command-impl-clone-builder.hpp

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

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

  **Lumiera** 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. See the file COPYING for further details.

*/


#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