pferd/PFERD/crawlers/ilias/kit_ilias_web_crawler.py

import asyncio
import re
from pathlib import PurePath
# TODO In Python 3.9 and above, AsyncContextManager is deprecated
from typing import Any, Awaitable, Callable, Dict, Optional, Set, TypeVar, Union

import aiohttp
from bs4 import BeautifulSoup, Tag

from PFERD.authenticators import Authenticator
from PFERD.config import Config
from PFERD.crawler import CrawlerSection, CrawlWarning, HttpCrawler, anoncritical
from PFERD.output_dir import Redownload
from PFERD.utils import soupify, url_set_query_param

from .file_templates import link_template_plain, link_template_rich
from .kit_ilias_html import IliasElementType, IliasPage, IliasPageElement

TargetType = Union[str, int]


class KitIliasWebCrawlerSection(CrawlerSection):

    def target(self) -> TargetType:
        target = self.s.get("target")
        if not target:
            self.missing_value("target")

        if re.fullmatch(r"\d+", target):
            # Course id
            return int(target)
        if target == "desktop":
            # Full personal desktop
            return target
        if target.startswith("https://ilias.studium.kit.edu"):
            # ILIAS URL
            return target

        self.invalid_value("target", target, "Should be <course id | desktop | kit ilias URL>")

    def tfa_auth(self, authenticators: Dict[str, Authenticator]) -> Optional[Authenticator]:
        value = self.s.get("tfa_auth")
        if not value:
            return None

        auth = authenticators.get(f"auth:{value}")
        if auth is None:
            self.invalid_value("auth", value, "No such auth section exists")
        return auth

    def link_file_redirect_delay(self) -> int:
        return self.s.getint("link_file_redirect_delay", fallback=-1)

    def link_file_use_plaintext(self) -> bool:
        return self.s.getboolean("link_file_plain_text", fallback=False)


_DIRECTORY_PAGES: Set[IliasElementType] = set([
    IliasElementType.EXERCISE,
    IliasElementType.FOLDER,
    IliasElementType.MEETING,
    IliasElementType.VIDEO_FOLDER,
    IliasElementType.VIDEO_FOLDER_MAYBE_PAGINATED,
])

AWrapped = TypeVar("AWrapped", bound=Callable[..., Awaitable[None]])


def _iorepeat(attempts: int) -> Callable[[AWrapped], AWrapped]:
    def decorator(f: AWrapped) -> AWrapped:
        async def wrapper(self: "HttpCrawler", *args: Any, **kwargs: Any) -> None:
            for _ in range(attempts - 1):
                try:
                    await f(self, *args, **kwargs)
                    return
                except aiohttp.ContentTypeError:  # invalid content type
                    raise CrawlWarning("ILIAS returned an invalid content type")
                except aiohttp.TooManyRedirects:
                    raise CrawlWarning("Got stuck in a redirect loop")
                except aiohttp.ClientPayloadError:  # encoding or not enough bytes
                    pass
                except aiohttp.ClientConnectionError:  # e.g. timeout, disconnect, resolve failed, etc.
                    pass

            await f(self, *args, **kwargs)
        return wrapper  # type: ignore
    return decorator


class KitIliasWebCrawler(HttpCrawler):
    def __init__(
            self,
            name: str,
            section: KitIliasWebCrawlerSection,
            config: Config,
            authenticators: Dict[str, Authenticator]
    ):
        super().__init__(name, section, config)

        self._shibboleth_login = KitShibbolethLogin(
            section.auth(authenticators),
            section.tfa_auth(authenticators)
        )
        self._base_url = "https://ilias.studium.kit.edu"

        self._target = section.target()
        self._link_file_redirect_delay = section.link_file_redirect_delay()
        self._link_file_use_plaintext = section.link_file_use_plaintext()

    async def crawl(self) -> None:
        if isinstance(self._target, int):
            await self._crawl_course(self._target)
        elif self._target == "desktop":
            await self._crawl_desktop()
        else:
            await self._crawl_url(self._target)

        if self.error_free:
            await self.cleanup()

    async def _crawl_course(self, course_id: int) -> None:
        # Start crawling at the given course
        root_url = url_set_query_param(
            self._base_url + "/goto.php", "target", f"crs_{course_id}"
        )

        await self._crawl_url(root_url, expected_id=course_id)

    async def _crawl_desktop(self) -> None:
        await self._crawl_url(self._base_url)

    async def _crawl_url(self, url: str, expected_id: Optional[int] = None) -> None:
        tasks = []

        async with self.crawl_bar(PurePath("Root element")):
            soup = await self._get_page(url)

            if expected_id is not None:
                perma_link_element: Tag = soup.find(id="current_perma_link")
                if not perma_link_element or "crs_" not in perma_link_element.get("value"):
                    # TODO: Properly handle error
                    raise RuntimeError(
                        "Invalid course id? I didn't find anything looking like a course!")

            # Duplicated code, but the root page is special - we want to void fetching it twice!
            page = IliasPage(soup, url, None)
            for child in page.get_child_elements():
                tasks.append(self._handle_ilias_element(PurePath("."), child))

        await asyncio.gather(*tasks)

    async def _handle_ilias_page(self, url: str, parent: IliasPageElement, path: PurePath) -> None:
        # We might not want to crawl this directory-ish page.
        # This is not in #handle_element, as the download methods check it themselves and therefore
        # would perform this check twice - messing with the explain output
        if not self.should_crawl(path):
            return

        tasks = []
        async with self.crawl_bar(path):
            soup = await self._get_page(url)
            page = IliasPage(soup, url, parent)

            for child in page.get_child_elements():
                tasks.append(self._handle_ilias_element(path, child))

        await asyncio.gather(*tasks)

    @anoncritical
    @_iorepeat(3)
    async def _handle_ilias_element(self, parent_path: PurePath, element: IliasPageElement) -> None:
        element_path = PurePath(parent_path, element.name)

        if element.type == IliasElementType.FILE:
            await self._download_file(element, element_path)
        elif element.type == IliasElementType.FORUM:
            # TODO: Delete
            print(f"Skipping forum [green]{element_path}[/]")
        elif element.type == IliasElementType.LINK:
            await self._download_link(element, element_path)
        elif element.type == IliasElementType.VIDEO:
            await self._download_file(element, element_path)
        elif element.type == IliasElementType.VIDEO_PLAYER:
            await self._download_video(element, element_path)
        elif element.type in _DIRECTORY_PAGES:
            await self._handle_ilias_page(element.url, element, element_path)
        else:
            # TODO: Proper exception
            raise RuntimeError(f"Unknown type: {element.type!r}")

    async def _download_link(self, element: IliasPageElement, element_path: PurePath) -> None:
        dl = await self.download(element_path, mtime=element.mtime)
        if not dl:
            return

        async with self.download_bar(element_path):
            export_url = element.url.replace("cmd=calldirectlink", "cmd=exportHTML")
            async with self.session.get(export_url) as response:
                html_page: BeautifulSoup = soupify(await response.read())
                real_url: str = html_page.select_one("a").get("href").strip()

            async with dl as sink:
                content = link_template_plain if self._link_file_use_plaintext else link_template_rich
                content = content.replace("{{link}}", real_url)
                content = content.replace("{{name}}", element.name)
                content = content.replace("{{description}}", str(element.description))
                content = content.replace("{{redirect_delay}}", str(self._link_file_redirect_delay))
                sink.file.write(content.encode("utf-8"))
                sink.done()

    async def _download_video(self, element: IliasPageElement, element_path: PurePath) -> None:
        # Videos will NOT be redownloaded - their content doesn't really change and they are chunky
        dl = await self.download(element_path, mtime=element.mtime, redownload=Redownload.NEVER)
        if not dl:
            return

        async with self.download_bar(element_path) as bar:
            page = IliasPage(await self._get_page(element.url), element.url, element)
            real_element = page.get_child_elements()[0]

            async with dl as sink, self.session.get(real_element.url) as resp:
                if resp.content_length:
                    bar.set_total(resp.content_length)

                async for data in resp.content.iter_chunked(1024):
                    sink.file.write(data)
                    bar.advance(len(data))

                sink.done()

    async def _download_file(self, element: IliasPageElement, element_path: PurePath) -> None:
        dl = await self.download(element_path, mtime=element.mtime)
        if not dl:
            return

        async with self.download_bar(element_path) as bar:
            async with dl as sink, self.session.get(element.url) as resp:
                if resp.content_length:
                    bar.set_total(resp.content_length)

                async for data in resp.content.iter_chunked(1024):
                    sink.file.write(data)
                    bar.advance(len(data))

                sink.done()

    async def _get_page(self, url: str, retries_left: int = 3) -> BeautifulSoup:
        # This function will retry itself a few times if it is not logged in - it won't handle
        # connection errors
        if retries_left < 0:
            # TODO: Proper exception
            raise RuntimeError("Get page failed too often")
        print(url, "retries left", retries_left)
        async with self.session.get(url) as request:
            soup = soupify(await request.read())
            if self._is_logged_in(soup):
                return soup

        await self._shibboleth_login.login(self.session)

        return await self._get_page(url, retries_left - 1)

    @staticmethod
    def _is_logged_in(soup: BeautifulSoup) -> bool:
        # Normal ILIAS pages
        userlog = soup.find("li", {"id": "userlog"})
        if userlog is not None:
            return True
        # Video listing embeds do not have complete ILIAS html. Try to match them by
        # their video listing table
        video_table = soup.find(
            recursive=True,
            name="table",
            attrs={"id": lambda x: x is not None and x.startswith("tbl_xoct")}
        )
        if video_table is not None:
            return True
        # The individual video player wrapper page has nothing of the above.
        # Match it by its playerContainer.
        if soup.select_one("#playerContainer") is not None:
            return True
        return False


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 = "https://ilias.studium.kit.edu/Shibboleth.sso/Login"
        data = {
            "sendLogin": "1",
            "idp_selection": "https://idp.scc.kit.edu/idp/shibboleth",
            "target": "/shib_login.php",
            "home_organization_selection": "Mit KIT-Account anmelden",
        }
        soup: BeautifulSoup = await _post(sess, url, data)

        # 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 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 = "https://ilias.studium.kit.edu/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:
            raise RuntimeError("No 'tfa_auth' present but you use two-factor authentication!")

        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"]

        # 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
        }
        return _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())