rx-request-handler

Rx Request Handler
==================
This is an Rx request handler meant to work with the rx-router module. This
version leverages a middleware format that was inspired by Clojure's ring
specification.

The previous middleware implementation was effectively a modeling of unix
pipes done with Rx. This version of middleware still leverages Rx but it
lets you model a flow similar to a call stack. To visualize the difference
check out the following ascii scribbles.

Previous pipe based middleware implementation:
``
Request
|
V
------------------ -------------- -------------------
| Authentication | - -\ | Controller | --\ | Caching |
| pre-middleware | - -/ | action | --/ | post-middleware |
------------------ -------------- -------------------
|
V
Response
`

Current ring spec based middleware implementation:
`
Request
|
V
------------------ -------------- --------------
| Authentication | --> | Caching | --> | Controller |
| middleware | <-- | middleware | <-- | action |
------------------ -------------- --------------
|
V
Response
`

The previous implementation forced every middleware to choose whether it was
a pre-action or post-action middleware. This creates nasty state passing
situations in the cases where you need to coordinate between a pre-action and
post-action middleware.

The new ring spec based implementations allows each middleware to choose whether
it wants to be a pre-action, post-action middleware or even both. This enables
the middleware to fully encapsulate all of it's state and gets rid of the need
to attach middleware specific state to the data object flowing through the
request cycle.

Example
-------
`javascript
var Rx = require("rx");
var RxHttpServer = require("rx-http-server");
var router = require("rx-router");
var handler = require("rx-request-handler");

var defaultHandler = handler(function(data) {
data.result = "no match found";
return Rx.Observable.fromArray([data]);
});

var preAction = function(next) {
return function(data) {
data.result = "[pre] ";
return Rx.Observable.returnValue(data).flatMap(next);
};
};

var postAction = function(next) {
return function(data) {
return next(data).map(function(n) {
n.result += " [post]"
return n;
});
};
};

var rootHandler = handler({

middleware: [
preAction,
postAction
],

action: function(data) {
data.result += "hello";
return Rx.Observable.fromArray([data]);
}

});

var regexHandler = handler(function(data) {
data.result = "hello from regex";
return Rx.Observable.fromArray([data]);
});

var server = new RxHttpServer();
var routes = router(defaultHandler, {
"GET": [
["/", rootHandler],
[/^\/test\/.+/, regexHandler]
]
});

server.requests.flatMap(routes).subscribe(function(data) {
data.response.writeHead(200, {"Content-Type": "text/plain"});
data.response.end(data.result);
});

server.listen(3000);
``