// 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_chol
//! @{

template <typename T1>
arma_warn_unused inline
    typename enable_if2<is_supported_blas_type<typename T1::elem_type>::value,
                        const Op<T1, op_chol> >::result
    chol(const Base<typename T1::elem_type, T1>& X, const char* layout = "upper") {
  arma_debug_sigprint();

  const char sig = (layout != nullptr) ? layout[0] : char(0);

  arma_conform_check(((sig != 'u') && (sig != 'l')),
                     "chol(): layout must be \"upper\" or \"lower\"");

  return Op<T1, op_chol>(X.get_ref(), ((sig == 'u') ? 0 : 1), 0);
}

template <typename T1>
inline typename enable_if2<is_supported_blas_type<typename T1::elem_type>::value,
                           bool>::result
chol(Mat<typename T1::elem_type>& out, const Base<typename T1::elem_type, T1>& X,
     const char* layout = "upper") {
  arma_debug_sigprint();

  const char sig = (layout != nullptr) ? layout[0] : char(0);

  arma_conform_check(((sig != 'u') && (sig != 'l')),
                     "chol(): layout must be \"upper\" or \"lower\"");

  const bool status = op_chol::apply_direct(out, X.get_ref(), ((sig == 'u') ? 0 : 1));

  if (status == false) {
    out.soft_reset();
    arma_warn(3, "chol(): decomposition failed");
  }

  return status;
}

template <typename T1>
inline typename enable_if2<is_supported_blas_type<typename T1::elem_type>::value,
                           bool>::result
chol(Mat<typename T1::elem_type>& out, Mat<uword>& P,
     const Base<typename T1::elem_type, T1>& X, const char* layout = "upper",
     const char* P_mode = "matrix") {
  arma_debug_sigprint();

  typedef typename T1::elem_type eT;

  const char sig_layout = (layout != nullptr) ? layout[0] : char(0);
  const char sig_P_mode = (P_mode != nullptr) ? P_mode[0] : char(0);

  arma_conform_check(((sig_layout != 'u') && (sig_layout != 'l')),
                     "chol(): argument 'layout' must be \"upper\" or \"lower\"");
  arma_conform_check(((sig_P_mode != 'm') && (sig_P_mode != 'v')),
                     "chol(): argument 'P_mode' must be \"vector\" or \"matrix\"");

  out = X.get_ref();

  arma_conform_check((out.is_square() == false),
                     "chol(): given matrix must be square sized",
                     [&]() { out.soft_reset(); });

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

  if ((arma_config::check_conform) && (auxlib::rudimentary_sym_check(out) == false)) {
    if (is_cx<eT>::no) {
      arma_warn(1, "chol(): given matrix is not symmetric");
    }
    if (is_cx<eT>::yes) {
      arma_warn(1, "chol(): given matrix is not hermitian");
    }
  }

  bool status = false;

  if (sig_P_mode == 'v') {
    status = auxlib::chol_pivot(out, P, ((sig_layout == 'u') ? 0 : 1));
  } else if (sig_P_mode == 'm') {
    Mat<uword> P_vec;

    status = auxlib::chol_pivot(out, P_vec, ((sig_layout == 'u') ? 0 : 1));

    if (status) {
      // construct P

      const uword N = P_vec.n_rows;

      P.zeros(N, N);

      for (uword i = 0; i < N; ++i) {
        P.at(P_vec[i], i) = uword(1);
      }
    }
  }

  if (status == false) {
    out.soft_reset();
    P.soft_reset();
    arma_warn(3, "chol(): decomposition failed");
  }

  return status;
}

//! @}
