import jwt
from datetime import datetime, timedelta
from typing import AsyncGenerator, Optional
from fastapi import Depends, HTTPException, Header, status
from sqlalchemy.ext.asyncio import create_async_engine, AsyncSession, async_sessionmaker
from app.config import settings

# Database Engine & Session
engine = create_async_engine(
    settings.DATABASE_URL,
    echo=settings.DEBUG,
    future=True,
    pool_pre_ping=True
)

AsyncSessionLocal = async_sessionmaker(
    bind=engine,
    class_=AsyncSession,
    expire_on_commit=False,
    autocommit=False,
    autoflush=False,
)

async def get_db_session() -> AsyncGenerator[AsyncSession, None]:
    async with AsyncSessionLocal() as session:
        try:
            yield session
            await session.commit()
        except Exception:
            await session.rollback()
            raise

def create_access_token(address: str) -> str:
    expire = datetime.utcnow() + timedelta(minutes=settings.ACCESS_TOKEN_EXPIRE_MINUTES)
    payload = {"sub": address.lower(), "exp": expire}
    return jwt.encode(payload, settings.JWT_SECRET, algorithm=settings.JWT_ALGORITHM)

async def get_current_user(authorization: Optional[str] = Header(None)) -> str:
    if not authorization or not authorization.startswith("Bearer "):
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="缺少有效的认证 Token",
            headers={"WWW-Authenticate": "Bearer"},
        )
    token = authorization.split(" ")[1]
    try:
        payload = jwt.decode(token, settings.JWT_SECRET, algorithms=[settings.JWT_ALGORITHM])
        address = payload.get("sub")
        if not address:
            raise HTTPException(status_code=status.HTTP_401_UNAUTHORIZED, detail="无效的用户凭证")
        return address
    except jwt.PyJWTError:
        raise HTTPException(status_code=status.HTTP_401_UNAUTHORIZED, detail="Token 已过期或无效")