module HeadMusic::Style::Annotations
end

class HeadMusic::Style::Annotations::PreferImperfect < HeadMusic::Style::Annotation
  MESSAGE = "Use consonant harmonic intervals."

  def marks
    if ratio_of_perfect_intervals > 0.5
      HeadMusic::Style::Mark.for_all(perfect_intervals.map(&:notes).flatten)
    end
  end

  private

  def ratio_of_perfect_intervals
    return 0 if downbeat_harmonic_intervals.empty?
    perfect_intervals.length.to_f / downbeat_harmonic_intervals.length
  end

  def perfect_intervals
    downbeat_harmonic_intervals.select { |interval| interval.perfect_consonance?(:two_part_harmony) }
  end
end