Fix simulation stopping condition

nozzlesim/mesh.py

@@ -80,13 +80,17 @@ def simulate(self, stop=float("inf")):
         """Propagate the mesh until no more events occur or ``stop`` is reached."""
 
         event = self.firstevent(self.activeshocks, self.x)
-        lastcheck = self.remainingangle <= 0
 
         while event is not None and self.x < stop:
+            currentx = event[1][2].x
             self.handleevent(event)
-            event = self.firstevent(self.activeshocks, self.x)
-            if lastcheck:
+            nextevent = self.firstevent(self.activeshocks, self.x)
+            while nextevent is not None and abs(nextevent[1][2].x - currentx) < epsilon:
+                self.handleevent(nextevent)
+                nextevent = self.firstevent(self.activeshocks, self.x)
+            if self.remainingangle <= 0:
                 return
+            event = nextevent
 
     @staticmethod
     def sortshocks(shocks, startx):

nozzlesim/wall.py

@@ -49,6 +49,32 @@ def createarc(
             segments.append(nextsegment)
         return segments, start.x + deltax * (numsegments + 1)
 
+    @classmethod
+    def create_symmetric_pair(
+        cls,
+        top_start: Point,
+        bottom_start: Point,
+        deltax: float,
+        totalangle: float,
+        numsegments: int,
+    ) -> tuple[list["Wall"], list["Wall"], float]:
+        """Return symmetric wall arcs for the top and bottom nozzle walls.
+
+        ``totalangle`` defines the turn of the top wall. The bottom wall will
+        mirror the top wall about the horizontal axis so the geometry is exactly
+        symmetric.
+        """
+
+        top_segments, endx = cls.createarc(top_start, deltax, totalangle, numsegments)
+        bottom_segments: list[Wall] = []
+        y_offset = top_start.y + bottom_start.y
+        for seg in top_segments:
+            start = Point(seg.start.x, -seg.start.y + y_offset)
+            end = None if seg.end is None else Point(seg.end.x, -seg.end.y + y_offset)
+            mirrored = cls(start, -seg.angle, end)
+            bottom_segments.append(mirrored)
+        return top_segments, bottom_segments, endx
+
     def exists(self, x: float) -> bool:
         """Return ``True`` if ``x`` lies between ``start`` and ``end`` (if defined)."""
 

tests/test_simulate_stop.py

@@ -0,0 +1,26 @@
+import nozzlesim.mesh as mesh_module
+
+
+class DummyMesh(mesh_module.Mesh):
+    def __init__(self):
+        # initialize with dummy values for parent
+        super().__init__(1.4, 1.0, [], [], 0, 1)
+        # minimal event objects with an ``x`` attribute in the expected place
+        from nozzlesim.point import Point
+
+        self.events = [["intersection", [None, None, Point(i, 0)]] for i in range(3)]
+        self.counter = 0
+
+    def firstevent(self, shocks, startx):
+        return self.events.pop(0) if self.events else None
+
+    def handleevent(self, event):
+        self.counter += 1
+        if self.counter == 2:
+            self.remainingangle = 0
+
+
+def test_simulate_stops_when_remainingangle_zero():
+    m = DummyMesh()
+    m.simulate()
+    assert m.counter == 2