// 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 spop_shift
//! @{

template <typename eT>
inline void spop_shift::apply_noalias(SpMat<eT>& out, const SpMat<eT>& X, const uword len,
                                      const uword neg, const uword dim) {
  arma_debug_sigprint();

  arma_conform_check_bounds(((dim == 0) && (len >= X.n_rows)),
                            "shift(): shift amount out of bounds");
  arma_conform_check_bounds(((dim == 1) && (len >= X.n_cols)),
                            "shift(): shift amount out of bounds");

  if (X.n_nonzero == 0) {
    out.zeros(X.n_rows, X.n_cols);
    return;
  }

  if (len == 0) {
    out = X;
    return;
  }

  typename SpMat<eT>::const_iterator it = X.begin();
  typename SpMat<eT>::const_iterator it_end = X.end();

  Mat<uword> locs(2, X.n_nonzero, arma_nozeros_indicator());

  uword* locs_mem = locs.memptr();

  if (dim == 0) {
    const uword X_row_threshold = X.n_rows - len;

    for (; it != it_end; ++it) {
      const uword X_row = it.row();
      uword Y_row = 0;

      if (neg == 0) {
        Y_row = (X_row < X_row_threshold) ? (X_row + len) : (X_row - X_row_threshold);
      } else if (neg == 1) {
        Y_row = (X_row >= len) ? (X_row - len) : (X_row + X_row_threshold);
      }

      locs_mem[0] = Y_row;
      locs_mem[1] = it.col();

      locs_mem += 2;
    }
  } else if (dim == 1) {
    const uword X_col_threshold = X.n_cols - len;

    for (; it != it_end; ++it) {
      const uword X_col = it.col();
      uword Y_col = 0;

      if (neg == 0) {
        Y_col = (X_col < X_col_threshold) ? (X_col + len) : (X_col - X_col_threshold);
      } else if (neg == 1) {
        Y_col = (X_col >= len) ? (X_col - len) : (X_col + X_col_threshold);
      }

      locs_mem[0] = it.row();
      locs_mem[1] = Y_col;

      locs_mem += 2;
    }
  }

  const Col<eT> vals(const_cast<eT*>(X.values), X.n_nonzero, false);

  SpMat<eT> Y(locs, vals, X.n_rows, X.n_cols, true, false);

  out.steal_mem(Y);
}

//! @}
