;; Copyright (c) 2006, Sarken LLC
;; Contact: Gordon Fischer [ fischer@sarken.org ]
;; Released under the Creative Commons Attribution License
;; http://creativecommons.org/licenses/by/2.5/

;; Based on the following Perl code [ http://brevity.org/code/google/google-draw-pl.txt ]
# Copyright (c) 2005, Neil Kandalgaonkar <neilk(a)brevity.org> 
# Released under the BSD license 
# http://www.opensource.org/licenses/bsd-license.php

;; Draw takes a list of coordinates.
;; First pair is absolute, following are relative to first pair.

(context 'GOOGLE)

(set 'test-clist-rel '( (10 10) (20 0) (0 20) (-20 0) (0 -20) ))
(set 'test-clist-abs '( (10 10) (30 10) (30 30) (10 30) (10 10) ))

(define (Draw-rel clist , e f path)
  (set 'path "")
  (push 9999 clist -1) ;; end of stream marker
  (dolist (c (flat clist))
    (set 'f (- (* (abs c) 2) (if (< c 0) 1 0)))
    (do-while (!= 0 f)
      (set 'e (& f 31))
      (set 'f (>> f 5))
      (if (> f 0) (set 'e (| e 32)))
      (write-buffer path (char (+ e 63)))
    )
  )
  path
)

(define (Draw a , b max_x max_y results)
  (set 'b (transpose a))
  (set 'max_x (apply max (b 0)))
  (set 'max_y (apply max (b 1)))
  (set 'b a)
  (push '(0 0) a)
  (push '(0 0) b -1)
  (dotimes (x (length a)) (push (list (- (b x 0) (a x 0)) (- (b x 1) (a x 1))) results -1))
  (pop results -1)
  (string "http://www.google.com/maplinedraw?width=" (+ max_x 10) "&height=" (+ max_y 10)
          "&path=" (Draw-rel results))
)

(context 'MAIN)

;; This will generate a URL that draws a square
;; (GOOGLE:Draw GOOGLE:test-clist-abs)