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"""Interfaces defined and used by the base layer of RPC Framework."""

import abc

# packets is referenced from specifications in this module.
from _framework.base import interfaces
from _framework.base.packets import packets  # pylint: disable=unused-import


class ForeLink(object):
  """Accepts back-to-front tickets and emits front-to-back tickets."""
  __metaclass__ = abc.ABCMeta

  @abc.abstractmethod
  def accept_back_to_front_ticket(self, ticket):
    """Accept a packets.BackToFrontPacket.

    Args:
      ticket: Any packets.BackToFrontPacket.
    """
    raise NotImplementedError()

  @abc.abstractmethod
  def join_rear_link(self, rear_link):
    """Mates this object with a peer with which it will exchange tickets."""
    raise NotImplementedError()


class RearLink(object):
  """Accepts front-to-back tickets and emits back-to-front tickets."""
  __metaclass__ = abc.ABCMeta

  @abc.abstractmethod
  def accept_front_to_back_ticket(self, ticket):
    """Accepts a packets.FrontToBackPacket.

    Args:
      ticket: Any packets.FrontToBackPacket.
    """
    raise NotImplementedError()

  @abc.abstractmethod
  def join_fore_link(self, fore_link):
    """Mates this object with a peer with which it will exchange tickets."""
    raise NotImplementedError()


class Front(ForeLink, interfaces.Front):
  """Clientish objects that operate by sending and receiving tickets."""
  __metaclass__ = abc.ABCMeta


class Back(RearLink, interfaces.Back):
  """Serverish objects that operate by sending and receiving tickets."""
  __metaclass__ = abc.ABCMeta
