;;; grid-geometry.lisp

(in-package :wheelwork )

(defmacro with-grid-line
    ((x y) (start-x start-y) (end-x end-y) &body body)
  "Execute BODY for X and Y assigned to integer values in a line
connecting the integer point START-X , START-Y and END-X, END-Y. "
  (with-gensyms (sx sy ex ey distance step progress xdiff ydiff)
    `(loop
       with ,sx = ,start-x
       with ,sy = ,start-y
       with ,ex = ,end-x
       with ,ey = ,end-y
       with ,xdiff = (- ,ex ,sx)
       with ,ydiff = (- ,ey, sy)
       with ,distance = (max (abs ,xdiff) (abs ,ydiff))
       for ,step from 0 to ,distance
       for ,progress = (if (zerop ,distance) 0.0 (/ ,step ,distance))
       for ,x = (round (+ ,start-x (* ,progress ,xdiff)))
       for ,y = (round (+ ,start-y (* ,progress ,ydiff)))
       do (progn ,@body))))

(defmacro with-grid-path
    ((x y) (path &key autoclosep interiorp) &body body)
  (with-gensyms (points x1 y1 x2 y2 more)
    (let ((autoclose-block
            (when autoclosep
              `(destructuring-bind (,x2 ,y2) (first ,points)
                 (with-grid-line (,x2 ,y2) (,x1 ,y1) ,@body))))) 
      `(let ((,points ,path))
         (loop
           for ((,x1 ,y) (,x2 ,y2) . ,more) on ,points
           while ,x2 do
             (with-grid-line (,x ,y) (,x1 ,y1) (,x2 ,y2) ,@body)
           finally (progn ,autoclose-block))))))

(defun grid-bbox-for (poly)
  "POLY is a list of pairs of xy coordinates. Return a pair of
pairs, ((min-x min-y) (max-x max-y)), representing the bottom left and
top right corners of the bounding box for POLY "
  (loop for (x y) in poly
        minimizing x into x-min
        maximizing x into x-max
        minimizing y into y-min
        maximizing y into y-max
        finally (return (list (list x-min y-min)
                              (list x-max y-max)))))

(defmacro with-grid-poly-interior
    ((x y) perimeter &body body)
  "PERMIETER is expected to evaluate to a list of contiguous points,
representing the permimeter a polygon in 2d space. Execute BODY for
each point interior to this polygon."
  (with-gensyms (points bottom left top right)
    `(let ((,points ,permieter))
       (destructuring-bind ((,left ,bottom) (,right ,top)) (grid-bbox-for ,points)
         (loop )
         )))
  )

(defmacro with-grid-circle
    ((x y) (cx cy radius &key interiorp) &body body)
  (with-gensyms (rad sx sy)
    (let ((comparator
            (if interiorp '>= '=))) 
      `(let ((,sx ,cx) (,sy ,cy) (,rad ,radius)) 
         (with-grid-rect (,x ,y) ((- ,sx ,rad) (- ,sy ,rad) (+ ,sx ,rad) (+ ,sy ,rad))
           (when (,comparator ,rad (round (euclidean-dist ,x ,y ,sx ,sy)))
             ,@body))))))