Password generator in steel scheme

password_generator.scm

(require-builtin "steel/random")

(define lowercase-chars "abcdefghijklmnopqrstuvwxyz")
(define uppercase-chars "ABCDEFGHIJKLMNOPQRSTUVWXYZ")
(define number-chars "0123456789")
(define special-chars "!@#$%^&*()_+-=[]{}|;:,.<>?")

(define (random-char str)
  (string-ref str (rng->gen-range 0 (string-length str))))

(define (shuffle-string str)
  (define len (string-length str))
  (define char-list (string->list str))
  (define (shuffle lst)
    (if (null? lst)
        '()
        (let* ((i (rng->gen-range 0 (length lst)))
               (item (list-ref lst i))
               (rest (append (take lst i) (drop lst (+ i 1)))))
          (cons item (shuffle rest)))))
  (list->string (shuffle (string->list str))))

(define (generate-password length 
                         #:use-lowercase? (use-lowercase? #t)
                         #:use-uppercase? (use-uppercase? #t)
                         #:use-numbers? (use-numbers? #t)
                         #:use-special? (use-special? #t))
  (if (< length 4)
      (error "Password length must be at least 4 characters")
      (let* (
            (initial-chars 
              (string-append
                (if use-lowercase? (string (random-char lowercase-chars)) "")
                (if use-uppercase? (string (random-char uppercase-chars)) "")
                (if use-numbers? (string (random-char number-chars)) "")
                (if use-special? (string (random-char special-chars)) "")))
            
            (char-pool 
              (string-append
                (if use-lowercase? lowercase-chars "")
                (if use-uppercase? uppercase-chars "")
                (if use-numbers? number-chars "")
                (if use-special? special-chars "")))
            
            (remaining-length (- length (string-length initial-chars)))
            (remaining-chars
              (let loop ((n remaining-length) (result ""))
                (if (zero? n)
                    result
                    (loop (- n 1) 
                          (string-append result (string (random-char char-pool)))))))
            
            ;; Combine and shuffle the password
            (final-password (shuffle-string (string-append initial-chars remaining-chars))))
        final-password)))

;; Example usage:
(display "Generated Passwords:\n")
(display "Default (all character types): ")
(display (generate-password 12))
(display "\n")

(display "Only lowercase and numbers: ")
(display (generate-password 8 
                          #:use-uppercase? #f 
                          #:use-special? #f))
(display "\n")

(display "Strong password (16 chars): ")
(display (generate-password 16))
(display "\n")