Enigma machine

plugboard.rb

class Plugboard

  def initialize(wires = '')
    @wires = wires
    validate unless @wires.empty?
  end

  def validate
    return raise "wire error" unless @wires.is_a?(String)
    return raise "wire error" if @wires.chars.uniq!
    return raise "wire error" if @wires.chars.size > 20
    return raise "wire error" unless @wires.chars.size.even?
  end

  def process(wire)
    enigma = {}
    @wires.chars.each_with_index{|item, index| enigma[item] = @wires.chars[(index + 1)] unless index.odd?}
    enigma[wire] || enigma.select { |key, value| value == wire }.keys[0] || wire
  end

end