karaoke_machine.rb

class KaraokeMachine
  OCTAVE = %w(C C# D D# E F F# G G# A A# B)
  def initialize(melody)
    @melody = melody
  end

  def transpose(t)
    transposed = transpose_octave(t)
    @melody.gsub(/[A-G]#?/) do |m|
      transposed[m]
    end
  end

  private
  def transpose_octave(t)
    transposed = OCTAVE.rotate(t)
    Hash[*OCTAVE.zip(transposed).flatten]
  end
end

describe KaraokeMachine do
  it "メロディ無し" do
    melody = ""
    answer = melody
    expect(KaraokeMachine.new(melody).transpose(0)).to eq answer
  end
 
  # ここから下のコメントを外していって、テストを全部パスさせてください！
 
  it "変更無し" do
    melody = "C D E F |E D C   |E F G A |G F E   |C   C   |C   C   |CCDDEEFF|E D C   "
    answer = melody
    expect(KaraokeMachine.new(melody).transpose(0)).to eq answer
  end
  
  it "2上げる" do
    melody = "C D E F |E D C   |E F G A |G F E   |C   C   |C   C   |CCDDEEFF|E D C   "
    answer = "D E F# G |F# E D   |F# G A B |A G F#   |D   D   |D   D   |DDEEF#F#GG|F# E D   "
    expect(KaraokeMachine.new(melody).transpose(2)).to eq answer
  end
  
  it "7上げる" do
    melody = "C D E F |E D C   |E F G A |G F E   |C   C   |C   C   |CCDDEEFF|E D C   "
    answer = "G A B C |B A G   |B C D E |D C B   |G   G   |G   G   |GGAABBCC|B A G   "
    expect(KaraokeMachine.new(melody).transpose(7)).to eq answer
  end
  
  it "1下げる" do
    melody = "C D E F |E D C   |E F G A |G F E   |C   C   |C   C   |CCDDEEFF|E D C   "
    answer = "B C# D# E |D# C# B   |D# E F# G# |F# E D#   |B   B   |B   B   |BBC#C#D#D#EE|D# C# B   "
    expect(KaraokeMachine.new(melody).transpose(-1)).to eq answer
  end
  
  it "7下げる" do
    melody = "C D E F |E D C   |E F G A |G F E   |C   C   |C   C   |CCDDEEFF|E D C   "
    answer = "F G A A# |A G F   |A A# C D |C A# A   |F   F   |F   F   |FFGGAAA#A#|A G F   "
    expect(KaraokeMachine.new(melody).transpose(-7)).to eq answer
  end
  
  it "1オクターブ上げる" do
    melody = "C D E F |E D C   |E F G A |G F E   |C   C   |C   C   |CCDDEEFF|E D C   "
    answer = melody
    expect(KaraokeMachine.new(melody).transpose(12)).to eq answer
  end
  
  it "1オクターブ下げる" do
    melody = "C D E F |E D C   |E F G A |G F E   |C   C   |C   C   |CCDDEEFF|E D C   "
    answer = melody
    expect(KaraokeMachine.new(melody).transpose(-12)).to eq answer
  end
  
  it "14上げる" do
    melody = "C D E F |E D C   |E F G A |G F E   |C   C   |C   C   |CCDDEEFF|E D C   "
    answer = "D E F# G |F# E D   |F# G A B |A G F#   |D   D   |D   D   |DDEEF#F#GG|F# E D   "
    expect(KaraokeMachine.new(melody).transpose(14)).to eq answer
  end
  
  it "13下げる" do
    melody = "C D E F |E D C   |E F G A |G F E   |C   C   |C   C   |CCDDEEFF|E D C   "
    answer = "B C# D# E |D# C# B   |D# E F# G# |F# E D#   |B   B   |B   B   |BBC#C#D#D#EE|D# C# B   "
    expect(KaraokeMachine.new(melody).transpose(-13)).to eq answer
  end
  
  it "2オクターブ上げる" do
    melody = "C D E F |E D C   |E F G A |G F E   |C   C   |C   C   |CCDDEEFF|E D C   "
    answer = melody
    expect(KaraokeMachine.new(melody).transpose(24)).to eq answer
  end
  
  it "2オクターブ下げる" do
    melody = "C D E F |E D C   |E F G A |G F E   |C   C   |C   C   |CCDDEEFF|E D C   "
    answer = melody
    expect(KaraokeMachine.new(melody).transpose(-24)).to eq answer
  end
  
  it "26上げる" do
    melody = "C D E F |E D C   |E F G A |G F E   |C   C   |C   C   |CCDDEEFF|E D C   "
    answer = "D E F# G |F# E D   |F# G A B |A G F#   |D   D   |D   D   |DDEEF#F#GG|F# E D   "
    expect(KaraokeMachine.new(melody).transpose(26)).to eq answer
  end
  
  it "25上げる" do
    melody = "C D E F |E D C   |E F G A |G F E   |C   C   |C   C   |CCDDEEFF|E D C   "
    answer = "B C# D# E |D# C# B   |D# E F# G# |F# E D#   |B   B   |B   B   |BBC#C#D#D#EE|D# C# B   "
    expect(KaraokeMachine.new(melody).transpose(-25)).to eq answer
  end
  
  it "6上げる(メロディはF#から開始)" do
    melody = "F# G# A# B |A# G# F#   |A# B C# D# |C# B A#   |F#   F#   |F#   F#   |F#F#G#G#A#A#BB|A# G# F#   "
    answer = "C D E F |E D C   |E F G A |G F E   |C   C   |C   C   |CCDDEEFF|E D C   "
    expect(KaraokeMachine.new(melody).transpose(6)).to eq answer
  end
  
  it "6下げる(メロディはF#から開始)" do
    melody = "F# G# A# B |A# G# F#   |A# B C# D# |C# B A#   |F#   F#   |F#   F#   |F#F#G#G#A#A#BB|A# G# F#   "
    answer = "C D E F |E D C   |E F G A |G F E   |C   C   |C   C   |CCDDEEFF|E D C   "
    expect(KaraokeMachine.new(melody).transpose(-6)).to eq answer
  end
  
  it "連続してtransposeを呼び出す" do
    melody = "C D E F |E D C   |E F G A |G F E   |C   C   |C   C   |CCDDEEFF|E D C   "
    karaoke = KaraokeMachine.new(melody)
  
    answer = melody
    expect(karaoke.transpose(0)).to eq answer
  
    answer = "D E F# G |F# E D   |F# G A B |A G F#   |D   D   |D   D   |DDEEF#F#GG|F# E D   "
    expect(karaoke.transpose(2)).to eq answer
  
    answer = "B C# D# E |D# C# B   |D# E F# G# |F# E D#   |B   B   |B   B   |BBC#C#D#D#EE|D# C# B   "
    expect(karaoke.transpose(-1)).to eq answer
  end
end