__init__.py

import logging
import shutil
import time

from tufup.client import Client

from myapp import settings

logger = logging.getLogger(__name__)

__version__ = settings.APP_VERSION


def progress_hook(bytes_downloaded: int, bytes_expected: int):
    progress_percent = bytes_downloaded / bytes_expected * 100
    print(f'\r{progress_percent:.1f}%', end='')
    time.sleep(0.2)  # quick and dirty: simulate slow or large download
    if progress_percent >= 100:
        print('')


def update(pre: str):
    # Create update client
    client = Client(
        app_name=settings.APP_NAME,
        app_install_dir=settings.INSTALL_DIR,
        current_version=settings.APP_VERSION,
        metadata_dir=settings.METADATA_DIR,
        metadata_base_url=settings.METADATA_BASE_URL,
        target_dir=settings.TARGET_DIR,
        target_base_url=settings.TARGET_BASE_URL,
        refresh_required=False,
    )

    # Perform update
    if client.check_for_updates(pre=pre):
        client.download_and_apply_update(
            # WARNING: Be very careful with purge_dst_dir=True, because this
            # will delete *EVERYTHING* inside the app_install_dir, except
            # paths specified in exclude_from_purge. So, only use
            # purge_dst_dir=True if you are certain that your app_install_dir
            # does not contain any unrelated content.
            progress_hook=progress_hook,
            purge_dst_dir=False,
            exclude_from_purge=None,
            log_file_name='install.log',
        )


def main(cmd_args):
    # extract options from command line args
    pre_release_channel = cmd_args[0] if cmd_args else None  # 'a', 'b', or 'rc'

    # The app must ensure dirs exist
    for dir_path in [settings.INSTALL_DIR, settings.METADATA_DIR, settings.TARGET_DIR]:
        dir_path.mkdir(exist_ok=True, parents=True)

    # The app must be shipped with a trusted "root.json" metadata file,
    # which is created using the tufup.repo tools. The app must ensure
    # this file can be found in the specified metadata_dir. The root metadata
    # file lists all trusted keys and TUF roles.
    if not settings.TRUSTED_ROOT_DST.exists():
        shutil.copy(src=settings.TRUSTED_ROOT_SRC, dst=settings.TRUSTED_ROOT_DST)
        logger.info('Trusted root metadata copied to cache.')

    # Download and apply any available updates
    update(pre=pre_release_channel)

    # Do what the app is supposed to do
    print(f'Starting {settings.APP_NAME} {settings.APP_VERSION}...')
    ...
    print('Doing what the app is supposed to do...')
    ...
    print('Done.')