3 posts tagged “appjet”

When I posted about lib-flickr-minimal, I noted that the newly-launched flickr.places.placesForUser method made a more interesting demo of data you could fetch when authenticated than, say, showing a user's most recent private photos. Evidently the developers at Flickr agreed it was an interesting concept, because over the last couple of months that area of the API has been extended considerably, As a result, I've expanded the demo into an AppJet application of its own.

Where? What? When? is the result. It shows you, on a map, the locations with the most photos according to a given criterion: by default, that's a tag, but it can also show your photos, or those from your friends and family, or your contacts. You can then inspect a place and see the most recent relevant photos, or the most popular tags, for that location.

How did that evolve from the initial demo app? Instead of simply printing a table based on Flickr's response into the document, I directly plotted the results on the map. I added a small form to enable the choice of criteria, and when Flickr added the placesForTags method, I added that as a choice. Belatedly, I realised that would also work for users without authentication, so I removed the requirement to authenticate, and made tags the logged-out default. (The image above shows a slight change to the initial results: it's the same tag, London, but at the neighbourhood, not locality, level. All of the locations are within the greater city's area, which probably won't be a surprise, but that's not true for Paris. Evidently, what happens in Vegas doesn't always stay there.)

The design of the application isn't quite settled, but I knew I wanted to replace the standard Google Maps pushpins with partially-transparent circles. Initially, I went with red, but when I showed it to colleagues, they said it reminded them of maps of bomb blast radii, so I spent a while looking around for the right colour, before settling on a yellow. The circles themselves are scaled according to the natural log of the number of photos for that location; I played with square roots as well, but I feel that logarithms give the right sense of scale.

The last piece of work I did was adding tag display for locations, using the tagsForPlace method. These tags can be surfed: clicking on one will load a new search for the given tag. It's noticable that the first few tags for most places are almost always place names, while common tags seem to share a familiar pattern of scattered, similarly-sized circles across the US, Europe, south-east Asia and coastal Australia.

There's still a few things I could add; tag persistence in URLs (to make it easier to share pages), better loading indicators (especially initially), options on which photos are shown, and links to view the search on Flickr itself, for example. There's also a missing question: while the API methods support maximum and minimum times, I haven't yet added options to allow you to show When? However, for now I think I've done enough (and I'll note that the site has a link to view the source of the application, if you fancy hacking on it yourself.) Enjoy.

groupr (my little JavaScript application that gives users an overview of their Flickr group membership) needs to be able to communicate with Flickr. That's really not hard; getting the most recent public photos posted by a user can be done trivially, either using feeds or the API proper.

However, most of the calls that you need to write really interesting applications require authentication, so that they can see private data. Rather than use the password antipattern, Flickr uses a well-thought-out multi-step system. Unfortunately, this can be a bit tricky to wrap your head around, and harder still to debug. It was certainly something I spent a while grappling with for groupr. That's the main reason I've split out the parts of groupr that talk to Flickr into a library on AppJet called lib-flickr-minimal.

As the name suggests, the library doesn't actually do that much. There are methods to handle the steps of authentication, and there's a generic function to call any Flickr method. However, it's more than enough for me to write both groupr, and a little demo application that guides other users through the process of handling authentication.

(A little on that demo application. I spent a few minutes trying to think of a method that required read privileges that would not be too obvious and dull ("you have 500 private photos", for example). Thankfully I remembered the recently-launched flickr.places.placesForUser method, and so I decided to use that as my example call. A bit more work meant I could plot the places returned onto a Google map, so now you can see where you've taken (or at least, geotagged) the most photos.

Ideally I'd rewrite this to produce something prettier, like Dopplr's lovely raumzeitgeist images, but for now, it's a nice little one-page example.)

Philosphically, I prefer this style of library. There seem to be two schools of thought when it comes to building such things. You can tell from the source of the library that I'm in the  "least possible work" camp: provide helpers for the functions that are tricky, but for most calls, let the user consult Flickr's documentation to figure out what to call, and use JSON as a return format to make everything that you get back an object (or at least, a rich data structure).

The other camp, which I think of as being influenced by Java and other less dynamic languages, wants to provide a method for everything. As a result their implementations tend to have lots of boilerplate code for handling every single Flickr method (there are about a hundred now), and more for parsing the returned XML (rarely, if never, JSON) and add to it convenience methods for such things as constructing URLs.

While the latter style is probably superficially appealing (you get documents in one place, and the library can error-check locally) it also has significant drawbacks. When Flickr add a method, or extend the returned data, the library has to be patched and re-released. Many libraries only implement the methods of interest to the author, leaving chunks of the API unimplemented. (These are particularly annoying for me; they tend to implement flickr.photos.search, which seems to be the cornerstone of the Flickr API, but ignore the interesting methods around the edges, which I seem to be drawn to.)

There is a nice middle way, which is to use metaprogramming and the API's own reflection methods to construct a list of allowed calls and arguments, giving  error-checking but also updating automatically when Flickr add methods. The libraries I prefer for both Python and Ruby do this, and very nice they are too.

To be honest, this is probably where I want lib-flickr-minimal to end up, but for now, I'll happily take a library that stays out of my way rather than one that aims to do everything but only implements a few things. Hopefuly others on AppJet, or those looking to implement Flickr authentication, will find it useful too.

Long-time readers here may remember groupr. (If you don't, it was a small web application that loaded the photos in your Flickr groups, something that, oddly, you can't do on Flickr itself.) I wrote it at the beginning of 2007 for Fotango's Zimki platform. Of course, when that died at the end of last year, groupr vanished, but not before I took a backup of the code and templates underlying it, in the hope that one day I might be able to revive it.

For a few different reasons, I've been considering bringing groupr back recently. I could use Google's App Engine, as I've done for snaptrip, but that was from scratch, and for this project, I didn't fancy porting both the code and templates. I had a quick look at Helma and Trimpath, but I didn't get on with either of them. There's also the fact that they they're not hosted solutions, and part of the joy of server-side JavaScript (SSJS) is not having to worry about finding a server. I also tried Reasonably Smart, but you have to be pretty clever to get git working, and I couldn't, so that was out.

Eventually I found AppJet, and after a quick look I was convinced that this was probably a good place to end up, and after about eight hours to port what I had, and another five or so to fix up some things I never quite polished off on the old version, you can now use groupr.appjet.net.

So, how does it compare to Zimki, and how hard was it to port the code? (After all, big names are now talking about portability in the cloud). Well, AppJet may be closed source, but they offer a downloadable JAR which ran without any effort for me on Mac OS X, meaning both that I could develop locally (even offline, with cached data), and that if AppJet vanishes (which, after all, happened to Zimki) I can take groupr and run it on a server of my own. In this case, practicality trumps theoretical openness.

AppJet's IDE feels a lot nicer than Zimki's did (although I barely use (or used) either, preferring BBEdit with AppJet's JAR, or Trawler for Zimki). I also approve of the way that libraries are handled (they're just apps whose name includes the 'lib-' prefix) is pretty nice. You can see what is using a library and there's provision for inline documentation too. The community feels bigger than Zimki's ever did (although that might just be because the idea of SSJS is taking off), and I was able to find a few useful libararies (such as a TrimPath template port) pretty easily. Speaking of libaries, AppJet's 'storage' is oddly non-core, but it's a pretty nice row-style store with nice querying facilities. It lacks Zimki's handy "expires:+2h" syntax, but that wasn't too hard to fit in myself.

One definite annoyance I have with AppJet is that they don't keep all their libraries out of the global namespace. Zimki's functionality was all hidden in a zimki object, but AppJet has a few top-level standard libraries, and 'page' and 'response' both clashed with names I was using in groupr's previous version. Another is that there's no way of handling non-JavaScript files, so both static files and templates are tricky. I've ended up with the former being hosted on my main server, and the latter as a hash of triple-quoted strings (a Python-ism that AppJet has imported into their JS runtime). Proper file support, like Zimki had, would be a boon there. However, both of these were pretty easy to overcome, and it turned out Zimki did very little that AppJet couldn't replicate. (Replacing the (Mojo, I believe) API calls was four lines of jQuery; replacing the server-side API cleverness, for my needs, was a few lines of JSON.)

Overall, then, I think I'm pretty happy with my experience so far. I've managed to revive the project without too much hair-pulling, and, as I said, even extended it from the state it was in on Zimki. Maybe server-side JavaScript has a future after all?