From 2becc43f5888802695ca2c7857aa1bd0e30da9fd Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mateusz=20Czapli=C4=B9=E2=80=9Eski?= <czapkofan@gmail.com>
Date: Wed, 8 Oct 2014 23:12:19 +0200
Subject: [PATCH] added testcase showing issue #3

---
 bugs_test.go | 73 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 73 insertions(+)
 create mode 100644 bugs_test.go

diff --git a/bugs_test.go b/bugs_test.go
new file mode 100644
index 0000000..1d1f727
--- /dev/null
+++ b/bugs_test.go
@@ -0,0 +1,73 @@
+package polyclip_test
+
+import (
+	"fmt"
+	"github.com/akavel/polyclip-go"
+	"sort"
+	. "testing"
+)
+
+type sorter polyclip.Polygon
+
+func (s sorter) Len() int      { return len(s) }
+func (s sorter) Swap(i, j int) { s[i], s[j] = s[j], s[i] }
+func (s sorter) Less(i, j int) bool {
+	if len(s[i]) != len(s[j]) {
+		return len(s[i]) < len(s[j])
+	}
+	for k := range s[i] {
+		pi, pj := s[i][k], s[j][k]
+		if pi.X != pj.X {
+			return pi.X < pj.X
+		}
+		if pi.Y != pj.Y {
+			return pi.Y < pj.Y
+		}
+	}
+	return false
+}
+
+// basic normalization just for tests; to be improved if needed
+func normalize(poly polyclip.Polygon) polyclip.Polygon {
+	for i, c := range poly {
+		if len(c) == 0 {
+			continue
+		}
+
+		// find bottom-most of leftmost points, to have fixed anchor
+		min := 0
+		for j, p := range c {
+			if p.X < c[min].X || p.X == c[min].X && p.Y < c[min].Y {
+				min = j
+			}
+		}
+
+		// rotate points to make sure min is first
+		poly[i] = append(c[min:], c[:min]...)
+	}
+
+	sort.Sort(sorter(poly))
+	return poly
+}
+
+func dump(poly polyclip.Polygon) string {
+	return fmt.Sprintf("%v", normalize(poly))
+}
+
+func TestBug3(t *T) {
+	subject := polyclip.Polygon{{{1, 1}, {1, 2}, {2, 2}, {2, 1}}}
+	clipping := polyclip.Polygon{
+		{{2, 1}, {2, 2}, {3, 2}, {3, 1}},
+		{{1, 2}, {1, 3}, {2, 3}, {2, 2}},
+		{{2, 2}, {2, 3}, {3, 3}, {3, 2}}}
+	result := dump(subject.Construct(polyclip.UNION, clipping))
+
+	exp := dump(polyclip.Polygon{{
+		{1, 1}, {2, 1}, {3, 1},
+		{3, 2}, {3, 3},
+		{2, 3}, {1, 3},
+		{1, 2}}})
+	if result != exp {
+		t.Errorf("expected %s, got %s", exp, result)
+	}
+}