"""
应用工厂模式 - 创建和配置 FastAPI 应用实例
"""
from fastapi import FastAPI
from fastapi.middleware.cors import CORSMiddleware
from app.core.config import settings


def create_application() -> FastAPI:
    """
    创建 FastAPI 应用实例

    Returns:
        FastAPI: 配置完成的应用实例
    """
    app = FastAPI(
        title=settings.PROJECT_NAME,
        version=settings.VERSION,
        description=settings.DESCRIPTION,
        debug=settings.DEBUG,
        docs_url=settings.DOCS_URL,
        redoc_url=settings.REDOC_URL
    )

    # 设置中间件
    setup_middleware(app)

    # 注册路由
    register_routers(app)

    # 注册事件处理器
    register_events(app)

    return app


def setup_middleware(app: FastAPI) -> None:
    """
    配置应用中间件

    Args:
        app: FastAPI 应用实例
    """
    # CORS 中间件配置
    app.add_middleware(
        CORSMiddleware,
        allow_origins=settings.CORS_ORIGINS,
        allow_credentials=settings.CORS_ALLOW_CREDENTIALS,
        allow_methods=settings.CORS_ALLOW_METHODS,
        allow_headers=settings.CORS_ALLOW_HEADERS,
    )

    # 可以在这里添加其他中间件
    # app.add_middleware(...)


def register_routers(app: FastAPI) -> None:
    """
    注册所有路由

    Args:
        app: FastAPI 应用实例
    """
    from app.api.v1.router import api_router

    # 注册 API v1 路由
    app.include_router(api_router, prefix="/api/v1")

    # 根路径路由
    @app.get("/")
    async def root():
        return {
            "message": "Welcome to FastAPI Demo",
            "version": settings.VERSION,
            "docs": "/docs",
            "redoc": "/redoc"
        }

    # 健康检查路由
    @app.get("/health")
    async def health_check():
        return {"status": "healthy", "service": settings.PROJECT_NAME}


def register_events(app: FastAPI) -> None:
    """
    注册应用事件处理器

    Args:
        app: FastAPI 应用实例
    """
    @app.on_event("startup")
    async def startup_event():
        """应用启动时执行"""
        print(f"[INFO] {settings.PROJECT_NAME} v{settings.VERSION} is starting up...")
        # 可以在这里添加启动时的初始化操作
        # 如：数据库连接、缓存初始化等
        
        # 创建数据库表（如果不存在）
        from app.database.connection import engine
        from app.database.models import Base
        Base.metadata.create_all(bind=engine)
        print("[INFO] Database tables created/verified successfully")

    @app.on_event("shutdown")
    async def shutdown_event():
        """应用关闭时执行"""
        print(f"[INFO] {settings.PROJECT_NAME} is shutting down...")
        # 可以在这里添加关闭时的清理操作
        # 如：关闭数据库连接、保存缓存等