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router is an in-memory trie based path router for Erlang.
It can be used to route paths to destinations. It has single-level,
and multi-level wildcard levels.

It can be used for arbitrary path/hierarchical based routing, and you
can have multiple independent routers.


Create a new router like this:

   Router = router:new()

This creates multiple ets tables which are owned by the calling process. It
is advised to call this inside a gen_server.

Now you can add routes like this:

   router:add(Router, [<<"a">>, <<"b">>], MyDestination),

This creates a route from path ```<<"a">>, <<"b">>``` to the information inside 
'MyDestination'. It is important that routes are added synchronized. It is best
to do it inside a handle_call or handle_cast of a single gen_server.

After this it is possible to route request paths to destinations:

  Routes = router:route(Router, [<<"foo">>, <<"bar">>]),

Calls to ```route``` can be called in parallel.


Router has two different wildcards, multi-level and single-level wildcards.

The following wildcards are implemented:

- ```'+'```, matches one level on the path.
- ```{'+', test}```, matches one level on the paths and binds the path element to test.
- ```{'+', test, {module, function}}```, matches the element on the path if the call
  to ```module:function(PathElement)``` returns true.

There is one multi-level wildcard ```'#'``` which matches all elements on the path.

Example single-level wildcard route:

   router:add(Router, [<<"rsc">>, {'+', id}], {controller_rsc, [{foo, <<"bar">>]})

When you now call ```router:route(Router,[<<"rsc">>, <<"12312">>])```, you get a list
with route tuples with all matching destinations and the list of bound variables in a
proplist. In this case: ```[{route, {controller_rsc, [{foo, <<"bar">>}]}, [{id, <<"12312">>}]```.

You get a list of matching destinations, and all elements which are bound in a proplist
as result.

Example multi-level wildcard route:


    router:add(Router, [<<"truck">>, <<"00001">>, '#'], self())

This will match all routes to ```[<<"truck">>, <<"00001">>]``` and all its sub paths. For 
example: ```[<<"truck">>, <<"00001">>, <<"temperature">>]``` will match and also 
```[<<"truck">>, <<"00001">>, <<"location">>]```.