chore: Add request converter to convert a2a request to ADK request

PiperOrigin-RevId: 773894462

Author: seanzhougoogle

src/google/adk/a2a/converters/request_converter.py

@@ -0,0 +1,90 @@
+# 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 __future__ import annotations
+
+import sys
+from typing import Any
+
+try:
+  from a2a.server.agent_execution import RequestContext
+except ImportError as e:
+  if sys.version_info < (3, 10):
+    raise ImportError(
+        'A2A Tool requires Python 3.10 or above. Please upgrade your Python'
+        ' version.'
+    ) from e
+  else:
+    raise e
+
+from google.genai import types as genai_types
+
+from ...runners import RunConfig
+from ...utils.feature_decorator import working_in_progress
+from .part_converter import convert_a2a_part_to_genai_part
+from .utils import _from_a2a_context_id
+from .utils import _get_adk_metadata_key
+
+
+def _get_user_id(request: RequestContext, user_id_from_context: str) -> str:
+  # Get user from call context if available (auth is enabled on a2a server)
+  if request.call_context and request.call_context.user:
+    return request.call_context.user.user_name
+
+  # Get user from context id if available
+  if user_id_from_context:
+    return user_id_from_context
+
+  # Get user from message metadata if available (client is an ADK agent)
+  if request.message.metadata:
+    user_id = request.message.metadata.get(_get_adk_metadata_key('user_id'))
+    if user_id:
+      return f'ADK_USER_{user_id}'
+
+  # Get user from task if available (client is a an ADK agent)
+  if request.current_task:
+    user_id = request.current_task.metadata.get(
+        _get_adk_metadata_key('user_id')
+    )
+    if user_id:
+      return f'ADK_USER_{user_id}'
+  return (
+      f'temp_user_{request.task_id}'
+      if request.task_id
+      else f'TEMP_USER_{request.message.messageId}'
+  )
+
+
+@working_in_progress
+def convert_a2a_request_to_adk_run_args(
+    request: RequestContext,
+) -> dict[str, Any]:
+
+  if not request.message:
+    raise ValueError('Request message cannot be None')
+
+  _, user_id, session_id = _from_a2a_context_id(request.context_id)
+
+  return {
+      'user_id': _get_user_id(request, user_id),
+      'session_id': session_id,
+      'new_message': genai_types.Content(
+          role='user',
+          parts=[
+              convert_a2a_part_to_genai_part(part)
+              for part in request.message.parts
+          ],
+      ),
+      'run_config': RunConfig(),
+  }

src/google/adk/a2a/converters/utils.py

@@ -15,6 +15,7 @@
 from __future__ import annotations
 
 ADK_METADATA_KEY_PREFIX = "adk_"
+ADK_CONTEXT_ID_PREFIX = "ADK"
 
 
 def _get_adk_metadata_key(key: str) -> str:
@@ -32,3 +33,39 @@ def _get_adk_metadata_key(key: str) -> str:
   if not key:
     raise ValueError("Metadata key cannot be empty or None")
   return f"{ADK_METADATA_KEY_PREFIX}{key}"
+
+
+def _to_a2a_context_id(app_name: str, user_id: str, session_id: str) -> str:
+  """Converts app name, user id and session id to an A2A context id.
+
+  Args:
+    app_name: The app name.
+    user_id: The user id.
+    session_id: The session id.
+
+  Returns:
+    The A2A context id.
+  """
+  return [ADK_CONTEXT_ID_PREFIX, app_name, user_id, session_id].join("$")
+
+
+def _from_a2a_context_id(context_id: str) -> tuple[str, str, str]:
+  """Converts an A2A context id to app name, user id and session id.
+  if context_id is None, return None, None, None
+  if context_id is not None, but not in the format of
+  ADK$app_name$user_id$session_id, return None, None, None
+
+  Args:
+    context_id: The A2A context id.
+
+  Returns:
+    The app name, user id and session id.
+  """
+  if not context_id:
+    return None, None, None
+
+  prefix, app_name, user_id, session_id = context_id.split("$")
+  if prefix == "ADK" and app_name and user_id and session_id:
+    return app_name, user_id, session_id
+
+  return None, None, None