/* Copyright (c) 2016 PaddlePaddle Authors. All Rights Reserve.

   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 "paddle/framework/grad_op_desc_maker.h"
#include "paddle/framework/op_info.h"
#include "paddle/framework/op_proto_maker.h"
#include "paddle/framework/operator.h"

namespace paddle {
namespace framework {
namespace details {

enum OpInfoFillType {
  kOperator = 0,
  kOpProtoAndCheckerMaker = 1,
  kGradOpDescMaker = 2
};

template <typename T>
struct OpInfoFillTypeID {
  static constexpr OpInfoFillType ID() {
    return std::is_base_of<OperatorBase, T>::value
               ? kOperator
               : (std::is_base_of<OpProtoAndCheckerMaker, T>::value
                      ? kOpProtoAndCheckerMaker
                      : (std::is_base_of<GradOpDescMakerBase, T>::value
                             ? kGradOpDescMaker
                             : static_cast<OpInfoFillType>(-1)));
  }
};

template <typename T, OpInfoFillType = OpInfoFillTypeID<T>::ID()>
struct OpInfoFiller;

template <size_t I, bool at_end, typename... ARGS>
class OperatorRegistrarRecursive;

template <size_t I, typename... ARGS>
class OperatorRegistrarRecursive<I, false, ARGS...> {
 public:
  using T = typename std::tuple_element<I, std::tuple<ARGS...>>::type;
  OperatorRegistrarRecursive(const char* op_type, OpInfo* info) {
    OpInfoFiller<T> fill;
    fill(op_type, info);
    constexpr auto size = sizeof...(ARGS);
    OperatorRegistrarRecursive<I + 1, I + 1 == size, ARGS...> reg(op_type,
                                                                  info);
    (void)(reg);
  }
};

template <size_t I, typename... ARGS>
class OperatorRegistrarRecursive<I, true, ARGS...> {
 public:
  OperatorRegistrarRecursive(const char* op_type, OpInfo* info) {}
};

template <typename T>
struct OpInfoFiller<T, kOperator> {
  void operator()(const char* op_type, OpInfo* info) const {
    info->creator_ = [](const std::string& type, const VariableNameMap& inputs,
                        const VariableNameMap& outputs,
                        const AttributeMap& attrs) {
      return new T(type, inputs, outputs, attrs);
    };
  }
};

template <typename T>
struct OpInfoFiller<T, kOpProtoAndCheckerMaker> {
  void operator()(const char* op_type, OpInfo* info) const {
    info->proto_ = new OpProto;
    info->checker_ = new OpAttrChecker();
    auto maker = T(info->proto_, info->checker_);
    maker.Validate();
    info->proto_->set_type(op_type);
    PADDLE_ENFORCE(
        info->proto_->IsInitialized(),
        "Fail to initialize %s's OpProto, because %s is not initialized",
        op_type, info->proto_->InitializationErrorString());
  }
};

template <typename T>
struct OpInfoFiller<T, kGradOpDescMaker> {
  void operator()(const char* op_type, OpInfo* info) const {
    info->grad_op_maker_ = [](
        const OpDescBind& fwd_op,
        const std::unordered_set<std::string>& no_grad_set) {
      T maker(fwd_op, no_grad_set);
      return maker();
    };
  }
};
}  // namespace details

}  // namespace framework
}  // namespace paddle