module Medidas
  class Unit
    attr_reader :base_unit

    def self.registered_units
      @registered_units ||= {}
    end

    def *(number)
      Measure.for(amount: number, unit: self)
    end

    def base_unit?(a_unit)
      a_unit == base_unit
    end

    def to_s
      @name
    end

    def inspect
      "#{self.class}(#{@name})"
    end

    def coerce(amount)
      raise TypeError, "Unit can't be coerced into Integer except for multiplication" unless caller.first.include?("`*'")

      [self, amount]
    end

    def name_for(amount)
      if amount == 1
        @name
      else
        @plural
      end
    end
  end
end