; The File-system Data Design:

(define-struct file [name size write? exec?])

; A File is a (make-file String Nat Boolean Boolean)
; a file in a directory structure:
; - a name
; - a size in Bytes
; - 2 permission bits: the file is writeable/executable
(define f-t (make-file "thomas.jpg"        1200 #f #f))
(define f-j (make-file "john.jpg"          1400 #f #f))
(define f-n (make-file "nicole.jpg"        1300 #f #f))
(define f-r (make-file "drracket"       1000000 #f #t))
(define f-c (make-file "2500-grades.xls"  10000 #t #f))
(define (file-templ file)
  (... (file-name   file) ...
       (file-size   file) ...
       (file-write? file) ...
       (file-exec?  file) ...))

(define-struct dir [name entries])

; A Dir is a (make-dir String [List-of Entry])
; a directory
(define d-0 (make-dir "Empty" '())) ; that's all we can do at this point!
(define (dir-templ dir)
  (... (dir-name dir) ...
       (loe-templ (dir-entries dir)) ...))

; An Entry is one of File or Dir
; a file or a directory
(define e-0 f-t)
(define (entry-templ entry)
  (... (cond [(file? entry) (... (file-templ entry) ...)]
             [(dir?  entry) (... (dir-templ  entry) ...)]) ...))

(define d-p (make-dir "Personal" (list f-t)))
(define d-r (make-dir "Racket"   (list f-r)))
(define d-c (make-dir "Course"   (list f-c)))
(define d-t (make-dir "Wahl"     (list d-p d-r d-c)))
(define d-j (make-dir "Park"     (list f-j)))
(define d-b (make-dir "Brewer"   (list f-n)))
(define d-h (make-dir "Home"     (list d-t d-j d-b)))

; The Page Data Design:

(define-struct page [title links])
     
; A Page is a (make-page String [List-of String])
; a web page's title and links to other pages.
(define page-0 (make-page "Khoury"        (list "NEU")))
(define page-1 (make-page "NEU"           (list "Khoury" "Boston")))
(define page-2 (make-page "Boston"        (list "NEU" "Shillman Hall")))
(define page-3 (make-page "Shillman Hall" (list "NEU")))
(define page-4 (make-page "New Orleans"   (list "Mardi Gras")))
(define (page-templ p)
  (... (page-title p) ...
       (los-templ (page-links p)) ...)) ; note: los-templ instead of lop-templ!
(define (los-templ los)
  (... (cond [(empty? los) ...]
             [(cons?  los) ... (first los)
                           ... (los-templ (rest los))])))

; A Wiki is a [List-of Page]
; a list of webpages (like the Internet)
(define wiki-0 (list page-0 page-1 page-2 page-3 page-4))

; page-links-by-title : String Wiki -> [List-of String]
; the list of page names linked to from the given page,
; or () if page not found
(check-expect (page-links-by-title "Boston" wiki-0) (list "NEU" "Shillman Hall"))
(check-expect (page-links-by-title "NOPAGE" wiki-0) '())
(define (page-links-by-title t wiki)
  (cond [(empty? wiki)                          '()]
        [(string=? (page-title (first wiki)) t) (page-links (first wiki))]
        [else                                (page-links-by-title t (rest wiki))]))