From 9ebd02e331052549135ab7698bb6a70b342e89c0 Mon Sep 17 00:00:00 2001
From: Gabriel Luiz Freitas Almeida <gabriel@logspace.ai>
Date: Mon, 12 Jun 2023 07:49:35 -0300
Subject: [PATCH] =?UTF-8?q?=F0=9F=9A=80=20feat(base.py):=20add=20topologic?=
 =?UTF-8?q?al=5Fsort=20method=20to=20perform=20a=20topological=20sort=20of?=
 =?UTF-8?q?=20the=20vertices=20in=20the=20graph=20=F0=9F=9A=80=20feat(base?=
 =?UTF-8?q?.py):=20add=20generator=5Fbuild=20method=20to=20build=20each=20?=
 =?UTF-8?q?node=20in=20the=20graph=20and=20yield=20it=20The=20topological?=
 =?UTF-8?q?=5Fsort=20method=20performs=20a=20topological=20sort=20of=20the?=
 =?UTF-8?q?=20vertices=20in=20the=20graph,=20returning=20a=20list=20of=20v?=
 =?UTF-8?q?ertices=20in=20topological=20order.=20The=20generator=5Fbuild?=
 =?UTF-8?q?=20method=20builds=20each=20node=20in=20the=20graph=20and=20yie?=
 =?UTF-8?q?lds=20it.=20These=20methods=20are=20useful=20for=20building=20t?=
 =?UTF-8?q?he=20graph=20in=20a=20specific=20order,=20which=20is=20importan?=
 =?UTF-8?q?t=20for=20certain=20algorithms=20that=20rely=20on=20the=20order?=
 =?UTF-8?q?=20of=20the=20nodes.?=
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---
 src/backend/langflow/graph/graph/base.py | 42 ++++++++++++++++++++++++
 1 file changed, 42 insertions(+)

diff --git a/src/backend/langflow/graph/graph/base.py b/src/backend/langflow/graph/graph/base.py
index 1e9d1f10f..dba948693 100644
--- a/src/backend/langflow/graph/graph/base.py
+++ b/src/backend/langflow/graph/graph/base.py
@@ -107,6 +107,48 @@ class Graph:
             raise ValueError("No root node found")
         return root_node.build()
 
+    def topological_sort(self) -> List[Vertex]:
+        """
+        Performs a topological sort of the vertices in the graph.
+
+        Returns:
+            List[Vertex]: A list of vertices in topological order.
+
+        Raises:
+            ValueError: If the graph contains a cycle.
+        """
+        # States: 0 = unvisited, 1 = visiting, 2 = visited
+        state = {node: 0 for node in self.nodes}
+        sorted_vertices = []
+
+        def dfs(node):
+            if state[node] == 1:
+                # We have a cycle
+                raise ValueError(
+                    "Graph contains a cycle, cannot perform topological sort"
+                )
+            if state[node] == 0:
+                state[node] = 1
+                for edge in node.edges:
+                    if edge.source == node:
+                        dfs(edge.target)
+                state[node] = 2
+                sorted_vertices.append(node)
+
+        # Visit each node
+        for node in self.nodes:
+            if state[node] == 0:
+                dfs(node)
+
+        return list(reversed(sorted_vertices))
+
+    def generator_build(self) -> List[Vertex]:
+        """Builds each
+        node in the graph and yields it."""
+        sorted_vertices = self.topological_sort()
+        for node in sorted_vertices:
+            yield node.build()
+
     def get_node_neighbors(self, node: Vertex) -> Dict[Vertex, int]:
         """Returns the neighbors of a node."""
         neighbors: Dict[Vertex, int] = {}