From 3bd05a7ab15a835a233bde397b424fcfec4d6842 Mon Sep 17 00:00:00 2001
From: Jan-Tarek Butt <tarek@ring0.de>
Date: Sat, 20 Apr 2019 00:29:21 +0200
Subject: [PATCH] package/libgluonmath: add math lib for gauss jordan Ponit in
 Polygon algorithm

Signed-off-by: Jan-Tarek Butt <tarek@ring0.de>
---
 package/libgluonmath/Makefile                 | 15 ++++
 .../luasrc/usr/lib/lua/gluon/math.lua         | 69 +++++++++++++++++++
 2 files changed, 84 insertions(+)
 create mode 100644 package/libgluonmath/Makefile
 create mode 100644 package/libgluonmath/luasrc/usr/lib/lua/gluon/math.lua

diff --git a/package/libgluonmath/Makefile b/package/libgluonmath/Makefile
new file mode 100644
index 00000000..36c4c8fa
--- /dev/null
+++ b/package/libgluonmath/Makefile
@@ -0,0 +1,15 @@
+include $(TOPDIR)/rules.mk
+
+PKG_NAME:=libgluonmath
+PKG_VERSION:=1
+CMAKE_INSTALL:=1
+
+include $(INCLUDE_DIR)/package.mk
+
+define Package/libgluonmath
+  SECTION:=libs
+  CATEGORY:=Libraries
+  TITLE:=Gluon math library
+endef
+
+$(eval $(call BuildPackage,libgluonmath))
diff --git a/package/libgluonmath/luasrc/usr/lib/lua/gluon/math.lua b/package/libgluonmath/luasrc/usr/lib/lua/gluon/math.lua
new file mode 100644
index 00000000..bb09fa68
--- /dev/null
+++ b/package/libgluonmath/luasrc/usr/lib/lua/gluon/math.lua
@@ -0,0 +1,69 @@
+local M = {}
+
+-- Source with pseudocode: https://de.wikipedia.org/wiki/Punkt-in-Polygon-Test_nach_Jordan
+-- see also https://en.wikipedia.org/wiki/Point_in_polygon
+-- parameters: points A = (x_a,y_a), B = (x_b,y_b), C = (x_c,y_c)
+-- return value: −1 if the ray from A to the right bisects the edge [BC] (the lower vortex of [BC]
+-- is not seen as part of [BC]);
+--                0 if A is on [BC];
+--                +1 else
+function M.cross_prod_test(x_a,y_a,x_b,y_b,x_c,y_c)
+	if y_a == y_b and y_b == y_c then
+		if (x_b <= x_a and x_a <= x_c) or (x_c <= x_a and x_a <= x_b) then
+			return 0
+		end
+		return 1
+	end
+	if not ((y_a == y_b) and (x_a == x_b)) then
+		if y_b > y_c then
+			-- swap b and c
+			local h = x_b
+			x_b = x_c
+			x_c = h
+			h = y_b
+			y_b = y_c
+			y_c = h
+		end
+		if (y_a <= y_b) or (y_a > y_c) then
+			return 1
+		end
+		local delta = (x_b-x_a) * (y_c-y_a) - (y_b-y_a) * (x_c-x_a)
+		if delta > 0 then
+			return 1
+		elseif delta < 0 then
+			return -1
+		end
+	end
+	return 0
+end
+
+-- Source with pseudocode: https://de.wikipedia.org/wiki/Punkt-in-Polygon-Test_nach_Jordan
+-- see also: https://en.wikipedia.org/wiki/Point_in_polygon
+-- let P be a 2D Polygon and Q a 2D Point
+-- return value:  +1 if Q within P;
+--                −1 if Q outside of P;
+--                0 if Q on an edge of P
+function M.point_in_polygon(poly, point)
+	local t = -1
+	for i=1,#poly-1 do
+		t = t * M.cross_prod_test(point.lon,point.lat,poly[i].lon,poly[i].lat,poly[i+1].lon,poly[i+1].lat)
+		if t == 0 then break end
+	end
+	return t
+end
+
+-- Convert Rectengular defined by two point into polygon
+function M.two_point_rec_to_poly(rec)
+	local poly = {};
+	poly[1]["lon"] = rec[1].lon
+	poly[1]["lat"] = rec[1].lat
+	poly[2]["lon"] = rec[2].lon
+	poly[2]["lat"] = rec[1].lat
+	poly[3]["lon"] = rec[2].lon
+	poly[3]["lat"] = rec[2].lat
+	poly[4]["lon"] = rec[1].lon
+	poly[4]["lat"] = rec[2].lat
+	return poly
+end
+
+return M