// -*- C++ -*-
//===-------------------------- optional ----------------------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is dual licensed under the MIT and the University of Illinois Open
// Source Licenses. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

#ifndef SDL2PP_LIBCPP_OPTIONAL
#define SDL2PP_LIBCPP_OPTIONAL

#include <cassert>
#include <functional>
#include <initializer_list>
#include <new>
#include <stdexcept>
#include <type_traits>

namespace sdl2pp_libcpp_optional {

class bad_optional_access
    : public std::logic_error
{
public:
    explicit bad_optional_access(const std::string& __arg)
        : std::logic_error(__arg) {}
    explicit bad_optional_access(const char* __arg)
        : std::logic_error(__arg) {}
    bad_optional_access(const bad_optional_access&) noexcept = default;
    bad_optional_access& operator=(const bad_optional_access&) noexcept = default;
    // Get the key function ~bad_optional_access() into the dylib even if not compiling for C++1y
    virtual ~bad_optional_access() noexcept {}
};

struct in_place_t {};
constexpr in_place_t in_place{};

struct nullopt_t
{
    explicit constexpr nullopt_t(int) noexcept {}
};

constexpr nullopt_t nullopt{0};

template <class _Tp, bool = std::is_trivially_destructible<_Tp>::value>
class __optional_storage
{
protected:
    typedef _Tp value_type;
    union
    {
        char __null_state_;
        value_type __val_;
    };
    bool __engaged_ = false;

    ~__optional_storage()
    {
        if (__engaged_)
            __val_.~value_type();
    }

    constexpr __optional_storage() noexcept
        :  __null_state_('\0') {}

    __optional_storage(const __optional_storage& __x)
        :  __engaged_(__x.__engaged_)
        {
            if (__engaged_)
                ::new(std::addressof(__val_)) value_type(__x.__val_);
        }

    __optional_storage(__optional_storage&& __x)
                      noexcept(std::is_nothrow_move_constructible<value_type>::value)
        :  __engaged_(__x.__engaged_)
        {
            if (__engaged_)
                ::new(std::addressof(__val_)) value_type(std::move(__x.__val_));
        }

    constexpr __optional_storage(const value_type& __v)
        :  __val_(__v),
           __engaged_(true) {}

    constexpr __optional_storage(value_type&& __v)
        :  __val_(std::move(__v)),
           __engaged_(true) {}

    template <class... _Args>
    constexpr
    explicit __optional_storage(in_place_t, _Args&&... __args)
       :  __val_(std::forward<_Args>(__args)...),
           __engaged_(true) {}
};

template <class _Tp>
class __optional_storage<_Tp, true>
{
protected:
    typedef _Tp value_type;
    union
    {
        char __null_state_;
        value_type __val_;
    };
    bool __engaged_ = false;

    constexpr __optional_storage() noexcept
        :  __null_state_('\0') {}

    __optional_storage(const __optional_storage& __x)
        :  __engaged_(__x.__engaged_)
        {
            if (__engaged_)
                ::new(std::addressof(__val_)) value_type(__x.__val_);
        }

    __optional_storage(__optional_storage&& __x)
                      noexcept(std::is_nothrow_move_constructible<value_type>::value)
        :  __engaged_(__x.__engaged_)
        {
            if (__engaged_)
                ::new(std::addressof(__val_)) value_type(std::move(__x.__val_));
        }

    constexpr __optional_storage(const value_type& __v)
        :  __val_(__v),
           __engaged_(true) {}

    constexpr __optional_storage(value_type&& __v)
        :  __val_(std::move(__v)),
           __engaged_(true) {}

    template <class... _Args>
    constexpr
    explicit __optional_storage(in_place_t, _Args&&... __args)
       :  __val_(std::forward<_Args>(__args)...),
           __engaged_(true) {}
};

template <class _Tp>
class optional
    : private __optional_storage<_Tp>
{
    typedef __optional_storage<_Tp> __base;
public:
    typedef _Tp value_type;

    static_assert(!std::is_reference<value_type>::value,
              "Instantiation of optional with a reference type is ill-formed.");
    static_assert(!std::is_same<typename std::remove_cv<value_type>::type, in_place_t>::value,
              "Instantiation of optional with a in_place_t type is ill-formed.");
    static_assert(!std::is_same<typename std::remove_cv<value_type>::type, nullopt_t>::value,
              "Instantiation of optional with a nullopt_t type is ill-formed.");
    static_assert(std::is_object<value_type>::value,
        "Instantiation of optional with a non-object type is undefined behavior.");
    static_assert(std::is_nothrow_destructible<value_type>::value,
        "Instantiation of optional with an object type that is not noexcept destructible is undefined behavior.");

    constexpr optional() noexcept {}
    optional(const optional&) = default;
    optional(optional&&) = default;
    ~optional() = default;
    constexpr optional(nullopt_t) noexcept {}
    constexpr optional(const value_type& __v)
        : __base(__v) {}
    constexpr optional(value_type&& __v)
        : __base(std::move(__v)) {}

    template <class... _Args,
              class = typename std::enable_if
                      <
                           std::is_constructible<value_type, _Args...>::value
                      >::type
             >
    constexpr
    explicit optional(in_place_t, _Args&&... __args)
        : __base(in_place, std::forward<_Args>(__args)...) {}

    template <class _Up, class... _Args,
              class = typename std::enable_if
                      <
                           std::is_constructible<value_type, std::initializer_list<_Up>&, _Args...>::value
                      >::type
             >
    constexpr
    explicit optional(in_place_t, std::initializer_list<_Up> __il, _Args&&... __args)
        : __base(in_place, __il, std::forward<_Args>(__args)...) {}

    optional& operator=(nullopt_t) noexcept
    {
        if (this->__engaged_)
        {
            this->__val_.~value_type();
            this->__engaged_ = false;
        }
        return *this;
    }

    optional&
    operator=(const optional& __opt)
    {
        if (this->__engaged_ == __opt.__engaged_)
        {
            if (this->__engaged_)
                this->__val_ = __opt.__val_;
        }
        else
        {
            if (this->__engaged_)
                this->__val_.~value_type();
            else
                ::new(std::addressof(this->__val_)) value_type(__opt.__val_);
            this->__engaged_ = __opt.__engaged_;
        }
        return *this;
    }

    optional&
    operator=(optional&& __opt)
        noexcept(std::is_nothrow_move_assignable<value_type>::value &&
                 std::is_nothrow_move_constructible<value_type>::value)
    {
        if (this->__engaged_ == __opt.__engaged_)
        {
            if (this->__engaged_)
                this->__val_ = std::move(__opt.__val_);
        }
        else
        {
            if (this->__engaged_)
                this->__val_.~value_type();
            else
                ::new(std::addressof(this->__val_)) value_type(std::move(__opt.__val_));
            this->__engaged_ = __opt.__engaged_;
        }
        return *this;
    }

    template <class _Up,
              class = typename std::enable_if
                      <
                          std::is_same<typename std::remove_reference<_Up>::type, value_type>::value &&
                          std::is_constructible<value_type, _Up>::value &&
                          std::is_assignable<value_type&, _Up>::value
                      >::type
             >
    optional&
    operator=(_Up&& __v)
    {
        if (this->__engaged_)
            this->__val_ = std::forward<_Up>(__v);
        else
        {
            ::new(std::addressof(this->__val_)) value_type(std::forward<_Up>(__v));
            this->__engaged_ = true;
        }
        return *this;
    }

    template <class... _Args,
              class = typename std::enable_if
                      <
                          std::is_constructible<value_type, _Args...>::value
                      >::type
             >
    void
    emplace(_Args&&... __args)
    {
        *this = nullopt;
        ::new(std::addressof(this->__val_)) value_type(std::forward<_Args>(__args)...);
        this->__engaged_ = true;
    }

    template <class _Up, class... _Args,
              class = typename std::enable_if
                      <
                          std::is_constructible<value_type, std::initializer_list<_Up>&, _Args...>::value
                      >::type
             >
    void
    emplace(std::initializer_list<_Up> __il, _Args&&... __args)
    {
        *this = nullopt;
        ::new(std::addressof(this->__val_)) value_type(__il, std::forward<_Args>(__args)...);
        this->__engaged_ = true;
    }

    void
    swap(optional& __opt)
        noexcept(std::is_nothrow_move_constructible<value_type>::value &&
                 noexcept(std::swap(std::declval<_Tp&>(), std::declval<_Tp&>())))
    {
        using std::swap;
        if (this->__engaged_ == __opt.__engaged_)
        {
            if (this->__engaged_)
                swap(this->__val_, __opt.__val_);
        }
        else
        {
            if (this->__engaged_)
            {
                ::new(std::addressof(__opt.__val_)) value_type(std::move(this->__val_));
                this->__val_.~value_type();
            }
            else
            {
                ::new(std::addressof(this->__val_)) value_type(std::move(__opt.__val_));
                __opt.__val_.~value_type();
            }
            swap(this->__engaged_, __opt.__engaged_);
        }
    }

    value_type const*
    operator->() const
    {
        assert(this->__engaged_); // "optional operator-> called for disengaged value");
        return std::addressof(this->__val_);
    }

    value_type*
    operator->()
    {
        assert(this->__engaged_); // "optional operator-> called for disengaged value");
        return std::addressof(this->__val_);
    }

    const value_type&
    operator*() const
    {
        assert(this->__engaged_); // "optional operator* called for disengaged value");
        return this->__val_;
    }

    value_type&
    operator*()
    {
        assert(this->__engaged_); // "optional operator* called for disengaged value");
        return this->__val_;
    }

    constexpr explicit operator bool() const noexcept {return this->__engaged_;}

    value_type const& value() const
    {
        if (!this->__engaged_)
            throw bad_optional_access("optional<T>::value: not engaged");
        return this->__val_;
    }

    value_type& value()
    {
        if (!this->__engaged_)
            throw bad_optional_access("optional<T>::value: not engaged");
        return this->__val_;
    }

    template <class _Up>
    constexpr value_type value_or(_Up&& __v) const&
    {
        static_assert(std::is_copy_constructible<value_type>::value,
                      "optional<T>::value_or: T must be copy constructible");
        static_assert(std::is_convertible<_Up, value_type>::value,
                      "optional<T>::value_or: U must be convertible to T");
        return this->__engaged_ ? this->__val_ :
                                  static_cast<value_type>(std::forward<_Up>(__v));
    }

    template <class _Up>
    value_type value_or(_Up&& __v) &&
    {
        static_assert(std::is_move_constructible<value_type>::value,
                      "optional<T>::value_or: T must be move constructible");
        static_assert(std::is_convertible<_Up, value_type>::value,
                      "optional<T>::value_or: U must be convertible to T");
        return this->__engaged_ ? std::move(this->__val_) :
                                  static_cast<value_type>(std::forward<_Up>(__v));
    }
};

template <class _Tp>
inline
bool
operator==(const optional<_Tp>& __x, const optional<_Tp>& __y)
{
    if (static_cast<bool>(__x) != static_cast<bool>(__y))
        return false;
    if (!static_cast<bool>(__x))
        return true;
    return *__x == *__y;
}

template <class _Tp>
inline
bool
operator<(const optional<_Tp>& __x, const optional<_Tp>& __y)
{
    if (!static_cast<bool>(__y))
        return false;
    if (!static_cast<bool>(__x))
        return true;
    return std::less<_Tp>{}(*__x, *__y);
}

template <class _Tp>
inline
constexpr
bool
operator==(const optional<_Tp>& __x, nullopt_t) noexcept
{
    return !static_cast<bool>(__x);
}

template <class _Tp>
inline
constexpr
bool
operator==(nullopt_t, const optional<_Tp>& __x) noexcept
{
    return !static_cast<bool>(__x);
}

template <class _Tp>
inline
constexpr
bool
operator<(const optional<_Tp>&, nullopt_t) noexcept
{
    return false;
}

template <class _Tp>
inline
constexpr
bool
operator<(nullopt_t, const optional<_Tp>& __x) noexcept
{
    return static_cast<bool>(__x);
}

template <class _Tp>
inline
constexpr
bool
operator==(const optional<_Tp>& __x, const _Tp& __v)
{
    return static_cast<bool>(__x) ? *__x == __v : false;
}

template <class _Tp>
inline
constexpr
bool
operator==(const _Tp& __v, const optional<_Tp>& __x)
{
    return static_cast<bool>(__x) ? *__x == __v : false;
}

template <class _Tp>
inline
constexpr
bool
operator<(const optional<_Tp>& __x, const _Tp& __v)
{
    return static_cast<bool>(__x) ? std::less<_Tp>{}(*__x, __v) : true;
}

template <class _Tp>
inline
constexpr
bool
operator<(const _Tp& __v, const optional<_Tp>& __x)
{
    return static_cast<bool>(__x) ? std::less<_Tp>{}(__v, *__x) : false;
}

template <class _Tp>
inline
void
swap(optional<_Tp>& __x, optional<_Tp>& __y) noexcept(noexcept(__x.swap(__y)))
{
    __x.swap(__y);
}

template <class _Tp>
inline
constexpr
optional<typename std::decay<_Tp>::type>
make_optional(_Tp&& __v)
{
    return optional<typename std::decay<_Tp>::type>(std::forward<_Tp>(__v));
}

} // namespace sdl2pp_libcpp_optional

namespace std {

template <class _Tp>
struct hash<sdl2pp_libcpp_optional::optional<_Tp> >
{
    typedef sdl2pp_libcpp_optional::optional<_Tp> argument_type;
    typedef size_t        result_type;

    result_type operator()(const argument_type& __opt) const noexcept
    {
        return static_cast<bool>(__opt) ? std::hash<_Tp>()(*__opt) : 0;
    }
};

}

#endif  // SDL2PP_LIBCPP_OPTIONAL