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"""State and behavior for operation expiration."""

import time

from grpc.framework.core import _interfaces
from grpc.framework.core import _utilities
from grpc.framework.foundation import later
from grpc.framework.interfaces.base import base


class _ExpirationManager(_interfaces.ExpirationManager):
  """An implementation of _interfaces.ExpirationManager."""

  def __init__(
      self, commencement, timeout, maximum_timeout, lock, termination_manager,
      transmission_manager):
    """Constructor.

    Args:
      commencement: The time in seconds since the epoch at which the operation
        began.
      timeout: A length of time in seconds to allow for the operation to run.
      maximum_timeout: The maximum length of time in seconds to allow for the
        operation to run despite what is requested via this object's
        change_timout method.
      lock: The operation-wide lock.
      termination_manager: The _interfaces.TerminationManager for the operation.
      transmission_manager: The _interfaces.TransmissionManager for the
        operation.
    """
    self._lock = lock
    self._termination_manager = termination_manager
    self._transmission_manager = transmission_manager
    self._commencement = commencement
    self._maximum_timeout = maximum_timeout

    self._timeout = timeout
    self._deadline = commencement + timeout
    self._index = None
    self._future = None

  def _expire(self, index):
    def expire():
      with self._lock:
        if self._future is not None and index == self._index:
          self._future = None
          self._termination_manager.expire()
          self._transmission_manager.abort(
              _utilities.Outcome(base.Outcome.Kind.EXPIRED, None, None))
    return expire

  def start(self):
    self._index = 0
    self._future = later.later(self._timeout, self._expire(0))

  def change_timeout(self, timeout):
    if self._future is not None and timeout != self._timeout:
      self._future.cancel()
      new_timeout = min(timeout, self._maximum_timeout)
      new_index = self._index + 1
      self._timeout = new_timeout
      self._deadline = self._commencement + new_timeout
      self._index = new_index
      delay = self._deadline - time.time()
      self._future = later.later(delay, self._expire(new_index))
      if new_timeout != timeout:
        self._transmission_manager.timeout(new_timeout)

  def deadline(self):
    return self._deadline

  def terminate(self):
    if self._future:
      self._future.cancel()
      self._future = None
    self._deadline_index = None


def invocation_expiration_manager(
    timeout, lock, termination_manager, transmission_manager):
  """Creates an _interfaces.ExpirationManager appropriate for front-side use.

  Args:
    timeout: A length of time in seconds to allow for the operation to run.
    lock: The operation-wide lock.
    termination_manager: The _interfaces.TerminationManager for the operation.
    transmission_manager: The _interfaces.TransmissionManager for the
      operation.

  Returns:
    An _interfaces.ExpirationManager appropriate for invocation-side use.
  """
  expiration_manager = _ExpirationManager(
      time.time(), timeout, timeout, lock, termination_manager,
      transmission_manager)
  expiration_manager.start()
  return expiration_manager


def service_expiration_manager(
    timeout, default_timeout, maximum_timeout, lock, termination_manager,
    transmission_manager):
  """Creates an _interfaces.ExpirationManager appropriate for back-side use.

  Args:
    timeout: A length of time in seconds to allow for the operation to run. May
      be None in which case default_timeout will be used.
    default_timeout: The default length of time in seconds to allow for the
      operation to run if the front-side customer has not specified such a value
      (or if the value they specified is not yet known).
    maximum_timeout: The maximum length of time in seconds to allow for the
      operation to run.
    lock: The operation-wide lock.
    termination_manager: The _interfaces.TerminationManager for the operation.
    transmission_manager: The _interfaces.TransmissionManager for the
      operation.

  Returns:
    An _interfaces.ExpirationManager appropriate for service-side use.
  """
  expiration_manager = _ExpirationManager(
      time.time(), default_timeout if timeout is None else timeout,
      maximum_timeout, lock, termination_manager, transmission_manager)
  expiration_manager.start()
  return expiration_manager