// 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 op_prod
//! @{

template <typename eT>
inline void op_prod::apply_noalias(Mat<eT>& out, const Mat<eT>& X, const uword dim) {
  arma_debug_sigprint();

  const uword X_n_rows = X.n_rows;
  const uword X_n_cols = X.n_cols;

  if (dim == 0)  // traverse across rows (ie. find the product in each column)
  {
    out.set_size(1, X_n_cols);

    eT* out_mem = out.memptr();

    for (uword col = 0; col < X_n_cols; ++col) {
      out_mem[col] = arrayops::product(X.colptr(col), X_n_rows);
    }
  } else  // traverse across columns (ie. find the product in each row)
  {
    out.ones(X_n_rows, 1);

    eT* out_mem = out.memptr();

    for (uword col = 0; col < X_n_cols; ++col) {
      const eT* X_col_mem = X.colptr(col);

      for (uword row = 0; row < X_n_rows; ++row) {
        out_mem[row] *= X_col_mem[row];
      }
    }
  }
}

template <typename T1>
inline void op_prod::apply(Mat<typename T1::elem_type>& out, const Op<T1, op_prod>& in) {
  arma_debug_sigprint();

  typedef typename T1::elem_type eT;

  const uword dim = in.aux_uword_a;

  arma_conform_check((dim > 1), "prod(): parameter 'dim' must be 0 or 1");

  const quasi_unwrap<T1> U(in.m);

  if (U.is_alias(out)) {
    Mat<eT> tmp;

    op_prod::apply_noalias(tmp, U.M, dim);

    out.steal_mem(tmp);
  } else {
    op_prod::apply_noalias(out, U.M, dim);
  }
}

template <typename eT>
inline eT op_prod::prod(const subview<eT>& X) {
  arma_debug_sigprint();

  eT val = eT(1);

  const uword X_n_rows = X.n_rows;
  const uword X_n_cols = X.n_cols;

  if (X_n_rows == 1) {
    const Mat<eT>& A = X.m;

    const uword start_row = X.aux_row1;
    const uword start_col = X.aux_col1;

    const uword end_col_p1 = start_col + X_n_cols;

    uword i, j;
    for (i = start_col, j = start_col + 1; j < end_col_p1; i += 2, j += 2) {
      val *= A.at(start_row, i);
      val *= A.at(start_row, j);
    }

    if (i < end_col_p1) {
      val *= A.at(start_row, i);
    }
  } else {
    for (uword col = 0; col < X_n_cols; ++col) {
      val *= arrayops::product(X.colptr(col), X_n_rows);
    }
  }

  return val;
}

template <typename T1>
inline typename T1::elem_type op_prod::prod(const Base<typename T1::elem_type, T1>& X) {
  arma_debug_sigprint();

  typedef typename T1::elem_type eT;

  const Proxy<T1> P(X.get_ref());

  eT val = eT(1);

  if (Proxy<T1>::use_at == false) {
    typedef typename Proxy<T1>::ea_type ea_type;

    const ea_type A = P.get_ea();

    const uword n_elem = P.get_n_elem();

    uword i, j;
    for (i = 0, j = 1; j < n_elem; i += 2, j += 2) {
      val *= A[i];
      val *= A[j];
    }

    if (i < n_elem) {
      val *= A[i];
    }
  } else {
    const uword n_rows = P.get_n_rows();
    const uword n_cols = P.get_n_cols();

    if (n_rows == 1) {
      uword i, j;
      for (i = 0, j = 1; j < n_cols; i += 2, j += 2) {
        val *= P.at(0, i);
        val *= P.at(0, j);
      }

      if (i < n_cols) {
        val *= P.at(0, i);
      }
    } else {
      for (uword col = 0; col < n_cols; ++col) {
        uword i, j;
        for (i = 0, j = 1; j < n_rows; i += 2, j += 2) {
          val *= P.at(i, col);
          val *= P.at(j, col);
        }

        if (i < n_rows) {
          val *= P.at(i, col);
        }
      }
    }
  }

  return val;
}

//! @}
