module Coltrane
  class DiatonicScale < Scale
    def initialize(tone, major: true)
      @major = major
      tone   = Note[tone]
      notes  = CircleOfFifths.new(tone - (major? ? 0 : 9), 7).notes.sort
      super notes: notes.rotate(notes.index(tone))
    end

    def name
      major? ? 'Major' : 'Natural Minor'
    end

    def relative_minor
      minor? ? self : self.class.new(@tone + 9, major: false)
    end

    def relative_major
      major? ? self : self.class.new(@tone - 9, major: true)
    end

    def relative
      major? ? relative_minor : relative_major
    end

    def major?
      !!@major
    end

    def minor?
      !@major
    end
  end
end