from google.oauth2.credentials import Credentials
from google_auth_oauthlib.flow import Flow
from googleapiclient.discovery import build
from googleapiclient.http import MediaFileUpload, MediaIoBaseDownload
import os
import json

# This file should be downloaded from Google Cloud Console
CLIENT_SECRETS_FILE = "credentials.json"
SCOPES = ["https://www.googleapis.com/auth/drive.file"]

def get_drive_service(credentials_info=None):
    if isinstance(credentials_info, str):
        credentials_info = json.loads(credentials_info)

    creds = None
    if credentials_info:
        creds = Credentials.from_authorized_user_info(credentials_info, SCOPES)

    if not creds or not creds.valid:
        # This should not happen in a web flow if the user is authenticated.
        # If it does, it means the credentials have expired or are invalid,
        # and the user needs to re-authenticate.
        # The API should handle this by returning a 401 Unauthorized error.
        return None

    return build('drive', 'v3', credentials=creds)

def upload_file(drive_service, file_path, folder_id=None):
    file_metadata = {
        'name': os.path.basename(file_path)
    }
    if folder_id:
        file_metadata['parents'] = [folder_id]

    media = MediaFileUpload(file_path, resumable=True)
    file = drive_service.files().create(
        body=file_metadata,
        media_body=media,
        fields='id'
    ).execute()
    
    return file.get('id')

def download_file(drive_service, file_id, destination):
    request = drive_service.files().get_media(fileId=file_id)
    with open(destination, "wb") as fh:
        downloader = MediaIoBaseDownload(fh, request)
        done = False
        while done is False:
            status, done = downloader.next_chunk()
            print(f"Download {int(status.progress() * 100)}%.")

def authenticate(redirect_uri):
    flow = Flow.from_client_secrets_file(
        CLIENT_SECRETS_FILE, SCOPES, redirect_uri=redirect_uri
    )
    authorization_url, state = flow.authorization_url(
        access_type='offline', include_granted_scopes='true'
    )
    # Store state in session or a temporary store to verify in the callback
    # For now, we'll just return it. A real app should handle this securely.
    return authorization_url, state

def exchange_code_for_credentials(code, redirect_uri, state):
    flow = Flow.from_client_secrets_file(
        CLIENT_SECRETS_FILE, SCOPES, redirect_uri=redirect_uri
    )
    # The state parameter should be verified against the value from the auth request
    flow.fetch_token(code=code)
    credentials = flow.credentials
    return credentials