// 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_regspace
//! @{

template <typename eT>
inline void internal_regspace_default_delta(Mat<eT>& x,
                                            const typename Mat<eT>::pod_type start,
                                            const typename Mat<eT>::pod_type end) {
  arma_debug_sigprint();

  typedef typename Mat<eT>::pod_type T;

  const bool ascend = (start <= end);

  const uword N = uword(1) + uword((ascend) ? (end - start) : (start - end));

  x.set_size(N);

  eT* x_mem = x.memptr();

  if (ascend) {
    for (uword i = 0; i < N; ++i) {
      x_mem[i] = eT(start + T(i));
    }
  } else {
    for (uword i = 0; i < N; ++i) {
      x_mem[i] = eT(start - T(i));
    }
  }
}

template <typename eT, typename sT>
inline typename enable_if2<(is_signed<sT>::value == true), void>::result
internal_regspace_var_delta(Mat<eT>& x, const typename Mat<eT>::pod_type start,
                            const sT delta, const typename Mat<eT>::pod_type end) {
  arma_debug_sigprint();
  arma_debug_print("internal_regspace_var_delta(): signed version");

  typedef typename Mat<eT>::pod_type T;

  if (((start < end) && (delta < sT(0))) || ((start > end) && (delta > sT(0))) ||
      (delta == sT(0))) {
    return;
  }

  const bool ascend = (start <= end);

  const T inc = (delta < sT(0)) ? T(-delta) : T(delta);

  const T M = ((ascend) ? T(end - start) : T(start - end)) / T(inc);

  const uword N =
      uword(1) + ((is_non_integral<T>::value) ? uword(std::floor(double(M))) : uword(M));

  x.set_size(N);

  eT* x_mem = x.memptr();

  if (ascend) {
    for (uword i = 0; i < N; ++i) {
      x_mem[i] = eT(start + T(i * inc));
    }
  } else {
    for (uword i = 0; i < N; ++i) {
      x_mem[i] = eT(start - T(i * inc));
    }
  }
}

template <typename eT, typename uT>
inline typename enable_if2<(is_signed<uT>::value == false), void>::result
internal_regspace_var_delta(Mat<eT>& x, const typename Mat<eT>::pod_type start,
                            const uT delta, const typename Mat<eT>::pod_type end) {
  arma_debug_sigprint();
  arma_debug_print("internal_regspace_var_delta(): unsigned version");

  typedef typename Mat<eT>::pod_type T;

  if (((start > end) && (delta > uT(0))) || (delta == uT(0))) {
    return;
  }

  const bool ascend = (start <= end);

  const T inc = T(delta);

  const T M = ((ascend) ? T(end - start) : T(start - end)) / T(inc);

  const uword N =
      uword(1) + ((is_non_integral<T>::value) ? uword(std::floor(double(M))) : uword(M));

  x.set_size(N);

  eT* x_mem = x.memptr();

  if (ascend) {
    for (uword i = 0; i < N; ++i) {
      x_mem[i] = eT(start + T(i * inc));
    }
  } else {
    for (uword i = 0; i < N; ++i) {
      x_mem[i] = eT(start - T(i * inc));
    }
  }
}

template <typename vec_type, typename sT>
inline typename enable_if2<is_Mat<vec_type>::value && (is_signed<sT>::value == true),
                           vec_type>::result
regspace(const typename vec_type::pod_type start, const sT delta,
         const typename vec_type::pod_type end) {
  arma_debug_sigprint();
  arma_debug_print("regspace(): signed version");

  vec_type x;

  if (((delta == sT(+1)) && (start <= end)) || ((delta == sT(-1)) && (start > end))) {
    internal_regspace_default_delta(x, start, end);
  } else {
    internal_regspace_var_delta(x, start, delta, end);
  }

  if (x.n_elem == 0) {
    if (is_Mat_only<vec_type>::value) {
      x.set_size(1, 0);
    }
  }

  return x;
}

template <typename vec_type, typename uT>
inline typename enable_if2<is_Mat<vec_type>::value && (is_signed<uT>::value == false),
                           vec_type>::result
regspace(const typename vec_type::pod_type start, const uT delta,
         const typename vec_type::pod_type end) {
  arma_debug_sigprint();
  arma_debug_print("regspace(): unsigned version");

  vec_type x;

  if ((delta == uT(+1)) && (start <= end)) {
    internal_regspace_default_delta(x, start, end);
  } else {
    internal_regspace_var_delta(x, start, delta, end);
  }

  if (x.n_elem == 0) {
    if (is_Mat_only<vec_type>::value) {
      x.set_size(1, 0);
    }
  }

  return x;
}

template <typename vec_type>
arma_warn_unused inline typename enable_if2<is_Mat<vec_type>::value, vec_type>::result
regspace(const typename vec_type::pod_type start, const typename vec_type::pod_type end) {
  arma_debug_sigprint();

  vec_type x;

  internal_regspace_default_delta(x, start, end);

  if (x.n_elem == 0) {
    if (is_Mat_only<vec_type>::value) {
      x.set_size(1, 0);
    }
  }

  return x;
}

arma_warn_unused inline vec regspace(const double start, const double delta,
                                     const double end) {
  arma_debug_sigprint();

  return regspace<vec>(start, delta, end);
}

arma_warn_unused inline vec regspace(const double start, const double end) {
  arma_debug_sigprint();

  return regspace<vec>(start, end);
}

//! @}
