A Simple First SHP

To use SHP - we should define start as follows:

(define start
(make-shp-handler "c:\\shp"))

SHP handler would then create a dispatcher based on the path, and call the appropriate script to handle the request.

A SHP page could look like:

;; index.shp
;; index.shp will be the default page displayed
;; notice we return an xexpr for this page
`(p "this is a test page")

Let's try to use the above to develop a very simple SHP handler. We want the following:

1. load the script (okay to be hardcoded for now)
2. evaluate the script into a procedure
   
3. execute the procedure and return the xexpr
   

We can accomplish the above with:

;; read all terms
(define (read-all in)
(define (helper acc)
(let ((term (read in)))
 (if (eof-object? term)
     (reverse acc)
     (helper (cons term acc)))))
(helper '()))

;; convert file into complete terms
(define (file->values path)
(call-with-input-file path read-all))

(define (make-shp-handler path)
(lambda (request)
;; let's load the request page. we'll hard code the page for now
(let ((terms (file->values (build-path path "index.shp"))))
 ;; once we loaded the page we'll conver the page's expressions into a procedure
 (let ((proc (eval `(lambda (request) . ,terms))))
   ;; then we can call the procedure.
   (proc request))
 )))

Great! We now have a trivial functional SHP system! Every request will load index.shp and reevaluate the script into a procedure to return results. Because the script gets evaluated into a scheme procedure (yes I know some of you are thinking this is dangerous... later on that topic), we can directly include inline scheme functions via quasiquotes:

;; index.shp
;; index.shp will be the default page displayed
;; notice we return an xexpr for this page
;; below will return 6
`(p "this is a test page = " ,(number->string (+ 1 2 3)))

We can use this as the basis for further development to add features, robustness, and performance, but for now this is good enough for the first shot!