From d01a8186d8df6e78eaa0849f13ee27ce5b67f7b7 Mon Sep 17 00:00:00 2001
From: lisyarus <lisyarus@gmail.com>
Date: Thu, 15 Dec 2022 20:10:57 +0300
Subject: [PATCH] Add geom::polygon_contains

---
 libs/geom/include/psemek/geom/contains.hpp | 28 ++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/libs/geom/include/psemek/geom/contains.hpp b/libs/geom/include/psemek/geom/contains.hpp
index 064f48f2..8467382d 100644
--- a/libs/geom/include/psemek/geom/contains.hpp
+++ b/libs/geom/include/psemek/geom/contains.hpp
@@ -5,6 +5,7 @@
 #include <psemek/geom/point.hpp>
 #include <psemek/geom/simplex.hpp>
 #include <psemek/geom/orientation.hpp>
+#include <psemek/util/range.hpp>
 
 namespace psemek::geom
 {
@@ -55,4 +56,31 @@ namespace psemek::geom
 		return contains(default_robust_tag, t, p);
 	}
 
+	template <typename Iterator, typename T>
+	bool polygon_contains(Iterator begin, Iterator end, point<T, 2> const & p)
+	{
+		int count = 0;
+		for (auto it = begin, prev = std::prev(end); it != end; prev = it++)
+		{
+			auto p0 = *prev;
+			auto p1 = *it;
+			if (p0[1] > p1[1])
+				std::swap(p0, p1);
+
+			if (p0[1] <= p[1] && p[1] < p1[1])
+			{
+				if (orientation(p0, p1, p) == sign_t::positive)
+					++count;
+			}
+		}
+
+		return (count % 2) == 1;
+	}
+
+	template <typename Polygon, typename T>
+	bool polygon_contains(Polygon const & polygon, point<T, 2> const & p)
+	{
+		return polygon_contains(util::begin(polygon), util::end(polygon), p);
+	}
+
 }