#lang scheme/unit
(require "cgi-sig.ss" "uri-codec.ss")
(import)
(export cgi^)
;; type bindings = list ((symbol . string))
;; --------------------------------------------------------------------
;; Exceptions:
(define-struct cgi-error ())
;; chars : list (char)
;; -- gives the suffix which is invalid, not including the `%'
(define-struct (incomplete-%-suffix cgi-error) (chars))
;; char : char
;; -- an invalid character in a hex string
(define-struct (invalid-%-suffix cgi-error) (char))
;; --------------------------------------------------------------------
;; query-chars->string : list (char) -> string
;; -- The input is the characters post-processed as per Web specs, which
;; is as follows:
;; spaces are turned into "+"es and lots of things are turned into %XX, where
;; XX are hex digits, eg, %E7 for ~. The output is a regular Scheme string
;; with all the characters converted back.
(define (query-chars->string chars)
(form-urlencoded-decode (list->string chars)))
;; string->html : string -> string
;; -- the input is raw text, the output is HTML appropriately quoted
(define (string->html s)
(apply string-append
(map (lambda (c)
(case c
[(#\<) "<"]
[(#\>) ">"]
[(#\&) "&"]
[else (string c)]))
(string->list s))))
(define default-text-color "#000000")
(define default-bg-color "#ffffff")
(define default-link-color "#cc2200")
(define default-vlink-color "#882200")
(define default-alink-color "#444444")
;; generate-html-output :
;; html-string x list (html-string) x ... -> ()
(define (generate-html-output title body-lines
[text-color default-text-color]
[bg-color default-bg-color]
[link-color default-link-color]
[vlink-color default-vlink-color]
[alink-color default-alink-color])
(let ([sa string-append])
(for ([l `("Content-type: text/html"
""
""
""
""
,(sa "" title "")
""
""
,(sa "")
""
,@body-lines
""
""
"")])
(display l)
(newline))))
;; output-http-headers : -> void
(define (output-http-headers)
(printf "Content-type: text/html\r\n\r\n"))
;; read-until-char : iport x char -> list (char) x bool
;; -- operates on the default input port; the second value indicates whether
;; reading stopped because an EOF was hit (as opposed to the delimiter being
;; seen); the delimiter is not part of the result
(define (read-until-char ip delimiter)
(let loop ([chars '()])
(let ([c (read-char ip)])
(cond [(eof-object? c) (values (reverse chars) #t)]
[(char=? c delimiter) (values (reverse chars) #f)]
[else (loop (cons c chars))]))))
;; read-name+value : iport -> (symbol + bool) x (string + bool) x bool
;; -- If the first value is false, so is the second, and the third is true,
;; indicating EOF was reached without any input seen. Otherwise, the first
;; and second values contain strings and the third is either true or false
;; depending on whether the EOF has been reached. The strings are processed
;; to remove the CGI spec "escape"s. This code is _slightly_ lax: it allows
;; an input to end in `&'. It's not clear this is legal by the CGI spec,
;; which suggests that the last value binding must end in an EOF. It doesn't
;; look like this matters. It would also introduce needless modality and
;; reduce flexibility.
(define (read-name+value ip)
(let-values ([(name eof?) (read-until-char ip #\=)])
(cond [(and eof? (null? name)) (values #f #f #t)]
[eof?
(generate-error-output
(list "Server generated malformed input for POST method:"
(string-append
"No binding for `" (list->string name) "' field.")))]
[else (let-values ([(value eof?) (read-until-char ip #\&)])
(values (string->symbol (query-chars->string name))
(query-chars->string value)
eof?))])))
;; get-bindings/post : () -> bindings
(define (get-bindings/post)
(let-values ([(name value eof?) (read-name+value (current-input-port))])
(cond [(and eof? (not name)) null]
[(and eof? name) (list (cons name value))]
[else (cons (cons name value) (get-bindings/post))])))
;; get-bindings/get : () -> bindings
(define (get-bindings/get)
(let ([p (open-input-string (getenv "QUERY_STRING"))])
(let loop ()
(let-values ([(name value eof?) (read-name+value p)])
(cond [(and eof? (not name)) null]
[(and eof? name) (list (cons name value))]
[else (cons (cons name value) (loop))])))))
;; get-bindings : () -> bindings
(define (get-bindings)
(if (string=? (get-cgi-method) "POST")
(get-bindings/post)
(get-bindings/get)))
;; generate-error-output : list (html-string) ->
(define (generate-error-output error-message-lines)
(generate-html-output "Internal Error" error-message-lines)
(exit))
;; bindings-as-html : bindings -> list (html-string)
;; -- formats name-value bindings as HTML appropriate for displaying
(define (bindings-as-html bindings)
`(""
,@(map (lambda (bind)
(string-append (symbol->string (car bind))
" --> "
(cdr bind)
"
"))
bindings)
""))
;; extract-bindings : (string + symbol) x bindings -> list (string)
;; -- Extracts the bindings associated with a given name. The semantics of
;; forms states that a CHECKBOX may use the same NAME field multiple times.
;; Hence, a list of strings is returned. Note that the result may be the
;; empty list.
(define (extract-bindings field-name bindings)
(let ([field-name (if (symbol? field-name)
field-name (string->symbol field-name))])
(let loop ([found null] [bindings bindings])
(if (null? bindings)
found
(if (equal? field-name (caar bindings))
(loop (cons (cdar bindings) found) (cdr bindings))
(loop found (cdr bindings)))))))
;; extract-binding/single : (string + symbol) x bindings -> string
;; -- used in cases where only one binding is supposed to occur
(define (extract-binding/single field-name bindings)
(let* ([field-name (if (symbol? field-name)
field-name (string->symbol field-name))]
[result (extract-bindings field-name bindings)])
(cond
[(null? result)
(generate-error-output
(cons (format "No binding for field `~a':
" field-name)
(bindings-as-html bindings)))]
[(null? (cdr result))
(car result)]
[else
(generate-error-output
(cons (format "Multiple bindings for field `~a' where one expected:
"
field-name)
(bindings-as-html bindings)))])))
;; get-cgi-method : () -> string
;; -- string is either GET or POST (though future extension is possible)
(define (get-cgi-method)
(or (getenv "REQUEST_METHOD")
(error 'get-cgi-method "no REQUEST_METHOD environment variable")))
;; generate-link-text : string x html-string -> html-string
(define (generate-link-text url anchor-text)
(string-append "" anchor-text ""))