//=====================================================
// Copyright (C) 2014 Benoit Steiner <benoit.steiner.goog@gmail.com>
//=====================================================
//
// This Source Code Form is subject to the terms of the Mozilla
// Public License v. 2.0. If a copy of the MPL was not distributed
// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
//
#ifndef TENSOR_INTERFACE_HH
#define TENSOR_INTERFACE_HH

#include <unsupported/Eigen/CXX11/Tensor>
#include <vector>
#include "btl.hh"

using namespace Eigen;

template <class real>
class tensor_interface {
 public:
  typedef real real_type;
  typedef typename Eigen::Tensor<real, 2>::Index Index;

  typedef std::vector<real> stl_vector;
  typedef std::vector<stl_vector> stl_matrix;

  typedef Eigen::Tensor<real, 2> gene_matrix;
  typedef Eigen::Tensor<real, 1> gene_vector;

  static inline std::string name(void) { return EIGEN_MAKESTRING(BTL_PREFIX); }

  static void free_matrix(gene_matrix& /*A*/, int /*N*/) {}

  static void free_vector(gene_vector& /*B*/) {}

  static BTL_DONT_INLINE void matrix_from_stl(gene_matrix& A, stl_matrix& A_stl) {
    A.resize(Eigen::array<Index, 2>(A_stl[0].size(), A_stl.size()));

    for (unsigned int j = 0; j < A_stl.size(); j++) {
      for (unsigned int i = 0; i < A_stl[j].size(); i++) {
        A.coeffRef(Eigen::array<Index, 2>(i, j)) = A_stl[j][i];
      }
    }
  }

  static BTL_DONT_INLINE void vector_from_stl(gene_vector& B, stl_vector& B_stl) {
    B.resize(B_stl.size());

    for (unsigned int i = 0; i < B_stl.size(); i++) {
      B.coeffRef(i) = B_stl[i];
    }
  }

  static BTL_DONT_INLINE void vector_to_stl(gene_vector& B, stl_vector& B_stl) {
    for (unsigned int i = 0; i < B_stl.size(); i++) {
      B_stl[i] = B.coeff(i);
    }
  }

  static BTL_DONT_INLINE void matrix_to_stl(gene_matrix& A, stl_matrix& A_stl) {
    int N = A_stl.size();

    for (int j = 0; j < N; j++) {
      A_stl[j].resize(N);
      for (int i = 0; i < N; i++) {
        A_stl[j][i] = A.coeff(Eigen::array<Index, 2>(i, j));
      }
    }
  }

  static inline void matrix_matrix_product(const gene_matrix& A, const gene_matrix& B, gene_matrix& X, int /*N*/) {
    typedef typename Eigen::Tensor<real_type, 1>::DimensionPair DimPair;
    const Eigen::array<DimPair, 1> dims(DimPair(1, 0));
    X /*.noalias()*/ = A.contract(B, dims);
  }

  static inline void matrix_vector_product(const gene_matrix& A, const gene_vector& B, gene_vector& X, int /*N*/) {
    typedef typename Eigen::Tensor<real_type, 1>::DimensionPair DimPair;
    const Eigen::array<DimPair, 1> dims(DimPair(1, 0));
    X /*.noalias()*/ = A.contract(B, dims);
  }

  static inline void axpy(real coef, const gene_vector& X, gene_vector& Y, int /*N*/) { Y += X.constant(coef) * X; }

  static inline void axpby(real a, const gene_vector& X, real b, gene_vector& Y, int /*N*/) {
    Y = X.constant(a) * X + Y.constant(b) * Y;
  }

  static EIGEN_DONT_INLINE void copy_matrix(const gene_matrix& source, gene_matrix& cible, int /*N*/) {
    cible = source;
  }

  static EIGEN_DONT_INLINE void copy_vector(const gene_vector& source, gene_vector& cible, int /*N*/) {
    cible = source;
  }
};

#endif