New backend for org-agenda: (Was Calendar-like view of the org-agenda)

[SAKURAI Masashi <m.sakurai@kiwanami.net>]

Hi Bastien,

At Fri, 08 Jul 2011 10:53:08 +0200,
Bastien wrote:
> :
> > the re-design of the whole org-agenda-list algorithm
> > seems to be needed, because the key function
> > org-agenda-get-day-entries requires only one date and the subsequent
> > dependent functions also are designed by the API.
> 
> FWIW, I'm all ears -- if you have ideas on how to make org-agenda-list
> more effective please let us know, I could try to implement them.

How about caching of schedule items?
My idea is as follows.

When one query schedule items for the first time, the backend parses
the org buffer and stores all schedule items with a buffer local
variable.  From the next time of the query, the backend can use the
cache data without parsing the buffer text.

Then, because The backend has a model of schedule items, in addition
to org-agenda-get-day-entries, we can define some useful API for
schedule items, such as org-agenda-get-entries-by-range(begin end).

I illustrated this idea:
[Diagram for caching schedule items]
https://cacoo.com/diagrams/RcNaxILLHDGZlr1L#4B823

Org schedule seems to consist of two types, simple items and repeat
items. So, I think that the backend should execute two type queries.

[Query and Data Structure]
https://cacoo.com/diagrams/RcNaxILLHDGZlr1L#C071E

Of course, because I have used orgmode not so long time, this idea is
not useful or too simple to handle the org schedules. 


Here are other implementations:

The Howm schedule API (howm-reminder-search) enumerates all schedule
items. The API user can filter them easily. However, the enumeration
employs full-text searching using grep command, so it takes a long
time to be done the query.  calfw-howm.el has a cache data and the
user can refresh it explicitly.

Another schedule API is CalDAV. This is a specification for the
schedule server, such as Apple iCal server and Google Calendar.

[Calendaring Extensions to WebDAV (CalDAV) RFC 4791]
http://www.webdav.org/specs/rfc4791.html
http://en.wikipedia.org/wiki/CalDAV

This specification has many API for query. It is very heavy spec, but
I think it may be a hint for designing query API for orgmode schedule
items.


Regards
--
SAKURAI, Masashi (family, given)
m.sakurai@kiwanami.net