Corrects nesting of referents

src/ifcopenshell-python/ifcopenshell/api/alignment/get_alignment_start_station.py

@@ -0,0 +1,48 @@
+# IfcOpenShell - IFC toolkit and geometry engine
+# Copyright (C) 2025 Thomas Krijnen <thomas@aecgeeks.com>
+#
+# This file is part of IfcOpenShell.
+#
+# IfcOpenShell is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Lesser General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# IfcOpenShell is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public License
+# along with IfcOpenShell.  If not, see <http://www.gnu.org/licenses/>.
+
+import ifcopenshell
+import ifcopenshell.api.alignment
+import ifcopenshell.util.element
+from ifcopenshell import entity_instance
+
+
+def get_alignment_start_station(file: ifcopenshell.file, alignment: entity_instance) -> float:
+    """
+    Returns the start station of the alignment. The starting station is defined by the first nested IfcReferent.
+    This is interpreted to mean the first IfcReferent with an occurance of Pset_Stationing.Station,
+    otherwise returns 0.0.
+    """
+
+    if not alignment.is_a("IfcAlignment"):
+        raise TypeError(f"Expected entity type to be IfcAlignment, instead received {alignment.is_a()}")
+
+    start_station = 0.0
+
+    parent_alignment = ifcopenshell.api.alignment.get_parent_alignment(alignment)
+    if parent_alignment:
+        start_station = ifcopenshell.api.alignment.get_alignment_start_station(file, parent_alignment)
+    else:
+        components = ifcopenshell.util.element.get_components(alignment)
+        for c in components:
+            if c.is_a("IfcReferent"):
+                start_station = ifcopenshell.util.element.get_pset(c, name="Pset_Stationing", prop="Station")
+                if not start_station == None:
+                    break
+
+    return start_station