De-duplicate element names in ILIAS crawler

This prevents any conflicts caused by multiple files with the same name.
Conflicts may still arise due to transforms, but that is out of our
control and a user error.

PFERD/crawl/ilias/kit_ilias_html.py

@@ -461,3 +461,55 @@ def _tomorrow() -> date:
 
 def _sanitize_path_name(name: str) -> str:
     return name.replace("/", "-").replace("\\", "-").strip()
+
+
+def deduplicate_element_names(elements: List[IliasPageElement]) -> List[IliasPageElement]:
+    """
+    De-duplicates element names by appending an incrementing number to later elements:
+      test.pdf
+      test.pdf
+    would result in
+      test.pdf
+      test_1.pdf
+
+    It is also space-aware:
+      "te st.pdf"
+      "te st.pdf"
+    would result in
+      "tes st.pdf"
+      "tes st 1.pdf"
+    """
+    known_names = dict()
+    result_elements = []
+
+    for element in elements:
+        # This file is new - add it and mark its name as used
+        if element.name not in known_names:
+            known_names[element.name] = 1
+            result_elements.append(element)
+            continue
+
+        # This file is a duplicate. Find a suitable suffix
+        current_counter = known_names[element.name]
+        adjusted_element = _append_number(element, current_counter)
+        # increment the counter so the next duplicate does not conflict
+        known_names[element.name] += 1
+        # also block the new name, so another file with the *renamed* name gets renamed as well
+        known_names[adjusted_element.name] = 1
+
+        result_elements.append(adjusted_element)
+
+    return result_elements
+
+
+def _append_number(element: IliasPageElement, number: int) -> IliasPageElement:
+    extension_index = element.name.rfind(".")
+    suffix = f" {number}" if " " in element.name else f"_{number}"
+    if extension_index < 0:
+        new_name = element.name + suffix
+    else:
+        new_name = element.name[:extension_index] + suffix + element.name[extension_index:]
+
+    return IliasPageElement(
+        element.type, element.url, new_name, element.mtime, element.description
+    )

PFERD/crawl/ilias/kit_ilias_web_crawler.py

@@ -15,7 +15,7 @@ from ...utils import fmt_path, soupify, url_set_query_param
 from ..crawler import CrawlError, CrawlWarning, anoncritical
 from ..http_crawler import HttpCrawler, HttpCrawlerSection
 from .file_templates import link_template_plain, link_template_rich
-from .kit_ilias_html import IliasElementType, IliasPage, IliasPageElement
+from .kit_ilias_html import IliasElementType, IliasPage, IliasPageElement, deduplicate_element_names
 
 TargetType = Union[str, int]
 
@@ -214,6 +214,7 @@ class KitIliasWebCrawler(HttpCrawler):
 
         # Fill up our task list with the found elements
         await gather_elements()
+        elements = deduplicate_element_names(elements)
         tasks = [self._handle_ilias_element(PurePath("."), element) for element in elements]
 
         # And execute them
@@ -240,6 +241,7 @@ class KitIliasWebCrawler(HttpCrawler):
 
         # Fill up our task list with the found elements
         await gather_elements()
+        elements = deduplicate_element_names(elements)
         tasks = [self._handle_ilias_element(path, element) for element in elements]
 
         # And execute them