/* Copyright (c) 1997-2024
   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.
--------------------------------------------------------------------------------
*/

#pragma once

#include "polymake/PowerSet.h"
#include "polymake/graph/BasicLatticeTypes.h"
#include "polymake/graph/lattice_builder.h"

namespace polymake { namespace topaz {

using graph::lattice::BasicDecoration;
using graph::lattice::FaceIndexingData;

// Iterate either over all maximal cells (for the artificial top node)
// or over all subsets less one element.
class simplicial_closure_iterator {
public:
  using iterator_category = std::forward_iterator_tag;
  using value_type = Set<Int>;
  using reference = const value_type&;
  using pointer = const value_type*;
  using difference_type = ptrdiff_t;

  template <typename Iterable>
  explicit simplicial_closure_iterator(const Iterable& f)
  {
    for (auto f_it = entire(f); !f_it.at_end(); ++f_it)
      data.push_back(*f_it);
    it = entire(data);
  }

  reference operator* () const { return it.operator*(); }
  pointer operator->() const { return it.operator->(); }
  simplicial_closure_iterator& operator++ () { ++it; return *this; }
  const simplicial_closure_iterator operator++ (int) { simplicial_closure_iterator copy = *this; operator++(); return copy; }
  bool at_end() const { return it.at_end(); }

protected:
  std::list<Set<Int>> data;
  pm::iterator_range<std::list<Set<Int>>::const_iterator> it;
};


template <typename Decoration = BasicDecoration>
class SimplicialClosure {
public:
  using ClosureData = Set<Int>;

  SimplicialClosure(const IncidenceMatrix<>& facets_)
    : facets(facets_)
    , total_size(facets.cols()) {}

  ClosureData closure_of_empty_set() const
  {
    return sequence(0,facets.cols()+1);
  }

  ClosureData compute_closure_data(const Decoration& face) const
  {
    return face.face;
  }

  FaceIndexingData get_indexing_data(const ClosureData& data)
  {
    Int& fi = face_index_map[data];
    return FaceIndexingData(fi, fi == -1, fi == -2);
  }

  simplicial_closure_iterator get_closure_iterator(const ClosureData& face) const
  {
    return face.size() > total_size
           ? simplicial_closure_iterator(rows(facets))
           : simplicial_closure_iterator(all_subsets_less_1(face));
  }

protected:
  const IncidenceMatrix<> facets;
  const Int total_size;
  FaceMap<> face_index_map;
};

class SimplicialDecorator {
protected:
  const Set<Int> artificial_set;
  Int top_rank;
public:
  SimplicialDecorator(Int top_rank_arg, const Set<Int>& artificial_set_arg)
    : artificial_set(artificial_set_arg)
    , top_rank(top_rank_arg) {}

  template <typename TSet>
  BasicDecoration compute_initial_decoration(const GenericSet<TSet, Int>& face) const
  {
    return BasicDecoration(artificial_set, top_rank);
  }

  template <typename TSet>
  BasicDecoration compute_decoration(const GenericSet<TSet, Int>& face,
                                     const BasicDecoration& predecessor_data) const
  {
    return BasicDecoration(face, face.top().size());   
  }

  BasicDecoration compute_artificial_decoration(const NodeMap<Directed, BasicDecoration> &decor,
               const std::list<Int>& max_nodes) const
  {
    return BasicDecoration(Set<Int>(), 0);
  }
};

using namespace graph;
using namespace graph::lattice;
    
template<typename Container>      
Lattice<BasicDecoration>
hasse_diagram_from_facets(const Container& facets,
			  const RankRestriction& rr = RankRestriction(),
			  const Set<Int>& artificial_set = scalar2set(-1))
{
   const Set<Int> all_vertices = accumulate(facets, operations::add());
   const Int n_vertices = accumulate(all_vertices, operations::max())+1;
   const IncidenceMatrix<> maximal_cells(facets.size(), n_vertices, entire(facets));
      
   if (rr.rank_restricted && rr.rank_restriction_type == RankCutType::LesserEqual)
      throw std::runtime_error("Hasse diagram of SimplicialComplex is always built dually.");
   Int top_rank = 0;
   if (!facets.empty()) {
      for (const auto& f: facets)
         top_rank = std::max(top_rank, f.size());
      ++top_rank;
   }
   SimplicialClosure<BasicDecoration> closure(maximal_cells);
   SimplicialDecorator decorator(top_rank, artificial_set);
   if (!rr.rank_restricted) {
      return lattice_builder::compute_lattice_from_closure<BasicDecoration>(
               closure, TrivialCut<BasicDecoration>(), decorator, false, lattice_builder::Dual());
   } else {
      const auto cut_above = lattice::RankCut<lattice::BasicDecoration, lattice::RankCutType::GreaterEqual>(rr.boundary_rank);
      return lattice_builder::compute_lattice_from_closure<BasicDecoration>(
               closure, cut_above, decorator, rr.boundary_rank > 0, lattice_builder::Dual());
   }
}

BigObject upper_hasse_diagram(BigObject complex, Int boundary_rank);

} }

