// 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_orth_null
//! @{

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

  typedef typename T1::pod_type T;

  const T tol = access::tmp_real(expr.aux);

  const bool status = op_orth::apply_direct(out, expr.m, tol);

  if (status == false) {
    out.soft_reset();
    arma_stop_runtime_error("orth(): svd failed");
  }
}

template <typename T1>
inline bool op_orth::apply_direct(Mat<typename T1::elem_type>& out,
                                  const Base<typename T1::elem_type, T1>& expr,
                                  typename T1::pod_type tol) {
  arma_debug_sigprint();

  typedef typename T1::elem_type eT;
  typedef typename T1::pod_type T;

  arma_conform_check((tol < T(0)), "orth(): tolerance must be >= 0");

  Mat<eT> A(expr.get_ref());

  Mat<eT> U;
  Col<T> s;
  Mat<eT> V;

  const bool status = auxlib::svd_dc(U, s, V, A);

  V.reset();

  if (status == false) {
    return false;
  }

  if (s.is_empty()) {
    out.reset();
    return true;
  }

  const uword s_n_elem = s.n_elem;
  const T* s_mem = s.memptr();

  // set tolerance to default if it hasn't been specified
  if (tol == T(0)) {
    tol = (std::max)(A.n_rows, A.n_cols) * s_mem[0] * std::numeric_limits<T>::epsilon();
  }

  uword count = 0;

  for (uword i = 0; i < s_n_elem; ++i) {
    count += (s_mem[i] > tol) ? uword(1) : uword(0);
  }

  if (count > 0) {
    out = U.head_cols(count);  // out *= eT(-1);
  } else {
    out.set_size(A.n_rows, 0);
  }

  return true;
}

//

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

  typedef typename T1::pod_type T;

  const T tol = access::tmp_real(expr.aux);

  const bool status = op_null::apply_direct(out, expr.m, tol);

  if (status == false) {
    out.soft_reset();
    arma_stop_runtime_error("null(): svd failed");
  }
}

template <typename T1>
inline bool op_null::apply_direct(Mat<typename T1::elem_type>& out,
                                  const Base<typename T1::elem_type, T1>& expr,
                                  typename T1::pod_type tol) {
  arma_debug_sigprint();

  typedef typename T1::elem_type eT;
  typedef typename T1::pod_type T;

  arma_conform_check((tol < T(0)), "null(): tolerance must be >= 0");

  Mat<eT> A(expr.get_ref());

  Mat<eT> U;
  Col<T> s;
  Mat<eT> V;

  const bool status = auxlib::svd_dc(U, s, V, A);

  U.reset();

  if (status == false) {
    return false;
  }

  if (s.is_empty()) {
    out.reset();
    return true;
  }

  const uword s_n_elem = s.n_elem;
  const T* s_mem = s.memptr();

  // set tolerance to default if it hasn't been specified
  if (tol == T(0)) {
    tol = (std::max)(A.n_rows, A.n_cols) * s_mem[0] * std::numeric_limits<T>::epsilon();
  }

  uword count = 0;

  for (uword i = 0; i < s_n_elem; ++i) {
    count += (s_mem[i] > tol) ? uword(1) : uword(0);
  }

  if (count < A.n_cols) {
    out = V.tail_cols(A.n_cols - count);

    const uword out_n_elem = out.n_elem;
    eT* out_mem = out.memptr();

    for (uword i = 0; i < out_n_elem; ++i) {
      if (std::abs(out_mem[i]) < std::numeric_limits<T>::epsilon()) {
        out_mem[i] = eT(0);
      }
    }
  } else {
    out.set_size(A.n_cols, 0);
  }

  return true;
}

//! @}
