#ifndef SASS_UNITS_H
#define SASS_UNITS_H

#include <cmath>
#include <string>
#include <sstream>

namespace Sass {

  const double PI = std::acos(-1);

  enum UnitClass {
    LENGTH = 0x000,
    ANGLE = 0x100,
    TIME = 0x200,
    FREQUENCY = 0x300,
    RESOLUTION = 0x400,
    INCOMMENSURABLE = 0x500
  };

  enum UnitType {

    // size units
    IN = UnitClass::LENGTH,
    CM,
    PC,
    MM,
    PT,
    PX,

    // angle units
    DEG = ANGLE,
    GRAD,
    RAD,
    TURN,

    // time units
    SEC = TIME,
    MSEC,

    // frequency units
    HERTZ = FREQUENCY,
    KHERTZ,

    // resolutions units
    DPI = RESOLUTION,
    DPCM,
    DPPX,

    // for unknown units
    UNKNOWN = INCOMMENSURABLE

  };

  extern const double size_conversion_factors[6][6];
  extern const double angle_conversion_factors[4][4];
  extern const double time_conversion_factors[2][2];
  extern const double frequency_conversion_factors[2][2];
  extern const double resolution_conversion_factors[3][3];

  enum Sass::UnitType string_to_unit(const std::string&);
  const char* unit_to_string(Sass::UnitType unit);
  enum Sass::UnitClass get_unit_type(Sass::UnitType unit);
  std::string get_unit_class(Sass::UnitType unit);
  std::string unit_to_class(const std::string&);
  // throws incompatibleUnits exceptions
  double conversion_factor(const std::string&, const std::string&, bool = true);

  class incompatibleUnits: public std::exception
  {
    public:
      const char* msg;
      incompatibleUnits(Sass::UnitType a, Sass::UnitType b)
      : exception()
      {
        std::stringstream ss;
        ss << "Incompatible units: ";
        ss << "'" << unit_to_string(a) << "' and ";
        ss << "'" << unit_to_string(b) << "'";
        // hold on to string on stack!
        std::string str(ss.str());
        msg = str.c_str();
      }
      virtual const char* what() const throw()
      {
        return msg;
      }
  };

}

#endif