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#!/usr/bin/env gsi-script
; File: "web-server.scm", Time-stamp: <2008-12-17 13:41:03 feeley>
; Copyright (c) 2004-2008 by Marc Feeley, All Rights Reserved.
; A minimal web server which implements a web-site with a few
; interesting examples.
;==============================================================================
(##include "~~lib/gambit#.scm") ;; import Gambit procedures and variables
(##include "http#.scm") ;; import HTTP procedures and variables
(##include "html#.scm") ;; import HTML procedures and variables
(##include "base64#.scm") ;; import BASE64 procedures and variables
(declare (block)) ;; required for serializing continuations
;; (for the web-continuation example)
;==============================================================================
(define main
(lambda (arg)
(let ((port-number
(string->number arg)))
(http-server-start!
(make-http-server
port-number: port-number
threaded?: #t
GET: GET/POST
POST: GET/POST)))))
(define page-generators (make-table test: string=?))
(define show-exceptions
(lambda (thunk)
(with-exception-catcher
(lambda (exc)
(reply-html
(<html>
(<head> (<title> "Scheme exception"))
(<body>
(<p> "The following Scheme exception occurred while processing the request:")
(<pre>
(call-with-output-string
""
(lambda (port) (##display-exception exc port))))))))
thunk)))
(define GET/POST
(lambda ()
(show-exceptions
(lambda ()
(let* ((request (current-request))
(uri (request-uri request))
(path (uri-path uri))
(generator (table-ref page-generators path unknown-page)))
(generator))))))
(define unknown-page
(lambda ()
(let* ((request (current-request))
(uri (request-uri request))
(path (uri-path uri)))
(get-filesys-path path))))
(define get-filesys-path
(lambda (path)
(let ((type (file-type path)))
(case type
((directory)
(reply-html
(<html>
(<head> (<title> "Files in directory " path))
(<body>
(<h1> "Files in " path)
(<ol>
(map (lambda (fn)
(<li>
(<a> href: (object->string (path-expand fn path)) fn)
" ("
(object->string
(with-exception-catcher
(lambda (exc) 'other)
(lambda () (file-type (path-expand fn path)))))
")"))
(directory-files
(list path: path ignore-hidden: #f))))))))
((regular)
(let* ((port (open-input-file path))
(file (read-line port #f)))
(close-input-port port)
(let ((ext (path-extension path)))
(if (or (string-ci=? ext ".htm")
(string-ci=? ext ".html"))
(reply (lambda () (display file)))
(reply-html
(<html>
(<head> (<title> "File " path))
(<body> (<pre> file))))))))
(else
(reply-html
(<html>
(<head> (<title> "Error"))
(<body>
"Only directories and regular files can be displayed"))))))))
;==============================================================================
; Main web page.
(define page-main
(lambda ()
(reply-html
(<html>
(<head> (<title> "Main page"))
(<body>
(<center> (<b> "Welcome to the " (<i> "web-server") " example"))
(<p> "Please choose one of these examples:")
(<ul>
(<li> (<a> href: (object->string (current-directory))
"Browse the web server's filesystem"))
(<li> (<a> href: "/web-continuation"
"Web-continuation based calculator"))
(<li> (<a> href: "/terminate-server"
"Terminate server"))))))))
(table-set! page-generators "/" page-main)
(table-set! page-generators "/index.html" page-main)
(table-set! page-generators "/index.htm" page-main)
;==============================================================================
; Web pages for web-continuation example.
(define page-web-continuation
(lambda ()
(obtain-store-cont-on-server title-embed)))
(table-set! page-generators "/web-continuation" page-web-continuation)
(define page-calculator
(lambda ()
; check if we are resuming a continuation or starting the example
(let* ((request (current-request))
(query (request-query request)))
(cond ((and query (assoc "cont" query))
=>
(lambda (x)
; we're resuming a continuation
(resume-continuation (cdr x) query)))
((and query (assoc "submit" query))
=>
(lambda (x)
; we're starting the calculator
(let* ((x (assoc "store_cont_on_server" query))
(on-server? (and x (string=? (cdr x) "yes"))))
(parameterize ((store-cont-on-server? on-server?))
(calculator-start)))))
(else
(reply-html
(<html>
(<head> (<title> "Error"))
(<body>
(<h1> "Something's wrong with the request...")))))))))
(table-set! page-generators "/calculator" page-calculator)
; BUG: parameters lose their identity when serialized/deserialized so
; we can't store this information in a parameter.
(define store-cont-on-server? (make-parameter #f))
(define calculator-start
(lambda ()
(let ((new-number
(show-sum-and-obtain-number
'()
first-number-embed)))
(calculator-loop (list new-number)))))
(define calculator-loop
(lambda (numbers-previously-entered)
(let ((new-number
(show-sum-and-obtain-number
numbers-previously-entered
plain-embed)))
(calculator-loop (append numbers-previously-entered
(list new-number))))))
(define show-sum-and-obtain-number
(lambda (numbers-previously-entered embed)
(let ((sum (apply + numbers-previously-entered)))
(obtain-number
(lambda (stuff)
(embed
(<table>
(if (null? numbers-previously-entered)
'()
(list
(map (lambda (x)
(<tr> (<td>)
(<td> align: 'right x)))
numbers-previously-entered)
(<tr> (<td>)
(<td> align: 'right "---------------------"))
(<tr> (<td> "TOTAL:")
(<td> align: 'right bgcolor: "yellow" sum))))
(<tr> (<td>)
(<td> stuff)))))))))
(define title-embed
(lambda (stuff)
(<html>
(<head> (<title> "Web-continuation example"))
(<body>
(<h1> "Web-continuation example")
(<p> "This page implements a simple calculator that adds the "
"numbers that are entered by the user.")
(<p> "You can use the " (<strong> "back") " button to undo the "
"additions. You can also clone the window and copy "
"the URL to a different browser to start an independent "
" branch of calculation.")
(<p> "The web-server can be run interpreted or compiled. It is "
"much more efficient to use a compiled web-server because "
"the continuations in the HTML file sent back to the browser "
"will be much more compact.")
(<p> "Please indicate if you want the continuation to be stored "
"on the web browser or on the web server. It is more "
"efficient to store the continuation on the server but it "
"introduces the problem of web-continuation garbage-collection "
"(each continuation will be saved as a file on the server's file "
"system; the issue is: when can these files be deleted?)")
stuff))))
(define first-number-embed
(lambda (stuff)
(<html>
(<head> (<title> "Web-continuation example"))
(<body>
(<h1> "Web-continuation example")
(<p> "Enter the first number here: " stuff)))))
(define plain-embed
(lambda (stuff)
(<html>
(<head> (<title> "Web-continuation example"))
(<body>
(<h1> "Web-continuation example")
stuff))))
(define form-method "GET") ; can be "GET" or "POST"
(define obtain-number
(lambda (embed)
(let ((number-str
(obtain
"number"
(lambda (cont)
(embed
(<form>
action: "/calculator"
method: form-method
(<input> type: 'hidden
name: "cont"
value: cont)
(<input> type: 'text name: "number")
(<input> type: 'submit
name: "submit"
value: "ADD")))))))
(or (string->number number-str)
(obtain-number embed)))))
(define obtain-store-cont-on-server
(lambda (embed)
(obtain
"store_cont_on_server"
(lambda (cont) ; continuation is ignored
(embed
(<form>
action: "/calculator"
method: form-method
(<input> type: 'checkbox
name: "store_cont_on_server"
value: "yes"
"Store continuation on server")
(<input> type: 'submit
name: "submit"
value: "\"START CALCULATOR\"")))))))
(define obtain
(lambda (name embed)
(let ((query
(capture-continuation
(lambda (cont)
(reply-html (embed cont))
(thread-terminate! (current-thread))))))
(cdr (assoc name query)))))
(define capture-continuation
(lambda (receiver)
(call/cc
(lambda (k)
(let* ((k-str
(u8vector->base64-string (object->u8vector k)))
(cont
(if (store-cont-on-server?)
(let loop () ; find a unique filename
(let* ((rn (random-integer (expt 2 64)))
(fn (string-append "_cont"
(number->string rn 16))))
(if (file-exists? fn)
(loop)
(begin
(with-output-to-file fn
(lambda ()
(display k-str)))
fn))))
k-str)))
(receiver cont))))))
(define resume-continuation
(lambda (cont val)
(let* ((k-str
(if (and (> (string-length cont) 0)
(char=? (string-ref cont 0) #\_))
(with-input-from-file cont read-line)
cont))
(k
(u8vector->object (base64-string->u8vector k-str))))
(k val))))
;==============================================================================
; Web-IDE page.
(define page-web-ide
(lambda ()
(reply-html
(<html>
(<head>
(<title> "Web-IDE page")
(<style> web-ide-style)
(<script> web-ide-script))
(<body>
(<p> "This example is not complete"))))))
(table-set! page-generators "/web-ide" page-web-ide)
(define web-ide-style #<<EOF
web ide style
EOF
)
(define web-ide-script #<<EOF
web ide script
EOF
)
;==============================================================================
; Web-server termination.
(define page-terminate-server
(lambda ()
(exit)))
(table-set! page-generators "/terminate-server" page-terminate-server)
;==============================================================================
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