(define-module (graphgif))

(use-modules (cairo)
	     (srfi srfi-1))

(re-export (cairo-pattern-create-rgb . create-color))

;;;;;;;;;;;;;;;;;;;
;; Basic Drawing ;;
;;;;;;;;;;;;;;;;;;;

(define-public pi 3.14159)
(define-public tau (* 2 pi))

(define-public black (cairo-pattern-create-rgb 0 0 0))
(define-public white (cairo-pattern-create-rgb 1 1 1))

(define (edge-painter cr graph)
  (lambda (node)
    (cairo-set-source cr black)
    (let ([x (caar node)]
	  [y (cdar node)]
	  [edges (cadr node)])
      (for-each
       (lambda (edge)
	 (let* ([other (list-ref graph edge)]
		[ox (caar other)]
		[oy (cdar other)])
	   (cairo-move-to cr x y)
	   (cairo-line-to cr ox oy)
	   (cairo-stroke cr)))
       edges))))

(define (node-painter cr)
  (lambda (node)
    (let ([x (caar node)]
	  [y (cdar node)]
	  [color (if (null? (cddr node))
		     white
		     (caddr node))])
      (cairo-arc cr x y 4. 0. tau)
      (cairo-set-source cr color)
      (cairo-fill-preserve cr)
      (cairo-set-source cr black)
      (cairo-stroke cr))))

(define-public (draw-abstract-graph graph)
  (let* ([surface (cairo-image-surface-create 'rgb24 400 400)]
	 [cr (cairo-create surface)])
    (define paint-edges (edge-painter cr graph))
    (define paint-nodes (node-painter cr))
    ;; White background
    (cairo-rectangle cr 0 0 400 400)
    (cairo-set-source cr white)
    (cairo-fill cr)
    (for-each paint-edges graph)
    (for-each paint-nodes graph)
    (cairo-destroy cr)
    surface))

;;;;;;;;;;;;;;;;;;;;;;
;; Graph Generation ;;
;;;;;;;;;;;;;;;;;;;;;;

(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 (offset)
     (let* ([x (idx->x i w)]
	    [y (idx->y i w)]
	    [ox (+ x (car offset))]
	    [oy (+ y (cdr offset))])
       (and
	(not (negative? ox))
	(not (negative? oy))
	(< ox w)
	(xy->idx ox oy w))))
   ;; Auto-connect these directions if legal indices
   '(( 0 . -1)
     (-1 .  0)
     (-1 . -1)
     (+1 . -1))))

(define-public (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)))
  (let loop ([i 0]
	     [lst '()])
    (if (>= i (* w h))
	(reverse lst)
	(loop (1+ i) (cons (make-node i) lst)))))

;;;;;;;;;;;;
;; Output ;;
;;;;;;;;;;;;

(define (output-to-file surfaces filename)
  (define pngdir (mkdtemp "graphgif_XXXXXX"))
  (do ([i 1 (1+ i)]
       [surfaces surfaces (cdr surfaces)])
      ((null? surfaces))
    (cairo-surface-write-to-png
     (car surfaces)
     (string-append pngdir "/img-" (number->string i) ".png")))
  (system* "ffmpeg" "-i" (string-append pngdir "/img-%d.png") "-r" "1" filename))

(define-public (write-graphs-to-file graphs filename)
  (output-to-file (map draw-abstract-graph graphs) filename))

;; Local Variables:
;; geiser-scheme-implementation: guile
;; End: