//

#include <string>
#include <map>
#include <functional>


namespace CXXHelper
{
	template <typename _Ret, typename _Key, typename... Args>
	class Dispatch
	{
	protected:
		std::map <_Key, std::function <_Ret (Args...)> > m_handlers;

	public:
		Dispatch () { }
		Dispatch (Dispatch && from)
		{
			m_handlers.swap (from.m_handlers);
		}

		Dispatch (const Dispatch & from)
		{
			from.CopyTo (*this);
		}

		Dispatch & operator = (const Dispatch & from)
		{
			from.CopyTo (*this);
			return (*this);
		}

		Dispatch & operator = (Dispatch && from)
		{
			m_handlers.swap (from.m_handlers);
			return (*this);
		}

		void swap (Dispatch & from)
		{
			m_handlers.swap (from.m_handlers);
		}

		void CopyTo (Dispatch & to) const
		{
			to.m_handlers = m_handlers;
		}

		void Release ()
		{
			m_handlers.clear ();
		}

		auto begin ()
		{
			return m_handlers.begin ();
		}

		auto end ()
		{
			return m_handlers.end ();
		}

		auto begin () const
		{
			return m_handlers.cbegin ();
		}

		auto end () const
		{
			return m_handlers.cend ();
		}

	public:
		template <typename U = _Ret>
		std::enable_if_t <! std::is_void <U>::value, U>
		operator () (const _Key k, Args... arg)
		{
			return Invoke (k, arg...);
		}

		template <typename U = _Ret>
		std::enable_if_t <std::is_void <U>::value, U>
		operator () (Args... arg)
		{
			Invoke (arg...);
		}

		template <typename U = _Ret>
		std::enable_if_t <! std::is_void <U>::value, U>
		Invoke (const _Key k, Args... arg)
		{
			auto Iter = m_handlers.find (k);
			if (Iter != m_handlers.end ())
			{
				return (*Iter).second (arg...);
			}

			return U { };
		}

		template <typename U = _Ret>
		std::enable_if_t <std::is_void <U>::value, U>
		Invoke (const _Key k, Args... arg)
		{
			auto Iter = m_handlers.find (k);
			if (Iter != m_handlers.end ())
			{
				(*Iter).second (arg...);
			}
		}


	public:
		inline void RemoveAll ()
		{
			Release ();
		}

		inline bool IsEmpty () const
		{
			return m_handlers.empty ();
		}

		inline int  GetSize () const
		{
			return (int)m_handlers.size ();
		}

		inline void AppendFrom (const Dispatch & from)
		{
			for (auto h : from.m_handlers)
				this->m_handlers.push_back (h);
		}

	public:
		Dispatch & operator += (Dispatch & from)
		{
			AppendFrom (from);
			return (*this);
		}

	public:
		template <typename TA>
		Dispatch & operator += (TA v)
		{
			Push (v);
			return (*this);
		}

	public:
		//	lambda 表达式会到这里
		//	Binder (bind 结果) 会到这里
		template <typename TX>
		//	inline void Push (const TX & handler)
		inline void Push (const _Key K, TX handler)
		{
			m_handlers.emplace (K, std::move (handler));
		}

		//	静态函数会到这里
		inline void Push (const _Key K, _Ret (*fn) (Args...))
		{
			m_handlers.emplace (K, std::move (fn));
		}

#if 1
		//	类的成员函数会到这里 - 3 个
		//	这里用了个小技巧: 把类实例和成员函数转换成一个临时的 lambda 函数
		//	另外, 不管 _Ret 是否为 void, 下面的代码都能通过编译 ! 暂不清楚 C++ 编译器是如何区分的 !
		template <typename TC>
		inline void Push (const _Key K, TC * inst, _Ret (TC::* mfn) (Args...))
		{
			m_handlers.emplace (K, [inst, mfn] (Args... args) { return (*inst.*mfn) (args...); });
		}

		template <typename TC>
		void Push (const _Key K, TC * inst, _Ret (TC::* mfn) (Args...) const)
		{
			m_handlers.emplace (K, [inst, mfn] (Args... args) { return (*inst.*mfn) (args...); });
		}

		template<typename TC>
		void Push (const _Key K, const TC * inst, _Ret (TC::* mfn) (Args...) const)
		{
			m_handlers.emplace (K, [inst, mfn] (Args... args) {return (*inst.*mfn) (args...); });
		}
#endif
	};

}