wip: implement websocket chat service with Pydantic models and session management

app/main.py

@@ -1,4 +1,3 @@
-from starlette.templating import _TemplateResponse
 from contextlib import asynccontextmanager
 from pathlib import Path
 
@@ -9,7 +8,9 @@ from fastapi.templating import Jinja2Templates
 from rotoger import get_logger
 from starlette.middleware import Middleware
 from starlette.middleware.gzip import GZipMiddleware
+from starlette.templating import _TemplateResponse
 
+from app.api.chat import router as chat_ws_router
 from app.api.health import router as health_router
 from app.api.ml import router as ml_router
 from app.api.nonsense import router as nonsense_router
@@ -21,6 +22,8 @@ from app.exception_handlers import register_exception_handlers
 from app.middleware.profiler import ProfilingMiddleware
 from app.redis import get_redis
 from app.services.auth import AuthBearer
+from app.services.chat_agent import build_chat_agent
+from app.services.chat_session import ChatSessionManager
 
 templates = Jinja2Templates(directory=Path(__file__).parent.parent / "templates")
 
@@ -30,21 +33,27 @@ async def lifespan(app: FastAPI):
     app.logger = get_logger()
     app.redis = await get_redis()
     postgres_dsn = global_settings.postgres_url.unicode_string()
+    # Chat service: initialize the pluggable model-client adapter and the
+    # in-memory session manager. See app/services/chat_agent.py to swap the
+    # local stub for a real model client (OpenAI, Ollama, etc.).
+    app.chat_agent = build_chat_agent(global_settings.chat)
+    app.chat_sessions = ChatSessionManager()
     try:
-        app.postgres_pool = await asyncpg.create_pool(
-            dsn=postgres_dsn,
-            min_size=5,
-            max_size=20,
-        )
-        await app.logger.ainfo(
-            "Postgres pool created", idle_size=app.postgres_pool.get_idle_size()
-        )
+        # app.postgres_pool = await asyncpg.create_pool(
+        #     dsn=postgres_dsn,
+        #     min_size=5,
+        #     max_size=20,
+        # )
+        # await app.logger.ainfo(
+        #     "Postgres pool created", idle_size=app.postgres_pool.get_idle_size()
+        # )
         yield
     except Exception as e:
         await app.logger.aerror("Error during app startup", error=repr(e))
         raise
     finally:
         await app.redis.close()
+        await app.chat_agent.aclose()
         # await app.postgres_pool.close()
 
 
@@ -66,6 +75,7 @@ def create_app() -> FastAPI:
     app.include_router(shakespeare_router)
     app.include_router(user_router)
     app.include_router(ml_router, prefix="/v1/ml", tags=["ML"])
+    app.include_router(chat_ws_router, prefix="/v1/chat", tags=["Chat"])
     app.include_router(
         health_router, prefix="/v1/public/health", tags=["Health, Public"]
     )