#pragma once

#include <forstio/common.hpp>

#include <type_traits>
#include "unit_schema.hpp"

namespace saw {
namespace impl {

template<typename T, typename U>
class unit_matching;

template<typename... T>
class unit_redux_list {
	static_assert(sizeof...(T) == 0u, "Template type not supported");

	using Type = unit_redux_list<>;
};

template<typename T0, int64_t E0, typename... TL, int64_t... EL>
struct unit_redux_list<schema::UnitElement<T0,E0>, schema::UnitElement<TL,EL>...> {
	using Type = typename unit_matching<unit_redux_list<schema::UnitElement<T0,E0>, schema::UnitElement<TL,EL>...>, unit_redux_list<>>::TypeList;
};

template<typename T, typename U, typename V>
class unit_matching_reduce {
public:
	static_assert(always_false<T,U,V>, "Template type not supported");
};

/**
 * Iterate over the left list to check against the left element.
 */
template<typename T, int64_t E, typename T0, int64_t E0, typename... TL, int64_t... EL, typename... TR, int64_t... ER>
class unit_matching_reduce<schema::UnitElement<T,E>, unit_redux_list<schema::UnitElement<T0,E0>,schema::UnitElement<TL,EL>...>, unit_redux_list<schema::UnitElement<TR,ER>...>> {
public:
	static constexpr bool is_same = std::is_same_v<T,T0>;

	// Match T,E against T0,E0
	using ReducedType = typename std::conditional<is_same, schema::UnitElement<T,E+E0>, schema::UnitElement<T,E>>::type;
	using ReducedTypeList = typename std::conditional<is_same, unit_redux_list<schema::UnitElement<TR,ER>...>, unit_redux_list<schema::UnitElement<TR,ER>..., schema::UnitElement<T0,E0>>>::type;

	using NextMatcher = unit_matching_reduce<ReducedType, unit_redux_list<schema::UnitElement<TL,EL>...>, ReducedTypeList>;
	using Type = typename NextMatcher::Type;
	using TypeList = typename NextMatcher::TypeList;
	static constexpr int64_t Num = NextMatcher::Num;
};

/**
 * Final step after going through the list. This contains the final match result.
 * On the left is the accumulated type and on the right its's a list of non matching types
 */
template<typename T, int64_t E, typename... TR, int64_t... ER>
class unit_matching_reduce<schema::UnitElement<T,E>, unit_redux_list<>, unit_redux_list<schema::UnitElement<TR,ER>...>> {
public:
	using Type = schema::UnitElement<T,E>;
	using TypeList = unit_redux_list<schema::UnitElement<TR,ER>...>;
	static constexpr int64_t Num = E;
};

template<typename LR, typename RR>
class unit_matching {
	static_assert(always_false<LR,RR>, "Template type not supported");
};

template<typename... Ele>
class unit_matching<unit_redux_list<>, unit_redux_list<Ele...>> {
public:
	using TypeList = unit_redux_list<Ele...>;
};

template<typename Ele0, typename... EleL, typename... EleR>
class unit_matching<unit_redux_list<Ele0, EleL...>, unit_redux_list<EleR...>> {
public:
	// static constexpr bool is_same = std::is_same_v<T,T0>;

	using MatchReducer = unit_matching_reduce<Ele0, unit_redux_list<EleL...>, unit_redux_list<>>;

	using ReducedType = typename MatchReducer::Type;
	using ReducedTypeList = typename MatchReducer::TypeList;
	static constexpr int64_t Num = MatchReducer::Num;

	using TypeRightList = typename std::conditional<Num == 0u, unit_redux_list<EleR...>, unit_redux_list<EleR..., ReducedType>>::type;
	using TypeList = typename unit_matching<ReducedTypeList, TypeRightList>::TypeList;
};

template<typename BaseSchema, typename List>
class unit_add_base {
	static_assert(always_false<BaseSchema,List>, "Template type not supported");
};

template<typename BaseSchema, typename... Ele>
class unit_add_base<BaseSchema, unit_redux_list<Ele...>> {
public:
	using Schema = schema::Unit<BaseSchema, Ele...>;
};
}

template<typename BaseSchema, typename... UE>
struct unit_element_reduction {
	using TypeList = typename impl::unit_matching<impl::unit_redux_list<UE...>, impl::unit_redux_list<>>::TypeList;
	using Schema = typename impl::unit_add_base<BaseSchema, TypeList>::Schema;
};

template<typename U0, typename U1>
struct unit_multiplication {
	static_assert(always_false<U0,U1>, "Template type not supported");
};

template<typename BaseSchema, typename... UnitT, int64_t... UnitE, typename... UnitRhsT, int64_t... UnitRhsE>
struct unit_multiplication<
	schema::Unit<BaseSchema, schema::UnitElement<UnitT,UnitE>...>,
	schema::Unit<BaseSchema, schema::UnitElement<UnitRhsT,UnitRhsE>...>
> {
	using Schema = typename unit_element_reduction<BaseSchema, schema::UnitElement<UnitT,UnitE>..., schema::UnitElement<UnitRhsT, UnitRhsE>...>::Schema;
};

template<typename U0, typename U1>
struct unit_division {
	static_assert(always_false<U0,U1>, "Template type not supported");
};

template<typename BaseSchema, typename... UnitT, int64_t... UnitE, typename... UnitRhsT, int64_t... UnitRhsE>
struct unit_division<
	schema::Unit<BaseSchema, schema::UnitElement<UnitT,UnitE>...>,
	schema::Unit<BaseSchema, schema::UnitElement<UnitRhsT,UnitRhsE>...>
> {
	using Schema = typename unit_element_reduction<BaseSchema, schema::UnitElement<UnitT,UnitE>..., schema::UnitElement<UnitRhsT, -UnitRhsE>...>::Schema;
};

}