From e0bf0b8d797b41ac17a688b8e3da693e4bec6985 Mon Sep 17 00:00:00 2001
From: Alex Greason <quantum935@yahoo.com>
Date: Wed, 11 Jun 2025 20:47:26 -0500
Subject: [PATCH 1/2] fix simulation stop condition

---
 nozzlesim/mesh.py           |  1 +
 tests/test_simulate_stop.py | 23 +++++++++++++++++++++++
 2 files changed, 24 insertions(+)
 create mode 100644 tests/test_simulate_stop.py

diff --git a/nozzlesim/mesh.py b/nozzlesim/mesh.py
index 77869ff..27d1ed2 100644
--- a/nozzlesim/mesh.py
+++ b/nozzlesim/mesh.py
@@ -85,6 +85,7 @@ def simulate(self, stop=float("inf")):
         while event is not None and self.x < stop:
             self.handleevent(event)
             event = self.firstevent(self.activeshocks, self.x)
+            lastcheck = self.remainingangle <= 0
             if lastcheck:
                 return
 
diff --git a/tests/test_simulate_stop.py b/tests/test_simulate_stop.py
new file mode 100644
index 0000000..9b6301e
--- /dev/null
+++ b/tests/test_simulate_stop.py
@@ -0,0 +1,23 @@
+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)
+        self.events = ["e1", "e2", "e3"]
+        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

From ca50895ba0a40cf5d6553c8c89fe12a22cd18b70 Mon Sep 17 00:00:00 2001
From: Alex Greason <quantum935@yahoo.com>
Date: Wed, 11 Jun 2025 20:57:17 -0500
Subject: [PATCH 2/2] Implement symmetric arc helper and process simultaneous
 events

---
 nozzlesim/mesh.py           | 11 +++++++----
 nozzlesim/wall.py           | 26 ++++++++++++++++++++++++++
 tests/test_simulate_stop.py |  5 ++++-
 3 files changed, 37 insertions(+), 5 deletions(-)

diff --git a/nozzlesim/mesh.py b/nozzlesim/mesh.py
index 27d1ed2..ea6ac76 100644
--- a/nozzlesim/mesh.py
+++ b/nozzlesim/mesh.py
@@ -80,14 +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)
-            lastcheck = self.remainingangle <= 0
-            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):
diff --git a/nozzlesim/wall.py b/nozzlesim/wall.py
index 2bbad6d..f4d2dae 100644
--- a/nozzlesim/wall.py
+++ b/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)."""
 
diff --git a/tests/test_simulate_stop.py b/tests/test_simulate_stop.py
index 9b6301e..d98c68b 100644
--- a/tests/test_simulate_stop.py
+++ b/tests/test_simulate_stop.py
@@ -5,7 +5,10 @@ class DummyMesh(mesh_module.Mesh):
     def __init__(self):
         # initialize with dummy values for parent
         super().__init__(1.4, 1.0, [], [], 0, 1)
-        self.events = ["e1", "e2", "e3"]
+        # 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):