pedrozath/coltrane

# frozen_string_literal: true

module Coltrane
  module Theory
    #
    # Pitch classes, and by classes here we don't mean in the sense of a ruby class
    # are all the classes of pitches (frequencies) that are in a whole number of
    # octaves apart.
    #
    # For example, C1, C2, C3 are all pitches from the C pitch class. Take a look into
    # Notes description if you somehow feel this is confuse and that it could just be
    # called as notes instead.
    #
    class PitchClass
      attr_reader :integer
      include Comparable

      NOTATION = %w[C C# D D# E F F# G G# A A# B].freeze

      def self.all_letters
        %w[C D E F G A B]
      end

      def self.all
        NOTATION.map { |n| new(n) }
      end

      def initialize(arg = nil, frequency: nil)
        @integer = case arg
                   when String then NOTATION.index(arg)
                   when Frequency then frequency_to_integer(Frequency.new(arg))
                   when Numeric then (arg % 12)
                   when nil then frequency_to_integer(Frequency.new(frequency))
                   when PitchClass then arg.integer
                   else raise(WrongArgumentsError)
                   end
      end

      def self.[](arg, frequency: nil)
        new(arg, frequency: nil)
      end

      def ==(other)
        integer == other.integer
      end

      alias eql? ==
      alias hash integer

      def true_notation
        NOTATION[integer]
      end

      def letter
        name[0]
      end

      def ascending_interval_to(other)
        Interval.new(self, (other.is_a?(PitchClass) ? other : Note.new(other)))
      end

      alias interval_to ascending_interval_to

      def descending_interval_to(other)
        Interval.new(
          self,
          (other.is_a?(PitchClass) ? other : Note.new(other)),
          ascending: false
        )
      end

      alias name true_notation

      def pretty_name
        name.tr('b', "\u266D").tr('#', "\u266F")
      end

      def accidental?
        notation.match? /#|b/
      end

      def sharp?
        notation.match? /#/
      end

      def flat?
        notation.match? /b/
      end

      alias notation true_notation
      alias to_s true_notation

      def +(other)
        case other
        when Interval   then self.class[integer + other.semitones]
        when Integer    then self.class[integer + other]
        when PitchClass then self.class[integer + other.integer]
        when Frequency  then self.class.new(frequency: frequency + other)
        end
      end

      def -(other)
        case other
        when Interval   then self.class[integer - other.semitones]
        when Integer    then self.class[integer - other]
        when PitchClass then Interval.new(self, other)
        when Frequency  then self.class.new(frequency: frequency - other)
        end
      end

      def pitch_class
        self
      end

      def <=>(other)
        integer <=> other.integer
      end

      def fundamental_frequency
        @fundamental_frequency ||=
          Frequency[
            Theory.base_tuning *
            (2**((integer - Theory::BASE_PITCH_INTEGER.to_f) / 12))
          ]
      end

      alias frequency fundamental_frequency

      def self.size
        NOTATION.size
      end

      def size
        self.class.size
      end

      def enharmonic?(other)
        case other
        when String then integer == Note[other].integer
        when Note then integer == other.integer
        end
      end

      private

      def frequency_to_integer(f)
        begin
          (::BASE_PITCH_INTEGER +
            size * Math.log(f.to_f / Theory.base_tuning.to_f, 2)) % size
        end.round
      end
    end
  end
end