/*******************************************************************************
 *
 * TRIQS: a Toolbox for Research in Interacting Quantum Systems
 *
 * Copyright (C) 2012-2013 by O. Parcollet
 *
 * TRIQS 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 3 of the License, or (at your option) any later
 * version.
 *
 * TRIQS 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
 * TRIQS. If not, see <http://www.gnu.org/licenses/>.
 *
 ******************************************************************************/
#pragma once
#include "./mesh_tools.hpp"
#include "../domains/product.hpp"
#include <triqs/utility/tuple_tools.hpp>
#include <triqs/utility/mini_vector.hpp>
#include <triqs/utility/c14.hpp>
namespace triqs {
namespace gfs {

 /** Cartesian product of meshes
  */
 template <typename... Meshes> struct mesh_product : tag::composite {
  using domain_t = domain_product<typename Meshes::domain_t...>;
  using index_t = std::c14::tuple<typename Meshes::index_t...>;
  using m_tuple_t = std::tuple<Meshes...>;
  using m_pt_tuple_t = std::tuple<typename Meshes::mesh_point_t...>;
  using domain_pt_t = typename domain_t::point_t;

  static constexpr int dim = sizeof...(Meshes);

  mesh_product() {}
  mesh_product(Meshes const &... meshes) : m_tuple(meshes...), _dom(meshes.domain()...) {}

  domain_t const &domain() const { return _dom; }
  m_tuple_t const &components() const { return m_tuple; }
  m_tuple_t &components() { return m_tuple; }

  private:
  struct _aux0 {
   template <typename M> size_t operator()(M const &m, size_t R) { return R * m.size(); }
  };

  public:
  /// size of the mesh is the product of size
  size_t size() const { return triqs::tuple::fold(_aux0(), m_tuple, 1); }

  private:
  struct _aux1 {
   template <typename P, typename M, typename I> void operator()(P &p, M const &m, I const &i) { p = m.index_to_point(i); }
  };

  public:
  /// Conversions point <-> index <-> linear_index
  typename domain_t::point_t index_to_point(index_t const &ind) const {
   domain_pt_t res;
   triqs::tuple::apply_on_zip(_aux1(), res, m_tuple, ind);
   return res;
  }

  private:
  struct _aux2 {
   template <typename I, typename M> size_t operator()(M const &m, I const &i, size_t R) {
    return m.index_to_linear(i) + R * m.size();
   }
  };

  public:
  /// Flattening index to linear :  index[0] + component[0].size * (index[1] + component[1].size* (index[2] + ....))
  size_t index_to_linear(index_t const &ii) const {
   return triqs::tuple::fold_on_zip(_aux2(), reverse(m_tuple), reverse(ii), size_t(0));
  }
  // size_t index_to_linear(index_t const & ii) const { return triqs::tuple::fold_on_zip([](auto const &m, auto const &i, auto R)
  //{return m.index_to_linear(i) + R * m.size();} , m_tuple, ii, size_t(0)); }

  private:
  struct _aux3 {
   template <typename P, typename M> size_t operator()(M const &m, P const &p, size_t R) {
    return p.linear_index() + R * m.size();
   }
  };

  public:
  /// Flattening index to linear :  index[0] + component[0].size * (index[1] + component[1].size* (index[2] + ....))
  size_t mp_to_linear(m_pt_tuple_t const &mp) const {
   return triqs::tuple::fold_on_zip(_aux3(), reverse(m_tuple), reverse(mp), size_t(0));
  }

  //
  private:
  struct _aux4 {
   template <typename M, typename V> V *operator()(M const &m, V *v) {
    *v = m.size();
    return ++v;
   }
  };

  public:
  utility::mini_vector<size_t, dim> shape() const {
   utility::mini_vector<size_t, dim> res;
   triqs::tuple::fold(_aux4(), m_tuple, &res[0]);
   return res;
  }

  // Same but a variadic list of mesh_point_t
  template <typename... MP> size_t mesh_pt_components_to_linear(MP const &... mp) const {
   static_assert(std::is_same<std::tuple<MP...>, m_pt_tuple_t>::value, "Call incorrect ");
   // static_assert(std::is_same< std::tuple<typename std::remove_cv<typename std::remove_reference<MP>::type>::type...>,
   // m_pt_tuple_t>::value, "Call incorrect ");
   return mp_to_linear(std::forward_as_tuple(mp...));
  } // speed test ? or make a variadic fold...

  /// The wrapper for the mesh point
  class mesh_point_t : tag::mesh_point {
   const mesh_product *m;
   m_pt_tuple_t _c;
   bool _atend;
   struct F2 {
    template <typename M> typename M::mesh_point_t operator()(M const &m, typename M::index_t const &i) const { return m[i]; }
   };
   struct F1 {
    template <typename M> typename M::mesh_point_t operator()(M const &m) const { return {m}; }
   };

   public:
   mesh_point_t() = default;
   mesh_point_t(mesh_product const &m_, index_t index_)
      : m(&m_), _c(triqs::tuple::apply_on_zip(F2(), m_.m_tuple, index_)), _atend(false) {}
   mesh_point_t(mesh_product const &m_) : m(&m_), _c(triqs::tuple::apply_on_tuple(F1(), m_.m_tuple)), _atend(false) {}
   m_pt_tuple_t const &components_tuple() const { return _c; }
   size_t linear_index() const { return m->mp_to_linear(_c); }
   const mesh_product *mesh() const { return m; }

   using cast_t = domain_pt_t;
   operator cast_t() const { return m->index_to_point(index); }

   // index[0] +=1; if index[0]==m.component[0].size() { index[0]=0; index[1] +=1; if  ....}  and so on until dim
   private:
   struct _aux1 {
    template <typename P> bool operator()(P &p, bool done) {
     if (done) return true;
     p.advance();
     if (!p.at_end()) return true;
     p.reset();
     return false;
    }
   };

   public:
   void advance() { _atend = ! (triqs::tuple::fold(_aux1(), _c, false)) ; }

   // index_t index() const { return _index;} // not implemented yet
   bool at_end() const { return _atend; }

   private:
   struct _aux {
    template <typename M> size_t operator()(M &m, size_t) {
     m.reset();
     return 0;
    }
   };

   public:
   void reset() {
    _atend = false;
    triqs::tuple::fold(_aux(), _c, 0);
   }
  }; // end mesh_point_t

  /// Accessing a point of the mesh
  mesh_point_t operator[](index_t i) const { return mesh_point_t(*this, i); }
  mesh_point_t operator()(typename Meshes::index_t... i) const { return (*this)[std::make_tuple(i...)]; }

  /// Iterating on all the points...
  using const_iterator = mesh_pt_generator<mesh_product>;
  const_iterator begin() const { return const_iterator(this); }
  const_iterator end() const { return const_iterator(this, true); }
  const_iterator cbegin() const { return const_iterator(this); }
  const_iterator cend() const { return const_iterator(this, true); }

  /// Mesh comparison
  friend bool operator==(mesh_product const &M1, mesh_product const &M2) { return M1.m_tuple == M2.m_tuple; }
  
  private:

  /// Write into HDF5
  struct _auxh5w {
   h5::group gr;
   _auxh5w(h5::group gr_) : gr(gr_) {} // icc has yet another bug on new initialization form with {}...
   template <typename M> size_t operator()(M const &m, size_t N) {
    std::stringstream fs;
    fs << "MeshComponent" << N;
    h5_write(gr, fs.str(), m);
    return N + 1;
   }
  };

  friend void h5_write(h5::group fg, std::string subgroup_name, mesh_product const &m) {
   h5::group gr = fg.create_group(subgroup_name);
   // h5_write(gr,"domain",m.domain());
   triqs::tuple::fold(_auxh5w(gr), m.components(), size_t(0));
  }

  /// Read from HDF5
  struct _auxh5r {
   h5::group gr;
   _auxh5r(h5::group gr_) : gr(gr_) {}
   template <typename M> size_t operator()(M &m, size_t N) {
    std::stringstream fs;
    fs << "MeshComponent" << N;
    h5_read(gr, fs.str(), m);
    return N + 1;
   }
  };
  friend void h5_read(h5::group fg, std::string subgroup_name, mesh_product &m) {
   h5::group gr = fg.open_group(subgroup_name);
   // h5_read(gr,"domain",m._dom);
   triqs::tuple::fold(_auxh5r(gr), m.components(), size_t(0));
  }

  //  BOOST Serialization
  friend class boost::serialization::access;
  template <typename Archive> struct _aux_ser {
   Archive &ar;
   _aux_ser(Archive &ar_) : ar(ar_) {}
   template <typename M> size_t operator()(M &m, size_t N) {
    std::stringstream fs;
    fs << "MeshComponent" << N;
    ar &boost::serialization::make_nvp(fs.str().c_str(), m);
    return N + 1;
   }
  };
  template <class Archive> void serialize(Archive &ar, const unsigned int version) {
   triqs::tuple::fold(_aux_ser<Archive>(ar), m_tuple, size_t(0));
  }

  friend std::ostream &operator<<(std::ostream &sout, mesh_product const &m) { return sout << "Product Mesh"; }

  private:
  m_tuple_t m_tuple;
  domain_t _dom;
 };

 template <int pos, typename P> auto get_index(P const &p) DECL_AND_RETURN(std::get<pos>(p.components_tuple()).index());

 template <int pos, typename P>
 auto get_point(P const &p)
     DECL_AND_RETURN(std::get<pos>(p.mesh() -> components()).index_to_point(std::get<pos>(p.components_tuple()).index()));

 template <int pos, typename P> auto get_component(P const &p) DECL_AND_RETURN(std::get<pos>(p.components_tuple()));

 // Given a composite mesh m , and a linear array of storage A
 // reinterpret_linear_array(m,A) returns a d-dimensionnal view of the array
 // with indices egal to the indices of the components of the mesh.
 // Very useful for slicing, currying functions.
 template <typename... Meshes, typename T, ull_t OptionsFlags, ull_t To, int R, bool B, bool C>
 arrays::array_view<T, sizeof...(Meshes) + R - 1, OptionsFlags, To, true, C>
 reinterpret_linear_array(mesh_product<Meshes...> const &m, arrays::array_view<T, R, OptionsFlags, To, B, C> A) {
  return {{join(m.shape(), get_shape(A).front_pop())}, A.storage()};
 }
}
}