;; The first three lines of this file were inserted by DrScheme. They record metadata
;; about the language level of this file in a form that our tools can easily process.
#reader(lib "htdp-advanced-reader.ss" "lang")((modname 10a) (read-case-sensitive #t) (teachpacks ()) (htdp-settings #(#t constructor repeating-decimal #t #t none #f ())))
;; constants: 
(define OL "OL")
(define UL "UL")
(define Mt "Mt")
(define OneItem "OneItem")
(define ConsItem "Cons")
(define StringItem "EString")

;; -----------------------------------------------------------------------------
;; String [Listof String] -> String 
;; create a new expression 
(check-expect (new ConsItem '("a" "b")) "new ConsItem(a, b)")
(define (new class fields)
  (string-append "new " class "(" (separate-with-commas fields) ")"))

;; String -> String 
;; create new StingItem (watch!)
(check-expect (newStringItem "a") (new StringItem '("\"a\"")))
(define (newStringItem x) (new StringItem (list (format "~s" x))))

;; [Listof String] -> String 
;; convert a Scheme list into an Item list 
(check-expect 
 (list->list '("a" "b" "c")) 
 (new ConsItem `("a" ,(new ConsItem `("b" ,(new ConsItem `("c" ,(new Mt '()))))))))
#;
(check-expect (list->list '("a" "b" "c")) 
              (new ConsItem `("a" ,(new ConsItem `("b" ,(new OneItem '("c")))))))
(define (list->list ls)
  (foldr (lambda (i r) (new ConsItem (list i r))) (new Mt '()) ls)
  #;
  (foldr (lambda (i r) (new ConsItem (list i r))) (new OneItem (list (last ls)))
         (all-but-last ls)))

;; Nat String -> [Listof String]
;; make a list of n string items 
(check-expect 
 (a-list 2 "a") 
 (new ConsItem (list (newStringItem "a1000") 
                     (new ConsItem (list (newStringItem "a1001")
                                         (new Mt '()))))))

(define (a-list n s)
  (list->list
   (build-list 
    n (lambda (i) (newStringItem (string-append s (number->string (+ i 1000))))))))

;; [Listof String] -> String 
;; separate the items with commans, combine into one string 
(check-expect (separate-with-commas '("a" "b" "c")) "a, b, c")
(define (separate-with-commas l)
  (if (empty? l) 
      ""
      (foldr (lambda (f r) (string-append f ", " r)) (last l) (all-but-last l))))

;; libraries 
(define (last l) (first (reverse l)))
(define (all-but-last l) (reverse (rest (reverse l))))
;; -----------------------------------------------------------------------------

(define (deep n)
  (cond
    [(zero? n) (new OL (list (a-list 3 "level0")))]
    [else (new UL `(,(new ConsItem 
                          `(,(newStringItem `(,(format "header ~a" n)))
                            ,(new ConsItem 
                                  `(,(deep (sub1 n))
                                    ,(a-list n (format "level ~a" n))))))))]))


(define (main n)
  (display (format "~a" (deep n))))
                    

(main 6)