// 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_eig_sym
//! @{

//! Eigenvalues of real/complex symmetric/hermitian matrix X
template <typename T1>
inline typename enable_if2<is_supported_blas_type<typename T1::elem_type>::value,
                           bool>::result
eig_sym(Col<typename T1::pod_type>& eigval, const Base<typename T1::elem_type, T1>& X) {
  arma_debug_sigprint();

  typedef typename T1::elem_type eT;

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

  const bool status = auxlib::eig_sym(eigval, A);

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

  return status;
}

//! Eigenvalues of real/complex symmetric/hermitian matrix X
template <typename T1>
arma_warn_unused inline
    typename enable_if2<is_supported_blas_type<typename T1::elem_type>::value,
                        Col<typename T1::pod_type> >::result
    eig_sym(const Base<typename T1::elem_type, T1>& X) {
  arma_debug_sigprint();

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

  Col<T> eigval;
  Mat<eT> A(X.get_ref());

  const bool status = auxlib::eig_sym(eigval, A);

  if (status == false) {
    eigval.reset();
    arma_stop_runtime_error("eig_sym(): decomposition failed");
  }

  return eigval;
}

//! internal helper function
template <typename eT>
inline bool eig_sym_helper(Col<typename get_pod_type<eT>::result>& eigval,
                           Mat<eT>& eigvec, const Mat<eT>& X, const char method_sig,
                           const char* caller_sig) {
  arma_debug_sigprint();

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

  bool status = false;

  if (method_sig == 'd') {
    status = auxlib::eig_sym_dc(eigval, eigvec, X);
  }

  if (status == false) {
    status = auxlib::eig_sym(eigval, eigvec, X);
  }

  return status;
}

//! Eigenvalues and eigenvectors of real/complex symmetric/hermitian matrix X
template <typename T1>
inline typename enable_if2<is_supported_blas_type<typename T1::elem_type>::value,
                           bool>::result
eig_sym(Col<typename T1::pod_type>& eigval, Mat<typename T1::elem_type>& eigvec,
        const Base<typename T1::elem_type, T1>& expr, const char* method = "dc") {
  arma_debug_sigprint();

  typedef typename T1::elem_type eT;

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

  arma_conform_check(((sig != 's') && (sig != 'd')),
                     "eig_sym(): unknown method specified");
  arma_conform_check(void_ptr(&eigval) == void_ptr(&eigvec),
                     "eig_sym(): parameter 'eigval' is an alias of parameter 'eigvec'");

  const quasi_unwrap<T1> U(expr.get_ref());

  const bool is_alias = U.is_alias(eigvec);

  Mat<eT> eigvec_tmp;
  Mat<eT>& eigvec_out = (is_alias == false) ? eigvec : eigvec_tmp;

  const bool status = eig_sym_helper(eigval, eigvec_out, U.M, sig, "eig_sym()");

  if (status == false) {
    eigval.soft_reset();
    eigvec.soft_reset();
    arma_warn(3, "eig_sym(): decomposition failed");
  } else {
    if (is_alias) {
      eigvec.steal_mem(eigvec_tmp);
    }
  }

  return status;
}

//! @}
