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, and stores UID in session state.
    
    Returns:
        uid (str): The verified User ID.
    
    If token is missing or invalid, stops execution.
    """
    
    # 1. Get token from URL query parameters
    # Note: query_params might return a list if multiple tokens are present, usually not the case.
    # In newer Streamlit versions, st.query_params acts like a dict.
    # We'll use .get() which returns the value string or None.
    print(f"DEBUG: ALL Query Params: {st.query_params}")
    token = st.query_params.get("token")
    print(f"DEBUG: Retrieved Token: {token}")
    
    if not token:
        st.warning("Please login first.")
        
        # Stop execution so the rest of the app doesn't run
        st.stop()
        
    try:
        # 2. Verify the ID token
        decoded_token = auth.verify_id_token(token)
        uid = decoded_token['uid']
        
        # 3. Store UID in session state
        st.session_state["uid"] = uid
        
        return uid
        
    except auth.ExpiredIdTokenError:
        st.error("Session expired. Please login again.")
        st.stop()
        
    except auth.InvalidIdTokenError:
        st.error("Invalid token. Please login again.")
        st.stop()
        
    except Exception as e:
        # Catch other errors (e.g., network issues, malformed token)
        st.error(f"Authentication error: {str(e)}")
        st.stop()