from datetime import datetime, timedelta, timezone
from typing import Optional
from fastapi import Depends, HTTPException, status
from fastapi.security import OAuth2PasswordBearer
from jose import JWTError, jwt
from passlib.context import CryptContext
from pydantic import BaseModel
SECRET_KEY = 'change-me-in-production'
ALGORITHM = 'HS256'
ACCESS_TOKEN_EXPIRE_MINUTES = 120
pwd_context = CryptContext(schemes=['bcrypt'], deprecated='auto')
oauth2_scheme = OAuth2PasswordBearer(tokenUrl='/auth/token')
class Token(BaseModel): access_token: str; token_type: str = 'bearer'
class TokenData(BaseModel): username: Optional[str] = None
class User(BaseModel): username: str; disabled: bool = False; role: str = 'viewer'
class UserInDB(User): hashed_password: str
fake_users_db = {'admin': {'username': 'admin', 'hashed_password': pwd_context.hash('admin123'), 'disabled': False, 'role': 'admin'}, 'viewer': {'username': 'viewer', 'hashed_password': pwd_context.hash('viewer123'), 'disabled': False, 'role': 'viewer'}}
def verify_password(plain_password: str, hashed_password: str) -> bool: return pwd_context.verify(plain_password, hashed_password)
def get_user(username: str) -> Optional[UserInDB]:
    user = fake_users_db.get(username)
    return UserInDB(**user) if user else None
def authenticate_user(username: str, password: str) -> Optional[UserInDB]:
    user = get_user(username)
    return user if user and verify_password(password, user.hashed_password) else None
def create_access_token(data: dict, expires_delta: Optional[timedelta] = None) -> str:
    to_encode = data.copy()
    expire = datetime.now(timezone.utc) + (expires_delta or timedelta(minutes=ACCESS_TOKEN_EXPIRE_MINUTES))
    to_encode.update({'exp': expire})
    return jwt.encode(to_encode, SECRET_KEY, algorithm=ALGORITHM)
def get_current_user(token: str = Depends(oauth2_scheme)) -> User:
    credentials_exception = HTTPException(status_code=status.HTTP_401_UNAUTHORIZED, detail='Could not validate credentials', headers={'WWW-Authenticate': 'Bearer'})
    try:
        payload = jwt.decode(token, SECRET_KEY, algorithms=[ALGORITHM])
        username: str = payload.get('sub')
        if username is None: raise credentials_exception
    except JWTError:
        raise credentials_exception
    user = get_user(username)
    if user is None: raise credentials_exception
    return User(username=user.username, disabled=user.disabled, role=user.role)
def get_current_active_user(current_user: User = Depends(get_current_user)) -> User:
    if current_user.disabled: raise HTTPException(status_code=400, detail='Inactive user')
    return current_user