from sqlalchemy import create_engine
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker
import os
from pathlib import Path

# 计算项目根目录（backend/app/database.py -> yu-zhi-ran）
# __file__: platform/backend/app/database.py
# parents[0]=app, [1]=backend, [2]=platform, [3]=yu-zhi-ran
PROJECT_ROOT = Path(__file__).resolve().parents[3]
DATA_DIR = os.getenv('DATA_DIR', str(PROJECT_ROOT / 'data'))
os.makedirs(DATA_DIR, exist_ok=True)
DB_PATH = os.path.join(DATA_DIR, 'yzr.db')
SQLALCHEMY_DATABASE_URL = f"sqlite:///{DB_PATH}"

engine = create_engine(SQLALCHEMY_DATABASE_URL, connect_args={"check_same_thread": False})
SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
Base = declarative_base()

def init_db():
    Base.metadata.create_all(bind=engine)

def get_db():
    db = SessionLocal()
    try:
        yield db
    finally:
        db.close()