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）
PROJECT_ROOT = Path(__file__).resolve().parent.parent.parent.parent

# 数据库配置：通过环境变量控制
USE_POSTGRES = os.getenv('USE_POSTGRES', 'false').lower() == 'true'

if USE_POSTGRES:
    # PostgreSQL 生产数据库
    POSTGRES_CONFIG = {
        'host': os.getenv('PG_HOST', '127.0.0.1'),
        'port': os.getenv('PG_PORT', '5432'),
        'database': os.getenv('PG_DATABASE', 'yzr_nr'),
        'user': os.getenv('PG_USER', 'yzr_nr'),
        'password': os.getenv('PG_PASSWORD', 'aTX3WKKnPfRnM5PC')
    }
    SQLALCHEMY_DATABASE_URL = f"postgresql://{POSTGRES_CONFIG['user']}:{POSTGRES_CONFIG['password']}@{POSTGRES_CONFIG['host']}:{POSTGRES_CONFIG['port']}/{POSTGRES_CONFIG['database']}"
    engine = create_engine(SQLALCHEMY_DATABASE_URL, pool_pre_ping=True)
else:
    # SQLite 开发数据库
    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()