source: src/Actions/Action.hpp@ bc3411

/*
 * Action.hpp
 *
 *  Created on: Dec 8, 2009
 *      Author: crueger
 */

#ifndef ACTION_HPP_
#define ACTION_HPP_

// include config.h
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <string>
#include <boost/shared_ptr.hpp>

/** Used in .def files in paramdefaults define to set that no default value exists.
 * We define NODEFAULT here, as it is used in .def files and needs to be present
 * before these are included.
 */
#define NODEFAULT ""

// forward declaration

class ActionState;
class ActionSequence;
class Dialog;

#include "Actions/ActionTraits.hpp"



/**
 * Base class for all actions.
 *
 * Actions describe something that has to be done.
 * Actions can be passed around, stored, performed and undone (Command-Pattern).
 */
class Action
{
friend class ActionSequence;
friend class ActionHistory;
public:

  enum QueryOptions {Interactive, NonInteractive};

  /**
   * This type is used to store pointers to ActionStates while allowing multiple ownership
   */
  typedef boost::shared_ptr<ActionState> state_ptr;

  /**
   * Standard constructor of Action Base class
   *
   * All Actions need to have a name. The second flag indicates, whether the action should
   * be registered with the ActionRegistry. If the Action is registered the name of the
   * Action needs to be unique for all Actions that are registered.
   *
   * \note NO reference for \a _Traits as we do have to copy it, otherwise _Traits would have
   * to be present throughout the program's run.
   *
   * \param Traits information class to this action
   * \param _doRegister whether to register with ActionRegistry
   */
  Action(const ActionTraits &_Traits, bool _doRegister=true);
  virtual ~Action();

  /**
   * This method is used to call an action. The basic operations for the Action
   * are carried out and if necessary/possible the Action is added to the History
   * to allow for undo of this action.
   *
   * If the call needs to undone you have to use the History, to avoid destroying
   * invariants used by the History.
   *
   * Note that this call can be Interactive (i.e. a dialog will ask the user for
   * necessary information) and NonInteractive (i.e. the information will have to
   * be present already within the ValueStorage class or else a MissingArgumentException
   * is thrown)
   */
  void call(enum QueryOptions state = Interactive);

  /**
   * This method provides a flag that indicates if an undo mechanism is implemented
   * for this Action. If this is true, and this action was called last, you can
   * use the History to undo this action.
   */
  virtual bool canUndo()=0;

  /**
   * This method provides a flag, that indicates if the Action changes the state of
   * the application in a way that needs to be undone for the History to work.
   *
   * If this is false the Action will not be added to the History upon calling. However
   * Actions called before this one will still be available for undo.
   */
  virtual bool shouldUndo()=0;

  /**
   * Indicates whether the Action can do it's work at the moment. If this
   * is false calling the action will result in a no-op.
   */
  virtual bool isActive();

  /**
   * Returns the name of the Action.
   */
  const std::string getName() const;

  /**
   * returns a detailed help message.
   */
  const std::string help() const;

  /**
   * Traits resemble all necessary information that "surrounds" an action, such as
   * its name (for ActionRegistry and as ref from string to instance and vice versa),
   * which menu, which position, what parameters, their types, if it is itself a
   * parameter and so on ...
   *
   * Note that is important that we do not use a reference here. We want to copy the
   * information in the Action's constructor and have it contained herein. Hence, we
   * also have our own copy constructor for ActionTraits. Information should be
   * encapsulated in the Action, no more references to the outside than absolutely
   * necessary.
   */
  const ActionTraits Traits;

  /** Removes the static entities Action::success and Action::failure.
   * This is only to be called on the program's exit, i.e. in cleanUp(),
   * as these static entities are used throughout all Actions.
   */
  static void removeStaticStateEntities();

protected:
  /**
   * This method is called by the History, when an undo is performed. It is
   * provided with the corresponding state produced by the performCall or
   * performRedo method and needs to provide a state that can be used for redo.
   */
  state_ptr undo(state_ptr);

  /**
   * This method is called by the Histor, when a redo is performed. It is
   * provided with the corresponding state produced by the undo method and
   * needs to produce a State that can then be used for another undo.
   */
  state_ptr redo(state_ptr);

  /**
   * This special state can be used to indicate that the Action was successfull
   * without providing a special state. Use this if your Action does not need
   * a speciallized state.
   */
  static state_ptr success;

  /**
   * This special state can be returned, to indicate that the action could not do it's
   * work, was abborted by the user etc. If you return this state make sure to transactionize
   * your Actions and unroll the complete transaction before this is returned.
   */
  static state_ptr failure;

  /**
   * This creates the dialog requesting the information needed for this action from the user
   * via means of the user interface.
   */
  Dialog * createDialog();

private:

  /**
   * This is called internally before the Action::performCall(). It initializes the
   * necessary ActionParameters by retrieving the values from ValueStorage.
   */
  virtual void getParametersfromValueStorage()=0;

  /**
   * This is called internally before the action is processed. This adds necessary queries
   * to a given dialog to obtain parameters for the user for processing the action accordingly.
   * The dialog will be given to the user before Action::performCall() is initiated, values
   * are transfered via ValueStorage.
   */
  virtual Dialog * fillDialog(Dialog*)=0;

  /**
   * This is called internally when the call is being done. Implement this method to do the actual
   * work of the Action. Implement this in your Derived classes. Needs to return a state that can be
   * used to undo the action.
   */
  virtual state_ptr performCall()=0;

  /**
   * This is called internally when the undo process is chosen. This Method should use the state
   * produced by the performCall method to return the state of the application to the state
   * it had before the Action.
   */
  virtual state_ptr performUndo(state_ptr)=0;

  /**
   * This is called internally when the redo process is chosen. This method shoudl use the state
   * produced by the performUndo method to return the application to the state it should have after
   * the action.
   *
   * Often this method can be implement to re-use the performCall method. However if user interaction
   * or further parameters are needed, those should be taken from the state and not query the user
   * again.
   */
  virtual state_ptr performRedo(state_ptr)=0;
};

/**
 * This class can be used by actions to save the state.
 *
 * It is implementing a memento pattern. The base class is completely empty,
 * since no general state internals can be given. The Action performing
 * the Undo should downcast to the apropriate type.
 */
class ActionState{
public:
  ActionState(){}
  virtual ~ActionState(){}
};

/**
 * This class can be used by actions to contain parameters.
 *
 * The base class is completely empty, since no general parameters can be given. The
 * Action performing the function should construct its own parameter class derived
 * from it.
 */
class ActionParameters{
public:
  ActionParameters(){}
  virtual ~ActionParameters(){}
};

#endif /* ACTION_HPP_ */