#lang racket

(require htdp/error)

(provide (all-defined-out))

(define INSET  5)     ;; the space around the image in the canvas
(define RATE   1/30)   ;; the clock tick rate 
(define TRIES  3)     ;; how many times should register try to connect to the server 
(define PAUSE  1/2)     ;; # secs to wait between attempts to connect to server 
(define SQPORT 4567) ;; the port on which universe traffic flows

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;   ;       ;;;   ;;;;;  ;;;;;   ;;;   ;;;;          ;   ;  ;   ;  ;   ;        
;   ;      ;   ;  ; ; ;  ; ; ;  ;   ;  ;   ;         ;;;;;  ;   ;   ; ;         
;   ;      ;   ;  ; ; ;  ; ; ;  ;   ;  ;   ;         ;   ;  ;   ;    ;          
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;    ;;;    ;;;   ; ; ;  ; ; ;   ;;;   ;   ;         ;   ;   ;; ;  ;   ;   ;;   
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;; -----------------------------------------------------------------------------

;; Any -> Boolean
(define (nat? x)
  (and (number? x) (integer? x) (>= x 0)))

;; Number Symbol Symbol -> Integer
(define (number->integer x [t ""] [p ""])
  (check-arg t (and (number? x) (real? x)) "real number" p x)
  (inexact->exact (floor x)))

;; -----------------------------------------------------------------------------
;; Nat Nat ->String 
;; converts i to a string, adding leading zeros, make it at least as long as L
(define (zero-fill i L)
  (let ([n (number->string i)])
    (string-append (make-string (max (- L (string-length n)) 0) #\0) n)))

;; -----------------------------------------------------------------------------

;; MouseEvent% -> [List Nat Nat MouseEventType]
;; turn a mouse event into its pieces 
(define (mouse-event->parts e)
  (define x (- (send e get-x) INSET))
  (define y (- (send e get-y) INSET))
  (values x y 
          (cond [(send e button-down?) "button-down"]
                [(send e button-up?)   "button-up"]
                [(send e dragging?)    "drag"]
                [(send e moving?)      "move"]
                [(send e entering?)    "enter"]
                [(send e leaving?)     "leave"]
                [else ; (send e get-event-type)
                 (let ([m (send e get-event-type)])
                   (error 'on-mouse (format "Unknown event: ~a" m)))])))

;; KeyEvent% -> String
(define (key-event->parts e)
  (define x (send e get-key-code))
  (cond
    [(char? x) (string x)]
    [(symbol? x) (symbol->string x)]
    [else (error 'on-key (format "Unknown event: ~a" x))]))

;; KeyEvent% -> String
(define (key-release->parts e)
  (define x (send e get-key-release-code))
  (cond
    [(char? x) (string x)]
    [(symbol? x) (symbol->string x)]
    [else (error 'on-key (format "Unknown event: ~a" x))]))

;; -----------------------------------------------------------------------------
;; Any -> Symbol 
(define (name-of draw tag)
  (define fname  (object-name draw))
  (if fname fname tag))

;; -----------------------------------------------------------------------------
;; Any -> Boolean
(define (sexp? x)
  (cond
    [(empty? x) true]
    [(string? x) true]
    [(symbol? x) true]
    [(number? x) true]
    [(boolean? x) true]
    [(char? x) true]
    [(pair? x) (and (list? x) (andmap sexp? x))]
    [else false]))

(define (no-newline? x)
  (not (member #\newline (string->list x))))

;; -----------------------------------------------------------------------------
;; exchange one-line messages between worlds and the server

(define tcp-eof (gensym 'tcp-eof))

;; Any -> Boolean 
(define (tcp-eof? a) (eq? tcp-eof a))

;; OutPort Sexp -> Void
(define (tcp-send out msg)
  (write msg out)
  (newline out)
  (flush-output out))

;; InPort -> Sexp
(define (tcp-receive in)
  (with-handlers ((exn? (lambda (x) (raise tcp-eof))))
    (define x (read in))
    (if (eof-object? x) 
        (raise tcp-eof)
        (begin
          (read-line in) ;; read the newline 
          x))))

;; InPort OutPort (X -> Y) -> (U Y Void)
;; process a registration from a potential client, invoke k if it is okay
(define (tcp-process-registration in out k)
  (define next (tcp-receive in))
  (match next
    [`(REGISTER ((name ,name)))
     (tcp-send out '(OKAY))
     (k name)]))
  
;; InPort OutPort (U #f String) -> Void 
;; register with the server 
(define (tcp-register in out name)
  (define msg `(REGISTER ((name ,(if name name (symbol->string (gensym 'world)))))))
  (tcp-send out msg)
  (define ackn (tcp-receive in))
  (unless (equal? ackn '(OKAY))
    (raise tcp-eof)))

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;; Symbol Any String -> Void
(define (check-pos t c r)
  (check-arg 
   t (and (real? c) (>= (number->integer c t r) 0)) "positive integer" r c))
