//===-- rosa/support/squashed_int.hpp ---------------------------*- C++ -*-===//
//
//                                 The RoSA Framework
//
//===----------------------------------------------------------------------===//
///
/// \file rosa/support/squashed_int.hpp
///
/// \author David Juhasz (david.juhasz@tuwien.ac.at)
///
/// \date 2017-2019
///
/// \brief Facilities for squashing integer types into standard equivalents.
///
/// \note This implementation is partially based on the \c squashed_int
///       implementation of CAF.
/// \todo Check license.
///
//===----------------------------------------------------------------------===//

#ifndef ROSA_SUPPORT_SQUASHED_INT_HPP
#define ROSA_SUPPORT_SQUASHED_INT_HPP

#include "rosa/support/type_list.hpp"
#include "rosa/support/type_pair.hpp"

namespace rosa {

/// Compile-time list of integer types.
///
/// \note This list is used to select a proper type as \c rosa::type_nr_t,
/// always make sure that \c rosa::type_nr_t remains correct whenever changing
/// the list.
using IntegerTypesBySize = TypeList< // bytes
    none_t,                          // 0
    TypePair<int8_t, uint8_t>,       // 1
    TypePair<int16_t, uint16_t>,     // 2
    none_t,                          // 3
    TypePair<int32_t, uint32_t>,     // 4
    none_t,                          // 5
    none_t,                          // 6
    none_t,                          // 7
    TypePair<int64_t, uint64_t>      // 8
    >;

/// Squashes integral types (except \c bool) into \c [u]int_[8|16|32|64]_t
/// equivalents.
///
/// The squashed type for a type \c T can be obtained as \code
/// typename SquashedInt<T>::Type
/// \endcode
///
/// \tparam T the integral type to squash
///
/// \pre \p T is an integral type:\code
/// std::is_integral<T>::value
/// \endcode
template <typename T> struct SquashedInt {
  STATIC_ASSERT((std::is_integral<T>::value && !std::is_same<T, bool>::value),
                "squashing a non-integral type or bool");
  using TPair = typename TypeListAt<IntegerTypesBySize, sizeof(T)>::Type;
  using Type =
      typename std::conditional<std::is_signed<T>::value, typename TPair::First,
                                typename TPair::Second>::type;
};

/// Convenience alias for obtaining a squashed integer type.
template <typename T> using squashed_int_t = typename SquashedInt<T>::Type;

/// \defgroup SquashedType Implementation for squashing types
///
/// \brief Squashes a type.
///
/// The squashed type for a type \c T can be obtained as \code
/// typename SquashedType<T>::Type
/// \endcode
/// The resulting type is squashed with \c rosa::SquashedInt if \c T is
/// integral but not \c bool, and remains \p T otherwise.
///@{

/// Definition for the general case, when squashing a non-integral type.
///
/// \tparam T the type to squash
/// \tparam IsIntegral Always use the default value!
template <typename T, bool IsIntegral = std::is_integral<T>::value>
struct SquashedType {
  using Type = T;
};

/// Specialization for the case when squashing an integral type.
///
/// \tparam T the type to squash
template <typename T> struct SquashedType<T, true> {
  using Type = squashed_int_t<T>;
};

/// Specialization for the type \c bool.
///
/// \note The type \c bool is an integral type and would be squashed by the
/// general case to \c uint8_t without this specialization.
template <> struct SquashedType<bool, true> { using Type = bool; };

///@}

/// Convenience alias for obtaining a squashed type.
template <typename T> using squashed_t = typename SquashedType<T>::Type;

/// \defgroup SquashedTypeList Implementation for squashing lists of types
///
/// \brief Squashes a \c rosa::TypeList elementwise.
///
/// Replaces all types in a \c rosa::TypeList with their corresponding squashed
/// types by using \c rosa::SquashedType. The squashed \c rosa::TypeList
/// corresponding to \c List can be obtained as \code
/// typename SquashedTypeList<List>::Type
/// \endcode
///@{

/// Declaration of the template.
///
/// \tparam List \c rosa::TypeList to squash
template <typename List> struct SquashedTypeList;

// Specialization for \c rosa::EmptyTypeList.
template <> struct SquashedTypeList<EmptyTypeList> {
  using Type = EmptyTypeList;
};

/// Specialization for non-empty \c rosa::TypeList.
template <typename T, typename... Ts>
struct SquashedTypeList<TypeList<T, Ts...>> {
  using Type = typename TypeListPush<
      squashed_t<T>, typename SquashedTypeList<TypeList<Ts...>>::Type>::Type;
};

///@}

} // End namespace rosa

#endif // ROSA_SUPPORT_SQUASHED_INT_HPP