gistfile1.rb

def lookup(reference, authenticable = true)
  return reference if !reference or reference.is_a? User
  base = self

  if reference.is_a? Numeric or (reference.is_a? String and reference.match(/^\d+$/))
    user = base.find(reference.to_i)
  elsif reference.include? '@'
    user = base.find_by_email(reference) ||
      base.find_by_hashed_email(User.hash_email(reference)) || base.find_by_identifier(reference)
  else
    user = base.find_by_login(reference) || base.find_by_identifier(reference)
  end

  (user && (!authenticable || user.can_login?)) ? user : nil
end