fix(polygon): Add properties for inside and outside angles

ladybug_geometry/geometry2d/polygon.py

@@ -33,6 +33,8 @@ class Polygon2D(Base2DIn2D):
     Properties:
         * vertices
         * segments
+        * inside_angles
+        * outside_angles
         * min
         * max
         * center
@@ -43,14 +45,16 @@ class Polygon2D(Base2DIn2D):
         * is_self_intersecting
         * is_valid
     """
-    __slots__ = ('_segments', '_perimeter', '_area',
+    __slots__ = ('_segments', '_inside_angles', '_outside_angles', '_perimeter', '_area',
                  '_is_clockwise', '_is_convex', '_is_self_intersecting')
 
     def __init__(self, vertices):
         """Initialize Polygon2D."""
         Base2DIn2D.__init__(self, vertices)
         self._segments = None
         self._perimeter = None
+        self._inside_angles = None
+        self._outside_angles = None
         self._area = None
         self._is_clockwise = None
         self._is_convex = None
@@ -308,6 +312,39 @@ def segments(self):
             self._segments = tuple(_segs)
         return self._segments
 
+    @property
+    def inside_angles(self):
+        """Tuple of angles in radians for the interior angles of the polygon.
+
+        These are aligned with the vertices such that the first angle corresponds
+        to the inside angle at the first vertex, the second at the second vertex,
+        and so on.
+        """
+        if self._inside_angles is None:
+            angles, is_clock = [], self.is_clockwise
+            for i, pt in enumerate(self.vertices):
+                v1 = self.vertices[i - 2] - self.vertices[i - 1]
+                v2 = pt - self.vertices[i - 1]
+                v_angle = v1.angle_counterclockwise(v2) if is_clock \
+                    else v1.angle_clockwise(v2)
+                angles.append(v_angle)
+            angles.append(angles.pop(0))  # move the start angle to the end
+            self._inside_angles = tuple(angles)
+        return self._inside_angles
+
+    @property
+    def outside_angles(self):
+        """Tuple of angles in radians for the exterior angles of the polygon.
+
+        These are aligned with the vertices such that the first angle corresponds
+        to the inside angle at the first vertex, the second at the second vertex,
+        and so on.
+        """
+        if self._outside_angles is None:
+            pi2 = math.pi * 2
+            self._outside_angles = tuple(pi2 - a for a in self.inside_angles)
+        return self._outside_angles
+
     @property
     def perimeter(self):
         """The perimeter of the polygon."""

tests/polygon2d_test.py

@@ -43,6 +43,25 @@ def test_polygon2d_init():
         assert isinstance(p_array, tuple)
         assert len(arr) == 2
 
+    assert isinstance(polygon.inside_angles, tuple)
+    assert len(polygon.inside_angles) == 4
+    assert all(math.degrees(a) == 90 for a in polygon.inside_angles)
+
+    assert isinstance(polygon.outside_angles, tuple)
+    assert len(polygon.outside_angles) == 4
+    assert all(math.degrees(a) == 270 for a in polygon.outside_angles)
+
+
+def test_polygon2d_inside_angles():
+    """Test the Polygon2D.inside_angles property."""
+    pts = (Point2D(-2, 0), Point2D(2, 0), Point2D(2, 2), Point2D(0, 2))
+    polygon = Polygon2D(pts)
+
+    assert math.degrees(polygon.inside_angles[0]) == pytest.approx(45, rel=1e-3)
+    assert math.degrees(polygon.inside_angles[1]) == pytest.approx(90, rel=1e-3)
+    assert math.degrees(polygon.inside_angles[2]) == pytest.approx(90, rel=1e-3)
+    assert math.degrees(polygon.inside_angles[3]) == pytest.approx(135, rel=1e-3)
+
 
 def test_polygon2d_is_rectangle():
     """Test the Polygon2D.is_rectangle method."""