"""Announcements handler for JupyterLab."""

# Copyright (c) Jupyter Development Team.
# Distributed under the terms of the Modified BSD License.

import abc
import hashlib
import json
import xml.etree.ElementTree as ET  # noqa
from dataclasses import asdict, dataclass, field
from datetime import datetime, timezone
from typing import Awaitable, Optional, Tuple, Union

from jupyter_server.base.handlers import APIHandler
from jupyterlab_server.translation_utils import translator
from packaging.version import parse
from tornado import httpclient, web

from jupyterlab._version import __version__

ISO8601_FORMAT = "%Y-%m-%dT%H:%M:%S%z"
JUPYTERLAB_LAST_RELEASE_URL = "https://pypi.org/pypi/jupyterlab/json"
JUPYTERLAB_RELEASE_URL = "https://github.com/jupyterlab/jupyterlab/releases/tag/v"


def format_datetime(dt_str: str):
    return datetime.fromisoformat(dt_str).timestamp() * 1000


@dataclass(frozen=True)
class Notification:
    """Notification

    Attributes:
        createdAt: Creation date
        message: Notification message
        modifiedAt: Modification date
        type: Notification type — ["default", "error", "info", "success", "warning"]
        link: Notification link button as a tuple (label, URL)
        options: Notification options
    """

    createdAt: float  # noqa
    message: str
    modifiedAt: float  # noqa
    type: str = "default"  # noqa
    link: Tuple[str, str] = field(default_factory=tuple)
    options: dict = field(default_factory=dict)


class CheckForUpdateABC(abc.ABC):
    """Abstract class to check for update.

    Args:
        version: Current JupyterLab version

    Attributes:
        version - str: Current JupyterLab version
        logger - logging.Logger: Server logger
    """

    def __init__(self, version: str) -> None:
        self.version = version

    @abc.abstractmethod
    async def __call__(self) -> Awaitable[Union[None, str, Tuple[str, Tuple[str, str]]]]:
        """Get the notification message if a new version is available.

        Returns:
            None if there is not update.
            or the notification message
            or the notification message and a tuple(label, URL link) for the user to get more information
        """
        msg = "CheckForUpdateABC.__call__ is not implemented"
        raise NotImplementedError(msg)


class CheckForUpdate(CheckForUpdateABC):
    """Default class to check for update.

    Args:
        version: Current JupyterLab version

    Attributes:
        version - str: Current JupyterLab version
        logger - logging.Logger: Server logger
    """

    async def __call__(self) -> Awaitable[Tuple[str, Tuple[str, str]]]:
        """Get the notification message if a new version is available.

        Returns:
            None if there is no update.
            or the notification message
            or the notification message and a tuple(label, URL link) for the user to get more information
        """
        http_client = httpclient.AsyncHTTPClient()
        try:
            response = await http_client.fetch(
                JUPYTERLAB_LAST_RELEASE_URL,
                headers={"Content-Type": "application/json"},
            )
            data = json.loads(response.body).get("info")
            last_version = data["version"]
        except Exception as e:
            self.logger.debug("Failed to get latest version", exc_info=e)
            return None
        else:
            if parse(self.version) < parse(last_version):
                trans = translator.load("jupyterlab")
                return (
                    trans.__(f"A newer version ({last_version}) of JupyterLab is available."),
                    (trans.__("Open changelog"), f"{JUPYTERLAB_RELEASE_URL}{last_version}"),
                )
            else:
                return None


class NeverCheckForUpdate(CheckForUpdateABC):
    """Check update version that does nothing.

    This is provided for administrators that want to
    turn off requesting external resources.

    Args:
        version: Current JupyterLab version

    Attributes:
        version - str: Current JupyterLab version
        logger - logging.Logger: Server logger
    """

    async def __call__(self) -> Awaitable[None]:
        """Get the notification message if a new version is available.

        Returns:
            None if there is no update.
            or the notification message
            or the notification message and a tuple(label, URL link) for the user to get more information
        """
        return None


class CheckForUpdateHandler(APIHandler):
    """Check for Updates API handler.

    Args:
        update_check: The class checking for a new version
    """

    def initialize(
        self,
        update_checker: Optional[CheckForUpdate] = None,
    ) -> None:
        super().initialize()
        self.update_checker = (
            NeverCheckForUpdate(__version__) if update_checker is None else update_checker
        )
        self.update_checker.logger = self.log

    @web.authenticated
    async def get(self):
        """Check for updates.
        Response:
            {
                "notification": Optional[Notification]
            }
        """
        notification = None
        out = await self.update_checker()
        if out:
            message, link = (out, ()) if isinstance(out, str) else out
            now = datetime.now(tz=timezone.utc).timestamp() * 1000.0
            hash_ = hashlib.sha1(message.encode()).hexdigest()  # noqa: S324
            notification = Notification(
                message=message,
                createdAt=now,
                modifiedAt=now,
                type="info",
                link=link,
                options={"data": {"id": hash_, "tags": ["update"]}},
            )

        self.set_status(200)
        self.finish(
            json.dumps({"notification": None if notification is None else asdict(notification)})
        )


class NewsHandler(APIHandler):
    """News API handler.

    Args:
        news_url: The Atom feed to fetch for news
    """

    def initialize(
        self,
        news_url: Optional[str] = None,
    ) -> None:
        super().initialize()
        self.news_url = news_url

    @web.authenticated
    async def get(self):
        """Get the news.

        Response:
            {
                "news": List[Notification]
            }
        """
        news = []

        http_client = httpclient.AsyncHTTPClient()

        if self.news_url is not None:
            trans = translator.load("jupyterlab")

            # Those registrations are global, naming them to reduce chance of clashes
            xml_namespaces = {"atom": "http://www.w3.org/2005/Atom"}
            for key, spec in xml_namespaces.items():
                ET.register_namespace(key, spec)

            try:
                response = await http_client.fetch(
                    self.news_url,
                    headers={"Content-Type": "application/atom+xml"},
                )
                tree = ET.fromstring(response.body)  # noqa S314

                def build_entry(node):
                    def get_xml_text(attr: str, default: Optional[str] = None) -> str:
                        node_item = node.find(f"atom:{attr}", xml_namespaces)
                        if node_item is not None:
                            return node_item.text
                        elif default is not None:
                            return default
                        else:
                            error_m = (
                                f'atom feed entry does not contain a required attribute: {attr}'
                            )
                            raise KeyError(error_m)

                    entry_title = get_xml_text("title")
                    entry_id = get_xml_text("id")
                    entry_updated = get_xml_text("updated")
                    entry_published = get_xml_text("published", entry_updated)
                    entry_summary = get_xml_text("summary", default='')
                    links = node.findall("atom:link", xml_namespaces)
                    if len(links) > 1:
                        alternate = list(filter(lambda elem: elem.get('rel') == 'alternate', links))
                        link_node = alternate[0] if alternate else links[0]
                    else:
                        link_node = links[0] if len(links) == 1 else None
                    entry_link = link_node.get("href") if link_node is not None else None

                    message = (
                        "\n".join([entry_title, entry_summary]) if entry_summary else entry_title
                    )
                    modified_at = format_datetime(entry_updated)
                    created_at = format_datetime(entry_published)
                    notification = Notification(
                        message=message,
                        createdAt=created_at,
                        modifiedAt=modified_at,
                        type="info",
                        link=None
                        if entry_link is None
                        else (
                            trans.__("Open full post"),
                            entry_link,
                        ),
                        options={
                            "data": {
                                "id": entry_id,
                                "tags": ["news"],
                            }
                        },
                    )
                    return notification

                entries = map(build_entry, tree.findall("atom:entry", xml_namespaces))
                news.extend(entries)
            except Exception as e:
                self.log.debug(
                    f"Failed to get announcements from Atom feed: {self.news_url}",
                    exc_info=e,
                )

        self.set_status(200)
        self.finish(json.dumps({"news": list(map(asdict, news))}))


news_handler_path = r"/lab/api/news"
check_update_handler_path = r"/lab/api/update"
