[Fix] Update Node depth when adding new Edges to a Pathway (#384)

Co-authored-by: Tim Lorsbach <tim@lorsba.ch>
Reviewed-on: enviPath/enviPy#384

epdb/models.py

@@ -2178,6 +2178,52 @@ class Pathway(EnviPathModel, AliasMixin, ScenarioMixin, AdditionalInformationMix
     ):
         return Edge.create(self, start_nodes, end_nodes, rule, name=name, description=description)
 
+    def update_depths(self):
+        in_count = defaultdict(lambda: 0)
+        out_count = defaultdict(lambda: 0)
+
+        for e in self.edges:
+            # TODO check if this will remain
+            for react in e.start_nodes.all():
+                out_count[str(react.uuid)] += 1
+
+            for prod in e.end_nodes.all():
+                in_count[str(prod.uuid)] += 1
+
+        root_nodes = []
+        for n in self.nodes:
+            num_parents = in_count[str(n.uuid)]
+            if num_parents == 0:
+                # must be a root node or unconnected node
+                if n.depth != 0:
+                    n.depth = 0
+                    n.save()
+
+                # Only root node may have children
+                if out_count[str(n.uuid)] > 0:
+                    root_nodes.append(n)
+
+        levels = [root_nodes]
+        seen = set()
+        # Do a bfs to determine depths starting with level 0 a.k.a. root nodes
+        for i, level_nodes in enumerate(levels):
+            new_level = []
+            for n in level_nodes:
+                for e in n.out_edges.all():
+                    for prod in e.end_nodes.all():
+                        if str(prod.uuid) not in seen:
+                            old_depth = prod.depth
+                            if old_depth != i + 1:
+                                prod.depth = i + 1
+                                prod.save()
+
+                            new_level.append(prod)
+
+                seen.add(str(n.uuid))
+
+            if new_level:
+                levels.append(new_level)
+
 
 class Node(EnviPathModel, AliasMixin, ScenarioMixin, AdditionalInformationMixin):
     pathway = models.ForeignKey(