/** \file SRDelegate.hpp
 *
 * This is a C++11 implementation by janezz55(code.google) for the original "The Impossibly Fast C++ Delegates" authored by Sergey Ryazanov.
 *
 * This is a copy checkouted from https://code.google.com/p/cpppractice/source/browse/trunk/delegate.hpp on 2014/06/07.
 *   Last change in the chunk was r370 on Feb 9, 2014.
 *
 * The following modifications were added by Benjamin YanXiang Huang
 *  - replace light_ptr with std::shared_ptr
 *  - renamed src file
 *
 * Reference:
 *  - http://codereview.stackexchange.com/questions/14730/impossibly-fast-delegate-in-c11
 *  - http://www.codeproject.com/Articles/11015/The-Impossibly-Fast-C-Delegates
 *  - https://code.google.com/p/cpppractice/source/browse/trunk/delegate.hpp
*/

#pragma once
#ifndef SRDELEGATE_HPP
#define SRDELEGATE_HPP

#include <cassert>
#include <cstring>
#include <memory>
#include <new>
#include <type_traits>
#include <utility>

// VC work around for constexpr and noexcept: VC2013 and below do not support these 2 keywords
#if defined(_MSC_VER) && (_MSC_VER <= 1800)
#define constexpr const
#define noexcept throw()
#endif

namespace fastdelegate
{

template <typename T> class delegate;

template<class R, class ...A>
class delegate<R(A...)>
{
    using stub_ptr_type = R(*)(void *, A&&...);

    delegate(void * const o, stub_ptr_type const m) noexcept : object_ptr_(o), stub_ptr_(m) {}

public:
    delegate(void) = default;

    delegate(delegate const &) = default;

    delegate(delegate && d)
        : object_ptr_(d.object_ptr_), stub_ptr_(d.stub_ptr_), deleter_(d.deleter_), store_(d.store_), store_size_(d.store_size_)
    {
        d.object_ptr_ = nullptr;
        d.stub_ptr_   = nullptr;
        d.deleter_    = nullptr;
        d.store_      = nullptr;
        d.store_size_ = 0;
    }

    delegate(::std::nullptr_t const) noexcept : delegate() { }

    template <class C, typename = typename ::std::enable_if< ::std::is_class<C>::value, C>::type>
    explicit delegate(C const * const o) noexcept :
    object_ptr_(const_cast<C *>(o))
    {}

    template <class C, typename = typename ::std::enable_if< ::std::is_class<C> {}>::type>
    explicit delegate(C const & o) noexcept :
    object_ptr_(const_cast<C *>(&o))
    {}

    template <class C>
    delegate(C * const object_ptr, R(C::* const method_ptr)(A...))
    {
        *this = from(object_ptr, method_ptr);
    }

    template <class C>
    delegate(C * const object_ptr, R(C::* const method_ptr)(A...) const)
    {
        *this = from(object_ptr, method_ptr);
    }

    template <class C>
    delegate(C & object, R(C::* const method_ptr)(A...))
    {
        *this = from(object, method_ptr);
    }

    template <class C>
    delegate(C const & object, R(C::* const method_ptr)(A...) const)
    {
        *this = from(object, method_ptr);
    }

    template <
        typename T,
        typename = typename ::std::enable_if<!::std::is_same<delegate, typename ::std::decay<T>::type>::value>::type
    >
    delegate(T&& f)
        : store_(operator new(sizeof(typename ::std::decay<T>::type))
        , functor_deleter<typename ::std::decay<T>::type>)
        , store_size_(sizeof(typename ::std::decay<T>::type))
    {
        using functor_type = typename ::std::decay<T>::type;

        new(store_.get()) functor_type(::std::forward<T>(f));
        object_ptr_ = store_.get();

        stub_ptr_ = functor_stub<functor_type>;
        deleter_ = deleter_stub<functor_type>;
    }

    delegate & operator=(delegate const &) = default;

    delegate & operator=(delegate&& d)
    {
        object_ptr_   = d.object_ptr_;
        stub_ptr_     = d.stub_ptr_;
        deleter_      = d.deleter_;
        store_        = d.store_;
        store_size_   = d.store_size_;

        d.object_ptr_ = nullptr;
        d.stub_ptr_   = nullptr;
        d.deleter_    = nullptr;
        d.store_      = nullptr;
        d.store_size_ = 0;

        return *this;
    }

    template <class C>
    delegate & operator=(R(C::* const rhs)(A...))
    {
        return *this = from(static_cast<C *>(object_ptr_), rhs);
    }

    template <class C>
    delegate & operator=(R(C::* const rhs)(A...) const)
    {
        return *this = from(static_cast<C const *>(object_ptr_), rhs);
    }

    template <
        typename T
        , typename = typename ::std::enable_if<!::std::is_same<delegate, typename ::std::decay<T>::type>::value>::type
    >
    delegate & operator=(T&& f)
    {
        using functor_type = typename ::std::decay<T>::type;

        if ((sizeof(functor_type) > store_size_) || !store_.unique())
        {
            store_.reset(operator new(sizeof(functor_type)), functor_deleter<functor_type>);
            store_size_ = sizeof(functor_type);
        }
        else
            deleter_(store_.get());

        new(store_.get()) functor_type(::std::forward<T>(f));
        object_ptr_ = store_.get();

        stub_ptr_ = functor_stub<functor_type>;
        deleter_ = deleter_stub<functor_type>;

        return *this;
    }

    template <R(* const function_ptr)(A...)>
    static delegate from(void) noexcept
    {
        return { nullptr, function_stub<function_ptr> };
    }

    template <class C, R(C::* const method_ptr)(A...)>
    static delegate from(C * const object_ptr) noexcept
    {
        return { object_ptr, method_stub<C, method_ptr> };
    }

    template <class C, R(C::* const method_ptr)(A...) const>
    static delegate from(C const * const object_ptr) noexcept
    {
        return { const_cast<C *>(object_ptr), const_method_stub<C, method_ptr> };
    }

    template <class C, R(C::* const method_ptr)(A...)>
    static delegate from(C & object) noexcept
    {
        return { &object, method_stub<C, method_ptr> };
    }

    template <class C, R(C::* const method_ptr)(A...) const>
    static delegate from(C const & object) noexcept
    {
        return { const_cast<C *>(&object), const_method_stub<C, method_ptr> };
    }

    template <typename T>
    static delegate from(T && f)
    {
        return ::std::forward<T>(f);
    }

    static delegate from(R(* const function_ptr)(A...))
    {
        return function_ptr;
    }

    template <class C>
    using member_pair = ::std::pair<C * const, R(C::* const)(A...)>;

    template <class C>
    using const_member_pair = ::std::pair<C const * const, R(C::* const)(A...) const>;

    template <class C>
    static delegate from(C * const object_ptr, R(C::* const method_ptr)(A...))
    {
        return member_pair<C>(object_ptr, method_ptr);
    }

    template <class C>
    static delegate from(C const * const object_ptr, R(C::* const method_ptr)(A...) const)
    {
        return const_member_pair<C>(object_ptr, method_ptr);
    }

    template <class C>
    static delegate from(C & object, R(C::* const method_ptr)(A...))
    {
        return member_pair<C>(&object, method_ptr);
    }

    template <class C>
    static delegate from(C const & object, R(C::* const method_ptr)(A...) const)
    {
        return const_member_pair<C>(&object, method_ptr);
    }

    void reset(void)
    {
        stub_ptr_ = nullptr;
        store_.reset();
    }

    void reset_stub(void) noexcept { stub_ptr_ = nullptr; }

    void swap(delegate & other) noexcept { ::std::swap(*this, other); }

    bool operator==(delegate const & rhs) const noexcept
    {
        // comparison between functor and non-functor is left as undefined at the moment.
        if (store_size_ && rhs.store_size_) // both functors
            return (std::memcmp(store_.get(), rhs.store_.get(), store_size_) == 0) && (stub_ptr_ == rhs.stub_ptr_);
        return (object_ptr_ == rhs.object_ptr_) && (stub_ptr_ == rhs.stub_ptr_);
    }

    bool operator!=(delegate const & rhs) const noexcept
    {
        return !operator==(rhs);
    }

    bool operator<(delegate const & rhs) const noexcept
    {
        return (object_ptr_ < rhs.object_ptr_) ||
               ((object_ptr_ == rhs.object_ptr_) && (stub_ptr_ < rhs.stub_ptr_));
    }

    bool operator==(::std::nullptr_t const) const noexcept
    {
        return !stub_ptr_;
    }

    bool operator!=(::std::nullptr_t const) const noexcept
    {
        return stub_ptr_;
    }

    explicit operator bool() const noexcept
    {
        return stub_ptr_;
    }

    R operator()(A... args) const
    {
        //  assert(stub_ptr);
        return stub_ptr_(object_ptr_, ::std::forward<A>(args)...);
    }

private:
    friend struct ::std::hash<delegate>;

    using deleter_type = void (*)(void *);

    void * object_ptr_              = nullptr;
    stub_ptr_type stub_ptr_         {};

    deleter_type deleter_           = nullptr;

    ::std::shared_ptr<void> store_  = nullptr;
    ::std::size_t store_size_       = 0;

    template <class T>
    static void functor_deleter(void * const p)
    {
        static_cast<T *>(p)->~T();
        operator delete(p);
    }

    template <class T>
    static void deleter_stub(void * const p)
    {
        static_cast<T *>(p)->~T();
    }

    template <R(*function_ptr)(A...)>
    static R function_stub(void * const, A && ... args)
    {
        return function_ptr(::std::forward<A>(args)...);
    }

    template <class C, R(C::*method_ptr)(A...)>
    static R method_stub(void * const object_ptr, A && ... args)
    {
        return (static_cast<C *>(object_ptr)->*method_ptr)(::std::forward<A>(args)...);
    }

    template <class C, R(C::*method_ptr)(A...) const>
    static R const_method_stub(void * const object_ptr, A && ... args)
    {
        return (static_cast<C const *>(object_ptr)->*method_ptr)(::std::forward<A>(args)...);
    }

    template <typename>
    struct is_member_pair : ::std::false_type { };

    template <class C>
    struct is_member_pair< ::std::pair<C * const, R(C::* const)(A...)> > : ::std::true_type {};

    template <typename>
    struct is_const_member_pair : ::std::false_type { };

    template <class C>
    struct is_const_member_pair< ::std::pair<C const * const, R(C::* const)(A...) const> > : ::std::true_type {};

    template <typename T>
    static typename ::std::enable_if<!(is_member_pair<T>::value || is_const_member_pair<T>::value), R>::type
    functor_stub(void * const object_ptr, A && ... args)
    {
        return (*static_cast<T *>(object_ptr))(::std::forward<A>(args)...);
    }

    template <typename T>
    static typename ::std::enable_if<is_member_pair<T>::value || is_const_member_pair<T>::value, R>::type
    functor_stub(void * const object_ptr, A && ... args)
    {
        return (static_cast<T *>(object_ptr)->first->*static_cast<T *>(object_ptr)->second)(::std::forward<A>(args)...);
    }
};

}

namespace std
{
template <typename R, typename ...A>
struct hash<::fastdelegate::delegate<R(A...)> >
{
    size_t operator()(::fastdelegate::delegate<R(A...)> const & d) const noexcept
    {
        auto const seed(hash<void *>()(d.object_ptr_));
        return hash<decltype(d.stub_ptr_)>()(d.stub_ptr_) + 0x9e3779b9 + (seed << 6) + (seed >> 2);
    }
};
}

#endif // SRDELEGATE_HPP