// 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_minus
//! @{

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

  typedef typename T1::elem_type eT;

  const SpProxy<T1> pa(X.A);
  const SpProxy<T2> pb(X.B);

  const bool is_alias = pa.is_alias(out) || pb.is_alias(out);

  if (is_alias == false) {
    spglue_minus::apply_noalias(out, pa, pb);
  } else {
    SpMat<eT> tmp;

    spglue_minus::apply_noalias(tmp, pa, pb);

    out.steal_mem(tmp);
  }
}

template <typename eT, typename T1, typename T2>
inline void spglue_minus::apply_noalias(SpMat<eT>& out, const SpProxy<T1>& pa,
                                        const SpProxy<T2>& pb) {
  arma_debug_sigprint();

  arma_conform_assert_same_size(pa.get_n_rows(), pa.get_n_cols(), pb.get_n_rows(),
                                pb.get_n_cols(), "subtraction");

  if (pa.get_n_nonzero() == 0) {
    out = pb.Q;
    out *= eT(-1);
    return;
  }
  if (pb.get_n_nonzero() == 0) {
    out = pa.Q;
    return;
  }

  const uword max_n_nonzero = pa.get_n_nonzero() + pb.get_n_nonzero();

  // Resize memory to upper bound
  out.reserve(pa.get_n_rows(), pa.get_n_cols(), max_n_nonzero);

  // Now iterate across both matrices.
  typename SpProxy<T1>::const_iterator_type x_it = pa.begin();
  typename SpProxy<T1>::const_iterator_type x_end = pa.end();

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

  uword count = 0;

  while ((x_it != x_end) || (y_it != y_end)) {
    eT out_val;

    const uword x_it_row = x_it.row();
    const uword x_it_col = x_it.col();

    const uword y_it_row = y_it.row();
    const uword y_it_col = y_it.col();

    bool use_y_loc = false;

    if (x_it == y_it) {
      out_val = (*x_it) - (*y_it);

      ++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
      {
        out_val = (*x_it);

        ++x_it;
      } else {
        out_val = -(*y_it);  // take the negative

        ++y_it;

        use_y_loc = true;
      }
    }

    if (out_val != eT(0)) {
      access::rw(out.values[count]) = out_val;

      const uword out_row = (use_y_loc == false) ? x_it_row : y_it_row;
      const uword out_col = (use_y_loc == false) ? x_it_col : y_it_col;

      access::rw(out.row_indices[count]) = out_row;
      access::rw(out.col_ptrs[out_col + 1])++;
      ++count;
    }

    arma_check((count > max_n_nonzero),
               "internal error: spglue_minus::apply_noalias(): count > max_n_nonzero");
  }

  const uword out_n_cols = out.n_cols;

  uword* col_ptrs = access::rwp(out.col_ptrs);

  // Fix column pointers to be cumulative.
  for (uword c = 1; c <= out_n_cols; ++c) {
    col_ptrs[c] += col_ptrs[c - 1];
  }

  if (count < max_n_nonzero) {
    if (count <= (max_n_nonzero / 2)) {
      out.mem_resize(count);
    } else {
      // quick resize without reallocating memory and copying data
      access::rw(out.n_nonzero) = count;
      access::rw(out.values[count]) = eT(0);
      access::rw(out.row_indices[count]) = uword(0);
    }
  }
}

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

  const SpProxy<SpMat<eT> > pa(A);
  const SpProxy<SpMat<eT> > pb(B);

  spglue_minus::apply_noalias(out, pa, pb);
}

//

template <typename T1, typename T2>
inline void spglue_minus_mixed::apply(
    SpMat<typename eT_promoter<T1, T2>::eT>& out,
    const mtSpGlue<typename eT_promoter<T1, T2>::eT, T1, T2, spglue_minus_mixed>& expr) {
  arma_debug_sigprint();

  typedef typename T1::elem_type eT1;
  typedef typename T2::elem_type eT2;

  typedef typename promote_type<eT1, eT2>::result out_eT;

  promote_type<eT1, eT2>::check();

  if ((is_same_type<eT1, out_eT>::no) && (is_same_type<eT2, out_eT>::yes)) {
    // upgrade T1

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

    const SpMat<eT1>& A = UA.M;
    const SpMat<eT2>& B = UB.M;

    SpMat<out_eT> AA(arma_layout_indicator(), A);

    for (uword i = 0; i < A.n_nonzero; ++i) {
      access::rw(AA.values[i]) = out_eT(A.values[i]);
    }

    const SpMat<out_eT>& BB = reinterpret_cast<const SpMat<out_eT>&>(B);

    out = AA - BB;
  } else if ((is_same_type<eT1, out_eT>::yes) && (is_same_type<eT2, out_eT>::no)) {
    // upgrade T2

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

    const SpMat<eT1>& A = UA.M;
    const SpMat<eT2>& B = UB.M;

    const SpMat<out_eT>& AA = reinterpret_cast<const SpMat<out_eT>&>(A);

    SpMat<out_eT> BB(arma_layout_indicator(), B);

    for (uword i = 0; i < B.n_nonzero; ++i) {
      access::rw(BB.values[i]) = out_eT(B.values[i]);
    }

    out = AA - BB;
  } else {
    // upgrade T1 and T2

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

    const SpMat<eT1>& A = UA.M;
    const SpMat<eT2>& B = UB.M;

    SpMat<out_eT> AA(arma_layout_indicator(), A);
    SpMat<out_eT> BB(arma_layout_indicator(), B);

    for (uword i = 0; i < A.n_nonzero; ++i) {
      access::rw(AA.values[i]) = out_eT(A.values[i]);
    }
    for (uword i = 0; i < B.n_nonzero; ++i) {
      access::rw(BB.values[i]) = out_eT(B.values[i]);
    }

    out = AA - BB;
  }
}

template <typename T1, typename T2>
inline void spglue_minus_mixed::sparse_minus_dense(
    Mat<typename promote_type<typename T1::elem_type, typename T2::elem_type>::result>&
        out,
    const T1& X, const T2& Y) {
  arma_debug_sigprint();

  typedef typename T1::elem_type eT1;
  typedef typename T2::elem_type eT2;

  typedef typename promote_type<eT1, eT2>::result out_eT;

  promote_type<eT1, eT2>::check();

  const quasi_unwrap<T2> UB(Y);
  const Mat<eT2>& B = UB.M;

  const uword B_n_elem = B.n_elem;
  const eT2* B_mem = B.memptr();

  out.set_size(B.n_rows, B.n_cols);

  out_eT* out_mem = out.memptr();

  for (uword i = 0; i < B_n_elem; ++i) {
    out_mem[i] = out_eT(-B_mem[i]);
  }

  const SpProxy<T1> pa(X);

  arma_conform_assert_same_size(pa.get_n_rows(), pa.get_n_cols(), out.n_rows, out.n_cols,
                                "subtraction");

  typename SpProxy<T1>::const_iterator_type it = pa.begin();
  typename SpProxy<T1>::const_iterator_type it_end = pa.end();

  while (it != it_end) {
    out.at(it.row(), it.col()) += out_eT(*it);
    ++it;
  }
}

template <typename T1, typename T2>
inline void spglue_minus_mixed::dense_minus_sparse(
    Mat<typename promote_type<typename T1::elem_type, typename T2::elem_type>::result>&
        out,
    const T1& X, const T2& Y) {
  arma_debug_sigprint();

  typedef typename T1::elem_type eT1;
  typedef typename T2::elem_type eT2;

  typedef typename promote_type<eT1, eT2>::result out_eT;

  promote_type<eT1, eT2>::check();

  if (is_same_type<eT1, out_eT>::no) {
    out = conv_to<Mat<out_eT> >::from(X);
  } else {
    const quasi_unwrap<T1> UA(X);

    const Mat<eT1>& A = UA.M;

    out = reinterpret_cast<const Mat<out_eT>&>(A);
  }

  const SpProxy<T2> pb(Y);

  arma_conform_assert_same_size(out.n_rows, out.n_cols, pb.get_n_rows(), pb.get_n_cols(),
                                "subtraction");

  typename SpProxy<T2>::const_iterator_type it = pb.begin();
  typename SpProxy<T2>::const_iterator_type it_end = pb.end();

  while (it != it_end) {
    out.at(it.row(), it.col()) -= out_eT(*it);
    ++it;
  }
}

//! @}
