(use-modules (graphgif)
	     (srfi srfi-1))

(define my-graph
  `(((10 . 10) (1) ,white)
    ((30 . 20) ()  ,red)))

(define more-complex-graph
  `(((10 . 10) () ,white) 
    ((40 . 10) (0) ,white)
    ((25 . 25) (0 1) ,white)
    ((10 . 40) (0 2 4) ,white)
    ((40 . 40) (1 2 3) ,white)))

(define (idx->x i w)
  (modulo i w))

(define (idx->y i w)
  (quotient i w))

(define (xy->idx x y w)
  (+ (* y w) x))

(define (idx->edges i w)
  (filter-map
   (lambda (x y)
     (if (or (negative? (+ (idx->x i w) x))
	     (negative? (+ (idx->y i w) y))
	     (>= (+ (idx->x i w) x) w))
	 #f
	 (xy->idx
	  (+ (idx->x i w) x)
	  (+ (idx->y i w) y)
	  w)))
   '(+0 -1 -1 +1)
   '(-1 +0 -1 -1)))

(define (generate-web w h)
  (define (make-node i)
    (list
     (cons (+ (* 30 (idx->x i w)) 10)
	   (+ (* 30 (idx->y i w)) 10))
     (idx->edges i w)
     white))
  (reverse
   (let loop ([i 0]
	      [lst '()])
     (if (>= i (* w h))
	 lst
	 (loop (1+ i) (cons (make-node i) lst))))))

(write-graph-to-file (generate-web 5 5) (cadr (command-line)))