// 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_rcond
//! @{

template <typename T1>
inline typename T1::pod_type op_rcond::apply(const Base<typename T1::elem_type, T1>& X) {
  arma_extra_debug_sigprint();

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

  if (strip_trimat<T1>::do_trimat) {
    const strip_trimat<T1> S(X.get_ref());

    const quasi_unwrap<typename strip_trimat<T1>::stored_type> U(S.M);

    arma_debug_check((U.M.is_square() == false), "rcond(): matrix must be square sized");

    const uword layout = (S.do_triu) ? uword(0) : uword(1);

    return auxlib::rcond_trimat(U.M, layout);
  }

  Mat<eT> A = X.get_ref();

  arma_debug_check((A.is_square() == false), "rcond(): matrix must be square sized");

  if (A.is_empty()) {
    return Datum<T>::inf;
  }

  if (is_op_diagmat<T1>::value || A.is_diagmat()) {
    arma_extra_debug_print("op_rcond::apply(): detected diagonal matrix");

    const eT* colmem = A.memptr();
    const uword N = A.n_rows;

    T abs_min = Datum<T>::inf;
    T abs_max = T(0);

    for (uword i = 0; i < N; ++i) {
      const T abs_val = std::abs(colmem[i]);

      abs_min = (abs_val < abs_min) ? abs_val : abs_min;
      abs_max = (abs_val > abs_max) ? abs_val : abs_max;

      colmem += N;
    }

    if ((abs_min == T(0)) || (abs_max == T(0))) {
      return T(0);
    }

    return T(abs_min / abs_max);
  }

  const bool is_triu = trimat_helper::is_triu(A);
  const bool is_tril = (is_triu) ? false : trimat_helper::is_tril(A);

  if (is_triu || is_tril) {
    const uword layout = (is_triu) ? uword(0) : uword(1);

    return auxlib::rcond_trimat(A, layout);
  }

  const bool try_sympd =
      arma_config::optimise_sym &&
      (auxlib::crippled_lapack(A) ? false : sym_helper::guess_sympd(A));

  if (try_sympd) {
    arma_extra_debug_print("op_rcond::apply(): attempting sympd optimisation");

    bool calc_ok = false;

    const T out_val = auxlib::rcond_sympd(A, calc_ok);

    if (calc_ok) {
      return out_val;
    }

    arma_extra_debug_print("op_rcond::apply(): sympd optimisation failed");

    // auxlib::rcond_sympd() may have failed because A isn't really sympd
    // restore A, as auxlib::rcond_sympd() may have destroyed it
    A = X.get_ref();
    // fallthrough to the next return statement
  }

  return auxlib::rcond(A);
}

//! @}
