/*
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * 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.
 */

#pragma once

#include <folly/CPortability.h>
#include <folly/Optional.h>
#include <thrift/lib/cpp2/protocol/Protocol.h>

namespace apache {
namespace thrift {
namespace detail {

/**
 * Default stub implementation for StructReadState for protocols that don't
 * support it.
 */
template <class Protocol>
struct ProtocolReaderStructReadState {
  std::string fieldName_;
  int16_t fieldId;
  apache::thrift::protocol::TType fieldType;

  constexpr static bool kAcceptsContext = false;

  void readStructBegin(Protocol* iprot) { iprot->readStructBegin(fieldName_); }

  void readStructEnd(Protocol* iprot) { iprot->readStructEnd(); }

  void readFieldBegin(Protocol* iprot) {
    iprot->readFieldBegin(fieldName_, fieldType, fieldId);
  }

  void readFieldBeginNoInline(Protocol* iprot) {
    iprot->readFieldBegin(fieldName_, fieldType, fieldId);
  }

  void readFieldEnd(Protocol* iprot) { iprot->readFieldEnd(); }

  /**
   * Transition to parsing next field. Under the hood it handles
   * (readFieldEnd + readFieldBegin).
   *
   * The return value indicates if the next field on the wire is the expected
   * one (i.e. same field type and field id as nextFieldType and nextFieldId),
   * but may have false negatives.
   *
   * Note, on success (i.e. return value is true), the read state is unchanged.
   *
   * Note2, this function is for making transitions faster and is BEST EFFORT.
   * It may return `false` even if the next field is the expected one, but it's
   * guaranteed to never return `true` when the next field is not the expected
   * one.
   *
   * @return true  if the next field on the wire is the expected one.
   */
  FOLLY_ALWAYS_INLINE bool advanceToNextField(
      Protocol* iprot,
      int16_t currFieldId,
      int16_t /*nextFieldId*/,
      TType /*nextFieldType*/) {
    if (currFieldId != 0) {
      iprot->readFieldEnd();
    }
    iprot->readFieldBegin(fieldName_, fieldType, fieldId);
    return false;
  }

  /*
   * This is used in generated deserialization code only. When deserializing
   * fields in "non-advanceToNextField" case, we delegate the type check to
   * each protocol since some protocol may not encode type information.
   */
  FOLLY_ALWAYS_INLINE bool isCompatibleWithType(
      Protocol* /*iprot*/, TType expectedFieldType) {
    return fieldType == expectedFieldType;
  }

  void skip(Protocol* iprot) { iprot->skip(fieldType); }
  template <class TypeClass, class Type>
  folly::Optional<folly::IOBuf> tryFastSkip(
      Protocol* /*iprot*/, int16_t /*fieldId*/, TType /*fieldType*/) {
    return {};
  }

  std::string& fieldName() { return fieldName_; }

  bool atStop() { return fieldType == protocol::T_STOP; }

  void afterAdvanceFailure(Protocol* /*iprot*/) {}

  void beforeSubobject(Protocol* /* iprot */) {}
  void afterSubobject(Protocol* /* iprot */) {}

  template <typename StructTraits>
  void fillFieldTraitsFromName() {
    StructTraits::translateFieldName(fieldName(), fieldId, fieldType);
  }
};

} // namespace detail
} // namespace thrift
} // namespace apache