(loop
                     (car tail)
                     (cdr tail)
                     newresult
                     (car argtail)
                     (cdr argtail)))))))))

;;======================================================================
;; M I S C   S T R I N G   S T U F F
;;======================================================================

(define (s:string-downcase str)
  (if (string? str)
      (string-translate str "ABCDEFGHIJKLMNOPQRSTUVWXYZ" "abcdefghijklmnopqrstuvwxyz")
      str)) 

;; (define session:valid-chars "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789")
(define session:valid-chars "abcdefghijklmnopqrstuvwxyz0123456789") ;; cookies are case insensitive.

;;
(define (s:crypt-passwd pw s)
  (c:crypt pw (or s (c:crypt-gensalt))))

(define (s:password-match? password crypted)
  (let* ((salt (substring crypted 0 2))
         (pcrypted (s:crypt-passwd password salt)))
    ;; (s:log "INFO: pcrypted=" pcrypted " crypted=" crypted)
    (and (string? password)
         (string? pcrypted)
         (string=? pcrypted crypted))))

;; (read-line (open-input-pipe "echo foo | mkpasswd -S ab -s"))

(define (s:error-page . err)

  (session:del! s:session "*sessionvars*" key))

(define s:session-var-delete! s:session-var-del!)

;; utility to get all vars as hash table
(define (s:session-get-sessionvars)
  (sdat-get-sessionvars s:session))

;; to obscure and indirect database ids use one time keys
;;
;;  (s:get-key 'n 1)     => "n99e1882" n=number 99e is the week number since 1970, remainder is random
;;  (s:key->val "n1882") => 1
;;
;;  first letter is a type: n=number, s=string, b=boolean
(define (s:get-key key-type val)
  (let ((mkrandstr (lambda (innum)(number->string (random innum) 16)))
	(week      (number->string (quotient (current-seconds) (* 7 24 60 60)) 16)))
    (let loop ((siz 1000)
	       (key (conc key-type week (mkrandstr 100)))
	       (num 0))
      (if (s:session-var-get key) ;; have a collision
	  (loop (cond                 ;; in the unlikey event we have trouble getting a new var, keep increasing the size of the number
		 ((< num 50)  100)
		 ((< num 100) 1000)
		 ((< num 200) 10000)
		 ((< num 300) 100000)
		 ((< num 400) 1000000) ;; can't imagine needing to get here. remember that this is for a single user
		 (else 100000000))
		(conc key-type (mkrandstr siz))
		(+ num 1))
	  (begin
	    (s:session-var-set! key val)
	    key)))))

;; given a key Xnnnn, look up the stored value and convert it appropriately, then
;; destroy the stored session var
;;
(define (s:key->val key)
  (let ((val (s:session-var-get key))
	(typ (string->symbol (substring key 0 1))))
    (if val
	(begin
	  (s:session-var-del! key)
	  ;; we take this opportunity to clean up old keyed session vars
	  ;; if more than 100 vars, remove all that are over 1-2 weeks old
					;(s:cleanup-session-vars)
	  (case typ
	    ((n)(string->number val))
	    ((s) val)
	    (else val)))
	val)))
  
;; clean up session vars
;;
(define (s:cleanup-session-vars)
  (let* ((session-vars (hash-table-keys (s:session-get-sessionvars)))
	 (week-num     (quotient (current-seconds) (* 7 24 60 60)))
	 (week         (number->string week-num  16)))
    (if (> (length session-vars) 100)
	(for-each
	 (lambda (var)
	   (if (> (string-length var) 5) ;; can't have keyed values with keys less than 5 characters long
	       (let ((var-week (string->number (substring var 1 4) 16)))
		 (if (and var-week
			  (>= (- week-num var-week) 2))
		     (s:session-var-del! var)))))
	 session-vars))))

;; inputs
;;
;; param: (dtype [tag1 tag2 ...])
;; dtype:
;;    'raw     : do no conversion
;;    'number  : convert to number, return #f if fails