The mirror of the import from #173, and the last thing contacts had that
calendars did not -- an address book could always be exported, a calendar
never could.
It is written here rather than asked for. The import hands parsing to the
server because Stalwart has a CalendarEvent/parse and reimplementing an .ics
reader in a browser would be foolish; there is no method the other way, in
Stalwart or in the JMAP calendar drafts, so the file is built from the RFC
8984 objects the server already returns. Most of that is renaming: 8984 was
written as a restatement of 5545, and the comments say which way it went
wherever the two disagree.
The masters, not the occurrences. The query runs without expandRecurrences,
so a weekly meeting leaves as one VEVENT carrying its RRULE rather than as a
year of identical ones -- an export that had flattened the rule would import
somewhere else as a pile nobody can maintain. A changed occurrence goes out
as its own VEVENT with the same UID and a RECURRENCE-ID, which is how
iCalendar has always said it; a cancelled one becomes an EXDATE.
Three decisions worth stating rather than leaving to be found:
No VTIMEZONE components. A TZID names the IANA zone the server holds and
nothing defines it beside it, because defining it means shipping a zone
database to describe rules the reader's own system already knows. Every
client that matters resolves IANA names. The alternative -- converting to
UTC -- would be worse than a validator's complaint: a weekly 09:00 that
becomes 08:00 for half the year is a wrong calendar.
UNTIL follows DTSTART's kind, a date for an all-day series and a UTC instant
otherwise. Sending a local time there is the usual way to make a series stop
a day early in another timezone.
Overrides are applied at the top level only. A recurrence override is a JSON
patch, and one addressing locations/x/name is not something this flattens.
Closes#216.
A timetable, a rota, a public holiday list: the calendars people are given
as a link, which ihasmail could not show at all.
Nothing is stored. The document is fetched when the calendar is opened and
parsed in the browser; the server keeps no copy, no cache and no schedule,
which is what lets an immutable container serve this. There is no timer
either -- there is nowhere to run one -- so the guarantee is that a
subscription is as current as the last time somebody looked, which is also
when it matters. That is said plainly rather than implied.
The fetch has to happen on the server: a calendar URL belongs to whoever
published it and almost none of them send CORS headers. That makes it the
second place this app knocks on a door somebody else chose, so the guard
the image proxy has always had was lifted out and both now call it. A
second SSRF implementation is how one of them ends up missing a case; this
way there is one, and the extraction is covered by the image proxy's own
tests still passing unchanged.
webcal: is understood, because that is how these are published, and it is
read as https: rather than waved past the checks -- a webcal URL pointing
at loopback is refused exactly like an http one.
Recurrence is deliberately not expanded. RRULE is a small language with a
lot of edge cases, and a subscription quietly showing the wrong dates would
be worse than one showing the first occurrence and saying so.
The parser is a subscription parser rather than an importer: a subscribed
calendar is read-only and redrawn from scratch each refresh, so nothing has
to round-trip or survive an edit, which is most of what makes a full
iCalendar implementation large. What it does have to do is never mis-state
a time -- a DATE is built in local time rather than at UTC midnight, which
would land on the day before for anyone west of Greenwich -- and never hang
on a document somebody else wrote.
Events go through instancesIn like the birthdays, so no view has to know
they are not real calendars, and the calendar they hang off reports no
write rights, so everything that asks before offering an edit declines on
its own. A subscription that cannot be read says so in the sidebar rather
than drawing an empty calendar, which looks like a calendar with nothing
in it.
jcoffey-dev