// 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 glue_cor
//! @{

template <typename T1, typename T2>
inline void glue_cor::apply(Mat<typename T1::elem_type>& out,
                            const Glue<T1, T2, glue_cor>& X) {
  arma_extra_debug_sigprint();

  typedef typename T1::elem_type eT;

  const uword norm_type = X.aux_uword;

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

  const Mat<eT>& A = UA.M;
  const Mat<eT>& B = UB.M;

  const Mat<eT>& AA =
      (A.n_rows == 1)
          ? Mat<eT>(const_cast<eT*>(A.memptr()), A.n_cols, A.n_rows, false, false)
          : Mat<eT>(const_cast<eT*>(A.memptr()), A.n_rows, A.n_cols, false, false);

  const Mat<eT>& BB =
      (B.n_rows == 1)
          ? Mat<eT>(const_cast<eT*>(B.memptr()), B.n_cols, B.n_rows, false, false)
          : Mat<eT>(const_cast<eT*>(B.memptr()), B.n_rows, B.n_cols, false, false);

  arma_debug_assert_mul_size(AA, BB, true, false, "cor()");

  if ((AA.n_elem == 0) || (BB.n_elem == 0)) {
    out.reset();
    return;
  }

  const uword N = AA.n_rows;
  const eT norm_val = (norm_type == 0) ? ((N > 1) ? eT(N - 1) : eT(1)) : eT(N);

  const Mat<eT> tmp1 = AA.each_row() - mean(AA, 0);
  const Mat<eT> tmp2 = BB.each_row() - mean(BB, 0);

  out = tmp1.t() * tmp2;
  out /= norm_val;

  out /= conv_to<Mat<eT> >::from(stddev(AA).t() * stddev(BB));  // TODO: check for zeros?
}

//! @}
