"""os.walk() variation with Google Drive API v3."""

from collections.abc import Iterator, Sequence
import os
import pathlib
from typing import TypedDict

# $ pip install google-api-python-client google-auth-oauthlib
from apiclient import discovery
from google.oauth2 import credentials
from google_auth_oauthlib import flow as flow_lib

SCOPES = ['https://www.googleapis.com/auth/drive.metadata.readonly']

FOLDER = 'application/vnd.google-apps.folder'


def get_credentials(scopes: Sequence[str], *,
                    secrets: os.PathLike[str] | str = '~/client_secrets.json',
                    storage: os.PathLike[str] | str | None = '~/authorized_user.json'
                    ) -> credentials.Credentials:
    creds = None
    if storage is not None:
        storage = pathlib.Path(storage).expanduser()
        if storage.exists():
            creds = credentials.Credentials.from_authorized_user_file(storage, scopes=scopes)

    if creds is None or creds.token_state.name == 'INVALID':
        secrets = pathlib.Path(secrets).expanduser()
        flow = flow_lib.InstalledAppFlow.from_client_secrets_file(secrets, scopes=scopes)
        flow.run_local_server()
        creds = flow.credentials
        if storage is not None:
            authorized_user_info = creds.to_json()
            storage.write_text(authorized_user_info)
    return creds


creds = get_credentials(SCOPES)

service = discovery.build('drive', version='v3', credentials=creds)


def iterfiles(name: str | None = None, *,
              is_folder: bool | None = None,
              parent: str | None = None,
              order_by: str = 'folder,name,createdTime') -> Iterator['File']:
    q = []
    if name is not None:
        q.append("name = '{}'".format(name.replace("'", "\\'")))
    if is_folder is not None:
        q.append("mimeType {} '{}'".format('=' if is_folder else '!=', FOLDER))
    if parent is not None:
        q.append("'{}' in parents".format(parent.replace("'", "\\'")))

    params = {'pageToken': None, 'orderBy': order_by}
    if q:
        params['q'] = ' and '.join(q)

    while True:
        response = service.files().list(**params).execute()
        for f in response['files']:
            yield f
        try:
            params['pageToken'] = response['nextPageToken']
        except KeyError:
            return


class File(TypedDict):
    id: str
    kind: str
    name: str
    mimeType: str
    resourceKey: str


def walk(top: str = 'root', *,
         by_name: bool = False) -> Iterator[tuple[str, list[File], list[File]]]:
    if by_name:
        (top,) = iterfiles(name=top, is_folder=True)
    else:
        top = service.files().get(fileId=top).execute()
        if top['mimeType'] != FOLDER:
            raise ValueError(f'not a folder: {top!r}')

    stack = [((top['name'],), top)]
    while stack:
        (path, top) = stack.pop()

        (dirs, files) = is_file = ([], [])
        for f in iterfiles(parent=top['id']):
            is_file[f['mimeType'] != FOLDER].append(f)

        yield path, top, dirs, files

        if dirs:
            stack.extend((path + (d['name'],), d) for d in reversed(dirs))


for kwargs in [{'top': 'spam', 'by_name': True}, {}]:
    print('', f'walk(**{kwargs!r})', sep='\n')
    for path, root, dirs, files in walk(**kwargs):
        print('/'.join(path), f'{len(dirs):d}', f'{len(files):d}', sep='\t')