# All plugins should include this module. It defines the basic
# operations that all plugins are supposed to support.
module Plugin

  def Plugin.included(c)
    # Callback, called whenever another class or module includes this
    # one. The parameter given is the name of the class or module
    # that included us.
    @includers ||= []
    @includers << c
  end

  def Plugin.includers
    return @includers
  end

  def describe_domain(domain)
    # Provide a "description" of the domain. This is output along
    # with the domain name and can be anything of use to the system
    # administrator.
    raise NotImplementedError
  end

  def describe_account(account)
    # Provide a "description" of the account. This is output along
    # with the domain name and can be anything of use to the system
    # administrator.
    raise NotImplementedError
  end

  def list_users()
    # Return a list of all users managed by this plugin.
    raise NotImplementedError
  end

  def list_domains_users(domains)
    # Get all usernames belonging to the given domains. If a username
    # ends in @example.com, it belongs to the domain example.com
    #
    # This uses a naive loop, but relies only on the existence of a
    # list_users() method which is guaranteed above. More efficient
    # implementations can usually be made within the plugin.
    domains_users = []

    usernames = list_users();
    domains.each do |d|
      matches = usernames.select do |username|
        username =~ /@#{d}$/
      end

      domains_users += matches
    end

    return domains_users
  end

end