/*################################################################################
  ##
  ##   Copyright (C) 2016-2024 Keith O'Hara
  ##
  ##   This file is part of the GCE-Math C++ library.
  ##
  ##   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.
  ##
  ################################################################################*/

#ifndef _gcem_fmod_HPP
#define _gcem_fmod_HPP

#include <cmath>
#include <type_traits>

namespace gcem
{

namespace internal
{

template<typename T>
constexpr
T
fmod_check(const T x, const T y)
noexcept
{
    return( // NaN check
            any_nan(x, y) ? \
                GCLIM<T>::quiet_NaN() :
            // +/- infinite
            !all_finite(x, y) ? \
                GCLIM<T>::quiet_NaN() :
            // else
                x - trunc(x/y)*y );
}

template<typename T1, typename T2, typename TC = common_return_t<T1,T2>>
constexpr
TC
fmod_type_check(const T1 x, const T2 y)
noexcept
{
    return fmod_check(static_cast<TC>(x),static_cast<TC>(y));
}

}

/**
 * Compile-time remainder of division function
 * @param x a real-valued input.
 * @param y a real-valued input.
 * @return computes the floating-point remainder of \f$ x / y \f$ (rounded towards zero) using \f[ \text{fmod}(x,y) = x - \text{trunc}(x/y) \times y \f] 
 */

template<typename T1, typename T2>
constexpr
common_return_t<T1,T2>
fmod(const T1 x, const T2 y)
noexcept
{
  if (std::is_constant_evaluated()) {
    return internal::fmod_type_check(x,y);
  } else {
    return std::fmod(x, y);
  }
}

}

#endif
