from sqlalchemy.ext.asyncio import async_sessionmaker, AsyncSession, create_async_engine
# 數(shù)據(jù)庫URL
ASYNC_DATABASE_URL = "mysql+aiomysql://root:123456@localhost:3306/pdf_agent?charset=utf8mb4"
# 創(chuàng)建異步引擎
async_engine = create_async_engine(
    ASYNC_DATABASE_URL,  # 傳入數(shù)據(jù)庫連接 URL
    echo=True,  # 可選：開啟 SQL 日志輸出，便于調(diào)試
    pool_size=10,  # 設(shè)置連接池中保持的持久連接數(shù)為 10
    max_overflow=20  # 設(shè)置連接池允許創(chuàng)建的額外連接數(shù)最大為 20
)
# 創(chuàng)建異步會(huì)話工廠
AsyncSessionLocal = async_sessionmaker(
    bind=async_engine,  # 綁定到之前創(chuàng)建的異步引擎
    class_=AsyncSession,  # 指定會(huì)話類為 AsyncSession
    expire_on_commit=False  # 提交后不使對(duì)象屬性過期，保持?jǐn)?shù)據(jù)可訪問
)
# 依賴項(xiàng)，用于獲取數(shù)據(jù)庫會(huì)話
async def get_db():
    async with AsyncSessionLocal() as session:
        try:
            yield session  # 將會(huì)話對(duì)象產(chǎn)出給調(diào)用者，暫停函數(shù)執(zhí)行直到請(qǐng)求結(jié)束
            await session.commit()  # 如果無異常，提交事務(wù)
        except Exception:
            await session.rollback()  # 發(fā)生異常時(shí)回滾事務(wù)
            raise  # 重新拋出異常以便上層處理
        finally:
            await session.close()  # 關(guān)閉會(huì)話，釋放資源

from datetime import datetime, UTC
from sqlalchemy import DateTime, String, Integer
from sqlalchemy.orm import DeclarativeBase, Mapped, mapped_column

def utc_now() -> datetime:
    return datetime.now(UTC)

class Base(DeclarativeBase):
    # 創(chuàng)建時(shí)間：默認(rèn)UTC時(shí)間，北京時(shí)間 = UTC + 8 小時(shí)
    # UTC 是全球統(tǒng)一的標(biāo)準(zhǔn)時(shí)間基準(zhǔn)，是互聯(lián)網(wǎng)、服務(wù)器、數(shù)據(jù)庫、日志、GPS、國際業(yè)務(wù)通用時(shí)間
    created_at: Mapped[datetime] = mapped_column(
        DateTime,
        default=utc_now,
        comment="創(chuàng)建時(shí)間(UTC)"
    )
    # 更新時(shí)間：新增默認(rèn)賦值 + 每次update自動(dòng)刷新
    updated_at: Mapped[datetime] = mapped_column(
        DateTime,
        default=utc_now,
        onupdate=utc_now,
        comment="更新時(shí)間(UTC)"
    )

from sqlalchemy import Integer, String, Float

class User(Base):
    # 數(shù)據(jù)庫表名
    __tablename__ = "t_user"

    # 字段定義：Mapped 標(biāo)注類型，mapped_column 配置字段屬性
    id: Mapped[int] = mapped_column(
        Integer,
        primary_key=True,
        autoincrement=True,
        name="user_id",
        comment="用戶編號(hào)"
    )
    name: Mapped[str] = mapped_column(
        String(20),
        name="user_name",
        nullable=False,
        comment="用戶名"
    )
    password: Mapped[str] = mapped_column(
        String(20),
        name="user_password",
        nullable=False,
        comment="密碼"
    )

from backend.db_models.db_file import Base
from backend.config.db_conf import async_engine

# 定義異步建表函數(shù)
async def create_tables():
    async with async_engine.begin() as conn:
        # run_sync包裹同步的create_all，創(chuàng)建所有繼承Base的表）
        await conn.run_sync(Base.metadata.create_all)

# FastAPI 啟動(dòng)事件：服務(wù)運(yùn)行自動(dòng)執(zhí)行建表
@app.on_event("startup")
async def startup_event():
    await create_tables()