Implement an IliasPage

This allows PFERD to semantically understand ILIAS HTML and is the
foundation for the ILIAS crawler. This patch extends the ILIAS crawler
to crawl the personal desktop and print the elements on it.

PFERD/crawlers/ilias.py

@@ -1,9 +1,15 @@
+import json
+import re
 from configparser import SectionProxy
+from dataclasses import dataclass, field
+from datetime import datetime
+from enum import Enum
 from pathlib import PurePath
-from typing import Any, Dict, Optional
+from typing import Any, Dict, List, Optional
+from urllib.parse import urljoin, urlparse
 
 import aiohttp
-from bs4 import BeautifulSoup
+from bs4 import BeautifulSoup, Tag
 from PFERD.utils import soupify
 
 from ..authenticators import Authenticator
@@ -41,6 +47,330 @@ class IliasCrawlerSection(CrawlerSection):
         return auth
 
 
+class IliasElementType(Enum):
+    EXERCISE = "exercise"
+    FILE = "file"
+    FOLDER = "folder"
+    FORUM = "forum"
+    LINK = "link"
+    MEETING = "meeting"
+    VIDEO = "video"
+    VIDEO_PLAYER = "video_player"
+    VIDEO_FOLDER = "video_folder"
+    VIDEO_FOLDER_MAYBE_PAGINATED = "video_folder_maybe_paginated"
+
+
+@dataclass
+class IliasPageElement:
+    type: IliasElementType
+    url: str
+    name: str
+    mtime: Optional[datetime] = None
+    query_parameter: Dict[str, str] = field(default_factory=dict)
+
+
+class IliasPage:
+
+    def __init__(self, soup: BeautifulSoup, _page_url: str, source_element: Optional[IliasPageElement]):
+        self._soup = soup
+        self._page_url = _page_url
+        self._page_type = source_element.type if source_element else None
+        self._source_name = source_element.name if source_element else ""
+
+    def get_child_elements(self) -> List[IliasPageElement]:
+        """
+        Return all child page elements you can find here.
+        """
+        if self._is_video_player():
+            return self._player_to_video()
+        if self._is_video_listing():
+            return self._find_video_entries()
+        return self._find_normal_entries()
+
+    def _is_video_player(self) -> bool:
+        return "paella_config_file" in str(self._soup)
+
+    def _is_video_listing(self) -> bool:
+        if self._soup.find(id="headerimage"):
+            element: Tag = self._soup.find(id="headerimage")
+            if "opencast" in element.attrs["src"].lower():
+                return True
+        return False
+
+    def _player_to_video(self) -> List[IliasPageElement]:
+        # Fetch the actual video page. This is a small wrapper page initializing a javscript
+        # player. Sadly we can not execute that JS. The actual video stream url is nowhere
+        # on the page, but defined in a JS object inside a script tag, passed to the player
+        # library.
+        # We do the impossible and RegEx the stream JSON object out of the page's HTML source
+        regex: re.Pattern[str] = re.compile(
+            r"({\"streams\"[\s\S]+?),\s*{\"paella_config_file", re.IGNORECASE
+        )
+        json_match = regex.search(str(self._soup))
+
+        if json_match is None:
+            print(f"Could not find json stream info for {self._page_url!r}")
+            return []
+        json_str = json_match.group(1)
+
+        # parse it
+        json_object = json.loads(json_str)
+        # and fetch the video url!
+        video_url = json_object["streams"][0]["sources"]["mp4"][0]["src"]
+        return [IliasPageElement(IliasElementType.VIDEO, video_url, self._source_name)]
+
+    def _find_video_entries(self) -> List[IliasPageElement]:
+        # ILIAS has three stages for video pages
+        # 1. The initial dummy page without any videos. This page contains the link to the listing
+        # 2. The video listing which might be paginated
+        # 3. An unpaginated video listing (or at least one that includes 800 videos)
+        #
+        # We need to figure out where we are.
+
+        video_element_table: Tag = self._soup.find(
+            name="table", id=re.compile(r"tbl_xoct_.+")
+        )
+
+        if video_element_table is None:
+            # We are in stage 1
+            # The page is actually emtpy but contains the link to stage 2
+            content_link: Tag = self._soup.select_one("#tab_series a")
+            url: str = self._abs_url_from_link(content_link)
+            query_params = {"limit": "800", "cmd": "asyncGetTableGUI", "cmdMode": "asynch"}
+            return [IliasPageElement(
+                IliasElementType.VIDEO_FOLDER_MAYBE_PAGINATED, url, "", query_parameter=query_params
+            )]
+
+        is_paginated = self._soup.find(id=re.compile(r"tab_page_sel.+")) is not None
+
+        if is_paginated and not self._page_type == IliasElementType.VIDEO_FOLDER:
+            # We are in stage 2 - try to break pagination
+            return self._find_video_entries_paginated()
+
+        return self._find_video_entries_no_paging()
+
+    def _find_video_entries_paginated(self) -> List[IliasPageElement]:
+        table_element: Tag = self._soup.find(name="table", id=re.compile(r"tbl_xoct_.+"))
+
+        if table_element is None:
+            # TODO: Properly log this
+            print(
+                "Could not increase elements per page (table not found)."
+                " Some might not be crawled!"
+            )
+            return self._find_video_entries_no_paging()
+
+        id_match = re.match(r"tbl_xoct_(.+)", table_element.attrs["id"])
+        if id_match is None:
+            # TODO: Properly log this
+            print(
+                "Could not increase elements per page (table id not found)."
+                " Some might not be crawled!"
+            )
+            return self._find_video_entries_no_paging()
+
+        table_id = id_match.group(1)
+
+        query_params = {f"tbl_xoct_{table_id}_trows": "800",
+                        "cmd": "asyncGetTableGUI", "cmdMode": "asynch"}
+        return [IliasPageElement(
+            IliasElementType.VIDEO_FOLDER, self._page_url, "", query_parameter=query_params
+        )]
+
+    def _find_video_entries_no_paging(self) -> List[IliasPageElement]:
+        """
+        Crawls the "second stage" video page. This page contains the actual video urls.
+        """
+        # Video start links are marked with an "Abspielen" link
+        video_links: List[Tag] = self._soup.findAll(
+            name="a", text=re.compile(r"\s*Abspielen\s*")
+        )
+
+        results: List[IliasPageElement] = []
+
+        # TODO: Sadly the download button is currently broken, so never do that
+        for link in video_links:
+            results.append(self._listed_video_to_element(link))
+
+        return results
+
+    def _listed_video_to_element(self, link: Tag) -> IliasPageElement:
+        # The link is part of a table with multiple columns, describing metadata.
+        # 6th child (1 indexed) is the modification time string
+        modification_string = link.parent.parent.parent.select_one(
+            "td.std:nth-child(6)"
+        ).getText().strip()
+        modification_time = datetime.strptime(modification_string, "%d.%m.%Y - %H:%M")
+
+        title = link.parent.parent.parent.select_one("td.std:nth-child(3)").getText().strip()
+        title += ".mp4"
+
+        video_name: str = _sanitize_path_name(title)
+
+        video_url = self._abs_url_from_link(link)
+
+        return IliasPageElement(IliasElementType.VIDEO_PLAYER, video_url, video_name, modification_time)
+
+    def _find_normal_entries(self) -> List[IliasPageElement]:
+        result: List[IliasPageElement] = []
+
+        # Fetch all links and throw them to the general interpreter
+        links: List[Tag] = self._soup.select("a.il_ContainerItemTitle")
+
+        for link in links:
+            abs_url = self._abs_url_from_link(link)
+            element_name = _sanitize_path_name(link.getText())
+            element_type = self._find_type_from_link(element_name, link, abs_url)
+
+            if not element_type:
+                continue
+            elif element_type == IliasElementType.MEETING:
+                element_path = _sanitize_path_name(self._normalize_meeting_name(element_name))
+            elif element_type == IliasElementType.FILE:
+                result.append(self._file_to_element(element_name, abs_url, link))
+                continue
+
+            result.append(IliasPageElement(element_type, abs_url, element_name, None))
+
+        return result
+
+    def _file_to_element(self, name: str, url: str, link_element: Tag) -> IliasPageElement:
+        # Files have a list of properties (type, modification date, size, etc.)
+        # In a series of divs.
+        # Find the parent containing all those divs, so we can filter our what we need
+        properties_parent: Tag = link_element.findParent(
+            "div", {"class": lambda x: "il_ContainerListItem" in x}
+        ).select_one(".il_ItemProperties")
+        # The first one is always the filetype
+        file_type = properties_parent.select_one("span.il_ItemProperty").getText().strip()
+
+        # The rest does not have a stable order. Grab the whole text and reg-ex the date
+        # out of it
+        all_properties_text = properties_parent.getText().strip()
+        modification_date_match = re.search(
+            r"(((\d+\. \w+ \d+)|(Gestern|Yesterday)|(Heute|Today)|(Morgen|Tomorrow)), \d+:\d+)",
+            all_properties_text
+        )
+        if modification_date_match is None:
+            modification_date = None
+            # TODO: Properly log this
+            print(f"Could not extract start date from {all_properties_text!r}")
+        else:
+            modification_date_str = modification_date_match.group(1)
+            modification_date = demangle_date(modification_date_str)
+
+        # Grab the name from the link text
+        name = _sanitize_path_name(link_element.getText())
+        full_path = name + "." + file_type
+
+        return IliasPageElement(IliasElementType.FILE, url, full_path, modification_date)
+
+    @staticmethod
+    def _find_type_from_link(
+            element_name: str,
+            link_element: Tag,
+            url: str
+    ) -> Optional[IliasElementType]:
+        """
+        Decides which sub crawler to use for a given top level element.
+        """
+        parsed_url = urlparse(url)
+
+        # file URLs contain "target=file"
+        if "target=file_" in parsed_url.query:
+            return IliasElementType.FILE
+
+        # Skip forums
+        if "cmd=showThreads" in parsed_url.query:
+            return IliasElementType.FORUM
+
+        # Everything with a ref_id can *probably* be opened to reveal nested things
+        # video groups, directories, exercises, etc
+        if "ref_id=" in parsed_url.query:
+            return IliasPage._find_type_from_folder_like(link_element, url)
+
+        # TODO: Log this properly
+        print(f"Unknown type: The element was at {str(element_name)!r} and it is {link_element!r})")
+        return None
+
+    @staticmethod
+    def _find_type_from_folder_like(link_element: Tag, url: str) -> Optional[IliasElementType]:
+        """
+        Try crawling something that looks like a folder.
+        """
+        # pylint: disable=too-many-return-statements
+
+        found_parent: Optional[Tag] = None
+
+        # We look for the outer div of our inner link, to find information around it
+        # (mostly the icon)
+        for parent in link_element.parents:
+            if "ilContainerListItemOuter" in parent["class"]:
+                found_parent = parent
+                break
+
+        if found_parent is None:
+            # TODO: Log this properly
+            print(f"Could not find element icon for {url!r}")
+            return None
+
+        # Find the small descriptive icon to figure out the type
+        img_tag: Optional[Tag] = found_parent.select_one("img.ilListItemIcon")
+
+        if img_tag is None:
+            # TODO: Log this properly
+            print(f"Could not find image tag for {url!r}")
+            return None
+
+        if "opencast" in str(img_tag["alt"]).lower():
+            return IliasElementType.VIDEO_FOLDER
+
+        if str(img_tag["src"]).endswith("icon_exc.svg"):
+            return IliasElementType.EXERCISE
+
+        if str(img_tag["src"]).endswith("icon_webr.svg"):
+            return IliasElementType.LINK
+
+        if str(img_tag["src"]).endswith("frm.svg"):
+            return IliasElementType.FORUM
+
+        if str(img_tag["src"]).endswith("sess.svg"):
+            return IliasElementType.MEETING
+
+        return IliasElementType.FOLDER
+
+    @staticmethod
+    def _normalize_meeting_name(meeting_name: str) -> str:
+        """
+        Normalizes meeting names, which have a relative time as their first part,
+        to their date in ISO format.
+        """
+        date_portion_str = meeting_name.split(" - ")[0]
+        date_portion = demangle_date(date_portion_str)
+
+        if not date_portion:
+            return meeting_name
+
+        rest_of_name = meeting_name
+        if rest_of_name.startswith(date_portion_str):
+            rest_of_name = rest_of_name[len(date_portion_str):]
+
+        return datetime.strftime(date_portion, "%Y-%m-%d, %H:%M") + rest_of_name
+
+    def _abs_url_from_link(self, link_tag: Tag) -> str:
+        """
+        Create an absolute url from an <a> tag.
+        """
+        return urljoin(self._page_url, link_tag.get("href"))
+
+def demangle_date(date_str: str) -> Optional[datetime]:
+    return None
+
+
+def _sanitize_path_name(name: str) -> str:
+    return name.replace("/", "-").replace("\\", "-").strip()
+
+
 class IliasCrawler(HttpCrawler):
     def __init__(
             self,
@@ -64,7 +394,9 @@ class IliasCrawler(HttpCrawler):
     async def crawl(self) -> None:
         async with self.crawl_bar(PurePath("/")) as bar:
             soup = await self._get_page(self._base_url)
-            self.print("[green]Gotcha![/]")
+            page = IliasPage(soup, self._base_url, None)
+            for element in page.get_child_elements():
+                self.print(element.name + " " + str(element.type))
 
     async def _get_page(self, url: str, retries_left: int = 3) -> BeautifulSoup:
         if retries_left < 0: