show error if transition length is more the segments length

src/blenderbim/blenderbim/bim/module/model/mep.py

@@ -642,10 +642,22 @@ class MEPAddTransition(bpy.types.Operator, tool.Ifc.Operator):
             end_segment_data["end_point"]: end_segment_data["end_port"],
         }
 
+        # transition points
         start_point, end_point = tool.Cad.closest_points(
             (start_segment_data["start_point"], start_segment_data["end_point"]),
             (end_segment_data["start_point"], end_segment_data["end_point"]),
         )
+        
+        first_segment_start, second_segment_end = [
+            p for p in (
+            start_segment_data["start_point"], 
+            start_segment_data["end_point"],
+            end_segment_data["start_point"], 
+            end_segment_data["end_point"])
+            if p not in (start_point, end_point)
+        ]
+        entire_length = (first_segment_start - second_segment_end).length
+
         transition_dir = (end_point - start_point).normalized()
         start_port = points_ports_map[start_point]
         end_port = points_ports_map[end_point]
@@ -659,9 +671,16 @@ class MEPAddTransition(bpy.types.Operator, tool.Ifc.Operator):
         if not rep:
             self.report({"ERROR"}, f"Failed to add transition - this kind of profiles is not yet supported.")
             return {"CANCELLED"}
+        
+        # TODO: test it
+        full_transition_length = transition_data["full_transition_length"] * si_conversion
+        if full_transition_length >= entire_length:
+            self.report({"ERROR"}, f"Failed to add transition - transition length is larger the segments and the distance between them.")
+            # TODO: handle the case without creating representation in the first place?
+            ifcopenshell.api.run("geometry.remove_representation", ifc_file, representation=rep)
+            return {"CANCELLED"}
 
         middle_point = (start_point + end_point) / 2
-        full_transition_length = transition_data["full_transition_length"] * si_conversion
         start_segment_extend_point = middle_point - transition_dir * full_transition_length / 2
         end_segment_extend_point = middle_point + transition_dir * full_transition_length / 2
         DumbProfileJoiner().join_E(start_object, start_segment_extend_point)

src/blenderbim/blenderbim/tool/cad.py

@@ -252,7 +252,7 @@ class Cad:
         return False
 
     @classmethod
-    def closest_points(cls, edge1, edge2):
+    def closest_points(cls, edge1, edge2) -> bool:
         """
 
         closest end points between `edge1` and `edge2` assuming `edge1` and `edge2` are collinear.
@@ -263,15 +263,12 @@ class Cad:
         direction = (edge1[1] - edge1[0]).normalized()
 
         # Project points onto the line to get scalar values along the direction
-        points1_values = [(p, p.dot(direction)) for p in edge1]
-        points2_values = [(p, p.dot(direction)) for p in edge2]
+        points_values = [(p, p.dot(direction)) for p in (edge1 + edge2)]
+        sorted_points = sorted(points_values, key=lambda el: el[1])
 
-        # Sort the projections for both edges
-        sorted_points1 = sorted(points1_values, key=lambda el: el[1])
-        sorted_points2 = sorted(points2_values, key=lambda el: el[1])
-
-        # The closest points will be the last point of the first edge and the first point of the second edge
-        return sorted_points1[-1][0], sorted_points2[0][0]
+        edge1_point = next((p for p, v in sorted_points[1:3] if p in edge1), None)
+        edge2_point = next((p for p, v in sorted_points[1:3] if p in edge2), None)
+        return edge1_point, edge2_point
 
     @classmethod
     def find_intersecting_edges(cls, bm, pt, idx1, idx2):