handling-pattern.hpp

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/*
  HANDLILNG-PATTERN.hpp  -  A skeleton for executing commands, including standard implementations

  Copyright (C)         Lumiera.org
    2009,               Hermann Vosseler <Ichthyostega@web.de>

  This program is free software; you can redistribute it and/or
  modify it under the terms of the GNU General Public License as
  published by the Free Software Foundation; either version 2 of
  the License, or (at your option) any later version.

  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this program; if not, write to the Free Software
  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

*/


#ifndef CONTROL_HANDLING_PATTERN_H
#define CONTROL_HANDLING_PATTERN_H

#include "lib/error.hpp"
#include "lib/symbol.hpp"

#include <string>



namespace steam {
namespace control {
  
  using std::string;
  using lib::Symbol;
  
  
  class CommandImpl;
  
  
  class ExecResult
    {
      const string log_;
      
    public:
      bool isValid() const;
      void maybeThrow() const;
      operator bool() const { return isValid(); }
      
    protected:
      ExecResult () { }                   
      ExecResult (lumiera::Error const&); 
      
      friend class HandlingPattern;
    };
  
  
  
  class HandlingPattern
    {
    public:
      virtual ~HandlingPattern() {}   
      
      enum ID
        { SYNC
        , SYNC_THROW
        , ASYNC
        , DUMMY
        
        , NUM_IDS
        };
      
      static ID defaultID() { return DUMMY; }   
      
      static HandlingPattern const& get (ID id);
      
      
      
      ExecResult exec (CommandImpl& command, string)  const;
      
      ExecResult undo (CommandImpl& command, string)  const;
      
      explicit operator bool()  const { return isValid(); }
      virtual bool isValid()    const                         =0;
      
    protected:
      
      virtual void performExec (CommandImpl& command)  const  =0;
      virtual void performUndo (CommandImpl& command)  const  =0;
      
    private:
      typedef void (HandlingPattern::*Action) (CommandImpl&) const;
      
      ExecResult invoke (CommandImpl&, string id, Action)  const;
    };
  
  
  
  inline ExecResult
  HandlingPattern::exec (CommandImpl& command, string id)  const
  {
    return this->invoke (command, id, &HandlingPattern::performExec);
  }
  
  inline ExecResult
  HandlingPattern::undo (CommandImpl& command, string id)  const
  {
    return this->invoke (command, id, &HandlingPattern::performUndo);
  }
  
  
  
  
}} // namespace steam::control
#endif