arc.rb

class Arc
  def initialize(from, to)
    raise ArgumentError if invalid?(from) || invalid?(to)

    @from = from
    @to = to
  end

  def to_s
    "#{arc} degrees from #{@from} to #{@to}"
  end

  def arc
    return 360 if all_round?

    result = @to - @from
    result.negative? ? result + 360 : result
  end

  def visible?(angle)
    raise ArgumentError if invalid?(angle)
    return true if all_round?

    if @from < @to
      angle >= @from && angle <= @to
    else
      angle >= @from && angle < 360 || angle >= 0 && angle <= @to
    end
  end

  private

  def invalid?(angle)
    angle.negative? || angle > 359.9
  end

  def all_round?
    @from == @to
  end
end