quantity.hpp

#ifndef LIBSBX_UNITS_QUANTITY_HPP_
#define LIBSBX_UNITS_QUANTITY_HPP_
 
#include <ratio>
#include <cmath>
#include <typeindex>
#include <iostream>
 
#include <fmt/format.h>
 
namespace sbx::units {
 
template<typename Type>
concept representation = (std::is_integral_v<Type> && !std::is_same_v<Type, bool> ) || std::is_floating_point_v<Type>;
 
template<typename Type>
concept ratio = requires {
  { Type::num } -> std::convertible_to<std::intmax_t>;
  { Type::den } -> std::convertible_to<std::intmax_t>;
};
 
template<typename LhsDimension, typename RhsDimension = LhsDimension, typename ResultDimension = LhsDimension>
concept addable_dimensions = std::is_same_v<LhsDimension, RhsDimension> || requires(LhsDimension dimension1, ResultDimension dimension2) {
  { dimension1 + dimension2 } -> std::same_as<ResultDimension>;
  { dimension2 + dimension1 } -> std::same_as<ResultDimension>;
};
 
template<typename LhsDimension, typename RhsDimension = LhsDimension, typename ResultDimension = LhsDimension>
concept subtractable_dimensions = std::is_same_v<LhsDimension, RhsDimension> || requires(LhsDimension dimension1, ResultDimension dimension2) {
  { dimension1 - dimension2 } -> std::same_as<ResultDimension>;
  { dimension2 - dimension1 } -> std::same_as<ResultDimension>;
};
 
template<typename LhsDimension, typename RhsDimension = LhsDimension, typename ResultDimension = LhsDimension>
concept multipliable_dimensions = std::is_same_v<LhsDimension, RhsDimension> || requires(LhsDimension dimension1, ResultDimension dimension2) {
  { dimension1 * dimension2 } -> std::same_as<ResultDimension>;
  { dimension2 * dimension1 } -> std::same_as<ResultDimension>;
};
 
template<typename LhsDimension, typename RhsDimension = LhsDimension, typename ResultDimension = LhsDimension>
concept dividable_dimensions = std::is_same_v<LhsDimension, RhsDimension> || requires(LhsDimension dimension1, ResultDimension dimension2) {
  { dimension1 / dimension2 } -> std::same_as<ResultDimension>;
  { dimension2 / dimension1 } -> std::same_as<ResultDimension>;
};
 
template<ratio Ratio, ratio OtherRatio>
struct ratio_multiply {
  using type = std::ratio<Ratio::num + OtherRatio::num, Ratio::den * OtherRatio::den>;
}; // struct ratio_multiply
 
template<ratio Ratio, ratio OtherRatio>
using ratio_multiply_t = typename ratio_multiply<Ratio, OtherRatio>::type;
 
template<representation Representation, ratio Ratio, ratio OtherRatio>
struct ratio_conversion {
  static constexpr auto value = 
    static_cast<Representation>(OtherRatio::num) / static_cast<Representation>(OtherRatio::den) *
    static_cast<Representation>(Ratio::den) / static_cast<Representation>(Ratio::num);
}; // struct ratio_conversion
 
template<representation Representation, ratio R1, ratio R2>
inline static constexpr auto ratio_conversion_v = ratio_conversion<Representation, R1, R2>::value;
 
template<typename Dimension, representation Representation, ratio Ratio = std::ratio<1, 1>>
class quantity {
 
public:
 
  using dimension_type = Dimension;
  using value_type = Representation;
  using ratio_type = Ratio;
 
  quantity() = default;
 
  template<std::convertible_to<value_type> Type>
  constexpr explicit quantity(Type value) noexcept
  : _value{static_cast<value_type>(value)} { }
 
  template<representation OtherRepresentation, ratio OtherRatio = ratio_type>
  constexpr quantity(const quantity<dimension_type, OtherRepresentation, OtherRatio>& other) noexcept
  : _value{quantity_cast<quantity>(other)} { }
 
  constexpr quantity(const quantity& other) noexcept = default;
 
  constexpr quantity(quantity&& other) noexcept = default;
 
  constexpr ~quantity() noexcept = default;
 
  constexpr auto operator=(const quantity& other) noexcept -> quantity& = default;
 
  constexpr auto operator=(quantity&& other) noexcept -> quantity& = default;
 
  template<representation OtherRepresentation, ratio OtherRatio>
  constexpr auto operator=(const quantity<dimension_type, OtherRepresentation, OtherRatio>& other) noexcept -> quantity& {
    _value = static_cast<value_type>(other.value()) * ratio_conversion_v<value_type, Ratio, OtherRatio>;
 
    return *this;
  }
 
  template<representation OtherRepresentation, ratio OtherRatio>
  constexpr auto operator+=(const quantity<dimension_type, OtherRepresentation, OtherRatio>& other) noexcept -> quantity& {
    _value += static_cast<value_type>(other.value()) * ratio_conversion_v<value_type, Ratio, OtherRatio>;
 
    return *this;
  }
 
  template<representation OtherRepresentation, ratio OtherRatio>
  constexpr auto operator-=(const quantity<dimension_type, OtherRepresentation, OtherRatio>& other) noexcept -> quantity& {
    _value -= static_cast<value_type>(other.value()) * ratio_conversion_v<value_type, Ratio, OtherRatio>;
 
    return *this;
  }
 
  constexpr auto operator-() const noexcept -> quantity {
    return quantity{-_value};
  }
 
  constexpr auto value() const noexcept -> value_type {
    return _value;
  }
 
  constexpr operator value_type() const noexcept {
    return _value;
  }
 
private:
 
  value_type _value{};
 
}; // class quantity
 
template<typename Dimension, representation Representation, ratio Ratio>
constexpr auto operator==(const quantity<Dimension, Representation, Ratio>& lhs, const quantity<Dimension, Representation, Ratio>& rhs) noexcept -> bool {
  return lhs.value() == rhs.value();
}
 
template<typename Dimension, representation Representation, ratio Ratio>
constexpr auto operator<=>(const quantity<Dimension, Representation, Ratio>& lhs, const quantity<Dimension, Representation, Ratio>& rhs) noexcept -> std::partial_ordering {
  return lhs.value() <=> rhs.value();
}
 
template<typename Dimension, representation LhsRepresentation, ratio LhsRatio, representation RhsRepresentation, ratio RhsRatio>
constexpr auto operator+(quantity<Dimension, LhsRepresentation, LhsRatio> lhs, const quantity<Dimension, RhsRepresentation, RhsRatio>& rhs) -> quantity<Dimension, LhsRepresentation, LhsRatio> {
  return lhs += rhs;
}
 
template<typename Dimension, representation LhsRepresentation, ratio LhsRatio, representation RhsRepresentation, ratio RhsRatio>
constexpr auto operator-(quantity<Dimension, LhsRepresentation, LhsRatio> lhs, const quantity<Dimension, RhsRepresentation, RhsRatio>& rhs) -> quantity<Dimension, LhsRepresentation, LhsRatio> {
  return lhs -= rhs;
}
 
template<typename Dimension, representation Representation, ratio Ratio>
constexpr auto operator-(const quantity<Dimension, Representation, Ratio>& value) -> quantity<Dimension, Representation, Ratio> {
  return -value;
}
 
template<typename TargetQuantity, representation FromRepresentation, ratio FromRatio>
constexpr auto quantity_cast(const quantity<typename TargetQuantity::dimension_type, FromRepresentation, FromRatio>& from) -> TargetQuantity {
  using value_type = typename TargetQuantity::value_type;
  using to_ratio = typename TargetQuantity::ratio_type;
 
  using ratio_type = std::conditional_t<std::is_floating_point_v<value_type>, value_type, std::float_t>;
 
  const auto ratio = ratio_conversion_v<ratio_type, to_ratio, FromRatio>;
 
  return TargetQuantity{static_cast<value_type>(from.value()) * static_cast<value_type>(ratio)};
}
 
} // namespace sbx::units
 
template<typename Dimension, sbx::units::representation Representation, sbx::units::ratio Ratio>
struct fmt::formatter<sbx::units::quantity<Dimension, Representation, Ratio>> {
 
  template<typename ParseContext>
  constexpr auto parse(ParseContext& context) -> decltype(context.begin()) {
    return context.begin();
  }
 
  template<typename FormatContext>
  auto format(const sbx::units::quantity<Dimension, Representation, Ratio>& quantity, FormatContext& context) -> decltype(context.out()) {
    return fmt::format_to(context.out(), "{}", quantity.value());
  }
 
}; // fmt::formatter
 
#endif // LIBSBX_UNITS_QUANTITY_HPP_