#lang racket

(require "hw4provided.rkt") ; change file name as appropriate

;; A simple library for displaying a 2x3 grid of pictures: used
;; for fun in the tests below (look for "Tests Start Here").

(require (lib "graphics.rkt" "graphics"))

(open-graphics)

(define window-name "CSE341, Homework 4")
(define window-width 700)
(define window-height 500)
(define border-size 100)

(define approx-pic-width 200)
(define approx-pic-height 200)
(define pic-grid-width 3)
(define pic-grid-height 2)

(define (open-window)
  (open-viewport window-name window-width window-height))

(define (grid-posn-to-posn grid-posn)
  (when (>= grid-posn (* pic-grid-height pic-grid-width))
    (error "picture grid does not have that many positions"))
  (let ([row (quotient grid-posn pic-grid-width)]
        [col (remainder grid-posn pic-grid-width)])
    (make-posn (+ border-size (* approx-pic-width col))
               (+ border-size (* approx-pic-height row)))))

(define (place-picture window filename grid-posn)
  (let ([posn (grid-posn-to-posn grid-posn)])
    ((clear-solid-rectangle window) posn approx-pic-width approx-pic-height)
    ((draw-pixmap window) filename posn)))

(define (place-repeatedly window pause stream n)
  (when (> n 0)
    (let* ([next (stream)]
           [filename (cdar next)]
           [grid-posn (caar next)]
           [stream (cdr next)])
      (place-picture window filename grid-posn)
      (sleep pause)
      (place-repeatedly window pause stream (- n 1)))))

;; Tests Start Here

; These definitions will work only after you do some of the problems
; so for convenience they are initially commented out.  
; Add more tests as appropriate of course.

;(define nums (sequence 0 5 1))

;(define files (string-append-map 
;               (list "steele" "curry" "lambda" "parens" "rational")
;               ".jpg"))


;(define (one-visual-test)
;  (place-repeatedly (open-window) 0.5 (cycle-lists nums files) 25))