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MeetSpot/app/db/database.py

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+"""数据库引擎与会话管理。
+
+使用SQLite作为MVP默认存储，保留通过环境变量`DATABASE_URL`切换到PostgreSQL的能力。
+"""
+
+import os
+from pathlib import Path
+from typing import AsyncGenerator
+
+from sqlalchemy.ext.asyncio import AsyncSession, async_sessionmaker, create_async_engine
+from sqlalchemy.orm import declarative_base
+
+
+# 项目根目录，默认将SQLite数据库放在data目录下
+PROJECT_ROOT = Path(__file__).resolve().parent.parent.parent
+DATA_DIR = PROJECT_ROOT / "data"
+DATA_DIR.mkdir(exist_ok=True)
+
+# 允许通过环境变量覆盖数据库连接串
+DEFAULT_SQLITE_PATH = DATA_DIR / "meetspot.db"
+DATABASE_URL = os.getenv(
+    "DATABASE_URL", f"sqlite+aiosqlite:///{DEFAULT_SQLITE_PATH.as_posix()}"
+)
+
+# 创建异步引擎与会话工厂
+engine = create_async_engine(DATABASE_URL, echo=False, future=True)
+AsyncSessionLocal = async_sessionmaker(
+    bind=engine, class_=AsyncSession, expire_on_commit=False, autoflush=False
+)
+
+# 统一的ORM基类
+Base = declarative_base()
+
+
+async def get_db() -> AsyncGenerator[AsyncSession, None]:
+    """FastAPI 依赖：提供数据库会话并确保正确关闭。"""
+    async with AsyncSessionLocal() as session:
+        yield session
+
+
+async def init_db() -> None:
+    """在启动时创建数据库表。"""
+    # 延迟导入以避免循环依赖
+    from app import models  # noqa: F401  确保所有模型已注册
+
+    async with engine.begin() as conn:
+        await conn.run_sync(Base.metadata.create_all)
+