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 googleapiclient.errors import HttpError
from config.settings import settings

class GSheetClient:
    SCOPES = ['https://www.googleapis.com/auth/spreadsheets.readonly']

    def __init__(self):
        self.creds = self._authenticate()

    def _authenticate(self):
        creds = None
        # The file token.json stores the user's access and refresh tokens
        if os.path.exists(settings.TOKEN_FILE):
            creds = Credentials.from_authorized_user_file(settings.TOKEN_FILE, self.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:
                if not os.path.exists(settings.CREDENTIALS_FILE):
                    raise FileNotFoundError(f"Credentials file not found at {settings.CREDENTIALS_FILE}. Please download it from Google Cloud Console.")
                
                flow = InstalledAppFlow.from_client_secrets_file(
                    settings.CREDENTIALS_FILE, self.SCOPES)
                creds = flow.run_local_server(port=0)
            
            # Save the credentials for the next run
            with open(settings.TOKEN_FILE, 'w') as token:
                token.write(creds.to_json())
        
        return creds

    def fetch_data(self):
        try:
            service = build('sheets', 'v4', credentials=self.creds)
            sheet = service.spreadsheets()
            result = sheet.values().get(
                spreadsheetId=settings.SPREADSHEET_ID,
                range=settings.SHEET_RANGE
            ).execute()
            
            return result.get('values', [])
            
        except HttpError as err:
            print(f"An error occurred: {err}")
            return []