"""
Utilities for event-driven programming.

$Id$

Copyright (C) 2009  Internet Systems Consortium ("ISC")

Permission to use, copy, modify, and distribute this software for any
purpose with or without fee is hereby granted, provided that the above
copyright notice and this permission notice appear in all copies.

THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
PERFORMANCE OF THIS SOFTWARE.
"""

import rpki.log

class iterator(object):
  """Iteration construct for event-driven code.  Takes three
  arguments:

  - Some kind of iterable object

  - A callback to call on each item in the iteration

  - A callback to call after the iteration terminates.

  The item callback receives two arguments: the callable iterator
  object and the current value of the iteration.  It should call the
  iterator (or arrange for the iterator to be called) when it is time
  to continue to the next item in the iteration.

  The termination callback receives no arguments.
  """

  def __init__(self, iterable, item_callback, done_callback):
    self.item_callback = item_callback
    self.done_callback = done_callback
    try:
      self.iterator = iter(iterable)
    except:
      rpki.log.debug("Problem constructing iterator for %s" % repr(iterable))
      raise
    self()

  def __call__(self, *ignored):
    try:
      self.item_callback(self, self.iterator.next())
    except StopIteration:
      if self.done_callback is not None:
        self.done_callback()