/*
  TreeDiffMutatorBinding  -  implementation of diff application to opaque 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.cpp
 ** Implementation of diff application to unspecific private data structures.
 ** This binding is the link between a generic interpreter for our
 ** »tree diff language« and a concrete TreeMutator implementation,
 ** as provided by the target data structure. We do not require much
 ** additional knowledge regarding the opaque target structure, beyond
 ** the ability to construct such a customised TreeMutator. For this reason,
 ** the implementation is mostly generic and thus can be emitted here within
 ** the library module -- with the exception of the ctor, which indeed picks
 ** up some specifics of the concrete usage situation and thus needs to be
 ** generated in usage context.
 ** 
 ** @see tree-diff.cpp
 ** @see tree-diff-mutator-binding.cpp
 ** @see DiffVirtualisedApplication_test
 ** 
 */


#include "lib/error.hpp"
#include "lib/diff/tree-diff-mutator-binding.hpp"



namespace lib {
namespace diff{
  
  /* ======= Implementation of Tree Diff Application via TreeMutator ======= */
  
  using util::unConst;
  using util::cStr;
  using util::_Fmt;
  using std::move;
  using std::swap;
  
  
#if false /////////////////////////////////////////////////////////////////////////////////////////////////////////////UNIMPLEMENTED :: TICKET #992

  using Mutator = Rec::Mutator;
  using Content = Rec::ContentMutator;
  using Iter    = Content::Iter;
  
  template<>
  struct DiffApplicationStrategy<DiffMutable>::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
  DiffApplicationStrategy<DiffMutable>::__expect_in_target (GenNode const& elm, Literal oper)
  {
    if (endOfData())
      throw error::State(_Fmt("Unable to %s element %s from target as demanded; "
                              "no (further) elements in target sequence") % oper % elm
                        , LUMIERA_ERROR_DIFF_CONFLICT);
    
    if (elm.matches(Ref::CHILD) and not srcPos()->isNamed())
      return; // allow for anonymous pick or delete of children
    
    if (not srcPos()->matches(elm))
      throw error::State(_Fmt("Unable to %s element %s from target as demanded; "
                              "found element %s on current target position instead")
                              % oper % elm % *srcPos()
                        , LUMIERA_ERROR_DIFF_CONFLICT);
  }
  
  void
  DiffApplicationStrategy<DiffMutable>::__expect_further_elements (GenNode const& elm)
  {
    if (endOfData())
      throw error::State(_Fmt("Premature end of target sequence, still expecting element %s; "
                              "unable to apply diff further.") % elm
                        , LUMIERA_ERROR_DIFF_CONFLICT);
  }
  
  void
  DiffApplicationStrategy<DiffMutable>::__expect_found (GenNode const& elm, Iter const& targetPos)
  {
    if (targetPos == src().end())
      throw error::State(_Fmt("Premature end of sequence; unable to locate "
                              "element %s in the remainder of the target.") % elm
                        , LUMIERA_ERROR_DIFF_CONFLICT);
  }
  
  void
  DiffApplicationStrategy<DiffMutable>::__expect_successful_location (GenNode const& elm)
  {
    if (endOfData()
        and not (    elm.matches(Ref::END)                                      // after(_END_)     -> its OK we hit the end
                 or (elm.matches(Ref::ATTRIBS) and src().children.empty())))    // after(_ATTRIBS_) -> if there are no children, it's OK to hit the end
      throw error::State(_Fmt("Unable locate position 'after(%s)'") % elm.idi
                        , LUMIERA_ERROR_DIFF_CONFLICT);
  }
  
  void
  DiffApplicationStrategy<DiffMutable>::__expect_valid_parent_scope (GenNode::ID const& idi)
  {
    if (scopes_.empty())
      throw error::State(_Fmt("Unbalanced child scope bracketing tokens in diff; "
                              "When leaving scope %s, we fell out of root scope.") % idi.getSym()
                        , LUMIERA_ERROR_DIFF_CONFLICT);
    
    if (alteredRec().empty())
      throw error::State(_Fmt("Corrupted state. When leaving scope %s, "
                              "we found an empty parent scope.") % idi.getSym()
                        , LUMIERA_ERROR_DIFF_CONFLICT);
  }
  
  void
  DiffApplicationStrategy<DiffMutable>::__expect_end_of_scope (GenNode::ID const& idi)
  {
    if (not endOfData())
      throw error::State(_Fmt("Incomplete diff: when about to leave scope %s, "
                              "not all previously existing elements have been confirmed by the diff. "
                              "At least one spurious element %s was left over") % idi.getSym() % *srcPos()
                        , LUMIERA_ERROR_DIFF_CONFLICT);
  }
  
  
  Iter
  DiffApplicationStrategy<DiffMutable>::find_in_current_scope (GenNode const& elm)
  {
    Iter end_of_scope = src().currIsAttrib()? src().attribs.end()
                                            : src().children.end();
    return std::find_if (srcPos()
                        ,end_of_scope
                        ,[&](auto& entry)
                             {
                               return entry.matches(elm);
                             });
  }
  
  GenNode const&
  DiffApplicationStrategy<DiffMutable>::find_child (GenNode::ID const& idi)
  {
    if (alteredRec().empty())
      throw error::State(_Fmt("Attempt to mutate element %s, but current target data scope is empty. "
                              "Sender and receiver out of sync?") % idi.getSym()
                        , LUMIERA_ERROR_DIFF_CONFLICT);
    
    // Short-cut-mutation: look at the last element.
    // this should be the one just added. BUT NOTE: this fails
    // when adding an attribute after entering the child scope.
    // Since attributes are typically values and not mutated,
    // this inaccuracy was deemed acceptable
    auto& current = out().accessLast();
    if (Ref::THIS.matches(idi) or current.matches(idi))
      return current;
    
    for (auto & child : alteredRec())
      if (child.idi == idi)
        return child;
    
    throw error::State(_Fmt("Attempt to mutate non existing child record; unable to locate child %s "
                            "after applying the diff. Current scope: %s") % idi.getSym() % alteredRec()
                      , LUMIERA_ERROR_DIFF_CONFLICT);
  }
  
  void
  DiffApplicationStrategy<DiffMutable>::move_into_new_sequence (Iter pos)
  {
    if (src().currIsAttrib())
      out().appendAttrib (move(*pos));                    //////////////TICKET #969  was it a good idea to allow adding attributes "after the fact"?
    else
      out().appendChild (move(*pos));
  }
#endif    /////////////////////////////////////////////////////////////////////////////////////////////////////////////UNIMPLEMENTED :: TICKET #992
  
  /* == Forwarding: error handling == */
  
  void
  DiffApplicationStrategy<DiffMutable>::__expect_in_target  (GenNode const& elm, Literal oper)
  {
    
  }
  
  void
  DiffApplicationStrategy<DiffMutable>::__expect_further_elements (GenNode const& elm)
  {
    
  }
  
  void
  DiffApplicationStrategy<DiffMutable>::__fail_not_found (GenNode const& elm)
  {
    
  }
  
  void
  DiffApplicationStrategy<DiffMutable>::__expect_end_of_scope (GenNode::ID const& idi)
  {
    
  }
  
  void
  DiffApplicationStrategy<DiffMutable>::__expect_valid_parent_scope (GenNode::ID const& idi)
  {
    
  }
  
  
  /* == Forwarding: mutation primitives == */
  
  void
  DiffApplicationStrategy<DiffMutable>::skipSrc()
  {
    UNIMPLEMENTED("skip next src element and advance abstract source position");
  }
  
  void
  DiffApplicationStrategy<DiffMutable>::injectNew (GenNode const& n)
  {
    UNIMPLEMENTED("inject a new element at current abstract position");
  }
  
  bool
  DiffApplicationStrategy<DiffMutable>::matchSrc (GenNode const& n)
  {
    UNIMPLEMENTED("ensure the next source element matches with given spec");
  }
  
  bool
  DiffApplicationStrategy<DiffMutable>::acceptSrc (GenNode const& n)
  {
    UNIMPLEMENTED("accept existing element, when matching the given spec");
  }
  
  bool
  DiffApplicationStrategy<DiffMutable>::findSrc (GenNode const& n)
  {
    UNIMPLEMENTED("locate designated element and accept it at current position");
  }
  
  bool
  DiffApplicationStrategy<DiffMutable>::accept_until (GenNode const& refMark)
  {
    UNIMPLEMENTED("repeatedly accept until encountering the mark");
  }
  
  void
  DiffApplicationStrategy<DiffMutable>::assignElm (GenNode const& n)
  {
    UNIMPLEMENTED("locate already accepted element and assign given new payload");
  }
  
  void
  DiffApplicationStrategy<DiffMutable>::open_subScope (GenNode const& n)
  {
    UNIMPLEMENTED("locate already accepted element and open recursive sub-scope for mutation");
  }
  
  void
  DiffApplicationStrategy<DiffMutable>::close_subScope()
  {
    UNIMPLEMENTED("finish and leave sub scope and return to invoking parent scope");
  }
  
  
  
  /* == Implementation of the list diff application primitives == */
  
  void
  DiffApplicationStrategy<DiffMutable>::ins (GenNode const& n)
  {
    injectNew (n);
  }
  
  void
  DiffApplicationStrategy<DiffMutable>::del (GenNode const& n)
  {
    __expect_in_target(n, "remove");
    skipSrc();
  }
  
  void
  DiffApplicationStrategy<DiffMutable>::pick (GenNode const& n)
  {
    __expect_in_target(n, "pick");
    acceptSrc (n);
  }
  
  void
  DiffApplicationStrategy<DiffMutable>::skip (GenNode const& n)
  {
    __expect_further_elements (n);
    skipSrc();
  }      // assume the actual content has been moved away by a previous find()
  
  void
  DiffApplicationStrategy<DiffMutable>::find (GenNode const& n)
  {
    __expect_further_elements (n);
         // consume and leave waste, expected to be cleaned-up by skip() later
    if (not findSrc(n));
      __fail_not_found (n);
  }
  
  
  /* == Implementation of the tree diff application primitives == */
  
  /** cue to a position behind the named node,
   *  thereby picking (accepting) all traversed elements
   *  into the reshaped new data structure as-is */
  void
  DiffApplicationStrategy<DiffMutable>::after (GenNode const& n)
  {
    if (not accept_until(n))
      __fail_not_found (n);
  }
  
  /** assignment of changed value in one step */
  void
  DiffApplicationStrategy<DiffMutable>::set (GenNode const& n)
  {
    assignElm (n);
  }
  
  /** open nested scope to apply diff to child object */
  void
  DiffApplicationStrategy<DiffMutable>::mut (GenNode const& n)
  {
    open_subScope (n);
    
#if false /////////////////////////////////////////////////////////////////////////////////////////////////////////////UNIMPLEMENTED :: TICKET #992
    Rec const& childRecord = child.data.get<Rec>();
    TRACE (diff, "tree-diff: ENTER scope %s", cStr(childRecord));
#endif    /////////////////////////////////////////////////////////////////////////////////////////////////////////////UNIMPLEMENTED :: TICKET #992
  }
  
  /** finish and leave child object scope, return to parent */
  void
  DiffApplicationStrategy<DiffMutable>::emu (GenNode const& n)
  {
#if false /////////////////////////////////////////////////////////////////////////////////////////////////////////////UNIMPLEMENTED :: TICKET #992
    TRACE (diff, "tree-diff: LEAVE scope %s", cStr(describeScope()));
#endif    /////////////////////////////////////////////////////////////////////////////////////////////////////////////UNIMPLEMENTED :: TICKET #992
    
    __expect_end_of_scope (n.idi);
    close_subScope();
    __expect_valid_parent_scope (n.idi);
  }
  
  
  
  void
  DiffApplicationStrategy<DiffMutable>::initDiffApplication()
  {
    TODO("(re)initialise the diff application machinery");
#if false /////////////////////////////////////////////////////////////////////////////////////////////////////////////UNIMPLEMENTED :: TICKET #992
    REQUIRE (1 == scopes_.size());
    scopes_.top().init();
#endif    /////////////////////////////////////////////////////////////////////////////////////////////////////////////UNIMPLEMENTED :: TICKET #992
  }
  
  
  
  /* ==== trigger code generation of the generic part ==== */

  /************************************************************************/
  /* explicit template instantiation DiffApplicationStrategy<DiffMutable> */
  /************************************************************************/
  
  template class DiffApplicationStrategy<DiffMutable>;
  
  
  
}} // namespace lib::diff