pedrozath/coltrane

# frozen_string_literal: true

module Coltrane
  module Theory
    # It describes a pitch, like E4 or Bb5. It's like a note, but it has an octave
    class Pitch
      include Comparable
      attr_reader :integer

      def initialize(notation_arg = nil,
                     note: nil,
                     octave: nil,
                     notation: nil,
                     frequency: nil)

        @integer = begin
          if (n = notation_arg || notation)
            n.is_a?(Integer) ? n : integer_from_notation(n)
          elsif note && octave
            integer_from_note_and_octave(Note[note], octave)
          elsif frequency
            integer_from_frequency(frequency)
          else
            raise(InvalidArgumentsError)
          end
        end
      end

      def self.[](*args)
        new *args
      end

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

      def scientific_notation
        "#{pitch_class}#{octave}"
      end

      def pitch_class
        PitchClass[integer]
      end

      def octave
        (integer / 12) - 1
      end

      alias notation scientific_notation
      alias name     scientific_notation
      alias to_s     scientific_notation

      alias hash integer
      alias midi integer

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

      def frequency
        pitch_class.frequency.octave(octave)
      end

      alias eql? ==
      alias eq ==

      def +(other)
        case other
        when Integer then Pitch[integer + other]
        end
      end

      def -(other)
        case other
        when Integer then Pitch[integer - other]
        end
      end

      private

      def integer_from_notation(the_notation)
        _, n, o = *the_notation.match(/(\D+)(\d+)/)
        integer_from_note_and_octave(Note[n], o)
      end

      def integer_from_note_and_octave(p, o)
        12 * (o.to_i + 1) + p.integer
      end

      def integer_from_frequency(f)
        octave_from_frequency(f) * 12 + PitchClass.new(frequency: f).integer
      end

      def octave_from_frequency(f)
        Math.log(f.to_f / PitchClass['C'].frequency.to_f, 2).ceil
      end
    end
  end
end