/****************************************************************************
 * Copyright (C) 2009-2015 EPAM Systems
 * 
 * This file is part of Indigo toolkit.
 * 
 * This file may be distributed and/or modified under the terms of the
 * GNU General Public License version 3 as published by the Free Software
 * Foundation and appearing in the file LICENSE.GPL included in the
 * packaging of this file.
 * 
 * This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
 * WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 ***************************************************************************/

#include "graph/embedding_enumerator.h"
#include "molecule/molecule.h"
#include "molecule/molecule_arom.h"
#include "molecule/molecule_arom_match.h"
#include "molecule/molecule_tautomer.h"
#include "molecule/molecule_tautomer_utils.h"
#include "molecule/molecule_substructure_matcher.h"
#include "molecule/molecule_exact_matcher.h"

using namespace indigo;

enum
{
   BOND_ZEROED = 0  // Bond can appear during tautomerism
};

TautomerChainFinder::TautomerChainFinder (TautomerSearchContext &context, int h_difference,
   int start_path_number, int n_chains) :
_context(context),
_path_length(0),
_h_difference(h_difference),
_is_zero_bond_present(!context.ring_chain),
_path_number(start_path_number + 2),
_n_chains(n_chains)
{
}

TautomerChainFinder::TautomerChainFinder (TautomerChainFinder &other) :
_context(other._context),
_path_length(other._path_length + 1),
_h_difference(other._h_difference * -1),
_path_number(other._path_number),
_start_idx1(other._start_idx1),
_start_idx2(other._start_idx2),
_n_chains(other._n_chains)
{
}

TautomerChainFinder::~TautomerChainFinder ()
{
}

bool TautomerChainFinder::enumeratePaths ()
{
   int n1, n2, e1 = -1, e2 = -1;

   while (nextPair(n1, n2, e1, e2, e1, e2))
   {
      int rc;
      bool zero_bond;
      int arom_bond2, bond_type2;

      if ((rc = isFeasiblePair(n1, n2, zero_bond, arom_bond2, bond_type2)) == 1)
      {
         TautomerChainFinder pe(*this);

         pe.addPair(n1, n2, zero_bond, arom_bond2, bond_type2);

         if (!pe.enumeratePaths())
            return false;

         pe.restore();
      } else if (rc == -1) {
         TautomerMatcher tm_state(_context, _path_number, _n_chains);

         tm_state.addPair(n1, n2, arom_bond2, bond_type2);

         if (!tm_state.findMatch())
            return false;

         tm_state.restore();
      }
   }
   return true;
}

bool TautomerChainFinder::nextPair (int &n1, int &n2, int &e1, int &e2, int prev_e1, int prev_e2)
{
   const Vertex &vertex1 = _context.g1.getVertex(_prev_n1);
   const Vertex &vertex2 = _context.g2.getVertex(_prev_n2);

   if (_is_zero_bond_present)
   {
      if (prev_e1 == -1)
         e1 = vertex1.neiBegin();

      if (prev_e2 == -1)
         e2 = vertex2.neiBegin();
      else
         e2 = vertex2.neiNext(prev_e2);

      for (; e1 != vertex1.neiEnd(); e1 = vertex1.neiNext(e1))
      {
         n1 = vertex1.neiVertex(e1);

         if (_context.core_1[n1] != EmbeddingEnumerator::UNMAPPED)
            continue;

         for (; e2 != vertex2.neiEnd(); e2 = vertex2.neiNext(e2))
         {
            n2 = vertex2.neiVertex(e2);

            if (_context.core_2[n2] != EmbeddingEnumerator::UNMAPPED)
               continue;

            if (TautomerMatcher::matchAtomsTau(_context.g1, _context.g2, n1, n2))
               return true;
         }

         e2 = vertex2.neiBegin();
      }
   } else if (_h_difference == 1) {
      if (prev_e1 == -1)
         e1 = _context.g1.vertexBegin();

      if (prev_e2 == -1)
         e2 = vertex2.neiBegin();
      else
         e2 = vertex2.neiNext(prev_e2);

      for (; e1 < _context.g1.vertexEnd(); e1 = _context.g1.vertexNext(e1))
      {
         n1 = e1;

         if (_context.core_1[n1] != EmbeddingEnumerator::UNMAPPED)
            continue;

         for (; e2 != vertex2.neiEnd(); e2 = vertex2.neiNext(e2))
         {
            n2 = vertex2.neiVertex(e2);

            if (_context.core_2[n2] != EmbeddingEnumerator::UNMAPPED)
               continue;

            if (TautomerMatcher::matchAtomsTau(_context.g1, _context.g2, n1, n2))
               return true;
         }

         e2 = vertex2.neiBegin();
      }
   } else {
      if (prev_e1 == -1)
         e1 = vertex1.neiBegin();

      if (prev_e2 == -1)
         e2 = _context.g2.vertexBegin();
      else
         e2 = _context.g2.vertexNext(prev_e2);

      for (; e1 != vertex1.neiEnd(); e1 = vertex1.neiNext(e1))
      {
         n1 = vertex1.neiVertex(e1);

         if (_context.core_1[n1] != EmbeddingEnumerator::UNMAPPED)
            continue;

         for (; e2 < _context.g2.vertexEnd(); e2 = _context.g2.vertexNext(e2))
         {
            n2 = e2;

            if (_context.core_2[n2] != EmbeddingEnumerator::UNMAPPED)
               continue;

            if (TautomerMatcher::matchAtomsTau(_context.g1, _context.g2, n1, n2))
               return true;
         }

         e2 = _context.g2.vertexBegin();
      }
   }

   return false;
}

int TautomerChainFinder::isFeasiblePair (int n1, int n2, bool &zero_bond, int &arom_bond_idx2, int &bond_type2)
{
   if (_prev_n1 != -1 && _context.decomposer1.getComponent(_prev_n1) != _context.decomposer1.getComponent(n1))
      return 0;
   if (_prev_n2 != -1 && _context.decomposer2.getComponent(_prev_n2) != _context.decomposer2.getComponent(n2))
      return 0;

   int edge1 = _context.g1.findEdgeIndex(_prev_n1, n1);
   int edge2 = _context.g2.findEdgeIndex(_prev_n2, n2);

   int type1 = 0;
   int type2 = 0;

   zero_bond = _is_zero_bond_present;
   arom_bond_idx2 = -1;

   if (edge1 == -1)
   {
      zero_bond = true;
   } else
      type1 = _context.g1.getBondOrder(edge1);

   if (type1 == BOND_AROMATIC || type1 == BOND_TRIPLE)
      return 0;

   if (edge2 == -1)
   {
      zero_bond = true;
   } else if (_context.g2.getBondOrder(edge2) == -1 &&
              _context.g2.possibleBondOrder(edge2, BOND_SINGLE))
   {
      if (_is_zero_bond_present || type1 == 0)
         return 0;

      zero_bond = true;
   } else
      type2 = _context.g2.getBondOrder(edge2);

   if (type2 == BOND_TRIPLE)
      return 0;

   if (type2 == BOND_AROMATIC)
      arom_bond_idx2 = edge2;

   if (edge1 == -1 && type2 == BOND_AROMATIC)
   {
      if (!_context.dearomatizationMatcher->isAbleToFixBond(edge2, 1))
         return 0;

      bond_type2 = 1;
   }

   if (type2 != BOND_AROMATIC) // both non-aromatic
   {
      if (type1 + _h_difference != type2)
         return 0;
   } else // exactly one aromatic
   {
      bond_type2 = type1 + _h_difference;

      if (bond_type2 < 1 || bond_type2 > 2)
         return 0;

      if (!_context.dearomatizationMatcher->isAbleToFixBond(edge2, bond_type2))
         return 0;
   }

   int h_count_1 = _context.g1.getAtomTotalH(n1);
   int h_count_2 = _context.g2.getAtomTotalH(n2);

   if (!_context.force_hydrogens)
   {
      h_count_1 += _context.h_rep_count_1[n1];
      h_count_2 += _context.h_rep_count_2[n2];
   }

   if (h_count_1 == h_count_2)
      return (_context.g1.possibleAtomCharge(n1, _context.g2.getAtomCharge(n2)) ? 1 : 0);
   if ((_path_length & 1) && h_count_1 - _h_difference ==  h_count_2)
   {
      if (_context.cb_check_rules == 0 || _context.cb_check_rules(_context, _start_idx1, _start_idx2, n1, n2))
         return -1;
   } 

   return 0;
}

void TautomerChainFinder::addPair (int n1, int n2, bool is_zero_bond, int arom_bond_idx2, int bond_type2)
{
   _context.core_1[n1] = n2;
   _context.core_2[n2] = n1;

   _context.chains_2[n2] = _path_number;

   _path_number++;

   _prev_n1 = n1;
   _prev_n2 = n2;

   _is_zero_bond_present = is_zero_bond;

   if (_path_length == 0)
   {
      _start_idx1 = n1;
      _start_idx2 = n2;
   }

#ifdef TRACE_TAUTOMER_MATCHING
   for (int i = 0; i < _path_number; i++)
      printf("  ");
   printf("%2d\n", n1 + 1);
   for (int i = 0; i < _path_number; i++)
      printf("  ");
   printf("%2d\n", n2 + 1);
#endif

   _bond_idx2 = arom_bond_idx2;

   if (_bond_idx2 >= 0)
      _context.dearomatizationMatcher->fixBond(_bond_idx2, bond_type2);
}

void TautomerChainFinder::restore ()
{
   _context.core_1[_prev_n1] = EmbeddingEnumerator::UNMAPPED;
   _context.core_2[_prev_n2] = EmbeddingEnumerator::UNMAPPED;

   _context.chains_2[_prev_n2] = 0;

   if (_bond_idx2 >= 0)
      _context.dearomatizationMatcher->unfixBond(_bond_idx2);
}

IMPL_ERROR(TautomerChainChecker, "tautomer chain checker");

TautomerChainChecker::TautomerChainChecker (TautomerSearchContext &context,
                                            const Array<int> &core1, const Array<int> &core2,
                                            int start_path_number) :
_context(context),
_path_length(0),
_h_difference(0),
_is_zero_bond_present(!context.ring_chain),
_is_query_bond_present(false),
_is_non_aromatic_bond_present(false),
_path_number(start_path_number + 2),
_core_1(core1),
_core_2(core2),
_tau_bonds_to_match(0),
_prev_n1(-1),
_prev_n2(-1),
_bond_idx1(-1),
_bond_idx2(-1),
_bond_type2(0)
{
   // calculate tautomer bonds
   for (int i = _context.g1.edgeBegin(); i < _context.g1.edgeEnd(); i = _context.g1.edgeNext(i))
   {
      int bond_1 = _context.g1.getBondOrder(i);

      if (bond_1 == -1)
         continue;

      const Edge& edge_1 = _context.g1.getEdge(i);

      int beg = _core_1[edge_1.beg];
      int end = _core_1[edge_1.end];

      if (beg < 0 || end < 0)
         continue;

      if (_context.chains_2[beg] > 0 && _context.chains_2[end] > 0)
         continue;

      const Vertex& vert_2_beg = _context.g2.getVertex(beg);

      int edge_2_idx = vert_2_beg.neiEdge(vert_2_beg.findNeiVertex(end));

      int bond_2 = _context.g2.getBondOrder(edge_2_idx);

      if (bond_1 != bond_2 && bond_1 != BOND_AROMATIC && bond_2 != BOND_AROMATIC)
         _tau_bonds_to_match++;
   }

   _context.core_1.copy(_core_1.ptr(), _context.initial_g1_vertexend);
              // see the comment in TautomerMatcher::_preliminaryEmbedding
   _context.core_2.copy(_core_2.ptr(), _context.g2.vertexEnd());
}

TautomerChainChecker::TautomerChainChecker (TautomerChainChecker &other) :
_context(other._context),
_path_length(other._path_length),
_h_difference(other._h_difference * -1),
_is_zero_bond_present(other._is_zero_bond_present),
_is_query_bond_present(other._is_query_bond_present),
_is_non_aromatic_bond_present(other._is_non_aromatic_bond_present),
_path_number(other._path_number),
_core_1(other._core_1),
_core_2(other._core_2),
_tau_bonds_to_match(other._tau_bonds_to_match),
_prev_n1(-1),
_prev_n2(-1),
_bond_idx1(-1),
_bond_idx2(-1),
_bond_type2(0),
_start_idx1(other._start_idx1),
_start_idx2(other._start_idx2)
{
}

TautomerChainChecker::~TautomerChainChecker ()
{
}

bool TautomerChainChecker::check ()
{
   int n1 = -1, n2 = -1;

   if (!_checkInterPathBonds())
      return true;

   if (_tau_bonds_to_match == 0 && _path_length == 0 && _matchAromatizedQuery())
   {
      _context.core_1.clear_resize(_context.g1.vertexEnd());
      _context.core_2.clear_resize(_context.g2.vertexEnd());

      memcpy(_context.core_1.ptr(), _core_1.ptr(), sizeof(int) * _context.g1.vertexEnd());
      memcpy(_context.core_2.ptr(), _core_2.ptr(), sizeof(int) * _context.g2.vertexEnd());

      return false;
   }

   if (_path_length == 0)
   {
      int diff;

      while (nextStartingPair(n1, n2))
         if (isFeasibleStartingPair(n1, n2, diff))
         {
            TautomerChainChecker cc(*this);

            cc._path_number++;
            cc.addPair(n1, n2);
            cc._path_length++;
            cc._h_difference = -diff;

            if (!cc.check())
               return false;

            cc.restore();
         }
   } else
   {
      int e1 = -1, e2 = -1;
      int rc;

      while (nextPair(n1, n2, e1, e2))
      {
         TautomerChainChecker cc1(*this);
         TautomerChainChecker cc2(*this);

         rc = isFeasiblePair(n1, n2, cc1, cc2);

         if (rc & 1) // intermediate pair in chain
         {
            cc1.addPair(n1, n2);

            if (!cc1.check())
               return false;

            cc1.restore();
         }
         if (rc & 2) // last pair in chain
         {
            cc2.addPair(n1, n2);

            if (cc2.releaseChain())
               if (!cc2.check())
                  return false;

            cc2.restoreChain();
            cc2.restore();
         }
      }
   }

   return true;
}

bool TautomerChainChecker::nextStartingPair (int &n1, int &n2)
{
   if (n2 == -1)
      n2 = _context.g2.vertexBegin();
   else
      n2 = _context.g2.vertexNext(n2);

   //n1 = _core_2[n2];

   for ( ; n2 < _context.g2.vertexEnd(); n2 = _context.g2.vertexNext(n2))
   {
      n1 = _core_2[n2];

      if (n1 != EmbeddingEnumerator::IGNORE && _context.chains_2[n2] <= 0)
         break;
   }

   if (n2 >= _context.g2.vertexEnd())
      return false;

   if (n1 < 0)
   {
      if (n1 != EmbeddingEnumerator::UNMAPPED && n1 != EmbeddingEnumerator::TERM_OUT)
         throw Error("some strange situation");

      n1 = -1;
   }

   return true;
}

bool TautomerChainChecker::isFeasibleStartingPair (int n1, int n2, int &h_diff)
{
   //if (n2 != -1 && _context.chains_2[n2] > 0)
   //   return false;

   if (n1 < 0)
   {
      h_diff = 0;
      return true;
   }

   if (!TautomerMatcher::matchAtomsTau(_context.g1, _context.g2, n1, n2))
      return false;

   int h_count_2 = _context.g2.getAtomTotalH(n2);
   int h_rep_1 = 0;

   if (!_context.force_hydrogens)
   {
      h_rep_1 = _context.h_rep_count_1[n1];
      h_count_2 += _context.h_rep_count_2[n2];
   } else if (!_context.g1.possibleAtomCharge(n1, _context.g2.getAtomCharge(n2)))
      return false;

   bool more = false, less = false;

   if (_context.g1.possibleAtomTotalH(n1, h_count_2 - h_rep_1 + 1))
      more = true;
   if (_context.g1.possibleAtomTotalH(n1, h_count_2 - h_rep_1 - 1))
      less = true;
   
   if (!less && !more)
      return false;
   
   if (less && more)
      h_diff = 0;
   else if (more)
      h_diff = -1;
   else
      h_diff = 1;
   
   return true;
}

bool TautomerChainChecker::nextPair (int &n1, int &n2, int &e1, int &e2)
{
   const Vertex &vertex2 = _context.g2.getVertex(_prev_n2);

   if (e2 == -1)
      e2 = vertex2.neiBegin();
   else
      e2 = vertex2.neiNext(e2);

   for (; e2 != vertex2.neiEnd(); e2 = vertex2.neiNext(e2))
   {
      n2 = vertex2.neiVertex(e2);

      if (_context.chains_2[n2] == 0 && _core_2[n2] != EmbeddingEnumerator::IGNORE)
         break;
   }

   if (e2 == vertex2.neiEnd())
      return false;

   e1 = -1;

   if ((n1 = _core_2[n2]) < 0)
      n1 = -1;
   else if (_prev_n1 != -1)
   {
      const Vertex &vertex1 = _context.g1.getVertex(_prev_n1);

      e1 = vertex1.findNeiEdge(_core_2[n2]);
   }

   return true;
}

int TautomerChainChecker::isFeasiblePair (int n1, int n2, TautomerChainChecker &next1, TautomerChainChecker &next2)
{
   //if (n1 == -1 && _prev_n1 == -1)
   //   return 0;

   //if (n2 != -1 && _context.chains_2[n2] > 0)
   //   return 0;

   if (_prev_n1 != -1 && n1 != -1 && _context.decomposer1.getComponent(_prev_n1) != _context.decomposer1.getComponent(n1))
      return 0;
   if (_prev_n2 != -1 && n2 != -1 && _context.decomposer2.getComponent(_prev_n2) != _context.decomposer2.getComponent(n2))
      return 0;
   
   if (_context.g2.isPseudoAtom(n2) || _context.g2.isTemplateAtom(n2)) // n1 are checked in matchAtomsTau later
      return 0;

   int h_diff = _h_difference;

   int edge2 = _context.g2.findEdgeIndex(_prev_n2, n2);

   int type1 = 0;
   int type2 = 0;

   bool zero_bond = _is_zero_bond_present;
   bool query_bond = _is_query_bond_present;
   bool na_bond = _is_non_aromatic_bond_present;

   int bond_type2 = 0;

   bool tau_bond = true;

   if (edge2 == -1)
   {
      zero_bond = true;
   } else
   {
      type2 = _context.g2.getBondOrder(edge2);

      if (type2 == -1 && _context.g2.possibleBondOrder(edge2, BOND_SINGLE))
         type2 = BOND_ZEROED;

      if (type2 == BOND_ZEROED)
      {
         if (_is_zero_bond_present)
            return 0;

         zero_bond = true;
      }
   }

   int edge1 = -1;

   if (n1 != -1)
   {
      if (_prev_n1 != -1)
         edge1 = _context.g1.findEdgeIndex(_prev_n1, n1);

      if (edge1 != -1)
      {
         type1 = _context.g1.getBondOrder(edge1);

         if (type1 == -1)
            return 0;
      }
   }

   if (type1 == BOND_AROMATIC || type1 == BOND_TRIPLE || type2 == BOND_TRIPLE)
      return 0;

   // Check degrees on previous vertices
   if (_prev_n1 != -1 && _path_length != 1)
   {
      const Vertex &prev_vert1 = _context.g1.getVertex(_prev_n1);
      const Vertex &prev_vert2 = _context.g2.getVertex(_prev_n2);

      int i;

      int bond_count1 = prev_vert1.degree();
      int prev_value_chain = _context.chains_2[_core_1[_prev_n1]];

      for (i = prev_vert1.neiBegin(); i < prev_vert1.neiEnd(); i = prev_vert1.neiNext(i))
      {
         int value_chain = _context.chains_2[_core_1[prev_vert1.neiVertex(i)]];

         if (value_chain > 0 && abs(value_chain - prev_value_chain) == 1)
            bond_count1--;
      }

      int bond_count2 = prev_vert2.degree();

      for (i = prev_vert2.neiBegin(); i < prev_vert2.neiEnd(); i = prev_vert2.neiNext(i))
      {
         int value_chain = _context.chains_2[prev_vert2.neiVertex(i)];

         if ((value_chain > 0 && abs(value_chain - prev_value_chain) == 1) ||
              (_context.g2.getBondOrder(prev_vert2.neiEdge(i)) == -1 &&
               _context.g2.possibleBondOrder(prev_vert2.neiEdge(i), BOND_SINGLE)))
            bond_count2--;
      }

      if (type1 == 0)
         bond_count1++;

      if (type2 == 0)
         bond_count2++;

      //if (bond_count1 != bond_count2)
      if (bond_count1 > bond_count2 || bond_count2 - bond_count1 > 1)
         return 0;
   }

   // zero bond must be
   if (edge1 == -1 && type2 == BOND_SINGLE && _h_difference == 1)
   {
      if (zero_bond)
         return 0;

      zero_bond = true;
   }
	
   if (zero_bond && !_is_zero_bond_present)
   {
      // Assume that aromatic ring cannot be destroyed
      if (type2 > 1)
         return 0;
      if (type2 == BOND_SINGLE)
      {
         if (_h_difference != 0)
         {
            if (_h_difference != 1)
               return 0;
         } else 
            h_diff = 1;
      }
   }

   if (edge1 == -1 || type2 == BOND_AROMATIC)
      tau_bond = false;

   if (edge1 != -1)
      query_bond = true;

   if (type2 != BOND_AROMATIC)
      na_bond = true;

   if (type1 != 0)
   {
      if (type2 != BOND_AROMATIC) // both non-aromatic
      {
         if (_h_difference != 0)
         {
            if (type1 + _h_difference != type2)
               return 0;
         } else if (abs(h_diff = (type2 - type1)) != 1)
               return 0;
      } else // exactly one aromatic
      {
         if (_h_difference != 0)
         {
            bond_type2 = type1 + _h_difference;

            if (bond_type2 < 1 || bond_type2 > 2)
               return 0;

            if (!_context.dearomatizationMatcher->isAbleToFixBond(edge2, bond_type2))
               return 0;
         } else 
         {
            if (type1 == BOND_SINGLE)
            {
               h_diff = 1;
               bond_type2 = 2;
            } else if (type1 == BOND_DOUBLE)
            {
               h_diff = -1;
               bond_type2 = 1;
            }

            if (bond_type2 > 0 && !_context.dearomatizationMatcher->isAbleToFixBond(edge2, bond_type2))
               return 0;
         }
      }
   }

   int rc = 0;

   if (n1 != -1)
   {
      if (!TautomerMatcher::matchAtomsTau(_context.g1, _context.g2, n1, n2))
         return 0;

      int h_rep_1 = 0;
      int h_count_2 = _context.g2.getAtomTotalH(n2);

      if (!_context.force_hydrogens)
      {
         h_rep_1 = _context.h_rep_count_1[n1];
         h_count_2 += _context.h_rep_count_2[n2];
      }

      if (query_bond && na_bond)
      {
         if (h_diff != 0)
         {
            if (!(_path_length & 1))
               if (_context.g1.possibleAtomTotalH(n1, h_count_2 + h_diff - h_rep_1))
               {
                  if (_context.cb_check_rules == 0 || _context.cb_check_rules(_context, _start_idx1, _start_idx2, n1, n2))
                     rc += 2;
               } 
         } else if (!(_path_length & 1))
            if (_context.g1.possibleAtomTotalH(n1, h_count_2 + 1 - h_rep_1) ||
                _context.g1.possibleAtomTotalH(n1, h_count_2 - 1 - h_rep_1))
            {
               if (_context.cb_check_rules == 0 || _context.cb_check_rules(_context, _start_idx1, _start_idx2, n1, n2))
                  rc += 2;
            }
      }

      if (_context.g1.possibleAtomTotalH(n1, h_count_2 - h_rep_1))
      {
         int charge_2 = _context.g2.getAtomCharge(n2);

         if (_context.g1.possibleAtomCharge(n1, charge_2))
            rc++;
      }
   } else
   {
      rc++;

      if (!(_path_length & 1) && query_bond && na_bond)
      {
         if (_context.cb_check_rules == 0 || _context.cb_check_rules(_context, _start_idx1, _start_idx2, n1, n2))
            rc += 2;
      } 
   }

   if (rc & 1)
   {
      next1._path_length++;
      next1._h_difference = -h_diff;
      next1._is_zero_bond_present = zero_bond;
      next1._is_query_bond_present = query_bond;
      next1._is_non_aromatic_bond_present = na_bond;

      if (tau_bond)
         next1._tau_bonds_to_match--;

      next1._bond_idx1 = edge1;
      next1._bond_idx2 = edge2;
      next1._bond_type2 = bond_type2 > 0 ? bond_type2 : type2;
   }

   if (rc & 2)
   {
      next2._final_path_length = next2._path_length + 1;
      next2._path_length = 0;
      next2._h_difference = 0;
      next2._final_h_difference = -h_diff;
      next2._is_query_bond_present = false;
      next2._is_non_aromatic_bond_present = false;
      //next2._is_zero_bond_present = false;
      next2._is_zero_bond_present = true;

      if (tau_bond)
         next2._tau_bonds_to_match--;

      next2._bond_idx1 = edge1;
      next2._bond_idx2 = edge2;
      next2._bond_type2 = bond_type2 > 0 ? bond_type2 : type2;
   }

   return rc;
}

void TautomerChainChecker::addPair (int n1, int n2)
{
   _context.chains_2[n2] = _path_number;

   _context.n1.expand(_path_number + 1);
   _context.n2.expand(_path_number + 1);
   _context.n1[_path_number] = n1;
   _context.n2[_path_number] = n2;

   _context.edges_1.expand(_path_number + 1);
   _context.edges_2.expand(_path_number + 1);
   _context.edge_types_2.expand(_path_number + 1);

   _context.edges_1[_path_number] = _bond_idx1;
   _context.edges_2[_path_number] = _bond_idx2;
   _context.edge_types_2[_path_number] = _bond_type2;

   _path_number++;

   _prev_n1 = n1;
   _prev_n2 = n2;

   if (_path_length == 0)
   {
      _start_idx1 = n1;
      _start_idx2 = n2;
   }

   if (_bond_type2 > 0 && _bond_type2 != BOND_AROMATIC)
      _context.dearomatizationMatcher->fixBond(_bond_idx2, _bond_type2);

#ifdef TRACE_TAUTOMER_MATCHING
   for (int i = 0; i < _path_number; i++)
      printf("  ");
   printf("%2d\n", n1 + 1);
   for (int i = 0; i < _path_number; i++)
      printf("  ");
   printf("%2d\n", n2 + 1);
#endif
}

void TautomerChainChecker::restore ()
{
   _context.chains_2[_prev_n2] = 0;
   if (_bond_type2 > 0 && _bond_type2 != BOND_AROMATIC)
      _context.dearomatizationMatcher->unfixBond(_bond_idx2);
}

// Make chain as in target
bool TautomerChainChecker::releaseChain ()
{
   if (_final_h_difference == 0)
      throw Error("unknown hydrogen difference");

   //if (_bond_type1 < 0 || _bond_type1 > 2 || _bond_type2 == BOND_AROMATIC)
   //   throw Error("bad bond type");

   int i = 1;
   int type, idx1, idx2, new_idx;
   int beg, end;
   BaseMolecule &query = _context.g1;
   BaseMolecule &target = _context.g2;
   int h_diff = _final_h_difference;
   bool res = true;

   for (i = 1; i < _final_path_length; i++, h_diff *= -1)
   {
      type = _context.edge_types_2[_path_number - i];
      idx1 = _context.edges_1[_path_number - i];
      idx2 = _context.edges_2[_path_number - i];

      if (type == BOND_AROMATIC)
      {
         if (idx1 < 0)
         {
            bool can_be_single = _context.dearomatizationMatcher->isAbleToFixBond(idx2, BOND_SINGLE);
            bool can_be_double = _context.dearomatizationMatcher->isAbleToFixBond(idx2, BOND_DOUBLE);

            if (can_be_single != can_be_double)
               type = can_be_single ? BOND_SINGLE : BOND_DOUBLE;
         } else
         {
            if (h_diff == 1)
               type = BOND_SINGLE;
            else
               type = BOND_DOUBLE;
         }
      }

      if (type > 0 && idx1 < 0)
      {
         // Forbidden zero bond
         if (!_context.ring_chain && type == BOND_SINGLE && h_diff == -1)
            res = false;
         
         const Edge &edge2 = target.getEdge(idx2);

         beg = _context.core_2[edge2.beg];
         if (beg < 0)
         {
            if (_context.substructure)
            {
               QueryMolecule &qmol = query.asQueryMolecule();

               new_idx = qmol.addAtom(new QueryMolecule::Atom(QueryMolecule::ATOM_NUMBER, target.getAtomNumber(edge2.beg)));
               if (target.getAtomCharge(edge2.beg) != 0)
               {
                  qmol.resetAtom(new_idx, QueryMolecule::Atom::und(
                          qmol.releaseAtom(new_idx),
                          new QueryMolecule::Atom(QueryMolecule::ATOM_CHARGE, target.getAtomCharge(edge2.beg))));
               }
            }
            else
            {
               Molecule &mol = query.asMolecule();

               new_idx = mol.addAtom(target.getAtomNumber(edge2.beg));
               mol.setAtomCharge(new_idx, target.getAtomCharge(edge2.beg));
            }

            _context.core_2[edge2.beg] = new_idx;
            _context.core_1.expand(new_idx + 1);
            _context.core_1[new_idx] = edge2.beg;
         }

         end = _context.core_2[edge2.end];
         if (end < 0)
         {
            if (_context.substructure)
            {
               QueryMolecule &qmol = query.asQueryMolecule();

               new_idx = qmol.addAtom(new QueryMolecule::Atom(QueryMolecule::ATOM_NUMBER, target.getAtomNumber(edge2.end)));
               if (target.getAtomCharge(edge2.end) != 0)
               {
                  qmol.resetAtom(new_idx, QueryMolecule::Atom::und(
                          qmol.releaseAtom(new_idx),
                          new QueryMolecule::Atom(QueryMolecule::ATOM_CHARGE, target.getAtomCharge(edge2.end))));
               }
            }
            else
            {
               Molecule &mol = query.asMolecule();

               new_idx = mol.addAtom(target.getAtomNumber(edge2.end));
               mol.setAtomCharge(new_idx, target.getAtomCharge(edge2.end));
            }


            _context.core_2[edge2.end] = new_idx;
            _context.core_1.expand(new_idx + 1);
            _context.core_1[new_idx] = edge2.end;
         }

         int new_bond_idx;

         if (_context.substructure)
         {
            QueryMolecule &qmol = query.asQueryMolecule();

            new_bond_idx = qmol.addBond(_context.core_2[edge2.beg], _context.core_2[edge2.end],
                    new QueryMolecule::Bond(QueryMolecule::BOND_ORDER, type));
         }
         else
         {
            Molecule &mol = query.asMolecule();

            new_bond_idx = mol.addBond(_context.core_2[edge2.beg], _context.core_2[edge2.end], type);
         }

         _context.edges_1[_path_number - i] = -2 - new_bond_idx;
      } else if (idx1 >= 0)
      {
         if (_context.substructure)
         {
            QueryMolecule &qmol = query.asQueryMolecule();

            qmol.resetBond(idx1,
                    new QueryMolecule::Bond(QueryMolecule::BOND_ORDER, type));
         }
         else
         {
            Molecule &mol = query.asMolecule();

            mol.setBondOrder(idx1, type);
         }
      }
   }
   return res;
}

// Restore original chain
void TautomerChainChecker::restoreChain ()
{
   int diff = _final_h_difference;
   int i = 1;
   int type, idx1, vidx1, vidx2;
   BaseMolecule &query = _context.g1;

   for (i = 1; i < _final_path_length; i++, diff *= -1)
   {
      type = _context.edge_types_2[_path_number - i] + diff;
      idx1 = _context.edges_1[_path_number - i];

      if (idx1 < -1)
      {
         idx1 = -idx1 - 2;

         query.removeBond(idx1);
         _context.edges_1[_path_number - i] = -1;
      } else if (idx1 >= 0)
      {
         if (_context.substructure)
         {
            QueryMolecule &qmol = query.asQueryMolecule();

            qmol.resetBond(idx1,
                    new QueryMolecule::Bond(QueryMolecule::BOND_ORDER, type));
         }
         else
         {
            Molecule &mol = query.asMolecule();

            mol.setBondOrder(idx1, type);
         }
      }


      if (_context.n1[_path_number - i] < 0)
      {
         vidx2 = _context.n2[_path_number - i];
         vidx1 = _context.core_2[vidx2];

         if (vidx1 >= 0)
         {
            query.removeAtom(vidx1);
            _context.core_1[vidx1] = -1;
            _context.core_2[vidx2] = -1;
         }
      }
   }

   if (_context.n1[_path_number - i] < 0)
   {
      vidx2 = _context.n2[_path_number - i];
      vidx1 = _context.core_2[vidx2];

      if (vidx1 >= 0)
      {
         query.removeAtom(vidx1);
         _context.core_1[vidx1] = -1;
         _context.core_2[vidx2] = -1;
      }
   }
}

bool TautomerChainChecker::_checkInterPathBonds ()
{
   BaseMolecule &g1 = _context.g1;
   BaseMolecule &g2 = _context.g2;

   if (_prev_n1 != -1)
   {
      const Vertex &vertex = g1.getVertex(_prev_n1);

      int idx1, idx2;

      for (int i = vertex.neiBegin(); i < vertex.neiEnd(); i = vertex.neiNext(i))
      {
         int nei_idx = vertex.neiVertex(i);

         if (_context.core_1[nei_idx] < 0 || _context.chains_2[_context.core_1[nei_idx]] == 0)
            continue;

         if (abs(_context.chains_2[_context.core_1[_prev_n1]] - _context.chains_2[_context.core_1[nei_idx]]) != 1)
         {
            idx1 = vertex.neiEdge(i);
            idx2 = g2.findEdgeIndex(_context.core_1[_prev_n1], _context.core_1[nei_idx]);

            int type1 = g1.getBondOrder(idx1);
            int type2 = g2.getBondOrder(idx2);

            bool matched;

            if (_context.substructure)
            {
               matched = MoleculeSubstructureMatcher::matchQueryBond(&(g1.asQueryMolecule()).getBond(idx1),
                       g2, idx1, idx2, 0, 0xFFFFFFFFUL);
            }
            else
            {
               matched = (g1.getBondOrder(idx1) == g2.getBondOrder(idx2));
            }
            
            if (!matched)
            {
               if (type1 != BOND_AROMATIC && type2 == BOND_AROMATIC)
               {
                  if (!_context.dearomatizationMatcher->isAbleToFixBond(idx2, type1))
                     return false;
               } else
                  return false;
            }
         }
      }
   }

   return true;
}


bool TautomerChainChecker::_matchAromBonds (Graph &subgraph, Graph &supergraph,
                                            int sub_idx, int super_idx, void *userdata)
{
   AromaticityMatcher *am = (AromaticityMatcher *)userdata;
   QueryMolecule::Bond *bond = &((BaseMolecule &)subgraph).asQueryMolecule().getBond(sub_idx);
   
   return MoleculeSubstructureMatcher::matchQueryBond(bond, (BaseMolecule &)supergraph, sub_idx, super_idx, am, 0xFFFFFFFFUL);
}

void TautomerChainChecker::_removeAtom (Graph &subgraph, int sub_idx, void *userdata)
{
   AromaticityMatcher *am = (AromaticityMatcher *)userdata;
 
   MoleculeSubstructureMatcher::removeAtom(subgraph, sub_idx, am);
}
 
void TautomerChainChecker::_addBond (Graph &subgraph, Graph &supergraph,
                                     int sub_idx, int super_idx, void *userdata)
{
   AromaticityMatcher *am = (AromaticityMatcher *)userdata;

   MoleculeSubstructureMatcher::addBond(subgraph, supergraph, sub_idx, super_idx, am);
}

int TautomerChainChecker::_embedding (Graph &subgraph, Graph &supergraph,
                                       int *core_sub, int *core_super, void *userdata)
{
   AromaticityMatcher *am = (AromaticityMatcher *)userdata;
   QueryMolecule &query = ((BaseMolecule &)subgraph).asQueryMolecule();
   BaseMolecule &target = (BaseMolecule &)supergraph;
   
   if (!MoleculeStereocenters::checkSub(query.stereocenters, target.stereocenters, core_sub, false))
      return 1;
   
   if (!MoleculeCisTrans::checkSub(query, target, core_sub))
      return 1;
   
   // Check possible aromatic configuration
   if (am != 0)
   {
      if (!am->match(core_sub, core_super))
         return 1;
   }
   
   return 0;
}

bool TautomerChainChecker::_matchAromatizedQuery()
{
   QS_DEF(QueryMolecule, aromatized_query);
   QS_DEF(Array<int>, mapping);

   aromatized_query.clone(((BaseMolecule &)_context.g1).asQueryMolecule(), 0, &mapping);
   QueryMoleculeAromatizer::aromatizeBonds(aromatized_query, _context.arom_options);

   EmbeddingEnumerator ee(_context.g2);

   ee.setSubgraph(aromatized_query);

   AromaticityMatcher am(aromatized_query, (Molecule &)_context.g2, _context.arom_options);

   ee.userdata = &am;

   ee.cb_match_edge = _matchAromBonds;
   ee.cb_vertex_remove = _removeAtom;
   ee.cb_edge_add = _addBond;
   ee.cb_embedding = _embedding;

   int i;

   for (i = _context.g1.vertexBegin(); i < _context.g1.vertexEnd(); i = _context.g1.vertexNext(i))
   {
      int val = _context.core_1[i];

      if (val == EmbeddingEnumerator::IGNORE)
         ee.ignoreSubgraphVertex(i);
      else if (!ee.fix(mapping[i], val))
         return false;
   }

   if (!ee.process())
      return true;
   return false;
}
