From 3afa2169c363ae58950a4dc91318ef94c726341b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Motiejus=20Jak=C5=A1tys?= <motiejus@jakstys.lt>
Date: Wed, 19 May 2021 22:57:45 +0300
Subject: [PATCH] wip detecting crossings

---
 wm.sql | 21 ++++++++++++++++-----
 1 file changed, 16 insertions(+), 5 deletions(-)

diff --git a/wm.sql b/wm.sql
index c8bd05a..c324399 100644
--- a/wm.sql
+++ b/wm.sql
@@ -165,6 +165,8 @@ $$ language plpgsql;
 -- article's section "Self-line Crossing When Cutting a Bend".
 create or replace function self_crossing(INOUT bends geometry[]) as $$
 declare
+  i int4;
+  j int4;
   pi real;
   angle real;
   p geometry;
@@ -176,12 +178,12 @@ begin
   pi = radians(180);
 
   -- go through the bends and find one where sum of inflection angle is >180
-  foreach bend in array bends loop
+  for i in 1..array_length(bends, 1) loop
     angle = 0;
-    p3 = null;
-    p2 = null;
     p1 = null;
-    for p in (select geom from st_dumppoints(bend) order by path[1] asc) loop
+    p2 = null;
+    p3 = null;
+    for p in (select geom from st_dumppoints(bends[i]) order by path[1] asc) loop
       p3 = p2;
       p2 = p1;
       p1 = p;
@@ -192,7 +194,16 @@ begin
     end loop;
 
     if abs(angle) > pi then
-      raise notice 'maybe self-crossing bend %: %', st_astext(bend), round(degrees(abs(angle)));
+      raise notice 'maybe self-crossing bend %: %', st_astext(bends[i]), round(degrees(abs(angle)));
+      -- sum of inflection angles for this bend is >180, so it may be self-crossing.
+      -- now try to find another bend in this line that crosses this one.
+      for j in 1..array_length(bends, 1) loop
+        continue when i = j;
+
+
+
+      end loop;
+
     end if;
   end loop;