gistfile1.rb

class PasswordChanger
  def initialize(account)
    @account = account
  end

  def change_password_for(user, old_password, new_password)
    unless user.authenticated?(old_password)
      raise PasswordIncorrect
    end

    # check that the passwords are different etc.

    reset_password_for(user, new_password)
  end

  # Assumes that authorization has already happened.
  def reset_password_for(user, new_password)
    unless @account.security_policy.valid_password?(new_password)
      raise PasswordInvalid
    end

    check_that_user_is_on_account(@account, user)

    do_some_logging_and_auditing(@account, user, new_password)

    user.change_password!(new_password)
  end
end