We're getting closer to using a new streamlined protocol with Cosmo,
and it's now a good time to re-examine what network operations
Chandler performs when given a URL to subscribe to. Below is a first
pass at the pseudo code for an initial subscribe. One problem with
this code is that Cosmo currently responds to a GET on a CalDAV
calendar with an icalendar file of all the contained events, and thus
if Chandler follows this algorithm it won't be able to subscribe to a
Cosmo collection in CalDAV mode (Chandler would simply treat the
collection as a monolithic ical file). Chandler, upon receiving a
monolithic ical file in response to the GET, will need to do
something extra to see if there's really a CalDAV calendar hiding
behind the ical file.
I've left out the logic for determining whether the user has write-
permission, but I believe I read that we can do some sort of ticket
discovery to ask Cosmo what the permissions are for a given ticket.
Is that true? I suppose in the case where there is no ticket
provided we can assume we have write-permission; if a write does fail
during the first sync then consider the share read-only. On the
other hand, at that point it's too late because the user may have
made some modifications to the items. So really, if there is no
ticket involved, I will have to perform the same trick I am currently
doing which is to MKCOL a temporary subcollection to verify write-
permission at the time of initial subscribe. Does that work for non-
Cosmo CalDAV servers?
subscribe
-------------
if url has a ticket in it:
ticket = url's ticket
username = password = None
else:
ticket = None
if there is a sharing account that corresponds to the url:
username = account.username
password = account.password
done = False
while True:
try:
response = GET(url, ticket, username, password)
except NetworkError, e:
# This could include problems such as not being able to connect to
the server, or not being able to look up
# a server's IP address
return appropriate error
if response.status == NotAuthorized:
return NotAuthorized # the UI code will prompt the user for
username and password and try again
elif response.status == OK:
if response.contenttype == "text/html":
if real sharing URL is embedded in response.body:
url = embedded sharing url
continue # back up to the top of the while loop
else: # this is some random HTML file
return ThisIsJustAnHTMLFile # What should the
UI do?
elif response.contenttype == "application/icalendar": # is that
the right contenttype value?
# response.body has the icalendar text
Set up Share objects for simple monolithic ical
subscription
share.sync(body=response.body) # no need to fetch the body again,
pass it directly to sync
return Success
# Note: the problem with this is that Cosmo returns a big
icalendar file when the client does a
# GET of a CalDAV calendar collection, and therefore Chandler
won't be able to subscribe to
# such a collection in CalDAV mode unless we do something
different here.
elif response.contenttype == "application/eim+xml":
# response.body has EIM records
Set up Share objects for morsecode subscription
share.sync(body=response.body) # no need to fetch the body again,
pass it directly to sync
return
else:
return UnknownContentType
elif response.status == MethodNotAllowed:
# perhaps this is a CalDAV collection that doesn't allow GET?
set up Share objects for CalDAV subscription
share.sync( )
return
else: # deal with other response.status values, such as NotFound
return appropriate error
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