final MethodDescriptor<ReqT, RespT> method;
  private final Tag tag;
  private final Context.CancellableContext context;
  private final byte[] messageAcceptEncoding;
  private final DecompressorRegistry decompressorRegistry;
  private final CompressorRegistry compressorRegistry;
  private CallTracer serverCallTracer;

  // state
  private volatile boolean cancelled;
  private boolean sendHeadersCalled;
  private boolean closeCalled;
  private Compressor compressor;
  private boolean messageSent;

  ServerCallImpl(ServerStream stream, MethodDescriptor<ReqT, RespT> method,
      Metadata inboundHeaders, Context.CancellableContext context,
      DecompressorRegistry decompressorRegistry, CompressorRegistry compressorRegistry,
      CallTracer serverCallTracer, Tag tag) {
    this.stream = stream;
    this.method = method;
    this.context = context;
    this.messageAcceptEncoding = inboundHeaders.get(MESSAGE_ACCEPT_ENCODING_KEY);
    this.decompressorRegistry = decompressorRegistry;
    this.compressorRegistry = compressorRegistry;
    this.serverCallTracer = serverCallTracer;
    this.serverCallTracer.reportCallStarted();
    this.tag = tag;
  }

  @Override
  public void request(int numMessages) {
    try (TaskCloseable ignore = PerfMark.traceTask("ServerCall.request")) {
      PerfMark.attachTag(tag);
      stream.request(numMessages);
    }
  }

  @Override
  public void sendHeaders(Metadata headers) {
    try (TaskCloseable ignore = PerfMark.traceTask("ServerCall.sendHeaders")) {
      PerfMark.attachTag(tag);
      sendHeadersInternal(headers);
    }
  }

  private void sendHeadersInternal(Metadata headers) {
    checkState(!sendHeadersCalled, "sendHeaders has already been called");
    checkState(!closeCalled, "call is closed");

    headers.discardAll(CONTENT_LENGTH_KEY);
    headers.discardAll(MESSAGE_ENCODING_KEY);
    if (compressor == null) {
      compressor = Codec.Identity.NONE;
    } else {
      if (messageAcceptEncoding != null) {
        // TODO(carl-mastrangelo): remove the string allocation.
        if (!GrpcUtil.iterableContains(
            ACCEPT_ENCODING_SPLITTER.split(new String(messageAcceptEncoding, GrpcUtil.US_ASCII)),
            compressor.getMessageEncoding())) {
          // resort to using no compression.
          compressor = Codec.Identity.NONE;
        }
      } else {
        compressor = Codec.Identity.NONE;
      }
    }

    // Always put compressor, even if it's identity.
    headers.put(MESSAGE_ENCODING_KEY, compressor.getMessageEncoding());

    stream.setCompressor(compressor);

    headers.discardAll(MESSAGE_ACCEPT_ENCODING_KEY);
    byte[] advertisedEncodings =
        InternalDecompressorRegistry.getRawAdvertisedMessageEncodings(decompressorRegistry);
    if (advertisedEncodings.length != 0) {
      headers.put(MESSAGE_ACCEPT_ENCODING_KEY, advertisedEncodings);
    }

    // Don't check if sendMessage has been called, since it requires that sendHeaders was already
    // called.
    sendHeadersCalled = true;
    stream.writeHeaders(headers);
  }

  @Override
  public void sendMessage(RespT message) {
    try (TaskCloseable ignore = PerfMark.traceTask("ServerCall.sendMessage")) {
      PerfMark.attachTag(tag);
      sendMessageInternal(message);
    }
  }

  private void sendMessageInternal(RespT message) {
    checkState(sendHeadersCalled, "sendHeaders has not been called");
    checkState(!closeCalled, "call is closed");

    if (method.getType().serverSendsOneMessage() && messageSent) {
      handleInternalError(Status.INTERNAL.withDescription(TOO_MANY_RESPONSES).asRuntimeException());
      return;
    }

    messageSent = true;
    try {
      InputStream resp = method.streamResponse(message);
      stream.writeMessage(resp);
      if (!getMethodDescriptor().getType().serverSendsOneMessage()) {
        stream.flush();
      }
    } catch (RuntimeException e) {
      handleInternalError(e);
    } catch (Error e) {
      close(
          Status.CANCELLED.withDescription("Server sendMessage() failed with Error"),
          new Metadata());
      throw e;
    }
  }

  @Override
  public void setMessageCompression(boolean enable) {
    stream.setMessageCompression(enable);
  }

  @Override
  public void setCompression(String compressorName) {
    // Added here to give a better error message.
    checkState(!sendHeadersCalled, "sendHeaders has been called");

    compressor = compressorRegistry.lookupCompressor(compressorName);
    checkArgument(compressor != null, "Unable to find compressor by name %s", compressorName);
  }

  @Override
  public boolean isReady() {
    if (closeCalled) {
      return false;
    }
    return stream.isReady();
  }

  @Override
  public void close(Status status, Metadata trailers) {
    try (TaskCloseable ignore = PerfMark.traceTask("ServerCall.close")) {
      PerfMark.attachTag(tag);
      closeInternal(status, trailers);
    }
  }

  private void closeInternal(Status status, Metadata trailers) {
    checkState(!closeCalled, "call already closed");
    try {
      closeCalled = true;

      if (status.isOk() && method.getType().serverSendsOneMessage() && !messageSent) {
        handleInternalError(Status.INTERNAL.withDescription(MISSING_RESPONSE).asRuntimeException());
        return;
      }

      stream.close(status, trailers);
    } finally {
      serverCallTracer.reportCallEnded(status.isOk());
    }
  }

  @Override
  public boolean isCancelled() {
    return cancelled;
  }

  ServerStreamListener newServerStreamListener(ServerCall.Listener<ReqT> listener) {
    return new ServerStreamListenerImpl<>(this, listener, context);
  }

  @Override
  public Attributes getAttributes() {
    return stream.getAttributes();
  }

  @Override
  public String getAuthority() {
    return stream.getAuthority();
  }

  @Override
  public MethodDescriptor<ReqT, RespT> getMethodDescriptor() {
    return method;
  }

  @Override
  public SecurityLevel getSecurityLevel() {
    final Attributes attributes = getAttributes();
    if (attributes == null) {
      return super.getSecurityLevel();
    }
    final SecurityLevel securityLevel = attributes.get(ATTR_SECURITY_LEVEL);
    return securityLevel == null ? super.getSecurityLevel() : securityLevel;
  }

  /**
   * Close the {@link ServerStream} because an internal error occurred. Allow the application to
   * run until completion, but silently ignore interactions with the {@link ServerStream} from now
   * on.
   */
  private void handleInternalError(Throwable internalError) {
    log.log(Level.WARNING, "Cancelling the stream because of internal error", internalError);
    Status status = (internalError instanceof StatusRuntimeException)
        ? ((StatusRuntimeException) internalError).getStatus()
        : Status.INTERNAL.withCause(internalError)
            .withDescription("Internal error so cancelling stream.");
    stream.cancel(status);
    serverCallTracer.reportCallEnded(false); // error so always false
  }

  /**
   * All of these callbacks are assumed to called on an application thread, and the caller is
   * responsible for handling thrown exceptions.
   */
  @VisibleForTesting
  static final class ServerStreamListenerImpl<ReqT> implements ServerStreamListener {
    private final ServerCallImpl<ReqT, ?> call;
    private final ServerCall.Listener<ReqT> listener;
    private final Context.CancellableContext context;

    public ServerStreamListenerImpl(
        ServerCallImpl<ReqT, ?> call, ServerCall.Listener<ReqT> listener,
        Context.CancellableContext context) {
      this.call = checkNotNull(call, "call");
      this.listener = checkNotNull(listener, "listener must not be null");
      this.context = checkNotNull(context, "context");
      // Wire ourselves up so that if the context is cancelled, our flag call.cancelled also
      // reflects the new state. Use a DirectExecutor so that it happens in the same thread
      // as the caller of {@link Context#cancel}.
      this.context.addListener(
          new Context.CancellationListener() {
            @Override
            public void cancelled(Context context) {
              // If the context has a cancellation cause then something exceptional happened
              // and we should also mark the call as cancelled.
              if (context.cancellationCause() != null) {
                ServerStreamListenerImpl.this.call.cancelled = true;
              }
            }
          },
          MoreExecutors.directExecutor());
    }

    @Override
    public void messagesAvailable(MessageProducer producer) {
      try (TaskCloseable ignore = PerfMark.traceTask("ServerStreamListener.messagesAvailable")) {
        PerfMark.attachTag(call.tag);
        messagesAvailableInternal(producer);
      }
    }

    @SuppressWarnings("Finally") // The code avoids suppressing the exception thrown from try
    private void messagesAvailableInternal(final MessageProducer producer) {
      if (call.cancelled) {
        GrpcUtil.closeQuietly(producer);
        return;
      }

      InputStream message;
      try {
        while ((message = producer.next()) != null) {
          try {
            listener.onMessage(call.method.parseRequest(message));
          } catch (Throwable t) {
            GrpcUtil.closeQuietly(message);
            throw t;
          }
          message.close();
        }
      } catch (Throwable t) {
        GrpcUtil.closeQuietly(producer);
        Throwables.throwIfUnchecked(t);
        throw new RuntimeException(t);
      }
    }

    @Override
    public void halfClosed() {
      try (TaskCloseable ignore = PerfMark.traceTask("ServerStreamListener.halfClosed")) {
        PerfMark.attachTag(call.tag);
        if (call.cancelled) {
          return;
        }

        listener.onHalfClose();
      }
    }

    @Override
    public void closed(Status status) {
      try (TaskCloseable ignore = PerfMark.traceTask("ServerStreamListener.closed")) {
        PerfMark.attachTag(call.tag);
        closedInternal(status);
      }
    }

    private void closedInternal(Status status) {
      Throwable cancelCause = null;
      try {
        if (status.isOk()) {
          listener.onComplete();
        } else {
          call.cancelled = true;
          listener.onCancel();
          // The status will not have a cause in all failure scenarios but we want to make sure
          // we always cancel the context with one to keep the context cancelled state consistent.
          cancelCause = InternalStatus.asRuntimeException(
              Status.CANCELLED.withDescription("RPC cancelled"), null, false);
        }
      } finally {
        // Cancel context after delivering RPC closure notification to allow the application to
        // clean up and update any state based on whether onComplete or onCancel was called.
        context.cancel(cancelCause);
      }
    }

    @Override
    public void onReady() {
      try (TaskCloseable ignore = PerfMark.traceTask("ServerStreamListener.onReady")) {
        PerfMark.attachTag(call.tag);
        if (call.cancelled) {
          return;
        }
        listener.onReady();
      }
    }
  }
}
