feat: Add service factory for configurable session and artifact backends

this creates service_factory to handle .adk folder changes (including per-agent .adk defaults and in-memory/custom URI handling)

Co-authored-by: George Weale <gweale@google.com>
PiperOrigin-RevId: 833875524

Author: GWeale

src/google/adk/cli/service_registry.py

@@ -66,10 +66,12 @@ def my_session_factory(uri: str, **kwargs):
 import importlib
 import logging
 import os
+from pathlib import Path
 import sys
 from typing import Any
 from typing import Optional
 from typing import Protocol
+from urllib.parse import unquote
 from urllib.parse import urlparse
 
 from ..artifacts.base_artifact_service import BaseArtifactService
@@ -218,6 +220,11 @@ def _register_builtin_services(registry: ServiceRegistry) -> None:
   """Register built-in service implementations."""
 
   # -- Session Services --
+  def memory_session_factory(uri: str, **kwargs):
+    from ..sessions.in_memory_session_service import InMemorySessionService
+
+    return InMemorySessionService()
+
   def agentengine_session_factory(uri: str, **kwargs):
     from ..sessions.vertex_ai_session_service import VertexAiSessionService
 
@@ -240,19 +247,26 @@ def sqlite_session_factory(uri: str, **kwargs):
     parsed = urlparse(uri)
     db_path = parsed.path
     if not db_path:
-      return InMemorySessionService()
+      # Treat sqlite:// without a path as an in-memory session service.
+      return memory_session_factory("memory://", **kwargs)
     elif db_path.startswith("/"):
       db_path = db_path[1:]
     kwargs_copy = kwargs.copy()
     kwargs_copy.pop("agents_dir", None)
     return SqliteSessionService(db_path=db_path, **kwargs_copy)
 
+  registry.register_session_service("memory", memory_session_factory)
   registry.register_session_service("agentengine", agentengine_session_factory)
   registry.register_session_service("sqlite", sqlite_session_factory)
   for scheme in ["postgresql", "mysql"]:
     registry.register_session_service(scheme, database_session_factory)
 
   # -- Artifact Services --
+  def memory_artifact_factory(uri: str, **kwargs):
+    from ..artifacts.in_memory_artifact_service import InMemoryArtifactService
+
+    return InMemoryArtifactService()
+
   def gcs_artifact_factory(uri: str, **kwargs):
     from ..artifacts.gcs_artifact_service import GcsArtifactService
 
@@ -262,15 +276,35 @@ def gcs_artifact_factory(uri: str, **kwargs):
     bucket_name = parsed_uri.netloc
     return GcsArtifactService(bucket_name=bucket_name, **kwargs_copy)
 
+  def file_artifact_factory(uri: str, **kwargs):
+    from ..artifacts.file_artifact_service import FileArtifactService
+
+    per_agent = kwargs.get("per_agent", False)
+    if per_agent:
+      raise ValueError(
+          "file:// artifact URIs are not supported in multi-agent mode."
+      )
+    parsed_uri = urlparse(uri)
+    if parsed_uri.netloc not in ("", "localhost"):
+      raise ValueError(
+          "file:// artifact URIs must reference the local filesystem."
+      )
+    if not parsed_uri.path:
+      raise ValueError("file:// artifact URIs must include a path component.")
+    artifact_path = Path(unquote(parsed_uri.path))
+    return FileArtifactService(root_dir=artifact_path)
+
+  registry.register_artifact_service("memory", memory_artifact_factory)
   registry.register_artifact_service("gs", gcs_artifact_factory)
+  registry.register_artifact_service("file", file_artifact_factory)
 
   # -- Memory Services --
   def rag_memory_factory(uri: str, **kwargs):
     from ..memory.vertex_ai_rag_memory_service import VertexAiRagMemoryService
 
     rag_corpus = urlparse(uri).netloc
     if not rag_corpus:
-      raise ValueError("Rag corpus cannot be empty.")
+      raise ValueError("Rag corpus can not be empty.")
     agents_dir = kwargs.get("agents_dir")
     project, location = _load_gcp_config(agents_dir, "RAG memory service")
     return VertexAiRagMemoryService(