pferd/PFERD/ilias/crawler.py

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"""
Contains an ILIAS crawler alongside helper functions.
"""
import datetime
import json
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import logging
import re
from pathlib import Path
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from typing import Any, Callable, Dict, List, Optional
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from urllib.parse import (parse_qs, urlencode, urljoin, urlparse, urlsplit,
urlunsplit)
import bs4
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import requests
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from ..cookie_jar import CookieJar
from ..utils import soupify
from .authenticators import IliasAuthenticator
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from .date_demangler import demangle_date
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from .downloader import IliasDownloadInfo
LOGGER = logging.getLogger(__name__)
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IliasFilter = Callable[[Path], bool]
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class IliasCrawler:
# pylint: disable=too-few-public-methods
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# TODO use the filter as appropriate
# TODO log the things that were discovered to the console on INFO
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"""
A crawler for ILIAS.
"""
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def __init__(
self,
base_url: str,
course_id: str,
session: requests.Session,
authenticator: IliasAuthenticator,
filter_: IliasFilter
):
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"""
Create a new ILIAS crawler.
"""
self._base_url = base_url
self._course_id = course_id
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self._session = session
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self._authenticator = authenticator
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self._filter = filter_
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def _abs_url_from_link(self, link_tag: bs4.Tag) -> str:
"""
Create an absolute url from an <a> tag.
"""
return urljoin(self._base_url, link_tag.get("href"))
@staticmethod
def _url_set_query_param(url: str, param: str, value: str) -> str:
"""
Set a query parameter in an url, overwriting existing ones with the same name.
"""
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scheme, netloc, path, query, fragment = urlsplit(url)
query_parameters = parse_qs(query)
query_parameters[param] = [value]
new_query_string = urlencode(query_parameters, doseq=True)
return urlunsplit((scheme, netloc, path, new_query_string, fragment))
def crawl(self) -> List[IliasDownloadInfo]:
"""
Starts the crawl process, yielding a list of elements to (potentially) download.
"""
# Start crawling at the given course
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root_url = self._url_set_query_param(
self._base_url + "/goto.php", "target", f"crs_{self._course_id}"
)
# And treat it as a folder
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return self._crawl_folder(Path(""), root_url)
def _switch_on_crawled_type(
self,
path: Path,
link_element: bs4.Tag,
url: str
) -> List[IliasDownloadInfo]:
"""
Decides which sub crawler to use for a given top level element.
"""
parsed_url = urlparse(url)
LOGGER.debug("Parsed url: %r", parsed_url)
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# file URLs contain "target=file"
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if "target=file_" in parsed_url.query:
LOGGER.debug("Interpreted as file.")
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return self._crawl_file(path, link_element, url)
# Skip forums
if "cmd=showThreads" in parsed_url.query:
LOGGER.debug("Skipping forum %r", url)
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return []
# Everything with a ref_id can *probably* be opened to reveal nested things
# video groups, directories, exercises, etc
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if "ref_id=" in parsed_url.query:
LOGGER.debug("Processing folder-like...")
return self._switch_on_folder_like(path, link_element, url)
LOGGER.warning("Got unknown type, %r, %r, %r", path, link_element, url)
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# TODO: Other types
raise Exception("Implement me!")
@staticmethod
def _crawl_file(path: Path, link_element: bs4.Tag, url: str) -> List[IliasDownloadInfo]:
"""
Crawls a file.
"""
# Files have a list of properties (type, modification date, size, etc.)
# In a series of divs.
# Find the parent containing all those divs, so we can filter our what we need
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properties_parent: bs4.Tag = link_element.findParent(
"div", {"class": lambda x: "il_ContainerListItem" in x}
).select_one(".il_ItemProperties")
# The first one is always the filetype
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file_type = properties_parent.select_one("span.il_ItemProperty").getText().strip()
# The rest does not have a stable order. Grab the whole text and reg-ex the date
# out of it
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all_properties_text = properties_parent.getText().strip()
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modification_date_match = re.search(
r"(((\d+\. \w+ \d+)|(Gestern)|(Heute)), \d+:\d+)",
all_properties_text
)
if modification_date_match is None:
modification_date = datetime.datetime.now()
LOGGER.warning("Could not extract start date from %r", all_properties_text)
else:
modification_date_str = modification_date_match.group(1)
modification_date = demangle_date(modification_date_str)
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# Grab the name from the link text
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name = link_element.getText()
full_path = Path(path, name + "." + file_type)
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return [IliasDownloadInfo(full_path, url, modification_date)]
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def _switch_on_folder_like(
self,
path: Path,
link_element: bs4.Tag,
url: str
) -> List[IliasDownloadInfo]:
"""
Try crawling something that looks like a folder.
"""
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found_parent: Optional[bs4.Tag] = None
# We look for the outer div of our inner link, to find information around it
# (mostly the icon)
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for parent in link_element.parents:
if "ilContainerListItemOuter" in parent["class"]:
found_parent = parent
break
if found_parent is None:
LOGGER.warning("Could not find element icon for %r", url)
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return []
# Find the small descriptive icon to figure out the type
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img_tag: Optional[bs4.Tag] = found_parent.select_one("img.ilListItemIcon")
if img_tag is None:
LOGGER.warning("Could not find image tag for %r", url)
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return []
# A forum
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if str(img_tag["src"]).endswith("frm.svg"):
LOGGER.debug("Skipping forum at %r", url)
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return []
element_path = Path(path, link_element.getText().strip())
# An exercise
if str(img_tag["src"]).endswith("icon_exc.svg"):
LOGGER.debug("Crawling exercises at %r", url)
return self._crawl_exercises(element_path, url)
# Match the opencast video plugin
if "opencast" in str(img_tag["alt"]).lower():
LOGGER.debug("Found video site: %r", url)
return self._crawl_video_directory(element_path, url)
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# Assume it is a folder
return self._crawl_folder(element_path, self._abs_url_from_link(link_element))
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def _crawl_video_directory(self, path: Path, url: str) -> List[IliasDownloadInfo]:
"""
Crawl the video overview site.
"""
initial_soup = self._get_page(url, {})
# The page is actually emtpy but contains a much needed token in the link below.
# That token can be used to fetch the *actual* video listing
content_link: bs4.Tag = initial_soup.select_one("#tab_series a")
# Fetch the actual video listing. The given parameters return all videos (max 800)
# in a standalone html page
video_list_soup = self._get_page(
self._abs_url_from_link(content_link),
{"limit": 800, "cmd": "asyncGetTableGUI", "cmdMode": "asynch"}
)
# Video start links are marked with an "Abspielen" link
video_links: List[bs4.Tag] = video_list_soup.findAll(
name="a", text=re.compile(r"\s*Abspielen\s*")
)
results: List[IliasDownloadInfo] = []
for link in video_links:
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results += self._crawl_single_video(path, link)
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return results
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def _crawl_single_video(self, path: Path, link: bs4.Tag) -> List[IliasDownloadInfo]:
"""
Crawl a single video based on its "Abspielen" link from the video listing.
"""
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video_page_url = self._abs_url_from_link(link)
# The link is part of a table with multiple columns, describing metadata.
# 6th child (1 indexed) is the modification time string
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modification_string = link.parent.parent.parent.select_one(
"td.std:nth-child(6)"
).getText().strip()
modification_time = datetime.datetime.strptime(modification_string, "%d.%m.%Y - %H:%M")
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title = link.parent.parent.parent.select_one(
"td.std:nth-child(3)"
).getText().strip()
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title += ".mp4"
# Fetch the actual video page. This is a small wrapper page initializing a javscript
# player. Sadly we can not execute that JS. The actual video stream url is nowhere
# on the page, but defined in a JS object inside a script tag, passed to the player
# library.
# We do the impossible and RegEx the stream JSON object out of the page's HTML source
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video_page_soup = self._get_page(video_page_url, {})
regex: re.Pattern = re.compile(
r"({\"streams\"[\s\S]+?),\s*{\"paella_config_file", re.IGNORECASE
)
json_match = regex.search(str(video_page_soup))
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if json_match is None:
LOGGER.warning("Could not find json stream info for %r", video_page_url)
return []
json_str = json_match.group(1)
# parse it
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json_object = json.loads(json_str)
# and fetch the video url!
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video_url = json_object["streams"][0]["sources"]["mp4"][0]["src"]
return [IliasDownloadInfo(Path(path, title), video_url, modification_time)]
def _crawl_exercises(self, element_path: Path, url: str) -> List[IliasDownloadInfo]:
"""
Crawl files offered for download in exercises.
"""
soup = self._get_page(url, {})
results: List[IliasDownloadInfo] = []
# Each assignment is in an accordion container
assignment_containers: List[bs4.Tag] = soup.select(".il_VAccordionInnerContainer")
for container in assignment_containers:
# Fetch the container name out of the header to use it in the path
container_name = container.select_one(".ilAssignmentHeader").getText().strip()
# Find all download links in the container (this will contain all the files)
files: List[bs4.Tag] = container.findAll(
name="a",
# download links contain the given command class
attrs={"href": lambda x: x and "cmdClass=ilexsubmissiongui" in x},
text="Download"
)
LOGGER.debug("Found exercise container %r", container_name)
# Parse the end date to use as modification date
# TODO: Return None?
end_date: datetime.datetime = datetime.datetime.now()
end_date_header: bs4.Tag = container.find(name="div", text="Abgabetermin")
if end_date_header is not None:
end_date_text = end_date_header.findNext("div").getText().strip()
end_date = demangle_date(end_date_text)
# Grab each file as you now have the link
for file_link in files:
# Two divs, side by side. Left is the name, right is the link ==> get left
# sibling
file_name = file_link.parent.findPrevious(name="div").getText().strip()
url = self._abs_url_from_link(file_link)
LOGGER.debug("Found file %r at %r", file_name, url)
results.append(IliasDownloadInfo(
Path(element_path, container_name, file_name),
url,
end_date
))
return results
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def _crawl_folder(self, path: Path, url: str) -> List[IliasDownloadInfo]:
"""
Crawl all files in a folder-like element.
"""
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soup = self._get_page(url, {})
result: List[IliasDownloadInfo] = []
# Fetch all links and throw them to the general interpreter
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links: List[bs4.Tag] = soup.select("a.il_ContainerItemTitle")
for link in links:
abs_url = self._abs_url_from_link(link)
result += self._switch_on_crawled_type(path, link, abs_url)
return result
def _get_page(self, url: str, params: Dict[str, Any]) -> bs4.BeautifulSoup:
"""
Fetches a page from ILIAS, authenticating when needed.
"""
LOGGER.debug("Fetching %r", url)
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response = self._session.get(url, params=params)
content_type = response.headers["content-type"]
if not content_type.startswith("text/html"):
# TODO: Correct exception type
raise Exception(f"Invalid content type {content_type}")
soup = soupify(response)
if self._is_logged_in(soup):
return soup
LOGGER.info("Not authenticated, changing that...")
self._authenticator.authenticate(self._session)
return self._get_page(url, params)
@staticmethod
def _is_logged_in(soup: bs4.BeautifulSoup) -> bool:
# Normal ILIAS pages
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userlog = soup.find("li", {"id": "userlog"})
if userlog is not None:
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LOGGER.debug("Auth: Found #userlog")
return True
# Video listing embeds do not have complete ILIAS html. Try to match them by
# their video listing table
video_table = soup.find(
recursive=True,
name="table",
attrs={"id": lambda x: x is not None and x.startswith("tbl_xoct")}
)
if video_table is not None:
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LOGGER.debug("Auth: Found #tbl_xoct.+")
return True
# The individual video player wrapper page has nothing of the above.
# Match it by its playerContainer.
if soup.select_one("#playerContainer") is not None:
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LOGGER.debug("Auth: Found #playerContainer")
return True
return False