import os

from google.auth.transport.requests import Request
from google.oauth2.credentials import Credentials
from google_auth_oauthlib.flow import InstalledAppFlow
from googleapiclient.discovery import build

from app.config import GOOGLE_SCOPES, Settings


def get_google_credentials(settings: Settings) -> Credentials:
    creds = None

    if os.path.exists(settings.google_token_file):
        creds = Credentials.from_authorized_user_file(
            settings.google_token_file, GOOGLE_SCOPES
        )

    if not creds or not creds.valid:
        if creds and creds.expired and creds.refresh_token:
            creds.refresh(Request())
        else:
            if not os.path.exists(settings.google_client_secrets_file):
                raise FileNotFoundError(
                    f"Missing OAuth client file at {settings.google_client_secrets_file}. "
                    "Create Google OAuth desktop credentials and save the JSON at this path."
                )
            flow = InstalledAppFlow.from_client_secrets_file(
                settings.google_client_secrets_file, GOOGLE_SCOPES
            )
            creds = flow.run_local_server(port=0)

        with open(settings.google_token_file, "w", encoding="utf-8") as token_file:
            token_file.write(creds.to_json())

    return creds


def build_gmail_service(settings: Settings):
    creds = get_google_credentials(settings)
    return build("gmail", "v1", credentials=creds, cache_discovery=False)


def build_calendar_service(settings: Settings):
    creds = get_google_credentials(settings)
    return build("calendar", "v3", credentials=creds, cache_discovery=False)