#!/usr/bin/python2.5

#

# Copyright 2009 the Melange authors.

#

# Licensed under the Apache License, Version 2.0 (the "License");

# you may not use this file except in compliance with the License.

# You may obtain a copy of the License at

#

#   http://www.apache.org/licenses/LICENSE-2.0

#

# Unless required by applicable law or agreed to in writing, software

# distributed under the License is distributed on an "AS IS" BASIS,

# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

# See the License for the specific language governing permissions and

# limitations under the License.

"""Functions that are useful when dealing with timelines.

"""

__authors__ = [

  '"Lennard de Rijk" <ljvderijk@gmail.com>',

  ]

import datetime

def isBeforePeriod(entity, period):

  """Returns true iff the current DateTime is before the given period_start.

  Args:

    entity: Instance of a timeline model.

    period: The name of a period (without start or end).

  """

  return isBeforeEvent(entity, '%s_start' % period)

def isBeforeEvent(entity, event):

  """Returns true iff the current DateTime is before the given event.

  Args:

    entity: Instance of a timeline model.

    event: The name of property in the timeline model.

  """

  event_time = getDateTimeByName(entity, event)

  if event_time:

    return datetime.datetime.utcnow() < event_time

  else:

    return False

def isActivePeriod(entity, period):

  """Returns true iff the current DateTime is between period_start and period_end.

  Args:

    entity: Instance of a timeline model.

    period: The name of a period (without start or end).

  """

  period_start = '%s_start' % period

  period_end = '%s_end' % period

  period_started = isAfterEvent(entity, period_start)

  period_not_ended = isBeforeEvent(entity, period_end)

  return period_started and period_not_ended

def isAfterPeriod(entity, period):

  """Returns true iff the current DateTime is after the given period_end.

  Args:

    entity: Instance of a timeline model.

    period: The name of a period (without start or end).

  """

  return isAfterEvent(entity, '%s_end' % period)

def isAfterEvent(entity, event):

  """Returns true iff the current DateTime is after the given event.

  Args:

    entity: Instance of a timeline model.

    event: The name of property in the timeline model.

  """

  event_time = getDateTimeByName(entity, event)

  if event_time:

    return event_time < datetime.datetime.utcnow()

  else:

    return False

def getDateTimeByName(entity, name):

  """Returns the DateTime property with the given name. 

  Args:

    entity: Instance of a timeline model.

    name: The name of a specific property in the given timeline model.

  Returns:

    The requested DateTime property, or None if there is no such property set.

  """

  if hasattr(entity, name):

    return getattr(entity, name)

  else:

    return None