Orbit 2.1.0’s dispatcher now accepts anything that answers to a match method for its routing patterns and returns a list of captures, instead of just strings that it interprets as standard Lua patterns. This means that you can now easily plug other kinds of pattern matchers, with the caveat that you only have the PATH_INFO available for matching.
As an example, I made a plugin for having Sinatra-like routes in your Orbit application, available here for Orbit 2.1.0 and through this rockspec if you have Git installed and want to track the bleeding edge of Orbit. It has as much of the Sinatra routes as I could understand from their test file: named parameters delimited by slashes or dots, splats delimited by slashes or dots, and optional named parameters. The test_routes.lua script is a good example of what is available.
This is “Hello World” example of how you can use this in an Orbit application:
You need to have LPEG installed, just a matter of luarocks install lpeg.
The implementation essentially compiles routes to an LPEG pattern that receives a string and a table for putting the extracted params, and if the string matches fills this table and returns it; otherwise it returns nil. The entry point for the compiler is the route pattern. It splits the route definition into parameters, optional parameters, splats and literals, then builds the final pattern using a foldr), because splats have to match everything up to the rest of the route definition.
As an optimization, the compiler builds two patterns instead of one, a “clean” pattern, that does not capture anything, used to make evaluation of PEG predicates (for the splats) faster, and a “capture” pattern that does the actual work (and is the final result).
I am thinking of exposing the WSAPI environment to the pattern matchers, so you can write routing plugins that can match on the query string or on HTTP headers. This would also let me refactor Orbit to decouple the dispatcher from the creation of the web objects. Sounds cool, but I have to think how actually useful this would be!