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#!/usr/bin/env python
# -*- encoding: utf-8 -*-
import re
from caldav.lib.python_utilities import to_local
## Fixups to the icalendar data to work around compatbility issues.
## TODO:
## 1) this should only be done if needed. Use try-except around the
## fragments where icalendar/vobject is parsing ical data, and do the
## fixups there.
## 2) arguably, this is outside the scope of the caldav library.
## check if this can be done in vobject or icalendar libraries instead
## of here
## TODO: would be nice with proper documentation on what systems are
## generating broken data. Compatibility issues should also be collected
## in the documentation. somewhere.
def fix(event):
"""This function receives some ical as it's given from the server, checks for
breakages with the standard, and attempts to fix up known issues:
1) COMPLETED MUST be a datetime in UTC according to the RFC, but sometimes
a date is given. (Google Calendar?)
2) The RFC does not specify any range restrictions on the dates,
but clearly it doesn't make sense with a CREATED-timestamp that is
centuries or decades before RFC2445 was published in 1998.
Apparently some calendar servers generate nonsensical CREATED
timestamps while other calendar servers can't handle CREATED
timestamps prior to 1970. Probably it would make more sense to
drop the CREATED line completely rather than moving it from the
end of year 0AD to the beginning of year 1970. (Google Calendar)
3) iCloud apparently duplicates the DTSTAMP property sometimes -
keep the first DTSTAMP encountered (arguably the DTSTAMP with earliest value
should be kept).
4) ref https://github.com/python-caldav/caldav/issues/37,
X-APPLE-STRUCTURED-EVENT attribute sometimes comes with trailing
white space. I've decided to remove all trailing spaces, since
they seem to cause a traceback with vobject and those lines are
simply ignored by icalendar.
"""
## TODO: add ^ before COMPLETED and CREATED?
## 1) Add a random time if completed is given as date
fixed = re.sub('COMPLETED:(\d+)\s', 'COMPLETED:\g<1>T120000Z',
to_local(event))
## 2) CREATED timestamps prior to epoch does not make sense,
## change from year 0001 to epoch.
fixed = re.sub('CREATED:00001231T000000Z',
'CREATED:19700101T000000Z', fixed)
fixed = re.sub(r"\\+('\")", r"\1", fixed)
## 4) trailing whitespace probably never makes sense
fixed = re.sub(' *$', '', fixed)
## 3 fix duplicated DTSTAMP
## OPTIMIZATION TODO: use list and join rather than concatination
## remove duplication of DTSTAMP
fixed2 = ""
for line in fixed.strip().split('\n'):
if line.startswith('BEGIN:V'):
cnt = 0
if line.startswith('DTSTAMP:'):
if not cnt:
fixed2 += line + "\n"
cnt += 1
else:
fixed2 += line + "\n"
return fixed2
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