////////////////////////////////////////////////////////////////////////////////
// Copyright (c) 2014-2023, Lawrence Livermore National Security, LLC.
// Produced at the Lawrence Livermore National Laboratory.
// Written by the LBANN Research Team (B. Van Essen, et al.) listed in
// the CONTRIBUTORS file. <lbann-dev@llnl.gov>
//
// LLNL-CODE-697807.
// All rights reserved.
//
// This file is part of LBANN: Livermore Big Artificial Neural Network
// Toolkit. For details, see http://software.llnl.gov/LBANN or
// https://github.com/LLNL/LBANN.
//
// Licensed under the Apache License, Version 2.0 (the "Licensee"); 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.
//
// load_model .hpp .cpp - Callbacks to load pretrained model(s)
////////////////////////////////////////////////////////////////////////////////

#ifndef LBANN_CALLBACKS_CALLBACK_LOAD_MODEL_HPP_INCLUDED
#define LBANN_CALLBACKS_CALLBACK_LOAD_MODEL_HPP_INCLUDED

#include <utility>

#include "lbann/callbacks/callback.hpp"

#include <google/protobuf/message.h>

// Forward-declare protobuf classes
namespace lbann_data {
class Model;
}

namespace lbann {
namespace callback {

/**
 * Load pretrained model from file
 */
class load_model : public callback_base
{
public:
  /**
   * @param dirs directories from which to load model
   * @param extension file extension e.g., model, state ......
   */
  load_model(std::vector<std::string> dirs, std::string extension = "prototext")
    : callback_base(),
      m_dirs(std::move(dirs)),
      m_extension(std::move(extension)),
      m_loaded(false)
  {}
  load_model(const load_model&) = default;
  load_model& operator=(const load_model&) = default;
  load_model* copy() const override { return new load_model(*this); }

  inline void add_dir(const std::string& dir) { m_dirs.emplace_back(dir); }

  void on_train_begin(model* m) override;

  void on_test_begin(model* m) override;

  std::string name() const override { return "load model"; }

  /** @name Serialization */
  ///@{

  /** @brief Store state to archive for checkpoint and restart */
  template <class Archive>
  void serialize(Archive& ar);

  ///@}

private:
  friend class lbann::model;
  friend class cereal::access;
  load_model() = default;

private:
  /** Add callback specific data to prototext */
  void write_specific_proto(lbann_data::Callback& proto) const final;

  std::vector<std::string> m_dirs; // director(ies) to load pretrained model(s)
  /// Disables the normal behavior of saving when training is complete
  std::string m_extension; // file extension

  /// Flag to indicate if the model has already been loaded
  bool m_loaded;
};

// Builder function
std::unique_ptr<callback_base>
build_load_model_callback_from_pbuf(const google::protobuf::Message&,
                                    std::shared_ptr<lbann_summary> const&);

} // namespace callback
} // namespace lbann

#endif // LBANN_CALLBACKS_CALLBACK_LOAD_MODEL_HPP_INCLUDED
