Initial work on cable paths (WIP)

netbox/dcim/utils.py

@@ -0,0 +1,65 @@
+from django.contrib.contenttypes.models import ContentType
+
+from .models import FrontPort, RearPort
+
+
+def object_to_path_node(obj):
+    return f'{obj._meta.model_name}:{obj.pk}'
+
+
+def objects_to_path(*obj_list):
+    return [object_to_path_node(obj) for obj in obj_list]
+
+
+def path_node_to_object(repr):
+    model_name, object_id = repr.split(':')
+    model_class = ContentType.objects.get(model=model_name).model_class()
+    return model_class.objects.get(pk=int(object_id))
+
+
+def trace_paths(node):
+    destination = None
+    path = []
+    position_stack = []
+
+    if node.cable is None:
+        return []
+
+    while node.cable is not None:
+
+        # Follow the cable to its far-end termination
+        path.append(object_to_path_node(node.cable))
+        peer_termination = node.get_cable_peer()
+
+        # Follow a FrontPort to its corresponding RearPort
+        if isinstance(peer_termination, FrontPort):
+            path.append(object_to_path_node(peer_termination))
+            position_stack.append(peer_termination.rear_port_position)
+            node = peer_termination.rear_port
+            path.append(object_to_path_node(node))
+
+        # Follow a RearPort to its corresponding FrontPort
+        elif isinstance(peer_termination, RearPort):
+            path.append(object_to_path_node(peer_termination))
+            if position_stack:
+                position = position_stack.pop()
+                node = FrontPort.objects.get(rear_port=peer_termination, rear_port_position=position)
+                path.append(object_to_path_node(node))
+            else:
+                # No position indicated, so we have to trace _all_ peer FrontPorts
+                paths = []
+                for frontport in FrontPort.objects.filter(rear_port=peer_termination):
+                    branches = trace_paths(frontport)
+                    if branches:
+                        for branch, destination in branches:
+                            paths.append(([*path, object_to_path_node(frontport), *branch], destination))
+                    else:
+                        paths.append(([*path, object_to_path_node(frontport)], None))
+                return paths
+
+        # Anything else marks the end of the path
+        else:
+            destination = peer_termination
+            break
+
+    return [(path, destination)]