"""
数据库连接和初始化
支持 PostgreSQL（推荐）和 SQLite（本地开发）
"""
import os
from sqlalchemy import create_engine
from sqlalchemy.orm import sessionmaker, Session
from sqlalchemy.ext.asyncio import create_async_engine, AsyncSession, async_sessionmaker

from .models import Base

# 从环境变量获取数据库 URL
raw_database_url = os.getenv("DATABASE_URL", "postgresql://postgres:postgres@localhost:5432/life_echo")


def parse_database_url(url: str) -> tuple[str, str]:
    """
    解析数据库 URL，返回同步和异步版本
    
    支持格式：
    - PostgreSQL: postgresql://user:pass@host:port/db
    - PostgreSQL async: postgresql+asyncpg://user:pass@host:port/db
    - SQLite: sqlite:///./path/to/db.db
    - SQLite async: sqlite+aiosqlite:///./path/to/db.db
    """
    # PostgreSQL
    if url.startswith("postgresql+asyncpg://"):
        async_url = url
        sync_url = url.replace("postgresql+asyncpg://", "postgresql://")
    elif url.startswith("postgresql://"):
        sync_url = url
        async_url = url.replace("postgresql://", "postgresql+asyncpg://")
    # SQLite
    elif url.startswith("sqlite+aiosqlite://"):
        async_url = url
        sync_url = url.replace("sqlite+aiosqlite://", "sqlite://")
    elif url.startswith("sqlite://"):
        sync_url = url
        async_url = url.replace("sqlite://", "sqlite+aiosqlite://")
    else:
        # 默认使用 PostgreSQL
        print(f"警告: DATABASE_URL 格式不正确 ({url})，使用默认 PostgreSQL")
        sync_url = "postgresql://postgres:postgres@localhost:5432/life_echo"
        async_url = "postgresql+asyncpg://postgres:postgres@localhost:5432/life_echo"
    
    return sync_url, async_url


DATABASE_URL, ASYNC_DATABASE_URL = parse_database_url(raw_database_url)

# 创建同步引擎（用于迁移、Celery 任务等）
# SQLite 需要特殊的 connect_args
if DATABASE_URL.startswith("sqlite"):
    engine = create_engine(DATABASE_URL, connect_args={"check_same_thread": False})
else:
    # 使用 psycopg (v3) 驱动
    sync_url = DATABASE_URL.replace("postgresql://", "postgresql+psycopg://")
    engine = create_engine(sync_url, pool_size=5, max_overflow=10)

# 创建异步引擎（用于 FastAPI）
if ASYNC_DATABASE_URL.startswith("sqlite"):
    async_engine = create_async_engine(ASYNC_DATABASE_URL, echo=False)
else:
    async_engine = create_async_engine(
        ASYNC_DATABASE_URL, 
        echo=False,
        pool_size=5,
        max_overflow=10
    )

# 创建会话工厂
SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
AsyncSessionLocal = async_sessionmaker(async_engine, class_=AsyncSession, expire_on_commit=False)


def init_db():
    """初始化数据库，创建所有表"""
    Base.metadata.create_all(bind=engine)


def get_db():
    """获取同步数据库会话（用于迁移等）"""
    db = SessionLocal()
    try:
        yield db
    finally:
        db.close()


async def get_async_db():
    """获取异步数据库会话（用于实际应用）"""
    async with AsyncSessionLocal() as session:
        try:
            yield session
            await session.commit()
        except Exception:
            await session.rollback()
            raise
        finally:
            await session.close()