/*=========================================================================
 *
 *  Copyright NumFOCUS
 *
 *  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
 *
 *         https://www.apache.org/licenses/LICENSE-2.0.txt
 *
 *  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.
 *
 *=========================================================================*/
#ifndef itkCommand_h
#define itkCommand_h

#include "itkObject.h"
#include "itkObjectFactory.h"
#include <functional>

namespace itk
{
/** \class Command
 *  \brief Superclass for callback/observer methods.
 *
 * Command is an implementation of the command design pattern that is used
 * in callbacks (such as StartMethod(), ProgressMethod(), and EndMethod()) in
 * ITK. itk::Object implements a Subject/Observer pattern. When a subject
 * needs to notify a observer, it does so using a itk::Command. The Execute
 * method is called to run the command.
 *
 * \ingroup ITKSystemObjects
 * \ingroup ITKCommon
 *
 * \sphinx
 * \sphinxexample{Core/Common/ObserveAnEvent,Observe An Event}
 * \endsphinx
 */

// The superclass that all commands should be subclasses of
class ITKCommon_EXPORT Command : public Object
{
public:
  ITK_DISALLOW_COPY_AND_MOVE(Command);

  /** Standard class type aliases. */
  using Self = Command;
  using Superclass = Object;
  using Pointer = SmartPointer<Self>;
  using ConstPointer = SmartPointer<const Self>;

  /** \see LightObject::GetNameOfClass() */
  itkOverrideGetNameOfClassMacro(Command);

  /** Abstract method that defines the action to be taken by the command. */
  virtual void
  Execute(Object * caller, const EventObject & event) = 0;

  /** Abstract method that defines the action to be taken by the command.
   * This variant is expected to be used when requests comes from a
   * const Object */
  virtual void
  Execute(const Object * caller, const EventObject & event) = 0;

protected:
  Command();
  ~Command() override;
};

// some implementations for several callback types

/** \class MemberCommand
 *  \brief A Command subclass that calls a pointer to a member function.
 *
 *  MemberCommand calls a pointer to a member function with the same
 *  arguments as Execute on Command.
 *
 * \ingroup ITKSystemObjects
 * \ingroup ITKCommon
 */
template <typename T>
class ITK_TEMPLATE_EXPORT MemberCommand : public Command
{
public:
  ITK_DISALLOW_COPY_AND_MOVE(MemberCommand);

  /** pointer to a member function that takes a Object* and the event */
  /** @ITKStartGrouping */
  using TMemberFunctionPointer = void (T::*)(Object *, const EventObject &);
  using TConstMemberFunctionPointer = void (T::*)(const Object *, const EventObject &);
  /** @ITKEndGrouping */
  /** Standard class type aliases. */
  using Self = MemberCommand;
  using Pointer = SmartPointer<Self>;

  /** Method for creation through the object factory. */
  itkNewMacro(Self);

  /** \see LightObject::GetNameOfClass() */
  itkOverrideGetNameOfClassMacro(MemberCommand);

  /**  Set the callback function along with the object that it will
   *  be invoked on. */
  void
  SetCallbackFunction(T * object, TMemberFunctionPointer memberFunction)
  {
    m_This = object;
    m_MemberFunction = memberFunction;
  }

  void
  SetCallbackFunction(T * object, TConstMemberFunctionPointer memberFunction)
  {
    m_This = object;
    m_ConstMemberFunction = memberFunction;
  }

  /**  Invoke the member function. */
  void
  Execute(Object * caller, const EventObject & event) override
  {
    if (m_MemberFunction)
    {
      (m_This->*(m_MemberFunction))(caller, event);
    }
  }

  /**  Invoke the member function with a const object. */
  void
  Execute(const Object * caller, const EventObject & event) override
  {
    if (m_ConstMemberFunction)
    {
      (m_This->*(m_ConstMemberFunction))(caller, event);
    }
  }

protected:
  T *                         m_This{ nullptr };
  TMemberFunctionPointer      m_MemberFunction{ nullptr };
  TConstMemberFunctionPointer m_ConstMemberFunction{ nullptr };

  MemberCommand() = default;

  ~MemberCommand() override = default;
};

/** \class ReceptorMemberCommand
 *  \brief A Command subclass that calls a pointer to a member function.
 *
 *  ReceptorMemberCommand calls a pointer to a member function with
 *  only and itk::EventObject as argument
 *
 * \ingroup ITKSystemObjects
 * \ingroup ITKCommon
 */
template <typename T>
class ITK_TEMPLATE_EXPORT ReceptorMemberCommand : public Command
{
public:
  ITK_DISALLOW_COPY_AND_MOVE(ReceptorMemberCommand);

  /** pointer to a member function that takes a Object* and the event */
  using TMemberFunctionPointer = void (T::*)(const EventObject &);

  /** Standard class type aliases. */
  using Self = ReceptorMemberCommand;
  using Pointer = SmartPointer<Self>;

  /** Method for creation through the object factory. */
  itkNewMacro(Self);

  /** \see LightObject::GetNameOfClass() */
  itkOverrideGetNameOfClassMacro(ReceptorMemberCommand);

  /**  Set the callback function along with the object that it will
   *  be invoked on. */
  void
  SetCallbackFunction(T * object, TMemberFunctionPointer memberFunction)
  {
    m_This = object;
    m_MemberFunction = memberFunction;
  }

  /**  Invoke the member function. */
  void
  Execute(Object *, const EventObject & event) override
  {
    if (m_MemberFunction)
    {
      (m_This->*(m_MemberFunction))(event);
    }
  }

  /**  Invoke the member function with a const object */
  void
  Execute(const Object *, const EventObject & event) override
  {
    if (m_MemberFunction)
    {
      (m_This->*(m_MemberFunction))(event);
    }
  }

protected:
  T *                    m_This{ nullptr };
  TMemberFunctionPointer m_MemberFunction{ nullptr };

  ReceptorMemberCommand() = default;

  ~ReceptorMemberCommand() override = default;
};

/** \class SimpleMemberCommand
 *  \brief A Command subclass that calls a pointer to a member function.
 *
 *  SimpleMemberCommand calls a pointer to a member function with no
 *  arguments.
 *
 * \ingroup ITKSystemObjects
 * \ingroup ITKCommon
 */
template <typename T>
class ITK_TEMPLATE_EXPORT SimpleMemberCommand : public Command
{
public:
  ITK_DISALLOW_COPY_AND_MOVE(SimpleMemberCommand);

  /** A method callback. */
  using TMemberFunctionPointer = void (T::*)();

  /** Standard class type aliases. */
  using Self = SimpleMemberCommand;
  using Pointer = SmartPointer<Self>;

  /** \see LightObject::GetNameOfClass() */
  itkOverrideGetNameOfClassMacro(SimpleMemberCommand);

  /** Method for creation through the object factory. */
  itkNewMacro(Self);

  /** Specify the callback function. */
  void
  SetCallbackFunction(T * object, TMemberFunctionPointer memberFunction)
  {
    m_This = object;
    m_MemberFunction = memberFunction;
  }

  /** Invoke the callback function. */
  void
  Execute(Object *, const EventObject &) override
  {
    if (m_MemberFunction)
    {
      (m_This->*(m_MemberFunction))();
    }
  }

  void
  Execute(const Object *, const EventObject &) override
  {
    if (m_MemberFunction)
    {
      (m_This->*(m_MemberFunction))();
    }
  }

protected:
  T *                    m_This{ nullptr };
  TMemberFunctionPointer m_MemberFunction{ nullptr };

  SimpleMemberCommand() = default;

  ~SimpleMemberCommand() override = default;
};

/** \class SimpleConstMemberCommand
 *  \brief A Command subclass that calls a pointer to a member function.
 *
 *  SimpleConstMemberCommand calls a pointer to a member function with no
 *  arguments.
 *
 * \ingroup ITKSystemObjects
 * \ingroup ITKCommon
 */
template <typename T>
class ITK_TEMPLATE_EXPORT SimpleConstMemberCommand : public Command
{
public:
  ITK_DISALLOW_COPY_AND_MOVE(SimpleConstMemberCommand);

  /** A const member method callback. */
  using TMemberFunctionPointer = void (T::*)() const;

  /** Standard class type aliases. */
  using Self = SimpleConstMemberCommand;
  using Pointer = SmartPointer<Self>;

  /** \see LightObject::GetNameOfClass() */
  itkOverrideGetNameOfClassMacro(SimpleConstMemberCommand);

  /** Method for creation through the object factory. */
  itkNewMacro(Self);

  /** Specify the const member method callback. */
  void
  SetCallbackFunction(const T * object, TMemberFunctionPointer memberFunction)
  {
    m_This = object;
    m_MemberFunction = memberFunction;
  }

  /** Invoke the const member method callback. */
  void
  Execute(Object *, const EventObject &) override
  {
    if (m_MemberFunction)
    {
      (m_This->*(m_MemberFunction))();
    }
  }

  void
  Execute(const Object *, const EventObject &) override
  {
    if (m_MemberFunction)
    {
      (m_This->*(m_MemberFunction))();
    }
  }

protected:
  const T *              m_This{ nullptr };
  TMemberFunctionPointer m_MemberFunction{ nullptr };

  SimpleConstMemberCommand() = default;

  ~SimpleConstMemberCommand() override = default;
};

/** \class CStyleCommand
 *  \brief A Command subclass that calls a pointer to a C function.
 *
 *  CStyleCommand calls a pointer to a C function with the following
 *  arguments void func(Object *,void *clientdata)
 *  The clientdata is data that the command wants passed to itself
 *  each time.
 *
 * \ingroup ITKSystemObjects
 * \ingroup ITKCommon
 */

class ITKCommon_EXPORT CStyleCommand : public Command
{
public:
  /** Typedefs for C-style callbacks. */
  /** @ITKStartGrouping */
  using FunctionPointer = void (*)(Object *, const EventObject &, void *);
  using ConstFunctionPointer = void (*)(const Object *, const EventObject &, void *);
  using DeleteDataFunctionPointer = void (*)(void *);
  /** @ITKEndGrouping */
  /** Standard class type aliases. */
  using Self = CStyleCommand;
  using Pointer = SmartPointer<Self>;

  /** \see LightObject::GetNameOfClass() */
  itkOverrideGetNameOfClassMacro(CStyleCommand);

  /** Method for creation through the object factory. */
  itkNewMacro(Self);

  /** Set the client data that will be passed into the C function when
   * it is called. */
  void
  SetClientData(void * cd);

  /** Set the C callback function pointer to be called at Execute time. */
  /** @ITKStartGrouping */
  void
  SetCallback(FunctionPointer f);
  void
  SetConstCallback(ConstFunctionPointer f);
  /** @ITKEndGrouping */
  /** Set the callback to delete the client data. */
  void
  SetClientDataDeleteCallback(DeleteDataFunctionPointer f);

  /** Execute the callback function. */
  void
  Execute(Object * caller, const EventObject & event) override;

  /** Execute the callback function with a const Object */
  void
  Execute(const Object * caller, const EventObject & event) override;

protected:
  CStyleCommand();
  ~CStyleCommand() override;

  void *                    m_ClientData{ nullptr };
  FunctionPointer           m_Callback{ nullptr };
  ConstFunctionPointer      m_ConstCallback{ nullptr };
  DeleteDataFunctionPointer m_ClientDataDeleteCallback{ nullptr };
};


/** \class FunctionCommand
 *  \brief A Command subclass that calls a std::function object.
 *
 * This function object is suitable to accept C++ lambda functions.
 *
 * \ingroup ITKSystemObjects
 * \ingroup ITKCommon
 */

class ITKCommon_EXPORT FunctionCommand : public Command
{
public:
  /** Standard class type aliases. */
  using Self = FunctionCommand;
  using Pointer = SmartPointer<Self>;

  using FunctionObjectType = std::function<void(const EventObject &)>;

  /** \see LightObject::GetNameOfClass() */
  itkOverrideGetNameOfClassMacro(FunctionCommand);

  /** Method for creation through the object factory. */
  itkNewMacro(Self);

  /** Set the C callback function pointer to be called at Execute time. */
  void
  SetCallback(FunctionObjectType f);

  /** Execute the callback function. */
  void
  Execute(Object *, const EventObject & event) override;

  /** Execute the callback function with a const Object */
  void
  Execute(const Object *, const EventObject & event) override;

protected:
  FunctionCommand();
  ~FunctionCommand() override;


  FunctionObjectType m_FunctionObject{};
};

} // end namespace itk

#endif
