;; The first three lines of this file were inserted by DrRacket. They record metadata
;; about the language level of this file in a form that our tools can easily process.
#reader(lib "htdp-beginner-reader.ss" "lang")((modname textbox-demo-before) (read-case-sensitive #t) (teachpacks ()) (htdp-settings #(#t constructor repeating-decimal #f #t none #f () #f)))
;;; An implementation of a gui textbox -- a box where a user can type text,
;;; and use left,right arrow keys, and Delete.
;;;
;;; (You may uncomment the 'big-bang' call at very end, to demo.
;;;  But only do that AFTER all test-cases pass!)

(require 2htdp/image)
(require 2htdp/universe)



;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;


; Datatype def'n:
(define-struct textbox (l r))
; make-textbox : string, string -> textbox
;    interpretation: `l` is the text to the left of the cursor; `r` is the text to the right.

; Recall: racket auto-creates constructor as above, getters, and a predicate:
;    textbox-contents : textbox -> string
;    textbox-cursor   : textbox -> natural
;    textbox? : ANY -> boolean

; examples of data


(define EMPTY-TEXTBOX (make-textbox "" ""))
(make-textbox "z" "")
(make-textbox "" "z")
(make-textbox "ano" "ther")
(make-textbox "anot" "her")





; template:

; func-for-textbox : textbox -> ???
;
(define (func-for-textbox a-box)
  (... (textbox-l a-box) ... (textbox-r a-box) ...))

;===========

(check-expect (handle-key (make-textbox "hel" "lo") "z")
              (make-textbox "helz" "lo"))
(check-expect (handle-key (make-textbox "hel" "lo") "right")
              (make-textbox "hell" "o"))
(check-expect (handle-key (make-textbox "hel" "lo") "left")
              (make-textbox "he" "llo"))
(check-expect (handle-key (make-textbox "hel" "lo") "\b")
              (make-textbox "he" "lo"))
(check-expect (handle-key (make-textbox "hel" "lo") "down")
              (make-textbox "hel" "lo"))

(check-expect (handle-key (make-textbox "hello" "") "right")
              (make-textbox ... ...))
(check-expect (handle-key (make-textbox "" "hello") "left")
              (make-textbox ... ...))
(check-expect (handle-key (make-textbox "" "hello") "\b")
              (make-textbox ... ...))

(check-expect (handle-key EMPTY-TEXTBOX "z")
              (make-textbox ... ...))
(check-expect (handle-key EMPTY-TEXTBOX "left")
              EMPTY-TEXTBOX)
(check-expect (handle-key EMPTY-TEXTBOX "right")
              EMPTY-TEXTBOX)
(check-expect (handle-key EMPTY-TEXTBOX "\b")
              EMPTY-TEXTBOX)


; handle-key : textbox?, key-event? -> textbox?
; Update `a-textbox` to incorporate `key`.
;
(define (handle-key a-tb key)
  (... (textbox-l a-tb) (textbox-r a-tb) key  ))


(define BOX-H 40)             ; height of the drawn text-box, in px (as per image library).
(define BOX-W 400)            ; minimum width of the text-box, in px.
(define BOX (rectangle BOX-W BOX-H 'outline 'green))

(define FONT-H BOX-H)         ; font-size (height of a typical char), in px.
(define CURSOR-H (* FONT-H 0.8)) ; height of our cursor, in px.
(define CURSOR (rectangle 2 CURSOR-H 'solid 'orange)) ; the cursor-image

(check-expect (draw (make-textbox "hel" "lo"))
              (overlay/align "left" "center"
                             (beside (text (substring "hello" 0 3) FONT-H 'blue)
                                     CURSOR
                                     (text "lo" FONT-H 'blue))
                             BOX))


(check-expect (draw (make-textbox "" "hello"))
              (overlay/align "left" "center"
                             (beside CURSOR
                                     (text "hello" FONT-H 'blue))
                             BOX))

(check-expect (draw (make-textbox "hello" ""))
              (overlay/align "left" "center"
                             (beside (text "hello" FONT-H 'blue)
                                     CURSOR)
                             BOX))


(check-expect (draw (make-textbox "" ""))
              (overlay/align "left" "center"
                             CURSOR
                             BOX))


; draw : textbox? -> image?
; Create an image corresponding to the textbox.
;
(define (draw a-textbox)
 BOX)







;-----------------------------------
(require 2htdp/universe)    ; Note: usually we place any `require`s at the top of our file.

#;(big-bang (make-textbox "" "")
    [on-draw draw]
    [on-key handle-key])




;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;;;;;;;;;;;; Code to move to top  of the file, after we've discussed the above.

; A few shorter names for standard string functions, for convenience:
;(define (substr s a b) (substring s a b))
;(define (str+ s1 s2) (string-append s1 s2))
;(define (strlen s) (string-length s))


; clamp : real?, real?, real? -> real?
; Return x, except clamped to the interval [a,b].
;   (That is, the closest number to x which is in [a,b] inclusive.)
; @pre (<= a b)
; Note: Beginning-student does not contain nan.0, but if it did this code
; would be weird in that case.
;
(define (clamp a x b)
  (cond [(<= a x b) x]
        [(not (<= a x)) a]
        [(not (<= x b)) b]
        [else (error 'clamp "violated pre-condition: first arg " a " must be <= " b)]))

(check-expect (clamp 1 3 5) 3)
(check-expect (clamp 1 0 5) 1)
(check-expect (clamp 1 7 5) 5)
(check-expect (clamp 1 1 5) 1)
(check-expect (clamp 1 5 5) 5)
(check-expect (clamp 1 +inf.0 5) 5)
(check-expect (clamp -inf.0 777777777 +inf.0) 777777777)

(define (infinite? x) (= (abs x) +inf.0))
(check-satisfied (clamp -inf.0 +inf.0 +inf.0) infinite?)
(check-satisfied (clamp -inf.0 -inf.0 +inf.0) infinite?)




; substr/safe : string, natnum, natum-or-inf.0 -> string
; Like substring, but if `a` or `b` aren't valid indices of `s`,
; just grab 'til the start/end of `s` instead.
; As a special case, `b` may be +inf.0, to take to the end-of-`s`.
; pre-condition: (and (<= a (string-length s)) (>= b 0))
;    (Note/bug: I should relax this pre-condition, after `let*` introduced.)
;
(define (substr/safe s a b)
  (substring s (clamp 0 a (string-length s)) (clamp 0 b (string-length s))))

(check-expect (substr/safe "hello" 2 4) "ll")
(check-expect (substr/safe "hello" 2 19) "llo")
(check-expect (substr/safe "hello" 2 +inf.0) "llo")

(check-expect (substr/safe "hello" 0 5) "hello")
(check-expect (substr/safe "hello" -2 44) "hello")
(check-expect (substr/safe "hello" -2 1) "h")

(check-expect (substr/safe "hello" 92 95) "")
(check-expect (substr/safe "hello" -7 -3) "")
(check-expect (substr/safe "hello" -5 0) "")

(check-expect (substr/safe "" -5 17) "")


(define (str-last s) (substr/safe s (sub1 (string-length s)) +inf.0))
(define (str-drop-last s) (substr/safe s 0 (sub1 (string-length s))))

(check-expect (str-last "") "")
(check-expect (str-last "a") "a")
(check-expect (str-last "hello") "o")
(check-expect (str-drop-last "") "")
(check-expect (str-drop-last "a") "")
(check-expect (str-drop-last "hello") "hell")


#|
@author ibarland
@version 2018-Sep-27

@license: CC-BY 4.0 -- you are free to share and adapt this file
for any purpose, provided you include appropriate attribution.
    https://creativecommons.org/licenses/by/4.0/ 
    https://creativecommons.org/licenses/by/4.0/legalcode 
Including a link to the *original* file satisifies "appropriate attribution".
|#