/* 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 <string>
#include <unordered_map>
#include <vector>

#include "paddle/framework/variable.h"

namespace paddle {
namespace framework {

class Scope;

/**
 * @brief Scope that manage all variables.
 *
 * Scope is an association of a name to Variable. All variables belong to
 * Scope. You need to specify a scope to run a Net, i.e., `net.Run(&scope)`.
 * One net can run in different scopes and update different variable in the
 * scope.
 */
class Scope {
 public:
  /**
   * @brief Initialize s Scope without parent.
   */
  Scope() {}

  /**
   * @brief Initialize a Scope with parent.
   */
  explicit Scope(const std::shared_ptr<Scope>& parent) : parent_(parent) {}

  /**
   * @brief Create Variable
   *
   * Create Variable in this Scope. Return the exist one if Variable already
   * been created.
   */
  Variable* CreateVariable(const std::string& name) {
    auto var = GetVariable(name);
    if (var) {
      return var;
    } else {
      auto ptr = new Variable();
      name_to_var_[name] = std::unique_ptr<Variable>(ptr);
      var_to_name_[ptr] = name;
      return GetVariable(name);
    }
  }

  /**
   * @brief Get Variable.
   *
   * Get Variable from this Scope, this function will recursive find Variable
   * from it's parent scope. Return nullptr if not found.
   */
  Variable* GetVariable(const std::string& name) const {
    auto it = name_to_var_.find(name);
    if (it != name_to_var_.end()) {
      return it->second.get();
    } else if (parent_ != nullptr) {
      return parent_->GetVariable(name);
    } else {
      return nullptr;
    }
  }

  /**
   * @brief If this scope has a Var named name.
   *
   * Find if there is a Variable in this scope and it's parent scope
   */
  bool HasVariable(const std::string& name) const {
    return (name_to_var_.find(name) != name_to_var_.end() ||
            (parent_ && parent_->HasVariable(name)));
  }

  std::string GetVariableName(Variable* const var) const {
    try {
      return var_to_name_.at(var);
    } catch (...) {
      return "";
    }
  }

 private:
  std::unordered_map<Variable*, std::string> var_to_name_;
  std::unordered_map<std::string, std::unique_ptr<Variable>> name_to_var_;
  std::shared_ptr<Scope> parent_{nullptr};
};

}  // namespace framework
}  // namespace paddle