feat(api): Add a method for extract a node configration from workflow

api/models/_workflow_exc.py

@@ -0,0 +1,20 @@
+"""All these exceptions are not meant to be caught by callers."""
+
+
+class WorkflowDataError(Exception):
+    """Base class for all workflow data related exceptions.
+
+    This should be used to indicate issues with workflow data integrity, such as
+    no `graph` configuration, missing `nodes` field in `graph` configuration, or
+    similar issues.
+    """
+
+    pass
+
+
+class NodeNotFoundError(WorkflowDataError):
+    """Raised when a node with the specified ID is not found in the workflow."""
+
+    def __init__(self, node_id: str):
+        super().__init__(f"Node with ID '{node_id}' not found in the workflow.")
+        self.node_id = node_id

api/models/workflow.py

@@ -12,6 +12,8 @@ from core.variables import utils as variable_utils
 from core.workflow.constants import CONVERSATION_VARIABLE_NODE_ID, SYSTEM_VARIABLE_NODE_ID
 from factories.variable_factory import build_segment
 
+from ._workflow_exc import NodeNotFoundError, WorkflowDataError
+
 if TYPE_CHECKING:
     from models.model import AppMode
 
@@ -201,6 +203,26 @@ class Workflow(Base):
         # - `_get_graph_and_variable_pool_of_single_loop`.
         return json.loads(self.graph) if self.graph else {}
 
+    def get_node_config_by_id(self, node_id: str) -> Mapping[str, Any]:
+        """Extract a node configuration from the workflow graph by node ID.
+        A node configuration is a dictionary containing the node's properties, including
+        the node's id, title, and its data as a dict.
+        """
+        workflow_graph = self.graph_dict
+
+        if not workflow_graph:
+            raise WorkflowDataError(f"workflow graph not found, workflow_id={self.id}")
+
+        nodes = workflow_graph.get("nodes")
+        if not nodes:
+            raise WorkflowDataError("nodes not found in workflow graph")
+
+        try:
+            node_config = next(filter(lambda node: node["id"] == node_id, nodes))
+        except StopIteration:
+            raise NodeNotFoundError(node_id)
+        return node_config
+
     @property
     def features(self) -> str:
         """
@@ -955,7 +977,7 @@ class WorkflowDraftVariable(Base):
     def _set_selector(self, value: list[str]):
         self.selector = json.dumps(value)
 
-    def get_value(self) -> Segment | None:
+    def get_value(self) -> Segment:
         return build_segment(json.loads(self.value))
 
     def set_name(self, name: str):
@@ -1009,12 +1031,14 @@ class WorkflowDraftVariable(Base):
         app_id: str,
         name: str,
         value: Segment,
+        description: str = "",
     ) -> "WorkflowDraftVariable":
         variable = cls._new(
             app_id=app_id,
             node_id=CONVERSATION_VARIABLE_NODE_ID,
             name=name,
             value=value,
+            description=description,
         )
         return variable