import json

import streamlit as st
from google_auth_oauthlib.flow import Flow

SCOPES = [
    # lets us see all the calendars that the user can see
    "https://www.googleapis.com/auth/calendar.readonly",
    # lets us read the details of the events in a calendar
    "https://www.googleapis.com/auth/calendar.events.readonly",
]


@st.cache_resource
def get_flow():
    """Create the oauth flow client"""
    client_creds_str = st.secrets.get("GOOGLE_CLIENT_CREDENTIALS")
    if client_creds_str:
        client_creds = json.loads(client_creds_str)
    else:
        with open("credentials.json", "r") as f:
            client_creds = json.load(f)

    flow = Flow.from_client_config(
        client_creds,
        scopes=SCOPES,
        redirect_uri="urn:ietf:wg:oauth:2.0:oob",
    )
    return flow


def get_auth_url(flow: Flow) -> str:
    """Construct the oauth authorization url for the user to visit to
    authenticate and authorize scopes."""
    auth_url, _ = flow.authorization_url(prompt="consent")
    return auth_url


@st.cache_resource
def get_creds(_flow: Flow, code: str):
    """Get the oauth credentials from the authorization code. Cache it."""
    _flow.fetch_token(code=code)
    creds = _flow.credentials
    st.session_state.creds = creds
    return creds


def load_creds() -> str | None:
    """Load the oauth credentials from the session state."""
    return st.session_state.get("creds", None)