lumiera_/src/lib/diff/tree-diff-mutator-binding.hpp

/*
  TREE-DIFF-MUTATOR-BINDING.hpp  -  consume a tree diff, but target arbitrary private data

  Copyright (C)         Lumiera.org
    2016,               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.

*/


/** @file tree-diff-mutator-binding.hpp
 ** Concrete implementation to apply structural changes to unspecific
 ** private data structures with hierarchical nature. This is a variation
 ** of the generic [tree diff applicator](\ref tree-diff-application.hpp),
 ** using the same implementation concept, while relying on an abstract
 ** adapter type, the \ref TreeMutator. Similar to the generic case, when
 ** combined with the generic #DiffApplicator, this allows to receive
 ** linearised structural diff descriptions and apply them to a given
 ** target data structure, which in this case is even a decoupled
 ** private data structure.
 ** 
 ** ## Design considerations
 ** So this use case is implemented on the same conceptual framework used for
 ** the generic tree diff application, which in turn is -- conceptually -- an
 ** extension of applying a list diff. But, again, we follow the route _not_ to
 ** explicate those conceptual relations in the form of inheritance. This would
 ** be implementation re-use, as opposed to building a new viable abstraction.
 ** No one outside the implementation realm would benefit from such an abstraction,
 ** so we prefer to understand the tree diff language as the abstraction, which
 ** needs to embodied into two distinct contexts of implementation.
 ** 
 ** ### Yet another indirection
 ** Unfortunately this leads to yet another indirection layer: Implementing a
 ** language in itself is necessarily a double dispatch (we have to abstract the
 ** verbs and we have to abstract the implementation side). And now we're decoupling
 ** the implementation side from a concrete data structure. Which means, that the
 ** use will have to provide a set of closures (which might even partially be generated
 ** functors) to translate the _implementation actions_ underlying the language into
 ** _concrete actions_ working on local data.
 ** 
 ** ### Generic and variable parts
 ** So this is a link between generic [»tree diff language«](\ref tree-diff.hpp)
 ** interpretation and the concrete yet undisclosed private data structure, and
 ** most of this implementation is entirely generic, since the specifics are
 ** abstracted away behind the TreeMutator interface. For this reason, most of
 ** this explicit template specialisation code, especially. the virtual functions,
 ** can be emitted right here, within the library module. This helps to reduce
 ** "template bloat" and simplifies the dynamic linking. Thus, this header
 ** only contains the definition and the ctor code, which indeed needs to
 ** be adapted to each usage situation, while the main body of the
 ** functionality has been moved to the corresponding implementation
 ** file, where this template is explicitly instantiated, to force
 ** code generation into the library module.
 ** 
 ** @todo this is WIP as of 2/2016 -- in the end it might be merged back or even
 **       replace the tree-diff-application.hpp
 ** 
 ** @see DiffVirtualisedApplication_test
 ** @see DiffTreeApplication_test
 ** @see DiffListApplication_test
 ** @see GenNodeBasic_test
 ** @see tree-diff.hpp
 ** 
 */


#ifndef LIB_DIFF_TREE_DIFF_MUTATOR_BINDING_H
#define LIB_DIFF_TREE_DIFF_MUTATOR_BINDING_H


#include "lib/diff/tree-diff.hpp"
#include "lib/diff/tree-mutator.hpp"
#include "lib/diff/diff-mutable.hpp"
#include "lib/diff/gen-node.hpp"
#include "lib/format-string.hpp"
#include "lib/util.hpp"

#include <utility>
#include <stack>

namespace lib {
namespace diff{
  
  /* ======= derive a TreeMutator binding for a given opaque data structure ======= */
  
  
  using meta::enable_if;
  using meta::Yes_t;
  using meta::No_t;
  using std::is_same;
  
  /**
   * helper to detect presence of a
   * TreeMutator builder function
   */
  template<typename T>
  class exposes_MutatorBuilder
    {
      
      META_DETECT_FUNCTION (void, buildMutator, (TreeMutator::Handle));
      
    public:
      enum{ value = HasFunSig_buildMutator<T>::value
          };
    };
  
  
  
  
  
  template<class TAR, typename SEL =void>
  struct MutatorBinding
    {
      static_assert (!sizeof(TAR), "MutatorBinding: Unable to access or build a TreeMutator for this target data.");
    };
  
  template<class TAR>
  struct MutatorBinding<TAR, enable_if<is_same<TAR, DiffMutable>>>
    {
      using Ret = DiffMutable&;
    };
  
  template<class TAR>
  struct MutatorBinding<TAR, enable_if<exposes_MutatorBuilder<TAR>>>
    {
      class Wrapper
        : public DiffMutable
        {
          TAR& subject_;
          
          /** implement the TreeMutator interface,
           *  by forwarding to a known implementation function
           *  on the wrapped target data type */
          virtual void
          buildMutator (TreeMutator::Handle handle)
            {
              subject_.buildMutator (handle);
            }
          
        public:
          Wrapper(TAR& subj)
            : subject_(subj)
            { }
        };
      
      using Ret = Wrapper;
    };
  
  template<class TAR>
  auto
  mutatorBinding (TAR& subject) -> typename MutatorBinding<TAR>::Ret
  {
     using Wrapper = typename MutatorBinding<TAR>::Ret;
     return Wrapper{subject};
  }
  
  
  
  
  /* ======= Implementation of Tree Diff Application via TreeMutator ======= */
  
  using util::unConst;
  using util::cStr;
  using util::_Fmt;
  using std::move;
  using std::swap;
  
  
  /**
   * Interpreter for the tree-diff-language to work on arbitrary, undisclosed
   * local data structures. The key point to note is that this local data is
   * not required to implement any specific interface. The only requirement is
   * the ability somehow to support the basic operations of applying a structural
   * diff. This is ensured with the help of a _customisable adapter_ the TreeMutator.
   * @throws  lumiera::error::State when diff application fails structurally.
   * @throws  _unspecified errors_ when delegated operations fail.
   * @see TreeDiffInterpreter explanation of the verbs
   * @see DiffVirtualisedApplication_test demonstration of usage
   */
  template<>
  class DiffApplicationStrategy<DiffMutable>
    : public TreeDiffInterpreter
    {
#if false /////////////////////////////////////////////////////////////////////////////////////////////////////////////UNIMPLEMENTED :: TICKET #992
      using Mutator = Rec::Mutator;
      using Content = Rec::ContentMutator;
      using Iter    = Content::Iter;
      
      struct ScopeFrame
        {
          Mutator& target;
          Content content;
          
          ScopeFrame(Mutator& toModify)
            : target(toModify)
            , content()
            { }
          
          void init()
            {
              target.swapContent (content);
              content.resetPos();
            }
        };
      
      /** Storage: a stack of workspaces
       * used to handle nested child objects */
      std::stack<ScopeFrame> scopes_;
      
      
      Mutator& out() { return scopes_.top().target; }
      Content& src() { return scopes_.top().content; }
      Iter& srcPos() { return scopes_.top().content.pos; }
      bool endOfData() { return srcPos() == src().end(); }   /////TODO split into an actual scope end check and an non-null check
      Rec& alteredRec() { return out(); }
      
      
      void __expect_in_target (GenNode const& elm, Literal oper);
      void __expect_further_elements (GenNode const& elm);
      void __expect_found (GenNode const& elm, Iter const& targetPos);
      void __expect_successful_location (GenNode const& elm);
      void __expect_valid_parent_scope (GenNode::ID const& idi);
      void __expect_end_of_scope (GenNode::ID const& idi);
      
      
      Iter find_in_current_scope (GenNode const& elm);
      
      GenNode const& find_child (GenNode::ID const& idi);
      
      void move_into_new_sequence (Iter pos);
#endif    /////////////////////////////////////////////////////////////////////////////////////////////////////////////UNIMPLEMENTED :: TICKET #992
      
      /* == Forwarding: error handling == */
      
      void __expect_in_target  (GenNode const& elm, Literal oper);
      void __expect_further_elements (GenNode const& elm);
      void __fail_not_found (GenNode const& elm);
      void __expect_end_of_scope (GenNode::ID const& idi);
      void __expect_valid_parent_scope (GenNode::ID const& idi);
      
      
      
      /* == Forwarding: mutation primitives == */
      
      void skipSrc();
      void injectNew (GenNode const& n);
      bool matchSrc (GenNode const& n);
      bool acceptSrc (GenNode const& n);
      bool findSrc (GenNode const& n);
      bool accept_until (GenNode const& refMark);
      void assignElm (GenNode const& n);
      void open_subScope (GenNode const& n);
      void close_subScope();
      
      
      
      /* == Implementation of the list diff application primitives == */
      
      virtual void ins  (GenNode const& n) override;
      virtual void del  (GenNode const& n) override;
      virtual void pick (GenNode const& n) override;
      virtual void skip (GenNode const& n) override;
      virtual void find (GenNode const& n) override;
      
      
      /* == Implementation of the tree diff application primitives == */
      
      virtual void after(GenNode const& n) override;
      virtual void set  (GenNode const& n) override;
      virtual void mut  (GenNode const& n) override;
      virtual void emu  (GenNode const& n) override;
      
      
    public:
      explicit
      DiffApplicationStrategy(DiffMutable& targetBinding)
        {
          TODO("attach to the given Target");
#if false /////////////////////////////////////////////////////////////////////////////////////////////////////////////UNIMPLEMENTED :: TICKET #992
          scopes_.emplace(mutableTargetRecord);
#endif    /////////////////////////////////////////////////////////////////////////////////////////////////////////////UNIMPLEMENTED :: TICKET #992
        }
      
      void initDiffApplication();
    };
  
  
  
  /** use the explicit instantiation provided in library module */
  extern template class DiffApplicationStrategy<DiffMutable>;
  
  
}} // namespace lib::diff
#endif /*LIB_DIFF_TREE_DIFF_MUTATOR_BINDING_H*/