text: # Used by pkgs/misc/vim-plugins/update.py and pkgs/applications/editors/kakoune/plugins/update.py
  
  # format:
  # $ nix run nixpkgs.python3Packages.black -c black update.py
  # type-check:
  # $ nix run nixpkgs.python3Packages.mypy -c mypy update.py
  # linted:
  # $ nix run nixpkgs.python3Packages.flake8 -c flake8 --ignore E501,E265 update.py
  
  import argparse
  import functools
  import http
  import json
  import os
  import subprocess
  import logging
  import sys
  import time
  import traceback
  import urllib.error
  import urllib.parse
  import urllib.request
  import xml.etree.ElementTree as ET
  from datetime import datetime
  from functools import wraps
  from multiprocessing.dummy import Pool
  from pathlib import Path
  from typing import Dict, List, Optional, Tuple, Union, Any, Callable
  from urllib.parse import urljoin, urlparse
  from tempfile import NamedTemporaryFile
  from dataclasses import dataclass
  
  import git
  
  ATOM_ENTRY = "{http://www.w3.org/2005/Atom}entry"  # " vim gets confused here
  ATOM_LINK = "{http://www.w3.org/2005/Atom}link"  # "
  ATOM_UPDATED = "{http://www.w3.org/2005/Atom}updated"  # "
  
  LOG_LEVELS = {
      logging.getLevelName(level): level for level in [
          logging.DEBUG, logging.INFO, logging.WARN, logging.ERROR ]
  }
  
  log = logging.getLogger()
  
  def retry(ExceptionToCheck: Any, tries: int = 4, delay: float = 3, backoff: float = 2):
      """Retry calling the decorated function using an exponential backoff.
      http://www.saltycrane.com/blog/2009/11/trying-out-retry-decorator-python/
      original from: http://wiki.python.org/moin/PythonDecoratorLibrary#Retry
      (BSD licensed)
      :param ExceptionToCheck: the exception on which to retry
      :param tries: number of times to try (not retry) before giving up
      :param delay: initial delay between retries in seconds
      :param backoff: backoff multiplier e.g. value of 2 will double the delay
          each retry
      """
  
      def deco_retry(f: Callable) -> Callable:
          @wraps(f)
          def f_retry(*args: Any, **kwargs: Any) -> Any:
              mtries, mdelay = tries, delay
              while mtries > 1:
                  try:
                      return f(*args, **kwargs)
                  except ExceptionToCheck as e:
                      print(f"{str(e)}, Retrying in {mdelay} seconds...")
                      time.sleep(mdelay)
                      mtries -= 1
                      mdelay *= backoff
              return f(*args, **kwargs)
  
          return f_retry  # true decorator
  
      return deco_retry
  
  
  def make_request(url: str) -> urllib.request.Request:
      token = os.getenv("GITHUB_API_TOKEN")
      headers = {}
      if token is not None:
          headers["Authorization"] = f"token {token}"
      return urllib.request.Request(url, headers=headers)
  
  @dataclass
  class PluginDesc:
      owner: str
      repo: str
      branch: str
      alias: Optional[str]
  
  
  class Repo:
      def __init__(
          self, owner: str, name: str, branch: str, alias: Optional[str]
      ) -> None:
          self.owner = owner
          self.name = name
          self.branch = branch
          self.alias = alias
          self.redirect: Dict[str, str] = {}
  
      def url(self, path: str) -> str:
          return urljoin(f"https://github.com/{self.owner}/{self.name}/", path)
  
      def __repr__(self) -> str:
          return f"Repo({self.owner}, {self.name})"
  
      @retry(urllib.error.URLError, tries=4, delay=3, backoff=2)
      def has_submodules(self) -> bool:
          try:
              req = make_request(self.url(f"blob/{self.branch}/.gitmodules"))
              urllib.request.urlopen(req, timeout=10).close()
          except urllib.error.HTTPError as e:
              if e.code == 404:
                  return False
              else:
                  raise
          return True
  
      @retry(urllib.error.URLError, tries=4, delay=3, backoff=2)
      def latest_commit(self) -> Tuple[str, datetime]:
          commit_url = self.url(f"commits/{self.branch}.atom")
          commit_req = make_request(commit_url)
          with urllib.request.urlopen(commit_req, timeout=10) as req:
              self.check_for_redirect(commit_url, req)
              xml = req.read()
              root = ET.fromstring(xml)
              latest_entry = root.find(ATOM_ENTRY)
              assert latest_entry is not None, f"No commits found in repository {self}"
              commit_link = latest_entry.find(ATOM_LINK)
              assert commit_link is not None, f"No link tag found feed entry {xml}"
              url = urlparse(commit_link.get("href"))
              updated_tag = latest_entry.find(ATOM_UPDATED)
              assert (
                  updated_tag is not None and updated_tag.text is not None
              ), f"No updated tag found feed entry {xml}"
              updated = datetime.strptime(updated_tag.text, "%Y-%m-%dT%H:%M:%SZ")
              return Path(str(url.path)).name, updated
  
      def check_for_redirect(self, url: str, req: http.client.HTTPResponse):
          response_url = req.geturl()
          if url != response_url:
              new_owner, new_name = (
                  urllib.parse.urlsplit(response_url).path.strip("/").split("/")[:2]
              )
              end_line = "\n" if self.alias is None else f" as {self.alias}\n"
              plugin_line = "{owner}/{name}" + end_line
  
              old_plugin = plugin_line.format(owner=self.owner, name=self.name)
              new_plugin = plugin_line.format(owner=new_owner, name=new_name)
              self.redirect[old_plugin] = new_plugin
  
      def prefetch_git(self, ref: str) -> str:
          data = subprocess.check_output(
              ["nix-prefetch-git", "--fetch-submodules", self.url(""), ref]
          )
          return json.loads(data)["sha256"]
  
      def prefetch_github(self, ref: str) -> str:
          data = subprocess.check_output(
              ["nix-prefetch-url", "--unpack", self.url(f"archive/{ref}.tar.gz")]
          )
          return data.strip().decode("utf-8")
  
  
  class Plugin:
      def __init__(
          self,
          name: str,
          commit: str,
          has_submodules: bool,
          sha256: str,
          date: Optional[datetime] = None,
      ) -> None:
          self.name = name
          self.commit = commit
          self.has_submodules = has_submodules
          self.sha256 = sha256
          self.date = date
  
      @property
      def normalized_name(self) -> str:
          return self.name.replace(".", "-")
  
      @property
      def version(self) -> str:
          assert self.date is not None
          return self.date.strftime("%Y-%m-%d")
  
      def as_json(self) -> Dict[str, str]:
          copy = self.__dict__.copy()
          del copy["date"]
          return copy
  
  
  class Editor:
      """The configuration of the update script."""
  
      def __init__(
          self,
          name: str,
          root: Path,
          get_plugins: str,
          default_in: Optional[Path] = None,
          default_out: Optional[Path] = None,
          deprecated: Optional[Path] = None,
          cache_file: Optional[str] = None,
      ):
          log.debug("get_plugins:", get_plugins)
          self.name = name
          self.root = root
          self.get_plugins = get_plugins
          self.default_in = default_in or root.joinpath(f"{name}-plugin-names")
          self.default_out = default_out or root.joinpath("generated.nix")
          self.deprecated = deprecated or root.joinpath("deprecated.json")
          self.cache_file = cache_file or f"{name}-plugin-cache.json"
  
      def get_current_plugins(self):
          """To fill the cache"""
          return get_current_plugins(self)
  
      def load_plugin_spec(self, plugin_file) -> List[PluginDesc]:
          return load_plugin_spec(plugin_file)
  
      def generate_nix(self, plugins, outfile: str):
          '''Returns nothing for now, writes directly to outfile'''
          raise NotImplementedError()
  
      def get_update(self, input_file: str, outfile: str, proc: int):
          return get_update(input_file, outfile, proc, editor=self)
  
      @property
      def attr_path(self):
          return self.name + "Plugins"
  
      def get_drv_name(self, name: str):
          return self.attr_path + "." + name
  
      def rewrite_input(self, *args, **kwargs):
          return rewrite_input(*args, **kwargs)
  
      def create_parser(self):
          parser = argparse.ArgumentParser(
              description=(
                  f"Updates nix derivations for {self.name} plugins"
                  f"By default from {self.default_in} to {self.default_out}"
              )
          )
          parser.add_argument(
              "--add",
              dest="add_plugins",
              default=[],
              action="append",
              help=f"Plugin to add to {self.attr_path} from Github in the form owner/repo",
          )
          parser.add_argument(
              "--input-names",
              "-i",
              dest="input_file",
              default=self.default_in,
              help="A list of plugins in the form owner/repo",
          )
          parser.add_argument(
              "--out",
              "-o",
              dest="outfile",
              default=self.default_out,
              help="Filename to save generated nix code",
          )
          parser.add_argument(
              "--proc",
              "-p",
              dest="proc",
              type=int,
              default=30,
              help="Number of concurrent processes to spawn.",
          )
          parser.add_argument(
              "--no-commit", "-n", action="store_true", default=False,
              help="Whether to autocommit changes"
          )
          parser.add_argument(
              "--debug", "-d", choices=LOG_LEVELS.keys(),
              default=logging.getLevelName(logging.WARN),
              help="Adjust log level"
          )
          return parser
  
  
  
  class CleanEnvironment(object):
      def __enter__(self) -> None:
          self.old_environ = os.environ.copy()
          local_pkgs = str(Path(__file__).parent.parent.parent)
          os.environ["NIX_PATH"] = f"localpkgs={local_pkgs}"
          self.empty_config = NamedTemporaryFile()
          self.empty_config.write(b"{}")
          self.empty_config.flush()
          os.environ["NIXPKGS_CONFIG"] = self.empty_config.name
  
      def __exit__(self, exc_type: Any, exc_value: Any, traceback: Any) -> None:
          os.environ.update(self.old_environ)
          self.empty_config.close()
  
  
  def get_current_plugins(editor: Editor) -> List[Plugin]:
      with CleanEnvironment():
          cmd = ["nix", "eval", "--impure", "--json", "--expr", editor.get_plugins]
          log.debug("Running command %s", cmd)
          out = subprocess.check_output(cmd)
      data = json.loads(out)
      plugins = []
      for name, attr in data.items():
          p = Plugin(name, attr["rev"], attr["submodules"], attr["sha256"])
          plugins.append(p)
      return plugins
  
  
  def prefetch_plugin(
      p: PluginDesc,
      cache: "Optional[Cache]" = None,
  ) -> Tuple[Plugin, Dict[str, str]]:
      user, repo_name, branch, alias = p.owner, p.repo, p.branch, p.alias
      log.info(f"Fetching last commit for plugin {user}/{repo_name}@{branch}")
      repo = Repo(user, repo_name, branch, alias)
      commit, date = repo.latest_commit()
      has_submodules = repo.has_submodules()
      cached_plugin = cache[commit] if cache else None
      if cached_plugin is not None:
          log.debug("Cache hit !")
          cached_plugin.name = alias or repo_name
          cached_plugin.date = date
          return cached_plugin, repo.redirect
  
      print(f"prefetch {user}/{repo_name}")
      if has_submodules:
          sha256 = repo.prefetch_git(commit)
      else:
          sha256 = repo.prefetch_github(commit)
  
      return (
          Plugin(alias or repo_name, commit, has_submodules, sha256, date=date),
          repo.redirect,
      )
  
  
  def fetch_plugin_from_pluginline(plugin_line: str) -> Plugin:
      plugin, _ = prefetch_plugin(parse_plugin_line(plugin_line))
      return plugin
  
  
  def print_download_error(plugin: str, ex: Exception):
      print(f"{plugin}: {ex}", file=sys.stderr)
      ex_traceback = ex.__traceback__
      tb_lines = [
          line.rstrip("\n")
          for line in traceback.format_exception(ex.__class__, ex, ex_traceback)
      ]
      print("\n".join(tb_lines))
  
  
  def check_results(
      results: List[Tuple[str, str, Union[Exception, Plugin], Dict[str, str]]]
  ) -> Tuple[List[Tuple[str, str, Plugin]], Dict[str, str]]:
      failures: List[Tuple[str, Exception]] = []
      plugins = []
      redirects: Dict[str, str] = {}
      for (owner, name, result, redirect) in results:
          if isinstance(result, Exception):
              failures.append((name, result))
          else:
              plugins.append((owner, name, result))
              redirects.update(redirect)
  
      print(f"{len(results) - len(failures)} plugins were checked", end="")
      if len(failures) == 0:
          print()
          return plugins, redirects
      else:
          print(f", {len(failures)} plugin(s) could not be downloaded:\n")
  
          for (plugin, exception) in failures:
              print_download_error(plugin, exception)
  
          sys.exit(1)
  
  def parse_plugin_line(line: str) -> PluginDesc:
      branch = "master"
      alias = None
      name, repo = line.split("/")
      if " as " in repo:
          repo, alias = repo.split(" as ")
          alias = alias.strip()
      if "@" in repo:
          repo, branch = repo.split("@")
  
      return PluginDesc(name.strip(), repo.strip(), branch.strip(), alias)
  
  
  def load_plugin_spec(plugin_file: str) -> List[PluginDesc]:
      plugins = []
      with open(plugin_file) as f:
          for line in f:
              plugin = parse_plugin_line(line)
              if not plugin.owner:
                  msg = f"Invalid repository {line}, must be in the format owner/repo[ as alias]"
                  print(msg, file=sys.stderr)
                  sys.exit(1)
              plugins.append(plugin)
      return plugins
  
  
  def get_cache_path(cache_file_name: str) -> Optional[Path]:
      xdg_cache = os.environ.get("XDG_CACHE_HOME", None)
      if xdg_cache is None:
          home = os.environ.get("HOME", None)
          if home is None:
              return None
          xdg_cache = str(Path(home, ".cache"))
  
      return Path(xdg_cache, cache_file_name)
  
  
  class Cache:
      def __init__(self, initial_plugins: List[Plugin], cache_file_name: str) -> None:
          self.cache_file = get_cache_path(cache_file_name)
  
          downloads = {}
          for plugin in initial_plugins:
              downloads[plugin.commit] = plugin
          downloads.update(self.load())
          self.downloads = downloads
  
      def load(self) -> Dict[str, Plugin]:
          if self.cache_file is None or not self.cache_file.exists():
              return {}
  
          downloads: Dict[str, Plugin] = {}
          with open(self.cache_file) as f:
              data = json.load(f)
              for attr in data.values():
                  p = Plugin(
                      attr["name"], attr["commit"], attr["has_submodules"], attr["sha256"]
                  )
                  downloads[attr["commit"]] = p
          return downloads
  
      def store(self) -> None:
          if self.cache_file is None:
              return
  
          os.makedirs(self.cache_file.parent, exist_ok=True)
          with open(self.cache_file, "w+") as f:
              data = {}
              for name, attr in self.downloads.items():
                  data[name] = attr.as_json()
              json.dump(data, f, indent=4, sort_keys=True)
  
      def __getitem__(self, key: str) -> Optional[Plugin]:
          return self.downloads.get(key, None)
  
      def __setitem__(self, key: str, value: Plugin) -> None:
          self.downloads[key] = value
  
  
  def prefetch(
      pluginDesc: PluginDesc, cache: Cache
  ) -> Tuple[str, str, Union[Exception, Plugin], dict]:
      owner, repo = pluginDesc.owner, pluginDesc.repo
      try:
          plugin, redirect = prefetch_plugin(pluginDesc, cache)
          cache[plugin.commit] = plugin
          return (owner, repo, plugin, redirect)
      except Exception as e:
          return (owner, repo, e, {})
  
  
  def rewrite_input(
      input_file: Path,
      deprecated: Path,
      redirects: Dict[str, str] = None,
      append: Tuple = (),
  ):
      with open(input_file, "r") as f:
          lines = f.readlines()
  
      lines.extend(append)
  
      if redirects:
          lines = [redirects.get(line, line) for line in lines]
  
          cur_date_iso = datetime.now().strftime("%Y-%m-%d")
          with open(deprecated, "r") as f:
              deprecations = json.load(f)
          for old, new in redirects.items():
              old_plugin = fetch_plugin_from_pluginline(old)
              new_plugin = fetch_plugin_from_pluginline(new)
              if old_plugin.normalized_name != new_plugin.normalized_name:
                  deprecations[old_plugin.normalized_name] = {
                      "new": new_plugin.normalized_name,
                      "date": cur_date_iso,
                  }
          with open(deprecated, "w") as f:
              json.dump(deprecations, f, indent=4, sort_keys=True)
              f.write("\n")
  
      lines = sorted(lines, key=str.casefold)
  
      with open(input_file, "w") as f:
          f.writelines(lines)
  
  
  def commit(repo: git.Repo, message: str, files: List[Path]) -> None:
      repo.index.add([str(f.resolve()) for f in files])
  
      if repo.index.diff("HEAD"):
          print(f'committing to nixpkgs "{message}"')
          repo.index.commit(message)
      else:
          print("no changes in working tree to commit")
  
  
  def get_update(input_file: str, outfile: str, proc: int, editor: Editor):
      cache: Cache = Cache(editor.get_current_plugins(), editor.cache_file)
      _prefetch = functools.partial(prefetch, cache=cache)
  
      def update() -> dict:
          plugin_names = editor.load_plugin_spec(input_file)
  
          try:
              pool = Pool(processes=proc)
              results = pool.map(_prefetch, plugin_names)
          finally:
              cache.store()
  
          plugins, redirects = check_results(results)
  
          editor.generate_nix(plugins, outfile)
  
          return redirects
  
      return update
  
  
  def update_plugins(editor: Editor, args):
      """The main entry function of this module. All input arguments are grouped in the `Editor`."""
  
      log.setLevel(LOG_LEVELS[args.debug])
      log.info("Start updating plugins")
      update = editor.get_update(args.input_file, args.outfile, args.proc)
  
      redirects = update()
      editor.rewrite_input(args.input_file, editor.deprecated, redirects)
  
      autocommit = not args.no_commit
  
      if autocommit:
          nixpkgs_repo = git.Repo(editor.root, search_parent_directories=True)
          commit(nixpkgs_repo, f"{editor.attr_path}: update", [args.outfile])
  
      if redirects:
          update()
          if autocommit:
              commit(
                  nixpkgs_repo,
                  f"{editor.attr_path}: resolve github repository redirects",
                  [args.outfile, args.input_file, editor.deprecated],
              )
  
      for plugin_line in args.add_plugins:
          editor.rewrite_input(args.input_file, editor.deprecated, append=(plugin_line + "\n",))
          update()
          plugin = fetch_plugin_from_pluginline(plugin_line)
          if autocommit:
              commit(
                  nixpkgs_repo,
                  "{drv_name}: init at {version}".format(
                      drv_name=editor.get_drv_name(plugin.normalized_name),
                      version=plugin.version
                  ),
                  [args.outfile, args.input_file],
              )
  