class Sensitive
  alias_method :eql?, :==
  alias_method :equal?, :==

  def initialize(v, ch: "*", head: 2, tail: 2)
    @v = v
    @ch = ch
    @head = head
    @tail = tail
  end

  def mask(v)
    +"".concat(v[0, @head], @ch * (v.length - (@head + @tail)), v[-@tail, @tail])
  end

  def unwrap
    @v
  end

  def length
    @v.length
  end

  def to_s
    mask @v
  end

  def inspect
    "#<#{self.class.name} @v=#{wrap}>"
  end

  def hash
    @v.hash
  end

  def ==(other)
    other.is_a?(Sensitive) && other.hash == hash
  end
end