Re: [Chicken-users] Starting up spiffy for dynamic content

[Peter Bex]

On Tue, Mar 08, 2016 at 02:48:00PM +0000, Norman Gray wrote:
> Peter, hello.
> 
> Thanks for these clarifications.

You're welcome.

> So you mean including handlers like:
> 
> (define (vhost-handler cont)
>   (let ((uri (uri-path (request-uri (current-request)))))
>     (if (string=? (cadr uri) "wibble") ;; we want to handle URIs
> like /wibble/...
>         (send-response status: 'ok
>                        body: (format "<p>Good: request was ~S
> (vhost)</p>" uri)
>                        headers: '((content-type text/html)))
>         (cont))))
> (vhost-map `((".*" . ,vhost-handler)))

That's how it was intended, yes.  I've added something similar to the
wiki with a link to slightly extended (but somewhat outdated) example
from a demonstration.

The introduction does mention in passing that you'd add custom path
handlers to the vhost-map.

> OK: that's a (very) nice design -- I'll do that.
> 
> But may I suggest that vhost-map is not, perhaps, the best name for
> this structure, since the intended functionality is much more
> general than mapping vhosts.  As I mentioned, I guessed that might
> be a route to the solution, but based on the name, on the fact it's
> documented in a section called 'Virtual hosts', and since the
> example in that section is about handling virtual hosts, I got the
> impression that the author was firmly steering me away from more
> open-ended cleverness.  Caolan suggested that I'm not (thankfully)
> alone in misinterpreting this.

Well, it is a mapping for which handler to use for which vhost.  That
is also the topmost place where dispatching happens for incoming
requests, so it's the place where you'd add custom handlers.

I could add some intermediate parameter like "request-handler", which
then defaults to some procedure that handles the request like the
current implementation does (try to serve a file), but it would be
one more level of indirection which is basically just what "continue"
does now.

Would that be sensible?

> Perhaps dispatch-handler-map, or handler-map, or something like
> that, would signal the intent more clearly, along with an example
> such as the above.

Not sure that would be much clearer.  Also, it would break compatibility.

> Since the car of the alist is a host pattern,
> then perhaps the word 'host' should be in the name, but in that case
> perhaps handle/host might be suitable (and if anything's being
> changed, then it might be nice to have a clear catch-all host
> pattern, such as #t, or to permit the list elements to be a
> continuation thunk as well as a string-thunk pair).  Thus:
> 
> (handle/host
>   `(,my-general-handler
>    ("foo\\.bar\\.com" . ,(lambda (continue) ...))
>    (#t . ,my-catch-all-handler))

I think that would only complicate things, and cause more confusion
as to the format of this list.

> Some preconceptions, yes, but I've used enough frameworks such as
> this to make sure that I keep such preconceptions pretty
> lightweight, so they're merely a guide as a search for how the
> system wants to be used.  I thus did find vhost-map quickly, but the
> documentation appeared to be telling me I was in the wrong place.

It's a wiki, feel free to improve the wording in places where it's
unclear.  I've been using Spiffy for too long to see these missing
pieces.

> Thanks again for the illumination.

No problem!

Cheers,
Peter

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