Issue #45: add intersection class.

roentgen/road.py

@@ -0,0 +1,33 @@
+"""
+Road shape drawing.
+"""
+from typing import List
+
+import numpy as np
+
+from flinger import Flinger, angle
+from osm_reader import OSMNode
+
+
+class RoadPart:
+    """
+    Line part of the road.
+    """
+    def __init__(self, node_1: OSMNode, node_2: OSMNode, flinger: Flinger):
+        self.point_1: np.array = flinger.fling(node_1.coordinates)
+        self.point_2: np.array = flinger.fling(node_2.coordinates)
+
+    def get_angle(self) -> float:
+        """
+        Get an angle between line and x axis.
+        """
+        return angle(self.point_1, self.point_2)
+
+
+class Intersection:
+    """
+    An intersection of the roads, that is described by its parts.  All first
+    points of the road parts should be the same.
+    """
+    def __init__(self, parts: List[RoadPart]):
+        self.parts: List[RoadPart] = sorted(parts, key=lambda x: x.get_angle())