Router-Fu is a modern router for your web application. Traditional routers match on the url and render components, templates or pages but a Router-Fu router matches on the url and outputs state. The application is able to treat route state like any other application state.

The core component of the system is the Route. A Route is a named pattern against which urls can be matched against. The pattern also identifies parameters that are extracted from the url and potentially constraints that each pattern must be validated against. The Route also has the ability to construct a url given a set of parameters.

A typical route may be represented by "/:function/:org_context/event/:eventId" and would extract the function, org_context and eventId parameters from any url that matches the above.

If a url is matched by a Route and the parameters satisfy the constraints then a RouteMatchCallback is invoked on the Route that can perform custom behaviour and returns an enum that indicates whether the match was:

• no-match. i.e. Further validation of the parameters identified the route as non-matching.
• terminal. i.e. The match was successful and no more routes need to be matched.
• non-terminal. i.e. The match was successful but continue to attempt to match more routes.

The Router is an ordered list of routes. During routing a path is passed to the Router that walks through each Route in order, until a terminal route is identified or there are no more routes. For each route matched a RouteState is created that contains the Route matched, the parameters extracted from the route and whether the route was "terminal". The routing method on the Router returns a Location which contains an ordered list of RouteState instances.

The Router also exposes the routes so that application code can generate paths for the route given a set of parameters. It also provides methods via which the application can request that the location be changed.

The Location object is effectively immutable and can easily be passed to other frameworks that have their own state management tools. In an Arez, it would expected that you wrap the Location to make it observable.

• Stock Software for providing significant support in building and maintaining the library, particularly at it's inception.

• This toolkit drew inspiration from troch/path-parser and router5.