core_misc/tjp/core/functions/Dispatch.hpp

// TJP COPYRIGHT HEADER

#pragma once

#include "Dispatch.h"
#include <tjp/core/assert/debug_assert.h>
#include <tjp/core/exception/Exception.hpp>
#include <tjp/core/rtti/RTTI.hpp>

#include <functional>
#include <map>


namespace tjp {
namespace core {

struct DispatchException : Exception
{
	typedef Exception Super;
	DispatchException(const type_index &what) : Super("DispatchException") {}
};

struct Variable
{
	void *v;
	type_index type;

	template<typename T>
	Variable(const T &t) :
	   type(type_id<T>())
	{
	   v = reinterpret_cast<void *>(const_cast<T *>(&t));
	}

	template<typename T>
	T &deref ()
	{
		debug_assert(type_id<T>() == type);
		return *reinterpret_cast<T *>(v);
	}

	template<typename T>
	T &&move ()
	{
		debug_assert(type_id<T>() == type);
		return std::move(*reinterpret_cast<T *>(v));
	}

	template<typename T>
	Variable &operator =(T &&t)
	{
		deref<T>() = std::move(t);
		return *this;
	}

	template<typename T>
	Variable &operator =(const T &t)
	{
		deref<T>() = t;
		return *this;
	}

protected:
	Variable () :
		v(nullptr),
		type(type_id<void>())
	{}
	
	template<typename T>
	void ref(const T &t)
	{
		type = { type_id<T>() };
		v = reinterpret_cast<void *>(const_cast<T *>(&t));
	}
} ;

template<typename T>
struct StackVariable : Variable
{
	T t;
	
	StackVariable()
	{
		ref(t);
	}
	
	operator T()
	{
		return t;
	}
	
	T &&move()
	{
		return std::move(t);
	}
} ;

typedef std::function<void(Variable &result, Variable &&param)> DispatchFunction;

template<typename R, typename T>
DispatchFunction asDispatchFunction(std::function<R(T)> &&f)
{
	return [f](Variable &result, Variable &&param) -> void {
		auto v = f(param.deref<T>());
		auto &r = result.deref<R>();
		r = v;
	} ;
}

struct FunctionDispatchOnParam
{
	std::map<type_index, DispatchFunction> dispatch;
	
	void execute(Variable &result, Variable &&param)
	{
		auto &type = param.type;

		auto i = dispatch.find(type);
		if (i == dispatch.end())
		{
			debug_assert(false);
			throw DispatchException(type);
		}

		i->second(result, std::move(param));
	}

	template<typename T>
	T execute(Variable &&param)
	{
		StackVariable<T> result;
		execute(result, std::move(param));
		return result;
	}
	
	void bind(const type_index &type, DispatchFunction &&f)
	{
		dispatch[type] = std::move(f);
	}

	template<typename T>
	void bind(std::function<void(Variable &result, Variable &&param)> &&f)
	{
		bind(type_id<T>(), std::move(f));
	}

	template<typename R, typename T>
	void bind(std::function<R(const T&)> &&f)
	{
		bind(type_id<T>(), asDispatchFunction<R, T>(f));
	}
} ;

struct FunctionDispatchOnReturn
{
	std::map<type_index, DispatchFunction> dispatch;
	
	void execute(Variable &result, Variable &&param)
	{
		auto &type = result.type;
		auto i = dispatch.find(type);
		if (i == dispatch.end())
		{
			debug_assert(false);
			throw DispatchException(type);
		}
			
		i->second(result, std::move(param));
	}

	template<typename T>
	T execute(Variable &&param)
	{
		StackVariable<T> result;
		execute(result, std::move(param));
		return result;
	}
	
	void bind(const type_index &type, DispatchFunction &&f)
	{
		dispatch[type] = f;
	}

	template<typename R>
	void bind(std::function<void(Variable &result, Variable &&param)> &&f)
	{
		bind(type_id<R>(), std::move(f));
	}

	template<typename R, typename T>
	void bind(std::function<R(const T&)> &&f)
	{
		bind(type_id<R>(), asDispatchFunction<R, T>(f));
	}
} ;


} // namespace
} // namespace