# ------------------------------------------------------------------------

# coding=utf-8

# ------------------------------------------------------------------------

"""

Track the modification date for objects.

"""

import os

try:

from email.utils import parsedate_tz, mktime_tz

except ImportError: # py 2.4 compat

from email.Utils import parsedate_tz, mktime_tz

from django.db import models

from django.db.models.signals import pre_save

from django.utils.translation import ugettext_lazy as _

# ------------------------------------------------------------------------

def pre_save_handler(sender, instance, **kwargs):

"""

Intercept attempts to save and insert the current date and time into

creation and modification date fields.

"""

from datetime import datetime

now = datetime.now()

if instance.id is None:

instance.creation_date = now

instance.modification_date = now

# ------------------------------------------------------------------------

def dt_to_utc_timestamp(dt):

from time import mktime

return int(mktime(dt.timetuple()))

def register(cls, admin_cls):

cls.add_to_class('creation_date', models.DateTimeField(_('creation date'), null=True, editable=False))

cls.add_to_class('modification_date', models.DateTimeField(_('modification date'), null=True, editable=False))

if hasattr(cls, 'cache_key_components'):

cls.cache_key_components.append(lambda page: page.modification_date and str(dt_to_utc_timestamp(page.modification_date)))

cls.last_modified = lambda p: p.modification_date

pre_save.connect(pre_save_handler, sender=cls)

# ------------------------------------------------------------------------

def last_modified_response_processor(page, request, response):

from django.utils.http import http_date

# Don't include Last-Modified if we don't want to be cached

if "no-cache" in response.get('Cache-Control', ''):

return

# If we already have a Last-Modified, take the later one

last_modified = dt_to_utc_timestamp(page.last_modified())

if response.has_header('Last-Modified'):

last_modified = max(last_modified, mktime_tz(parsedate_tz(response['Last-Modified'])))

response['Last-Modified'] = http_date(last_modified)

# ------------------------------------------------------------------------