include/grpcpp/impl/codegen/call.h

/*
 *
 * Copyright 2015 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.
 *
 */

#ifndef GRPCPP_IMPL_CODEGEN_CALL_H
#define GRPCPP_IMPL_CODEGEN_CALL_H

#include <assert.h>
#include <array>
#include <cstring>
#include <functional>
#include <map>
#include <memory>
#include <vector>

#include <grpcpp/impl/codegen/byte_buffer.h>
#include <grpcpp/impl/codegen/call_hook.h>
#include <grpcpp/impl/codegen/client_context.h>
#include <grpcpp/impl/codegen/client_interceptor.h>
#include <grpcpp/impl/codegen/completion_queue_tag.h>
#include <grpcpp/impl/codegen/config.h>
#include <grpcpp/impl/codegen/core_codegen_interface.h>
#include <grpcpp/impl/codegen/serialization_traits.h>
#include <grpcpp/impl/codegen/server_interceptor.h>
#include <grpcpp/impl/codegen/slice.h>
#include <grpcpp/impl/codegen/status.h>
#include <grpcpp/impl/codegen/string_ref.h>

#include <grpc/impl/codegen/atm.h>
#include <grpc/impl/codegen/compression_types.h>
#include <grpc/impl/codegen/grpc_types.h>

namespace grpc {

class CompletionQueue;
extern CoreCodegenInterface* g_core_codegen_interface;

namespace internal {
class Call;
class CallHook;

// TODO(yangg) if the map is changed before we send, the pointers will be a
// mess. Make sure it does not happen.
inline grpc_metadata* FillMetadataArray(
    const std::multimap<grpc::string, grpc::string>& metadata,
    size_t* metadata_count, const grpc::string& optional_error_details) {
  *metadata_count = metadata.size() + (optional_error_details.empty() ? 0 : 1);
  if (*metadata_count == 0) {
    return nullptr;
  }
  grpc_metadata* metadata_array =
      (grpc_metadata*)(g_core_codegen_interface->gpr_malloc(
          (*metadata_count) * sizeof(grpc_metadata)));
  size_t i = 0;
  for (auto iter = metadata.cbegin(); iter != metadata.cend(); ++iter, ++i) {
    metadata_array[i].key = SliceReferencingString(iter->first);
    metadata_array[i].value = SliceReferencingString(iter->second);
  }
  if (!optional_error_details.empty()) {
    metadata_array[i].key =
        g_core_codegen_interface->grpc_slice_from_static_buffer(
            kBinaryErrorDetailsKey, sizeof(kBinaryErrorDetailsKey) - 1);
    metadata_array[i].value = SliceReferencingString(optional_error_details);
  }
  return metadata_array;
}
}  // namespace internal

/// Per-message write options.
class WriteOptions {
 public:
  WriteOptions() : flags_(0), last_message_(false) {}
  WriteOptions(const WriteOptions& other)
      : flags_(other.flags_), last_message_(other.last_message_) {}

  /// Clear all flags.
  inline void Clear() { flags_ = 0; }

  /// Returns raw flags bitset.
  inline uint32_t flags() const { return flags_; }

  /// Sets flag for the disabling of compression for the next message write.
  ///
  /// \sa GRPC_WRITE_NO_COMPRESS
  inline WriteOptions& set_no_compression() {
    SetBit(GRPC_WRITE_NO_COMPRESS);
    return *this;
  }

  /// Clears flag for the disabling of compression for the next message write.
  ///
  /// \sa GRPC_WRITE_NO_COMPRESS
  inline WriteOptions& clear_no_compression() {
    ClearBit(GRPC_WRITE_NO_COMPRESS);
    return *this;
  }

  /// Get value for the flag indicating whether compression for the next
  /// message write is forcefully disabled.
  ///
  /// \sa GRPC_WRITE_NO_COMPRESS
  inline bool get_no_compression() const {
    return GetBit(GRPC_WRITE_NO_COMPRESS);
  }

  /// Sets flag indicating that the write may be buffered and need not go out on
  /// the wire immediately.
  ///
  /// \sa GRPC_WRITE_BUFFER_HINT
  inline WriteOptions& set_buffer_hint() {
    SetBit(GRPC_WRITE_BUFFER_HINT);
    return *this;
  }

  /// Clears flag indicating that the write may be buffered and need not go out
  /// on the wire immediately.
  ///
  /// \sa GRPC_WRITE_BUFFER_HINT
  inline WriteOptions& clear_buffer_hint() {
    ClearBit(GRPC_WRITE_BUFFER_HINT);
    return *this;
  }

  /// Get value for the flag indicating that the write may be buffered and need
  /// not go out on the wire immediately.
  ///
  /// \sa GRPC_WRITE_BUFFER_HINT
  inline bool get_buffer_hint() const { return GetBit(GRPC_WRITE_BUFFER_HINT); }

  /// corked bit: aliases set_buffer_hint currently, with the intent that
  /// set_buffer_hint will be removed in the future
  inline WriteOptions& set_corked() {
    SetBit(GRPC_WRITE_BUFFER_HINT);
    return *this;
  }

  inline WriteOptions& clear_corked() {
    ClearBit(GRPC_WRITE_BUFFER_HINT);
    return *this;
  }

  inline bool is_corked() const { return GetBit(GRPC_WRITE_BUFFER_HINT); }

  /// last-message bit: indicates this is the last message in a stream
  /// client-side:  makes Write the equivalent of performing Write, WritesDone
  /// in a single step
  /// server-side:  hold the Write until the service handler returns (sync api)
  /// or until Finish is called (async api)
  inline WriteOptions& set_last_message() {
    last_message_ = true;
    return *this;
  }

  /// Clears flag indicating that this is the last message in a stream,
  /// disabling coalescing.
  inline WriteOptions& clear_last_message() {
    last_message_ = false;
    return *this;
  }

  /// Guarantee that all bytes have been written to the socket before completing
  /// this write (usually writes are completed when they pass flow control).
  inline WriteOptions& set_write_through() {
    SetBit(GRPC_WRITE_THROUGH);
    return *this;
  }

  inline bool is_write_through() const { return GetBit(GRPC_WRITE_THROUGH); }

  /// Get value for the flag indicating that this is the last message, and
  /// should be coalesced with trailing metadata.
  ///
  /// \sa GRPC_WRITE_LAST_MESSAGE
  bool is_last_message() const { return last_message_; }

  WriteOptions& operator=(const WriteOptions& rhs) {
    flags_ = rhs.flags_;
    return *this;
  }

 private:
  void SetBit(const uint32_t mask) { flags_ |= mask; }

  void ClearBit(const uint32_t mask) { flags_ &= ~mask; }

  bool GetBit(const uint32_t mask) const { return (flags_ & mask) != 0; }

  uint32_t flags_;
  bool last_message_;
};

namespace internal {
/// Default argument for CallOpSet. I is unused by the class, but can be
/// used for generating multiple names for the same thing.
template <int I>
class CallNoOp {
 protected:
  void AddOp(grpc_op* ops, size_t* nops) {}
  void FinishOp(bool* status) {}
  void SetInterceptionHookPoint(
      experimental::InterceptorBatchMethods* interceptor_methods) {}

  void SetFinishInterceptionHookPoint(
      experimental::InterceptorBatchMethods* interceptor_methods) {}
  void SetHijackingState(
      experimental::InterceptorBatchMethods* interceptor_methods) {}
};

class CallOpSendInitialMetadata {
 public:
  CallOpSendInitialMetadata() : send_(false) {
    maybe_compression_level_.is_set = false;
  }

  void SendInitialMetadata(std::multimap<grpc::string, grpc::string>* metadata,
                           uint32_t flags) {
    maybe_compression_level_.is_set = false;
    send_ = true;
    flags_ = flags;
    metadata_map_ = metadata;
  }

  void set_compression_level(grpc_compression_level level) {
    maybe_compression_level_.is_set = true;
    maybe_compression_level_.level = level;
  }

 protected:
  void AddOp(grpc_op* ops, size_t* nops) {
    if (!send_ || hijacked_) return;
    grpc_op* op = &ops[(*nops)++];
    op->op = GRPC_OP_SEND_INITIAL_METADATA;
    op->flags = flags_;
    op->reserved = NULL;
    initial_metadata_ =
        FillMetadataArray(*metadata_map_, &initial_metadata_count_, "");
    op->data.send_initial_metadata.count = initial_metadata_count_;
    op->data.send_initial_metadata.metadata = initial_metadata_;
    op->data.send_initial_metadata.maybe_compression_level.is_set =
        maybe_compression_level_.is_set;
    if (maybe_compression_level_.is_set) {
      op->data.send_initial_metadata.maybe_compression_level.level =
          maybe_compression_level_.level;
    }
  }
  void FinishOp(bool* status) {
    if (!send_ || hijacked_) return;
    g_core_codegen_interface->gpr_free(initial_metadata_);
    send_ = false;
  }

  void SetInterceptionHookPoint(
      experimental::InterceptorBatchMethods* interceptor_methods) {
    if (!send_) return;
    interceptor_methods->AddInterceptionHookPoint(
        experimental::InterceptionHookPoints::PRE_SEND_INITIAL_METADATA);
    interceptor_methods->SetSendInitialMetadata(metadata_map_);
  }

  void SetFinishInterceptionHookPoint(
      experimental::InterceptorBatchMethods* interceptor_methods) {}

  void SetHijackingState(
      experimental::InterceptorBatchMethods* interceptor_methods) {
    hijacked_ = true;
  }

  bool hijacked_ = false;
  bool send_;
  uint32_t flags_;
  size_t initial_metadata_count_;
  std::multimap<grpc::string, grpc::string>* metadata_map_;
  grpc_metadata* initial_metadata_;
  struct {
    bool is_set;
    grpc_compression_level level;
  } maybe_compression_level_;
};

class CallOpSendMessage {
 public:
  CallOpSendMessage() : send_buf_() {}

  /// Send \a message using \a options for the write. The \a options are cleared
  /// after use.
  template <class M>
  Status SendMessage(const M& message,
                     WriteOptions options) GRPC_MUST_USE_RESULT;

  template <class M>
  Status SendMessage(const M& message) GRPC_MUST_USE_RESULT;

 protected:
  void AddOp(grpc_op* ops, size_t* nops) {
    if (!send_buf_.Valid() || hijacked_) return;
    grpc_op* op = &ops[(*nops)++];
    op->op = GRPC_OP_SEND_MESSAGE;
    op->flags = write_options_.flags();
    op->reserved = NULL;
    op->data.send_message.send_message = send_buf_.c_buffer();
    // Flags are per-message: clear them after use.
    write_options_.Clear();
  }
  void FinishOp(bool* status) { send_buf_.Clear(); }

  void SetInterceptionHookPoint(
      experimental::InterceptorBatchMethods* interceptor_methods) {
    if (!send_buf_.Valid()) return;
    interceptor_methods->AddInterceptionHookPoint(
        experimental::InterceptionHookPoints::PRE_SEND_MESSAGE);
    interceptor_methods->SetSendMessage(&send_buf_);
  }

  void SetFinishInterceptionHookPoint(
      experimental::InterceptorBatchMethods* interceptor_methods) {}

  void SetHijackingState(
      experimental::InterceptorBatchMethods* interceptor_methods) {
    hijacked_ = true;
  }

 private:
  bool hijacked_ = false;
  ByteBuffer send_buf_;
  WriteOptions write_options_;
};

template <class M>
Status CallOpSendMessage::SendMessage(const M& message, WriteOptions options) {
  write_options_ = options;
  bool own_buf;
  // TODO(vjpai): Remove the void below when possible
  // The void in the template parameter below should not be needed
  // (since it should be implicit) but is needed due to an observed
  // difference in behavior between clang and gcc for certain internal users
  Status result = SerializationTraits<M, void>::Serialize(
      message, send_buf_.bbuf_ptr(), &own_buf);
  if (!own_buf) {
    send_buf_.Duplicate();
  }
  return result;
}

template <class M>
Status CallOpSendMessage::SendMessage(const M& message) {
  return SendMessage(message, WriteOptions());
}

template <class R>
class CallOpRecvMessage {
 public:
  CallOpRecvMessage()
      : got_message(false),
        message_(nullptr),
        allow_not_getting_message_(false) {}

  void RecvMessage(R* message) { message_ = message; }

  // Do not change status if no message is received.
  void AllowNoMessage() { allow_not_getting_message_ = true; }

  bool got_message;

 protected:
  void AddOp(grpc_op* ops, size_t* nops) {
    if (message_ == nullptr || hijacked_) return;
    grpc_op* op = &ops[(*nops)++];
    op->op = GRPC_OP_RECV_MESSAGE;
    op->flags = 0;
    op->reserved = NULL;
    op->data.recv_message.recv_message = recv_buf_.c_buffer_ptr();
  }

  void FinishOp(bool* status) {
    if (message_ == nullptr || hijacked_) return;
    if (recv_buf_.Valid()) {
      if (*status) {
        got_message = *status =
            SerializationTraits<R>::Deserialize(recv_buf_.bbuf_ptr(), message_)
                .ok();
        recv_buf_.Release();
      } else {
        got_message = false;
        recv_buf_.Clear();
      }
    } else {
      got_message = false;
      if (!allow_not_getting_message_) {
        *status = false;
      }
    }
    message_ = nullptr;
  }

  void SetInterceptionHookPoint(
      experimental::InterceptorBatchMethods* interceptor_methods) {
    interceptor_methods->SetRecvMessage(message_);
  }

  void SetFinishInterceptionHookPoint(
      experimental::InterceptorBatchMethods* interceptor_methods) {
    if (!got_message) return;
    interceptor_methods->AddInterceptionHookPoint(
        experimental::InterceptionHookPoints::POST_RECV_MESSAGE);
  }
  void SetHijackingState(
      experimental::InterceptorBatchMethods* interceptor_methods) {
    hijacked_ = true;
    if (message_ == nullptr) return;
    interceptor_methods->AddInterceptionHookPoint(
        experimental::InterceptionHookPoints::PRE_RECV_MESSAGE);
    got_message = true;
  }

 private:
  R* message_;
  ByteBuffer recv_buf_;
  bool allow_not_getting_message_;
  bool hijacked_ = false;
};

class DeserializeFunc {
 public:
  virtual Status Deserialize(ByteBuffer* buf) = 0;
  virtual ~DeserializeFunc() {}
};

template <class R>
class DeserializeFuncType final : public DeserializeFunc {
 public:
  DeserializeFuncType(R* message) : message_(message) {}
  Status Deserialize(ByteBuffer* buf) override {
    return SerializationTraits<R>::Deserialize(buf->bbuf_ptr(), message_);
  }

  ~DeserializeFuncType() override {}

 private:
  R* message_;  // Not a managed pointer because management is external to this
};

class CallOpGenericRecvMessage {
 public:
  CallOpGenericRecvMessage()
      : got_message(false), allow_not_getting_message_(false) {}

  template <class R>
  void RecvMessage(R* message) {
    // Use an explicit base class pointer to avoid resolution error in the
    // following unique_ptr::reset for some old implementations.
    DeserializeFunc* func = new DeserializeFuncType<R>(message);
    deserialize_.reset(func);
    message_ = message;
  }

  // Do not change status if no message is received.
  void AllowNoMessage() { allow_not_getting_message_ = true; }

  bool got_message;

 protected:
  void AddOp(grpc_op* ops, size_t* nops) {
    if (!deserialize_ || hijacked_) return;
    grpc_op* op = &ops[(*nops)++];
    op->op = GRPC_OP_RECV_MESSAGE;
    op->flags = 0;
    op->reserved = NULL;
    op->data.recv_message.recv_message = recv_buf_.c_buffer_ptr();
  }

  void FinishOp(bool* status) {
    if (!deserialize_ || hijacked_) return;
    if (recv_buf_.Valid()) {
      if (*status) {
        got_message = true;
        *status = deserialize_->Deserialize(&recv_buf_).ok();
        recv_buf_.Release();
      } else {
        got_message = false;
        recv_buf_.Clear();
      }
    } else {
      got_message = false;
      if (!allow_not_getting_message_) {
        *status = false;
      }
    }
    deserialize_.reset();
  }

  void SetInterceptionHookPoint(
      experimental::InterceptorBatchMethods* interceptor_methods) {
    interceptor_methods->SetRecvMessage(message_);
  }

  void SetFinishInterceptionHookPoint(
      experimental::InterceptorBatchMethods* interceptor_methods) {
    if (!got_message) return;
    interceptor_methods->AddInterceptionHookPoint(
        experimental::InterceptionHookPoints::POST_RECV_MESSAGE);
  }
  void SetHijackingState(
      experimental::InterceptorBatchMethods* interceptor_methods) {
    hijacked_ = true;
    if (!deserialize_) return;
    interceptor_methods->AddInterceptionHookPoint(
        experimental::InterceptionHookPoints::PRE_RECV_MESSAGE);
  }

 private:
  void* message_;
  bool hijacked_ = false;
  std::unique_ptr<DeserializeFunc> deserialize_;
  ByteBuffer recv_buf_;
  bool allow_not_getting_message_;
};

class CallOpClientSendClose {
 public:
  CallOpClientSendClose() : send_(false) {}

  void ClientSendClose() { send_ = true; }

 protected:
  void AddOp(grpc_op* ops, size_t* nops) {
    if (!send_ || hijacked_) return;
    grpc_op* op = &ops[(*nops)++];
    op->op = GRPC_OP_SEND_CLOSE_FROM_CLIENT;
    op->flags = 0;
    op->reserved = NULL;
  }
  void FinishOp(bool* status) { send_ = false; }

  void SetInterceptionHookPoint(
      experimental::InterceptorBatchMethods* interceptor_methods) {
    if (!send_) return;
    interceptor_methods->AddInterceptionHookPoint(
        experimental::InterceptionHookPoints::PRE_SEND_CLOSE);
  }

  void SetFinishInterceptionHookPoint(
      experimental::InterceptorBatchMethods* interceptor_methods) {}

  void SetHijackingState(
      experimental::InterceptorBatchMethods* interceptor_methods) {
    hijacked_ = true;
  }

 private:
  bool hijacked_ = false;
  bool send_;
};

class CallOpServerSendStatus {
 public:
  CallOpServerSendStatus() : send_status_available_(false) {}

  void ServerSendStatus(
      std::multimap<grpc::string, grpc::string>* trailing_metadata,
      const Status& status) {
    send_error_details_ = status.error_details();
    metadata_map_ = trailing_metadata;
    send_status_available_ = true;
    send_status_code_ = static_cast<grpc_status_code>(status.error_code());
    send_error_message_ = status.error_message();
  }

 protected:
  void AddOp(grpc_op* ops, size_t* nops) {
    if (!send_status_available_ || hijacked_) return;
    trailing_metadata_ = FillMetadataArray(
        *metadata_map_, &trailing_metadata_count_, send_error_details_);
    grpc_op* op = &ops[(*nops)++];
    op->op = GRPC_OP_SEND_STATUS_FROM_SERVER;
    op->data.send_status_from_server.trailing_metadata_count =
        trailing_metadata_count_;
    op->data.send_status_from_server.trailing_metadata = trailing_metadata_;
    op->data.send_status_from_server.status = send_status_code_;
    error_message_slice_ = SliceReferencingString(send_error_message_);
    op->data.send_status_from_server.status_details =
        send_error_message_.empty() ? nullptr : &error_message_slice_;
    op->flags = 0;
    op->reserved = NULL;
  }

  void FinishOp(bool* status) {
    if (!send_status_available_ || hijacked_) return;
    g_core_codegen_interface->gpr_free(trailing_metadata_);
    send_status_available_ = false;
  }

  void SetInterceptionHookPoint(
      experimental::InterceptorBatchMethods* interceptor_methods) {
    if (!send_status_available_) return;
    interceptor_methods->AddInterceptionHookPoint(
        experimental::InterceptionHookPoints::PRE_SEND_STATUS);
    interceptor_methods->SetSendTrailingMetadata(metadata_map_);
    interceptor_methods->SetSendStatus(&send_status_code_, &send_error_details_,
                                       &send_error_message_);
  }

  void SetFinishInterceptionHookPoint(
      experimental::InterceptorBatchMethods* interceptor_methods) {}

  void SetHijackingState(
      experimental::InterceptorBatchMethods* interceptor_methods) {
    hijacked_ = true;
  }

 private:
  bool hijacked_ = false;
  bool send_status_available_;
  grpc_status_code send_status_code_;
  grpc::string send_error_details_;
  grpc::string send_error_message_;
  size_t trailing_metadata_count_;
  std::multimap<grpc::string, grpc::string>* metadata_map_;
  grpc_metadata* trailing_metadata_;
  grpc_slice error_message_slice_;
};

class CallOpRecvInitialMetadata {
 public:
  CallOpRecvInitialMetadata() : metadata_map_(nullptr) {}

  void RecvInitialMetadata(ClientContext* context) {
    context->initial_metadata_received_ = true;
    metadata_map_ = &context->recv_initial_metadata_;
  }

 protected:
  void AddOp(grpc_op* ops, size_t* nops) {
    if (metadata_map_ == nullptr || hijacked_) return;
    grpc_op* op = &ops[(*nops)++];
    op->op = GRPC_OP_RECV_INITIAL_METADATA;
    op->data.recv_initial_metadata.recv_initial_metadata = metadata_map_->arr();
    op->flags = 0;
    op->reserved = NULL;
  }

  void FinishOp(bool* status) {
    if (metadata_map_ == nullptr || hijacked_) return;
  }

  void SetInterceptionHookPoint(
      experimental::InterceptorBatchMethods* interceptor_methods) {
    interceptor_methods->SetRecvInitialMetadata(metadata_map_);
  }

  void SetFinishInterceptionHookPoint(
      experimental::InterceptorBatchMethods* interceptor_methods) {
    if (metadata_map_ == nullptr) return;
    interceptor_methods->AddInterceptionHookPoint(
        experimental::InterceptionHookPoints::POST_RECV_INITIAL_METADATA);
    metadata_map_ = nullptr;
  }

  void SetHijackingState(
      experimental::InterceptorBatchMethods* interceptor_methods) {
    hijacked_ = true;
    if (metadata_map_ == nullptr) return;
    interceptor_methods->AddInterceptionHookPoint(
        experimental::InterceptionHookPoints::PRE_RECV_INITIAL_METADATA);
  }

 private:
  bool hijacked_ = false;
  MetadataMap* metadata_map_;
};

class CallOpClientRecvStatus {
 public:
  CallOpClientRecvStatus()
      : recv_status_(nullptr), debug_error_string_(nullptr) {}

  void ClientRecvStatus(ClientContext* context, Status* status) {
    client_context_ = context;
    metadata_map_ = &client_context_->trailing_metadata_;
    recv_status_ = status;
    error_message_ = g_core_codegen_interface->grpc_empty_slice();
  }

 protected:
  void AddOp(grpc_op* ops, size_t* nops) {
    if (recv_status_ == nullptr || hijacked_) return;
    grpc_op* op = &ops[(*nops)++];
    op->op = GRPC_OP_RECV_STATUS_ON_CLIENT;
    op->data.recv_status_on_client.trailing_metadata = metadata_map_->arr();
    op->data.recv_status_on_client.status = &status_code_;
    op->data.recv_status_on_client.status_details = &error_message_;
    op->data.recv_status_on_client.error_string = &debug_error_string_;
    op->flags = 0;
    op->reserved = NULL;
  }

  void FinishOp(bool* status) {
    if (recv_status_ == nullptr || hijacked_) return;
    grpc::string binary_error_details = metadata_map_->GetBinaryErrorDetails();
    *recv_status_ =
        Status(static_cast<StatusCode>(status_code_),
               GRPC_SLICE_IS_EMPTY(error_message_)
                   ? grpc::string()
                   : grpc::string(GRPC_SLICE_START_PTR(error_message_),
                                  GRPC_SLICE_END_PTR(error_message_)),
               binary_error_details);
    client_context_->set_debug_error_string(
        debug_error_string_ != nullptr ? debug_error_string_ : "");
    g_core_codegen_interface->grpc_slice_unref(error_message_);
    if (debug_error_string_ != nullptr) {
      g_core_codegen_interface->gpr_free((void*)debug_error_string_);
    }
  }

  void SetInterceptionHookPoint(
      experimental::InterceptorBatchMethods* interceptor_methods) {
    interceptor_methods->SetRecvStatus(recv_status_);
    interceptor_methods->SetRecvTrailingMetadata(metadata_map_);
  }

  void SetFinishInterceptionHookPoint(
      experimental::InterceptorBatchMethods* interceptor_methods) {
    if (recv_status_ == nullptr) return;
    interceptor_methods->AddInterceptionHookPoint(
        experimental::InterceptionHookPoints::POST_RECV_STATUS);
    recv_status_ = nullptr;
  }

  void SetHijackingState(
      experimental::InterceptorBatchMethods* interceptor_methods) {
    hijacked_ = true;
    if (recv_status_ == nullptr) return;
    interceptor_methods->AddInterceptionHookPoint(
        experimental::InterceptionHookPoints::PRE_RECV_STATUS);
  }

 private:
  bool hijacked_ = false;
  ClientContext* client_context_;
  MetadataMap* metadata_map_;
  Status* recv_status_;
  const char* debug_error_string_;
  grpc_status_code status_code_;
  grpc_slice error_message_;
};

/// Straightforward wrapping of the C call object
class Call final {
 public:
  Call()
      : call_hook_(nullptr),
        cq_(nullptr),
        call_(nullptr),
        max_receive_message_size_(-1) {}
  /** call is owned by the caller */
  Call(grpc_call* call, CallHook* call_hook, CompletionQueue* cq)
      : call_hook_(call_hook),
        cq_(cq),
        call_(call),
        max_receive_message_size_(-1) {}

  Call(grpc_call* call, CallHook* call_hook, CompletionQueue* cq,
       experimental::ClientRpcInfo* rpc_info)
      : call_hook_(call_hook),
        cq_(cq),
        call_(call),
        max_receive_message_size_(-1),
        client_rpc_info_(rpc_info) {}

  Call(grpc_call* call, CallHook* call_hook, CompletionQueue* cq,
       int max_receive_message_size, experimental::ServerRpcInfo* rpc_info)
      : call_hook_(call_hook),
        cq_(cq),
        call_(call),
        max_receive_message_size_(max_receive_message_size),
        server_rpc_info_(rpc_info) {}

  void PerformOps(CallOpSetInterface* ops) {
    call_hook_->PerformOpsOnCall(ops, this);
  }

  grpc_call* call() const { return call_; }
  CompletionQueue* cq() const { return cq_; }

  int max_receive_message_size() const { return max_receive_message_size_; }

  experimental::ClientRpcInfo* client_rpc_info() const {
    return client_rpc_info_;
  }

  experimental::ServerRpcInfo* server_rpc_info() const {
    return server_rpc_info_;
  }

 private:
  CallHook* call_hook_;
  CompletionQueue* cq_;
  grpc_call* call_;
  int max_receive_message_size_;
  experimental::ClientRpcInfo* client_rpc_info_ = nullptr;
  experimental::ServerRpcInfo* server_rpc_info_ = nullptr;
};

/// An abstract collection of call ops, used to generate the
/// grpc_call_op structure to pass down to the lower layers,
/// and as it is-a CompletionQueueTag, also massages the final
/// completion into the correct form for consumption in the C++
/// API.
class CallOpSetInterface : public CompletionQueueTag {
 public:
  /// Fills in grpc_op, starting from ops[*nops] and moving
  /// upwards.
  virtual void FillOps(internal::Call* call) = 0;

  /// Get the tag to be used at the core completion queue. Generally, the
  /// value of cq_tag will be "this". However, it can be overridden if we
  /// want core to process the tag differently (e.g., as a core callback)
  virtual void* cq_tag() = 0;

  // This will be called while interceptors are run if the RPC is a hijacked
  // RPC. This should set hijacking state for each of the ops.
  virtual void SetHijackingState() = 0;

  /* Should be called after interceptors are done running */
  virtual void ContinueFillOpsAfterInterception() = 0;

  /* Should be called after interceptors are done running on the finalize result
   * path */
  virtual void ContinueFinalizeResultAfterInterception() = 0;
};

template <class Op1 = CallNoOp<1>, class Op2 = CallNoOp<2>,
          class Op3 = CallNoOp<3>, class Op4 = CallNoOp<4>,
          class Op5 = CallNoOp<5>, class Op6 = CallNoOp<6>>
class CallOpSet;

class InterceptorBatchMethodsImpl
    : public experimental::InterceptorBatchMethods {
 public:
  InterceptorBatchMethodsImpl() {
    for (auto i = 0;
         i < static_cast<int>(
                 experimental::InterceptionHookPoints::NUM_INTERCEPTION_HOOKS);
         i++) {
      hooks_[i] = false;
    }
  }

  virtual ~InterceptorBatchMethodsImpl() {}

  virtual bool QueryInterceptionHookPoint(
      experimental::InterceptionHookPoints type) override {
    return hooks_[static_cast<int>(type)];
  }

  virtual void Proceed() override { /* fill this */
    if (call_->client_rpc_info() != nullptr) {
      return ProceedClient();
    }
    GPR_CODEGEN_ASSERT(call_->server_rpc_info() != nullptr);
    ProceedServer();
  }

  virtual void Hijack() override { /* fill this */
    /* Only the client can hijack when sending down initial metadata */
    GPR_CODEGEN_ASSERT(!reverse_ && ops_ != nullptr &&
                       call_->client_rpc_info() != nullptr);
    auto* rpc_info = call_->client_rpc_info();
    rpc_info->hijacked_ = true;
    rpc_info->hijacked_interceptor_ = curr_iteration_;
    ClearHookPoints();
    ops_->SetHijackingState();
    curr_iteration_++;  // increment so that we recognize that we have already
                        // run the hijacking interceptor
    rpc_info->RunInterceptor(this, curr_iteration_ - 1);
  }

  virtual void AddInterceptionHookPoint(
      experimental::InterceptionHookPoints type) override {
    hooks_[static_cast<int>(type)] = true;
  }

  virtual ByteBuffer* GetSendMessage() override { return send_message_; }

  virtual std::multimap<grpc::string, grpc::string>* GetSendInitialMetadata()
      override {
    return send_initial_metadata_;
  }

  virtual Status GetSendStatus() override {
    return Status(static_cast<StatusCode>(*code_), *error_message_,
                  *error_details_);
  }

  virtual void ModifySendStatus(const Status& status) override {
    *code_ = static_cast<grpc_status_code>(status.error_code());
    *error_details_ = status.error_details();
    *error_message_ = status.error_message();
  }

  virtual std::multimap<grpc::string, grpc::string>* GetSendTrailingMetadata()
      override {
    return send_trailing_metadata_;
  }

  virtual void* GetRecvMessage() override { return recv_message_; }

  virtual std::multimap<grpc::string_ref, grpc::string_ref>*
  GetRecvInitialMetadata() override {
    return recv_initial_metadata_->map();
  }

  virtual Status* GetRecvStatus() override { return recv_status_; }

  virtual std::multimap<grpc::string_ref, grpc::string_ref>*
  GetRecvTrailingMetadata() override {
    return recv_trailing_metadata_->map();
  }

  virtual void SetSendMessage(ByteBuffer* buf) override { send_message_ = buf; }

  virtual void SetSendInitialMetadata(
      std::multimap<grpc::string, grpc::string>* metadata) override {
    send_initial_metadata_ = metadata;
  }

  virtual void SetSendStatus(grpc_status_code* code,
                             grpc::string* error_details,
                             grpc::string* error_message) override {
    code_ = code;
    error_details_ = error_details;
    error_message_ = error_message;
  }

  virtual void SetSendTrailingMetadata(
      std::multimap<grpc::string, grpc::string>* metadata) override {
    send_trailing_metadata_ = metadata;
  }

  virtual void SetRecvMessage(void* message) override {
    recv_message_ = message;
  }

  virtual void SetRecvInitialMetadata(internal::MetadataMap* map) override {
    recv_initial_metadata_ = map;
  }

  virtual void SetRecvStatus(Status* status) override { recv_status_ = status; }

  virtual void SetRecvTrailingMetadata(internal::MetadataMap* map) override {
    recv_trailing_metadata_ = map;
  }

  /* Prepares for Post_recv operations */
  void SetReverse() {
    reverse_ = true;
    ClearHookPoints();
  }

  /* This needs to be set before interceptors are run */
  void SetCall(Call* call) { call_ = call; }

  void SetCallOpSetInterface(CallOpSetInterface* ops) { ops_ = ops; }

  /* Returns true if no interceptors are run. This should be used only by
  subclasses of CallOpSetInterface. SetCall and SetCallOpSetInterface should
  have been called before this. After all the interceptors are done running,
  either ContinueFillOpsAfterInterception or
  ContinueFinalizeOpsAfterInterception will be called. Note that neither of them
  is invoked if there were no interceptors registered.
   */
  bool RunInterceptors() {
    auto* client_rpc_info = call_->client_rpc_info();
    if (client_rpc_info == nullptr ||
        client_rpc_info->interceptors_.size() == 0) {
      return true;
    } else {
      RunClientInterceptors();
      return false;
    }

    auto* server_rpc_info = call_->server_rpc_info();
    if (server_rpc_info == nullptr ||
        server_rpc_info->interceptors_.size() == 0) {
      return true;
    }
    GPR_ASSERT(false);
    RunServerInterceptors();
    return false;
  }

  /* Returns true if no interceptors are run. Returns false otherwise if there
  are interceptors registered. After the interceptors are done running \a f will
  be invoked. This is to be used only by BaseAsyncRequest and SyncRequest. */
  bool RunInterceptors(std::function<void(internal::CompletionQueueTag*)> f) {
    GPR_CODEGEN_ASSERT(reverse_ == true);
    return true;
  }

 private:
  void RunClientInterceptors() {
    auto* rpc_info = call_->client_rpc_info();
    if (!reverse_) {
      curr_iteration_ = 0;
    } else {
      if (rpc_info->hijacked_) {
        curr_iteration_ = rpc_info->hijacked_interceptor_;
        gpr_log(GPR_ERROR, "running from the hijacked %d",
                rpc_info->hijacked_interceptor_);
      } else {
        curr_iteration_ = rpc_info->interceptors_.size() - 1;
      }
    }
    rpc_info->RunInterceptor(this, curr_iteration_);
  }

  void RunServerInterceptors() {
    auto* rpc_info = call_->server_rpc_info();
    if (!reverse_) {
      curr_iteration_ = 0;
    } else {
      curr_iteration_ = rpc_info->interceptors_.size() - 1;
    }
    rpc_info->RunInterceptor(this, curr_iteration_);
  }

  void ProceedClient() {
    curr_iteration_ = reverse_ ? curr_iteration_ - 1 : curr_iteration_ + 1;
    auto* rpc_info = call_->client_rpc_info();
    if (rpc_info->hijacked_ &&
        (!reverse_ && curr_iteration_ == rpc_info->hijacked_interceptor_ + 1)) {
      /* We now need to provide hijacked recv ops to this interceptor */
      ClearHookPoints();
      ops_->SetHijackingState();
      rpc_info->RunInterceptor(this, curr_iteration_ - 1);
      return;
    }
    if (!reverse_) {
      /* We are going down the stack of interceptors */
      if (curr_iteration_ < static_cast<long>(rpc_info->interceptors_.size())) {
        if (rpc_info->hijacked_ &&
            curr_iteration_ > rpc_info->hijacked_interceptor_) {
          /* This is a hijacked RPC and we are done with hijacking */
          ops_->ContinueFillOpsAfterInterception();
        } else {
          rpc_info->RunInterceptor(this, curr_iteration_);
        }
      } else {
        /* we are done running all the interceptors without any hijacking */
        ops_->ContinueFillOpsAfterInterception();
      }
    } else {
      /* We are going up the stack of interceptors */
      if (curr_iteration_ >= 0) {
        /* Continue running interceptors */
        rpc_info->RunInterceptor(this, curr_iteration_);
      } else {
        /* we are done running all the interceptors without any hijacking */
        ops_->ContinueFinalizeResultAfterInterception();
      }
    }
  }

  void ProceedServer() {
    auto* rpc_info = call_->server_rpc_info();
    if (!reverse_) {
      curr_iteration_++;
      if (curr_iteration_ < static_cast<long>(rpc_info->interceptors_.size())) {
        return rpc_info->RunInterceptor(this, curr_iteration_);
      }
    } else {
      curr_iteration_--;
      /* We are going up the stack of interceptors */
      if (curr_iteration_ >= 0) {
        /* Continue running interceptors */
        return rpc_info->RunInterceptor(this, curr_iteration_);
      }
    }
    /* we are done running all the interceptors */
    if (ops_) {
      ops_->ContinueFinalizeResultAfterInterception();
    }
    GPR_CODEGEN_ASSERT(callback_);
    callback_();
  }

  void ClearHookPoints() {
    for (auto i = 0;
         i < static_cast<int>(
                 experimental::InterceptionHookPoints::NUM_INTERCEPTION_HOOKS);
         i++) {
      hooks_[i] = false;
    }
  }

  std::array<bool,
             static_cast<int>(
                 experimental::InterceptionHookPoints::NUM_INTERCEPTION_HOOKS)>
      hooks_;

  int curr_iteration_ = 0;  // Current iterator
  bool reverse_ = false;
  Call* call_ =
      nullptr;  // The Call object is present along with CallOpSet object
  CallOpSetInterface* ops_ = nullptr;
  std::function<void(void)> callback_;

  ByteBuffer* send_message_ = nullptr;

  std::multimap<grpc::string, grpc::string>* send_initial_metadata_;

  grpc_status_code* code_ = nullptr;
  grpc::string* error_details_ = nullptr;
  grpc::string* error_message_ = nullptr;
  Status send_status_;

  std::multimap<grpc::string, grpc::string>* send_trailing_metadata_ = nullptr;
  size_t* send_trailing_metadata_count_ = nullptr;

  void* recv_message_ = nullptr;

  internal::MetadataMap* recv_initial_metadata_ = nullptr;

  Status* recv_status_ = nullptr;

  internal::MetadataMap* recv_trailing_metadata_ = nullptr;

  // void (*hijacking_state_setter_)();
  // void (*continue_after_interception_)();
  // void (*continue_after_reverse_interception_)();
};

/// Primary implementation of CallOpSetInterface.
/// Since we cannot use variadic templates, we declare slots up to
/// the maximum count of ops we'll need in a set. We leverage the
/// empty base class optimization to slim this class (especially
/// when there are many unused slots used). To avoid duplicate base classes,
/// the template parmeter for CallNoOp is varied by argument position.
template <class Op1, class Op2, class Op3, class Op4, class Op5, class Op6>
class CallOpSet : public CallOpSetInterface,
                  public Op1,
                  public Op2,
                  public Op3,
                  public Op4,
                  public Op5,
                  public Op6 {
 public:
  CallOpSet() : cq_tag_(this), return_tag_(this) {}
  void FillOps(Call* call) override {
    done_intercepting_ = false;
    g_core_codegen_interface->grpc_call_ref(call->call());
    call_ =
        *call;  // It's fine to create a copy of call since it's just pointers

    if (RunInterceptors()) {
      ContinueFillOpsAfterInterception();
    } else {
      /* After the interceptors are run, ContinueFillOpsAfterInterception will
       * be run */
    }
  }

  bool FinalizeResult(void** tag, bool* status) override {
    if (done_intercepting_) {
      /* We have already finished intercepting and filling in the results. This
       * round trip from the core needed to be made because interceptors were
       * run  */
      *tag = return_tag_;
      g_core_codegen_interface->grpc_call_unref(call_.call());
      return true;
    }

    this->Op1::FinishOp(status);
    this->Op2::FinishOp(status);
    this->Op3::FinishOp(status);
    this->Op4::FinishOp(status);
    this->Op5::FinishOp(status);
    this->Op6::FinishOp(status);

    if (RunInterceptorsPostRecv()) {
      *tag = return_tag_;
      g_core_codegen_interface->grpc_call_unref(call_.call());
      return true;
    }

    /* Interceptors are going to be run, so we can't return the tag just yet.
    After the interceptors are run, ContinueFinalizeResultAfterInterception */
    return false;
  }

  void set_output_tag(void* return_tag) { return_tag_ = return_tag; }

  void* cq_tag() override { return cq_tag_; }

  /// set_cq_tag is used to provide a different core CQ tag than "this".
  /// This is used for callback-based tags, where the core tag is the core
  /// callback function. It does not change the use or behavior of any other
  /// function (such as FinalizeResult)
  void set_cq_tag(void* cq_tag) { cq_tag_ = cq_tag; }

  // This will be called while interceptors are run if the RPC is a hijacked
  // RPC. This should set hijacking state for each of the ops.
  void SetHijackingState() override {
    this->Op1::SetHijackingState(&interceptor_methods_);
    this->Op2::SetHijackingState(&interceptor_methods_);
    this->Op3::SetHijackingState(&interceptor_methods_);
    this->Op4::SetHijackingState(&interceptor_methods_);
    this->Op5::SetHijackingState(&interceptor_methods_);
    this->Op6::SetHijackingState(&interceptor_methods_);
  }

  /* Should be called after interceptors are done running */
  void ContinueFillOpsAfterInterception() override {
    static const size_t MAX_OPS = 6;
    grpc_op ops[MAX_OPS];
    size_t nops = 0;
    this->Op1::AddOp(ops, &nops);
    this->Op2::AddOp(ops, &nops);
    this->Op3::AddOp(ops, &nops);
    this->Op4::AddOp(ops, &nops);
    this->Op5::AddOp(ops, &nops);
    this->Op6::AddOp(ops, &nops);
    GPR_CODEGEN_ASSERT(GRPC_CALL_OK ==
                       g_core_codegen_interface->grpc_call_start_batch(
                           call_.call(), ops, nops, cq_tag(), nullptr));
  }

  /* Should be called after interceptors are done running on the finalize result
   * path */
  void ContinueFinalizeResultAfterInterception() override {
    done_intercepting_ = true;
    GPR_CODEGEN_ASSERT(GRPC_CALL_OK ==
                       g_core_codegen_interface->grpc_call_start_batch(
                           call_.call(), nullptr, 0, cq_tag(), nullptr));
  }

 private:
  /* Returns true if no interceptors need to be run */
  bool RunInterceptors() {
    this->Op1::SetInterceptionHookPoint(&interceptor_methods_);
    this->Op2::SetInterceptionHookPoint(&interceptor_methods_);
    this->Op3::SetInterceptionHookPoint(&interceptor_methods_);
    this->Op4::SetInterceptionHookPoint(&interceptor_methods_);
    this->Op5::SetInterceptionHookPoint(&interceptor_methods_);
    this->Op6::SetInterceptionHookPoint(&interceptor_methods_);
    interceptor_methods_.SetCallOpSetInterface(this);
    interceptor_methods_.SetCall(&call_);
    // interceptor_methods_.SetFunctions(ContinueFillOpsAfterInterception,
    // SetHijackingState, ContinueFinalizeResultAfterInterception);
    return interceptor_methods_.RunInterceptors();
  }
  /* Returns true if no interceptors need to be run */
  bool RunInterceptorsPostRecv() {
    interceptor_methods_.SetReverse();
    this->Op1::SetFinishInterceptionHookPoint(&interceptor_methods_);
    this->Op2::SetFinishInterceptionHookPoint(&interceptor_methods_);
    this->Op3::SetFinishInterceptionHookPoint(&interceptor_methods_);
    this->Op4::SetFinishInterceptionHookPoint(&interceptor_methods_);
    this->Op5::SetFinishInterceptionHookPoint(&interceptor_methods_);
    this->Op6::SetFinishInterceptionHookPoint(&interceptor_methods_);
    return interceptor_methods_.RunInterceptors();
  }

  void* cq_tag_;
  void* return_tag_;
  Call call_;
  bool done_intercepting_ = false;
  InterceptorBatchMethodsImpl interceptor_methods_;
};

}  // namespace internal
}  // namespace grpc

#endif  // GRPCPP_IMPL_CODEGEN_CALL_H