import json
import logging
from typing import AsyncGenerator
from contextlib import asynccontextmanager

from fastapi import FastAPI, HTTPException, Depends
from fastapi.middleware.cors import CORSMiddleware
from fastapi.responses import StreamingResponse

from google.adk.runners import Runner
from google.adk.agents.run_config import RunConfig, StreamingMode
from google.genai import types

from app.config import settings

from app.services import (
    get_session_service, 
    init_session_service, 
    close_session_service
)
from app.agent_factory import create_agent

# Routers
from app.routers.agents import router as agents_router
from app.routers.sessions import router as sessions_router
from app.routers.tools import router as tools_router


# --- Logging Configuration ---

# --- Logging Configuration ---
logging.basicConfig(
    level=logging.INFO,
    format="%(asctime)s - %(name)s - %(levelname)s - %(message)s"
)
logger = logging.getLogger(__name__)


# --- Application Lifespan ---
@asynccontextmanager
async def lifespan(app: FastAPI):
    """Application lifespan manager for startup/shutdown events."""
    logger.info("Starting up ADK Chat Backend...")
    await init_session_service()
    logger.info("Application started successfully")
    yield
    logger.info("Shutting down ADK Chat Backend...")
    await close_session_service()
    logger.info("Application shutdown complete")


app = FastAPI(
    title="ADK Enterprise Chat Backend",
    description="LLM Chat backend powered by Google ADK with PostgreSQL persistence",
    version="2.0.0",
    lifespan=lifespan
)


# --- CORS Configuration ---
app.add_middleware(
    CORSMiddleware,
    allow_origins=["*"],
    allow_credentials=True,
    allow_methods=["*"],
    allow_headers=["*"],
)


# --- Register Routers ---
app.include_router(agents_router)
app.include_router(sessions_router)
app.include_router(tools_router)


# --- Helper ---
def get_streaming_mode(mode_str: str) -> StreamingMode:
    return StreamingMode.SSE if mode_str.lower() == "sse" else StreamingMode.NONE