(define image.read-object!
  (lambda (image port)
    (let* ((type (read port))
           (stroked? (list.contains? 
                       (list "empty ellipse" "empty circle" 
                             "empty rectangle" "empty square" 
                             "line")
                       type))
           (color (read port))
           (brush (if stroked? (read port) (envt.get-brush))))
      (cond 
        ; If we are at eof, return eof.
        ((eof-object? type) type)
        ; Otherwise, there is more to draw.
        (else
          ; Set the color and brush.
          (envt.set-fgcolor! (cname->rgb color))
          (envt.set-brush! brush)
          ; Select the shape type, read the remaining data, and draw it.
          (cond
            ((list.contains? (list "empty ellipse" "filled ellipse") type)
             (let* ((left (read port))
                    (top (read port))
                    (width (read port))
                    (height (read port)))
               (image.select-ellipse! image 
                                      selection.replace
                                      left top width height)
               (if stroked?
                   (image.stroke! image)
                   (image.fill! image))
               (image.select-nothing! image)))
            ((list.contains? (list "empty circle" "filled circle") type)
             (let* ((left (read port))
                    (top (read port))
                    (diameter (read port)))
               (image.select-ellipse! image 
                                      selection.replace
                                      left top diameter diameter)
               (if stroked?
                   (image.stroke! image)
                   (image.fill! image))
               (image.select-nothing! image)))
            ((list.contains? (list "empty rectangle" "filled rectangle") type)
             (let* ((left (read port))
                    (top (read port))
                    (width (read port))
                    (height (read port)))
               (image.select-rectangle! image 
                                        selection.replace
                                        left top width height)
               (if stroked?
                   (image.stroke! image)
                   (image.fill! image))
               (image.select-nothing! image)))
            ((list.contains? (list "empty square" "filled square") type)
             (let* ((left (read port))
                    (top (read port))
                    (side (read port)))
               (image.select-rectangle! image 
                                        selection.replace
                                        left top side side)
               (if stroked?
                   (image.stroke! image)
                   (image.fill! image))
               (image.select-nothing! image)))
            ((equal? type "line")
             (let* ((start-col (read port))
                    (start-row (read port))
                    (end-col (read port))
                    (end-row (read port)))
               (image.draw-line! image start-col start-row end-col end-row)))))))))


(define image.read-objects!
  (lambda (image filename)
    (let kernel ((in-port (open-input-file filename)))
      (cond 
        ; If we are at the end of the file, close the port and return the image.
        ((eof-object? (peek-char in-port))
         (close-input-port in-port)
         image)
        ; Otherwise, read the next object and recursively call the kernel.
        (else
         (image.read-object! image in-port)
         (kernel in-port))))))
        

(define list.contains?
  (lambda (lst val)
    (and (not (null? lst))
         (or (equal? (car lst) val)
             (list.contains? (cdr lst) val)))))

(define empty-ellipse.write
  (lambda (port color brush left top width height)
    (write "empty ellipse" port)
    (display " " port)    
    (write (if (rgb? color) (rgb->cname color) color) port)
    (display " " port)
    (write brush port)
    (display " " port)
    (write left port)
    (display " " port)
    (write top port)
    (display " " port)
    (write width port)
    (display " " port)
    (write height port)
    (newline port)))

(define filled-ellipse.write
  (lambda (port color left top width height)
    (write "filled ellipse" port)
    (display " " port)    
    (write (if (rgb? color) (rgb->cname color) color) port)
    (display " " port)
    (write left port)
    (display " " port)
    (write top port)
    (display " " port)
    (write width port)
    (display " " port)
    (write height port)
    (newline port)))

(define empty-circle.write
  (lambda (port color brush left top diameter)
    (write "empty circle" port)
    (display " " port)    
    (write (if (rgb? color) (rgb->cname color) color) port)
    (display " " port)
    (write brush port)
    (display " " port)
    (write left port)
    (display " " port)
    (write top port)
    (display " " port)
    (write diameter port)
    (newline port)))

(define filled-circle.write
  (lambda (port color left top diameter)
    (write "filled circle" port)
    (display " " port)    
    (write (if (rgb? color) (rgb->cname color) color) port)
    (display " " port)
    (write left port)
    (display " " port)
    (write top port)
    (display " " port)
    (write diameter port)
    (newline port)))

(define empty-rectangle.write
  (lambda (port color brush left top width height)
    (write "empty rectangle" port)
    (display " " port)    
    (write (if (rgb? color) (rgb->cname color) color) port)
    (display " " port)
    (write brush port)
    (display " " port)
    (write left port)
    (display " " port)
    (write top port)
    (display " " port)
    (write width port)
    (display " " port)
    (write height port)
    (newline port)))

(define filled-rectangle.write
  (lambda (port color left top width height)
    (write "filled rectangle" port)
    (display " " port)    
    (write (if (rgb? color) (rgb->cname color) color) port)
    (display " " port)
    (write left port)
    (display " " port)
    (write top port)
    (display " " port)
    (write width port)
    (display " " port)
    (write height port)
    (newline port)))

(define empty-square.write
  (lambda (port color brush left top side)
    (write "empty square" port)
    (display " " port)    
    (write (if (rgb? color) (rgb->cname color) color) port)
    (display " " port)
    (write brush port)
    (display " " port)
    (write left port)
    (display " " port)
    (write top port)
    (display " " port)
    (write side port)
    (newline port)))

(define filled-square.write
  (lambda (port color left top side)
    (write "filled square" port)
    (display " " port)    
    (write (if (rgb? color) (rgb->cname color) color) port)
    (display " " port)
    (write left port)
    (display " " port)
    (write top port)
    (display " " port)
    (write side port)
    (newline port)))

(define line.write
  (lambda (port color brush start-col start-row end-col end-row)
    (write "line" port)
    (display " " port)    
    (write (if (rgb? color) (rgb->cname color) color) port)
    (display " " port)
    (write brush port)
    (display " " port)
    (write start-col port)
    (display " " port)
    (write start-row port)
    (display " " port)
    (write end-col port)
    (display " " port)
    (write end-row port)
    (newline port)))