/*!
 * @file factory.h
 * @brief Contains a base class for a factory.
 *
 * A factory contains an array of inputs, an array of outputs and an operation.
 * You can update some elements in the array of inputs and then call
 * `Factory::Update()` to update the outputs (it will run the operation only if
 * some input elements are changed since last update).
 *
 * @author cathook
 */

#ifndef __MEOWPP_UTILITY_FACTORY_H__
#define __MEOWPP_UTILITY_FACTORY_H__

#include "operation.h"
#include "pointer.h"
#include "self.h"


namespace meow {

namespace factory_types {


/*!
 * @brief A base class for kinds of factory classes.
 */
class Base {
 protected:
  struct BaseData {
    Pointer<Operation const> oper;
    Pointer<Pointer<Object const>> inputs;
    Pointer<Pointer<Object>> outputs;

    //! An array with each elements points to the input elements with
    //! non-constant type.
    Pointer<Pointer<Object>> non_const_inputs;

    //! An array with each elements points to the output elements with
    //! constant type.
    Pointer<Pointer<Object const>> const_outputs;

    /*!
     * @brief Constructor.
     * @param [in] arg_oper The operation this factory should run.
     * @param [in] arg_inputs A pointer points to the array of the input
     *     elements.
     * @param [in] arg_outputs A pointer points to the array of the output
     *     elements.
     */
    BaseData(Pointer<Operation const> const& arg_oper,
             Pointer<Pointer<Object const>> const& arg_inputs,
             Pointer<Pointer<Object>> const& arg_outputs):
        oper(arg_oper),
        inputs(arg_inputs),
        outputs(arg_outputs),
        non_const_inputs(new Pointer<Object>[oper->inputs_size()], ARRAY, true),
        const_outputs(
            new Pointer<Object const>[oper->outputs_size()], ARRAY, true) {
      for (int i = 0, i_max = oper->inputs_size(); i < i_max; ++i) {
        non_const_inputs[i] = Pointer<Object>(
            const_cast<Object*>(inputs[i].address()), SINGLE, false);
      }
      for (int i = 0, i_max = oper->outputs_size(); i < i_max; ++i) {
        const_outputs[i] = Pointer<Object const>(
            outputs[i].address(), SINGLE, false);
      }
    };
  };

  Base() {}

 public:
  virtual ~Base() {}

  /*!
   * @brief Updates the output elements by re-run the operation.
   */
  virtual State Update() const = 0;

  /*!
   * @brief Returns whether the last time calling `Update()` did update really
   *     or not.
   *
   * If the input elements were not changed before `Update()` be called, it
   * might be returns false (depends on how it implements).
   */
  virtual bool HasRedo() const = 0;

  /*!
   * @brief Gets the operation.
   */
  virtual Pointer<Operation const> operation() const = 0;

  /*!
   * @brief Gets the pointer points to the array of input elements.
   */
  virtual Pointer<Pointer<Object>> inputs() const = 0;

  /*!
   * @brief Gets the pointer points to the array of output elements.
   */
  virtual Pointer<Pointer<Object const>> outputs() const = 0;
};


/*!
 * An implement of the factory class.
 *
 * When the function `Update()` be called, no matter whether the input elements
 * has changed or not, it will do the operation.
 */
class CheckOff : public Base {
 private:
  struct Data : Base::BaseData {
    Data(Pointer<Operation const> const& arg_oper,
         Pointer<Pointer<Object const>> const& arg_inputs,
         Pointer<Pointer<Object>> const& arg_outputs) :
        BaseData(arg_oper, arg_inputs, arg_outputs) {}
  };

  Self<Data> const self_;

 public:

  /*!
   * @brief Constructor.
   * @param [in] arg_oper The operation for this factory to run.
   * @param [in] arg_inputs A pointer points to the array of the pointer points
   *     to the input elements.
   * @param [in] arg_outputs A pointer points to the array of the pointer points
   *     to the output elements.
   */
  CheckOff(Pointer<Operation const> const& arg_oper,
           Pointer<Pointer<Object const>> const& arg_inputs,
           Pointer<Pointer<Object>> const& arg_outputs) :
      self_(Data(arg_oper, arg_inputs, arg_outputs)) {}

  /*!
   * @brief Updates the output elements by running the operation.
   */
  State Update() const {
    return self_->oper->Operate(self_->inputs, self_->outputs);
  }

  /*!
   * @brief It will always return true.
   */
  bool HasRedo() const {
    return true;
  }

  /*!
   * @brief Gets the operation.
   */
  virtual Pointer<Operation const> operation() const {
    return self_->oper;
  }

  /*!
   * @brief Gets the pointer points to the array of input elements.
   */
  Pointer<Pointer<Object>> inputs() const {
    return self_->non_const_inputs;
  }

  /*!
   * @brief Gets the pointer points to the array of output elements.
   */
  Pointer<Pointer<Object const>> outputs() const {
    return self_->const_outputs;
  }

};


/*!
 * An implement of the factory class.
 *
 * It will check whether the input elements has changed before running the
 * operation.
 */
class CheckOn : public Base {
 private:
  struct Data : Base::BaseData {
    //! Stores the last input elements which are using to check whether the
    //! input elements have changed or not.
    Pointer<Pointer<Object>> old_inputs;

    //! Stores the state returned by the operation last time.
    State last_state;

    //! Stores whether the last `Update()` run the operation or not.
    bool has_redo;

    //! Stores whether it has not run the `Update()` yet.
    bool first_time;
    
    Data(Pointer<Operation const> const& arg_oper,
         Pointer<Pointer<Object const>> const& arg_inputs,
         Pointer<Pointer<Object>> const& arg_outputs) :
        BaseData(arg_oper, arg_inputs, arg_outputs),
        old_inputs(new Pointer<Object>[oper->inputs_size()], ARRAY, true),
        has_redo(false),
        first_time(true) {
      for (int i = 0, i_max = oper->inputs_size(); i < i_max; ++i) {
        old_inputs[i] = Pointer<Object>(inputs[i]->Copy(), SINGLE, true);
      }
    }
  };

  Self<Data> const self_;

 public:

  /*!
   * @brief Constructor.
   * @param [in] arg_oper The operation this factory should run.
   * @param [in] arg_inputs A pointer points to the array of the input
   *     elements.
   * @param [in] arg_outputs A pointer points to the array of the output
   *     elements.
   */
  CheckOn(Pointer<Operation const> const& arg_oper,
          Pointer<Pointer<Object const>> const& arg_inputs,
          Pointer<Pointer<Object>> const& arg_outputs) :
      self_(Data(arg_oper, arg_inputs, arg_outputs)) {}

  /*!
   * @brief Updates the output elements if needs.
   *
   * It will check whether the input elements different from the old ones first.
   */
  State Update() const {
    bool needs_to_update = self_->first_time;
    if (!needs_to_update) {
      for (int i = 0, i_max = self_->oper->inputs_size(); i < i_max; ++i) {
        Object const* old = self_->old_inputs[i].address();
        Object const* cur = self_->inputs[i].address();
        if (!old->Equals(cur)) {
          needs_to_update = true;
          break;
        }
      }
    }
    if (!needs_to_update) {
      self_()->has_redo = false;
    } else {
      for (int i = 0, i_max = self_->oper->inputs_size(); i < i_max; ++i) {
        Object* old = self_->old_inputs[i].address();
        Object const* cur = self_->inputs[i].address();
        old->CopyFrom(cur);
      }
      self_()->last_state = self_->oper->Operate(self_->inputs, self_->outputs);
      self_()->has_redo = true;
    }
    self_()->first_time = false;
    return self_->last_state;
  }

  /*!
   * @brief Returns whether the output elements have been re-generated by
   *     running the operation again.
   *
   * It will check whether the input elements different from the old ones first.
   */
  bool HasRedo() const {
    return self_->has_redo;
  }

  /*!
   * @brief Gets the operation.
   */
  virtual Pointer<Operation const> operation() const {
    return self_->oper;
  }

  /*!
   * @brief Gets the array of the input elements.
   */
  Pointer<Pointer<Object>> inputs() const {
    return self_->non_const_inputs;
  }

  /*!
   * @brief Gets the array of the output elements.
   */
  Pointer<Pointer<Object const>> outputs() const {
    return self_->const_outputs;
  }

};

}  // factory_types


/*!
 * @brief A class which contains input elements, output elements and an
 *   operation.
 */
class Factory : public Object {
 private:

  Pointer<factory_types::Base> factory_;

 public:

  /*!
   * @brief Constructor.
   */
  Factory(Pointer<Operation const> const& arg_oper,
          Pointer<Pointer<Object const>> const& arg_inputs,
          Pointer<Pointer<Object>> const& arg_outputs,
          bool arg_check_before_update) {
    if (arg_check_before_update) {
      factory_ = Pointer<factory_types::Base>(
          new factory_types::CheckOn(
              arg_oper, arg_inputs, arg_outputs), SINGLE, true);
    } else {
      factory_ = Pointer<factory_types::Base>(
          new factory_types::CheckOff(
              arg_oper, arg_inputs, arg_outputs), SINGLE, true);
    }
  }

  /*!
   * @brief Updates the output elements.
   */
  State Update() const {
    return factory_->Update();
  }

  /*!
   * @brief Returns whether the output elements have been re-generated by
   *     running the operation again.
   */
  bool HasRedo() const {
    return factory_->HasRedo();
  }

  /*!
   * @brief Gets the operation.
   */
  Pointer<Operation const> operation() const {
    return factory_->operation();
  }

  /*!
   * @brief Gets the array of the input elements.
   */
  Pointer<Pointer<Object>> inputs() const {
    return factory_->inputs();
  }

  /*!
   * @brief Gets the array of the output elements.
   */
  Pointer<Pointer<Object const>> outputs() const {
    return factory_->outputs();
  }
  
  Object* Copy() const {
    return NULL;
  }

  Object* CopyFrom(Object const* another_factory) {
    return NULL;
  }
  
  bool Equals(Object const* another_factory) {
    return false;
  }

#ifdef MEOWPP_UTILITY_FACTORY_TESTING
  friend class FactoryTest;
#endif

};

}  // meow

#endif  // __MEOWPP_UTILITY_FACTORY_H__