class Rack::Auth::Digest::Nonce

def self.parse(string)
  new(*Base64.decode64(string).split(' ', 2))
end

def digest
  ::Digest::MD5.hexdigest("#{@timestamp}:#{self.class.private_key}")
end

def fresh?
  !stale?
end

def initialize(timestamp = Time.now, given_digest = nil)
  @timestamp, @given_digest = timestamp.to_i, given_digest
end

def stale?
  !self.class.time_limit.nil? && (Time.now.to_i - @timestamp) > self.class.time_limit
end

def to_s
  Base64.encode64("#{@timestamp} #{digest}").strip
end

def valid?
  digest == @given_digest
end