libgcal 0.9.4 released

Sweet! But what the heck is this ‘libgcal’ thingie? For starts, the name can and is misleading, since it should read as ‘library for google calendar’ but in reality, it implements both Contacts and Calendar google data protocol.

When I got it started, back in February of 2008, it was supposed to implement just calendar, but later on I realized that adding contact support only required +25% of code on it (thanks for well modular software design). Back then,  there was no other good alternative for any C/C++ programmer that would fit the following requirements:

• easy to use;
• well documented;
• few dependencies;

So, I got my library started! After studying the google data protocol 1.0 (at the time) for while, I realized that using XPath would make my life way easier than say, browsing through the DOM tree searching for the attributes and tags that I wanted.

At that time, Qt didn’t have support for XPath (it only started with 4.5), so I went with libxml. For networking I used libcurl, which is fast/reliable and has great documentation (and a very welcoming community, from time to time I asked for help and always got answers for my questions).

From the very early beginning, I set a high quality standard in the development (after all, parsing XML in C is already prone to errors by itself) and followed a TDD (Test Driven Development) approach where *first* I write the test and *later* write the implementation of functions. Having an average of test coverage of 80% helped a lot when google released version 2.0 of the protocol (back in december 2008) and now more recently, version 3.0 of Contact’s protocol. I did the porting from version 1.0 to version 2.0 of the protocol in few hours, mostly because I could detect any regression by simply running the test suites.

IIRC in about 4 months I got the basic (authenticate, retrieve, add/edit/delete, query for updates) done and the library even got featured in the google official blog (that was surprising to say the least)!

So, the library was ‘done’, let’s put it to good use. I decided to integrate it with Opensync (it was rather cool, I got google contacts and calendar sync for my Nokia N95 over bluetooth working 6 months before google decided to release a syncml server for S60 devices). You can see a pre-jurassic video of this here. I think up until now libsyncml is a pretty good syncml implementation, it is just a shame that there is not a good UI bounded to it.

But I needed a good UI and the alternative seemed to write an akonadi resource. In just 3 weeks I got contacts working, while also implementing missing features in libgcal to make possible to do fast-sync (i.e. when you download only what has changed in server side). Contacts resource was done in just 3 days (I think this is clearly a good signal that akonadi API is well designed).

Developing the akonadi resources gave the opportunity to better understand how KDE community works and also to start running KDE trunk as my default desktop (after all, pre-packaged software are for sissies and developers should eat their own dog food).

So, why I wrote all this story? Well, to help to understand some numbers:

• 10 months ……. since last release (0.9.3)
• 6 distros ………. pre-packages libgcal (Debian, Ubuntu, OpenSuse, Gentoo, Mandriva, FreeBSD) and counting
• 2326 downloads .. directly from libgcal project website (hey, this is a source code tarball of a library and not some porn!)
• 20681 views …… reported by google analytics in a 1 year period
• 3000 ms……… the lag to ping google servers in a bad day in Manaus/Amazonas (yeah, truly it is unbeliavable how I managed to write a *networking* library in this enviroment but what doesn’t kill you makes you stronger)
• 6762 LOC ……. lines of C code (34% are unit tests)
• 76.5 % ……… current *real* code coverage (here I slipped a bit, it used to be 80%)
• 10th ……….. of most wanted KDE features

So, what this new release brings? For start, support for multiple email addresses, patch by Stefano Avallone (Andre Loureiro helped to fix the unit test) and migration to Google Contacts API 3.0. Next, support for structured names and several other fields (nickname, blog, etc) by Holger Kral. I think currently only IM field is missing from the library (but is quite easy to implement that).

You can have access to both the library and the akonadi resource in libgcal website. The only issue is that is required to purge your akonadi resource and do a slow-sync again because the ETags and urls of contacts have changed thanks to migration to version 3.0 of protocol.

So, what is missing in the library for a 1.0 release? The following features:

• support multiple calendars (easy to do, is a matter of using another URL as base to do the network operations)
• support recurrent events in calendar (thanks to the fact that google uses an invalid iCal to represent it, it gets tricky to implement it since a iCal parser would fail to read this data). An idea to implement this would be to ‘convert’ the invalid iCal from google to a valid one and do the opposite when sending data back to the google server.
• batch commit (nice to have, but not a hard requirement)
• port/rewrite it all to Qt (seriously, this was actually started already: http://code.google.com/p/libgdata-cpp/). Here I’m somewhat unsure, if Qt has support for the XPath/XQuery in Symbian (it seems that RTTI is not supported in this OS).

Oh well… so, why not give it a try? If you got the skills, go on and download the sources (please check the README and INSTALL files) and feel free to report to me how things worked (or not…).

If you are a normal user, I think in a couple of weeks it should get packaged for your loved distro.