// 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_chi2rnd
//! @{

template <typename T1>
inline void op_chi2rnd::apply(Mat<typename T1::elem_type>& out,
                              const Op<T1, op_chi2rnd>& in) {
  arma_debug_sigprint();

  typedef typename T1::elem_type eT;

  const Proxy<T1> P(in.m);

  if (P.is_alias(out) == false) {
    op_chi2rnd::apply_noalias(out, P);
  } else {
    Mat<eT> tmp;

    op_chi2rnd::apply_noalias(tmp, P);

    out.steal_mem(tmp);
  }
}

template <typename T1>
inline void op_chi2rnd::apply_noalias(Mat<typename T1::elem_type>& out,
                                      const Proxy<T1>& P) {
  arma_debug_sigprint();

  typedef typename T1::elem_type eT;

  op_chi2rnd_varying_df<eT> generator;

  const uword n_rows = P.get_n_rows();
  const uword n_cols = P.get_n_cols();

  out.set_size(n_rows, n_cols);

  eT* out_mem = out.memptr();

  if (Proxy<T1>::use_at == false) {
    const uword N = P.get_n_elem();

    typename Proxy<T1>::ea_type Pea = P.get_ea();

    for (uword i = 0; i < N; ++i) {
      out_mem[i] = generator(Pea[i]);
    }
  } else {
    for (uword col = 0; col < n_cols; ++col)
      for (uword row = 0; row < n_rows; ++row) {
        (*out_mem) = generator(P.at(row, col));
        ++out_mem;
      }
  }
}

template <typename eT>
inline void op_chi2rnd::fill_constant_df(Mat<eT>& out, const eT df) {
  arma_debug_sigprint();

  if (df > eT(0)) {
    typedef std::mt19937_64 motor_type;
    typedef std::mt19937_64::result_type seed_type;
    typedef std::chi_squared_distribution<eT> distr_type;

    motor_type motor;
    motor.seed(seed_type(arma_rng::randi<int>()));
    distr_type distr(df);

    const uword N = out.n_elem;

    eT* out_mem = out.memptr();

    for (uword i = 0; i < N; ++i) {
      out_mem[i] = eT(distr(motor));
    }
  } else {
    out.fill(Datum<eT>::nan);
  }
}

//

template <typename eT>
inline op_chi2rnd_varying_df<eT>::~op_chi2rnd_varying_df() {
  arma_debug_sigprint();
}

template <typename eT>
inline op_chi2rnd_varying_df<eT>::op_chi2rnd_varying_df() {
  arma_debug_sigprint();

  typedef std::mt19937_64::result_type seed_type;

  motor.seed(seed_type(arma_rng::randi<int>()));
}

template <typename eT>
inline eT op_chi2rnd_varying_df<eT>::operator()(const eT df) {
  arma_debug_sigprint();

  // as C++11 doesn't seem to provide a way to explicitly set the parameter
  // of an existing chi_squared_distribution object,
  // we need to create a new object each time

  if (df > eT(0)) {
    std::chi_squared_distribution<eT> distr(df);

    return eT(distr(motor));
  } else {
    return Datum<eT>::nan;
  }
}

//! @}
