; ,open srfi-13 srfi-14 ascii

(define (replace-plus-signs uri-string)
  (string-map
   (lambda (c)
     (if (char=? c #\+) #\space c))
   uri-string))

(define (decode-hex-chars uri-string)
  (call-with-current-continuation
   (lambda (esc)
     (regexp-substitute/global
      #f (rx (: #\% (= 2 any))) uri-string
      'pre
      (lambda (match)
	(cond ((regexp-search (rx (: #\% (= 2 hex-digit)))
			      (match:substring match 0))
	       => (lambda (match)
		    (string (hex->char (substring (match:substring match 0) 1 3)))))
	      (else (esc #f))))
      'post))))

(define (hex->char str)
  (ascii->char (string->number (string-append "#x" str))))

(define (decode-query query-string)
  (map 
   (lambda (argval)
     (string-tokenize 
      argval (char-set-difference char-set:full (char-set #\=))))
   (string-tokenize 
    query-string (char-set-difference char-set:full (char-set #\&)))))