/* Copyright (c) 1997-2020
   Ewgenij Gawrilow, Michael Joswig, and the polymake team
   Technische Universität Berlin, Germany
   https://polymake.org

   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, or (at your option) any
   later version: http://www.gnu.org/licenses/gpl.txt.

   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.
--------------------------------------------------------------------------------
*/

#ifndef POLYMAKE_GRAPH_LATTICE_PERMUTATION_H
#define POLYMAKE_GRAPH_LATTICE_PERMUTATION_H

#include "polymake/client.h"
#include "polymake/Graph.h"
#include "polymake/Set.h"
#include "polymake/Array.h"
#include "polymake/vector"
#include "polymake/IncidenceMatrix.h"
#include <algorithm>
#include "polymake/graph/Decoration.h"
#include "polymake/graph/Lattice.h"

namespace polymake { namespace graph { namespace lattice {

template <typename Decoration>
class CompareByFace {
private:
  const NodeMap<Directed, Decoration>& node_map;
public:
  CompareByFace(const NodeMap<Directed, Decoration>& nmap) : node_map(nmap) {}
  pm::cmp_value operator() (Int a, Int b) const
  {
    return operations::cmp()( node_map[a].face, node_map[b].face);
  }
};

// Sorts vertices by number and facets according to a specified order.
// Facets are not sorted if VIF.rows == 0
// @param Lattice The lattice to be sorted
// @param IncidenceMatrix<> VIF A list of facets prescribing the order of the facet nodes. If
// empty, only the rays are sorted.
template <typename Decoration, typename SeqType>
void sort_vertices_and_facets(Lattice<Decoration, SeqType> &l, const IncidenceMatrix<>& VIF)
{
  Array<Int> perm(sequence(0, l.nodes()));
         
  // First sort the vertices
  Set<Int> unsorted_nodes( l.nodes_of_rank(1));
  Set<Int, CompareByFace<Decoration> > vertex_nodes(CompareByFace<Decoration>(l.decoration()));
  for (auto nd : unsorted_nodes) { vertex_nodes += nd; }
  copy_range( entire(vertex_nodes), select(perm, unsorted_nodes).begin());

  // Then facets
  if (l.rank() > 2 && VIF.rows() > 0) {
    Array<Int> facet_nodes(l.nodes_of_rank(l.rank()-1));
    const IncidenceMatrix<> lfacets(VIF.rows(), VIF.cols(), 
      entire(attach_member_accessor( select(l.decoration(), facet_nodes), 
                                     ptr2type< Decoration, Set<Int>, &Decoration::face>())));
    const auto fperm = find_permutation(rows(lfacets), rows(VIF));
    if (fperm)
      copy_range(entire(permuted(facet_nodes, fperm.value())), select(perm, facet_nodes).begin());
    else
      throw std::runtime_error("sort_vertices_and_facets: decoration facets do not match the incidence matrix");
  }

  l.permute_nodes_in_levels(perm);
}

// This can be used to make a Lattice sequential. 
// Careful! This is fairly expensive for large lattices, since all data needs to be copied.
template <typename Decoration>
BigObject make_lattice_sequential(const Lattice<Decoration, lattice::Nonsequential> &lattice)
{
  Array<Int> node_perm(lattice.nodes());
  InverseRankMap<lattice::Sequential> new_rank_map;
  Int current_index = 0;
  for (auto rk_it = entire(lattice.inverse_rank_map().get_map()); !rk_it.at_end(); ++rk_it) {
    Int list_length = rk_it->second.size();
    copy_range(entire(sequence(current_index, list_length)), select(node_perm, rk_it->second).begin());
    std::pair<Int, Int> new_map_value(current_index, current_index+list_length-1);
    new_rank_map.set_rank_list( rk_it->first, new_map_value);
    current_index += list_length;
  }

  Graph<Directed> new_graph = permuted_inv_nodes( lattice.graph(), node_perm);
  NodeMap<Directed, Decoration> new_decoration(new_graph);
  copy_range(entire(lattice.decoration()), select(new_decoration, node_perm).begin());

  BigObject result("Lattice", mlist<Decoration, lattice::Sequential>());
  result.take("ADJACENCY") << new_graph;
  result.take("DECORATION") << new_decoration;
  result.take("INVERSE_RANK_MAP") << new_rank_map;
  result.take("TOP_NODE") << node_perm[ lattice.top_node()];
  result.take("BOTTOM_NODE") << node_perm[ lattice.bottom_node()];
  return result;
}

} } }

#endif
