# Used by pkgs/applications/editors/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

@dataclass
class FetchConfig:
    proc: int
    github_token: str


def make_request(url: str, token=None) -> urllib.request.Request:
    headers = {}
    if token is not None:
        headers["Authorization"] = f"token {token}"
    return urllib.request.Request(url, headers=headers)

class Repo:
    def __init__(
        self, uri: str, branch: str, alias: Optional[str]
    ) -> None:
        self.uri = uri
        '''Url to the repo'''
        self.branch = branch
        self.alias = alias
        self.redirect: Dict[str, str] = {}
        self.token = "dummy_token"

    @property
    def name(self):
        return self.uri.split('/')[-1]

    def __repr__(self) -> str:
        return f"Repo({self.name}, {self.uri})"

    @retry(urllib.error.URLError, tries=4, delay=3, backoff=2)
    def has_submodules(self) -> bool:
        return True

    @retry(urllib.error.URLError, tries=4, delay=3, backoff=2)
    def latest_commit(self) -> Tuple[str, datetime]:
        loaded = self._prefetch(None)
        updated = datetime.strptime(loaded['date'], "%Y-%m-%dT%H:%M:%S%z")

        return loaded['rev'], updated

    def _prefetch(self, ref: Optional[str]):
        cmd = ["nix-prefetch-git", "--quiet", "--fetch-submodules", self.uri]
        if ref is not None:
            cmd.append(ref)
        log.debug(cmd)
        data = subprocess.check_output(cmd)
        loaded = json.loads(data)
        return loaded

    def prefetch(self, ref: Optional[str]) -> str:
        loaded = self._prefetch(ref)
        return loaded["sha256"]

    def as_nix(self, plugin: "Plugin") -> str:
        return f'''fetchgit {{
            url = "{self.uri}";
            rev = "{plugin.commit}";
            sha256 = "{plugin.sha256}";
        }}'''


class RepoGitHub(Repo):
    def __init__(
        self, owner: str, repo: str, branch: str, alias: Optional[str]
    ) -> None:
        self.owner = owner
        self.repo = repo
        self.token = None
        '''Url to the repo'''
        super().__init__(self.url(""), branch, alias)
        log.debug("Instantiating github repo %s/%s", self.owner, self.repo)

    @property
    def name(self):
        return self.repo

    def url(self, path: str) -> str:
        return urljoin(f"https://github.com/{self.owner}/{self.name}/", path)

    @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"), self.token)
            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, self.token)
        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(self, commit: str) -> str:
        if self.has_submodules():
            sha256 = super().prefetch(commit)
        else:
            sha256 = self.prefetch_github(commit)
        return 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")

    def as_nix(self, plugin: "Plugin") -> str:
        if plugin.has_submodules:
            submodule_attr = "\n      fetchSubmodules = true;"
        else:
            submodule_attr = ""

        return f'''fetchFromGitHub {{
      owner = "{self.owner}";
      repo = "{self.repo}";
      rev = "{plugin.commit}";
      sha256 = "{plugin.sha256}";{submodule_attr}
    }}'''


@dataclass
class PluginDesc:
    repo: Repo
    branch: str
    alias: Optional[str]

    @property
    def name(self):
        if self.alias is None:
            return self.repo.name
        else:
            return self.alias


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, config: FetchConfig, plugin_file) -> List[PluginDesc]:
        plugins = []
        with open(plugin_file) as f:
            for line in f:
                if line.startswith("#"):
                    continue
                plugin = parse_plugin_line(config, line)
                plugins.append(plugin)
        return plugins

    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, config: FetchConfig):
        cache: Cache = Cache(self.get_current_plugins(), self.cache_file)
        _prefetch = functools.partial(prefetch, cache=cache)

        def update() -> dict:
            plugin_names = self.load_plugin_spec(config, input_file)

            try:
                pool = Pool(processes=config.proc)
                results = pool.map(_prefetch, plugin_names)
            finally:
                cache.store()

            plugins, redirects = check_results(results)

            self.generate_nix(plugins, outfile)

            return redirects

        return update


    @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.\n
                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. Setting --github-token allows higher values.",
        )
        parser.add_argument(
            "--github-token",
            "-t",
            type=str,
            default=os.getenv("GITHUB_API_TOKEN"),
            help="""Allows to set --proc to higher values.
            Uses GITHUB_API_TOKEN environment variables as the default value.""",
        )
        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", "--extra-experimental-features", "nix-command", "--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]]:
    repo, branch, alias = p.repo, p.branch, p.alias
    name = alias or p.repo.name
    commit = None
    log.info(f"Fetching last commit for plugin {name} from {repo.uri}@{branch}")
    commit, date = repo.latest_commit()
    cached_plugin = cache[commit] if cache else None
    if cached_plugin is not None:
        log.debug("Cache hit !")
        cached_plugin.name = name
        cached_plugin.date = date
        return cached_plugin, repo.redirect

    has_submodules = repo.has_submodules()
    print(f"prefetch {name}")
    sha256 = repo.prefetch(commit)

    return (
        Plugin(name, commit, has_submodules, sha256, date=date),
        repo.redirect,
    )


def fetch_plugin_from_pluginline(config: FetchConfig, plugin_line: str) -> Plugin:
    plugin, _ = prefetch_plugin(parse_plugin_line(config, 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[PluginDesc, Union[Exception, Plugin], Dict[str, str]]]
) -> Tuple[List[Tuple[PluginDesc, Plugin]], Dict[str, str]]:
    ''' '''
    failures: List[Tuple[str, Exception]] = []
    plugins = []
    redirects: Dict[str, str] = {}
    for (pdesc, result, redirect) in results:
        if isinstance(result, Exception):
            failures.append((pdesc.name, result))
        else:
            plugins.append((pdesc, 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 make_repo(uri, branch, alias) -> Repo:
    '''Instantiate a Repo with the correct specialization depending on server (gitub spec)'''
    # dumb check to see if it's of the form owner/repo (=> github) or https://...
    res = uri.split('/')
    if len(res) <= 2:
        repo = RepoGitHub(res[0], res[1], branch, alias)
    else:
        repo = Repo(uri.strip(), branch, alias)
    return repo

def parse_plugin_line(config: FetchConfig, line: str) -> PluginDesc:
    branch = "HEAD"
    alias = None
    uri = line
    if " as " in uri:
        uri, alias = uri.split(" as ")
        alias = alias.strip()
    if "@" in uri:
        uri, branch = uri.split("@")

    repo = make_repo(uri.strip(), branch.strip(), alias)
    repo.token = config.github_token

    return PluginDesc(repo, branch.strip(), alias)


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[PluginDesc, Union[Exception, Plugin], dict]:
    try:
        plugin, redirect = prefetch_plugin(pluginDesc, cache)
        cache[plugin.commit] = plugin
        return (pluginDesc, plugin, redirect)
    except Exception as e:
        return (pluginDesc, e, {})


def rewrite_input(
    config: FetchConfig,
    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(config, old)
            new_plugin = fetch_plugin_from_pluginline(config, 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 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")
    fetch_config = FetchConfig(args.proc, args.github_token)
    update = editor.get_update(args.input_file, args.outfile, fetch_config)

    redirects = update()
    editor.rewrite_input(fetch_config, args.input_file, editor.deprecated, redirects)

    autocommit = not args.no_commit

    nixpkgs_repo = None
    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(fetch_config, args.input_file, editor.deprecated, append=(plugin_line + "\n",))
        update()
        plugin = fetch_plugin_from_pluginline(fetch_config, 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],
            )