from datetime import datetime
import os.path
from base64 import b16encode

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, Resource
from googleapiclient.errors import HttpError

# If modifying these scopes, delete the file token.json.
SCOPES = [
    "https://www.googleapis.com/auth/calendar.readonly",
    "https://www.googleapis.com/auth/calendar.events",
]


class CalendarService:
    service: Resource

    def __init__(self):
        creds = self._authenticate()
        self.service = build("calendar", "v3", credentials=creds)

    @staticmethod
    def encode_event_id(id):
        return b16encode(id.encode("ascii")).decode("ascii").lower().rstrip("=")

    def _authenticate(self) -> Credentials:
        creds = None
        # The file token.json stores the user's access and refresh tokens, and is
        # created automatically when the authorization flow completes for the first
        # time.
        if os.path.exists("token.json"):
            creds = Credentials.from_authorized_user_file("token.json", SCOPES)
        # If there are no (valid) credentials available, let the user log in.
        if not creds or not creds.valid:
            if creds and creds.expired and creds.refresh_token:
                creds.refresh(Request())
            else:
                flow = InstalledAppFlow.from_client_secrets_file(
                    "credentials.json", SCOPES
                )
                creds = flow.run_local_server(port=0)
            # Save the credentials for the next run
            with open("token.json", "w") as token:
                token.write(creds.to_json())

        return creds

    def insert_or_update_event(
        self, calendar_id: str, id: str, title: str, start: datetime, end: datetime
    ):
        event_id = self.encode_event_id(id)
        event = {
            "id": event_id,
            "summary": title,
            "start": {
                "dateTime": start.isoformat() + "Z",  # 'Z' indicates UTC time
            },
            "end": {
                "dateTime": end.isoformat() + "Z",  # 'Z' indicates UTC time
            },
        }

        print(f"Adding/updating event: {title}, start: {start}, end: {end}")

        try:
            self.service.events().update(
                calendarId=calendar_id, eventId=event_id, body=event
            ).execute()

        except HttpError as error:
            # Create event if it doesn't exist
            if error.status_code == 404:
                self.service.events().insert(
                    calendarId=calendar_id, body=event
                ).execute()

            else:
                raise

    def delete_event(self, calendar_id: str, id: str):
        event_id = self.encode_event_id(id)
        try:
            self.service.events().delete(calendar_id, event_id)
        except HttpError as error:
            print("Got error when deleting event: ", error)