Fun with Simple Fab Apps (in v0.5)

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I got over the hump with the new version (0.5) of fab.js. Tonight I would like to sanity check myself with what Jed describes as the very simplest v0.5 (fab) apps.

Again tonight, I will be using a fairly simple skeleton (fab) application:

// Don't crash on errors
process.on('uncaughtException', function (err) {
  console.log('Runaway exception: ' + err.stack);
});

with ( require('fab') )

( fab )

  // Listen on the FAB port
  ( listen, 0xFAB )

  (prepend_hello)
  (simplest_app)
  (prepend_hello)
  ()

();

function prepend_hello(write) {
  return function read(body) {
    return write(" hello ")(body);
  };
}

The prepend_hello() (fab) app will prepend the text " hello " to the current stream, which ought to aid in seeing what is happening.

First up, the simplest possible app, which should pass the stream back downstream:

function simplest_app(write) {
  return write;
}

When I access the server via curl, I see:

cstrom@whitefall:~$ curl http://localhost:4011/ -d Foo
 hello  hello 

Ah, interesting. I would have expected the write to short-circuit the stream, ignoring the last prepend_hello. Instead it does nothing—connecting the two streams, making no changes.

Next, I replace the simplest_app with the second simplest app:

function second_simplest_app(write) {
  return write( "foo" );
}

Accessing the server via curl, I see:

cstrom@whitefall:~$ curl http://localhost:4011/ -d Foo
 hello foo hello 

Given the behavior of the simplest app, the behavior of the second simplest app is to be expected.

Last up tonight, I wonder how I might grab downstream body data. Ultimately, I am stumped. I can obtain the request header info with:

function read_from_downstream(write) {
  return write( function read(write, obj, hunh) {
    if (obj.body) return write(obj.body);
    return write(obj.url.pathname);
  });
}

But I am stumped how to re-read from the downstream app so that I could access the request body. From curl, I get:

curl http://localhost:4011/ -d Foo 
 hello / hello 

Ultimately, I am not too concerned. Fab is going to be changing quite a bit in the upcoming days, so this will get sorted out.

Day #221