From 1620fc15d1d21989fb38d9f3596cdf03f8535ff5 Mon Sep 17 00:00:00 2001
From: Jan-Hendrik Willms <tleilax+studip@gmail.com>
Date: Sun, 22 Mar 2026 16:13:59 +0100
Subject: implement logic that may collapse list, fixes #6380

---
 app/controllers/course/overview.php             |  4 +-
 lib/classes/CourseDateList.php                  |  4 +-
 resources/assets/javascripts/bootstrap/lists.js | 57 +++++++++++++++++++++++++
 resources/assets/javascripts/entry-base.js      |  1 +
 templates/dates/course_date_list.php            | 13 +++++-
 5 files changed, 76 insertions(+), 3 deletions(-)
 create mode 100644 resources/assets/javascripts/bootstrap/lists.js

diff --git a/app/controllers/course/overview.php b/app/controllers/course/overview.php
index 4325de8..e87417e 100644
--- a/app/controllers/course/overview.php
+++ b/app/controllers/course/overview.php
@@ -67,7 +67,9 @@ class Course_OverviewController extends AuthenticatedController
             $this->next_date   = $this->course->getNextDate();
             $this->first_date  = $this->course->getFirstDate();
             $show_link         = $GLOBALS["perm"]->have_studip_perm('autor', $this->course_id) && $this->course->isToolActive('schedule');
-            $this->times_rooms = $this->course->getAllDatesInSemester()->toHtml();
+            $this->times_rooms = $this->course->getAllDatesInSemester()->toHtml(
+                as_collapsible_list: true
+            );
 
             //Load lecturers:
             $lecturers = $this->course->getMembersWithStatus('dozent');
diff --git a/lib/classes/CourseDateList.php b/lib/classes/CourseDateList.php
index cb1c504..02261e0 100644
--- a/lib/classes/CourseDateList.php
+++ b/lib/classes/CourseDateList.php
@@ -180,7 +180,8 @@ class CourseDateList implements Stringable
     public function toHtml(
         bool $group_by_rooms = false,
         bool $with_room_names = false,
-        bool $with_cancelled_dates = false
+        bool $with_cancelled_dates = false,
+        bool $as_collapsible_list = false
     ) : string {
         if ($this->isEmpty()) {
             return _('Die Zeiten der Veranstaltung stehen nicht fest.');
@@ -230,6 +231,7 @@ class CourseDateList implements Stringable
         } else {
             $template = $GLOBALS['template_factory']->open('dates/course_date_list');
             $template->with_room_names = $with_room_names;
+            $template->as_collapsible_list = $as_collapsible_list;
             $template->collection = $this;
         }
         $template->with_cancelled_dates = $with_cancelled_dates;
diff --git a/resources/assets/javascripts/bootstrap/lists.js b/resources/assets/javascripts/bootstrap/lists.js
new file mode 100644
index 0000000..ac7b85c
--- /dev/null
+++ b/resources/assets/javascripts/bootstrap/lists.js
@@ -0,0 +1,57 @@
+import {$gettext} from "@/assets/javascripts/lib/gettext";
+
+(() => {
+    let uniqueId = 0;
+
+    STUDIP.ready(() => {
+        document.querySelectorAll('.collapsible-list').forEach(list => {
+            if (!list.matches('ol,ul')) {
+                console.error('Not applicable for anything else than ol/ul lists');
+            }
+
+            const data = list.dataset;
+
+            if (data.collapsibleListInitialized !== undefined) {
+                return;
+            }
+
+            data.collapsibleListInitialized = true;
+
+            const label = data.label ?? $gettext('Einträge');
+            const max = Number.parseInt(data.collapseAfter ?? 5, 10);
+            const items = Array.from(list.children);
+            const hiddenItems = items.slice(max);
+            const hiddenCount = hiddenItems.length;
+
+            if (hiddenCount === 0) {
+                return;
+            }
+
+            const id = list.getAttribute('id') ?? `collapsable-list-${uniqueId++}`;
+            list.setAttribute('id', id);
+
+            const button = Object.assign(document.createElement('button'), {
+                className: 'as-link',
+                textContent: '',
+                type: 'button',
+            });
+            button.setAttribute('aria-controls', id);
+
+            const update = (collapsed) => {
+                button.textContent = collapsed
+                    ? $gettext('%{count} weitere %{label} anzeigen', {count: hiddenCount, label})
+                    : $gettext('weniger %{label} anzeigen', {label});
+                button.setAttribute('aria-expanded', collapsed ? 'false' : 'true');
+                hiddenItems.forEach(li => li.toggleAttribute('hidden', collapsed));
+            };
+
+            update(true);
+
+            button.addEventListener('click', () => {
+                update(button.getAttribute('aria-expanded') === 'true');
+            });
+
+            list.after(button);
+        });
+    });
+})();
diff --git a/resources/assets/javascripts/entry-base.js b/resources/assets/javascripts/entry-base.js
index ad114f1..b4f807c 100644
--- a/resources/assets/javascripts/entry-base.js
+++ b/resources/assets/javascripts/entry-base.js
@@ -15,6 +15,7 @@ import "./jquery-bundle.js"
 import "./init.js"
 import "./bootstrap/responsive.js"
 import "./bootstrap/vue.js"
+import "./bootstrap/lists.js"
 
 import "./studip-ui.js"
 import "./bootstrap/fullscreen.js"
diff --git a/templates/dates/course_date_list.php b/templates/dates/course_date_list.php
index bcc9eb7..5f2fd56 100644
--- a/templates/dates/course_date_list.php
+++ b/templates/dates/course_date_list.php
@@ -3,14 +3,25 @@
  * @var CourseDateList $collection
  * @var bool $with_room_names
  * @var bool $with_cancelled_dates
+ * @var bool $as_collapsible_list
  *
  * @var SeminarCycleDate $regular_date
  * @var CourseDate $single_date
  * @var CourseExDate $cancelled_date
  */
 ?>
+<?php
+$html_attributes = HTMLAttributes::from([
+    'class' => 'list-unstyled',
+]);
+
+if ($as_collapsible_list) {
+    $html_attributes['class'] = 'collapsible-list';
+    $html_attributes['data-label'] = _('Termine');
+}
+?>
 <? if (!$collection->isEmpty()) : ?>
-    <ul class="list-unstyled">
+    <ul <?= $html_attributes ?>>
         <? foreach ($collection->getRegularDates() as $regular_date) : ?>
             <li>
                 <?= $regular_date->toString($with_room_names ? 'long-start' : 'long-start-without-room', true) ?>
-- 
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