Save stacktraces in context manager and print on error

Crawl the info tab of courses again
This got lost in a refactor
2026-01-08 13:42:30 +01:00 · 2025-12-09 17:01:24 +01:00 · 2025-12-02 22:37:32 +01:00 · 2025-10-30 20:19:37 +01:00 · 2025-10-29 13:11:34 +01:00 · 2025-10-28 11:47:28 +01:00
51 changed files with 3465 additions and 1622 deletions
--- a/.git-blame-ignore-revs
+++ b/.git-blame-ignore-revs
@@ -0,0 +1 @@
+2cf0e060ed126537dd993896b6aa793e2a6b9e80
--- a/.github/workflows/build-and-release.yml
+++ b/.github/workflows/build-and-release.yml
@@ -14,23 +14,17 @@ jobs:
      fail-fast: false
      matrix:
        os: [ubuntu-latest, windows-latest, macos-13, macos-latest]
-        python: ["3.9"]
+        python: ["3.11"]
    steps:
      - uses: actions/checkout@v4

-      - uses: actions/setup-python@v5
+      - name: Install uv
+        uses: astral-sh/setup-uv@v7
        with:
          python-version: ${{ matrix.python }}

      - name: Set up project
-        if: matrix.os != 'windows-latest'
-        run: ./scripts/setup
-
-      - name: Set up project on windows
-        if: matrix.os == 'windows-latest'
-        # For some reason, `pip install --upgrade pip` doesn't work on
-        # 'windows-latest'. The installed pip version works fine however.
-        run: ./scripts/setup --no-pip
+        run: uv sync

      - name: Run checks
        run: |
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -22,6 +22,82 @@ ambiguous situations.

 ## Unreleased

+## Added
+- Store the description when using the `internet-shortcut` link format
+- Support for basic auth with the kit-ipd crawler
+
+## Fixed
+- Event loop errors on Windows with Python 3.14
+- Sanitize `/` in headings in kit-ipd crawler
+- Crawl info tab again
+
+## 3.8.3 - 2025-07-01
+
+## Added
+- Support for link collections.  
+  In "fancy" mode, a single HTML file with multiple links is generated.
+  In all other modes, PFERD creates a folder for the collection and a new file
+  for every link inside.
+
+## Fixed
+- Crawling of exercises with instructions
+- Don't download unavailable elements.  
+  Elements that are unavailable (for example, because their availability is
+  time restricted) will not download the HTML for the info page anymore.
+- `base_url` argument for `ilias-web` crawler causing crashes
+
+## 3.8.2 - 2025-04-29
+
+## Changed
+- Explicitly mention that wikis are not supported at the moment and ignore them
+
+## Fixed
+- Ilias-native login
+- Exercise crawling
+
+## 3.8.1 - 2025-04-17
+
+## Fixed
+- Description html files now specify at UTF-8 encoding
+- Images in descriptions now always have a white background
+
+## 3.8.0 - 2025-04-16
+
+### Added
+- Support for ILIAS 9
+
+### Changed
+- Added prettier CSS to forum threads
+- Downloaded forum threads now link to the forum instead of the ILIAS thread
+- Increase minimum supported Python version to 3.11
+- Do not crawl nested courses (courses linked in other courses)
+
+## Fixed
+- File links in report on Windows
+- TOTP authentication in KIT Shibboleth
+- Forum crawling only considering the first 20 entries
+
+## 3.7.0 - 2024-11-13
+
+### Added
+- Support for MOB videos in page descriptions
+- Clickable links in the report to directly open new/modified/not-deleted files
+- Support for non KIT shibboleth login
+
+### Changed
+- Remove videos from description pages
+- Perform ILIAS cycle detection after processing the transform to allow
+  ignoring duplicated elements
+- Parse headings (h1-h3) as folders in kit-ipd crawler
+
+### Fixed
+- Personal desktop/dashboard/favorites crawling
+- Crawling of nested courses
+- Downloading of links with no target URL
+- Handle row flex on description pages
+- Add `<!DOCTYPE html>` heading to forum threads to fix mime type detection
+- Handle groups in cards
+
 ## 3.6.0 - 2024-10-23

 ### Added
--- a/CONFIG.md
+++ b/CONFIG.md
@@ -153,6 +153,7 @@ requests is likely a good idea.
 - `link_regex`: A regex that is matched against the `href` part of links. If it
  matches, the given link is downloaded as a file. This is used to extract
  files from KIT-IPD pages. (Default: `^.*?[^/]+\.(pdf|zip|c|cpp|java)$`)
+- `auth`: Name of auth section to use for basic authentication. (Optional)

 ### The `ilias-web` crawler

@@ -163,12 +164,15 @@ out of the box for the corresponding universities:

 [ilias-dl]: https://github.com/V3lop5/ilias-downloader/blob/main/configs "ilias-downloader configs"

-| University    | `base_url`                           | `client_id`   |
-|---------------|--------------------------------------|---------------|
-| FH Aachen     | https://www.ili.fh-aachen.de         | elearning     |
-| Uni Köln      | https://www.ilias.uni-koeln.de/ilias | uk            |
-| Uni Konstanz  | https://ilias.uni-konstanz.de        | ILIASKONSTANZ |
-| Uni Stuttgart | https://ilias3.uni-stuttgart.de      | Uni_Stuttgart |
+| University      | `base_url`                              | `login_type` | `client_id`   |
+|-----------------|-----------------------------------------|--------------|---------------|
+| FH Aachen       | https://www.ili.fh-aachen.de            | local        | elearning     |
+| HHU Düsseldorf  | https://ilias.hhu.de                    | local        | UniRZ         |
+| Uni Köln        | https://www.ilias.uni-koeln.de/ilias    | local        | uk            |
+| Uni Konstanz    | https://ilias.uni-konstanz.de           | local        | ILIASKONSTANZ |
+| Uni Stuttgart   | https://ilias3.uni-stuttgart.de         | local        | Uni_Stuttgart |
+| Uni Tübingen    | https://ovidius.uni-tuebingen.de/ilias3 | shibboleth   |               |
+| KIT ILIAS Pilot | https://pilot.ilias.studium.kit.edu     | shibboleth   | pilot         |

 If your university isn't listed, try navigating to your instance's login page.
 Assuming no custom login service is used, the URL will look something like this:
@@ -180,7 +184,11 @@ Assuming no custom login service is used, the URL will look something like this:
 If the values work, feel free to submit a PR and add them to the table above.

 - `base_url`: The URL where the ILIAS instance is located. (Required)
- `client_id`: An ID used for authentication. (Required)
+- `login_type`: How you authenticate. (Required)
+    - `local`: Use `client_id` for authentication.
+    - `shibboleth`: Use shibboleth for authentication.
+- `client_id`: An ID used for authentication if `login_type` is `local`. Is
+  ignored if `login_type` is `shibboleth`.
 - `target`: The ILIAS element to crawl. (Required)
    - `desktop`: Crawl your personal desktop / dashboard
    - `<course id>`: Crawl the course with the given id
@@ -191,6 +199,8 @@ If the values work, feel free to submit a PR and add them to the table above.
      and duplication warnings if you are a member of an ILIAS group. The
      `desktop` target is generally preferable.
 - `auth`: Name of auth section to use for login. (Required)
+- `tfa_auth`: Name of auth section to use for two-factor authentication. Only
+  uses the auth section's password. (Default: Anonymous `tfa` authenticator)
 - `links`: How to represent external links. (Default: `fancy`)
    - `ignore`: Don't download links.
    - `plaintext`: A text file containing only the URL.
--- a/DEV.md
+++ b/DEV.md
@@ -9,30 +9,25 @@ particular [this][ppug-1] and [this][ppug-2] guide).

 ## Setting up a dev environment

-The use of [venv][venv] is recommended. To initially set up a development
-environment, run these commands in the same directory as this file:
+The use of [venv][venv] and [uv][uv] is recommended. To initially set up a
+development environment, run these commands in the same directory as this file:

 ```
-$ python -m venv .venv
+$ uv sync
 $ . .venv/bin/activate
-$ ./scripts/setup
 ```

-The setup script installs a few required dependencies and tools. It also
-installs PFERD via `pip install --editable .`, which means that you can just run
-`pferd` as if it was installed normally. Since PFERD was installed with
-`--editable`, there is no need to re-run `pip install` when the source code is
-changed.
-
-If you get any errors because pip can't update itself, try running
-`./scripts/setup --no-pip` instead of `./scripts/setup`.
+This install all required dependencies and tools. It also installs PFERD as
+*editable*, which means that you can just run `pferd` as if it was installed
+normally. Since PFERD was installed with `--editable`, there is no need to
+re-run `uv sync` when the source code is changed.

 For more details, see [this part of the Python Tutorial][venv-tut] and
 [this section on "development mode"][ppug-dev].

 [venv]: <https://docs.python.org/3/library/venv.html> "venv - Creation of virtual environments"
 [venv-tut]: <https://docs.python.org/3/tutorial/venv.html> "12. Virtual Environments and Packages"
-[ppug-dev]: <https://packaging.python.org/guides/distributing-packages-using-setuptools/#working-in-development-mode> "Working in “development mode”"
+[uv]: <https://docs.astral.sh/uv/> "uv - An extremely fast Python package and project manager"

 ## Checking and formatting the code

--- a/2
+++ b/2
@@ -1,6 +1,6 @@
 Copyright 2019-2024 Garmelon, I-Al-Istannen, danstooamerican, pavelzw,
                    TheChristophe, Scriptim, thelukasprobst, Toorero,
-                    Mr-Pine, p-fruck
+                    Mr-Pine, p-fruck, PinieP

 Permission is hereby granted, free of charge, to any person obtaining a copy of
 this software and associated documentation files (the "Software"), to deal in
--- a/PFERD/main.py
+++ b/PFERD/main.py
@@ -133,7 +133,8 @@ def main() -> None:
            # https://bugs.python.org/issue39232
            # https://github.com/encode/httpx/issues/914#issuecomment-780023632
            # TODO Fix this properly
-            loop = asyncio.get_event_loop()
+            loop = asyncio.new_event_loop()
+            asyncio.set_event_loop(loop)
            loop.run_until_complete(pferd.run(args.debug_transforms))
            loop.run_until_complete(asyncio.sleep(1))
            loop.close()
--- a/PFERD/auth/init.py
+++ b/PFERD/auth/init.py
@@ -1,5 +1,5 @@
+from collections.abc import Callable
 from configparser import SectionProxy
-from typing import Callable, Dict

 from ..config import Config
 from .authenticator import Authenticator, AuthError, AuthLoadError, AuthSection  # noqa: F401
@@ -9,21 +9,19 @@ from .pass_ import PassAuthenticator, PassAuthSection
 from .simple import SimpleAuthenticator, SimpleAuthSection
 from .tfa import TfaAuthenticator

-AuthConstructor = Callable[[
-    str,                # Name (without the "auth:" prefix)
-    SectionProxy,       # Authenticator's section of global config
-    Config,             # Global config
-], Authenticator]
+AuthConstructor = Callable[
+    [
+        str,  # Name (without the "auth:" prefix)
+        SectionProxy,  # Authenticator's section of global config
+        Config,  # Global config
+    ],
+    Authenticator,
+]

-AUTHENTICATORS: Dict[str, AuthConstructor] = {
-    "credential-file": lambda n, s, c:
-        CredentialFileAuthenticator(n, CredentialFileAuthSection(s), c),
-    "keyring": lambda n, s, c:
-        KeyringAuthenticator(n, KeyringAuthSection(s)),
-    "pass": lambda n, s, c:
-        PassAuthenticator(n, PassAuthSection(s)),
-    "simple": lambda n, s, c:
-        SimpleAuthenticator(n, SimpleAuthSection(s)),
-    "tfa": lambda n, s, c:
-        TfaAuthenticator(n),
+AUTHENTICATORS: dict[str, AuthConstructor] = {
+    "credential-file": lambda n, s, c: CredentialFileAuthenticator(n, CredentialFileAuthSection(s), c),
+    "keyring": lambda n, s, c: KeyringAuthenticator(n, KeyringAuthSection(s)),
+    "pass": lambda n, s, c: PassAuthenticator(n, PassAuthSection(s)),
+    "simple": lambda n, s, c: SimpleAuthenticator(n, SimpleAuthSection(s)),
+    "tfa": lambda n, s, c: TfaAuthenticator(n),
 }
--- a/PFERD/auth/authenticator.py
+++ b/PFERD/auth/authenticator.py
@@ -1,5 +1,4 @@
 from abc import ABC, abstractmethod
-from typing import Tuple

 from ..config import Section

@@ -35,7 +34,7 @@ class Authenticator(ABC):
        self.name = name

    @abstractmethod
-    async def credentials(self) -> Tuple[str, str]:
+    async def credentials(self) -> tuple[str, str]:
        pass

    async def username(self) -> str:
--- a/PFERD/auth/credential_file.py
+++ b/PFERD/auth/credential_file.py
@@ -1,5 +1,4 @@
 from pathlib import Path
-from typing import Tuple

 from ..config import Config
 from ..utils import fmt_real_path
@@ -23,7 +22,9 @@ class CredentialFileAuthenticator(Authenticator):
            with open(path, encoding="utf-8") as f:
                lines = list(f)
        except UnicodeDecodeError:
-            raise AuthLoadError(f"Credential file at {fmt_real_path(path)} is not encoded using UTF-8")
+            raise AuthLoadError(
+                f"Credential file at {fmt_real_path(path)} is not encoded using UTF-8"
+            ) from None
        except OSError as e:
            raise AuthLoadError(f"No credential file at {fmt_real_path(path)}") from e

@@ -42,5 +43,5 @@ class CredentialFileAuthenticator(Authenticator):
        self._username = uline[9:]
        self._password = pline[9:]

-    async def credentials(self) -> Tuple[str, str]:
+    async def credentials(self) -> tuple[str, str]:
        return self._username, self._password
--- a/PFERD/auth/keyring.py
+++ b/PFERD/auth/keyring.py
@@ -1,4 +1,4 @@
-from typing import Optional, Tuple
+from typing import Optional

 import keyring

@@ -17,7 +17,6 @@ class KeyringAuthSection(AuthSection):


 class KeyringAuthenticator(Authenticator):
-
    def __init__(self, name: str, section: KeyringAuthSection) -> None:
        super().__init__(name)

@@ -28,7 +27,7 @@ class KeyringAuthenticator(Authenticator):
        self._password_invalidated = False
        self._username_fixed = section.username() is not None

-    async def credentials(self) -> Tuple[str, str]:
+    async def credentials(self) -> tuple[str, str]:
        # Request the username
        if self._username is None:
            async with log.exclusive_output():
--- a/PFERD/auth/pass_.py
+++ b/PFERD/auth/pass_.py
@@ -1,6 +1,5 @@
 import re
 import subprocess
-from typing import List, Tuple

 from ..logging import log
 from .authenticator import Authenticator, AuthError, AuthSection
@@ -12,11 +11,11 @@ class PassAuthSection(AuthSection):
            self.missing_value("passname")
        return value

-    def username_prefixes(self) -> List[str]:
+    def username_prefixes(self) -> list[str]:
        value = self.s.get("username_prefixes", "login,username,user")
        return [prefix.lower() for prefix in value.split(",")]

-    def password_prefixes(self) -> List[str]:
+    def password_prefixes(self) -> list[str]:
        value = self.s.get("password_prefixes", "password,pass,secret")
        return [prefix.lower() for prefix in value.split(",")]

@@ -31,14 +30,14 @@ class PassAuthenticator(Authenticator):
        self._username_prefixes = section.username_prefixes()
        self._password_prefixes = section.password_prefixes()

-    async def credentials(self) -> Tuple[str, str]:
+    async def credentials(self) -> tuple[str, str]:
        log.explain_topic("Obtaining credentials from pass")

        try:
            log.explain(f"Calling 'pass show {self._passname}'")
            result = subprocess.check_output(["pass", "show", self._passname], text=True)
        except subprocess.CalledProcessError as e:
-            raise AuthError(f"Failed to get password info from {self._passname}: {e}")
+            raise AuthError(f"Failed to get password info from {self._passname}: {e}") from e

        prefixed = {}
        unprefixed = []
--- a/PFERD/auth/simple.py
+++ b/PFERD/auth/simple.py
@@ -1,4 +1,4 @@
-from typing import Optional, Tuple
+from typing import Optional

 from ..logging import log
 from ..utils import agetpass, ainput
@@ -23,7 +23,7 @@ class SimpleAuthenticator(Authenticator):
        self._username_fixed = self.username is not None
        self._password_fixed = self.password is not None

-    async def credentials(self) -> Tuple[str, str]:
+    async def credentials(self) -> tuple[str, str]:
        if self._username is not None and self._password is not None:
            return self._username, self._password

--- a/PFERD/auth/tfa.py
+++ b/PFERD/auth/tfa.py
@@ -1,5 +1,3 @@
-from typing import Tuple
-
 from ..logging import log
 from ..utils import ainput
 from .authenticator import Authenticator, AuthError
@@ -17,7 +15,7 @@ class TfaAuthenticator(Authenticator):
            code = await ainput("TFA code: ")
            return code

-    async def credentials(self) -> Tuple[str, str]:
+    async def credentials(self) -> tuple[str, str]:
        raise AuthError("TFA authenticator does not support usernames")

    def invalidate_username(self) -> None:
--- a/PFERD/cli/command_ilias_web.py
+++ b/PFERD/cli/command_ilias_web.py
@@ -21,23 +21,20 @@ GROUP.add_argument(
    "--base-url",
    type=str,
    metavar="BASE_URL",
-    help="The base url of the ilias instance"
+    help="The base url of the ilias instance",
 )

 GROUP.add_argument(
    "--client-id",
    type=str,
    metavar="CLIENT_ID",
-    help="The client id of the ilias instance"
+    help="The client id of the ilias instance",
 )

 configure_common_group_args(GROUP)


-def load(
-        args: argparse.Namespace,
-        parser: configparser.ConfigParser,
-) -> None:
+def load(args: argparse.Namespace, parser: configparser.ConfigParser) -> None:
    log.explain(f"Creating config for command '{COMMAND_NAME}'")

    parser["crawl:ilias"] = {}
@@ -45,8 +42,8 @@ def load(
    load_crawler(args, section)

    section["type"] = COMMAND_NAME
-    if args.ilias_url is not None:
-        section["base_url"] = args.ilias_url
+    if args.base_url is not None:
+        section["base_url"] = args.base_url
    if args.client_id is not None:
        section["client_id"] = args.client_id

--- a/PFERD/cli/command_kit_ilias_web.py
+++ b/PFERD/cli/command_kit_ilias_web.py
@@ -21,8 +21,8 @@ configure_common_group_args(GROUP)


 def load(
-        args: argparse.Namespace,
-        parser: configparser.ConfigParser,
+    args: argparse.Namespace,
+    parser: configparser.ConfigParser,
 ) -> None:
    log.explain(f"Creating config for command '{COMMAND_NAME}'")

--- a/PFERD/cli/command_kit_ipd.py
+++ b/PFERD/cli/command_kit_ipd.py
@@ -18,25 +18,30 @@ GROUP.add_argument(
    "--link-regex",
    type=str,
    metavar="REGEX",
-    help="href-matching regex to identify downloadable files"
+    help="href-matching regex to identify downloadable files",
+)
+GROUP.add_argument(
+    "--basic-auth",
+    action="store_true",
+    help="enable basic authentication",
 )
 GROUP.add_argument(
    "target",
    type=str,
    metavar="TARGET",
-    help="url to crawl"
+    help="url to crawl",
 )
 GROUP.add_argument(
    "output",
    type=Path,
    metavar="OUTPUT",
-    help="output directory"
+    help="output directory",
 )


 def load(
-        args: argparse.Namespace,
-        parser: configparser.ConfigParser,
+    args: argparse.Namespace,
+    parser: configparser.ConfigParser,
 ) -> None:
    log.explain("Creating config for command 'kit-ipd'")

@@ -50,5 +55,11 @@ def load(
    if args.link_regex:
        section["link_regex"] = str(args.link_regex)

+    if args.basic_auth:
+        section["auth"] = "auth:kit-ipd"
+        parser["auth:kit-ipd"] = {}
+        auth_section = parser["auth:kit-ipd"]
+        auth_section["type"] = "simple"
+

 SUBPARSER.set_defaults(command=load)
--- a/PFERD/cli/command_local.py
+++ b/PFERD/cli/command_local.py
@@ -18,37 +18,37 @@ GROUP.add_argument(
    "target",
    type=Path,
    metavar="TARGET",
-    help="directory to crawl"
+    help="directory to crawl",
 )
 GROUP.add_argument(
    "output",
    type=Path,
    metavar="OUTPUT",
-    help="output directory"
+    help="output directory",
 )
 GROUP.add_argument(
    "--crawl-delay",
    type=float,
    metavar="SECONDS",
-    help="artificial delay to simulate for crawl requests"
+    help="artificial delay to simulate for crawl requests",
 )
 GROUP.add_argument(
    "--download-delay",
    type=float,
    metavar="SECONDS",
-    help="artificial delay to simulate for download requests"
+    help="artificial delay to simulate for download requests",
 )
 GROUP.add_argument(
    "--download-speed",
    type=int,
    metavar="BYTES_PER_SECOND",
-    help="download speed to simulate"
+    help="download speed to simulate",
 )


 def load(
-        args: argparse.Namespace,
-        parser: configparser.ConfigParser,
+    args: argparse.Namespace,
+    parser: configparser.ConfigParser,
 ) -> None:
    log.explain("Creating config for command 'local'")

--- a/PFERD/cli/common_ilias_args.py
+++ b/PFERD/cli/common_ilias_args.py
@@ -12,58 +12,60 @@ def configure_common_group_args(group: argparse._ArgumentGroup) -> None:
        "target",
        type=str,
        metavar="TARGET",
-        help="course id, 'desktop', or ILIAS URL to crawl"
+        help="course id, 'desktop', or ILIAS URL to crawl",
    )
    group.add_argument(
        "output",
        type=Path,
        metavar="OUTPUT",
-        help="output directory"
+        help="output directory",
    )
    group.add_argument(
-        "--username", "-u",
+        "--username",
+        "-u",
        type=str,
        metavar="USERNAME",
-        help="user name for authentication"
+        help="user name for authentication",
    )
    group.add_argument(
        "--keyring",
        action=BooleanOptionalAction,
-        help="use the system keyring to store and retrieve passwords"
+        help="use the system keyring to store and retrieve passwords",
    )
    group.add_argument(
        "--credential-file",
        type=Path,
        metavar="PATH",
-        help="read username and password from a credential file"
+        help="read username and password from a credential file",
    )
    group.add_argument(
        "--links",
        type=show_value_error(Links.from_string),
        metavar="OPTION",
-        help="how to represent external links"
+        help="how to represent external links",
    )
    group.add_argument(
        "--link-redirect-delay",
        type=int,
        metavar="SECONDS",
-        help="time before 'fancy' links redirect to to their target (-1 to disable)"
+        help="time before 'fancy' links redirect to to their target (-1 to disable)",
    )
    group.add_argument(
        "--videos",
        action=BooleanOptionalAction,
-        help="crawl and download videos"
+        help="crawl and download videos",
    )
    group.add_argument(
        "--forums",
        action=BooleanOptionalAction,
-        help="crawl and download forum posts"
+        help="crawl and download forum posts",
    )
    group.add_argument(
-        "--http-timeout", "-t",
+        "--http-timeout",
+        "-t",
        type=float,
        metavar="SECONDS",
-        help="timeout for all HTTP requests"
+        help="timeout for all HTTP requests",
    )


--- a/PFERD/cli/parser.py
+++ b/PFERD/cli/parser.py
@@ -1,8 +1,9 @@
 import argparse
 import configparser
 from argparse import ArgumentTypeError
+from collections.abc import Callable, Sequence
 from pathlib import Path
-from typing import Any, Callable, List, Optional, Sequence, Union
+from typing import Any, Optional

 from ..output_dir import OnConflict, Redownload
 from ..version import NAME, VERSION
@@ -15,15 +16,15 @@ class ParserLoadError(Exception):
 # TODO Replace with argparse version when updating to 3.9?
 class BooleanOptionalAction(argparse.Action):
    def __init__(
-            self,
-            option_strings: List[str],
-            dest: Any,
-            default: Any = None,
-            type: Any = None,
-            choices: Any = None,
-            required: Any = False,
-            help: Any = None,
-            metavar: Any = None,
+        self,
+        option_strings: list[str],
+        dest: Any,
+        default: Any = None,
+        type: Any = None,
+        choices: Any = None,
+        required: Any = False,
+        help: Any = None,
+        metavar: Any = None,
    ):
        if len(option_strings) != 1:
            raise ValueError("There must be exactly one option string")
@@ -48,11 +49,11 @@ class BooleanOptionalAction(argparse.Action):
        )

    def __call__(
-            self,
-            parser: argparse.ArgumentParser,
-            namespace: argparse.Namespace,
-            values: Union[str, Sequence[Any], None],
-            option_string: Optional[str] = None,
+        self,
+        parser: argparse.ArgumentParser,
+        namespace: argparse.Namespace,
+        values: str | Sequence[Any] | None,
+        option_string: Optional[str] = None,
    ) -> None:
        if option_string and option_string in self.option_strings:
            value = not option_string.startswith("--no-")
@@ -67,11 +68,13 @@ def show_value_error(inner: Callable[[str], Any]) -> Callable[[str], Any]:
    Some validation functions (like the from_string in our enums) raise a ValueError.
    Argparse only pretty-prints ArgumentTypeErrors though, so we need to wrap our ValueErrors.
    """
+
    def wrapper(input: str) -> Any:
        try:
            return inner(input)
        except ValueError as e:
-            raise ArgumentTypeError(e)
+            raise ArgumentTypeError(e) from e
+
    return wrapper


@@ -81,52 +84,57 @@ CRAWLER_PARSER_GROUP = CRAWLER_PARSER.add_argument_group(
    description="arguments common to all crawlers",
 )
 CRAWLER_PARSER_GROUP.add_argument(
-    "--redownload", "-r",
+    "--redownload",
+    "-r",
    type=show_value_error(Redownload.from_string),
    metavar="OPTION",
-    help="when to download a file that's already present locally"
+    help="when to download a file that's already present locally",
 )
 CRAWLER_PARSER_GROUP.add_argument(
    "--on-conflict",
    type=show_value_error(OnConflict.from_string),
    metavar="OPTION",
-    help="what to do when local and remote files or directories differ"
+    help="what to do when local and remote files or directories differ",
 )
 CRAWLER_PARSER_GROUP.add_argument(
-    "--transform", "-T",
+    "--transform",
+    "-T",
    action="append",
    type=str,
    metavar="RULE",
-    help="add a single transformation rule. Can be specified multiple times"
+    help="add a single transformation rule. Can be specified multiple times",
 )
 CRAWLER_PARSER_GROUP.add_argument(
-    "--tasks", "-n",
+    "--tasks",
+    "-n",
    type=int,
    metavar="N",
-    help="maximum number of concurrent tasks (crawling, downloading)"
+    help="maximum number of concurrent tasks (crawling, downloading)",
 )
 CRAWLER_PARSER_GROUP.add_argument(
-    "--downloads", "-N",
+    "--downloads",
+    "-N",
    type=int,
    metavar="N",
-    help="maximum number of tasks that may download data at the same time"
+    help="maximum number of tasks that may download data at the same time",
 )
 CRAWLER_PARSER_GROUP.add_argument(
-    "--task-delay", "-d",
+    "--task-delay",
+    "-d",
    type=float,
    metavar="SECONDS",
-    help="time the crawler should wait between subsequent tasks"
+    help="time the crawler should wait between subsequent tasks",
 )
 CRAWLER_PARSER_GROUP.add_argument(
    "--windows-paths",
    action=BooleanOptionalAction,
-    help="whether to repair invalid paths on windows"
+    help="whether to repair invalid paths on windows",
 )


 def load_crawler(
-        args: argparse.Namespace,
-        section: configparser.SectionProxy,
+    args: argparse.Namespace,
+    section: configparser.SectionProxy,
 ) -> None:
    if args.redownload is not None:
        section["redownload"] = args.redownload.value
@@ -152,79 +160,79 @@ PARSER.add_argument(
    version=f"{NAME} {VERSION} (https://github.com/Garmelon/PFERD)",
 )
 PARSER.add_argument(
-    "--config", "-c",
+    "--config",
+    "-c",
    type=Path,
    metavar="PATH",
-    help="custom config file"
+    help="custom config file",
 )
 PARSER.add_argument(
    "--dump-config",
    action="store_true",
-    help="dump current configuration to the default config path and exit"
+    help="dump current configuration to the default config path and exit",
 )
 PARSER.add_argument(
    "--dump-config-to",
    metavar="PATH",
-    help="dump current configuration to a file and exit."
-    " Use '-' as path to print to stdout instead"
+    help="dump current configuration to a file and exit. Use '-' as path to print to stdout instead",
 )
 PARSER.add_argument(
    "--debug-transforms",
    action="store_true",
-    help="apply transform rules to files of previous run"
+    help="apply transform rules to files of previous run",
 )
 PARSER.add_argument(
-    "--crawler", "-C",
+    "--crawler",
+    "-C",
    action="append",
    type=str,
    metavar="NAME",
-    help="only execute a single crawler."
-    " Can be specified multiple times to execute multiple crawlers"
+    help="only execute a single crawler. Can be specified multiple times to execute multiple crawlers",
 )
 PARSER.add_argument(
-    "--skip", "-S",
+    "--skip",
+    "-S",
    action="append",
    type=str,
    metavar="NAME",
-    help="don't execute this particular crawler."
-    " Can be specified multiple times to skip multiple crawlers"
+    help="don't execute this particular crawler. Can be specified multiple times to skip multiple crawlers",
 )
 PARSER.add_argument(
    "--working-dir",
    type=Path,
    metavar="PATH",
-    help="custom working directory"
+    help="custom working directory",
 )
 PARSER.add_argument(
    "--explain",
    action=BooleanOptionalAction,
-    help="log and explain in detail what PFERD is doing"
+    help="log and explain in detail what PFERD is doing",
 )
 PARSER.add_argument(
    "--status",
    action=BooleanOptionalAction,
-    help="print status updates while PFERD is crawling"
+    help="print status updates while PFERD is crawling",
 )
 PARSER.add_argument(
    "--report",
    action=BooleanOptionalAction,
-    help="print a report of all local changes before exiting"
+    help="print a report of all local changes before exiting",
 )
 PARSER.add_argument(
    "--share-cookies",
    action=BooleanOptionalAction,
-    help="whether crawlers should share cookies where applicable"
+    help="whether crawlers should share cookies where applicable",
 )
 PARSER.add_argument(
    "--show-not-deleted",
    action=BooleanOptionalAction,
-    help="print messages in status and report when PFERD did not delete a local only file"
+    help="print messages in status and report when PFERD did not delete a local only file",
 )


 def load_default_section(
-        args: argparse.Namespace,
-        parser: configparser.ConfigParser,
+    args: argparse.Namespace,
+    parser: configparser.ConfigParser,
 ) -> None:
    section = parser[parser.default_section]

--- a/PFERD/config.py
+++ b/PFERD/config.py
@@ -3,7 +3,7 @@ import os
 import sys
 from configparser import ConfigParser, SectionProxy
 from pathlib import Path
-from typing import Any, List, NoReturn, Optional, Tuple
+from typing import Any, NoReturn, Optional

 from rich.markup import escape

@@ -53,10 +53,10 @@ class Section:
        raise ConfigOptionError(self.s.name, key, desc)

    def invalid_value(
-            self,
-            key: str,
-            value: Any,
-            reason: Optional[str],
+        self,
+        key: str,
+        value: Any,
+        reason: Optional[str],
    ) -> NoReturn:
        if reason is None:
            self.error(key, f"Invalid value {value!r}")
@@ -126,13 +126,13 @@ class Config:
            with open(path, encoding="utf-8") as f:
                parser.read_file(f, source=str(path))
        except FileNotFoundError:
-            raise ConfigLoadError(path, "File does not exist")
+            raise ConfigLoadError(path, "File does not exist") from None
        except IsADirectoryError:
-            raise ConfigLoadError(path, "That's a directory, not a file")
+            raise ConfigLoadError(path, "That's a directory, not a file") from None
        except PermissionError:
-            raise ConfigLoadError(path, "Insufficient permissions")
+            raise ConfigLoadError(path, "Insufficient permissions") from None
        except UnicodeDecodeError:
-            raise ConfigLoadError(path, "File is not encoded using UTF-8")
+            raise ConfigLoadError(path, "File is not encoded using UTF-8") from None

    def dump(self, path: Optional[Path] = None) -> None:
        """
@@ -150,8 +150,8 @@ class Config:

        try:
            path.parent.mkdir(parents=True, exist_ok=True)
-        except PermissionError:
-            raise ConfigDumpError(path, "Could not create parent directory")
+        except PermissionError as e:
+            raise ConfigDumpError(path, "Could not create parent directory") from e

        try:
            # Ensuring we don't accidentally overwrite any existing files by
@@ -167,16 +167,16 @@ class Config:
                    with open(path, "w", encoding="utf-8") as f:
                        self._parser.write(f)
                else:
-                    raise ConfigDumpError(path, "File already exists")
+                    raise ConfigDumpError(path, "File already exists") from None
        except IsADirectoryError:
-            raise ConfigDumpError(path, "That's a directory, not a file")
-        except PermissionError:
-            raise ConfigDumpError(path, "Insufficient permissions")
+            raise ConfigDumpError(path, "That's a directory, not a file") from None
+        except PermissionError as e:
+            raise ConfigDumpError(path, "Insufficient permissions") from e

    def dump_to_stdout(self) -> None:
        self._parser.write(sys.stdout)

-    def crawl_sections(self) -> List[Tuple[str, SectionProxy]]:
+    def crawl_sections(self) -> list[tuple[str, SectionProxy]]:
        result = []
        for name, proxy in self._parser.items():
            if name.startswith("crawl:"):
@@ -184,7 +184,7 @@ class Config:

        return result

-    def auth_sections(self) -> List[Tuple[str, SectionProxy]]:
+    def auth_sections(self) -> list[tuple[str, SectionProxy]]:
        result = []
        for name, proxy in self._parser.items():
            if name.startswith("auth:"):
--- a/PFERD/crawl/init.py
+++ b/PFERD/crawl/init.py
@@ -1,5 +1,5 @@
+from collections.abc import Callable
 from configparser import SectionProxy
-from typing import Callable, Dict

 from ..auth import Authenticator
 from ..config import Config
@@ -8,20 +8,19 @@ from .ilias import IliasWebCrawler, IliasWebCrawlerSection, KitIliasWebCrawler,
 from .kit_ipd_crawler import KitIpdCrawler, KitIpdCrawlerSection
 from .local_crawler import LocalCrawler, LocalCrawlerSection

-CrawlerConstructor = Callable[[
-    str,                       # Name (without the "crawl:" prefix)
-    SectionProxy,              # Crawler's section of global config
-    Config,                    # Global config
-    Dict[str, Authenticator],  # Loaded authenticators by name
-], Crawler]
+CrawlerConstructor = Callable[
+    [
+        str,  # Name (without the "crawl:" prefix)
+        SectionProxy,  # Crawler's section of global config
+        Config,  # Global config
+        dict[str, Authenticator],  # Loaded authenticators by name
+    ],
+    Crawler,
+]

-CRAWLERS: Dict[str, CrawlerConstructor] = {
-    "local": lambda n, s, c, a:
-        LocalCrawler(n, LocalCrawlerSection(s), c),
-    "ilias-web": lambda n, s, c, a:
-        IliasWebCrawler(n, IliasWebCrawlerSection(s), c, a),
-    "kit-ilias-web": lambda n, s, c, a:
-        KitIliasWebCrawler(n, KitIliasWebCrawlerSection(s), c, a),
-    "kit-ipd": lambda n, s, c, a:
-        KitIpdCrawler(n, KitIpdCrawlerSection(s), c),
+CRAWLERS: dict[str, CrawlerConstructor] = {
+    "local": lambda n, s, c, a: LocalCrawler(n, LocalCrawlerSection(s), c),
+    "ilias-web": lambda n, s, c, a: IliasWebCrawler(n, IliasWebCrawlerSection(s), c, a),
+    "kit-ilias-web": lambda n, s, c, a: KitIliasWebCrawler(n, KitIliasWebCrawlerSection(s), c, a),
+    "kit-ipd": lambda n, s, c, a: KitIpdCrawler(n, KitIpdCrawlerSection(s), c, a),
 }
--- a/PFERD/crawl/crawler.py
+++ b/PFERD/crawl/crawler.py
@@ -1,10 +1,10 @@
 import asyncio
 import os
 from abc import ABC, abstractmethod
-from collections.abc import Awaitable, Coroutine
+from collections.abc import Awaitable, Callable, Coroutine, Sequence
 from datetime import datetime
 from pathlib import Path, PurePath
-from typing import Any, Callable, Dict, List, Optional, Sequence, Set, Tuple, TypeVar
+from typing import Any, Optional, TypeVar

 from ..auth import Authenticator
 from ..config import Config, Section
@@ -116,7 +116,7 @@ class CrawlToken(ReusableAsyncContextManager[ProgressBar]):
        return bar


-class DownloadToken(ReusableAsyncContextManager[Tuple[ProgressBar, FileSink]]):
+class DownloadToken(ReusableAsyncContextManager[tuple[ProgressBar, FileSink]]):
    def __init__(self, limiter: Limiter, fs_token: FileSinkToken, path: PurePath):
        super().__init__()

@@ -128,12 +128,13 @@ class DownloadToken(ReusableAsyncContextManager[Tuple[ProgressBar, FileSink]]):
    def path(self) -> PurePath:
        return self._path

-    async def _on_aenter(self) -> Tuple[ProgressBar, FileSink]:
+    async def _on_aenter(self) -> tuple[ProgressBar, FileSink]:
        await self._stack.enter_async_context(self._limiter.limit_download())
        sink = await self._stack.enter_async_context(self._fs_token)
        # The "Downloaded ..." message is printed in the output dir, not here
-        bar = self._stack.enter_context(log.download_bar("[bold bright_cyan]", "Downloading",
-                                                         fmt_path(self._path)))
+        bar = self._stack.enter_context(
+            log.download_bar("[bold bright_cyan]", "Downloading", fmt_path(self._path))
+        )

        return bar, sink

@@ -149,9 +150,7 @@ class CrawlerSection(Section):
        return self.s.getboolean("skip", fallback=False)

    def output_dir(self, name: str) -> Path:
-        # TODO Use removeprefix() after switching to 3.9
-        if name.startswith("crawl:"):
-            name = name[len("crawl:"):]
+        name = name.removeprefix("crawl:")
        return Path(self.s.get("output_dir", name)).expanduser()

    def redownload(self) -> Redownload:
@@ -206,7 +205,7 @@ class CrawlerSection(Section):
        on_windows = os.name == "nt"
        return self.s.getboolean("windows_paths", fallback=on_windows)

-    def auth(self, authenticators: Dict[str, Authenticator]) -> Authenticator:
+    def auth(self, authenticators: dict[str, Authenticator]) -> Authenticator:
        value = self.s.get("auth")
        if value is None:
            self.missing_value("auth")
@@ -218,10 +217,10 @@ class CrawlerSection(Section):

 class Crawler(ABC):
    def __init__(
-            self,
-            name: str,
-            section: CrawlerSection,
-            config: Config,
+        self,
+        name: str,
+        section: CrawlerSection,
+        config: Config,
    ) -> None:
        """
        Initialize a crawler from its name and its section in the config file.
@@ -258,8 +257,12 @@ class Crawler(ABC):
    def prev_report(self) -> Optional[Report]:
        return self._output_dir.prev_report

+    @property
+    def output_dir(self) -> OutputDirectory:
+        return self._output_dir
+
    @staticmethod
-    async def gather(awaitables: Sequence[Awaitable[Any]]) -> List[Any]:
+    async def gather(awaitables: Sequence[Awaitable[Any]]) -> list[Any]:
        """
        Similar to asyncio.gather. However, in the case of an exception, all
        still running tasks are cancelled and the exception is rethrown.
@@ -290,12 +293,39 @@ class Crawler(ABC):
        log.explain("Answer: Yes")
        return CrawlToken(self._limiter, path)

+    def should_try_download(
+        self,
+        path: PurePath,
+        *,
+        etag_differs: Optional[bool] = None,
+        mtime: Optional[datetime] = None,
+        redownload: Optional[Redownload] = None,
+        on_conflict: Optional[OnConflict] = None,
+    ) -> bool:
+        log.explain_topic(f"Decision: Should Download {fmt_path(path)}")
+
+        if self._transformer.transform(path) is None:
+            log.explain("Answer: No (ignored)")
+            return False
+
+        should_download = self._output_dir.should_try_download(
+            path, etag_differs=etag_differs, mtime=mtime, redownload=redownload, on_conflict=on_conflict
+        )
+        if should_download:
+            log.explain("Answer: Yes")
+            return True
+        else:
+            log.explain("Answer: No")
+            return False
+
    async def download(
-            self,
-            path: PurePath,
-            mtime: Optional[datetime] = None,
-            redownload: Optional[Redownload] = None,
-            on_conflict: Optional[OnConflict] = None,
+        self,
+        path: PurePath,
+        *,
+        etag_differs: Optional[bool] = None,
+        mtime: Optional[datetime] = None,
+        redownload: Optional[Redownload] = None,
+        on_conflict: Optional[OnConflict] = None,
    ) -> Optional[DownloadToken]:
        log.explain_topic(f"Decision: Download {fmt_path(path)}")
        path = self._deduplicator.mark(path)
@@ -307,7 +337,14 @@ class Crawler(ABC):
            log.status("[bold bright_black]", "Ignored", fmt_path(path))
            return None

-        fs_token = await self._output_dir.download(path, transformed_path, mtime, redownload, on_conflict)
+        fs_token = await self._output_dir.download(
+            path,
+            transformed_path,
+            etag_differs=etag_differs,
+            mtime=mtime,
+            redownload=redownload,
+            on_conflict=on_conflict,
+        )
        if fs_token is None:
            log.explain("Answer: No")
            return None
@@ -357,7 +394,7 @@ class Crawler(ABC):
            log.warn("Couldn't find or load old report")
            return

-        seen: Set[PurePath] = set()
+        seen: set[PurePath] = set()
        for known in sorted(self.prev_report.found_paths):
            looking_at = list(reversed(known.parents)) + [known]
            for path in looking_at:
--- a/PFERD/crawl/http_crawler.py
+++ b/PFERD/crawl/http_crawler.py
@@ -1,35 +1,39 @@
 import asyncio
 import http.cookies
 import ssl
+from datetime import datetime
 from pathlib import Path, PurePath
-from typing import Any, Dict, List, Optional
+from typing import Any, Optional

 import aiohttp
 import certifi
 from aiohttp.client import ClientTimeout
+from bs4 import Tag

 from ..auth import Authenticator
 from ..config import Config
 from ..logging import log
-from ..utils import fmt_real_path
+from ..utils import fmt_real_path, sanitize_path_name
 from ..version import NAME, VERSION
 from .crawler import Crawler, CrawlerSection

+ETAGS_CUSTOM_REPORT_VALUE_KEY = "etags"
+

 class HttpCrawlerSection(CrawlerSection):
    def http_timeout(self) -> float:
-        return self.s.getfloat("http_timeout", fallback=20)
+        return self.s.getfloat("http_timeout", fallback=30)


 class HttpCrawler(Crawler):
    COOKIE_FILE = PurePath(".cookies")

    def __init__(
-            self,
-            name: str,
-            section: HttpCrawlerSection,
-            config: Config,
-            shared_auth: Optional[Authenticator] = None,
+        self,
+        name: str,
+        section: HttpCrawlerSection,
+        config: Config,
+        shared_auth: Optional[Authenticator] = None,
    ) -> None:
        super().__init__(name, section, config)

@@ -39,7 +43,7 @@ class HttpCrawler(Crawler):
        self._http_timeout = section.http_timeout()

        self._cookie_jar_path = self._output_dir.resolve(self.COOKIE_FILE)
-        self._shared_cookie_jar_paths: Optional[List[Path]] = None
+        self._shared_cookie_jar_paths: Optional[list[Path]] = None
        self._shared_auth = shared_auth

        self._output_dir.register_reserved(self.COOKIE_FILE)
@@ -94,7 +98,7 @@ class HttpCrawler(Crawler):
        """
        raise RuntimeError("_authenticate() was called but crawler doesn't provide an implementation")

-    def share_cookies(self, shared: Dict[Authenticator, List[Path]]) -> None:
+    def share_cookies(self, shared: dict[Authenticator, list[Path]]) -> None:
        if not self._shared_auth:
            return

@@ -169,24 +173,102 @@ class HttpCrawler(Crawler):
            log.warn(f"Failed to save cookies to {fmt_real_path(self._cookie_jar_path)}")
            log.warn(str(e))

+    @staticmethod
+    def get_folder_structure_from_heading_hierarchy(file_link: Tag, drop_h1: bool = False) -> PurePath:
+        """
+        Retrieves the hierarchy of headings associated with the give file link and constructs a folder
+        structure from them.
+
+        <h1> level headings usually only appear once and serve as the page title, so they would introduce
+        redundant nesting. To avoid this, <h1> headings are ignored via the drop_h1 parameter.
+        """
+
+        def find_associated_headings(tag: Tag, level: int) -> PurePath:
+            if level == 0 or (level == 1 and drop_h1):
+                return PurePath()
+
+            level_heading = tag.find_previous(name=f"h{level}")
+
+            if level_heading is None:
+                return find_associated_headings(tag, level - 1)
+
+            folder_name = sanitize_path_name(level_heading.get_text().strip())
+            return find_associated_headings(level_heading, level - 1) / folder_name
+
+        # start at level <h3> because paragraph-level headings are usually too granular for folder names
+        return find_associated_headings(file_link, 3)
+
+    def _get_previous_etag_from_report(self, path: PurePath) -> Optional[str]:
+        """
+        If available, retrieves the entity tag for a given path which was stored in the previous report.
+        """
+        if not self._output_dir.prev_report:
+            return None
+
+        etags = self._output_dir.prev_report.get_custom_value(ETAGS_CUSTOM_REPORT_VALUE_KEY) or {}
+        return etags.get(str(path))
+
+    def _add_etag_to_report(self, path: PurePath, etag: Optional[str]) -> None:
+        """
+        Adds an entity tag for a given path to the report's custom values.
+        """
+        if not etag:
+            return
+
+        etags = self._output_dir.report.get_custom_value(ETAGS_CUSTOM_REPORT_VALUE_KEY) or {}
+        etags[str(path)] = etag
+        self._output_dir.report.add_custom_value(ETAGS_CUSTOM_REPORT_VALUE_KEY, etags)
+
+    async def _request_resource_version(self, resource_url: str) -> tuple[Optional[str], Optional[datetime]]:
+        """
+        Requests the ETag and Last-Modified headers of a resource via a HEAD request.
+        If no entity tag / modification date can be obtained, the according value will be None.
+        """
+        try:
+            async with self.session.head(resource_url) as resp:
+                if resp.status != 200:
+                    return None, None
+
+                etag_header = resp.headers.get("ETag")
+                last_modified_header = resp.headers.get("Last-Modified")
+                last_modified = None
+
+                if last_modified_header:
+                    try:
+                        # https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Last-Modified#directives
+                        datetime_format = "%a, %d %b %Y %H:%M:%S GMT"
+                        last_modified = datetime.strptime(last_modified_header, datetime_format)
+                    except ValueError:
+                        # last_modified remains None
+                        pass
+
+                return etag_header, last_modified
+        except aiohttp.ClientError:
+            return None, None
+
    async def run(self) -> None:
        self._request_count = 0
        self._cookie_jar = aiohttp.CookieJar()
        self._load_cookies()

        async with aiohttp.ClientSession(
-                headers={"User-Agent": f"{NAME}/{VERSION}"},
-                cookie_jar=self._cookie_jar,
-                connector=aiohttp.TCPConnector(ssl=ssl.create_default_context(cafile=certifi.where())),
-                timeout=ClientTimeout(
-                    # 30 minutes. No download in the history of downloads was longer than 30 minutes.
-                    # This is enough to transfer a 600 MB file over a 3 Mib/s connection.
-                    # Allowing an arbitrary value could be annoying for overnight batch jobs
-                    total=15 * 60,
-                    connect=self._http_timeout,
-                    sock_connect=self._http_timeout,
-                    sock_read=self._http_timeout,
-                )
+            headers={"User-Agent": f"{NAME}/{VERSION}"},
+            cookie_jar=self._cookie_jar,
+            connector=aiohttp.TCPConnector(ssl=ssl.create_default_context(cafile=certifi.where())),
+            timeout=ClientTimeout(
+                # 30 minutes. No download in the history of downloads was longer than 30 minutes.
+                # This is enough to transfer a 600 MB file over a 3 Mib/s connection.
+                # Allowing an arbitrary value could be annoying for overnight batch jobs
+                total=15 * 60,
+                connect=self._http_timeout,
+                sock_connect=self._http_timeout,
+                sock_read=self._http_timeout,
+            ),
+            # See https://github.com/aio-libs/aiohttp/issues/6626
+            # Without this aiohttp will mangle the redirect header from Shibboleth, invalidating the
+            # passed signature. Shibboleth will not accept the broken signature and authentication will
+            # fail.
+            requote_redirect_url=False,
        ) as session:
            self.session = session
            try:
--- a/PFERD/crawl/ilias/init.py
+++ b/PFERD/crawl/ilias/init.py
@@ -1,5 +1,9 @@
-from .kit_ilias_web_crawler import (IliasWebCrawler, IliasWebCrawlerSection, KitIliasWebCrawler,
-                                    KitIliasWebCrawlerSection)
+from .kit_ilias_web_crawler import (
+    IliasWebCrawler,
+    IliasWebCrawlerSection,
+    KitIliasWebCrawler,
+    KitIliasWebCrawlerSection,
+)

 __all__ = [
    "IliasWebCrawler",
--- a/PFERD/crawl/ilias/async_helper.py
+++ b/PFERD/crawl/ilias/async_helper.py
@@ -1,5 +1,6 @@
 import asyncio
-from typing import Any, Callable, Optional
+from collections.abc import Callable
+from typing import Any, Optional

 import aiohttp

@@ -15,9 +16,9 @@ def _iorepeat(attempts: int, name: str, failure_is_error: bool = False) -> Calla
                try:
                    return await f(*args, **kwargs)
                except aiohttp.ContentTypeError:  # invalid content type
-                    raise CrawlWarning("ILIAS returned an invalid content type")
+                    raise CrawlWarning("ILIAS returned an invalid content type") from None
                except aiohttp.TooManyRedirects:
-                    raise CrawlWarning("Got stuck in a redirect loop")
+                    raise CrawlWarning("Got stuck in a redirect loop") from None
                except aiohttp.ClientPayloadError as e:  # encoding or not enough bytes
                    last_exception = e
                except aiohttp.ClientConnectionError as e:  # e.g. timeout, disconnect, resolve failed, etc.
@@ -25,9 +26,10 @@ def _iorepeat(attempts: int, name: str, failure_is_error: bool = False) -> Calla
                except asyncio.exceptions.TimeoutError as e:  # explicit http timeouts in HttpCrawler
                    last_exception = e
                log.explain_topic(f"Retrying operation {name}. Retries left: {attempts - 1 - round}")
+                log.explain(f"Last exception: {last_exception!r}")

            if last_exception:
-                message = f"Error in I/O Operation: {last_exception}"
+                message = f"Error in I/O Operation: {last_exception!r}"
                if failure_is_error:
                    raise CrawlError(message) from last_exception
                else:
--- a/PFERD/crawl/ilias/file_templates.py
+++ b/PFERD/crawl/ilias/file_templates.py
@@ -1,5 +1,7 @@
+import dataclasses
+import re
 from enum import Enum
-from typing import Optional
+from typing import Optional, cast

 import bs4

@@ -12,7 +14,9 @@ _link_template_fancy = """
    <head>
        <meta charset="UTF-8">
        <title>ILIAS - Link: {{name}}</title>
+        <!-- REPEAT REMOVE START -->
        <meta http-equiv = "refresh" content = "{{redirect_delay}}; url = {{link}}" />
+        <!-- REPEAT REMOVE END -->
    </head>

    <style>
@@ -23,6 +27,8 @@ _link_template_fancy = """
        display: flex;
        align-items: center;
        justify-content: center;
+        flex-direction: column;
+        gap: 4px;
    }
    body {
        padding: 0;
@@ -31,11 +37,16 @@ _link_template_fancy = """
        font-family: "Open Sans", Verdana, Arial, Helvetica, sans-serif;
        height: 100vh;
    }
-    .row {
-        background-color: white;
+    .column {
        min-width: 500px;
        max-width: 90vw;
        display: flex;
+        flex-direction: column;
+        row-gap: 5px;
+    }
+    .row {
+        background-color: white;
+        display: flex;
        padding: 1em;
    }
    .logo {
@@ -75,19 +86,23 @@ _link_template_fancy = """
    }
    </style>
    <body class="center-flex">
-        <div class="row">
-            <div class="logo center-flex">
-                <svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24">
-                    <path d="M12 0c-6.627 0-12 5.373-12 12s5.373 12 12 12 12-5.373 12-12-5.373-12-12-12zm9.567 9.098c-.059-.058-.127-.108-.206-.138-.258-.101-1.35.603-1.515.256-.108-.231-.327.148-.578.008-.121-.067-.459-.52-.611-.465-.312.112.479.974.694 1.087.203-.154.86-.469 1.002-.039.271.812-.745 1.702-1.264 2.171-.775.702-.63-.454-1.159-.86-.277-.213-.274-.667-.555-.824-.125-.071-.7-.732-.694-.821l-.017.167c-.095.072-.297-.27-.319-.325 0 .298.485.772.646 1.011.273.409.42 1.005.756 1.339.179.18.866.923 1.045.908l.921-.437c.649.154-1.531 3.237-1.738 3.619-.171.321.139 1.112.114 1.49-.029.437-.374.579-.7.817-.35.255-.268.752-.562.934-.521.321-.897 1.366-1.639 1.361-.219-.001-1.151.364-1.273.007-.095-.258-.223-.455-.356-.71-.131-.25-.015-.51-.175-.731-.11-.154-.479-.502-.513-.684-.002-.157.118-.632.283-.715.231-.118.044-.462.016-.663-.048-.357-.27-.652-.535-.859-.393-.302-.189-.542-.098-.974 0-.206-.126-.476-.402-.396-.57.166-.396-.445-.812-.417-.299.021-.543.211-.821.295-.349.104-.707-.083-1.053-.126-1.421-.179-1.885-1.804-1.514-2.976.037-.192-.115-.547-.048-.696.159-.352.485-.752.768-1.021.16-.152.365-.113.553-.231.29-.182.294-.558.578-.789.404-.328.956-.321 1.482-.392.281-.037 1.35-.268 1.518-.06 0 .039.193.611-.019.578.438.023 1.061.756 1.476.585.213-.089.135-.744.573-.427.265.19 1.45.275 1.696.07.152-.125.236-.939.053-1.031.117.116-.618.125-.686.099-.122-.044-.235.115-.43.025.117.055-.651-.358-.22-.674-.181.132-.349-.037-.544.109-.135.109.062.181-.13.277-.305.155-.535-.53-.649-.607-.118-.077-1.024-.713-.777-.298l.797.793c-.04.026-.209-.289-.209-.059.053-.136.02.585-.105.35-.056-.09.091-.14.006-.271 0-.085-.23-.169-.275-.228-.126-.157-.462-.502-.644-.585-.05-.024-.771.088-.832.111-.071.099-.131.203-.181.314-.149.055-.29.127-.423.216l-.159.356c-.068.061-.772.294-.776.303.03-.076-.492-.172-.457-.324.038-.167.215-.687.169-.877-.048-.199 1.085.287 1.158-.238.029-.227.047-.492-.316-.531.069.008.702-.249.807-.364.148-.169.486-.447.731-.447.286 0 .225-.417.356-.622.133.053-.071.38.088.512-.01-.104.45.057.494.033.105-.056.691-.023.601-.299-.101-.28.052-.197.183-.255-.02.008.248-.458.363-.456-.104-.089-.398.112-.516.103-.308-.024-.177-.525-.061-.672.09-.116-.246-.258-.25-.036-.006.332-.314.633-.243 1.075.109.666-.743-.161-.816-.115-.283.172-.515-.216-.368-.449.149-.238.51-.226.659-.48.104-.179.227-.389.388-.524.541-.454.689-.091 1.229-.042.526.048.178.125.105.327-.07.192.289.261.413.1.071-.092.232-.326.301-.499.07-.175.578-.2.527-.365 2.72 1.148 4.827 3.465 5.694 6.318zm-11.113-3.779l.068-.087.073-.019c.042-.034.086-.118.151-.104.043.009.146.095.111.148-.037.054-.066-.049-.081.101-.018.169-.188.167-.313.222-.087.037-.175-.018-.09-.104l.088-.108-.007-.049zm.442.245c.046-.045.138-.008.151-.094.014-.084.078-.178-.008-.335-.022-.042.116-.082.051-.137l-.109.032s.155-.668.364-.366l-.089.103c.135.134.172.47.215.687.127.066.324.078.098.192.117-.02-.618.314-.715.178-.072-.083.317-.139.307-.173-.004-.011-.317-.02-.265-.087zm1.43-3.547l-.356.326c-.36.298-1.28.883-1.793.705-.524-.18-1.647.667-1.826.673-.067.003.002-.641.36-.689-.141.021.993-.575 1.185-.805.678-.146 1.381-.227 2.104-.227l.326.017zm-5.086 1.19c.07.082.278.092-.026.288-.183.11-.377.809-.548.809-.51.223-.542-.439-1.109.413-.078.115-.395.158-.644.236.685-.688 1.468-1.279 2.327-1.746zm-5.24 8.793c0-.541.055-1.068.139-1.586l.292.185c.113.135.113.719.169.911.139.482.484.751.748 1.19.155.261.414.923.332 1.197.109-.179 1.081.824 1.259 1.033.418.492.74 1.088.061 1.574-.219.158.334 1.14.049 1.382l-.365.094c-.225.138-.235.397-.166.631-1.562-1.765-2.518-4.076-2.518-6.611zm14.347-5.823c.083-.01-.107.167-.107.167.033.256.222.396.581.527.437.157.038.455-.213.385-.139-.039-.854-.255-.879.025 0 .167-.679.001-.573-.175.073-.119.05-.387.186-.562.193-.255.38-.116.386.032-.001.394.398-.373.619-.399z"/>
-                </svg>
-            </div>
-            <div class="tile">
-                <div class="top-row">
-                    <a href="{{link}}">{{name}}</a>
+        <div class="column">
+        <!-- REPEAT START -->
+            <div class="row">
+                <div class="logo center-flex">
+                    <svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24">
+                        <path d="M12 0c-6.627 0-12 5.373-12 12s5.373 12 12 12 12-5.373 12-12-5.373-12-12-12zm9.567 9.098c-.059-.058-.127-.108-.206-.138-.258-.101-1.35.603-1.515.256-.108-.231-.327.148-.578.008-.121-.067-.459-.52-.611-.465-.312.112.479.974.694 1.087.203-.154.86-.469 1.002-.039.271.812-.745 1.702-1.264 2.171-.775.702-.63-.454-1.159-.86-.277-.213-.274-.667-.555-.824-.125-.071-.7-.732-.694-.821l-.017.167c-.095.072-.297-.27-.319-.325 0 .298.485.772.646 1.011.273.409.42 1.005.756 1.339.179.18.866.923 1.045.908l.921-.437c.649.154-1.531 3.237-1.738 3.619-.171.321.139 1.112.114 1.49-.029.437-.374.579-.7.817-.35.255-.268.752-.562.934-.521.321-.897 1.366-1.639 1.361-.219-.001-1.151.364-1.273.007-.095-.258-.223-.455-.356-.71-.131-.25-.015-.51-.175-.731-.11-.154-.479-.502-.513-.684-.002-.157.118-.632.283-.715.231-.118.044-.462.016-.663-.048-.357-.27-.652-.535-.859-.393-.302-.189-.542-.098-.974 0-.206-.126-.476-.402-.396-.57.166-.396-.445-.812-.417-.299.021-.543.211-.821.295-.349.104-.707-.083-1.053-.126-1.421-.179-1.885-1.804-1.514-2.976.037-.192-.115-.547-.048-.696.159-.352.485-.752.768-1.021.16-.152.365-.113.553-.231.29-.182.294-.558.578-.789.404-.328.956-.321 1.482-.392.281-.037 1.35-.268 1.518-.06 0 .039.193.611-.019.578.438.023 1.061.756 1.476.585.213-.089.135-.744.573-.427.265.19 1.45.275 1.696.07.152-.125.236-.939.053-1.031.117.116-.618.125-.686.099-.122-.044-.235.115-.43.025.117.055-.651-.358-.22-.674-.181.132-.349-.037-.544.109-.135.109.062.181-.13.277-.305.155-.535-.53-.649-.607-.118-.077-1.024-.713-.777-.298l.797.793c-.04.026-.209-.289-.209-.059.053-.136.02.585-.105.35-.056-.09.091-.14.006-.271 0-.085-.23-.169-.275-.228-.126-.157-.462-.502-.644-.585-.05-.024-.771.088-.832.111-.071.099-.131.203-.181.314-.149.055-.29.127-.423.216l-.159.356c-.068.061-.772.294-.776.303.03-.076-.492-.172-.457-.324.038-.167.215-.687.169-.877-.048-.199 1.085.287 1.158-.238.029-.227.047-.492-.316-.531.069.008.702-.249.807-.364.148-.169.486-.447.731-.447.286 0 .225-.417.356-.622.133.053-.071.38.088.512-.01-.104.45.057.494.033.105-.056.691-.023.601-.299-.101-.28.052-.197.183-.255-.02.008.248-.458.363-.456-.104-.089-.398.112-.516.103-.308-.024-.177-.525-.061-.672.09-.116-.246-.258-.25-.036-.006.332-.314.633-.243 1.075.109.666-.743-.161-.816-.115-.283.172-.515-.216-.368-.449.149-.238.51-.226.659-.48.104-.179.227-.389.388-.524.541-.454.689-.091 1.229-.042.526.048.178.125.105.327-.07.192.289.261.413.1.071-.092.232-.326.301-.499.07-.175.578-.2.527-.365 2.72 1.148 4.827 3.465 5.694 6.318zm-11.113-3.779l.068-.087.073-.019c.042-.034.086-.118.151-.104.043.009.146.095.111.148-.037.054-.066-.049-.081.101-.018.169-.188.167-.313.222-.087.037-.175-.018-.09-.104l.088-.108-.007-.049zm.442.245c.046-.045.138-.008.151-.094.014-.084.078-.178-.008-.335-.022-.042.116-.082.051-.137l-.109.032s.155-.668.364-.366l-.089.103c.135.134.172.47.215.687.127.066.324.078.098.192.117-.02-.618.314-.715.178-.072-.083.317-.139.307-.173-.004-.011-.317-.02-.265-.087zm1.43-3.547l-.356.326c-.36.298-1.28.883-1.793.705-.524-.18-1.647.667-1.826.673-.067.003.002-.641.36-.689-.141.021.993-.575 1.185-.805.678-.146 1.381-.227 2.104-.227l.326.017zm-5.086 1.19c.07.082.278.092-.026.288-.183.11-.377.809-.548.809-.51.223-.542-.439-1.109.413-.078.115-.395.158-.644.236.685-.688 1.468-1.279 2.327-1.746zm-5.24 8.793c0-.541.055-1.068.139-1.586l.292.185c.113.135.113.719.169.911.139.482.484.751.748 1.19.155.261.414.923.332 1.197.109-.179 1.081.824 1.259 1.033.418.492.74 1.088.061 1.574-.219.158.334 1.14.049 1.382l-.365.094c-.225.138-.235.397-.166.631-1.562-1.765-2.518-4.076-2.518-6.611zm14.347-5.823c.083-.01-.107.167-.107.167.033.256.222.396.581.527.437.157.038.455-.213.385-.139-.039-.854-.255-.879.025 0 .167-.679.001-.573-.175.073-.119.05-.387.186-.562.193-.255.38-.116.386.032-.001.394.398-.373.619-.399z"/>
+                    </svg>
                </div>
-                <div class="bottom-row">{{description}}</div>
+                <div class="tile">
+                    <div class="top-row">
+                        <a href="{{link}}">{{name}}</a>
+                    </div>
+                    <div class="bottom-row">{{description}}</div>
+                </div>
+                <div class="menu-button center-flex"> ⯆ </div>
            </div>
-            <div class="menu-button center-flex"> ⯆ </div>
+        <!-- REPEAT END -->
        </div>
    </body>
 </html>
@@ -96,6 +111,7 @@ _link_template_fancy = """
 _link_template_internet_shortcut = """
 [InternetShortcut]
 URL={{link}}
+Desc={{description}}
 """.strip()

 _learning_module_template = """
@@ -126,6 +142,88 @@ _learning_module_template = """
 </html>
 """

+_forum_thread_template = """
+<!DOCTYPE html>
+<html lang="en">
+    <head>
+        <meta charset="UTF-8">
+        <title>ILIAS - Forum: {{name}}</title>
+        <style>
+            * {
+                box-sizing: border-box;
+            }
+            body {
+                font-family: 'Open Sans', Verdana, Arial, Helvetica, sans-serif;
+                padding: 8px;
+            }
+            ul, ol, p {
+                margin: 1.2em 0;
+            }
+            p {
+                margin-top: 8px;
+                margin-bottom: 8px;
+            }
+            a {
+                color: #00876c;
+                text-decoration: none;
+                cursor: pointer;
+            }
+            a:hover {
+                text-decoration: underline;
+            }
+            body > p:first-child > span:first-child {
+                font-size: 1.6em;
+            }
+            body > p:first-child > span:first-child ~ span.default {
+                display: inline-block;
+                font-size: 1.2em;
+                padding-bottom: 8px;
+            }
+            .ilFrmPostContent {
+                margin-top: 8px;
+                max-width: 64em;
+            }
+            .ilFrmPostContent > *:first-child {
+                margin-top: 0px;
+            }
+            .ilFrmPostTitle {
+                margin-top: 24px;
+                color: #00876c;
+                font-weight: bold;
+            }
+            #ilFrmPostList {
+                list-style: none;
+                padding-left: 0;
+            }
+            li.ilFrmPostRow {
+                padding: 3px 0 3px 3px;
+                margin-bottom: 24px;
+                border-left: 6px solid #dddddd;
+            }
+            .ilFrmPostRow > div {
+                display: flex;
+            }
+            .ilFrmPostImage img {
+                margin: 0 !important;
+                padding: 6px 9px 9px 6px;
+            }
+            .ilUserIcon {
+                width: 115px;
+            }
+            .small {
+                text-decoration: none;
+                font-size: 0.75rem;
+                color: #6f6f6f;
+            }
+        </style>
+    </head>
+    <body>
+    {{heading}}
+    {{content}}
+    </body>
+</html>
+""".strip()  # noqa: E501 line too long
+

 def learning_module_template(body: bs4.Tag, name: str, prev: Optional[str], next: Optional[str]) -> str:
    # Seems to be comments, ignore those.
@@ -139,13 +237,13 @@ def learning_module_template(body: bs4.Tag, name: str, prev: Optional[str], next
        </div>
    """
    if prev and body.select_one(".ilc_page_lnav_LeftNavigation"):
-        text = body.select_one(".ilc_page_lnav_LeftNavigation").getText().strip()
+        text = cast(bs4.Tag, body.select_one(".ilc_page_lnav_LeftNavigation")).get_text().strip()
        left = f'<a href="{prev}">{text}</a>'
    else:
        left = "<span></span>"

    if next and body.select_one(".ilc_page_rnav_RightNavigation"):
-        text = body.select_one(".ilc_page_rnav_RightNavigation").getText().strip()
+        text = cast(bs4.Tag, body.select_one(".ilc_page_rnav_RightNavigation")).get_text().strip()
        right = f'<a href="{next}">{text}</a>'
    else:
        right = "<span></span>"
@@ -156,12 +254,29 @@ def learning_module_template(body: bs4.Tag, name: str, prev: Optional[str], next
        )

    if bot_nav := body.select_one(".ilc_page_bnav_BottomNavigation"):
-        bot_nav.replace_with(soupify(nav_template.replace(
-            "{{left}}", left).replace("{{right}}", right).encode())
+        bot_nav.replace_with(
+            soupify(nav_template.replace("{{left}}", left).replace("{{right}}", right).encode())
        )

-    body = body.prettify()
-    return _learning_module_template.replace("{{body}}", body).replace("{{name}}", name)
+    body_str = body.prettify()
+    return _learning_module_template.replace("{{body}}", body_str).replace("{{name}}", name)
+
+
+def forum_thread_template(name: str, url: str, heading: bs4.Tag, content: bs4.Tag) -> str:
+    if title := heading.find(name="b"):
+        title.wrap(bs4.Tag(name="a", attrs={"href": url}))
+    return (
+        _forum_thread_template.replace("{{name}}", name)
+        .replace("{{heading}}", heading.prettify())
+        .replace("{{content}}", content.prettify())
+    )
+
+
+@dataclasses.dataclass
+class LinkData:
+    name: str
+    url: str
+    description: str


 class Links(Enum):
@@ -181,6 +296,9 @@ class Links(Enum):
            return None
        raise ValueError("Missing switch case")

+    def collection_as_one(self) -> bool:
+        return self == Links.FANCY
+
    def extension(self) -> Optional[str]:
        if self == Links.FANCY:
            return ".html"
@@ -192,10 +310,47 @@ class Links(Enum):
            return None
        raise ValueError("Missing switch case")

+    def interpolate(self, redirect_delay: int, collection_name: str, links: list[LinkData]) -> str:
+        template = self.template()
+        if template is None:
+            raise ValueError("Cannot interpolate ignored links")
+
+        if len(links) == 1:
+            link = links[0]
+            content = template
+            content = content.replace("{{link}}", link.url)
+            content = content.replace("{{name}}", link.name)
+            content = content.replace("{{description}}", link.description)
+            content = content.replace("{{redirect_delay}}", str(redirect_delay))
+            return content
+        if self == Links.PLAINTEXT or self == Links.INTERNET_SHORTCUT:
+            return "\n".join(f"{link.url}" for link in links)
+
+        # All others get coerced to fancy
+        content = cast(str, Links.FANCY.template())
+        repeated_content = cast(
+            re.Match[str], re.search(r"<!-- REPEAT START -->([\s\S]+)<!-- REPEAT END -->", content)
+        ).group(1)
+
+        parts = []
+        for link in links:
+            instance = repeated_content
+            instance = instance.replace("{{link}}", link.url)
+            instance = instance.replace("{{name}}", link.name)
+            instance = instance.replace("{{description}}", link.description)
+            instance = instance.replace("{{redirect_delay}}", str(redirect_delay))
+            parts.append(instance)
+
+        content = content.replace(repeated_content, "\n".join(parts))
+        content = content.replace("{{name}}", collection_name)
+        content = re.sub(r"<!-- REPEAT REMOVE START -->[\s\S]+<!-- REPEAT REMOVE END -->", "", content)
+
+        return content
+
    @staticmethod
    def from_string(string: str) -> "Links":
        try:
            return Links(string)
        except ValueError:
-            raise ValueError("must be one of 'ignore', 'plaintext',"
-                             " 'html', 'internet-shortcut'")
+            options = [f"'{option.value}'" for option in Links]
+            raise ValueError(f"must be one of {', '.join(options)}") from None
--- a/PFERD/crawl/ilias/ilias_html_cleaner.py
+++ b/PFERD/crawl/ilias/ilias_html_cleaner.py
@@ -1,3 +1,5 @@
+from typing import cast
+
 from bs4 import BeautifulSoup, Comment, Tag

 _STYLE_TAG_CONTENT = """
@@ -12,6 +14,13 @@ _STYLE_TAG_CONTENT = """
      font-weight: bold;
    }

+    .row-flex {
+      display: flex;
+    }
+    .row-flex-wrap {
+      flex-wrap: wrap;
+    }
+
    .accordion-head {
      background-color: #f5f7fa;
      padding: 0.5rem 0;
@@ -30,6 +39,10 @@ _STYLE_TAG_CONTENT = """
      margin: 0.5rem 0;
    }

+    img {
+        background-color: white;
+    }
+
    body {
      padding: 1em;
      grid-template-columns: 1fr min(60rem, 90%) 1fr;
@@ -47,12 +60,11 @@ _ARTICLE_WORTHY_CLASSES = [
 def insert_base_markup(soup: BeautifulSoup) -> BeautifulSoup:
    head = soup.new_tag("head")
    soup.insert(0, head)
+    # Force UTF-8 encoding
+    head.append(soup.new_tag("meta", charset="utf-8"))

-    simplecss_link: Tag = soup.new_tag("link")
    # <link rel="stylesheet" href="https://cdn.simplecss.org/simple.css">
-    simplecss_link["rel"] = "stylesheet"
-    simplecss_link["href"] = "https://cdn.simplecss.org/simple.css"
-    head.append(simplecss_link)
+    head.append(soup.new_tag("link", rel="stylesheet", href="https://cdn.simplecss.org/simple.css"))

    # Basic style tags for compat
    style: Tag = soup.new_tag("style")
@@ -63,18 +75,18 @@ def insert_base_markup(soup: BeautifulSoup) -> BeautifulSoup:


 def clean(soup: BeautifulSoup) -> BeautifulSoup:
-    for block in soup.find_all(class_=lambda x: x in _ARTICLE_WORTHY_CLASSES):
+    for block in cast(list[Tag], soup.find_all(class_=lambda x: x in _ARTICLE_WORTHY_CLASSES)):
        block.name = "article"

-    for block in soup.find_all("h3"):
+    for block in cast(list[Tag], soup.find_all("h3")):
        block.name = "div"

-    for block in soup.find_all("h1"):
+    for block in cast(list[Tag], soup.find_all("h1")):
        block.name = "h3"

-    for block in soup.find_all(class_="ilc_va_ihcap_VAccordIHeadCap"):
+    for block in cast(list[Tag], soup.find_all(class_="ilc_va_ihcap_VAccordIHeadCap")):
        block.name = "h3"
-        block["class"] += ["accordion-head"]
+        block["class"] += ["accordion-head"]  # type: ignore

    for dummy in soup.select(".ilc_text_block_Standard.ilc_Paragraph"):
        children = list(dummy.children)
@@ -85,7 +97,12 @@ def clean(soup: BeautifulSoup) -> BeautifulSoup:
        if isinstance(type(children[0]), Comment):
            dummy.decompose()

-    for hrule_imposter in soup.find_all(class_="ilc_section_Separator"):
+    # Delete video figures, as they can not be internalized anyway
+    for video in soup.select(".ilc_media_cont_MediaContainerHighlighted .ilPageVideo"):
+        if figure := video.find_parent("figure"):
+            figure.decompose()
+
+    for hrule_imposter in cast(list[Tag], soup.find_all(class_="ilc_section_Separator")):
        hrule_imposter.insert(0, soup.new_tag("hr"))

    return soup
--- a/PFERD/crawl/ilias/ilias_web_crawler.py
+++ b/PFERD/crawl/ilias/ilias_web_crawler.py
--- a/PFERD/crawl/ilias/kit_ilias_html.py
+++ b/PFERD/crawl/ilias/kit_ilias_html.py
--- a/PFERD/crawl/ilias/kit_ilias_web_crawler.py
+++ b/PFERD/crawl/ilias/kit_ilias_web_crawler.py
@@ -1,23 +1,14 @@
-from typing import Any, Dict, Optional, Union
+from typing import Literal

-import aiohttp
-import yarl
-from bs4 import BeautifulSoup
-
-from ...auth import Authenticator, TfaAuthenticator
+from ...auth import Authenticator
 from ...config import Config
-from ...logging import log
-from ...utils import soupify
-from ..crawler import CrawlError, CrawlWarning
-from .async_helper import _iorepeat
 from .ilias_web_crawler import IliasWebCrawler, IliasWebCrawlerSection
-
-TargetType = Union[str, int]
+from .shibboleth_login import ShibbolethLogin

 _ILIAS_URL = "https://ilias.studium.kit.edu"


-class KitShibbolethBackgroundLoginSuccessful():
+class KitShibbolethBackgroundLoginSuccessful:
    pass


@@ -25,19 +16,8 @@ class KitIliasWebCrawlerSection(IliasWebCrawlerSection):
    def base_url(self) -> str:
        return _ILIAS_URL

-    def client_id(self) -> str:
-        # KIT ILIAS uses the Shibboleth service for authentication. There's no
-        # use for a client id.
-        return "unused"
-
-    def tfa_auth(self, authenticators: Dict[str, Authenticator]) -> Optional[Authenticator]:
-        value: Optional[str] = self.s.get("tfa_auth")
-        if value is None:
-            return None
-        auth = authenticators.get(value)
-        if auth is None:
-            self.invalid_value("tfa_auth", value, "No such auth section exists")
-        return auth
+    def login(self) -> Literal["shibboleth"]:
+        return "shibboleth"


 class KitIliasWebCrawler(IliasWebCrawler):
@@ -46,184 +26,12 @@ class KitIliasWebCrawler(IliasWebCrawler):
        name: str,
        section: KitIliasWebCrawlerSection,
        config: Config,
-        authenticators: Dict[str, Authenticator]
+        authenticators: dict[str, Authenticator],
    ):
        super().__init__(name, section, config, authenticators)

-        self._shibboleth_login = KitShibbolethLogin(
+        self._shibboleth_login = ShibbolethLogin(
+            _ILIAS_URL,
            self._auth,
            section.tfa_auth(authenticators),
        )
-
-    # We repeat this as the login method in shibboleth doesn't handle I/O errors.
-    # Shibboleth is quite reliable as well, the repeat is likely not critical here.
-    @_iorepeat(3, "Login", failure_is_error=True)
-    async def _authenticate(self) -> None:
-        await self._shibboleth_login.login(self.session)
-
-
-class KitShibbolethLogin:
-    """
-    Login via KIT's shibboleth system.
-    """
-
-    def __init__(self, authenticator: Authenticator, tfa_authenticator: Optional[Authenticator]) -> None:
-        self._auth = authenticator
-        self._tfa_auth = tfa_authenticator
-
-    async def login(self, sess: aiohttp.ClientSession) -> None:
-        """
-        Performs the ILIAS Shibboleth authentication dance and saves the login
-        cookies it receieves.
-
-        This function should only be called whenever it is detected that you're
-        not logged in. The cookies obtained should be good for a few minutes,
-        maybe even an hour or two.
-        """
-
-        # Equivalent: Click on "Mit KIT-Account anmelden" button in
-        # https://ilias.studium.kit.edu/login.php
-        url = f"{_ILIAS_URL}/shib_login.php"
-        data = {
-            "sendLogin": "1",
-            "idp_selection": "https://idp.scc.kit.edu/idp/shibboleth",
-            "il_target": "",
-            "home_organization_selection": "Weiter",
-        }
-        soup: Union[BeautifulSoup, KitShibbolethBackgroundLoginSuccessful] = await _shib_post(sess, url, data)
-
-        if isinstance(soup, KitShibbolethBackgroundLoginSuccessful):
-            return
-
-        # Attempt to login using credentials, if necessary
-        while not self._login_successful(soup):
-            # Searching the form here so that this fails before asking for
-            # credentials rather than after asking.
-            form = soup.find("form", {"class": "full content", "method": "post"})
-            action = form["action"]
-
-            csrf_token = form.find("input", {"name": "csrf_token"})["value"]
-
-            # Equivalent: Enter credentials in
-            # https://idp.scc.kit.edu/idp/profile/SAML2/Redirect/SSO
-            url = "https://idp.scc.kit.edu" + action
-            username, password = await self._auth.credentials()
-            data = {
-                "_eventId_proceed": "",
-                "j_username": username,
-                "j_password": password,
-                "csrf_token": csrf_token
-            }
-            soup = await _post(sess, url, data)
-
-            if soup.find(id="attributeRelease"):
-                raise CrawlError(
-                    "ILIAS Shibboleth entitlements changed! "
-                    "Please log in once in your browser and review them"
-                )
-
-            if self._tfa_required(soup):
-                soup = await self._authenticate_tfa(sess, soup)
-
-            if not self._login_successful(soup):
-                self._auth.invalidate_credentials()
-
-        # Equivalent: Being redirected via JS automatically
-        # (or clicking "Continue" if you have JS disabled)
-        relay_state = soup.find("input", {"name": "RelayState"})
-        saml_response = soup.find("input", {"name": "SAMLResponse"})
-        url = f"{_ILIAS_URL}/Shibboleth.sso/SAML2/POST"
-        data = {  # using the info obtained in the while loop above
-            "RelayState": relay_state["value"],
-            "SAMLResponse": saml_response["value"],
-        }
-        await sess.post(url, data=data)
-
-    async def _authenticate_tfa(
-        self,
-        session: aiohttp.ClientSession,
-        soup: BeautifulSoup
-    ) -> BeautifulSoup:
-        if not self._tfa_auth:
-            self._tfa_auth = TfaAuthenticator("ilias-anon-tfa")
-
-        tfa_token = await self._tfa_auth.password()
-
-        # Searching the form here so that this fails before asking for
-        # credentials rather than after asking.
-        form = soup.find("form", {"method": "post"})
-        action = form["action"]
-        csrf_token = form.find("input", {"name": "csrf_token"})["value"]
-
-        # Equivalent: Enter token in
-        # https://idp.scc.kit.edu/idp/profile/SAML2/Redirect/SSO
-        url = "https://idp.scc.kit.edu" + action
-        data = {
-            "_eventId_proceed": "",
-            "j_tokenNumber": tfa_token,
-            "csrf_token": csrf_token
-        }
-        return await _post(session, url, data)
-
-    @staticmethod
-    def _login_successful(soup: BeautifulSoup) -> bool:
-        relay_state = soup.find("input", {"name": "RelayState"})
-        saml_response = soup.find("input", {"name": "SAMLResponse"})
-        return relay_state is not None and saml_response is not None
-
-    @staticmethod
-    def _tfa_required(soup: BeautifulSoup) -> bool:
-        return soup.find(id="j_tokenNumber") is not None
-
-
-async def _post(session: aiohttp.ClientSession, url: str, data: Any) -> BeautifulSoup:
-    async with session.post(url, data=data) as response:
-        return soupify(await response.read())
-
-
-async def _shib_post(
-    session: aiohttp.ClientSession,
-    url: str,
-    data: Any
-) -> Union[BeautifulSoup, KitShibbolethBackgroundLoginSuccessful]:
-    """
-    aiohttp unescapes '/' and ':' in URL query parameters which is not RFC compliant and rejected
-    by Shibboleth. Thanks a lot. So now we unroll the requests manually, parse location headers and
-    build encoded URL objects ourselves... Who thought mangling location header was a good idea??
-    """
-    log.explain_topic("Shib login POST")
-    async with session.post(url, data=data, allow_redirects=False) as response:
-        location = response.headers.get("location")
-        log.explain(f"Got location {location!r}")
-        if not location:
-            raise CrawlWarning(f"Login failed (1), no location header present at {url}")
-        correct_url = yarl.URL(location, encoded=True)
-        log.explain(f"Corrected location to {correct_url!r}")
-
-        if str(correct_url).startswith(_ILIAS_URL):
-            log.explain("ILIAS recognized our shib token and logged us in in the background, returning")
-            return KitShibbolethBackgroundLoginSuccessful()
-
-        async with session.get(correct_url, allow_redirects=False) as response:
-            location = response.headers.get("location")
-            log.explain(f"Redirected to {location!r} with status {response.status}")
-            # If shib still has a valid session, it will directly respond to the request
-            if location is None:
-                log.explain("Shib recognized us, returning its response directly")
-                return soupify(await response.read())
-
-            as_yarl = yarl.URL(response.url)
-            # Probably not needed anymore, but might catch a few weird situations with a nicer message
-            if not location or not as_yarl.host:
-                raise CrawlWarning(f"Login failed (2), no location header present at {correct_url}")
-
-            correct_url = yarl.URL.build(
-                scheme=as_yarl.scheme,
-                host=as_yarl.host,
-                path=location,
-                encoded=True
-            )
-            log.explain(f"Corrected location to {correct_url!r}")
-
-            async with session.get(correct_url, allow_redirects=False) as response:
-                return soupify(await response.read())
--- a/PFERD/crawl/ilias/shibboleth_login.py
+++ b/PFERD/crawl/ilias/shibboleth_login.py
@@ -0,0 +1,127 @@
+from typing import Any, Optional, cast
+
+import aiohttp
+import yarl
+from bs4 import BeautifulSoup, Tag
+
+from ...auth import Authenticator, TfaAuthenticator
+from ...logging import log
+from ...utils import soupify
+from ..crawler import CrawlError
+
+
+class ShibbolethLogin:
+    """
+    Login via shibboleth system.
+    """
+
+    def __init__(
+        self, ilias_url: str, authenticator: Authenticator, tfa_authenticator: Optional[Authenticator]
+    ) -> None:
+        self._ilias_url = ilias_url
+        self._auth = authenticator
+        self._tfa_auth = tfa_authenticator
+
+    async def login(self, sess: aiohttp.ClientSession) -> None:
+        """
+        Performs the ILIAS Shibboleth authentication dance and saves the login
+        cookies it receieves.
+
+        This function should only be called whenever it is detected that you're
+        not logged in. The cookies obtained should be good for a few minutes,
+        maybe even an hour or two.
+        """
+
+        # Equivalent: Click on "Mit KIT-Account anmelden" button in
+        # https://ilias.studium.kit.edu/login.php
+        url = f"{self._ilias_url}/shib_login.php"
+        async with sess.get(url) as response:
+            shib_url = response.url
+            if str(shib_url).startswith(self._ilias_url):
+                log.explain("ILIAS recognized our shib token and logged us in in the background, returning")
+                return
+            soup: BeautifulSoup = soupify(await response.read())
+
+        # Attempt to login using credentials, if necessary
+        while not self._login_successful(soup):
+            # Searching the form here so that this fails before asking for
+            # credentials rather than after asking.
+            form = cast(Tag, soup.find("form", {"method": "post"}))
+            action = cast(str, form["action"])
+
+            # Equivalent: Enter credentials in
+            # https://idp.scc.kit.edu/idp/profile/SAML2/Redirect/SSO
+            url = str(shib_url.origin()) + action
+            username, password = await self._auth.credentials()
+            data = {
+                "_eventId_proceed": "",
+                "j_username": username,
+                "j_password": password,
+                "fudis_web_authn_assertion_input": "",
+            }
+            if csrf_token_input := form.find("input", {"name": "csrf_token"}):
+                data["csrf_token"] = csrf_token_input["value"]  # type: ignore
+            soup = await _post(sess, url, data)
+
+            if soup.find(id="attributeRelease"):
+                raise CrawlError(
+                    "ILIAS Shibboleth entitlements changed! "
+                    "Please log in once in your browser and review them"
+                )
+
+            if self._tfa_required(soup):
+                soup = await self._authenticate_tfa(sess, soup, shib_url)
+
+            if not self._login_successful(soup):
+                self._auth.invalidate_credentials()
+
+        # Equivalent: Being redirected via JS automatically
+        # (or clicking "Continue" if you have JS disabled)
+        relay_state = cast(Tag, soup.find("input", {"name": "RelayState"}))
+        saml_response = cast(Tag, soup.find("input", {"name": "SAMLResponse"}))
+        url = cast(str, cast(Tag, soup.find("form", {"method": "post"}))["action"])
+        data = {  # using the info obtained in the while loop above
+            "RelayState": cast(str, relay_state["value"]),
+            "SAMLResponse": cast(str, saml_response["value"]),
+        }
+        await sess.post(cast(str, url), data=data)
+
+    async def _authenticate_tfa(
+        self, session: aiohttp.ClientSession, soup: BeautifulSoup, shib_url: yarl.URL
+    ) -> BeautifulSoup:
+        if not self._tfa_auth:
+            self._tfa_auth = TfaAuthenticator("ilias-anon-tfa")
+
+        tfa_token = await self._tfa_auth.password()
+
+        # Searching the form here so that this fails before asking for
+        # credentials rather than after asking.
+        form = cast(Tag, soup.find("form", {"method": "post"}))
+        action = cast(str, form["action"])
+
+        # Equivalent: Enter token in
+        # https://idp.scc.kit.edu/idp/profile/SAML2/Redirect/SSO
+        url = str(shib_url.origin()) + action
+        username, password = await self._auth.credentials()
+        data = {
+            "_eventId_proceed": "",
+            "fudis_otp_input": tfa_token,
+        }
+        if csrf_token_input := form.find("input", {"name": "csrf_token"}):
+            data["csrf_token"] = csrf_token_input["value"]  # type: ignore
+        return await _post(session, url, data)
+
+    @staticmethod
+    def _login_successful(soup: BeautifulSoup) -> bool:
+        relay_state = soup.find("input", {"name": "RelayState"})
+        saml_response = soup.find("input", {"name": "SAMLResponse"})
+        return relay_state is not None and saml_response is not None
+
+    @staticmethod
+    def _tfa_required(soup: BeautifulSoup) -> bool:
+        return soup.find(id="fudiscr-form") is not None
+
+
+async def _post(session: aiohttp.ClientSession, url: str, data: Any) -> BeautifulSoup:
+    async with session.post(url, data=data) as response:
+        return soupify(await response.read())
--- a/PFERD/crawl/kit_ipd_crawler.py
+++ b/PFERD/crawl/kit_ipd_crawler.py
@@ -1,16 +1,21 @@
 import os
 import re
+from collections.abc import Awaitable, Generator, Iterable
 from dataclasses import dataclass
+from datetime import datetime
 from pathlib import PurePath
-from typing import Awaitable, List, Optional, Pattern, Set, Tuple, Union
+from re import Pattern
+from typing import Any, Optional, Union, cast
 from urllib.parse import urljoin

+import aiohttp
 from bs4 import BeautifulSoup, Tag

+from ..auth import Authenticator
 from ..config import Config
 from ..logging import ProgressBar, log
 from ..output_dir import FileSink
-from ..utils import soupify
+from ..utils import sanitize_path_name, soupify
 from .crawler import CrawlError
 from .http_crawler import HttpCrawler, HttpCrawlerSection

@@ -30,126 +35,157 @@ class KitIpdCrawlerSection(HttpCrawlerSection):
        regex = self.s.get("link_regex", r"^.*?[^/]+\.(pdf|zip|c|cpp|java)$")
        return re.compile(regex)

+    def basic_auth(self, authenticators: dict[str, Authenticator]) -> Optional[Authenticator]:
+        value: Optional[str] = self.s.get("auth")
+        if value is None:
+            return None
+        auth = authenticators.get(value)
+        if auth is None:
+            self.invalid_value("auth", value, "No such auth section exists")
+        return auth

-@dataclass(unsafe_hash=True)
+
+@dataclass
 class KitIpdFile:
    name: str
    url: str

+    def explain(self) -> None:
+        log.explain(f"File {self.name!r} (href={self.url!r})")
+

@dataclass
 class KitIpdFolder:
    name: str
-    files: List[KitIpdFile]
+    entries: list[Union[KitIpdFile, "KitIpdFolder"]]

    def explain(self) -> None:
        log.explain_topic(f"Folder {self.name!r}")
-        for file in self.files:
-            log.explain(f"File {file.name!r} (href={file.url!r})")
-
-    def __hash__(self) -> int:
-        return self.name.__hash__()
+        for entry in self.entries:
+            entry.explain()


 class KitIpdCrawler(HttpCrawler):
-
    def __init__(
-            self,
-            name: str,
-            section: KitIpdCrawlerSection,
-            config: Config,
+        self,
+        name: str,
+        section: KitIpdCrawlerSection,
+        config: Config,
+        authenticators: dict[str, Authenticator],
    ):
        super().__init__(name, section, config)
        self._url = section.target()
        self._file_regex = section.link_regex()
+        self._authenticator = section.basic_auth(authenticators)
+        self._basic_auth: Optional[aiohttp.BasicAuth] = None

    async def _run(self) -> None:
+        if self._authenticator:
+            username, password = await self._authenticator.credentials()
+            self._basic_auth = aiohttp.BasicAuth(username, password)
+
        maybe_cl = await self.crawl(PurePath("."))
        if not maybe_cl:
            return

-        tasks: List[Awaitable[None]] = []
+        tasks: list[Awaitable[None]] = []

        async with maybe_cl:
            for item in await self._fetch_items():
+                item.explain()
                if isinstance(item, KitIpdFolder):
-                    tasks.append(self._crawl_folder(item))
+                    tasks.append(self._crawl_folder(PurePath("."), item))
                else:
-                    # Orphan files are placed in the root folder
-                    tasks.append(self._download_file(PurePath("."), item))
+                    log.explain_topic(f"Orphan file {item.name!r} (href={item.url!r})")
+                    log.explain("Attributing it to root folder")
+                    # do this here to at least be sequential and not parallel (rate limiting is hard, as the
+                    # crawl abstraction does not hold for these requests)
+                    etag, mtime = await self._request_resource_version(item.url)
+                    tasks.append(self._download_file(PurePath("."), item, etag, mtime))

        await self.gather(tasks)

-    async def _crawl_folder(self, folder: KitIpdFolder) -> None:
-        path = PurePath(folder.name)
+    async def _crawl_folder(self, parent: PurePath, folder: KitIpdFolder) -> None:
+        path = parent / sanitize_path_name(folder.name)
        if not await self.crawl(path):
            return

-        tasks = [self._download_file(path, file) for file in folder.files]
+        tasks = []
+        for entry in folder.entries:
+            if isinstance(entry, KitIpdFolder):
+                tasks.append(self._crawl_folder(path, entry))
+            else:
+                # do this here to at least be sequential and not parallel (rate limiting is hard, as the crawl
+                # abstraction does not hold for these requests)
+                etag, mtime = await self._request_resource_version(entry.url)
+                tasks.append(self._download_file(path, entry, etag, mtime))

        await self.gather(tasks)

-    async def _download_file(self, parent: PurePath, file: KitIpdFile) -> None:
-        element_path = parent / file.name
-        maybe_dl = await self.download(element_path)
+    async def _download_file(
+        self, parent: PurePath, file: KitIpdFile, etag: Optional[str], mtime: Optional[datetime]
+    ) -> None:
+        element_path = parent / sanitize_path_name(file.name)
+
+        prev_etag = self._get_previous_etag_from_report(element_path)
+        etag_differs = None if prev_etag is None else prev_etag != etag
+
+        maybe_dl = await self.download(element_path, etag_differs=etag_differs, mtime=mtime)
        if not maybe_dl:
+            # keep storing the known file's etag
+            if prev_etag:
+                self._add_etag_to_report(element_path, prev_etag)
            return

        async with maybe_dl as (bar, sink):
-            await self._stream_from_url(file.url, sink, bar)
+            await self._stream_from_url(file.url, element_path, sink, bar)

-    async def _fetch_items(self) -> Set[Union[KitIpdFile, KitIpdFolder]]:
+    async def _fetch_items(self) -> Iterable[KitIpdFile | KitIpdFolder]:
        page, url = await self.get_page()
-        elements: List[Tag] = self._find_file_links(page)
-        items: Set[Union[KitIpdFile, KitIpdFolder]] = set()
+        elements: list[Tag] = self._find_file_links(page)

+        # do not add unnecessary nesting for a single <h1> heading
+        drop_h1: bool = len(page.find_all(name="h1")) <= 1
+
+        folder_tree: KitIpdFolder = KitIpdFolder(".", [])
        for element in elements:
-            folder_label = self._find_folder_label(element)
-            if folder_label:
-                folder = self._extract_folder(folder_label, url)
-                if folder not in items:
-                    items.add(folder)
-                    folder.explain()
-            else:
-                file = self._extract_file(element, url)
-                items.add(file)
-                log.explain_topic(f"Orphan file {file.name!r} (href={file.url!r})")
-                log.explain("Attributing it to root folder")
+            parent = HttpCrawler.get_folder_structure_from_heading_hierarchy(element, drop_h1)
+            file = self._extract_file(element, url)

-        return items
+            current_folder: KitIpdFolder = folder_tree
+            for folder_name in parent.parts:
+                # helps the type checker to verify that current_folder is indeed a folder
+                def subfolders() -> Generator[KitIpdFolder, Any, None]:
+                    return (entry for entry in current_folder.entries if isinstance(entry, KitIpdFolder))

-    def _extract_folder(self, folder_tag: Tag, url: str) -> KitIpdFolder:
-        files: List[KitIpdFile] = []
-        name = folder_tag.getText().strip()
+                if not any(entry.name == folder_name for entry in subfolders()):
+                    current_folder.entries.append(KitIpdFolder(folder_name, []))
+                current_folder = next(entry for entry in subfolders() if entry.name == folder_name)

-        container: Tag = folder_tag.findNextSibling(name="table")
-        for link in self._find_file_links(container):
-            files.append(self._extract_file(link, url))
+            current_folder.entries.append(file)

-        return KitIpdFolder(name, files)
-
-    @staticmethod
-    def _find_folder_label(file_link: Tag) -> Optional[Tag]:
-        enclosing_table: Tag = file_link.findParent(name="table")
-        if enclosing_table is None:
-            return None
-        return enclosing_table.findPreviousSibling(name=re.compile("^h[1-6]$"))
+        return folder_tree.entries

    def _extract_file(self, link: Tag, url: str) -> KitIpdFile:
        url = self._abs_url_from_link(url, link)
        name = os.path.basename(url)
        return KitIpdFile(name, url)

-    def _find_file_links(self, tag: Union[Tag, BeautifulSoup]) -> List[Tag]:
-        return tag.findAll(name="a", attrs={"href": self._file_regex})
+    def _find_file_links(self, tag: Tag | BeautifulSoup) -> list[Tag]:
+        return cast(list[Tag], tag.find_all(name="a", attrs={"href": self._file_regex}))

    def _abs_url_from_link(self, url: str, link_tag: Tag) -> str:
-        return urljoin(url, link_tag.get("href"))
+        return urljoin(url, cast(str, link_tag.get("href")))

-    async def _stream_from_url(self, url: str, sink: FileSink, bar: ProgressBar) -> None:
-        async with self.session.get(url, allow_redirects=False) as resp:
+    async def _stream_from_url(self, url: str, path: PurePath, sink: FileSink, bar: ProgressBar) -> None:
+        async with self.session.get(url, allow_redirects=False, auth=self._basic_auth) as resp:
            if resp.status == 403:
                raise CrawlError("Received a 403. Are you within the KIT network/VPN?")
+            if resp.status == 401:
+                raise CrawlError("Received a 401. Do you maybe need credentials?")
+            if resp.status >= 400:
+                raise CrawlError(f"Received HTTP {resp.status} when trying to download {url!r}")
+
            if resp.content_length:
                bar.set_total(resp.content_length)

@@ -159,8 +195,10 @@ class KitIpdCrawler(HttpCrawler):

            sink.done()

-    async def get_page(self) -> Tuple[BeautifulSoup, str]:
-        async with self.session.get(self._url) as request:
+            self._add_etag_to_report(path, resp.headers.get("ETag"))
+
+    async def get_page(self) -> tuple[BeautifulSoup, str]:
+        async with self.session.get(self._url, auth=self._basic_auth) as request:
            # The web page for Algorithmen für Routenplanung contains some
            # weird comments that beautifulsoup doesn't parse correctly. This
            # hack enables those pages to be crawled, and should hopefully not
--- a/PFERD/crawl/local_crawler.py
+++ b/PFERD/crawl/local_crawler.py
@@ -18,31 +18,28 @@ class LocalCrawlerSection(CrawlerSection):
    def crawl_delay(self) -> float:
        value = self.s.getfloat("crawl_delay", fallback=0.0)
        if value < 0:
-            self.invalid_value("crawl_delay", value,
-                               "Must not be negative")
+            self.invalid_value("crawl_delay", value, "Must not be negative")
        return value

    def download_delay(self) -> float:
        value = self.s.getfloat("download_delay", fallback=0.0)
        if value < 0:
-            self.invalid_value("download_delay", value,
-                               "Must not be negative")
+            self.invalid_value("download_delay", value, "Must not be negative")
        return value

    def download_speed(self) -> Optional[int]:
        value = self.s.getint("download_speed")
        if value is not None and value <= 0:
-            self.invalid_value("download_speed", value,
-                               "Must be greater than 0")
+            self.invalid_value("download_speed", value, "Must be greater than 0")
        return value


 class LocalCrawler(Crawler):
    def __init__(
-            self,
-            name: str,
-            section: LocalCrawlerSection,
-            config: Config,
+        self,
+        name: str,
+        section: LocalCrawlerSection,
+        config: Config,
    ):
        super().__init__(name, section, config)

@@ -74,10 +71,12 @@ class LocalCrawler(Crawler):
        tasks = []

        async with cl:
-            await asyncio.sleep(random.uniform(
-                0.5 * self._crawl_delay,
-                self._crawl_delay,
-            ))
+            await asyncio.sleep(
+                random.uniform(
+                    0.5 * self._crawl_delay,
+                    self._crawl_delay,
+                )
+            )

            for child in path.iterdir():
                pure_child = cl.path / child.name
@@ -93,10 +92,12 @@ class LocalCrawler(Crawler):
            return

        async with dl as (bar, sink):
-            await asyncio.sleep(random.uniform(
-                0.5 * self._download_delay,
-                self._download_delay,
-            ))
+            await asyncio.sleep(
+                random.uniform(
+                    0.5 * self._download_delay,
+                    self._download_delay,
+                )
+            )

            bar.set_total(stat.st_size)

--- a/PFERD/deduplicator.py
+++ b/PFERD/deduplicator.py
@@ -1,5 +1,5 @@
+from collections.abc import Iterator
 from pathlib import PurePath
-from typing import Iterator, Set

 from .logging import log
 from .utils import fmt_path
@@ -16,15 +16,34 @@ def name_variants(path: PurePath) -> Iterator[PurePath]:
 class Deduplicator:
    FORBIDDEN_CHARS = '<>:"/\\|?*' + "".join([chr(i) for i in range(0, 32)])
    FORBIDDEN_NAMES = {
-        "CON", "PRN", "AUX", "NUL",
-        "COM1", "COM2", "COM3", "COM4", "COM5", "COM6", "COM7", "COM8", "COM9",
-        "LPT1", "LPT2", "LPT3", "LPT4", "LPT5", "LPT6", "LPT7", "LPT8", "LPT9",
+        "CON",
+        "PRN",
+        "AUX",
+        "NUL",
+        "COM1",
+        "COM2",
+        "COM3",
+        "COM4",
+        "COM5",
+        "COM6",
+        "COM7",
+        "COM8",
+        "COM9",
+        "LPT1",
+        "LPT2",
+        "LPT3",
+        "LPT4",
+        "LPT5",
+        "LPT6",
+        "LPT7",
+        "LPT8",
+        "LPT9",
    }

    def __init__(self, windows_paths: bool) -> None:
        self._windows_paths = windows_paths

-        self._known: Set[PurePath] = set()
+        self._known: set[PurePath] = set()

    def _add(self, path: PurePath) -> None:
        self._known.add(path)
--- a/PFERD/limiter.py
+++ b/PFERD/limiter.py
@@ -1,8 +1,9 @@
 import asyncio
 import time
+from collections.abc import AsyncIterator
 from contextlib import asynccontextmanager
 from dataclasses import dataclass
-from typing import AsyncIterator, Optional
+from typing import Optional


@dataclass
@@ -12,12 +13,7 @@ class Slot:


 class Limiter:
-    def __init__(
-            self,
-            task_limit: int,
-            download_limit: int,
-            task_delay: float
-    ):
+    def __init__(self, task_limit: int, download_limit: int, task_delay: float):
        if task_limit <= 0:
            raise ValueError("task limit must be at least 1")
        if download_limit <= 0:
--- a/PFERD/logging.py
+++ b/PFERD/logging.py
@@ -1,16 +1,23 @@
 import asyncio
 import sys
 import traceback
-from contextlib import asynccontextmanager, contextmanager
-# TODO In Python 3.9 and above, ContextManager is deprecated
-from typing import AsyncIterator, ContextManager, Iterator, List, Optional
+from collections.abc import AsyncIterator, Iterator
+from contextlib import AbstractContextManager, asynccontextmanager, contextmanager
+from typing import Any, Optional

 from rich.console import Console, Group
 from rich.live import Live
 from rich.markup import escape
 from rich.panel import Panel
-from rich.progress import (BarColumn, DownloadColumn, Progress, TaskID, TextColumn, TimeRemainingColumn,
-                           TransferSpeedColumn)
+from rich.progress import (
+    BarColumn,
+    DownloadColumn,
+    Progress,
+    TaskID,
+    TextColumn,
+    TimeRemainingColumn,
+    TransferSpeedColumn,
+)
 from rich.table import Column


@@ -54,7 +61,7 @@ class Log:
        self._showing_progress = False
        self._progress_suspended = False
        self._lock = asyncio.Lock()
-        self._lines: List[str] = []
+        self._lines: list[str] = []

        # Whether different parts of the output are enabled or disabled
        self.output_explain = False
@@ -115,7 +122,7 @@ class Log:
        for line in self._lines:
            self.print(line)

-    def print(self, text: str) -> None:
+    def print(self, text: Any) -> None:
        """
        Print a normal message. Allows markup.
        """
@@ -177,10 +184,14 @@ class Log:
        # Our print function doesn't take types other than strings, but the
        # underlying rich.print function does. This call is a special case
        # anyways, and we're calling it internally, so this should be fine.
-        self.print(Panel.fit("""
+        self.print(
+            Panel.fit(
+                """
 Please copy your program output and send it to the PFERD maintainers, either
 directly or as a GitHub issue: https://github.com/Garmelon/PFERD/issues/new
-        """.strip()))  # type: ignore
+        """.strip()
+            )
+        )

    def explain_topic(self, text: str) -> None:
        """
@@ -237,10 +248,10 @@ directly or as a GitHub issue: https://github.com/Garmelon/PFERD/issues/new

    @contextmanager
    def _bar(
-            self,
-            progress: Progress,
-            description: str,
-            total: Optional[float],
+        self,
+        progress: Progress,
+        description: str,
+        total: Optional[float],
    ) -> Iterator[ProgressBar]:
        if total is None:
            # Indeterminate progress bar
@@ -256,12 +267,12 @@ directly or as a GitHub issue: https://github.com/Garmelon/PFERD/issues/new
            self._update_live()

    def crawl_bar(
-            self,
-            style: str,
-            action: str,
-            text: str,
-            total: Optional[float] = None,
-    ) -> ContextManager[ProgressBar]:
+        self,
+        style: str,
+        action: str,
+        text: str,
+        total: Optional[float] = None,
+    ) -> AbstractContextManager[ProgressBar]:
        """
        Allows markup in the "style" argument which will be applied to the
        "action" string.
@@ -272,12 +283,12 @@ directly or as a GitHub issue: https://github.com/Garmelon/PFERD/issues/new
        return self._bar(self._crawl_progress, description, total)

    def download_bar(
-            self,
-            style: str,
-            action: str,
-            text: str,
-            total: Optional[float] = None,
-    ) -> ContextManager[ProgressBar]:
+        self,
+        style: str,
+        action: str,
+        text: str,
+        total: Optional[float] = None,
+    ) -> AbstractContextManager[ProgressBar]:
        """
        Allows markup in the "style" argument which will be applied to the
        "action" string.
--- a/PFERD/output_dir.py
+++ b/PFERD/output_dir.py
@@ -4,12 +4,13 @@ import os
 import random
 import shutil
 import string
-from contextlib import contextmanager
+from collections.abc import Iterator
+from contextlib import contextmanager, suppress
 from dataclasses import dataclass
 from datetime import datetime
 from enum import Enum
 from pathlib import Path, PurePath
-from typing import BinaryIO, Iterator, Optional, Tuple
+from typing import BinaryIO, Optional

 from .logging import log
 from .report import Report, ReportLoadError
@@ -35,8 +36,7 @@ class Redownload(Enum):
        try:
            return Redownload(string)
        except ValueError:
-            raise ValueError("must be one of 'never', 'never-smart',"
-                             " 'always', 'always-smart'")
+            raise ValueError("must be one of 'never', 'never-smart', 'always', 'always-smart'") from None


 class OnConflict(Enum):
@@ -51,12 +51,15 @@ class OnConflict(Enum):
        try:
            return OnConflict(string)
        except ValueError:
-            raise ValueError("must be one of 'prompt', 'local-first',"
-                             " 'remote-first', 'no-delete', 'no-delete-prompt-overwrite'")
+            raise ValueError(
+                "must be one of 'prompt', 'local-first',"
+                " 'remote-first', 'no-delete', 'no-delete-prompt-overwrite'"
+            ) from None


@dataclass
 class Heuristics:
+    etag_differs: Optional[bool]
    mtime: Optional[datetime]


@@ -95,13 +98,13 @@ class FileSinkToken(ReusableAsyncContextManager[FileSink]):
    # download handed back to the OutputDirectory.

    def __init__(
-            self,
-            output_dir: "OutputDirectory",
-            remote_path: PurePath,
-            path: PurePath,
-            local_path: Path,
-            heuristics: Heuristics,
-            on_conflict: OnConflict,
+        self,
+        output_dir: "OutputDirectory",
+        remote_path: PurePath,
+        path: PurePath,
+        local_path: Path,
+        heuristics: Heuristics,
+        on_conflict: OnConflict,
    ):
        super().__init__()

@@ -117,15 +120,17 @@ class FileSinkToken(ReusableAsyncContextManager[FileSink]):
        sink = FileSink(file)

        async def after_download() -> None:
-            await self._output_dir._after_download(DownloadInfo(
-                self._remote_path,
-                self._path,
-                self._local_path,
-                tmp_path,
-                self._heuristics,
-                self._on_conflict,
-                sink.is_done(),
-            ))
+            await self._output_dir._after_download(
+                DownloadInfo(
+                    self._remote_path,
+                    self._path,
+                    self._local_path,
+                    tmp_path,
+                    self._heuristics,
+                    self._on_conflict,
+                    sink.is_done(),
+                )
+            )

        self._stack.push_async_callback(after_download)
        self._stack.enter_context(file)
@@ -137,10 +142,10 @@ class OutputDirectory:
    REPORT_FILE = PurePath(".report")

    def __init__(
-            self,
-            root: Path,
-            redownload: Redownload,
-            on_conflict: OnConflict,
+        self,
+        root: Path,
+        redownload: Redownload,
+        on_conflict: OnConflict,
    ):
        if os.name == "nt":
            # Windows limits the path length to 260 for some historical reason.
@@ -173,8 +178,8 @@ class OutputDirectory:

        try:
            self._root.mkdir(parents=True, exist_ok=True)
-        except OSError:
-            raise OutputDirError("Failed to create base directory")
+        except OSError as e:
+            raise OutputDirError("Failed to create base directory") from e

    def register_reserved(self, path: PurePath) -> None:
        self._report.mark_reserved(path)
@@ -192,11 +197,11 @@ class OutputDirectory:
        return self._root / path

    def _should_download(
-            self,
-            local_path: Path,
-            heuristics: Heuristics,
-            redownload: Redownload,
-            on_conflict: OnConflict,
+        self,
+        local_path: Path,
+        heuristics: Heuristics,
+        redownload: Redownload,
+        on_conflict: OnConflict,
    ) -> bool:
        if not local_path.exists():
            log.explain("No corresponding file present locally")
@@ -233,8 +238,16 @@ class OutputDirectory:

        remote_newer = None

+        # ETag should be a more reliable indicator than mtime, so we check it first
+        if heuristics.etag_differs is not None:
+            remote_newer = heuristics.etag_differs
+            if remote_newer:
+                log.explain("Remote file's entity tag differs")
+            else:
+                log.explain("Remote file's entity tag is the same")
+
        # Python on Windows crashes when faced with timestamps around the unix epoch
-        if heuristics.mtime and (os.name != "nt" or heuristics.mtime.year > 1970):
+        if remote_newer is None and heuristics.mtime and (os.name != "nt" or heuristics.mtime.year > 1970):
            mtime = heuristics.mtime
            remote_newer = mtime.timestamp() > stat.st_mtime
            if remote_newer:
@@ -261,9 +274,9 @@ class OutputDirectory:
    # files.

    async def _conflict_lfrf(
-            self,
-            on_conflict: OnConflict,
-            path: PurePath,
+        self,
+        on_conflict: OnConflict,
+        path: PurePath,
    ) -> bool:
        if on_conflict in {OnConflict.PROMPT, OnConflict.NO_DELETE_PROMPT_OVERWRITE}:
            async with log.exclusive_output():
@@ -280,9 +293,9 @@ class OutputDirectory:
        raise ValueError(f"{on_conflict!r} is not a valid conflict policy")

    async def _conflict_ldrf(
-            self,
-            on_conflict: OnConflict,
-            path: PurePath,
+        self,
+        on_conflict: OnConflict,
+        path: PurePath,
    ) -> bool:
        if on_conflict in {OnConflict.PROMPT, OnConflict.NO_DELETE_PROMPT_OVERWRITE}:
            async with log.exclusive_output():
@@ -299,10 +312,10 @@ class OutputDirectory:
        raise ValueError(f"{on_conflict!r} is not a valid conflict policy")

    async def _conflict_lfrd(
-            self,
-            on_conflict: OnConflict,
-            path: PurePath,
-            parent: PurePath,
+        self,
+        on_conflict: OnConflict,
+        path: PurePath,
+        parent: PurePath,
    ) -> bool:
        if on_conflict in {OnConflict.PROMPT, OnConflict.NO_DELETE_PROMPT_OVERWRITE}:
            async with log.exclusive_output():
@@ -319,9 +332,9 @@ class OutputDirectory:
        raise ValueError(f"{on_conflict!r} is not a valid conflict policy")

    async def _conflict_delete_lf(
-            self,
-            on_conflict: OnConflict,
-            path: PurePath,
+        self,
+        on_conflict: OnConflict,
+        path: PurePath,
    ) -> bool:
        if on_conflict == OnConflict.PROMPT:
            async with log.exclusive_output():
@@ -344,9 +357,9 @@ class OutputDirectory:
        return base.parent / name

    async def _create_tmp_file(
-            self,
-            local_path: Path,
-    ) -> Tuple[Path, BinaryIO]:
+        self,
+        local_path: Path,
+    ) -> tuple[Path, BinaryIO]:
        """
        May raise an OutputDirError.
        """
@@ -362,20 +375,38 @@ class OutputDirectory:

        raise OutputDirError("Failed to create temporary file")

+    def should_try_download(
+        self,
+        path: PurePath,
+        *,
+        etag_differs: Optional[bool] = None,
+        mtime: Optional[datetime] = None,
+        redownload: Optional[Redownload] = None,
+        on_conflict: Optional[OnConflict] = None,
+    ) -> bool:
+        heuristics = Heuristics(etag_differs, mtime)
+        redownload = self._redownload if redownload is None else redownload
+        on_conflict = self._on_conflict if on_conflict is None else on_conflict
+        local_path = self.resolve(path)
+
+        return self._should_download(local_path, heuristics, redownload, on_conflict)
+
    async def download(
-            self,
-            remote_path: PurePath,
-            path: PurePath,
-            mtime: Optional[datetime] = None,
-            redownload: Optional[Redownload] = None,
-            on_conflict: Optional[OnConflict] = None,
+        self,
+        remote_path: PurePath,
+        path: PurePath,
+        *,
+        etag_differs: Optional[bool] = None,
+        mtime: Optional[datetime] = None,
+        redownload: Optional[Redownload] = None,
+        on_conflict: Optional[OnConflict] = None,
    ) -> Optional[FileSinkToken]:
        """
        May throw an OutputDirError, a MarkDuplicateError or a
        MarkConflictError.
        """

-        heuristics = Heuristics(mtime)
+        heuristics = Heuristics(etag_differs, mtime)
        redownload = self._redownload if redownload is None else redownload
        on_conflict = self._on_conflict if on_conflict is None else on_conflict
        local_path = self.resolve(path)
@@ -479,10 +510,8 @@ class OutputDirectory:
            await self._cleanup(child, pure_child)

        if delete_self:
-            try:
+            with suppress(OSError):
                path.rmdir()
-            except OSError:
-                pass

    async def _cleanup_file(self, path: Path, pure: PurePath) -> None:
        if self._report.is_marked(pure):
--- a/PFERD/pferd.py
+++ b/PFERD/pferd.py
@@ -1,5 +1,5 @@
-from pathlib import Path
-from typing import Dict, List, Optional
+from pathlib import Path, PurePath
+from typing import Optional

 from rich.markup import escape

@@ -15,7 +15,7 @@ class PferdLoadError(Exception):


 class Pferd:
-    def __init__(self, config: Config, cli_crawlers: Optional[List[str]], cli_skips: Optional[List[str]]):
+    def __init__(self, config: Config, cli_crawlers: Optional[list[str]], cli_skips: Optional[list[str]]):
        """
        May throw PferdLoadError.
        """
@@ -23,10 +23,10 @@ class Pferd:
        self._config = config
        self._crawlers_to_run = self._find_crawlers_to_run(config, cli_crawlers, cli_skips)

-        self._authenticators: Dict[str, Authenticator] = {}
-        self._crawlers: Dict[str, Crawler] = {}
+        self._authenticators: dict[str, Authenticator] = {}
+        self._crawlers: dict[str, Crawler] = {}

-    def _find_config_crawlers(self, config: Config) -> List[str]:
+    def _find_config_crawlers(self, config: Config) -> list[str]:
        crawl_sections = []

        for name, section in config.crawl_sections():
@@ -37,7 +37,7 @@ class Pferd:

        return crawl_sections

-    def _find_cli_crawlers(self, config: Config, cli_crawlers: List[str]) -> List[str]:
+    def _find_cli_crawlers(self, config: Config, cli_crawlers: list[str]) -> list[str]:
        if len(cli_crawlers) != len(set(cli_crawlers)):
            raise PferdLoadError("Some crawlers were selected multiple times")

@@ -66,14 +66,14 @@ class Pferd:
        return crawlers_to_run

    def _find_crawlers_to_run(
-            self,
-            config: Config,
-            cli_crawlers: Optional[List[str]],
-            cli_skips: Optional[List[str]],
-    ) -> List[str]:
+        self,
+        config: Config,
+        cli_crawlers: Optional[list[str]],
+        cli_skips: Optional[list[str]],
+    ) -> list[str]:
        log.explain_topic("Deciding which crawlers to run")

-        crawlers: List[str]
+        crawlers: list[str]
        if cli_crawlers is None:
            log.explain("No crawlers specified on CLI")
            log.explain("Running crawlers specified in config")
@@ -104,7 +104,7 @@ class Pferd:

    def _load_crawlers(self) -> None:
        # Cookie sharing
-        kit_ilias_web_paths: Dict[Authenticator, List[Path]] = {}
+        kit_ilias_web_paths: dict[Authenticator, list[Path]] = {}

        for name, section in self._config.crawl_sections():
            log.print(f"[bold bright_cyan]Loading[/] {escape(name)}")
@@ -117,9 +117,8 @@ class Pferd:
            crawler = crawler_constructor(name, section, self._config, self._authenticators)
            self._crawlers[name] = crawler

-            if self._config.default_section.share_cookies():
-                if isinstance(crawler, KitIliasWebCrawler):
-                    crawler.share_cookies(kit_ilias_web_paths)
+            if self._config.default_section.share_cookies() and isinstance(crawler, KitIliasWebCrawler):
+                crawler.share_cookies(kit_ilias_web_paths)

    def debug_transforms(self) -> None:
        for name in self._crawlers_to_run:
@@ -161,26 +160,32 @@ class Pferd:

    def print_report(self) -> None:
        for name in self._crawlers_to_run:
-            crawler = self._crawlers.get(name)
-            if crawler is None:
+            crawlerOpt = self._crawlers.get(name)
+            if crawlerOpt is None:
                continue  # Crawler failed to load
+            crawler = crawlerOpt

            log.report("")
            log.report(f"[bold bright_cyan]Report[/] for {escape(name)}")

+            def fmt_path_link(relative_path: PurePath) -> str:
+                # We need to URL-encode the path because it might contain spaces or special characters
+                link = crawler.output_dir.resolve(relative_path).absolute().as_uri()
+                return f"[link={link}]{fmt_path(relative_path)}[/link]"
+
            something_changed = False
            for path in sorted(crawler.report.added_files):
                something_changed = True
-                log.report(f"  [bold bright_green]Added[/] {fmt_path(path)}")
+                log.report(f"  [bold bright_green]Added[/] {fmt_path_link(path)}")
            for path in sorted(crawler.report.changed_files):
                something_changed = True
-                log.report(f"  [bold bright_yellow]Changed[/] {fmt_path(path)}")
+                log.report(f"  [bold bright_yellow]Changed[/] {fmt_path_link(path)}")
            for path in sorted(crawler.report.deleted_files):
                something_changed = True
                log.report(f"  [bold bright_magenta]Deleted[/] {fmt_path(path)}")
            for path in sorted(crawler.report.not_deleted_files):
                something_changed = True
-                log.report_not_deleted(f"  [bold bright_magenta]Not deleted[/] {fmt_path(path)}")
+                log.report_not_deleted(f"  [bold bright_magenta]Not deleted[/] {fmt_path_link(path)}")

            for warning in crawler.report.encountered_warnings:
                something_changed = True
--- a/PFERD/report.py
+++ b/PFERD/report.py
@@ -1,6 +1,6 @@
 import json
 from pathlib import Path, PurePath
-from typing import Any, Dict, List, Optional, Set
+from typing import Any, Optional


 class ReportLoadError(Exception):
@@ -34,15 +34,6 @@ class MarkConflictError(Exception):
        self.collides_with = collides_with


-# TODO Use PurePath.is_relative_to when updating to 3.9
-def is_relative_to(a: PurePath, b: PurePath) -> bool:
-    try:
-        a.relative_to(b)
-        return True
-    except ValueError:
-        return False
-
-
 class Report:
    """
    A report of a synchronization. Includes all files found by the crawler, as
@@ -51,32 +42,32 @@ class Report:

    def __init__(self) -> None:
        # Paths found by the crawler, untransformed
-        self.found_paths: Set[PurePath] = set()
+        self.found_paths: set[PurePath] = set()

        # Files reserved for metadata files (e. g. the report file or cookies)
        # that can't be overwritten by user transforms and won't be cleaned up
        # at the end.
-        self.reserved_files: Set[PurePath] = set()
+        self.reserved_files: set[PurePath] = set()

        # Files found by the crawler, transformed. Only includes files that
        # were downloaded (or a download was attempted)
-        self.known_files: Set[PurePath] = set()
+        self.known_files: set[PurePath] = set()

-        self.added_files: Set[PurePath] = set()
-        self.changed_files: Set[PurePath] = set()
-        self.deleted_files: Set[PurePath] = set()
+        self.added_files: set[PurePath] = set()
+        self.changed_files: set[PurePath] = set()
+        self.deleted_files: set[PurePath] = set()
        # Files that should have been deleted by the cleanup but weren't
-        self.not_deleted_files: Set[PurePath] = set()
+        self.not_deleted_files: set[PurePath] = set()

        # Custom crawler-specific data
-        self.custom: Dict[str, Any] = dict()
+        self.custom: dict[str, Any] = dict()

        # Encountered errors and warnings
-        self.encountered_warnings: List[str] = []
-        self.encountered_errors: List[str] = []
+        self.encountered_warnings: list[str] = []
+        self.encountered_errors: list[str] = []

    @staticmethod
-    def _get_list_of_strs(data: Dict[str, Any], key: str) -> List[str]:
+    def _get_list_of_strs(data: dict[str, Any], key: str) -> list[str]:
        result: Any = data.get(key, [])

        if not isinstance(result, list):
@@ -89,8 +80,8 @@ class Report:
        return result

    @staticmethod
-    def _get_str_dictionary(data: Dict[str, Any], key: str) -> Dict[str, Any]:
-        result: Dict[str, Any] = data.get(key, {})
+    def _get_str_dictionary(data: dict[str, Any], key: str) -> dict[str, Any]:
+        result: dict[str, Any] = data.get(key, {})

        if not isinstance(result, dict):
            raise ReportLoadError(f"Incorrect format: {key!r} is not a dictionary")
@@ -173,13 +164,13 @@ class Report:
            if path == other:
                raise MarkDuplicateError(path)

-            if is_relative_to(path, other) or is_relative_to(other, path):
+            if path.is_relative_to(other) or other.is_relative_to(path):
                raise MarkConflictError(path, other)

        self.known_files.add(path)

    @property
-    def marked(self) -> Set[PurePath]:
+    def marked(self) -> set[PurePath]:
        return self.known_files | self.reserved_files

    def is_marked(self, path: PurePath) -> bool:
--- a/PFERD/transformer.py
+++ b/PFERD/transformer.py
@@ -1,10 +1,12 @@
 import ast
+import contextlib
 import re
 from abc import ABC, abstractmethod
+from collections.abc import Callable, Sequence
 from dataclasses import dataclass
 from enum import Enum
 from pathlib import PurePath
-from typing import Callable, Dict, List, Optional, Sequence, TypeVar, Union
+from typing import Optional, TypeVar

 from .logging import log
 from .utils import fmt_path, str_path
@@ -23,7 +25,7 @@ class Empty:
    pass


-RightSide = Union[str, Ignore, Empty]
+RightSide = str | Ignore | Empty


@dataclass
@@ -35,7 +37,7 @@ class Ignored:
    pass


-TransformResult = Optional[Union[Transformed, Ignored]]
+TransformResult = Transformed | Ignored | None


@dataclass
@@ -47,7 +49,7 @@ class Rule:
    right: RightSide
    right_index: int

-    def right_result(self, path: PurePath) -> Union[str, Transformed, Ignored]:
+    def right_result(self, path: PurePath) -> str | Transformed | Ignored:
        if isinstance(self.right, str):
            return self.right
        elif isinstance(self.right, Ignore):
@@ -93,24 +95,20 @@ class ExactReTf(Transformation):
        # since elements of "match.groups()" can be None, mypy is wrong.
        groups: Sequence[Optional[str]] = [match[0]] + list(match.groups())

-        locals_dir: Dict[str, Union[str, int, float]] = {}
+        locals_dir: dict[str, str | int | float] = {}
        for i, group in enumerate(groups):
            if group is None:
                continue

            locals_dir[f"g{i}"] = group

-            try:
+            with contextlib.suppress(ValueError):
                locals_dir[f"i{i}"] = int(group)
-            except ValueError:
-                pass

-            try:
+            with contextlib.suppress(ValueError):
                locals_dir[f"f{i}"] = float(group)
-            except ValueError:
-                pass

-        named_groups: Dict[str, str] = match.groupdict()
+        named_groups: dict[str, str] = match.groupdict()
        for name, capture in named_groups.items():
            locals_dir[name] = capture

@@ -208,7 +206,7 @@ class Line:

    @property
    def rest(self) -> str:
-        return self.line[self.index:]
+        return self.line[self.index :]

    def peek(self, amount: int = 1) -> str:
        return self.rest[:amount]
@@ -228,7 +226,7 @@ class Line:
        self.expect(string)
        return value

-    def one_of(self, parsers: List[Callable[[], T]], description: str) -> T:
+    def one_of(self, parsers: list[Callable[[], T]], description: str) -> T:
        for parser in parsers:
            index = self.index
            try:
@@ -315,7 +313,7 @@ def parse_left(line: Line) -> str:
        return parse_str(line)


-def parse_right(line: Line) -> Union[str, Ignore]:
+def parse_right(line: Line) -> str | Ignore:
    c = line.peek()
    if c in QUOTATION_MARKS:
        return parse_quoted_str(line)
@@ -327,21 +325,27 @@ def parse_right(line: Line) -> Union[str, Ignore]:


 def parse_arrow_name(line: Line) -> str:
-    return line.one_of([
-        lambda: line.expect("exact-re"),
-        lambda: line.expect("exact"),
-        lambda: line.expect("name-re"),
-        lambda: line.expect("name"),
-        lambda: line.expect("re"),
-        lambda: line.expect(""),
-    ], "Expected arrow name")
+    return line.one_of(
+        [
+            lambda: line.expect("exact-re"),
+            lambda: line.expect("exact"),
+            lambda: line.expect("name-re"),
+            lambda: line.expect("name"),
+            lambda: line.expect("re"),
+            lambda: line.expect(""),
+        ],
+        "Expected arrow name",
+    )


 def parse_arrow_head(line: Line) -> ArrowHead:
-    return line.one_of([
-        lambda: line.expect_with(">>", ArrowHead.SEQUENCE),
-        lambda: line.expect_with(">", ArrowHead.NORMAL),
-    ], "Expected arrow head")
+    return line.one_of(
+        [
+            lambda: line.expect_with(">>", ArrowHead.SEQUENCE),
+            lambda: line.expect_with(">", ArrowHead.NORMAL),
+        ],
+        "Expected arrow head",
+    )


 def parse_eol(line: Line) -> None:
@@ -413,12 +417,12 @@ class Transformer:

    def transform(self, path: PurePath) -> Optional[PurePath]:
        for i, (line, tf) in enumerate(self._tfs):
-            log.explain(f"Testing rule {i+1}: {line}")
+            log.explain(f"Testing rule {i + 1}: {line}")

            try:
                result = tf.transform(path)
            except Exception as e:
-                log.warn(f"Error while testing rule {i+1}: {line}")
+                log.warn(f"Error while testing rule {i + 1}: {line}")
                log.warn_contd(str(e))
                continue

--- a/PFERD/utils.py
+++ b/PFERD/utils.py
@@ -2,11 +2,13 @@ import asyncio
 import getpass
 import sys
 import threading
+import traceback
 from abc import ABC, abstractmethod
+from collections.abc import Callable
 from contextlib import AsyncExitStack
 from pathlib import Path, PurePath
 from types import TracebackType
-from typing import Any, Callable, Dict, Generic, Optional, Type, TypeVar
+from typing import Any, Generic, Optional, TypeVar
 from urllib.parse import parse_qs, urlencode, urlsplit, urlunsplit

 import bs4
@@ -79,7 +81,7 @@ def url_set_query_param(url: str, param: str, value: str) -> str:
    return urlunsplit((scheme, netloc, path, new_query_string, fragment))


-def url_set_query_params(url: str, params: Dict[str, str]) -> str:
+def url_set_query_params(url: str, params: dict[str, str]) -> str:
    """
    Sets multiple query parameters in an url, overwriting existing ones.
    """
@@ -105,17 +107,31 @@ def fmt_real_path(path: Path) -> str:
    return repr(str(path.absolute()))


+def sanitize_path_name(name: str) -> str:
+    return name.replace("/", "-").replace("\\", "-").strip()
+
+
 class ReusableAsyncContextManager(ABC, Generic[T]):
    def __init__(self) -> None:
        self._active = False
        self._stack = AsyncExitStack()
+        self._create_stacktrace = traceback.format_stack()
+        self._enter_stacktraces = []

    @abstractmethod
    async def _on_aenter(self) -> T:
        pass

    async def __aenter__(self) -> T:
+        self._enter_stacktraces.append(traceback.format_stack())
+
        if self._active:
+            print("Context manager was already active. Created at:")
+            print("".join(self._create_stacktrace))
+            print("\n== Previous __aenter__ calls")
+            for i, stacktrace in enumerate(self._enter_stacktraces, start=1):
+                print(f"\n-- __aenter__ call #{i} at:")
+                print("".join(stacktrace))
            raise RuntimeError("Nested or otherwise concurrent usage is not allowed")

        self._active = True
@@ -124,21 +140,23 @@ class ReusableAsyncContextManager(ABC, Generic[T]):
        # See https://stackoverflow.com/a/13075071
        try:
            result: T = await self._on_aenter()
-        except:  # noqa: E722 do not use bare 'except'
+            return result
+        except:
            if not await self.__aexit__(*sys.exc_info()):
                raise
-
-        return result
+            raise

    async def __aexit__(
-            self,
-            exc_type: Optional[Type[BaseException]],
-            exc_value: Optional[BaseException],
-            traceback: Optional[TracebackType],
+        self,
+        exc_type: Optional[type[BaseException]],
+        exc_value: Optional[BaseException],
+        traceback: Optional[TracebackType],
    ) -> Optional[bool]:
        if not self._active:
            raise RuntimeError("__aexit__ called too many times")

+        self._enter_stacktraces.pop()
+
        result = await self._stack.__aexit__(exc_type, exc_value, traceback)
        self._active = False
        return result
--- a/PFERD/version.py
+++ b/PFERD/version.py
@@ -1,2 +1,2 @@
 NAME = "PFERD"
-VERSION = "3.6.0"
+VERSION = "3.8.3"
--- a/README.md
+++ b/README.md
@@ -17,7 +17,7 @@ Binaries for Linux, Windows and Mac can be downloaded directly from the

 ### With pip

-Ensure you have at least Python 3.9 installed. Run the following command to
+Ensure you have at least Python 3.11 installed. Run the following command to
 install PFERD or upgrade it to the latest version:

 ```
--- a/flake.lock
+++ b/flake.lock
@@ -2,16 +2,16 @@
  "nodes": {
    "nixpkgs": {
      "locked": {
-        "lastModified": 1708979614,
-        "narHash": "sha256-FWLWmYojIg6TeqxSnHkKpHu5SGnFP5um1uUjH+wRV6g=",
+        "lastModified": 1760725957,
+        "narHash": "sha256-tdoIhL/NlER290HfSjOkgi4jfmjeqmqrzgnmiMtGepE=",
        "owner": "NixOS",
        "repo": "nixpkgs",
-        "rev": "b7ee09cf5614b02d289cd86fcfa6f24d4e078c2a",
+        "rev": "81b927b14b7b3988334d5282ef9cba802e193fe1",
        "type": "github"
      },
      "original": {
        "owner": "NixOS",
-        "ref": "nixos-23.11",
+        "ref": "nixos-25.05",
        "repo": "nixpkgs",
        "type": "github"
      }
--- a/flake.nix
+++ b/flake.nix
@@ -2,7 +2,7 @@
  description = "Tool for downloading course-related files from ILIAS";

  inputs = {
-    nixpkgs.url = "github:NixOS/nixpkgs/nixos-23.11";
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-25.05";
  };

  outputs = { self, nixpkgs }:
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -12,7 +12,7 @@ dependencies = [
  "certifi>=2021.10.8"
 ]
 dynamic = ["version"]
-requires-python = ">=3.9"
+requires-python = ">=3.11"

 [project.scripts]
 pferd = "PFERD.__main__:main"
@@ -20,23 +20,33 @@ pferd = "PFERD.__main__:main"
 [tool.setuptools.dynamic]
 version = {attr = "PFERD.version.VERSION"}

-[tool.flake8]
-max-line-length = 110
+[tool.ruff]
+line-length = 110

-[tool.isort]
-line_length = 110
+[tool.ruff.lint]
+select = [
+    # pycodestyle
+    "E",
+    # Pyflakes
+    "F",
+    # pyupgrade
+    "UP",
+    # flake8-bugbear
+    "B",
+    # flake8-simplify
+    "SIM",
+    # isort
+    "I",
+]
+ignore = [
+  "UP045",
+  "SIM114",
+  "B023"
+]

-[tool.autopep8]
-max_line_length = 110
-in-place = true
-recursive = true
-
-[tool.mypy]
-disallow_any_generics = true
-disallow_untyped_defs = true
-disallow_incomplete_defs = true
-no_implicit_optional = true
-warn_unused_ignores = true
-warn_unreachable = true
-show_error_context = true
-ignore_missing_imports = true
+[dependency-groups]
+dev = [
+    "pyinstaller>=6.16.0",
+    "pyright>=1.1.406",
+    "ruff>=0.14.1",
+]
--- a/scripts/build
+++ b/scripts/build
@@ -2,4 +2,4 @@

 set -e

-pyinstaller --onefile pferd.py
+uv run pyinstaller --onefile pferd.py
--- a/scripts/check
+++ b/scripts/check
@@ -2,5 +2,5 @@

 set -e

-mypy .
-flake8 PFERD
+uv run pyright .
+uv run ruff check
--- a/scripts/format
+++ b/scripts/format
@@ -2,5 +2,4 @@

 set -e

-autopep8 .
-isort .
+uv run ruff format
--- a/uv.lock
+++ b/uv.lock
Author	SHA1	Message	Date
I-Al-Istannen	4eab927899	Save stacktraces in context manager and print on error	2025-12-09 17:01:24 +01:00
I-Al-Istannen	e246053de2	Crawl the info tab of courses again This got lost in a refactor	2025-12-02 22:37:32 +01:00
I-Al-Istannen	3f5637366e	Sanitize `/` in kit-ipd heading hierarchy	2025-10-30 20:19:37 +01:00
I-Al-Istannen	3453bbc991	Add basic auth to KIT-IPD crawler	2025-10-29 13:11:34 +01:00
I-Al-Istannen	bd7b384e8f	Manually set event loop on windows The behaviour of get_event_loop changed in 3.14 and no longer creates one. Instead, it will crash.	2025-10-28 11:47:28 +01:00
randomNumber101	6353571eb4	Added Ilias configuration for HHU Duesseldorf to Congig file Closes #125	2025-10-19 16:43:54 +02:00
I-Al-Istannen	1e56976b9f	Update nix flake.lock	2025-10-19 16:31:16 +02:00
I-Al-Istannen	bb0d68da65	Switch to pyright	2025-10-19 16:28:53 +02:00
I-Al-Istannen	c1c78673aa	Switch to uv	2025-10-19 16:27:54 +02:00
I-Al-Istannen	ebcfb2a2f3	Fix some typing errors It seems like the type hints have gotten better :)	2025-10-19 16:27:54 +02:00
I-Al-Istannen	5646e933fd	Ignore reformat in git blame	2025-10-19 15:48:29 +02:00
I-Al-Istannen	6e563134b2	Fix ruff errors	2025-10-19 15:48:16 +02:00
I-Al-Istannen	2cf0e060ed	Reformat and switch to ruff	2025-10-19 15:45:49 +02:00
I-Al-Istannen	ee4625be78	Hardcode max line length in scripts/check	2025-10-19 15:08:29 +02:00
I-Al-Istannen	f6c713d621	Fix mypy errors	2025-10-19 15:08:21 +02:00
I-Al-Istannen	207af51aa4	Include description in internet-shortcut links	2025-07-27 20:13:05 +02:00
I-Al-Istannen	3755f593ff	Update nix flake to 25.05	2025-07-01 14:33:11 +02:00
I-Al-Istannen	465f8b28c0	Bump version to 3.8.3	2025-07-01 14:28:30 +02:00
I-Al-Istannen	27e69af2f3	Update changelog for `8caad00`	2025-07-01 14:26:10 +02:00
Christian Schliz	56e3065950	Document usage of pilot.ilias.studium.kit.edu (#111 )	2025-05-30 17:13:45 +02:00
Mr. Pine	549ce6cce9	Ignore unavailable elements (#119 )	2025-05-28 17:04:57 +02:00
I-Al-Istannen	34564cedb4	Add support for link collections	2025-05-27 16:25:59 +02:00
I-Al-Istannen	2b0d20a1f6	Fix crawling of exercises with instructions We do not want a second path and the instruction field has an identical link...	2025-05-26 14:42:38 +02:00
PinieP	8caad0008d	Fix check for nonexistent `ilias_url` command attribute to `base_url` (#113 )	2025-05-05 22:05:54 +02:00
I-Al-Istannen	77a23265a9	Bump version to 3.8.2	2025-04-29 17:55:57 +02:00
I-Al-Istannen	4c230ef6dd	Fix exercise crawling	2025-04-25 13:45:57 +02:00
Nikolas Heise	b305e1ce23	Fix login using the native ilias login form	2025-04-23 16:08:45 +02:00
I-Al-Istannen	bdf17f5c87	Ignore wikis	2025-04-23 16:03:37 +02:00
I-Al-Istannen	77fce7daf8	Bump version to 3.8.1	2025-04-17 11:22:35 +02:00
I-Al-Istannen	653bf139f0	Fix encoding of descriptions and force images to light mode	2025-04-16 10:52:18 +02:00
I-Al-Istannen	3f60638d33	Bump version to 3.8.0	2025-04-16 00:47:05 +02:00
I-Al-Istannen	b97b6fae6b	Update minimum Python version to 3.11	2025-04-15 21:35:20 +02:00
I-Al-Istannen	477234ad0d	Support ILIAS 9	2025-04-15 21:35:20 +02:00
I-Al-Istannen	63f25277b0	Fix crawling of empty forum threads	2025-03-09 23:44:25 +01:00
I-Al-Istannen	c8eff04ae0	Make thread titles link to original ILIAS thread	2025-02-19 16:23:20 +01:00
I-Al-Istannen	edc482cdf4	Internalize images in forum threads	2025-02-19 16:23:20 +01:00
I-Al-Istannen	72cd0f77e2	Prettify forum thread exports Co-authored-by: Tim <me@scriptim.dev>	2025-02-19 16:23:20 +01:00
I-Al-Istannen	be175f9347	Download only new/updated forum threads	2025-02-19 16:16:37 +01:00
I-Al-Istannen	ba2833dba5	Crawl all threads in a forum Before this patch the row count was unconditionally changed to 800. This patch tries to detect how many rows the forum has and then fetches this amount, if it is larger than 800.	2025-02-19 12:19:33 +01:00
I-Al-Istannen	2f0e792670	Increase default http timeout to 30 Otherwise larger forums will fail to download in time	2025-02-19 12:19:13 +01:00
I-Al-Istannen	5f88539f7e	Fix page size increase for forum threads	2025-02-19 12:19:11 +01:00
I-Al-Istannen	bd9d7efe64	"Fix" mypy errors Thank you mypy, very cool. These types make things so much better. They don't just complicate everything and don't really help because they can not detect that an element queried by a tag is no navigable string...	2025-02-19 12:15:41 +01:00
Aurelia	16a2dd5b15	fix: totp	2025-02-19 12:15:41 +01:00
I-Al-Istannen	678283d341	Use Python facilities to convert paths to file:// urls	2024-11-15 00:09:11 +01:00
I-Al-Istannen	287173b0b1	Bump version to 3.7.0	2024-11-13 20:38:27 +01:00
I-Al-Istannen	712217e959	Handle groups in cards	2024-11-11 12:53:08 +01:00
I-Al-Istannen	6dda4c55a8	Add doctype header to forum threads This should fix mimetype detection on most systems and is more relevant now that the report is clickable	2024-11-05 18:36:21 +01:00
PinieP	596b6a7688	Add support for non-KIT shibboleth login (#98 ) Co-authored-by: Mr-Pine <git@mr-pine.de> Co-authored-by: I-Al-Istannen <I-Al-Istannen@users.noreply.github.com>	2024-11-05 18:30:34 +01:00
Tim	5983200247	Treat headings as folders in kit-ipd crawler (#99 )	2024-11-04 23:53:48 +01:00
Tim	26e802d88b	Add clickable links to file names in the printed report (#100 ) Co-authored-by: I-Al-Istannen <i-al-istannen@users.noreply.github.com>	2024-11-04 00:32:32 +01:00
I-Al-Istannen	f5c4e82816	Delay ilias loop detection after transform This allows users to filter out duplicated elements and suppress the warning.	2024-11-02 22:46:51 +01:00
I-Al-Istannen	f5273f7ca0	Collapse ilias url crawling into normal page crawling	2024-11-02 22:46:51 +01:00
I-Al-Istannen	fa71a9f44f	Add support for mob videos in page descriptions	2024-10-28 20:35:30 +01:00
I-Al-Istannen	81d6ff53c4	Respect row flex in descriptions	2024-10-28 19:41:03 +01:00
I-Al-Istannen	d7a2b6e019	Delete videos from course descriptions	2024-10-28 19:41:03 +01:00
I-Al-Istannen	71c65e89d1	Internalize images in course descriptions	2024-10-28 19:41:03 +01:00
I-Al-Istannen	c1046498e7	Fix download of links without a target URL They are now downloaded as links to the empty url.	2024-10-28 19:41:03 +01:00
I-Al-Istannen	8fbd1978af	Fix crawling of nested courses	2024-10-28 18:52:27 +01:00
Tim	739dd95850	Use Last-Modified and ETag headers to determine KIT-IPD file versions (#95 ) Co-authored-by: I-Al-Istannen <i-al-istannen@users.noreply.github.com>	2024-10-27 19:03:47 +01:00
I-Al-Istannen	c54c3bcfa1	Fix crawling of favorites	2024-10-27 10:50:59 +01:00