import logging
from flask import Flask
from .config import Config
from .extensions import init_extensions, register_namespaces, close_extensions
from .views import register_blueprints
import atexit
import logging
import signal
import threading

_shutdown_once = threading.Event()

def _graceful_shutdown(app: Flask, signum: str = "atexit"):
    # 防止重复执行
    if _shutdown_once.is_set():
        return
    _shutdown_once.set()

    app.logger.info("Shutting down gracefully (%s)...", signum)
    try:
        close_extensions()
    finally:
        app.logger.info("Cleanup finished (%s).", signum)

def _bind_signals(app: Flask):
    def handler(sig, frame):
        _graceful_shutdown(app, signum=sig)
        # 不要在这里强行 os._exit(0)，让外层管理器决定何时真正退出
    for s in (signal.SIGINT, signal.SIGTERM, getattr(signal, "SIGQUIT", None)):
        if s is not None:
            try:
                signal.signal(s, handler)
            except Exception:
                # 某些环境不能重绑定（如部分 WSGI 容器内），忽略
                pass

def create_app(config_object: type = Config) -> Flask:
    app = Flask(__name__, template_folder="templates", static_folder="static")
    app.config.from_object(config_object)

    # secret_key 从 config 里来
    app.secret_key = app.config["SECRET_KEY"]

    # logging
    app.logger.setLevel(logging.DEBUG)


    register_namespaces(app)

    # 1) 初始化第三方扩展（db、cache、jwt、cors 等）
    init_extensions(app)


    # 2) 注册蓝图（把子文件暴露的蓝图统一挂到 app 上）
    register_blueprints(app)

    # 3) 其他钩子/命令/错误处理
    @app.route("/healthz")
    def healthz():
        return {"status": "ok"}

        
    # 绑定退出钩子（开发/简单部署环境很有用）
    atexit.register(_graceful_shutdown, app, "atexit")
    _bind_signals(app)

    return app