// SPDX-License-Identifier: Apache-2.0
//
// Copyright 2008-2016 Conrad Sanderson (http://conradsanderson.id.au)
// Copyright 2008-2016 National ICT Australia (NICTA)
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// ------------------------------------------------------------------------

//! \addtogroup spglue_kron
//! @{

template <typename T1, typename T2>
inline void spglue_kron::apply(SpMat<typename T1::elem_type>& out,
                               const SpGlue<T1, T2, spglue_kron>& X) {
  arma_debug_sigprint();

  typedef typename T1::elem_type eT;

  const unwrap_spmat<T1> UA(X.A);
  const unwrap_spmat<T2> UB(X.B);

  if (UA.is_alias(out) || UB.is_alias(out)) {
    SpMat<eT> tmp;

    spglue_kron::apply_noalias(tmp, UA.M, UB.M);

    out.steal_mem(tmp);
  } else {
    spglue_kron::apply_noalias(out, UA.M, UB.M);
  }
}

template <typename eT>
inline void spglue_kron::apply_noalias(SpMat<eT>& out, const SpMat<eT>& A,
                                       const SpMat<eT>& B) {
  arma_debug_sigprint();

  const uword A_n_rows = A.n_rows;
  const uword A_n_cols = A.n_cols;

  const uword B_n_rows = B.n_rows;
  const uword B_n_cols = B.n_cols;

  const uword out_n_nonzero = A.n_nonzero * B.n_nonzero;

  out.reserve(A_n_rows * B_n_rows, A_n_cols * B_n_cols, out_n_nonzero);

  if (out_n_nonzero == 0) {
    return;
  }

  access::rw(out.col_ptrs[0]) = 0;

  uword count = 0;

  for (uword A_col = 0; A_col < A_n_cols; ++A_col)
    for (uword B_col = 0; B_col < B_n_cols; ++B_col) {
      for (uword A_i = A.col_ptrs[A_col]; A_i < A.col_ptrs[A_col + 1]; ++A_i) {
        const uword out_row = A.row_indices[A_i] * B_n_rows;

        const eT A_val = A.values[A_i];

        for (uword B_i = B.col_ptrs[B_col]; B_i < B.col_ptrs[B_col + 1]; ++B_i) {
          access::rw(out.values[count]) = A_val * B.values[B_i];
          access::rw(out.row_indices[count]) = out_row + B.row_indices[B_i];

          count++;
        }
      }

      access::rw(out.col_ptrs[A_col * B_n_cols + B_col + 1]) = count;
    }
}

// template<typename T1, typename T2>
// inline
// void
// spglue_kron::apply(SpMat<typename T1::elem_type>& out, const SpGlue<T1,T2,spglue_kron>&
// X)
//   {
//   arma_debug_sigprint();
//
//   typedef typename T1::elem_type eT;
//
//   const unwrap_spmat<T1> UA(X.A);
//   const unwrap_spmat<T2> UB(X.B);
//
//   const SpMat<eT>& A = UA.M;
//   const SpMat<eT>& B = UB.M;
//
//   umat    locs(2, A.n_nonzero * B.n_nonzero, arma_nozeros_indicator());
//   Col<eT> vals(   A.n_nonzero * B.n_nonzero, arma_nozeros_indicator());
//
//   uword* locs_mem = locs.memptr();
//   eT*    vals_mem = vals.memptr();
//
//   typename SpMat<eT>::const_iterator A_it     = A.begin();
//   typename SpMat<eT>::const_iterator A_it_end = A.end();
//
//   typename SpMat<eT>::const_iterator B_it_start = B.begin();
//   typename SpMat<eT>::const_iterator B_it_end   = B.end();
//
//   const uword B_n_rows = B.n_rows;
//   const uword B_n_cols = B.n_cols;
//
//   uword i = 0;
//
//   while(A_it != A_it_end)
//     {
//     typename SpMat<eT>::const_iterator B_it = B_it_start;
//
//     const uword loc_row = A_it.row() * B_n_rows;
//     const uword loc_col = A_it.col() * B_n_cols;
//
//     const eT A_val = (*A_it);
//
//     while(B_it != B_it_end)
//       {
//       (*locs_mem) = loc_row + B_it.row();  locs_mem++;
//       (*locs_mem) = loc_col + B_it.col();  locs_mem++;
//
//       vals_mem[i] = A_val * (*B_it);
//
//       ++i;
//       ++B_it;
//       }
//
//     ++A_it;
//     }
//
//   out = SpMat<eT>(locs, vals, A.n_rows*B.n_rows, A.n_cols*B.n_cols);
//   }

//! @}
