// 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_fft
//! @{

#if defined(ARMA_USE_FFTW3)

template <typename cx_type, bool inverse>
class fft_engine_wrapper {
 public:
  static constexpr uword threshold = 512;

  fft_engine_kissfft<cx_type, inverse>* worker_kissfft = nullptr;
  fft_engine_fftw3<cx_type, inverse>* worker_fftw3 = nullptr;

  inline ~fft_engine_wrapper() {
    arma_debug_sigprint();

    if (worker_kissfft != nullptr) {
      delete worker_kissfft;
    }
    if (worker_fftw3 != nullptr) {
      delete worker_fftw3;
    }
  }

  inline fft_engine_wrapper(const uword N_samples, const uword N_exec) {
    arma_debug_sigprint();

    const bool use_fftw3 = N_samples >= (threshold / N_exec);

    worker_kissfft = (use_fftw3 == false)
                         ? new fft_engine_kissfft<cx_type, inverse>(N_samples)
                         : nullptr;
    worker_fftw3 =
        (use_fftw3 == true) ? new fft_engine_fftw3<cx_type, inverse>(N_samples) : nullptr;
  }

  inline void run(cx_type* Y, const cx_type* X) {
    arma_debug_sigprint();

    if (worker_kissfft != nullptr) {
      (*worker_kissfft).run(Y, X);
    } else if (worker_fftw3 != nullptr) {
      (*worker_fftw3).run(Y, X);
    }
  }
};

#endif

//
// op_fft_real

template <typename T1>
inline void op_fft_real::apply(
    Mat<std::complex<typename T1::pod_type> >& out,
    const mtOp<std::complex<typename T1::pod_type>, T1, op_fft_real>& in) {
  arma_debug_sigprint();

  typedef typename T1::pod_type in_eT;
  typedef typename std::complex<in_eT> out_eT;

  // no need to worry about aliasing, as we're going from a real object to complex
  // complex, which by definition cannot alias

  const quasi_unwrap<T1> U(in.m);
  const Mat<in_eT>& X = U.M;

  const uword n_rows = X.n_rows;
  const uword n_cols = X.n_cols;
  const uword n_elem = X.n_elem;

  const bool is_vec = ((n_rows == 1) || (n_cols == 1));

  const uword N_orig = (is_vec) ? n_elem : n_rows;
  const uword N_user = (in.aux_uword_b == 0) ? in.aux_uword_a : N_orig;

#if defined(ARMA_USE_FFTW3)
  const uword N_exec = (is_vec) ? uword(1) : n_cols;
  fft_engine_wrapper<out_eT, false> worker(N_user, N_exec);
#else
  fft_engine_kissfft<out_eT, false> worker(N_user);
#endif

  if (is_vec) {
    (n_cols == 1) ? out.set_size(N_user, 1) : out.set_size(1, N_user);

    if ((out.n_elem == 0) || (N_orig == 0)) {
      out.zeros();
      return;
    }

    if ((N_user == 1) && (N_orig >= 1)) {
      out[0] = out_eT(X[0]);
      return;
    }

    podarray<out_eT> data(N_user, arma_zeros_indicator());

    out_eT* data_mem = data.memptr();
    const in_eT* X_mem = X.memptr();

    const uword N = (std::min)(N_user, N_orig);

    for (uword i = 0; i < N; ++i) {
      data_mem[i].real(X_mem[i]);
    }

    worker.run(out.memptr(), data_mem);
  } else {
    // process each column seperately

    out.set_size(N_user, n_cols);

    if ((out.n_elem == 0) || (N_orig == 0)) {
      out.zeros();
      return;
    }

    if ((N_user == 1) && (N_orig >= 1)) {
      for (uword col = 0; col < n_cols; ++col) {
        out.at(0, col).real(X.at(0, col));
      }

      return;
    }

    podarray<out_eT> data(N_user, arma_zeros_indicator());

    out_eT* data_mem = data.memptr();

    const uword N = (std::min)(N_user, N_orig);

    for (uword col = 0; col < n_cols; ++col) {
      for (uword i = 0; i < N; ++i) {
        data_mem[i].real(X.at(i, col));
      }

      worker.run(out.colptr(col), data_mem);
    }
  }
}

//
// op_fft_cx

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

  typedef typename T1::elem_type eT;

  const quasi_unwrap<T1> U(in.m);

  if (U.is_alias(out)) {
    Mat<eT> tmp;

    op_fft_cx::apply_noalias<eT, false>(tmp, U.M, in.aux_uword_a, in.aux_uword_b);

    out.steal_mem(tmp);
  } else {
    op_fft_cx::apply_noalias<eT, false>(out, U.M, in.aux_uword_a, in.aux_uword_b);
  }
}

template <typename eT, bool inverse>
inline void op_fft_cx::apply_noalias(Mat<eT>& out, const Mat<eT>& X, const uword a,
                                     const uword b) {
  arma_debug_sigprint();

  const uword n_rows = X.n_rows;
  const uword n_cols = X.n_cols;
  const uword n_elem = X.n_elem;

  const bool is_vec = ((n_rows == 1) || (n_cols == 1));

  const uword N_orig = (is_vec) ? n_elem : n_rows;
  const uword N_user = (b == 0) ? a : N_orig;

#if defined(ARMA_USE_FFTW3)
  const uword N_exec = (is_vec) ? uword(1) : n_cols;
  fft_engine_wrapper<eT, inverse> worker(N_user, N_exec);
#else
  fft_engine_kissfft<eT, inverse> worker(N_user);
#endif

  if (is_vec) {
    (n_cols == 1) ? out.set_size(N_user, 1) : out.set_size(1, N_user);

    if ((out.n_elem == 0) || (N_orig == 0)) {
      out.zeros();
      return;
    }

    if ((N_user == 1) && (N_orig >= 1)) {
      out[0] = X[0];
      return;
    }

    if (N_user > N_orig) {
      podarray<eT> data(N_user);

      eT* data_mem = data.memptr();

      arrayops::fill_zeros(&data_mem[N_orig], (N_user - N_orig));

      arrayops::copy(data_mem, X.memptr(), (std::min)(N_user, N_orig));

      worker.run(out.memptr(), data_mem);
    } else {
      worker.run(out.memptr(), X.memptr());
    }
  } else {
    // process each column seperately

    out.set_size(N_user, n_cols);

    if ((out.n_elem == 0) || (N_orig == 0)) {
      out.zeros();
      return;
    }

    if ((N_user == 1) && (N_orig >= 1)) {
      for (uword col = 0; col < n_cols; ++col) {
        out.at(0, col) = X.at(0, col);
      }

      return;
    }

    if (N_user > N_orig) {
      podarray<eT> data(N_user);

      eT* data_mem = data.memptr();

      arrayops::fill_zeros(&data_mem[N_orig], (N_user - N_orig));

      const uword N = (std::min)(N_user, N_orig);

      for (uword col = 0; col < n_cols; ++col) {
        arrayops::copy(data_mem, X.colptr(col), N);

        worker.run(out.colptr(col), data_mem);
      }
    } else {
      for (uword col = 0; col < n_cols; ++col) {
        worker.run(out.colptr(col), X.colptr(col));
      }
    }
  }

  // correct the scaling for the inverse transform
  if (inverse) {
    typedef typename get_pod_type<eT>::result T;

    const T k = T(1) / T(N_user);

    eT* out_mem = out.memptr();

    const uword out_n_elem = out.n_elem;

    for (uword i = 0; i < out_n_elem; ++i) {
      out_mem[i] *= k;
    }
  }
}

//
// op_ifft_cx

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

  typedef typename T1::elem_type eT;

  const quasi_unwrap<T1> U(in.m);

  if (U.is_alias(out)) {
    Mat<eT> tmp;

    op_fft_cx::apply_noalias<eT, true>(tmp, U.M, in.aux_uword_a, in.aux_uword_b);

    out.steal_mem(tmp);
  } else {
    op_fft_cx::apply_noalias<eT, true>(out, U.M, in.aux_uword_a, in.aux_uword_b);
  }
}

//! @}
