///////////////////////////////////////////////////////////////////////////////
//
// Copyright (c) 2015 Microsoft Corporation. All rights reserved.
//
// This code is licensed under the MIT License (MIT).
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
//
///////////////////////////////////////////////////////////////////////////////

#ifndef GSL_NARROW_H
#define GSL_NARROW_H
#include "./assert"  // for GSL_SUPPRESS
#include "./util"    // for narrow_cast
#include <exception> // for std::exception
namespace gsl
{
namespace details
{
    template <class T, class U>
    constexpr bool static_cast_is_defined(U u, /*is_floating_point_to_integral=*/std::true_type)
    {
        if (std::is_same<typename std::remove_cv<T>::type, bool>::value) { return true; }

        U upper_bound{1};
        for (int i = 0; i < std::numeric_limits<T>::digits; i++)
        {
            upper_bound *= std::numeric_limits<T>::radix;
        }

        if (u >= U{}) { return u < upper_bound; }
        if (!std::is_signed<T>::value) { return u > U{-1}; }

        return u + upper_bound > U{-1};
    }

    template <class T, class U>
    constexpr bool static_cast_is_defined(U, /*is_floating_point_to_integral=*/std::false_type)
    {
        return true;
    }
} // namespace details

struct narrowing_error : public std::exception
{
    const char* what() const noexcept override { return "narrowing_error"; }
};

// narrow() : a checked version of narrow_cast() that throws if the cast changed the value
template <class T, class U, typename std::enable_if<std::is_arithmetic<T>::value>::type* = nullptr>
GSL_SUPPRESS(type.1) constexpr T narrow(U u)
{
    constexpr const bool is_different_signedness =
        (std::is_signed<T>::value != std::is_signed<U>::value);

    using is_floating_point_to_integral =
        std::integral_constant<bool,
                               std::is_integral<T>::value && std::is_floating_point<U>::value>;
    if (!details::static_cast_is_defined<T, U>(u, is_floating_point_to_integral{}))
    {
        throw narrowing_error{};
    }

    GSL_SUPPRESS(es.103) // don't overflow
    GSL_SUPPRESS(es.104) // don't underflow
    const T t = narrow_cast<T>(u);

#if defined(__clang__) || defined(__GNUC__)
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wfloat-equal"
#endif
    // Note: NaN will always throw, since NaN != NaN
    if (static_cast<U>(t) != u || (is_different_signedness && ((t < T{}) != (u < U{}))))
    {
        throw narrowing_error{};
    }
#if defined(__clang__) || defined(__GNUC__)
#pragma GCC diagnostic pop
#endif

    return t;
}

template <class T, class U, typename std::enable_if<!std::is_arithmetic<T>::value>::type* = nullptr>
GSL_SUPPRESS(type.1) constexpr T narrow(U u)
{
    const T t = narrow_cast<T>(u);

    if (static_cast<U>(t) != u) { throw narrowing_error{}; }

    return t;
}
} // namespace gsl
#endif // GSL_NARROW_H