static_assert( __cplusplus > 2020'99 );

#pragma once

// Analogue to `#include <functional>`

#include <Alepha/Alepha.h>

namespace Alepha::Hydrogen::Meta  ::detail::  functional_m
{
	inline namespace exports
	{
		template< typename MetaFunction, typename Arg >
		constexpr auto bind1st( MetaFunction func, Arg arg );
	}

	template< typename MetaFunction, typename Arg > struct binder1st;

	template< typename MetaFunction, typename Arg1, typename Arg2 >
	constexpr decltype( auto )
	invoke_call( MetaFunction func, Meta::type_value< Arg1 > arg1, Meta::type_value< Arg2 > arg2 )
	{
		return func( arg1, arg2 );
	}

	template< typename MetaFunction, typename Arg >
	struct binder1st< MetaFunction, Meta::type_value< Arg > >
	{
		MetaFunction func;
		Meta::type_value< Arg > arg;

		template< typename Second >
		constexpr decltype( auto )
		operator () ( const Second &second )
		{
			return invoke_call( func, arg, second );
		}
	};

	template< typename MetaFunction, typename Arg >
	constexpr auto
	exports::bind1st( MetaFunction func, Arg arg )
	{
		return binder1st< MetaFunction, Arg >{ func, arg };
	}
}

namespace Alepha::Hydrogen::Meta::inline exports::inline functional_m
{
	using namespace detail::functional_m::exports;
}