structure saas with tools

.venv/lib/python3.10/site-packages/google/adk/agents/langgraph_agent.py

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+# Copyright 2025 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from typing import AsyncGenerator
+from typing import Union
+
+from google.genai import types
+from langchain_core.messages import AIMessage
+from langchain_core.messages import HumanMessage
+from langchain_core.messages import SystemMessage
+from langchain_core.runnables.config import RunnableConfig
+from langgraph.graph.graph import CompiledGraph
+from pydantic import ConfigDict
+from typing_extensions import override
+
+from ..events.event import Event
+from .base_agent import BaseAgent
+from .invocation_context import InvocationContext
+
+
+def _get_last_human_messages(events: list[Event]) -> list[HumanMessage]:
+  """Extracts last human messages from given list of events.
+
+  Args:
+    events: the list of events
+
+  Returns:
+    list of last human messages
+  """
+  messages = []
+  for event in reversed(events):
+    if messages and event.author != 'user':
+      break
+    if event.author == 'user' and event.content and event.content.parts:
+      messages.append(HumanMessage(content=event.content.parts[0].text))
+  return list(reversed(messages))
+
+
+class LangGraphAgent(BaseAgent):
+  """Currently a concept implementation, supports single and multi-turn."""
+
+  model_config = ConfigDict(
+      arbitrary_types_allowed=True,
+  )
+
+  graph: CompiledGraph
+
+  instruction: str = ''
+
+  @override
+  async def _run_async_impl(
+      self,
+      ctx: InvocationContext,
+  ) -> AsyncGenerator[Event, None]:
+
+    # Needed for langgraph checkpointer (for subsequent invocations; multi-turn)
+    config: RunnableConfig = {'configurable': {'thread_id': ctx.session.id}}
+
+    # Add instruction as SystemMessage if graph state is empty
+    current_graph_state = self.graph.get_state(config)
+    graph_messages = (
+        current_graph_state.values.get('messages', [])
+        if current_graph_state.values
+        else []
+    )
+    messages = (
+        [SystemMessage(content=self.instruction)]
+        if self.instruction and not graph_messages
+        else []
+    )
+    # Add events to messages (evaluating the memory used; parent agent vs checkpointer)
+    messages += self._get_messages(ctx.session.events)
+
+    # Use the Runnable
+    final_state = self.graph.invoke({'messages': messages}, config)
+    result = final_state['messages'][-1].content
+
+    result_event = Event(
+        invocation_id=ctx.invocation_id,
+        author=self.name,
+        branch=ctx.branch,
+        content=types.Content(
+            role='model',
+            parts=[types.Part.from_text(text=result)],
+        ),
+    )
+    yield result_event
+
+  def _get_messages(
+      self, events: list[Event]
+  ) -> list[Union[HumanMessage, AIMessage]]:
+    """Extracts messages from given list of events.
+
+    If the developer provides their own memory within langgraph, we return the
+    last user messages only. Otherwise, we return all messages between the user
+    and the agent.
+
+    Args:
+      events: the list of events
+
+    Returns:
+      list of messages
+    """
+    if self.graph.checkpointer:
+      return _get_last_human_messages(events)
+    else:
+      return self._get_conversation_with_agent(events)
+
+  def _get_conversation_with_agent(
+      self, events: list[Event]
+  ) -> list[Union[HumanMessage, AIMessage]]:
+    """Extracts messages from given list of events.
+
+    Args:
+      events: the list of events
+
+    Returns:
+      list of messages
+    """
+
+    messages = []
+    for event in events:
+      if not event.content or not event.content.parts:
+        continue
+      if event.author == 'user':
+        messages.append(HumanMessage(content=event.content.parts[0].text))
+      elif event.author == self.name:
+        messages.append(AIMessage(content=event.content.parts[0].text))
+    return messages