command-impl-clone-builder.hpp

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/*
  COMMAND-IMPL-CLONE-BUILDER.hpp  -  Cloning command implementation without disclosing concrete type

  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_COMMAND_IMPL_CLONE_BUILDER_H
#define CONTROL_COMMAND_IMPL_CLONE_BUILDER_H

#include "steam/control/command-mutation.hpp"
#include "lib/typed-allocation-manager.hpp"
#include "lib/opaque-holder.hpp"
#include "lib/nocopy.hpp"


namespace steam {
namespace control {
  
  using lib::TypedAllocationManager;
  using lib::InPlaceBuffer;
  
  
  namespace impl { // Helper: type erased context for creating command clones
    
    struct CloneContext  
      {
        virtual ~CloneContext() {}
        
        virtual UndoMutation const& getUndoFunc() { NOTREACHED(); }
        virtual PClo         const& getClosure()  { NOTREACHED(); }
        virtual bool                isValid()     { return false; }
      };
    
    class ClonedContext
      : public CloneContext
      {
        PClo newClosure_;
        UndoMutation newUndoFunctor_;
        
        virtual UndoMutation const& getUndoFunc() { return newUndoFunctor_; }
        virtual PClo         const& getClosure()  { return newClosure_; }
        virtual bool                isValid()     { return true; }
        
        
        template<typename ARG>
        ARG&
        downcast()
          {
            REQUIRE (INSTANCEOF (ARG, newClosure_.get()));
            
            return static_cast<ARG&> (*newClosure_);
          }
        
        
      public:
        
        template<typename ARG>
        ClonedContext ( ARG const& origArgHolder
                      , TypedAllocationManager& allocator
                      )
          : newClosure_(allocator.create<ARG> (origArgHolder))
          , newUndoFunctor_(downcast<ARG>().getMementoWiring())
          { }
      };
    
  }//(End) impl namespace
  
  
  
  
  
  class CommandImplCloneBuilder
    : util::NonCopyable
    {
      typedef InPlaceBuffer<impl::CloneContext, sizeof(impl::ClonedContext)> ContextHolder;
      
      TypedAllocationManager& allocator_;
      ContextHolder newContext_;
      
    public:
      CommandImplCloneBuilder (TypedAllocationManager& allo)
        : allocator_(allo)
        { }
      
      
      template<typename ARG>
      void
      buildCloneContext (ARG const& origArgHolder)
        {
          REQUIRE (!newContext_->isValid(), "Lifecycle-Error");
          
          newContext_.create<impl::ClonedContext> (origArgHolder, allocator_);
        }
      
      
      
      UndoMutation const&
      clonedUndoMutation ()
        {
          REQUIRE (newContext_->isValid());
          return newContext_->getUndoFunc();
        }
      
      
      PClo const&
      clonedClosuere ()
        {
          REQUIRE (newContext_->isValid());
          return newContext_->getClosure();
        }
      
    };
  
  
  
  
  
}} // namespace steam::control
#endif