/*
 * 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>

#include <boost/preprocessor/list/adt.hpp>

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

// forward declaration

namespace MoleCuilder {
  class ActionState;
  class ActionSequence;
}
class Dialog;

#include "Actions/ActionTrait.hpp"


namespace MoleCuilder {

/** Actions are Command patterns to allow for undoing and redoing.
 *
 * Each specific Action derives from this class to implement a certain functionality.
 *
 * Actions describe something that has to be done.
 * Actions can be passed around, stored, performed and undone (Command-Pattern:
 * http://en.wikipedia.org/wiki/Command_pattern).
 *
 * Unique to each Action is its ActionTrait, i.e. the options it requires
 * to perform a certain function. E.g. in order to execute a "add atom" Action
 * we need to know a position and an element. These options have certain
 * properties, see \ref OptionTrait and \ref ActionTrait wherein these are stored.
 * Essentially, each option is stored as an \ref OptionTrait instance and
 * contains the token, default value, a description, the type, ...
 *
 * ActionTrait itself is also an OptionTrait because the command token may actually
 * coincide with an option-token. E.g. this allows "...--add-atom 3" to mean
 * both execute the action under token "add-atom" and that the option "add-atom"
 * (the new atom's \ref element number) should contain 3.
 *
 * \ref ActionTrait contains a map of all associated options. With this in the cstor
 * we register not only the Action with the \ref ActionRegistry but also each of
 * its \link options OptionTrait \endlink with the \ref OptionRegistry.
 *
 * The token of the option is unique, but two Action's may share the same token if:
 * -# they have the same default value
 * -# they have the same type
 *
 * This requirement is easy because if you need to store some option of another
 * type, simply think of a new suitable name for it.
 *
 * The actual value, i.e. "3" in the "add-atom" example, is taken from the
 * ValueStorage, see \ref Dialog for how this is possible.
 *
 * \note There is a unit test that checks on the consistency of all registered
 * options, also in "--enable-debug"-mode assertions will check that an option
 * has not been registered before under another type.
 *
 */
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 ActionTrait &_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 ActionTrait. Information should be
   * encapsulated in the Action, no more references to the outside than absolutely
   * necessary.
   */
  const ActionTrait Traits;

protected:
  /** 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();

  /** Creates the static entities Action::success and Action::failure.
   * This is only to be called by ActionHistory.
   */
  static void createStaticStateEntities();

  /**
   * 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 History, 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 successful
   * without providing a special state. Use this if your Action does not need
   * a specialized state.
   */
  static state_ptr success;

  /**
   * This special state can be returned, to indicate that the action could not do it's
   * work, was aborted 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();

  /** Virtual function that starts the timer.
   *
   */
  virtual void startTimer() const {};

  /** Virtual function that ends the timer.
   *
   */
  virtual void endTimer() const {};

private:

  /**
   * 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 appropriate 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_ */