draconisplusplus/include/rfl/comparisons.hpp

#ifndef RFL_COMPARISONS_HPP_
#define RFL_COMPARISONS_HPP_

#include <type_traits>

#include "Result.hpp"
#include "parsing/schema/ValidationType.hpp"

namespace rfl {

  template <auto _threshold>
  struct EqualTo {
    template <class T>
    static Result<T> validate(T _value) noexcept {
      constexpr auto threshold = static_cast<T>(_threshold);
      if (_value != threshold) {
        return Error(
            "Value expected to be equal to " + std::to_string(threshold) +
            ", but got " + std::to_string(_value) + "."
        );
      }
      return _value;
    }

    template <class T>
    static parsing::schema::ValidationType to_schema() {
      using ValidationType = parsing::schema::ValidationType;
      const auto value =
          std::is_floating_point_v<T>
              ? std::variant<double, int>(static_cast<double>(_threshold))
              : std::variant<double, int>(static_cast<int>(_threshold));
      return ValidationType {ValidationType::EqualTo {.value_ = value}};
    }
  };

  template <auto _threshold>
  struct Minimum {
    template <class T>
    static Result<T> validate(T _value) noexcept {
      constexpr auto threshold = static_cast<T>(_threshold);
      if (_value < threshold) {
        return Error(
            "Value expected to be greater than or equal to " +
            std::to_string(threshold) + ", but got " + std::to_string(_value) +
            "."
        );
      }
      return _value;
    }

    template <class T>
    static parsing::schema::ValidationType to_schema() {
      using ValidationType = parsing::schema::ValidationType;
      const auto value =
          std::is_floating_point_v<T>
              ? std::variant<double, int>(static_cast<double>(_threshold))
              : std::variant<double, int>(static_cast<int>(_threshold));
      return ValidationType {ValidationType::Minimum {.value_ = value}};
    }
  };

  template <auto _threshold>
  struct ExclusiveMinimum {
    template <class T>
    static Result<T> validate(T _value) noexcept {
      constexpr auto threshold = static_cast<T>(_threshold);
      if (_value <= threshold) {
        return Error(
            "Value expected to be greater than " + std::to_string(threshold) +
            ", but got " + std::to_string(_value) + "."
        );
      }
      return _value;
    }

    template <class T>
    static parsing::schema::ValidationType to_schema() {
      using ValidationType = parsing::schema::ValidationType;
      const auto value =
          std::is_floating_point_v<T>
              ? std::variant<double, int>(static_cast<double>(_threshold))
              : std::variant<double, int>(static_cast<int>(_threshold));
      return ValidationType {ValidationType::ExclusiveMinimum {.value_ = value}
      };
    }
  };

  template <auto _threshold>
  struct Maximum {
    template <class T>
    static Result<T> validate(T _value) noexcept {
      constexpr auto threshold = static_cast<T>(_threshold);
      if (_value > threshold) {
        return Error(
            "Value expected to be less than or equal to " +
            std::to_string(threshold) + ", but got " + std::to_string(_value) +
            "."
        );
      }
      return _value;
    }

    template <class T>
    static parsing::schema::ValidationType to_schema() {
      using ValidationType = parsing::schema::ValidationType;
      const auto value =
          std::is_floating_point_v<T>
              ? std::variant<double, int>(static_cast<double>(_threshold))
              : std::variant<double, int>(static_cast<int>(_threshold));
      return ValidationType {ValidationType::Maximum {.value_ = value}};
    }
  };

  template <auto _threshold>
  struct ExclusiveMaximum {
    template <class T>
    static Result<T> validate(T _value) noexcept {
      constexpr auto threshold = static_cast<T>(_threshold);
      if (_value >= threshold) {
        return Error(
            "Value expected to be less than " + std::to_string(threshold) +
            ", but got " + std::to_string(_value) + "."
        );
      }
      return _value;
    }

    template <class T>
    static parsing::schema::ValidationType to_schema() {
      using ValidationType = parsing::schema::ValidationType;
      const auto value =
          std::is_floating_point_v<T>
              ? std::variant<double, int>(static_cast<double>(_threshold))
              : std::variant<double, int>(static_cast<int>(_threshold));
      return ValidationType {ValidationType::ExclusiveMaximum {.value_ = value}
      };
    }
  };

  template <auto _threshold>
  struct NotEqualTo {
    template <class T>
    static Result<T> validate(T _value) noexcept {
      constexpr auto threshold = static_cast<T>(_threshold);
      if (_value == threshold) {
        return Error(
            "Value expected to not be equal to " + std::to_string(threshold) +
            ", but got " + std::to_string(_value) + "."
        );
      }
      return _value;
    }

    template <class T>
    static parsing::schema::ValidationType to_schema() {
      using ValidationType = parsing::schema::ValidationType;
      const auto value =
          std::is_floating_point_v<T>
              ? std::variant<double, int>(static_cast<double>(_threshold))
              : std::variant<double, int>(static_cast<int>(_threshold));
      return ValidationType {ValidationType::NotEqualTo {.value_ = value}};
    }
  };

} // namespace rfl

#endif