" title "

#lang racket/base (require "uri-codec.rkt") (provide ;; -- exceptions raised -- (struct-out cgi-error) (struct-out incomplete-%-suffix) (struct-out invalid-%-suffix) ;; -- cgi methods -- get-bindings get-bindings/post get-bindings/get output-http-headers generate-html-output generate-error-output bindings-as-html extract-bindings extract-binding/single get-cgi-method ;; -- general HTML utilities -- string->html generate-link-text) ;; 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-string->string : string -> string ;; -- The input is the string 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-string->string form-urlencoded-decode) ;; 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")) ;; delimiter->predicate : symbol -> regexp ;; returns a regexp to read a chunk of text up to a delimiter (excluding it) (define (delimiter->rx delimiter) (case delimiter [(amp) #rx#"^[^&]*"] [(semi) #rx#"^[^;]*"] [(amp-or-semi) #rx#"^[^&;]*"] [else (error 'delimiter->rx "internal-error, unknown delimiter: ~e" delimiter)])) ;; get-bindings* : iport -> (listof (cons symbol string)) ;; Reads all bindings from the input port. The strings are processed to ;; remove the CGI spec "escape"s. ;; This code is _slightly_ lax: it allows an input to end in ;; (current-alist-separator-mode). 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. ;; ELI: * Keeping this behavior for now, maybe better to remove it? ;; * Looks like `form-urlencoded->alist' is doing almost exactly ;; the same job this code does. (define (get-bindings* method ip) (define (err fmt . xs) (generate-error-output (list (format "Server generated malformed input for ~a method:" method) (apply format fmt xs)))) (define value-rx (delimiter->rx (current-alist-separator-mode))) (define (process str) (query-string->string (bytes->string/utf-8 str))) (let loop ([bindings '()]) (if (eof-object? (peek-char ip)) (reverse bindings) (let () (define name (car (or (regexp-match #rx"^[^=]+" ip) (err "Missing field name before `='")))) (unless (eq? #\= (read-char ip)) (err "No binding for `~a' field." name)) (define value (car (regexp-match value-rx ip))) (read-char ip) ; consume the delimiter, possibly eof (retested above) (loop (cons (cons (string->symbol (process name)) (process value)) bindings)))))) ;; get-bindings/post : () -> bindings (define (get-bindings/post) (get-bindings* "POST" (current-input-port))) ;; get-bindings/get : () -> bindings (define (get-bindings/get) (get-bindings* "GET" (open-input-string (getenv "QUERY_STRING")))) ;; 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 ""))