pferd/PFERD/ilias/downloader.py

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"""Contains a downloader for ILIAS."""
import datetime
import logging
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from dataclasses import dataclass
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from pathlib import Path
from typing import Callable, List, Optional
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import bs4
import requests
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from ..logging import PrettyLogger
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from ..organizer import Organizer
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from ..tmp_dir import TmpDir
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from ..transform import Transformable
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from ..utils import soupify, stream_to_path
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from .authenticators import IliasAuthenticator
LOGGER = logging.getLogger(__name__)
PRETTY = PrettyLogger(LOGGER)
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class ContentTypeException(Exception):
"""Thrown when the content type of the ilias element can not be handled."""
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@dataclass
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class IliasDownloadInfo(Transformable):
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"""
This class describes a single file to be downloaded.
"""
url: str
modification_date: Optional[datetime.datetime]
# parameters: Dict[str, Any] = field(default_factory=dict)
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IliasDownloadStrategy = Callable[[Organizer, IliasDownloadInfo], bool]
def download_everything(organizer: Organizer, info: IliasDownloadInfo) -> bool:
# pylint: disable=unused-argument
"""
Accepts everything.
"""
return True
def download_modified_or_new(organizer: Organizer, info: IliasDownloadInfo) -> bool:
"""
Accepts new files or files with a more recent modification date.
"""
resolved_file = organizer.resolve(info.path)
if not resolved_file.exists() or info.modification_date is None:
return True
resolved_mod_time_seconds = resolved_file.stat().st_mtime
# Download if the info is newer
if info.modification_date.timestamp() > resolved_mod_time_seconds:
return True
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PRETTY.ignored_file(info.path, "local file has newer or equal modification time")
return False
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class IliasDownloader:
# pylint: disable=too-many-arguments
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"""A downloader for ILIAS."""
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def __init__(
self,
tmp_dir: TmpDir,
organizer: Organizer,
session: requests.Session,
authenticator: IliasAuthenticator,
strategy: IliasDownloadStrategy,
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):
"""
Create a new IliasDownloader.
"""
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self._tmp_dir = tmp_dir
self._organizer = organizer
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self._session = session
self._authenticator = authenticator
self._strategy = strategy
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def download_all(self, infos: List[IliasDownloadInfo]) -> None:
"""
Download multiple files one after the other.
"""
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for info in infos:
self.download(info)
def download(self, info: IliasDownloadInfo) -> None:
"""
Download a file from ILIAS.
Retries authentication until eternity if it could not fetch the file.
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"""
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LOGGER.debug("Downloading %r", info)
if not self._strategy(self._organizer, info):
self._organizer.mark(info.path)
return
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tmp_file = self._tmp_dir.new_path()
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while not self._try_download(info, tmp_file):
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self._authenticator.authenticate(self._session)
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self._organizer.accept_file(tmp_file, info.path)
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def _try_download(self, info: IliasDownloadInfo, target: Path) -> bool:
with self._session.get(info.url, stream=True) as response:
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content_type = response.headers["content-type"]
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if content_type.startswith("text/html"):
# Dangit, we're probably not logged in.
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if self._is_logged_in(soupify(response)):
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raise ContentTypeException("Attempting to download a web page, not a file")
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return False
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# Yay, we got the file :)
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stream_to_path(response, target, info.path.name)
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return True
@staticmethod
def _is_logged_in(soup: bs4.BeautifulSoup) -> bool:
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userlog = soup.find("li", {"id": "userlog"})
return userlog is not None