// Copyright 2019 The SwiftShader Authors. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//    http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#ifndef rr_Traits_hpp
#define rr_Traits_hpp

#include <stdint.h>
#include <type_traits>

#ifdef Bool
#undef Bool // b/127920555
#endif

namespace rr {

// Forward declarations
class Value;

class Void;
class Bool;
class Byte;
class SByte;
class Short;
class UShort;
class Int;
class UInt;
class Long;
class Half;
class Float;
class Float4;

template<class T> class Pointer;
template<class T> class LValue;
template<class T> class RValue;

// enabled_if_t is identical to C++14's std::enable_if_t.
// std::enable_if_t was introduced in C++14, but Reactor must support
// C++11.
template<bool Condition, class TrueType = void>
using enable_if_t = typename std::enable_if<Condition, TrueType>::type;

// IsDefined<T>::value is true if T is a valid type, otherwise false.
template <typename T, typename Enable = void>
struct IsDefined
{
	static constexpr bool value = false;
};

template <typename T>
struct IsDefined<T, enable_if_t<(sizeof(T)>0)> >
{
	static constexpr bool value = true;
};

template <>
struct IsDefined<void>
{
	static constexpr bool value = true;
};

// CToReactorT<T> resolves to the corresponding Reactor type for the given C
// template type T.
template<typename T, typename ENABLE = void> struct CToReactor;
template<typename T> using CToReactorT = typename CToReactor<T>::type;

// CToReactor specializations for POD types.
template<> struct CToReactor<void>    	{ using type = Void; };
template<> struct CToReactor<bool>    	{ using type = Bool;   static Bool   cast(bool);     };
template<> struct CToReactor<uint8_t> 	{ using type = Byte;   static Byte   cast(uint8_t);  };
template<> struct CToReactor<int8_t>  	{ using type = SByte;  static SByte  cast(int8_t);   };
template<> struct CToReactor<int16_t> 	{ using type = Short;  static Short  cast(int16_t);  };
template<> struct CToReactor<uint16_t>	{ using type = UShort; static UShort cast(uint16_t); };
template<> struct CToReactor<int32_t> 	{ using type = Int;    static Int    cast(int32_t);  };
template<> struct CToReactor<uint32_t>	{ using type = UInt;   static UInt   cast(uint32_t); };
template<> struct CToReactor<float>   	{ using type = Float;  static Float  cast(float);    };
template<> struct CToReactor<float[4]>	{ using type = Float4; static Float4 cast(float[4]); };

// TODO: Long has no constructor that takes a uint64_t
template<> struct CToReactor<uint64_t>	{ using type = Long;  /* static Long   cast(uint64_t); */ };

// HasReactorType<T>::value resolves to true iff there exists a
// CToReactorT specialization for type T.
template<typename T>
using HasReactorType = IsDefined< CToReactorT<T> >;

// CToReactorPtr<T>::type resolves to the corresponding Reactor Pointer<>
// type for T*.
// For T types that have a CToReactorT<> specialization,
// CToReactorPtr<T>::type resolves to Pointer< CToReactorT<T> >, otherwise
// CToReactorPtr<T>::type resolves to Pointer<Byte>.
template<typename T, typename ENABLE = void> struct CToReactorPtr
{
	using type = Pointer<Byte>;
	static inline type cast(const T* v); // implemented in Traits.inl
};

// CToReactorPtr specialization for T types that have a CToReactorT<>
// specialization.
template<typename T> struct CToReactorPtr<T, enable_if_t< HasReactorType<T>::value > >
{
	using type = Pointer< CToReactorT<T> >;
	static inline type cast(const T* v); // implemented in Traits.inl
};

// CToReactorPtr specialization for void*.
// Maps to Pointer<Byte> instead of Pointer<Void>.
template<> struct CToReactorPtr<void, void>
{
	using type = Pointer<Byte>;
	static inline type cast(const void* v); // implemented in Traits.inl
};

// CToReactorPtr specialization for function pointer types.
// Maps to Pointer<Byte>.
// Drops the 'const' qualifier from the cast() method to avoid warnings
// about const having no meaning for function types.
template<typename T> struct CToReactorPtr<T, enable_if_t< std::is_function<T>::value > >
{
	using type = Pointer<Byte>;
	static inline type cast(T* v); // implemented in Traits.inl
};

template<typename T> using CToReactorPtrT = typename CToReactorPtr<T>::type;

// CToReactor specialization for pointer types.
// For T types that have a CToReactorT<> specialization,
// CToReactorT<T*>::type resolves to Pointer< CToReactorT<T> >, otherwise
// CToReactorT<T*>::type resolves to Pointer<Byte>.
template<typename T>
struct CToReactor<T, enable_if_t<std::is_pointer<T>::value> >
{
	using elem = typename std::remove_pointer<T>::type;
	using type = CToReactorPtrT<elem>;
	static inline type cast(T v); // implemented in Traits.inl
};

// CToReactor specialization for enum types.
template<typename T>
struct CToReactor<T, enable_if_t<std::is_enum<T>::value> >
{
	using underlying = typename std::underlying_type<T>::type;
	using type = CToReactorT<underlying>;
	static type cast(T v); // implemented in Traits.inl
};

// IsRValue::value is true if T is of type RValue<X>, where X is any type.
template <typename T, typename Enable = void> struct IsRValue { static constexpr bool value = false; };
template <typename T> struct IsRValue<T, enable_if_t<IsDefined<typename T::rvalue_underlying_type>::value> > { static constexpr bool value = true; };

// IsLValue::value is true if T is of, or derives from type LValue<T>.
template <typename T> struct IsLValue { static constexpr bool value = std::is_base_of<LValue<T>, T>::value; };

// IsReference::value is true if T is of type Reference<X>, where X is any type.
template <typename T, typename Enable = void> struct IsReference { static constexpr bool value = false; };
template <typename T> struct IsReference<T, enable_if_t<IsDefined<typename T::reference_underlying_type>::value> > { static constexpr bool value = true; };

// ReactorTypeT<T> returns the LValue Reactor type for T.
// T can be a C-type, RValue or LValue.
template<typename T, typename ENABLE = void> struct ReactorType;
template<typename T> using ReactorTypeT = typename ReactorType<T>::type;
template<typename T> struct ReactorType<T, enable_if_t<IsDefined<CToReactorT<T>>::value> >
{
	using type = CToReactorT<T>;
	static type cast(T v) { return CToReactor<T>::cast(v); }
};
template<typename T> struct ReactorType<T, enable_if_t<IsRValue<T>::value> >
{
	using type = typename T::rvalue_underlying_type;
	static type cast(T v) { return type(v); }
};
template<typename T> struct ReactorType<T, enable_if_t<IsLValue<T>::value> >
{
	using type = T;
	static type cast(T v) { return type(v); }
};
template<typename T> struct ReactorType<T, enable_if_t<IsReference<T>::value> >
{
	using type = T;
	static type cast(T v) { return type(v); }
};


// Reactor types that can be used as a return type for a function.
template <typename T> struct CanBeUsedAsReturn { static constexpr bool value = false; };
template <> struct CanBeUsedAsReturn<Void>     { static constexpr bool value = true; };
template <> struct CanBeUsedAsReturn<Int>      { static constexpr bool value = true; };
template <> struct CanBeUsedAsReturn<UInt>     { static constexpr bool value = true; };
template <> struct CanBeUsedAsReturn<Float>    { static constexpr bool value = true; };
template <typename T> struct CanBeUsedAsReturn<Pointer<T>> { static constexpr bool value = true; };

// Reactor types that can be used as a parameter types for a function.
template <typename T> struct CanBeUsedAsParameter { static constexpr bool value = false; };
template <> struct CanBeUsedAsParameter<Int>      { static constexpr bool value = true; };
template <> struct CanBeUsedAsParameter<UInt>     { static constexpr bool value = true; };
template <> struct CanBeUsedAsParameter<Float>    { static constexpr bool value = true; };
template <typename T> struct CanBeUsedAsParameter<Pointer<T>> { static constexpr bool value = true; };

// AssertParameterTypeIsValid statically asserts that all template parameter
// types can be used as a Reactor function parameter.
template<typename T, typename ... other>
struct AssertParameterTypeIsValid : AssertParameterTypeIsValid<other...>
{
	static_assert(CanBeUsedAsParameter<T>::value, "Invalid parameter type");
};
template<typename T>
struct AssertParameterTypeIsValid<T>
{
	static_assert(CanBeUsedAsParameter<T>::value, "Invalid parameter type");
};

// AssertFunctionSignatureIsValid statically asserts that the Reactor
// function signature is valid.
template<typename Return, typename... Arguments>
class AssertFunctionSignatureIsValid;
template<typename Return>
class AssertFunctionSignatureIsValid<Return(Void)> {};
template<typename Return, typename... Arguments>
class AssertFunctionSignatureIsValid<Return(Arguments...)>
{
	static_assert(CanBeUsedAsReturn<Return>::value, "Invalid return type");
	static_assert(sizeof(AssertParameterTypeIsValid<Arguments...>) >= 0, "");
};

}  // namespace rr

#endif // rr_Traits_hpp