auth.py

import streamlit as st
from firebase_admin import auth

def verify_user_from_query():
    """
    Retrieves Firebase ID token from URL parameter 'token',
    verifies it with Firebase Admin SDK.
    
    Returns:
        uid (str): The verified User ID.
    
    Raises:
        ValueError: If token is missing.
        auth.ExpiredIdTokenError: If token is expired.
        auth.InvalidIdTokenError: If token is invalid.
        Exception: For other errors.
    """
    
    token = st.query_params.get("token")
    
    if not token:
        raise ValueError("No token found in query parameters.")
        
    try:
        # Verify the ID token
        decoded_token = auth.verify_id_token(token)
        uid = decoded_token['uid']
        return uid
        
    except auth.ExpiredIdTokenError:
        raise
        
    except auth.InvalidIdTokenError:
        raise
        
    except Exception as e:
        raise e