feat: llm text stream support for workflow app (#3798)

Co-authored-by: JzoNg <jzongcode@gmail.com>

api/core/workflow/nodes/end/end_node.py

@@ -36,6 +36,49 @@ class EndNode(BaseNode):
             outputs=outputs
         )
 
+    @classmethod
+    def extract_generate_nodes(cls, graph: dict, config: dict) -> list[str]:
+        """
+        Extract generate nodes
+        :param graph: graph
+        :param config: node config
+        :return:
+        """
+        node_data = cls._node_data_cls(**config.get("data", {}))
+        node_data = cast(cls._node_data_cls, node_data)
+
+        return cls.extract_generate_nodes_from_node_data(graph, node_data)
+
+    @classmethod
+    def extract_generate_nodes_from_node_data(cls, graph: dict, node_data: EndNodeData) -> list[str]:
+        """
+        Extract generate nodes from node data
+        :param graph: graph
+        :param node_data: node data object
+        :return:
+        """
+        nodes = graph.get('nodes')
+        node_mapping = {node.get('id'): node for node in nodes}
+
+        variable_selectors = node_data.outputs
+
+        generate_nodes = []
+        for variable_selector in variable_selectors:
+            if not variable_selector.value_selector:
+                continue
+
+            node_id = variable_selector.value_selector[0]
+            if node_id != 'sys' and node_id in node_mapping:
+                node = node_mapping[node_id]
+                node_type = node.get('data', {}).get('type')
+                if node_type == NodeType.LLM.value and variable_selector.value_selector[1] == 'text':
+                    generate_nodes.append(node_id)
+
+        # remove duplicates
+        generate_nodes = list(set(generate_nodes))
+
+        return generate_nodes
+
     @classmethod
     def _extract_variable_selector_to_variable_mapping(cls, node_data: BaseNodeData) -> dict[str, list[str]]:
         """