From 4f43260f449721fde9af8aef0fdf96de71f658b7 Mon Sep 17 00:00:00 2001
From: Justin Lin <justin.sdk@gmail.com>
Date: Sun, 24 Apr 2022 17:10:37 +0800
Subject: [PATCH] refactor

---
 src/_impl/_bijection_offset_impl.scad | 29 ++++++++-------------------
 1 file changed, 8 insertions(+), 21 deletions(-)

diff --git a/src/_impl/_bijection_offset_impl.scad b/src/_impl/_bijection_offset_impl.scad
index 78112f66..816347d6 100644
--- a/src/_impl/_bijection_offset_impl.scad
+++ b/src/_impl/_bijection_offset_impl.scad
@@ -1,42 +1,30 @@
 use <../__comm__/__lines_from.scad>;
 use <../__comm__/__line_intersection.scad>;
     
-function _bijection_inward_edge_normal(edge) =  
+function _bijection_outward_edge_normal(edge) =     
     let(
-        pt1 = edge[0],
-        pt2 = edge[1],
-        dx = pt2.x - pt1.x,
-        dy = pt2.y - pt1.y,
-        edge_leng = norm([dx, dy])
+        v = edge[1] - edge[0],
+        nv = v / norm(v)
     )
-    [-dy / edge_leng, dx / edge_leng];
+    [nv.y, -nv.x];
 
-function _bijection_outward_edge_normal(edge) = -1 * _bijection_inward_edge_normal(edge);
-
-function _bijection_offset_edge(edge, dx, dy) = 
-    let(
-        pt1 = edge[0],
-        pt2 = edge[1],
-        dxy = [dx, dy]
-    )
-    [pt1 + dxy, pt2 + dxy];
+function _bijection_offset_edge(edge, dxy) = edge + [dxy, dxy];
     
 function _bijection__bijection_offset_edges(edges, d) = 
     [ 
         for(edge = edges)
-        let(ow_normal_d = _bijection_outward_edge_normal(edge) * d)
-        _bijection_offset_edge(edge, ow_normal_d.x, ow_normal_d.y)
+        _bijection_offset_edge(edge, _bijection_outward_edge_normal(edge) * d)
     ];
 
 function _bijection_offset_impl(pts, d, epsilon) = 
     let(
         es = __lines_from(pts, true), 
         offset_es = _bijection__bijection_offset_edges(es, d),
-        leng = len(offset_es),
-        leng_minus_one = leng - 1,
+        leng_minus_one = len(offset_es) - 1,
         last_p = __line_intersection2(offset_es[leng_minus_one], offset_es[0], epsilon)
     )
     [
+        // p == p to avoid [nan, nan], because [nan, nan] != [nan, nan]
         if(last_p != [] && last_p == last_p) last_p,
         each [
             for(i = 0; i < leng_minus_one; i = i + 1)
@@ -45,7 +33,6 @@ function _bijection_offset_impl(pts, d, epsilon) =
                 next_edge = offset_es[i + 1],
                 p = __line_intersection2(this_edge, next_edge, epsilon)
             )
-            // p == p to avoid [nan, nan], because [nan, nan] != [nan, nan]
             assert(p != [] && p == p, "bijection_offset failed. Parallel or conincident edges found")
             p
         ]