// 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 fn_n_unique
//! @{

//! \brief
//! Get the number of unique nonzero elements in two sparse matrices.
//! This is very useful for determining the amount of memory necessary before
//! a sparse matrix operation on two matrices.

template <typename T1, typename T2, typename op_n_unique_type>
inline uword n_unique(const SpBase<typename T1::elem_type, T1>& x,
                      const SpBase<typename T2::elem_type, T2>& y,
                      const op_n_unique_type junk) {
  arma_debug_sigprint();

  const SpProxy<T1> pa(x.get_ref());
  const SpProxy<T2> pb(y.get_ref());

  return n_unique(pa, pb, junk);
}

template <typename T1, typename T2, typename op_n_unique_type>
arma_hot inline uword n_unique(const SpProxy<T1>& pa, const SpProxy<T2>& pb,
                               const op_n_unique_type junk) {
  arma_debug_sigprint();
  arma_ignore(junk);

  typename SpProxy<T1>::const_iterator_type x_it = pa.begin();
  typename SpProxy<T1>::const_iterator_type x_it_end = pa.end();

  typename SpProxy<T2>::const_iterator_type y_it = pb.begin();
  typename SpProxy<T2>::const_iterator_type y_it_end = pb.end();

  uword total_n_nonzero = 0;

  while ((x_it != x_it_end) || (y_it != y_it_end)) {
    if (x_it == y_it) {
      if (op_n_unique_type::eval((*x_it), (*y_it)) != typename T1::elem_type(0)) {
        ++total_n_nonzero;
      }

      ++x_it;
      ++y_it;
    } else {
      if ((x_it.col() < y_it.col()) ||
          ((x_it.col() == y_it.col()) &&
           (x_it.row() < y_it.row())))  // if y is closer to the end
      {
        if (op_n_unique_type::eval((*x_it), typename T1::elem_type(0)) !=
            typename T1::elem_type(0)) {
          ++total_n_nonzero;
        }

        ++x_it;
      } else  // x is closer to the end
      {
        if (op_n_unique_type::eval(typename T1::elem_type(0), (*y_it)) !=
            typename T1::elem_type(0)) {
          ++total_n_nonzero;
        }

        ++y_it;
      }
    }
  }

  return total_n_nonzero;
}

// Simple operators.
struct op_n_unique_add {
  template <typename eT>
  inline static eT eval(const eT& l, const eT& r) {
    return (l + r);
  }
};

struct op_n_unique_sub {
  template <typename eT>
  inline static eT eval(const eT& l, const eT& r) {
    return (l - r);
  }
};

struct op_n_unique_mul {
  template <typename eT>
  inline static eT eval(const eT& l, const eT& r) {
    return (l * r);
  }
};

struct op_n_unique_count {
  template <typename eT>
  inline static eT eval(const eT&, const eT&) {
    return eT(1);
  }
};

//! @}
