~launchpad-pqm/launchpad/devel

Calendars

=========

Some objects in Launchpad have calendars.  Actually, currently only persons

(and teams) have calendars, but it is planned to add them to products and

projects as well.

Calendaring code makes use of the SchoolBell library (Python package

`schoolbell`), which comes from the SchoolTool project (www.schooltool.org).

Launchpad calendars have some additional attributes such as title and owner,

defined in the ILaunchpadCalendar interface (that extends schoolbell's

IEditCalendar).  Calendars are stored in the PostgreSQL database.

Hooking up calendars to objects

-------------------------------

Objects that have calendars can be adapted to ILaunchpadCalendar.

There is an adapter registered for ICalendarOwner that returns the

'calendar' attribute of an object, so the simplest thing for adding a

calendar to an object is to make sure this attribute exists, and

declare that the object provides ICalendarOwner.

There is a view named '+calendar' registered for ICalendarOwner, so if

an object (e.g. a person) that has a calendar can be reached at a

certain URL, accessing the calendar of that object is just a matter of

going to URL + '/+calendar'.

There is also a view named 'calendar' registered for the root object.

This view provides a merged view of the calendars the user has

subscribed to.

There is a set of views available for ICalendar, and a traverser that

interprets URL segments as dates.

Interoperability with calendaring clients

-----------------------------------------

Every calendar can be exported as an iCalendar file via HTTP.  You can

subscribe to these calendars from Mozilla Calendar (or Sunbird), Evolution,

KOrganizer, Apple's iCal, etc.  The get the URL for getting an iCalendar file

just append '/calendar.ics' to the calendar URL, e.g.

   http://localhost:8085/foaf/persons/test/calendar/calendar.ics

The ability to upload iCalendar files (and thus modify calendars stored in

Launchpad from these calendaring clients) is not hooked up yet.  There is

an iCalendar parser in the schoolbell module, but the tricky part is to get

Zope 3 traversal (which is heavily customized in Launchpad) to actually

work for HTTP PUT requests.

Security

--------

All calendars are readable by everyone.  Write access is restricted to

the calendar owner.  The calendar owner is taken from the calendar's

parent:

  * if the calendar belongs to a team, then it is owned by the team's

    owner.

  * if the calendar belongs to a person, then it is owned by the

    person.

  * project and product calendars are owned by their respective

    owners.

TODO

----

- Re-add recurring event support (it was disabled to make prototyping

  easier).  SchoolBell interfaces currently define the recurrence rule

  as a single attribute providing one of four recurrence rule

  interfaces; perhaps it can be simulated with a property.  Or perhaps

  SchoolBell's interfaces aren't general enough and could be changed

  to be more convenient.  Talk to me (Marius Gedminas,

  <marius@pov.lt>) if you have ideas.

- Write and hook up the iCalendar upload view (HTTP PUT requests).

  Writing it should be easy -- use

  schoolbell.icalendar.read_icalendar().  Hooking it up is difficult

  (see the description above).

   * After discussion, it has been decided not to provide webcal://

     write access.

If you have any questions about the schoolbell library or calendaring in

Launchpad, feel free to email Marius Gedminas <marius@pov.lt>.