from flask import Flask
from flask_sqlalchemy import SQLAlchemy
from flask_migrate import Migrate
from flask_login import LoginManager
from flask_session import Session
from config import config
from flask_bootstrap import Bootstrap

# 初始化扩展，但此时不传入 app
db = SQLAlchemy()
migrate = Migrate()
login_manager = LoginManager()
sess = Session()
bootstrap = Bootstrap()
# login_manager 的基本配置
login_manager.login_view = 'auth.login' # 后面我们会创建一个叫 'auth' 的蓝图

def create_app(config_name='default'):
    """
    应用工厂函数
    :param config_name: 配置名称 ('development', 'production')
    :return: Flask app instance
    """
    app = Flask(__name__)
    
    # 1. 加载配置
    app.config.from_object(config[config_name])
    config[config_name].init_app(app)
    # 2. 初始化扩展
    db.init_app(app)
    migrate.init_app(app, db)
    login_manager.init_app(app)
    sess.init_app(app)
    bootstrap.init_app(app)
    
    # 3. 注册蓝图 (Blueprint)
    # 后面我们会在这里添加蓝图
    from .routes import main as main_blueprint
    app.register_blueprint(main_blueprint)
    
    from .auth import auth as auth_blueprint
    app.register_blueprint(auth_blueprint, url_prefix='/auth')
    
    return app