# File: backend/app/api/v1/endpoints/chat.py (Update with DB session dependency)
# Description: 聊天功能的 API 路由 (使用数据库会话)

from fastapi import APIRouter, HTTPException, Depends, status
from sqlalchemy.ext.asyncio import AsyncSession
from app.db.database import get_db_session
from app.models.pydantic_models import ChatRequest, ChatResponse, SessionCreateRequest
from app.services.chat_service import ChatService # Import class
from app.services.session_service import SessionService # Import class
import app.core.config as Config # Import API Key for ChatService instantiation

router = APIRouter()

# --- Dependency Injection ---
# Instantiate services here or use a more sophisticated dependency injection system
chat_service = ChatService(default_api_key=Config.GOOGLE_API_KEY)
session_service = SessionService()

@router.post("/", response_model=ChatResponse)
async def handle_chat_message(
    request: ChatRequest,
    db: AsyncSession = Depends(get_db_session) # Inject DB session
):
    user_message = request.message
    session_id = request.session_id
    assistant_id = request.assistant_id

    print(f"接收到消息: User='{user_message}', Session='{session_id}', Assistant='{assistant_id}'")

    response_session_id = None
    response_session_title = None

    if session_id == 'temp-new-chat':
        print("检测到临时新会话，正在创建...")
        try:
            create_req = SessionCreateRequest(assistant_id=assistant_id, first_message=user_message)
            # Pass db session to the service method
            created_session = await session_service.create_session(db, create_req)
            session_id = created_session.id
            response_session_id = created_session.id
            response_session_title = created_session.title
            print(f"新会话已创建: ID={session_id}, Title='{created_session.title}'")
        except ValueError as e:
            raise HTTPException(status_code=status.HTTP_400_BAD_REQUEST, detail=str(e))
        except Exception as e:
            print(f"创建会话时出错: {e}")
            raise HTTPException(status_code=status.HTTP_500_INTERNAL_SERVER_ERROR, detail="创建会话失败")

    try:
        # Pass db session to the service method
        ai_reply = await chat_service.get_ai_reply(
            db=db,
            user_message=user_message,
            session_id=session_id,
            assistant_id=assistant_id
        )
        print(f"发送 AI 回复: '{ai_reply}'")
        return ChatResponse(
            reply=ai_reply,
            session_id=response_session_id,
            session_title=response_session_title
        )
    except ValueError as e:
         raise HTTPException(status_code=status.HTTP_400_BAD_REQUEST, detail=str(e))
    except Exception as e:
        print(f"处理聊天消息时发生错误: {e}")
        # The get_db_session dependency will handle rollback
        raise HTTPException(status_code=status.HTTP_500_INTERNAL_SERVER_ERROR, detail=str(e))