updater.py

#!/usr/bin/env python3
"""
Usage:
    updater.py check <repo> <path>
    updater.py update <repo> <path>
"""
import os
import sys
import tarfile
from distutils.version import StrictVersion
from pathlib import Path
from shutil import rmtree

import requests
from docopt import docopt

ASSET_ID_FILE = ".asset_id"
CURRENT_PATH = "current"
HISTORY_COUNT = 5
RELEASES_PATH = "releases"
RELEASE_PREFIX = "website-v"

RELEASE_URL = "https://api.github.com/repos/{repo}/releases"


def _release_filter(release):
    return not release["draft"] and not release["prerelease"] and release["assets"]


def get_latest_release_asset(repo):
    with requests.get(RELEASE_URL.format(repo=repo)) as response:
        response.raise_for_status()
        data = response.json()

    release = next(filter(_release_filter, data), None)

    if release is None:
        raise ValueError("Unable to find matching release")

    return release["assets"][0]


def check_for_update(args):
    repo = args["<repo>"]
    deploy_path = Path(args["<path>"]).resolve()
    if not deploy_path.is_dir():
        sys.exit("Website not deployed")

    asset_id_file = deploy_path / CURRENT_PATH / ASSET_ID_FILE
    if not asset_id_file.exists():
        sys.exit("No assets currently deployed")

    with open(str(asset_id_file)) as f:
        current_id = f.read().strip().splitlines()[0]

    if not current_id:
        sys.exit("No assets currently deployed")

    asset = get_latest_release_asset(repo)
    if str(asset["id"]) != current_id:
        sys.exit("Assets out of date")

    sys.exit(0)


def do_update(args):
    deploy_path = Path(args["<path>"]).resolve()
    releases_dir = deploy_path / RELEASES_PATH
    current_link = deploy_path / CURRENT_PATH

    asset = get_latest_release_asset(args["<repo>"])

    # Requires that the asset be '<name>.tar.gz'
    release_name = asset["name"].rsplit(".", 2)[0]

    release_dir = releases_dir / release_name
    if not release_dir.exists():
        release_dir.mkdir(parents=True)

    with requests.get(
        asset["url"], stream=True, headers={"Accept": "application/octet-stream",}
    ) as response:
        with tarfile.open(fileobj=response.raw, mode="r|*") as tarball:
            tarball.extractall(path=str(release_dir))

    # Record the ID of this asset for later update checks
    with open(str(release_dir / ASSET_ID_FILE), "w") as f:
        print(asset["id"], file=f)

    if current_link.is_symlink():
        current_link.unlink()

    current_link.symlink_to(release_dir, target_is_directory=True)
    print("Deployed", release_name)

    do_cleanup(releases_dir, release_name)


def do_cleanup(releases_dir, latest_release):
    directories = os.listdir(releases_dir)

    if len(directories) <= HISTORY_COUNT:
        print("Did not run clean up (too few historic releases)")
        return

    def key(d):
        return StrictVersion(d.replace(RELEASE_PREFIX, ""))

    directories.sort(key=key, reverse=True)

    to_remove = directories[HISTORY_COUNT:]
    for directory in to_remove:
        rmtree(releases_dir / directory)

    if to_remove:
        print(f"Cleaned up {len(to_remove)} historic releases")
    else:
        print("No clean up required")


def main():
    args = docopt(__doc__)

    if args["check"]:
        check_for_update(args)
    elif args["update"]:
        do_update(args)
    else:
        raise ValueError("Invalid arguments from docopt")


if __name__ == "__main__":
    main()