Launch School challenge: Protein Translation

protein_translation.rb

class Translation

  AMINO_ACIDS = {
    'Methionine' =>     [:AUG],
    'Phenylalanine' =>  [:UUU, :UUC],
    'Leucine' =>        [:UUA, :UUG],
    'Serine' =>         [:UCU, :UCC, :UCA, :UCG],
    'Tyrosine' =>       [:UAU, :UAC],
    'Cysteine' =>       [:UGU, :UGC],
    'Tryptophan' =>     [:UGG],
    'STOP' =>           [:UAA, :UAG, :UGA]
  }

  def self.of_codon(codon)
    AMINO_ACIDS.each do |protein, codons|
      return protein if codons.include?(codon.to_sym)
    end
    raise InvalidCodonError
  end

  def self.of_rna(strand)
    polypeptide = []

    to_codons(strand).each do |codon|
      protein = Translation.of_codon(codon)

      break if protein == 'STOP'

      polypeptide << protein
    end

    polypeptide
  end


  private

  def self.to_codons(strand)
    strand.scan(/.../)
  end

end

class InvalidCodonError < RuntimeError
end

Original challenge at https://launchschool.com/gists/266be03e