import os
import datetime
import pickle
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

# If modifying these scopes, delete the file token.pickle.
SCOPES = ['https://www.googleapis.com/auth/calendar']

def get_calendar_service():
    creds = None
    # The file token.pickle stores the user's access and refresh tokens, and is
    # created automatically when the authorization flow completes for the first
    # time.
    base_dir = os.path.dirname(os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
    token_path = os.path.join(base_dir, 'token.pickle')
    credentials_path = os.path.join(base_dir, 'credentials.json')

    if os.path.exists(token_path):
        with open(token_path, 'rb') as token:
            creds = pickle.load(token)
            
    # 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:
            if not os.path.exists(credentials_path):
                print(f"[ERROR] credentials.json not found at {credentials_path}")
                return None
                
            flow = InstalledAppFlow.from_client_secrets_file(
                credentials_path, SCOPES)
            creds = flow.run_local_server(port=0)
            
        # Save the credentials for the next run
        with open(token_path, 'wb') as token:
            pickle.dump(creds, token)

    service = build('calendar', 'v3', credentials=creds)
    return service

def create_event(summary, description, start_time_str, location=None):
    """
    Creates a Google Calendar event.
    start_time_str: "YYYY-MM-DDTHH:MM:SS" (frontend send format)
    """
    try:
        service = get_calendar_service()
        if not service:
            return None

        # Parse start time (Assume generic ISO format)
        # Frontend sends: "2024-05-20T14:30"
        start_dt = datetime.datetime.fromisoformat(start_time_str)
        end_dt = start_dt + datetime.timedelta(hours=1) # Default 1 hour duration

        event = {
            'summary': summary,
            'location': location,
            'description': description,
            'start': {
                'dateTime': start_dt.isoformat(),
                'timeZone': 'Asia/Tokyo', # Adjust as needed
            },
            'end': {
                'dateTime': end_dt.isoformat(),
                'timeZone': 'Asia/Tokyo',
            },
            'reminders': {
                'useDefault': False,
                'overrides': [
                    {'method': 'email', 'minutes': 24 * 60},
                    {'method': 'popup', 'minutes': 10},
                ],
            },
        }

        event = service.events().insert(calendarId='primary', body=event).execute()
        print(f'Event created: {event.get("htmlLink")}')
        return event.get("htmlLink")

    except Exception as e:
        print(f"An error occurred: {e}")
        return None