Issue #45: support parsing from tags.

roentgen/constructor.py

@@ -202,9 +202,12 @@ class Road(Figure):
         self.matcher: RoadMatcher = matcher
 
         self.width: Optional[float] = None
+        self.lanes: int = 1
+
         if "lanes" in tags:
             try:
                 self.width = float(tags["lanes"]) * 3.7
+                self.lanes = float(tags["lanes"])
             except ValueError:
                 pass
         if "width" in tags:

roentgen/road.py

@@ -2,12 +2,13 @@
 Road shape drawing.
 """
 from dataclasses import dataclass
-from typing import List
+from typing import List, Any, Dict
 
 import numpy as np
 import svgwrite
 from shapely.geometry import LineString, Point
 
+from roentgen.constructor import Road
 from roentgen.flinger import Flinger, angle, turn_by_angle, norm
 from roentgen.osm_reader import OSMNode
 
@@ -64,13 +65,15 @@ class RoadPart:
         node_1: OSMNode,
         node_2: OSMNode,
         flinger: Flinger,
-        left_offset: float,
+        road: Road,
-        right_offset: float,
-        lanes: List[Lane],
     ) -> "RoadPart":
         """
         Construct road part from OSM nodes.
         """
+        left_offset: float = road.width / 2
+        right_offset: float = road.width / 2
+        lanes = [Lane(road.width / road.lanes)] * road.lanes
+
         return cls(
             flinger.fling(node_1.coordinates),
             flinger.fling(node_2.coordinates),