Merge branch 'main' into issue-3911issue-3911

44 files changed, 734 insertions, 842 deletions

diff --git a/resources/assets/javascripts/bootstrap/application.js b/resources/assets/javascripts/bootstrap/application.js
index a9f53df..4ad248f 100644
--- a/resources/assets/javascripts/bootstrap/application.js
+++ b/resources/assets/javascripts/bootstrap/application.js
@@ -353,6 +353,7 @@ jQuery(document).on('click', 'a[data-behaviour~="ajax-toggle"]', function (event
 (function ($) {
     $(document).on('click', 'form[name=course-details] fieldset legend', function () {
         $('#open_variable').attr('value', $(this).parent('fieldset').data('open'));
+        $(this).parent('fieldset').attr('aria-expanded',  $(this).parent('fieldset').attr('aria-expanded') == 'true' ? 'false' : 'true');
     });
 }(jQuery));
 
diff --git a/resources/assets/javascripts/bootstrap/article.js b/resources/assets/javascripts/bootstrap/article.js
index fbfc131..04316f5 100644
--- a/resources/assets/javascripts/bootstrap/article.js
+++ b/resources/assets/javascripts/bootstrap/article.js
@@ -13,6 +13,7 @@
 
         // Open the contentbox
         article.toggleClass('open').removeClass('new');
+        article.attr('aria-expanded', article.attr('aria-expanded') === 'true' ? 'false' : 'true');
     });
 
     // Open closed article contents when location hash matches
diff --git a/resources/assets/javascripts/bootstrap/clipboard.js b/resources/assets/javascripts/bootstrap/clipboard.js
index e525b35..a64a605 100644
--- a/resources/assets/javascripts/bootstrap/clipboard.js
+++ b/resources/assets/javascripts/bootstrap/clipboard.js
@@ -25,7 +25,9 @@ STUDIP.domReady(function () {
 
     jQuery(document).on('click', '.clipboard-remove-button', function (event) {
         event.preventDefault();
-        STUDIP.Dialog.confirm($(this).data('confirm-message'), function() {
+
+        const message = $(this).data('confirm-message');
+        STUDIP.Dialog.confirm(message).done(() => {
             STUDIP.Clipboard.handleRemoveClick(event.target);
         });
     });
@@ -62,10 +64,11 @@ STUDIP.domReady(function () {
         });
     });
 
-    jQuery(document).on('submit', '.clipboard-widget .new-clipboard-form', function (event) {
-        event.preventDefault();
-        STUDIP.Clipboard.handleAddForm(event);
-    });
+    jQuery(document).on(
+        'submit',
+        '.clipboard-widget .new-clipboard-form',
+        STUDIP.Clipboard.handleAddForm
+    );
 
     jQuery(document).on('click', '.clipboard-add-item-button', function (event) {
         event.preventDefault();
diff --git a/resources/assets/javascripts/bootstrap/consultations.js b/resources/assets/javascripts/bootstrap/consultations.js
index ef79d9c..51ffa85 100644
--- a/resources/assets/javascripts/bootstrap/consultations.js
+++ b/resources/assets/javascripts/bootstrap/consultations.js
@@ -10,9 +10,9 @@ $(document).on('click', '.consultation-delete-check:not(.ignore)', event => {
     }
 
     let requests = ids.map(id => {
-        return STUDIP.jsonapi.GET(`consultation-slots/${id}/bookings`).then(result => result.data.length);
+        return STUDIP.jsonapi.withPromises().get(`consultation-slots/${id}/bookings`).then(response => response.data.length);
     });
-    $.when(...requests).done((...results) => {
+    Promise.all(requests).then((...results) => {
         if (results.some(result => result > 0)) {
             $(event.target).addClass('ignore').click().removeClass('ignore');
         } else {
diff --git a/resources/assets/javascripts/bootstrap/contentbox.js b/resources/assets/javascripts/bootstrap/contentbox.js
index 42c5df1..3f05331 100644
--- a/resources/assets/javascripts/bootstrap/contentbox.js
+++ b/resources/assets/javascripts/bootstrap/contentbox.js
@@ -13,5 +13,6 @@ $(document).on('click', 'section.contentbox article header h1 a', function(e) {
 
         // Open the contentbox
         article.toggleClass('open').removeClass('new');
+        article.attr('aria-expanded', article.attr('aria-expanded') === 'true' ? 'false' : 'true');
     }
 });
diff --git a/resources/assets/javascripts/bootstrap/copyable_links.js b/resources/assets/javascripts/bootstrap/copyable_links.js
index 521eae4..b4f6fc6 100644
--- a/resources/assets/javascripts/bootstrap/copyable_links.js
+++ b/resources/assets/javascripts/bootstrap/copyable_links.js
@@ -16,24 +16,8 @@ $(document).on('click', 'a.copyable-link', function (event) {
     document.execCommand('Copy');
     dummy.remove();
 
-    // Show visual hint using a deferred (this way we don't need to
-    // duplicate the functionality in the done() handler)
-    (new Promise((resolve, reject) => {
-        let confirmation = $('<div class="copyable-link-confirmation copyable-link-success">');
-        confirmation.text($gettext('Link wurde kopiert'));
-        confirmation.insertBefore('#content');
-
-        // Resolve deferred when animation has ended or after 2 seconds as a
-        // fail safe
-        let timeout = setTimeout(() => {
-            $(this).parent().off('animationend');
-            resolve(confirmation);
-        }, 1500);
-        $(this).parent().one('animationend', () => {
-            clearTimeout(timeout);
-            resolve(confirmation);
-        });
-    })).then((confirmation, parent) => {
-        confirmation.remove();
-    });
+    STUDIP.eventBus.emit(
+        'push-system-notification',
+        { type: 'success', message: $gettext('Link wurde kopiert') }
+    );
 });
diff --git a/resources/assets/javascripts/bootstrap/forms.js b/resources/assets/javascripts/bootstrap/forms.js
index c34a0c1..7643612 100644
--- a/resources/assets/javascripts/bootstrap/forms.js
+++ b/resources/assets/javascripts/bootstrap/forms.js
@@ -1,4 +1,5 @@
 import { $gettext, $gettextInterpolate } from '../lib/gettext';
+import Report from '../lib/report.js';
 
 // Allow fieldsets to collapse
 $(document).on(
@@ -291,9 +292,12 @@ STUDIP.ready(function () {
                                         url: v.STUDIPFORM_AUTOSAVEURL,
                                         data: params,
                                         type: 'post',
-                                        success() {
-                                            if (v.STUDIPFORM_REDIRECTURL) {
-                                                window.location.href = v.STUDIPFORM_REDIRECTURL
+                                        success(output) {
+                                            if (output === 'STUDIPFORM_STORE_SUCCESS' && v.STUDIPFORM_REDIRECTURL) {
+                                                //The form has been stored successfully:
+                                                window.location.href = v.STUDIPFORM_REDIRECTURL;
+                                            } else if (output !== 'STUDIPFORM_STORE_SUCCESS') {
+                                                Report.error($gettext('Es ist ein Fehler aufgetreten'), output);
                                             }
                                         }
                                     });
diff --git a/resources/assets/javascripts/bootstrap/global_search.js b/resources/assets/javascripts/bootstrap/global_search.js
index 4d0738e..0e179b7 100644
--- a/resources/assets/javascripts/bootstrap/global_search.js
+++ b/resources/assets/javascripts/bootstrap/global_search.js
@@ -27,15 +27,47 @@ STUDIP.domReady(() => {
     // Enlarge search input on focus and show hints.
     $('#globalsearch-input').on('focus', function() {
         STUDIP.GlobalSearch.toggleSearchBar(true, false);
-    });
-
-    // Start search on Enter
-    $('#globalsearch-input').on('keypress', function(e) {
-        if (e.which === 13) {
+    }).on('keypress', (e) => {
+        // Start search on Enter
+        if (e.key === 'Enter') {
             STUDIP.GlobalSearch.doSearch();
             return false;
         }
     });
+    $('#globalsearch-searchbar').on('keydown', function(e) {
+        if (!['ArrowDown', 'ArrowUp'].includes(e.key)) {
+            return;
+        }
+
+        e.preventDefault();
+
+        // Get all possible items
+        const items = $('#globalsearch-list [role=listitem]:visible');
+
+        // Find focussed element
+        const focussed = items.filter(':focus');
+
+        // Get index of focussed element in all items
+        let index = focussed.length > 0 ? items.index(focussed[0]) : null;
+
+        // Move focussed element up or down in items
+        if (e.key === 'ArrowDown') {
+            index = (index ?? -1) + 1;
+        } else {
+            index = (index ?? items.length) - 1;
+        }
+
+        // Clamp index to sane boundaries
+        if (index < 0) {
+            index = 0;
+        } else if (index > items.length - 1) {
+            index = items.length - 1;
+        }
+
+        // Focus new element by index
+        items.get(index).focus();
+    });
+
 
     // Close search on click on page.
     $('#navigation-level-1, #current-page-structure, #main-footer').on('click', function() {
diff --git a/resources/assets/javascripts/bootstrap/resources.js b/resources/assets/javascripts/bootstrap/resources.js
index 8c89b7f..7eb6a68 100644
--- a/resources/assets/javascripts/bootstrap/resources.js
+++ b/resources/assets/javascripts/bootstrap/resources.js
@@ -416,7 +416,7 @@ STUDIP.ready(function () {
                     $("#BookingEndDateInput").prop('defaultValue', $(this).val());
                     $("#BookingEndDateInput").val($(this).val()).trigger('change');
                 }
-                updateRepeatEndSemesterByTimestamp(Math.floor(d / 1000));
+                updateRepeatEndSemesterByTimestamp(d);
             } else if ($(this).attr('id') == 'BookingEndDateInput') {
                 $("#end_date-weekdays span").addClass('invisible');
                 $("#end_date-weekdays #" + day_numer).removeClass('invisible');
@@ -545,38 +545,41 @@ STUDIP.ready(function () {
         }
     );
 
-    function updateRepeatEndSemesterByTimestamp(timestamp, api_url = 'api.php/semesters') {
-        var semester = null;
-        jQuery.ajax(
-            STUDIP.URLHelper.getURL(api_url),
-            {
-                method: 'get',
-                dataType: 'json',
-                success: function (data) {
-                    if (data) {
-                        Object.values(data.collection).forEach(item => {
-                            if (timestamp >= item.begin && timestamp < item.end) {
-                                semester = item;
-                            }
-                        });
-                        if (semester) {
-                            $("#semester_course_name").text(semester.title);
-                            $(".semester-time-option").prop('disabled', false);
-                        } else {
-                            if (data.pagination && data.pagination.links.next != api_url) {
-                                semester = updateRepeatEndSemesterByTimestamp(timestamp, data.pagination.links.next);
-                            } else {
-                                $("#semester_course_name").text('außerhalb definierter Zeiten');
-                                $(".semester-time-option").prop('checked', false);
-                                $(".semester-time-option").prop('disabled', true);
-                                $(".manual-time-option").prop('checked', true);
-                                $(".manual-time-option").trigger('change');
-                            }
-                        }
-                    }
-                }
+    function updateRepeatEndSemesterByTimestamp(timestamp) {
+        (new Promise((resolve, reject) => {
+            const cache = STUDIP.Cache.getInstance('jsonapi');
+            if (cache.has('semesters')) {
+                resolve(cache.get('semesters'));
+            } else {
+                STUDIP.jsonapi.GET('semesters', { data: { page: { limit: 100000 }}})
+                    .done(({data}) => {
+                        cache.set('semesters', data);
+                        resolve(data)
+                    })
+                    .fail(() => {
+                        reject(new Error('Could not load semesters'));
+                    });
+            }
+        })).then(semesters => {
+            const semester = semesters.find(({attributes}) => {
+                return new Date(attributes.start) <= timestamp
+                    && timestamp <= new Date(attributes.end);
+            });
+
+            if (semester) {
+                $('#semester_course_name').text(semester.attributes.title);
+                $('.semester-time-option').prop('disabled', false);
+            } else {
+                $('#semester_course_name').text('außerhalb definierter Zeiten');
+                $('.semester-time-option').prop({
+                    checked: false,
+                    disabled: true
+                });
+                $('.manual-time-option')
+                    .prop('checked', true)
+                    .trigger('change');
             }
-        );
+        });
     }
 
     function updateViewURL(defaultView) {
diff --git a/resources/assets/javascripts/bootstrap/responsive-navigation.js b/resources/assets/javascripts/bootstrap/responsive-navigation.js
index aa81107..ad39d2b 100644
--- a/resources/assets/javascripts/bootstrap/responsive-navigation.js
+++ b/resources/assets/javascripts/bootstrap/responsive-navigation.js
@@ -1,6 +1,6 @@
 import ResponsiveNavigation from '../../../vue/components/responsive/ResponsiveNavigation.vue';
 
-STUDIP.ready(() => {
+STUDIP.domReady(() => {
     STUDIP.Vue.load().then(({ createApp }) => {
         createApp({
             el: '#responsive-menu',
diff --git a/resources/assets/javascripts/bootstrap/search.js b/resources/assets/javascripts/bootstrap/search.js
index 6a0559b..7d4fb76 100644
--- a/resources/assets/javascripts/bootstrap/search.js
+++ b/resources/assets/javascripts/bootstrap/search.js
@@ -2,8 +2,6 @@ STUDIP.domReady(() => {
     var cache = STUDIP.Search.getCache();
     // initially hide all filters except for the semester filter
     $('#reset-search').hide();
-    STUDIP.Search.hideAllFilters();
-    $('div#semester_filter').show();
     STUDIP.Search.setActiveCategory('show_all_categories');
     STUDIP.Search.showActiveFilters(STUDIP.Search.getFilter());
 
diff --git a/resources/assets/javascripts/bootstrap/studip_helper_attributes.js b/resources/assets/javascripts/bootstrap/studip_helper_attributes.js
index c106de3..aea1823 100644
--- a/resources/assets/javascripts/bootstrap/studip_helper_attributes.js
+++ b/resources/assets/javascripts/bootstrap/studip_helper_attributes.js
@@ -276,6 +276,15 @@ $(document).on('click keydown', '[data-toggles]', function (event) {
             $(target).toggle();
         }
 
+        const controls = $(event.currentTarget).attr('aria-controls');
+        if (controls) {
+            // Find elements which control the expanded status of the same element.
+            const elements = $('[aria-controls="' + controls + '"]');
+            const expanded = $(event.currentTarget).attr('aria-expanded') === 'true';
+            // Set the aria-expanded status accordingly.
+            elements.attr('aria-expanded', !expanded);
+        }
+
         event.preventDefault();
     }
 });
diff --git a/resources/assets/javascripts/bootstrap/system-notifications.js b/resources/assets/javascripts/bootstrap/system-notifications.js
new file mode 100644
index 0000000..7a85fcd
--- /dev/null
+++ b/resources/assets/javascripts/bootstrap/system-notifications.js
@@ -0,0 +1,11 @@
+import SystemNotificationManager from '../../../vue/components/SystemNotificationManager.vue';
+
+STUDIP.domReady(() => {
+    document.getElementById('system-notifications')?.classList.add('vueified');
+    STUDIP.Vue.load().then(({ createApp }) => {
+        createApp({
+            el: '#system-notifications',
+            components: { SystemNotificationManager }
+        });
+    });
+});
diff --git a/resources/assets/javascripts/bootstrap/tooltip.js b/resources/assets/javascripts/bootstrap/tooltip.js
deleted file mode 100644
index c84042b..0000000
--- a/resources/assets/javascripts/bootstrap/tooltip.js
+++ /dev/null
@@ -1,67 +0,0 @@
-// Attach global hover handler for tooltips.
-// Applies to all elements having a "data-tooltip" attribute.
-// Tooltip may be provided in the data-attribute itself or by
-// defining a title attribute. The latter is prefered due to
-// the obvious accessibility issues.
-
-var timeout = null;
-
-STUDIP.Tooltip.threshold = 6;
-
-$(document).on('mouseenter mouseleave focusin focusout', '[data-tooltip],.tooltip:has(.tooltip-content)', function(event) {
-    let data = $(this).data();
-
-    const visible = event.type === 'mouseenter' || event.type === 'focusin';
-    const offset = $(this).offset();
-    const x = offset.left + $(this).outerWidth(true) / 2;
-    const y = offset.top;
-    const delay = data.tooltipDelay ?? 300;
-
-    let content;
-    let tooltip;
-
-    if (!data.tooltipObject) {
-        // If tooltip has not yet been created (first hover), obtain it's
-        // contents and create the actual tooltip object.
-        if (!data.tooltip || !$.isPlainObject(data.tooltip)) {
-            content = $('<div/>').text(data.tooltip || $(this).attr('title')).html();
-        } else if (data.tooltip.html !== undefined) {
-            content = data.tooltip.html;
-        } else if (data.tooltip.text !== undefined) {
-            content = data.tooltip.text;
-        } else {
-            throw "Invalid content for tooltip via data";
-        }
-        if (!content) {
-            content = $(this).find('.tooltip-content').remove().html();
-        }
-        $(this).attr('title', null);
-        $(this).attr('data-tooltip', content);
-
-        tooltip = new STUDIP.Tooltip(x, y, content);
-
-        data.tooltipObject = tooltip;
-        $(this).attr('aria-describedby', tooltip.id);
-
-        $(this).on('remove', function() {
-            tooltip.remove();
-        });
-    } else if (visible) {
-        // If tooltip has already been created, update it's position.
-        // This is neccessary if the surrounding content is scrollable AND has
-        // been scrolled. Otherwise the tooltip would appear at it's previous
-        // and now wrong location.
-        data.tooltipObject.position(x, y);
-    }
-
-    if (visible) {
-        $('.studip-tooltip').not(data.tooltipObject).hide();
-        data.tooltipObject.show();
-    } else {
-        timeout = setTimeout(() => data.tooltipObject.hide(), delay);
-    }
-}).on('mouseenter focusin', '.studip-tooltip', () => {
-    clearTimeout(timeout);
-}).on('mouseleave focusout', '.studip-tooltip', function() {
-    $(this).hide();
-});
diff --git a/resources/assets/javascripts/bootstrap/treeview.js b/resources/assets/javascripts/bootstrap/treeview.js
index 998a70e..d132775 100644
--- a/resources/assets/javascripts/bootstrap/treeview.js
+++ b/resources/assets/javascripts/bootstrap/treeview.js
@@ -1,7 +1,8 @@
 import StudipTree from '../../../vue/components/tree/StudipTree.vue'
 
 STUDIP.ready(() => {
-    document.querySelectorAll('[data-studip-tree]').forEach(element => {
+    document.querySelectorAll('[data-studip-tree]:not(.vueified)').forEach(element => {
+        element.classList.add('vueified');
         STUDIP.Vue.load().then(({ createApp }) => {
             createApp({
                 el: element,
diff --git a/resources/assets/javascripts/bootstrap/vue.js b/resources/assets/javascripts/bootstrap/vue.js
index b8c938d..c6816a2 100644
--- a/resources/assets/javascripts/bootstrap/vue.js
+++ b/resources/assets/javascripts/bootstrap/vue.js
@@ -28,27 +28,17 @@ STUDIP.ready(() => {
         });
 
         STUDIP.Vue.load().then(async ({createApp, store}) => {
-            let vm;
             if (config.store) {
                 const storeConfig = await import(`../../../vue/store/${config.store}.js`);
-                console.log('store', storeConfig.default);
 
                 store.registerModule(config.id, storeConfig.default, {root: true});
 
                 Object.keys(data).forEach(command => {
                     store.commit(`${config.id}/${command}`, data[command]);
                 });
-                vm = createApp({components});
-            } else {
-                vm = createApp({data, components});
             }
-            // import myCoursesStore from '../stores/MyCoursesStore.js';
-            //
-            // myCoursesStore.namespaced = true;
-            //
-            // store.registerModule('my-courses', myCoursesStore);
 
-            vm.$mount(this);
+            createApp({components, data}).$mount(this);
         });
 
         $(this).attr('data-vue-app-created', '');
diff --git a/resources/assets/javascripts/bootstrap/wysiwyg.js b/resources/assets/javascripts/bootstrap/wysiwyg.js
index fb158bb..9e18cf8 100644
--- a/resources/assets/javascripts/bootstrap/wysiwyg.js
+++ b/resources/assets/javascripts/bootstrap/wysiwyg.js
@@ -6,8 +6,11 @@ STUDIP.domReady(() => {
     $(document).on('focus blur', '.studip-dialog .ck-editor__editable_inline', function(event) {
         let height = this.clientHeight;
         let editor = this.ckeditorInstance;
-        editor.editing.view.change(writer => {
-            writer.setStyle('height', height + 'px', editor.editing.view.document.getRoot());
+        // this is needed on Chrome, see https://gitlab.studip.de/studip/studip/-/issues/3510
+        setTimeout(() => {
+            editor.editing.view.change(writer => {
+                writer.setStyle('height', height + 'px', editor.editing.view.document.getRoot());
+            });
         });
     });
 
diff --git a/resources/assets/javascripts/chunk-loader.js b/resources/assets/javascripts/chunk-loader.js
index dcd95cc..f372286 100644
--- a/resources/assets/javascripts/chunk-loader.js
+++ b/resources/assets/javascripts/chunk-loader.js
@@ -8,95 +8,100 @@ export const loadScript = function (script_name) {
     });
 };
 
-export const loadChunk = (function () {
-    let mathjax_promise = null;
+let mathjax_promise = null;
 
-    return function (chunk) {
-        let promise = null;
-        switch (chunk) {
+/** This function dynamically loads JS features organized in chunks.
+ *
+ * @param {string} chunk  The name of the chunk to load.
+ * @param {{ silent: boolean }} options Options for loading the chunk.
+ *                                      Pass `{ silent: true }` to supress
+ *                                      error messages.
+ * @return {Promise}
+ */
+export const loadChunk = function (chunk, { silent = false } = {}) {
+    let promise = null;
+    switch (chunk) {
+        case 'code-highlight':
+            promise = import(
+                /* webpackChunkName: "code-highlight" */
+                './chunks/code-highlight'
+            ).then(({ default: hljs }) => {
+                return hljs;
+            });
+            break;
 
-            case 'code-highlight':
-                promise = import(
-                    /* webpackChunkName: "code-highlight" */
-                    './chunks/code-highlight'
-                ).then(({default: hljs}) => {
-                    return hljs;
-                });
-                break;
+        case 'courseware':
+            promise = Promise.all([
+                STUDIP.loadChunk('vue'),
+                import(
+                    /* webpackChunkName: "courseware" */
+                    './chunks/courseware'
+                ),
+            ]).then(([Vue]) => Vue);
+            break;
 
-            case 'courseware':
-                promise = Promise.all([
-                    STUDIP.loadChunk('vue'),
-                    import(
-                        /* webpackChunkName: "courseware" */
-                        './chunks/courseware'
-                    ),
-                ]).then(([Vue]) => Vue);
-                break;
+        case 'chartist':
+            promise = import(
+                /* webpackChunkName: "chartist" */
+                './chunks/chartist'
+            ).then(({ default: Chartist }) => Chartist);
+            break;
 
-            case 'chartist':
-                promise = import(
-                    /* webpackChunkName: "chartist" */
-                    './chunks/chartist'
-                ).then(({ default: Chartist }) => Chartist);
-                break;
+        case 'fullcalendar':
+            promise = import(
+                /* webpackChunkName: "fullcalendar" */
+                './chunks/fullcalendar'
+            );
+            break;
 
-            case 'fullcalendar':
-                promise = import(
-                    /* webpackChunkName: "fullcalendar" */
-                    './chunks/fullcalendar'
-                );
-                break;
+        case 'tablesorter':
+            promise = import(
+                /* webpackChunkName: "tablesorter" */
+                './chunks/tablesorter'
+            );
+            break;
 
-            case 'tablesorter':
-                promise = import(
-                    /* webpackChunkName: "tablesorter" */
-                    './chunks/tablesorter'
-                );
-                break;
-
-            case 'mathjax':
-                if (mathjax_promise === null) {
-                    mathjax_promise = STUDIP.loadScript(
-                        'javascripts/mathjax/MathJax.js?config=TeX-AMS_HTML,default'
-                    ).then(() => {
+        case 'mathjax':
+            if (mathjax_promise === null) {
+                mathjax_promise = STUDIP.loadScript('javascripts/mathjax/MathJax.js?config=TeX-AMS_HTML,default')
+                    .then(() => {
                         (function (origPrint) {
                             window.print = function () {
-                                window.MathJax.Hub.Queue(
-                                    ['Delay', window.MathJax.Callback, 700],
-                                    origPrint
-                                );
+                                window.MathJax.Hub.Queue(['Delay', window.MathJax.Callback, 700], origPrint);
                             };
                         })(window.print);
 
                         return window.MathJax;
-                    }).catch(() => {
-                        console.log('Could not load mathjax')
+                    })
+                    .catch(() => {
+                        throw new Error('Could not load mathjax');
                     });
-                }
-                promise = mathjax_promise;
-                break;
+            }
+            promise = mathjax_promise;
+            break;
 
-            case 'vue':
-                promise = import(
-                    /* webpackChunkName: "vue.js" */
-                    './chunks/vue'
-                );
-                break;
+        case 'vue':
+            promise = import(
+                /* webpackChunkName: "vue.js" */
+                './chunks/vue'
+            );
+            break;
 
-            case 'wysiwyg':
-                promise = import(
-                    /* webpackChunkName: "wysiwyg.js" */
-                    './chunks/wysiwyg'
-                );
-                break;
+        case 'wysiwyg':
+            promise = import(
+                /* webpackChunkName: "wysiwyg.js" */
+                './chunks/wysiwyg'
+            );
+            break;
 
-            default:
-                promise = Promise.reject(new Error(`Unknown chunk: ${chunk}`));
-        }
+        default:
+            promise = Promise.reject(new Error(`Unknown chunk: ${chunk}`));
+    }
 
-        return promise.catch((error) => {
+    return promise.catch((error) => {
+        if (!silent) {
             console.error(`Could not load chunk ${chunk}`, error);
-        });
-    };
-}());
+        }
+        throw error;
+    });
+};
diff --git a/resources/assets/javascripts/chunks/vue.js b/resources/assets/javascripts/chunks/vue.js
index b98cc27..8d506a1 100644
--- a/resources/assets/javascripts/chunks/vue.js
+++ b/resources/assets/javascripts/chunks/vue.js
@@ -39,6 +39,9 @@ Vue.mixin({
         globalOn(...args) {
             eventBus.on(...args);
         },
+        globalOff(...args) {
+            eventBus.off(...args);
+        },
         getStudipConfig: store.getters['studip/getConfig']
     },
 });
diff --git a/resources/assets/javascripts/entry-base.js b/resources/assets/javascripts/entry-base.js
index 73b1aaa..5f88c30 100644
--- a/resources/assets/javascripts/entry-base.js
+++ b/resources/assets/javascripts/entry-base.js
@@ -16,6 +16,8 @@ import "./init.js"
 import "./bootstrap/responsive.js"
 import "./bootstrap/vue.js"
 
+import "./bootstrap/system-notifications.js"
+
 import "./bootstrap/my-courses.js";
 
 import "./studip-ui.js"
@@ -55,7 +57,6 @@ import "./bootstrap/article.js"
 import "./bootstrap/copyable_links.js"
 import "./bootstrap/selection.js"
 import "./bootstrap/data_secure.js"
-import "./bootstrap/tooltip.js"
 import "./bootstrap/lightbox.js"
 import "./bootstrap/application.js"
 import "./bootstrap/global_search.js"
diff --git a/resources/assets/javascripts/init.js b/resources/assets/javascripts/init.js
index 2d592be..1d7d5ac 100644
--- a/resources/assets/javascripts/init.js
+++ b/resources/assets/javascripts/init.js
@@ -38,7 +38,7 @@ import HeaderMagic from './lib/header_magic.js';
 import i18n from './lib/i18n.js';
 import Instschedule from './lib/instschedule.js';
 import InlineEditing from './lib/inline-editing.js';
-import JSONAPI, { jsonapi } from './lib/jsonapi.js';
+import JSONAPI, { jsonapi } from './lib/jsonapi.ts';
 import JSUpdater from './lib/jsupdater.js';
 import Lightbox from './lib/lightbox.js';
 import Markup from './lib/markup.js';
@@ -64,7 +64,6 @@ import register from './lib/register.js';
 import Report from './lib/report.js';
 import Resources from './lib/resources.js';
 import Responsive from './lib/responsive.js';
-import RESTAPI, { api } from './lib/restapi.js';
 import Schedule from './lib/schedule.js';
 import Screenreader from './lib/screenreader.js';
 import Scroll from './lib/scroll.js';
@@ -76,7 +75,6 @@ import Statusgroups from './lib/statusgroups.js';
 import study_area_selection from './lib/study_area_selection.js';
 import Table from './lib/table.js';
 import TableOfContents from './lib/table-of-contents.js';
-import Tooltip from './lib/tooltip.js';
 import Tour from './lib/tour.js';
 import * as Gettext from './lib/gettext';
 import UserFilter from './lib/user_filter.js';
@@ -93,7 +91,6 @@ window.STUDIP = _.assign(window.STUDIP || {}, {
     admin_sem_class,
     AdminCourses,
     Admission,
-    api,
     Arbeitsgruppen,
     Archive,
     Avatar,
@@ -152,7 +149,6 @@ window.STUDIP = _.assign(window.STUDIP || {}, {
     register,
     Report,
     Responsive,
-    RESTAPI,
     Schedule,
     Scroll,
     Screenreader,
@@ -164,7 +160,6 @@ window.STUDIP = _.assign(window.STUDIP || {}, {
     study_area_selection,
     Table,
     TableOfContents,
-    Tooltip,
     Tour,
     URLHelper,
     UserFilter,
diff --git a/resources/assets/javascripts/lib/RestrictedDatesHelper.ts b/resources/assets/javascripts/lib/RestrictedDatesHelper.ts
new file mode 100644
index 0000000..bcc0af2
--- /dev/null
+++ b/resources/assets/javascripts/lib/RestrictedDatesHelper.ts
@@ -0,0 +1,89 @@
+import { jsonapi } from "./jsonapi";
+
+type RestrictedDate = {
+    year: Number,
+    month: Number,
+    day: Number,
+
+    reason: string | null,
+    lock: boolean
+}
+
+class RestrictedDatesHelper
+{
+    static #loadedYears : Number[] = [];
+    static #restrictedDates: RestrictedDate[] = [];
+
+    static isDateRestricted(date: Date, returnBoolean: Boolean = false): RestrictedDate | Boolean {
+        const restrictedDate : RestrictedDate | undefined = this.#restrictedDates.find(item => {
+            return item.year === date.getFullYear()
+                && item.month === date.getMonth() + 1
+                && item.day === date.getDate();
+        });
+
+        if (returnBoolean) {
+            return !!restrictedDate;
+        }
+
+        return restrictedDate ?? this.#convertDate(date, null, false);
+    }
+
+    static async loadRestrictedDatesByYear(year: Number): Promise<void> {
+        if (this.#loadedYears.includes(year)) {
+            return Promise.reject();
+        }
+
+        this.#loadedYears.push(year);
+
+        jsonapi.withPromises().request('holidays', {data: {
+            'filter[year]': year
+        }}).then((response: [] | Object) => {
+            // Since PHP will return an empty object as an array,
+            // we need to check
+            if (Array.isArray(response)) {
+                return;
+            }
+
+            for (const [date, data] of Object.entries(response)) {
+                this.#addRestrictedDate(
+                    new Date(date),
+                    data.holiday,
+                    data.mandatory
+                );
+            }
+        });
+    }
+
+    static #addRestrictedDate(date: Date, reason: string, lock: boolean = true): void {
+        const restricted = this.#convertDate(date, reason, lock);
+
+        this.#restrictedDates = this.#restrictedDates.filter(item => {
+            return item.year !== restricted.year
+                || item.month !== restricted.month
+                || item.day !== restricted.day;
+        });
+
+        this.#restrictedDates.push(restricted);
+    }
+
+    static removeRestrictedDate(date: Date): void {
+        this.#restrictedDates = this.#restrictedDates.filter(item => {
+            return item.year !== date.getFullYear()
+                || item.month !== date.getMonth() + 1
+                || item.day !== date.getDate();
+        });
+    }
+
+    static #convertDate(date: Date, reason: string | null, lock: boolean): RestrictedDate {
+        return {
+            year: date.getFullYear(),
+            month: date.getMonth() + 1,
+            day: date.getDate(),
+
+            reason,
+            lock
+        };
+    }
+}
+
+export default RestrictedDatesHelper;
diff --git a/resources/assets/javascripts/lib/abstract-api.js b/resources/assets/javascripts/lib/abstract-api.js
index eafca85..95ae015 100644
--- a/resources/assets/javascripts/lib/abstract-api.js
+++ b/resources/assets/javascripts/lib/abstract-api.js
@@ -1,5 +1,20 @@
 import Overlay from './overlay.js';
 
+class APIError extends Error
+{
+    static createWithJqXhr(message, jqXhr) {
+        const error = new APIError(message);
+        error.setJqXhr(jqXhr);
+        return error;
+    }
+
+    jqXhr = null;
+
+    setJqXhr(jqXhr) {
+        this.jqXhr = jqXhr;
+    }
+}
+
 class AbstractAPI
 {
     static get supportedMethods() {
@@ -52,6 +67,8 @@ class AbstractAPI
 
         var deferred;
 
+        const request = this.#createRequest(url, options);
+
         if (options.async && this.request_count > 0) {
             // Request should be sent asynchronous after every other request
             // is finished. The configuration for this particular request is
@@ -73,10 +90,10 @@ class AbstractAPI
             this.total_requests += 1;
 
             // Actual request
-            deferred = $.ajax(STUDIP.URLHelper.getURL(`${this.base_url}/${url}`, {}, true), {
+            deferred = $.ajax(request.url, {
                 contentType: options.contentType || 'application/x-www-form-urlencoded; charset=UTF-8',
                 method: options.method.toUpperCase(),
-                data: this.encodeData(options.data, options.method.toUpperCase()),
+                data: this.encodeData(request.data, options.method.toUpperCase()),
                 headers: options.headers
             }).always(() => {
                 // Decrease request counter, remove overlay if neccessary
@@ -93,6 +110,54 @@ class AbstractAPI
             }
         }).promise();
     }
+
+    #createRequest(url, options) {
+        const hasBody = ['post', 'put', 'patch'].includes(options.method.toLowerCase());
+        const query = hasBody ? '' : `?${this.convertDataToRequestParameters(options.data)}`;
+
+        return {
+            url: STUDIP.URLHelper.getURL(`${this.base_url}/${url}${query}`, {}, true),
+            data: hasBody ? options.data : {},
+        };
+    }
+
+    convertDataToRequestParameters(data, prefix = '') {
+        return Object.entries(data).filter(([key, value]) => {
+            return value !== null;
+        }).map(([key, value]) => {
+            const name = prefix ? `${prefix}[${key}]` : `${key}`;
+            if (value.constructor?.name === 'Object') {
+                return this.convertDataToRequestParameters(value, name);
+            } else {
+                return `${name}=${value}`;
+            }
+        }).join('&');
+    }
+
+    withPromises() {
+        return new Proxy(this, {
+            get(target, prop, receiver) {
+                // This will allow http methods to be written as lowercase when called as methods
+                // (e.g. api.patch() instead of api.PATCH())
+                if (target[prop] === undefined && AbstractAPI.supportedMethods.includes(prop.toUpperCase())) {
+                    prop = prop.toUpperCase();
+                }
+
+                // Only handle calls to request methods
+                if (prop !== 'request') {
+                    return Reflect.get(target, prop, receiver);
+                }
+
+                // Return a wrapped promise that handles the deferred
+                return (url, options = {}) => new Promise((resolve, reject) => {
+                    target[prop].apply(target, [url, options]).then(
+                        (response) => resolve(response),
+                        (jqXhr, textStatus, errorThrown) => reject(APIError.createWithJqXhr(errorThrown || textStatus, jqXhr))
+                    );
+                });
+            }
+        })
+    }
 }
 
 // Create shortcut methods for easier access by method
diff --git a/resources/assets/javascripts/lib/activityfeed.js b/resources/assets/javascripts/lib/activityfeed.js
index 74c27f9..12f0bac 100644
--- a/resources/assets/javascripts/lib/activityfeed.js
+++ b/resources/assets/javascripts/lib/activityfeed.js
@@ -6,13 +6,13 @@ const ActivityFeed = {
     maxheight: null,
     filter: null,
 
-    init: function() {
+    init() {
         STUDIP.ActivityFeed.maxheight = parseInt($('#stream-container').css('max-height').replace(/[^-\d.]/g, ''));
 
         STUDIP.ActivityFeed.loadFeed(STUDIP.ActivityFeed.filter);
 
-        $('#stream-container').scroll(function () {
-            var scrollBottom = $('#stream-container').scrollTop() + $('#stream-container').height() + 250;
+        $('#stream-container').scroll(() => {
+            const scrollBottom = $('#stream-container').scrollTop() + $('#stream-container').height() + 250;
 
             if ($('#stream-container').prop('scrollHeight') < scrollBottom) {
                 STUDIP.ActivityFeed.loadFeed(STUDIP.ActivityFeed.filter);
@@ -23,7 +23,7 @@ const ActivityFeed = {
         $(document).on('click', '.provider_circle', function () {
             $(this).parent().parent().children('.activity-content').toggle();
         }).on('click', '#toggle-all-activities,#toggle-user-activities', function () {
-            var toggled = $(this).is(':not(.toggled)');
+            const toggled = $(this).is(':not(.toggled)');
             $(this).toggleClass('toggled', toggled);
 
             STUDIP.ActivityFeed.setToggleStatus();
@@ -32,11 +32,11 @@ const ActivityFeed = {
         });
     },
 
-    getTemplate: _.memoize(function(name) {
-        return _.template($("script." + name).html());
+    getTemplate: _.memoize(name => {
+        return _.template($(`script.${name}`).html());
     }),
 
-    loadFeed: function(filtertype) {
+    loadFeed(filtertype) {
         if (STUDIP.ActivityFeed.user_id === null) {
             console.log('Could not retrieve activities, no valid user id found!');
             return false;
@@ -48,17 +48,18 @@ const ActivityFeed = {
 
         STUDIP.ActivityFeed.polling = true;
 
-        STUDIP.api.GET(['user', STUDIP.ActivityFeed.user_id, 'activitystream'], {
-            data: {
-                filtertype: JSON.stringify(filtertype),
-                scrollfrom: STUDIP.ActivityFeed.scrolledfrom
-            }
-        }).done(function (activities) {
-            var stream        = STUDIP.ActivityFeed.getTemplate('activity_stream');
-            var activity      = STUDIP.ActivityFeed.getTemplate('activity');
-            var activity_urls = STUDIP.ActivityFeed.getTemplate('activity-urls');
-            var num_entries   = Object.keys(activities).length;
-            var lastelem      = $(activities).last();
+        const url = STUDIP.URLHelper.getURL('dispatch.php/activityfeed/load', {
+            filtertype: JSON.stringify(filtertype),
+            scrollfrom: STUDIP.ActivityFeed.scrolledfrom,
+        });
+        fetch(url).then(
+            response => response.json(),
+        ).then(activities => {
+            const stream = STUDIP.ActivityFeed.getTemplate('activity_stream');
+            const activity = STUDIP.ActivityFeed.getTemplate('activity');
+            const activity_urls = STUDIP.ActivityFeed.getTemplate('activity-urls');
+            const num_entries = Object.keys(activities).length;
+            const lastelem = $(activities).last();
 
             if (lastelem[0]) {
                 STUDIP.ActivityFeed.scrolledfrom  = lastelem[0].mkdate;
@@ -79,15 +80,15 @@ const ActivityFeed = {
             if ($('#stream-container').height() < STUDIP.ActivityFeed.maxheight) {
                 STUDIP.ActivityFeed.loadFeed('');
             }
-        }).fail(function () {
-            var template = STUDIP.ActivityFeed.getTemplate('activity-load-error');
+        }).catch(() => {
+            const template = STUDIP.ActivityFeed.getTemplate('activity-load-error');
             STUDIP.ActivityFeed.writeToStream(template());
-        }).always(function () {
+        }).finally(() => {
             STUDIP.ActivityFeed.polling = false;
         });
     },
 
-    writeToStream: function (html) {
+    writeToStream(html) {
         if (STUDIP.ActivityFeed.initial) {
             // replace data in DOM
             $('#stream-container').html('');
@@ -98,9 +99,9 @@ const ActivityFeed = {
         $('#stream-container').append(html);
     },
 
-    setToggleStatus: function() {
-        var show_details = $('#toggle-all-activities').is('.toggled'),
-            show_own     = $('#toggle-user-activities').is('.toggled');
+    setToggleStatus() {
+        const show_details = $('#toggle-all-activities').is('.toggled');
+        const show_own = $('#toggle-user-activities').is('.toggled');
 
         // update toggle status fir activity contents
         $('.activity-content').toggle(show_details);
@@ -109,7 +110,7 @@ const ActivityFeed = {
         $('.activity:has(.provider_circle.right)').toggle(show_own);
     },
 
-    updateFilter: function(filter) {
+    updateFilter(filter) {
         STUDIP.ActivityFeed.filter = filter;
         STUDIP.ActivityFeed.initial = true;
         STUDIP.ActivityFeed.scrolledfrom = Math.floor(Date.now() / 1000);
diff --git a/resources/assets/javascripts/lib/blubber.js b/resources/assets/javascripts/lib/blubber.js
index 3e93985..4e724b4 100644
--- a/resources/assets/javascripts/lib/blubber.js
+++ b/resources/assets/javascripts/lib/blubber.js
@@ -47,6 +47,7 @@ const Blubber = {
                 subscribe: follow,
             });
         }).then(() => {
+            elements.attr('aria-pressed', follow ? 'true' : 'false');
             elements.toggleClass('unfollowed', !follow);
         }).finally(() => {
             elements.removeClass('loading');
diff --git a/resources/assets/javascripts/lib/clipboard.js b/resources/assets/javascripts/lib/clipboard.js
index e5890ab..6fd1489 100644
--- a/resources/assets/javascripts/lib/clipboard.js
+++ b/resources/assets/javascripts/lib/clipboard.js
@@ -1,4 +1,14 @@
-import {$gettext} from './gettext';
+function extractAttribute(node, attribute) {
+    return node.querySelector(`input[name="${attribute}"]`)?.value.trim();
+}
+
+function extractAttributes(node, attributes) {
+    const result = {};
+    for (const key of attributes) {
+        result[key] = extractAttribute(node, key);
+    }
+    return result;
+}
 
 const Clipboard = {
     switchClipboard: function(event) {
@@ -32,32 +42,30 @@ const Clipboard = {
         }
     },
 
-    handleAddForm: function(event) {
-        if (!event) {
-            return false;
-        }
-
+    handleAddForm(event) {
+        event.preventDefault();
 
+        const attributes = extractAttributes(event.target, ['name', 'allowed_item_class']);
 
         //Check if a name is entered in the form:
-        let name_input = jQuery(event.target).find('input[type="text"][name="name"]');
+        const name_input = event.target.querySelector('input[name="name"]');
         if (!name_input) {
             //Something is wrong with the HTML:
             return false;
         }
-        let name = jQuery(name_input).val().trim();
-        if (!name) {
+        if (!attributes.name) {
             //The name field is empty. Why send an empty field?
             return false;
         }
 
-        //Submit the form via AJAX:
-        STUDIP.api.POST(
-            'clipboard/add',
-            {
-                data: jQuery(event.target).serialize()
-            }
-        ).done(STUDIP.Clipboard.add);
+        // Submit the form via AJAX:
+        STUDIP.jsonapi.POST('clipboards', {data: {data: {attributes}}}).done(({data}) => {
+            STUDIP.Clipboard.add({
+                id: data.id,
+                name: data.attributes.name,
+                widget_id: extractAttribute(event.target, 'widget_id')
+            });
+        });
     },
 
     add: function(data) {
@@ -134,11 +142,9 @@ const Clipboard = {
         jQuery(widget_node).find('#clipboard-group-container').removeClass('invisible');
 
         //Call the droppable jQuery method on the new clipboard area:
-        jQuery(clipboard_node).droppable(
-            {
-                drop: STUDIP.Clipboard.handleItemDrop
-            }
-        );
+        jQuery(clipboard_node).droppable({
+            drop: STUDIP.Clipboard.handleItemDrop
+        });
 
         //Clear the text input in the "add clipboard" form:
         jQuery(widget_node).find(
@@ -238,17 +244,19 @@ const Clipboard = {
         }
 
         //Add the item to the clipboard via AJAX:
-        STUDIP.api.POST(
-            'clipboard/' + clipboard_id + '/item',
-            {
+        STUDIP.jsonapi.POST(`clipboards/${clipboard_id}/items`, {
+            data: {
                 data: {
-                    'range_id': range_id,
-                    'range_type': range_type,
-                    'widget_id': widget_id
+                    attributes: { range_id, range_type }
                 }
             }
-        ).done(function(data) {
-            STUDIP.Clipboard.addDroppedItem(data);
+        }).done(({data}) => {
+            STUDIP.Clipboard.addDroppedItem({
+                id: data.id,
+                name: data.attributes.name,
+                range_id: data.attributes.range_id,
+                widget_id
+            });
         });
     },
 
@@ -263,6 +271,7 @@ const Clipboard = {
         let widget = jQuery('#ClipboardWidget_' + response_data['widget_id']);
         let clipboard_id = jQuery(widget).find(".clipboard-selector").val();
 
+
         if (!widget) {
             //The widget with the speicified widget-ID
             //is not present on the current page.
@@ -302,7 +311,6 @@ const Clipboard = {
         jQuery(new_item_node).removeClass('invisible');
 
         let name_column = jQuery(new_item_node).find('td.item-name');
-        console.log(name_column);
         jQuery('<span/>').text(response_data['name']).appendTo(name_column)
         let id_field = jQuery(new_item_node).find("input[name='selected_clipboard_items[]']");
         jQuery(id_field).val(checkbox_id);
@@ -325,25 +333,16 @@ const Clipboard = {
         );
     },
 
-    rename: function(widget_id) {
-         if (!widget_id) {
-            //Required data are missing!
-            return;
-        }
+    rename(widget_id) {
+        const widget = jQuery('#ClipboardWidget_' + widget_id);
+        const clipboard_id = widget.find('.clipboard-selector').val();
+        const name = widget.find('input.clipboard-name').val();
 
-        let widget = jQuery('#ClipboardWidget_' + widget_id);
-        let clipboard_id = jQuery(widget).find(".clipboard-selector").val();
-        let namer = jQuery(widget).find("input.clipboard-name");
-
-        STUDIP.api.PUT(
-            'clipboard/' + clipboard_id,
-            {
-                data: {
-                    name: namer.val()
-                }
-            }
-        ).done(function(data) {
-            STUDIP.Clipboard.update(data, widget_id)
+        STUDIP.jsonapi.PATCH(`clipboards/${clipboard_id}`, {data: {data: {attributes: {name}}}}).done(({data}) => {
+            STUDIP.Clipboard.update({
+                id: data.id,
+                name: data.attributes.name,
+            }, widget_id)
         });
     },
 
@@ -358,7 +357,7 @@ const Clipboard = {
         STUDIP.Clipboard.toggleEditButtons(widget_id);
     },
 
-    remove: function(clipboard_id, widget_id) {
+    remove(clipboard_id, widget_id) {
         if (!clipboard_id || !widget_id) {
             //Required data are missing!
             return;
@@ -427,10 +426,6 @@ const Clipboard = {
     },
 
     handleRemoveClick: function(delete_icon) {
-        if (!delete_icon) {
-            return;
-        }
-
         //Get the data of the clipboard:
         let clipboard_select = jQuery(delete_icon).siblings('.clipboard-selector')[0];
         if (!clipboard_select) {
@@ -444,52 +439,42 @@ const Clipboard = {
             //Another case where something is wrong with the HTML.
             return;
         }
-        let widget_id = jQuery(widget).data('widget_id');
 
-        STUDIP.api.DELETE(
-            'clipboard/' + clipboard_id,
-            {
-                data: {
-                    widget_id: widget_id
-                }
-            }
-        ).done(function() {
+        const widget_id = jQuery(widget).data('widget_id');
+
+        STUDIP.jsonapi.DELETE(`clipboards/${clipboard_id}`).done(() => {
             STUDIP.Clipboard.remove(clipboard_id, widget_id);
         });
     },
 
-    removeItem: function(delete_icon) {
-        if (!delete_icon) {
-            return;
-        }
-
-        //Get the item-ID:
-        let item_html = jQuery(delete_icon).parents('tr');
-        let range_id = jQuery(item_html).data('range_id');
-        let clipboard_element = jQuery(item_html).parents('table');
-        let clipboard_id = jQuery(clipboard_element).data('id');
+    removeItem(delete_icon) {
+        // Get the item-ID:
+        const item_element = jQuery(delete_icon).parents('tr');
+        const range_id = jQuery(item_element).data('range_id');
+        const clipboard_element = jQuery(item_element).parents('table');
+        const clipboard_id = jQuery(clipboard_element).data('id');
 
         if (!range_id || !clipboard_id) {
             //We cannot proceed without the item-ID and the clipboard-ID!
             return;
         }
 
-        STUDIP.api.DELETE(
-            'clipboard/' + clipboard_id + '/item/' + range_id
-        ).done(function() {
+        STUDIP.jsonapi.DELETE(`clipboards/${clipboard_id}/items`, {
+            data: {
+                filter: { range_id }
+            }
+        }).done(() => {
             //Check if the item has siblings:
-            let siblings = jQuery(item_html).siblings();
+            let siblings = item_element.siblings();
             if (siblings.length < 3) {
                 //Only the "no items" element and the template
                 //are siblings of the item.
                 //We must display the "no items" element:
-                jQuery(item_html).siblings(
-                    '.empty-clipboard-message'
-                ).removeClass('invisible');
+                item_element.siblings('.empty-clipboard-message').removeClass('invisible');
                 jQuery("#clipboard-group-container").find('.widget-links').addClass('invisible');
             }
             //Finally remove the item:
-            jQuery(item_html).remove();
+            item_element.remove();
         });
     },
 
diff --git a/resources/assets/javascripts/lib/dialog.js b/resources/assets/javascripts/lib/dialog.js
index b5cab54..8f6e50a 100644
--- a/resources/assets/javascripts/lib/dialog.js
+++ b/resources/assets/javascripts/lib/dialog.js
@@ -386,7 +386,12 @@ Dialog.show = function(content, options = {}) {
                     .before(element);
             }
 
-            $(this).parent().find('.ui-dialog-title').attr('title', options.title);
+            $(this).parent().find('.ui-dialog-title').attr({
+                title: options.title,
+                role: 'heading',
+                'aria-level': 2
+            });
+            $(this).parents('.studip-dialog').attr('aria-modal', 'true');
 
             instance.open = true;
             // Execute scripts
diff --git a/resources/assets/javascripts/lib/extract_callback.js b/resources/assets/javascripts/lib/extract_callback.js
index bf7ac79..a630275 100644
--- a/resources/assets/javascripts/lib/extract_callback.js
+++ b/resources/assets/javascripts/lib/extract_callback.js
@@ -56,8 +56,9 @@ export default function extractCallback(cmd, payload, root = window) {
             }
         }
 
-        if (callback[chunk] === undefined) {
-            throw 'Error: Undefined callback ' + cmd;
+        if (callback === null || callback[chunk] === undefined) {
+            console.log('Error: Undefined callback ' + cmd);
+            return;
         }
 
         if (typeof callback[chunk] === 'function' && parameters !== null) {
diff --git a/resources/assets/javascripts/lib/fullcalendar.js b/resources/assets/javascripts/lib/fullcalendar.js
index 49274f4..5b7d032 100644
--- a/resources/assets/javascripts/lib/fullcalendar.js
+++ b/resources/assets/javascripts/lib/fullcalendar.js
@@ -622,8 +622,13 @@ class Fullcalendar
                     $('.fc-slats tr:odd .fc-widget-content:not(.fc-axis)').remove();
                 }
 
-                STUDIP.api.GET(`semester/${timestamp}/week`).done((data) => {
+                if (document.getElementById('booking-plan-header-semname') === null) {
+                    return;
+                }
 
+                $.getJSON(
+                    STUDIP.URLHelper.getURL(`dispatch.php/resources/ajax/semester_week/${timestamp}`)
+                ).done((data) => {
                     if (data) {
                         $('#booking-plan-header-semname').text(data.semester_name);
                         if (data.sem_week) {
@@ -640,7 +645,7 @@ class Fullcalendar
                         $('#booking-plan-header-semrow').hide();
                         $('#booking-plan-header-semweek-part').hide();
                     }
-            })
+                });
             },
             resourceRender (renderInfo) {
                 if ($(renderInfo.view.context.calendar.el).hasClass('room-group-booking-plan')) {
@@ -731,12 +736,31 @@ class Fullcalendar
             //Get the timestamp:
             let timestamp = changedMoment.getTime() / 1000;
 
-            jQuery('a.resource-bookings-actions').each(function () {
+            jQuery('a.resource-bookings-actions, a.calendar-action').each(function () {
                 const url = new URL(this.href);
-                url.searchParams.set('timestamp', timestamp)
+                url.searchParams.set('timestamp', timestamp.toString())
                 url.searchParams.set('defaultDate', changed_date)
                 this.href = url.toString();
             });
+            jQuery('.sidebar-widget.calendar-action').each(function() {
+                //Each sidebar widget is different. The placement of the defaultDate URL parameter
+                //has to reflect that.
+                jQuery(this).find('button[formaction]').each(function() {
+                    //Modify the formaction attribute:
+                    let url = new URL(jQuery(this).attr('formaction'));
+                    url.searchParams.set('defaultDate', changed_date);
+                    jQuery(this).attr('formaction', url.toString());
+                });
+                jQuery(this).find('form[action]').each(function() {
+                    //Add a hidden input with the defaultDate:
+                    let hidden_input = jQuery(this).find('input[name="defaultDate"]')[0];
+                    if (!hidden_input) {
+                        hidden_input = jQuery('<input type="hidden" name="defaultDate">');
+                        jQuery(this).append(hidden_input);
+                    }
+                    jQuery(hidden_input).val(changed_date);
+                });
+            });
 
             // Now change the URL of the window.
             const url = new URL(window.location.href);
diff --git a/resources/assets/javascripts/lib/global_search.js b/resources/assets/javascripts/lib/global_search.js
index dbd045b..394b7e3 100644
--- a/resources/assets/javascripts/lib/global_search.js
+++ b/resources/assets/javascripts/lib/global_search.js
@@ -9,6 +9,7 @@ const GlobalSearch = {
      */
     toggleSearchBar: function(visible, cleanup) {
         $('#globalsearch-searchbar').toggleClass('is-visible', visible);
+        $('#globalsearch-input').attr('aria-expanded', visible ? 'true' : 'false');
         $('#globalsearch-input').toggleClass('hidden-small-down', !visible);
         $('#globalsearch-icon').toggleClass('hidden-small-down', visible);
         $('#globalsearch-clear').toggleClass('hidden-small-down', !visible);
@@ -70,7 +71,7 @@ const GlobalSearch = {
             // Iterate over each result category.
             $.each(json, function(name, value) {
                 // Create an <article> for category.
-                var category = $(`<article id="globalsearch-${name}">`),
+                var category = $(`<article id="globalsearch-${name}" role="list">`),
                     header = $('<header>').appendTo(category),
                     counter = 0;
 
@@ -96,7 +97,7 @@ const GlobalSearch = {
                 // Process results and create corresponding entries.
                 $.each(value.content, function(index, result) {
                     // Create single result entry.
-                    var single = $('<section>'),
+                    var single = $(`<a href="${result.url}" role="listitem" ${dataDialog}>`),
                         data = $('<div class="globalsearch-result-data">'),
                         details = $('<div class="globalsearch-result-details">');
 
@@ -107,17 +108,17 @@ const GlobalSearch = {
                     // Which result types should be opened via dialog?
                     const openInDialog = ['GlobalSearchFiles', 'GlobalSearchMessages'];
                     var dataDialog = (openInDialog.indexOf(name) >= 0 ? dataDialog = 'data-dialog' : dataDialog = '');
-                    var link = $(`<a href="${result.url}" ${dataDialog}>`).appendTo(single);
+                    //var link = $(`<a href="${result.url}" ${dataDialog}>`).appendTo(single);
 
                     // Optional image...
                     if (result.img !== null) {
-                        $(`<img src="${result.img}">`)
+                        $(`<img src="${result.img}" alt="">`)
                             .wrap('<div class="globalsearch-result-img">')
                             .parent() // Element is now the wrapper
-                            .appendTo(link);
+                            .appendTo(single);
                     }
 
-                    link.append(data);
+                    single.append(data);
 
                     // Name/title
                     $('<div class="globalsearch-result-title">')
@@ -144,7 +145,7 @@ const GlobalSearch = {
                     if (result.date !== null) {
                         $('<div class="globalsearch-result-time">')
                             .html(result.date)
-                            .appendTo(link);
+                            .appendTo(single);
                     }
 
                     // "Expand" attribute for further, result-related search
@@ -178,6 +179,7 @@ const GlobalSearch = {
         GlobalSearch.lastSearch = null;
 
         $('#globalsearch-searchbar').removeClass('is-visible has-value');
+        $('#globalsearch-input').attr('aria-expanded', 'false');
         $('#globalsearch-input').val('');
         $('#globalsearch-results').html('');
         $('#globalsearch-input').focus();
diff --git a/resources/assets/javascripts/lib/header_magic.js b/resources/assets/javascripts/lib/header_magic.js
index f465e7e..a581107 100644
--- a/resources/assets/javascripts/lib/header_magic.js
+++ b/resources/assets/javascripts/lib/header_magic.js
@@ -17,7 +17,7 @@ const scroll = function(scrolltop) {
 const HeaderMagic = {
     enable() {
         fold = $('#navigation-level-1').height();
-        Scroll.addHandler('header', scroll);
+        Scroll.addHandler('header', scroll, true);
     },
     disable() {
         Scroll.removeHandler('header');
diff --git a/resources/assets/javascripts/lib/jsonapi.js b/resources/assets/javascripts/lib/jsonapi.ts
index f3217bc..80176cc 100644
--- a/resources/assets/javascripts/lib/jsonapi.js
+++ b/resources/assets/javascripts/lib/jsonapi.ts
@@ -3,11 +3,11 @@ import AbstractAPI from './abstract-api.js';
 // Actual JSONAPI object
 class JSONAPI extends AbstractAPI
 {
-    constructor(version = 1) {
+    constructor(version: number = 1) {
         super(`jsonapi.php/v${version}`);
     }
 
-    encodeData (data, method) {
+    encodeData (data: any, method: string): any {
         data = super.encodeData(data);
 
         if (['DELETE', 'GET', 'HEAD'].includes(method)) {
@@ -21,11 +21,11 @@ class JSONAPI extends AbstractAPI
         return JSON.stringify(data);
     }
 
-    request (url, options = {}) {
+    request (url: string, options: any = {}) {
         options.contentType = 'application/vnd.api+json';
         return super.request(url, options);
     }
 }
 
 export default JSONAPI;
-export const jsonapi = new JSONAPI();
+export const jsonapi: JSONAPI = new JSONAPI();
diff --git a/resources/assets/javascripts/lib/messages.js b/resources/assets/javascripts/lib/messages.js
index 7ce5328..8e27f8f 100644
--- a/resources/assets/javascripts/lib/messages.js
+++ b/resources/assets/javascripts/lib/messages.js
@@ -252,6 +252,8 @@ const Messages = {
         if (jQuery('#' + name).is(':visible')) {
             jQuery('#' + name)[0].scrollIntoView(false);
         }
+        jQuery('#toggle-' + name)
+            .attr('aria-expanded', jQuery('#toggle-' + name).attr('aria-expanded') !== 'true');
     }
 };
 
diff --git a/resources/assets/javascripts/lib/personal_notifications.js b/resources/assets/javascripts/lib/personal_notifications.js
index 90f1053..392e8b0 100644
--- a/resources/assets/javascripts/lib/personal_notifications.js
+++ b/resources/assets/javascripts/lib/personal_notifications.js
@@ -116,6 +116,11 @@ const PersonalNotifications = {
                     .click(STUDIP.PersonalNotifications.activate);
             }
         }
+
+        // Special handling for personal notifications:
+        $('#notification-container').on('mouseover mouseout', function (event) {
+            $(this).attr('aria-expanded', $(this).attr('aria-expanded') === 'true' ? 'false' : 'true');
+        });
     },
     activate () {
         Promise.resolve(Notification.requestPermission()).then(permission => {
diff --git a/resources/assets/javascripts/lib/questionnaire.js b/resources/assets/javascripts/lib/questionnaire.js
index 2bca8c6..9a89348 100644
--- a/resources/assets/javascripts/lib/questionnaire.js
+++ b/resources/assets/javascripts/lib/questionnaire.js
@@ -86,7 +86,7 @@ const Questionnaire = {
                             }
                             $.post(STUDIP.URLHelper.getURL('dispatch.php/questionnaire/store/' + (this.data.id || '')), {
                                 questionnaire: data,
-                                questions_data: questions,
+                                questions_data: JSON.stringify(questions),
                                 range_type: this.range_type,
                                 range_id: this.range_id
                             }).done(() => {
@@ -112,7 +112,7 @@ const Questionnaire = {
                                 id: id,
                                 questiontype: this.questions[i].questiontype,
                                 internal_name: this.questions[i].internal_name,
-                                questiondata: Object.assign({}, this.questions[i].questiondata)
+                                questiondata: JSON.parse(JSON.stringify(this.questions[i].questiondata)),
                             });
                             this.activeTab = id;
                         },
diff --git a/resources/assets/javascripts/lib/resources.js b/resources/assets/javascripts/lib/resources.js
index 3287b42..6ff4156 100644
--- a/resources/assets/javascripts/lib/resources.js
+++ b/resources/assets/javascripts/lib/resources.js
@@ -50,7 +50,7 @@ class Resources
             jQuery(row_tds[user_td_index]).children('input').removeAttr('disabled');
 
             if (username) {
-                jQuery(row_tds[user_td_index]).append(username);
+                jQuery('<span>').text(username).appendTo(row_tds[user_td_index]);
             } else {
                 jQuery(row_tds[user_td_index]).append('ID ' + user_id);
             }
@@ -60,8 +60,6 @@ class Resources
             }
             jQuery(user_id_input).val(user_id);
 
-            var perm_select = jQuery(row_tds[user_td_index + 1]).children()[0];
-
             if (temp_perms_row) {
                 //Set the time input fields to useful values:
 
@@ -134,22 +132,19 @@ class Resources
             jQuery(table_element).trigger('update');
         };
 
-        STUDIP.api.GET(
-            `user/${user_id}`
-        ).done(function (data) {
-            var username = data.name.family
-                + ', '
-                + data.name.given;
-            if (data.name.prefix) {
-                username += ', ' + data.name.prefix;
+        STUDIP.jsonapi.GET(`users/${user_id}`).done(data => {
+            const attributes = data.data.attributes;
+
+            let username = `${attributes['family-name']}, ${attributes['given-name']}`;
+            if (attributes['name-prefix']) {
+                username += `, ${attributes['name-prefix']}`;
             }
-            if (data.name.suffix) {
-                username += ' ' + data.name.suffix;
+            if (attributes['name-suffix']) {
+                username += ` ${attributes['name-suffix']}`;
             }
-            username += ' (' + data.name.username + ')'
-                + ' (' + data.perms + ')';
+            username += ` (${attributes.username}) (${attributes.permission})`;
             insert_function(user_id, username);
-        }).fail(function () {
+        }).fail(() => {
             insert_function(user_id);
         });
     }
@@ -160,23 +155,13 @@ class Resources
             return;
         }
 
-        STUDIP.api.GET(
-            `course/${course_id}/members`,
-            {
-                data: {
-                    //The limit '0' results in a division by zero.
-                    //Hopefully, the limit is set to a value high enough:
-                    limit: 1000000
-                }
-            }
-        ).done(function (data) {
-            for (var attribute in data.collection) {
-                var user_id = data.collection[attribute].member.id;
+        STUDIP.jsonapi.GET(`courses/${course_id}/memberships`, {data: {page: {limit: 1000000}}}).done(data => {
+            data.data.forEach(membership => {
                 STUDIP.Resources.addUserToPermissionList(
-                    user_id,
+                    membership.relationships.user.data.id,
                     table_element
                 );
-            }
+            });
         });
     }
 
diff --git a/resources/assets/javascripts/lib/restapi.js b/resources/assets/javascripts/lib/restapi.js
deleted file mode 100644
index b6e31df..0000000
--- a/resources/assets/javascripts/lib/restapi.js
+++ /dev/null
@@ -1,12 +0,0 @@
-import AbstractAPI from './abstract-api.js';
-
-// Actual RESTAPI object
-class RESTAPI extends AbstractAPI
-{
-    constructor() {
-        super('api.php');
-    }
-}
-
-export default RESTAPI;
-export const api = new RESTAPI();
diff --git a/resources/assets/javascripts/lib/scroll.js b/resources/assets/javascripts/lib/scroll.js
index a4d24d5..f4ffc66 100644
--- a/resources/assets/javascripts/lib/scroll.js
+++ b/resources/assets/javascripts/lib/scroll.js
@@ -6,49 +6,54 @@
  * Updates/calls to the callback are synchronized to screen refresh by using
  * the animation frame method (which will fallback to a timer based solution).
  */
-var handlers = {};
-var animId = false;
+const handlers = {};
+let animId = false;
 
-var lastTop  = null;
-var lastLeft = null;
-
-function scrollHandler() {
-    var scrollTop = $(document).scrollTop();
-    var scrollLeft = $(document).scrollLeft();
-
-    if (scrollTop !== lastTop || scrollLeft !== lastLeft) {
-        $.each(handlers, function(index, handler) {
-            handler(scrollTop, scrollLeft);
-        });
-
-        lastTop  = scrollTop;
-        lastLeft = scrollLeft;
-    }
-
-    animId = false;
-
-    engageScrollTrigger();
-}
+let lastTop = null;
+let lastLeft = null;
 
 function refresh() {
-    var hasHandlers = !$.isEmptyObject(handlers);
+    const hasHandlers = Object.keys(handlers).length > 0;
     if (!hasHandlers && animId !== false) {
         window.cancelAnimationFrame(animId);
         animId = false;
     } else if (hasHandlers && animId === false) {
-        animId = window.requestAnimationFrame(scrollHandler);
+        animId = window.requestAnimationFrame(() => Scroll.executeHandlers());
     }
 }
 
 function engageScrollTrigger() {
-    $(window).off('scroll.studip-handler');
-    $(window).one('scroll.studip-handler', refresh);
+    window.removeEventListener('scroll', refresh);
+    window.addEventListener('scroll', refresh, {once: true});
 }
 
 const Scroll = {
-    addHandler(index, handler) {
+    executeHandlers(only_these = []) {
+        const scrollTop = document.scrollingElement.scrollTop;
+        const scrollLeft = document.scrollingElement.scrollLeft;
+
+        if (scrollTop !== lastTop || scrollLeft !== lastLeft) {
+            for (const [index, handler] of Object.entries(handlers)) {
+                if (only_these.length === 0 || only_these.includes(index)) {
+                    handler(scrollTop, scrollLeft);
+                }
+            }
+
+            lastTop  = scrollTop;
+            lastLeft = scrollLeft;
+        }
+
+        animId = false;
+
+        engageScrollTrigger();
+    },
+    addHandler(index, handler, immediate = false) {
         handlers[index] = handler;
         engageScrollTrigger();
+
+        if (immediate) {
+            Scroll.executeHandlers([index]);
+        }
     },
     removeHandler(index) {
         delete handlers[index];
diff --git a/resources/assets/javascripts/lib/scroll_to_top.js b/resources/assets/javascripts/lib/scroll_to_top.js
index 2a75402..9b0d3ee 100644
--- a/resources/assets/javascripts/lib/scroll_to_top.js
+++ b/resources/assets/javascripts/lib/scroll_to_top.js
@@ -4,9 +4,9 @@ let fold;
 let was_below_the_fold = false;
 
 const back_to_top = function(scrolltop) {
-    var is_below_the_fold = scrolltop > fold;
+    let is_below_the_fold = scrolltop > fold;
     if (is_below_the_fold !== was_below_the_fold) {
-        $('#scroll-to-top').toggleClass('hide', !is_below_the_fold);
+        document.getElementById('scroll-to-top').classList.toggle('hide', !is_below_the_fold);
         was_below_the_fold = is_below_the_fold;
     }
 };
@@ -23,15 +23,21 @@ const ScrollToTop = {
     },
     disable() {
         Scroll.removeHandler('header');
-        $('#scroll-to-top').addClass('hide');
+        document.getElementById('scroll-to-top').classList.add('hide');
     },
     moveBack() {
-        $('#scroll-to-top').on('click', function(e) {
-            $('html, body').stop().animate({
-                scrollTop: (0)
-            }, 1000, 'easeInOutExpo');
-            e.preventDefault();
+        document.getElementById('scroll-to-top').addEventListener('click', (evt)  => {
+            evt.preventDefault();
+            this.toTop();
         });
+        document.getElementById('scroll-to-top').addEventListener('keypress', (evt) => {
+            if (evt.code === 'Space') {
+                this.toTop();
+            }
+        });
+    },
+    toTop() {
+        window.scroll({top: 0, left: 0, behavior: 'smooth'});
     }
 };
 
diff --git a/resources/assets/javascripts/lib/search.js b/resources/assets/javascripts/lib/search.js
index 5d39f43..f8108cd 100644
--- a/resources/assets/javascripts/lib/search.js
+++ b/resources/assets/javascripts/lib/search.js
@@ -200,7 +200,7 @@ const Search = {
         // Optional image...
         if (result.img !== null) {
             $('<div class="search-result-img hidden-tiny-down">')
-                .append(`<img src="${result.img}">`)
+                .append(`<img src="${result.img}" alt="">`)
                 .appendTo(link);
         }
 
@@ -339,7 +339,8 @@ const Search = {
      * Hide all select filters in the sidebar.
      */
     hideAllFilters: function () {
-        $('div[id$="_filter"]').hide();
+        $('#filter_widget').hide();
+        $('#filter_widget *[id$="_filter"]').hide();
     },
 
     /**
@@ -350,12 +351,11 @@ const Search = {
     showFilter: function (category) {
         var filters = $('#search-results').data('filters');
         STUDIP.Search.hideAllFilters();
-        if (filters && filters[category] !== undefined && category != 'show_all_categories') {
+        if (filters && filters[category] !== undefined && filters[category].length > 0) {
+            $('#filter_widget').show();
             for (let i = 0; i < filters[category].length; i++) {
                 $(`#${filters[category][i]}_filter`).show();
             }
-        } else if (category === 'show_all_categories') {
-            $('#semester_filter').show();
         }
     },
 
@@ -547,7 +547,7 @@ const Search = {
             if (item != 'category') {
                 var value = filter[item];
                 if (value.trim()) {
-                    var name = $(`#${item}_filter .sidebar-widget-header`).text().trim();
+                    var name = $(`#${item}_filter .label-text`).text().trim();
                     var value_text = $(`#${item}_select option:selected`).text().trim();
                     var filterItem = $('<button></button>').addClass('button remove-filter').text(name + ': ' + value_text).attr('data-filter-name', item);
                     filterItem.on('click', function () {
diff --git a/resources/assets/javascripts/lib/tooltip.js b/resources/assets/javascripts/lib/tooltip.js
deleted file mode 100644
index 2cdac27..0000000
--- a/resources/assets/javascripts/lib/tooltip.js
+++ /dev/null
@@ -1,227 +0,0 @@
-import CSS from './css.js';
-
-/**
- * Tooltip library for Stud.IP
- *
- * @author Jan-Hendrik Willms <tleilax+studip@gmail.com>
- * @copyright Stud.IP Core Group 2014
- * @license GPL2 or any later version
- * @since Stud.IP 3.1
- */
-
-let count = 0;
-let threshold = 0;
-
-class Tooltip {
-    static get count() {
-        return count;
-    }
-
-    static set count(value) {
-        count = value;
-    }
-
-    // Threshold used for "edge detection" (imagine a padding along the edges)
-    static get threshold() {
-        return threshold;
-    }
-
-    static set threshold(value) {
-        threshold = value;
-    }
-
-    /**
-     * Returns a new unique id of a tooltip.
-     *
-     * @return {string} Unique id
-     * @static
-     */
-    static getId() {
-        const id = `studip-tooltip-${Tooltip.count}`;
-        Tooltip.count += 1;
-        return id;
-    }
-
-    /**
-     * Constructs a new tooltip at given location with given content.
-     * The applied css class may be changed by the fourth parameter.
-     *
-     * @class
-     * @classdesc Stud.IP tooltips provide an improved layout and handling
-     *            of contents (including html) than the browser's default
-     *            tooltip through title attribute would
-     *
-     * @param {int} x - Horizontal position of the tooltip
-     * @param {int} y - Vertical position of the tooltip
-     * @param {string} content - Content of the tooltip (may be html)
-     * @param {string} css_class - Optional name of the applied css class /
-     *                             defaults to 'studip-tooltip'
-     */
-    constructor(x, y, content, css_class) {
-        // Obtain unique id of the tooltip
-        this.id = Tooltip.getId();
-
-        // Create dom element of the tooltip, apply id and class and attach
-        // to dom
-        this.element = $('<div>');
-        this.element.addClass(css_class || 'studip-tooltip');
-        this.element.attr('id', this.id);
-        this.element.attr('role', 'tooltip');
-        this.element.appendTo('body');
-
-        // Set position and content and paint the tooltip
-        this.position(x, y);
-        this.update(content);
-        this.paint();
-    }
-
-    /**
-     * Translates the arrow(s) under a tooltip using css3 translate
-     * transforms. This is needed at the edges of the screen.
-     * This implies that a current browser is used. The translation could
-     * also be achieved by adjusting margins but that way we would need
-     * to hardcode values into this function since it's a struggle to
-     * obtain the neccessary values from the CSS pseudo selectors in JS.
-     *
-     * Internal, css rules are dynamically created and applied to the current
-     * document by using the methods provided in the file studip-css.js.
-     *
-     * @param {int} x - Horizontal offset
-     * @param {int} y - Vertical offset
-     */
-    translateArrows(x, y, left_arrow = false) {
-        CSS.removeRule(`#${this.id}::before`);
-        CSS.removeRule(`#${this.id}::after`);
-
-        if (x !== 0 || y !== 0) {
-            let before_rule = {
-                transform: `translate(${x}px, ${y}px);`
-            };
-            if (left_arrow) {
-                before_rule.transform = `translate(${x}px, ${y}px) rotate(90deg);`;
-            }
-            let after_rule = before_rule;
-            if (left_arrow) {
-                after_rule['border-width'] = '9px';
-            }
-            CSS.addRule(`#${this.id}::before`, before_rule, ['-ms-', '-webkit-']);
-            CSS.addRule(`#${this.id}::after`, after_rule, ['-ms-', '-webkit-']);
-        }
-    }
-
-    /**
-     * Updates the position of the tooltip.
-     *
-     * @param {int} x - Horizontal position of the tooltip
-     * @param {int} y - Vertical position of the tooltip
-     */
-    position(x, y) {
-        this.x = x;
-        this.y = y;
-    }
-
-    /**
-     * Updates the contents of the tooltip.
-     *
-     * @param {string} content - Content of the tooltip (may be html)
-     */
-    update(content) {
-        this.element.html(content);
-    }
-
-    /**
-     * "Paints" the tooltip. This method actually computes the dimensions of
-     * the tooltips, checks for screen edges and calculates the actual offset
-     * in the current document.
-     * This method is neccessary due to the fact that position and content
-     * can be changed apart from each other.
-     * Thus: Don't forget to repaint after adjusting any of the two.
-     */
-    paint() {
-        const width = this.element.outerWidth(true);
-        const height = this.element.outerHeight(true);
-        const maxWidth = $(document).width();
-        const maxHeight = $(document).height();
-        let x = this.x - width / 2;
-        let y = this.y - height;
-        //The arrow offset is the offset from the bottom right corner of
-        //the tooltip "frame".
-        let arrow_offset_x = 0;
-        let arrow_offset_y = 0;
-        let left_arrow = false;
-
-        if (y < 0) {
-            y = 0;
-            x = this.x + 20;
-            //Put the arrow on the left side and move the tooltip,
-            //if there is still enough place left on the right.
-            left_arrow = true;
-            arrow_offset_y = -height + this.y + 10;
-            if (arrow_offset_y > -20) {
-                y+= arrow_offset_y + 20;
-                arrow_offset_y = -20;
-            }
-            arrow_offset_x = -width / 2 - 8;
-        } else if (y + height > maxHeight) {
-            y = maxHeight - height;
-        }
-
-        if (x < 0) {
-            arrow_offset_x = 0;
-            x = 0;
-        } else if (x + width > maxWidth) {
-            arrow_offset_x = x + width - maxWidth;
-            x = maxWidth - width;
-        }
-        this.translateArrows(arrow_offset_x, arrow_offset_y, left_arrow);
-
-        this.element.css({
-            left: x,
-            top: y
-        });
-    }
-
-    /**
-     * Toggles the visibility of the tooltip. If no state is provided,
-     * the tooltip will be hidden if visible and vice versa. Pretty straight
-     * forward and no surprises here.
-     * This method implicitely calls paint before a tooltip is shown (in case
-     * it was forgotten).
-     *
-     * @param {bool} visible - Optional visibility parameter to set the
-     *                         tooltip to a certain state
-     */
-    toggle(visible) {
-        if (visible) {
-            this.paint();
-        }
-        this.element.toggle(visible);
-    }
-
-    /**
-     * Reveals the tooltip.
-     *
-     * @see Tooltip.toggle
-     */
-    show() {
-        this.toggle(true);
-    }
-
-    /**
-     * Hides the tooltip.
-     *
-     * @see Tooltip.toggle
-     */
-    hide() {
-        this.toggle(false);
-    }
-
-    /**
-     * Removes the tooltip
-     */
-    remove() {
-        this.element.remove();
-    }
-}
-
-export default Tooltip;
diff --git a/resources/assets/javascripts/lib/wysiwyg.js b/resources/assets/javascripts/lib/wysiwyg.js
index f9acb81..47c64d0 100644
--- a/resources/assets/javascripts/lib/wysiwyg.js
+++ b/resources/assets/javascripts/lib/wysiwyg.js
@@ -13,17 +13,17 @@ const wysiwyg = {
 
     isHtml: function isHtml(text) {
         // NOTE keep this function in sync with
-        // Markup::isHtml in Markup.class.php
+        // Markup::isHtml in Markup.php
         return this.hasHtmlMarker(text);
     },
     hasHtmlMarker: function hasHtmlMarker(text) {
         // NOTE keep this function in sync with
-        // Markup::hasHtmlMarker in Markup.class.php
+        // Markup::hasHtmlMarker in Markup.php
         return this.htmlMarkerRegExp.test(text);
     },
     markAsHtml: function markAsHtml(text) {
         // NOTE keep this function in sync with
-        // Markup::markAsHtml in Markup.class.php
+        // Markup::markAsHtml in Markup.php
         if (this.hasHtmlMarker(text) || text.trim() == '') {
             return text; // marker already set, don't set twice
         }
diff --git a/resources/assets/javascripts/mvv.js b/resources/assets/javascripts/mvv.js
index a339624..92dcd68 100644
--- a/resources/assets/javascripts/mvv.js
+++ b/resources/assets/javascripts/mvv.js
@@ -67,10 +67,17 @@ jQuery(function ($) {
     });
 
     $(document).on('click', '.stgfile .remove_attachment', function($event) {
-        STUDIP.MVV.Document.remove_attachment($(this));
+        STUDIP.Dialog.confirm($gettext('Soll die Datei wirklich gelöscht werden?')).done(() => {
+            STUDIP.MVV.Document.remove_attachment(this);
+        });
         return false;
     });
 
+    $(document).on('click', '.stgfile .refresh_attachment', (event) => {
+        STUDIP.MVV.Document.refresh_attachment(event.target);
+        event.preventDefault();
+    });
+
     STUDIP.dialogReady(
         function() {
 
@@ -663,27 +670,55 @@ STUDIP.MVV.Document = {
             })
         }, 100);
     },
-    remove_attachment: function(item) {
-        jQuery.ajax({
-            url: STUDIP.ABSOLUTE_URI_STUDIP + 'dispatch.php/materialien/files/delete_attachment',
-            data: {
-                mvvfile_id: jQuery('#mvvfile_id').val(),
-                fileref_id: item.closest('li')
-                                .find('input[name=document_id]')
-                                .val()
-            },
-            type: 'POST'
+    refresh_attachment(item) {
+        const language = item.closest('button').dataset.language;
+        const document_id = item.closest('.stgfile').querySelector('[name="document_id"]').value;
+
+        const input = document.createElement('input');
+        input.type = 'file';
+        input.hidden = true;
+
+        input.addEventListener('cancel', () => {
+            input.remove();
         });
-        item.parents('td').find('.attachments').toggle();
-        item.closest('li')
-            .fadeOut(300, function() {
-                jQuery(this).remove();
+        input.addEventListener('change', () => {
+            const fd = new FormData();
+            fd.append('file', input.files[0], input.files[0].name);
+            fd.append('mvvfile_id', jQuery('#mvvfile_id').val());
+            fd.append('range_id', jQuery('#range_id').val());
+            fd.append('document_id', document_id);
+            fd.append('file_language', language);
+
+            const statusbar = $('#statusbar_container .statusbar')
+                .first()
+                .clone()
+                .show();
+            statusbar.appendTo('#statusbar_container');
+
+            STUDIP.MVV.Document.upload_file(fd, statusbar, true).then(() => {
+                input.remove();
+            });
+        });
+
+        item.parentNode.after(input);
+        input.click();
+    },
+    remove_attachment(item) {
+        const url = STUDIP.URLHelper.getURL('dispatch.php/materialien/files/delete_attachment', {
+            mvvfile_id: document.getElementById('mvvfile_id').value,
+            fileref_id: item.closest('li').querySelector('input[name=document_id]').value,
+        });
+        $.post(url).done(() => {
+            $(item).closest('td').find('.attachments').toggle();
+            $(item).closest('li').fadeOut(300, function () {
+                this.remove();
                 jQuery('#upload_chooser').show();
             });
+        });
     },
-    upload_from_input: function(input, file_language) {
+    upload_from_input(input, file_language) {
         STUDIP.MVV.Document.upload_files(input.files, file_language);
-        jQuery(input).val('');
+        input.value = '';
     },
     fileIDQueue: 1,
     upload_files: function(files, file_language) {
@@ -701,82 +736,94 @@ STUDIP.MVV.Document = {
             STUDIP.MVV.Document.upload_file(fd, statusbar);
         }
     },
-    upload_file: function(formdata, statusbar) {
-        $.ajax({
-            xhr: function() {
-                var xhrobj = $.ajaxSettings.xhr();
-                if (xhrobj.upload) {
-                    xhrobj.upload.addEventListener(
-                        'progress',
-                        function(event) {
-                            var percent = 0;
-                            var position = event.loaded || event.position;
-                            var total = event.total;
-                            if (event.lengthComputable) {
-                                percent = Math.ceil((position / total) * 100);
-                            }
-                            //Set progress
-                            statusbar.find('.progress').css({ 'min-width': percent + '%', 'max-width': percent + '%' });
-                            statusbar
-                                .find('.progresstext')
-                                .text(percent === 100 ? jQuery('#upload_finished').text() : percent + '%');
-                        },
-                        false
-                    );
+    upload_file(formdata, statusbar, update = false) {
+        return new Promise((resolve, reject) => {
+            $.ajax({
+                xhr() {
+                    var xhrobj = $.ajaxSettings.xhr();
+                    if (xhrobj.upload) {
+                        xhrobj.upload.addEventListener(
+                            'progress',
+                            function(event) {
+                                var percent = 0;
+                                var position = event.loaded || event.position;
+                                var total = event.total;
+                                if (event.lengthComputable) {
+                                    percent = Math.ceil((position / total) * 100);
+                                }
+                                //Set progress
+                                statusbar.find('.progress').css({ 'min-width': percent + '%', 'max-width': percent + '%' });
+                                statusbar
+                                    .find('.progresstext')
+                                    .text(percent === 100 ? jQuery('#upload_finished').text() : percent + '%');
+                            },
+                            false
+                        );
+                    }
+                    return xhrobj;
+                },
+                url: STUDIP.ABSOLUTE_URI_STUDIP + 'dispatch.php/materialien/files/upload_attachment',
+                type: 'POST',
+                contentType: false,
+                processData: false,
+                cache: false,
+                data: formdata,
+                dataType: 'json'
+            }).done((data) => {
+                const language = formdata.get('file_language');
+
+                statusbar.find('.progress').css({ 'min-width': '100%', 'max-width': '100%' });
+                var file = jQuery('#fileselector_'+formdata.get('file_language')).find('.stgfiles > .stgfile')
+                    .first()
+                    .clone();
+                file.find('.name').text(data.name);
+                if (data.size < 1024) {
+                    file.find('.size').text(data.size + 'B');
                 }
-                return xhrobj;
-            },
-            url: STUDIP.ABSOLUTE_URI_STUDIP + 'dispatch.php/materialien/files/upload_attachment',
-            type: 'POST',
-            contentType: false,
-            processData: false,
-            cache: false,
-            data: formdata,
-            dataType: 'json'
-        })
-        .done(function(data) {
-            statusbar.find('.progress').css({ 'min-width': '100%', 'max-width': '100%' });
-            var file = jQuery('#fileselector_'+formdata.get('file_language')).find('.stgfiles > .stgfile')
-                .first()
-                .clone();
-            file.find('.name').text(data.name);
-            if (data.size < 1024) {
-                file.find('.size').text(data.size + 'B');
-            }
-            if (data.size > 1024 && data.size < 1024 * 1024) {
-                file.find('.size').text(Math.floor(data.size / 1024) + 'KB');
-            }
-            if (data.size > 1024 * 1024 && data.size < 1024 * 1024 * 1024) {
-                file.find('.size').text(Math.floor(data.size / 1024 / 1024) + 'MB');
-            }
-            if (data.size > 1024 * 1024 * 1024) {
-                file.find('.size').text(Math.floor(data.size / 1024 / 1024 / 1024) + 'GB');
-            }
-            file.find('.icon').html(data.icon);
-            file.find('input[name=document_id]').attr('value', data.document_id);
-            jQuery('#fileviewer_'+formdata.get('file_language')).find('.stgfiles').append(file);
-            jQuery('#fileselector_'+formdata.get('file_language')).toggle();
-            jQuery('#fileselector_'+formdata.get('file_language')).parents('.attachments').toggle();
-            jQuery('#fileselector_'+formdata.get('file_language')).parents('.attachments').find('span').toggle();
-            file.fadeIn(300);
-            statusbar.find('.progresstext').text(jQuery('#upload_received_data').text());
-            statusbar.delay(1000).fadeOut(300, function() {
-                jQuery('#upload_chooser').hide();
-                jQuery(this).remove();
-            });
-        })
-        .fail(function(jqxhr, status, errorThrown) {
-            var error = jqxhr.responseJSON.error;
-
-            statusbar
-                .find('.progress')
-                .addClass('progress-error')
-                .attr('title', error);
-            statusbar.find('.progresstext').html(error);
-            statusbar.on('click', function() {
-                jQuery(this).fadeOut(300, function() {
-                    jQuery(this).remove();
+                if (data.size > 1024 && data.size < 1024 * 1024) {
+                    file.find('.size').text(Math.floor(data.size / 1024) + 'KB');
+                }
+                if (data.size > 1024 * 1024 && data.size < 1024 * 1024 * 1024) {
+                    file.find('.size').text(Math.floor(data.size / 1024 / 1024) + 'MB');
+                }
+                if (data.size > 1024 * 1024 * 1024) {
+                    file.find('.size').text(Math.floor(data.size / 1024 / 1024 / 1024) + 'GB');
+                }
+                file.find('.icon').html(data.icon);
+                file.find('input[name=document_id]').attr('value', data.document_id);
+                if (update) {
+                    $(`#fileviewer_${language} .stgfiles`).empty().append(file);
+                    file.show();
+                } else {
+                    $(`#fileviewer_${language}`).find('.stgfiles').append(file);
+                    $(`#fileselector_${language}`)
+                        .toggle()
+                        .parents('.attachments').toggle()
+                        .find('span').toggle();
+                    file.fadeIn(300);
+                }
+                statusbar.find('.progresstext').text(jQuery('#upload_received_data').text());
+                statusbar.delay(1000).fadeOut(300, function() {
+                    $('#upload_chooser').hide();
+                    this.remove();
                 });
+
+                resolve();
+            }).fail(function(jqxhr, status, errorThrown) {
+                var error = jqxhr.responseJSON.error;
+
+                statusbar
+                    .find('.progress')
+                    .addClass('progress-error')
+                    .attr('title', error);
+                statusbar.find('.progresstext').html(error);
+                statusbar.on('click', function() {
+                    jQuery(this).fadeOut(300, function() {
+                        jQuery(this).remove();
+                    });
+                });
+
+                reject(new Error(error));
             });
         });
     }
diff --git a/resources/assets/javascripts/studip-ui.js b/resources/assets/javascripts/studip-ui.js
index f581295..f98ba94 100644
--- a/resources/assets/javascripts/studip-ui.js
+++ b/resources/assets/javascripts/studip-ui.js
@@ -1,5 +1,6 @@
 import { $gettext } from './lib/gettext';
 import eventBus from "./lib/event-bus.ts";
+import RestrictedDatesHelper from './lib/RestrictedDatesHelper';
 
 /**
  * This file contains extensions/adjustments for jQuery UI.
@@ -28,33 +29,11 @@ import eventBus from "./lib/event-bus.ts";
     }
 
     function disableHolidaysBeforeShow(date) {
-        const year = date.getFullYear();
-
-        if (STUDIP.UI.restrictedDates[year] === undefined) {
-            STUDIP.UI.restrictedDates[year] = {};
-
-            STUDIP.jsonapi.GET('holidays', {data: {
-                'filter[year]': year
-            }}).done(response => {
-                // Since PHP will return an empty object as an array,
-                // we need to check
-                if (Array.isArray(response)) {
-                    return;
-                }
-
-                for (const [date, data] of Object.entries(response)) {
-                    STUDIP.UI.addRestrictedDate(
-                        new Date(date),
-                        data.holiday,
-                        data.mandatory
-                    );
-                }
-
-                $(this).datepicker('refresh');
-            });
-        }
-
-        const {reason, lock} = STUDIP.UI.isDateRestricted(date, false);
+        RestrictedDatesHelper.loadRestrictedDatesByYear(date.getFullYear()).then(
+            () => $(this).datepicker('refresh'),
+            () => null
+        );
+        const {reason, lock} = RestrictedDatesHelper.isDateRestricted(date);
         return [!lock, lock ? 'ui-datepicker-is-locked' : null, reason];
     }
 
@@ -83,57 +62,8 @@ import eventBus from "./lib/event-bus.ts";
         return;
     }
 
+    STUDIP.UI = {};
     // Setup Stud.IP's own datepicker extensions
-    STUDIP.UI = Object.assign(STUDIP.UI || {}, {
-        restrictedDates: {},
-        addRestrictedDate(date, reason = '', lock = true) {
-            if (this.isDateRestricted(date)) {
-                return;
-            }
-
-            const [year, month, day] = this.convertDateForRestriction(date);
-            if (this.restrictedDates[year] === undefined) {
-                this.restrictedDates[year] = {};
-            }
-            if (this.restrictedDates[year][month] === undefined) {
-                this.restrictedDates[year][month] = {};
-            }
-
-            this.restrictedDates[year][month][day] = {reason, lock};
-        },
-        removeRestrictedDate(date) {
-            if (!this.isDateRestricted(date)) {
-                return false;
-            }
-            const [year, month, day] = this.convertDateForRestriction(date);
-
-            delete this.restrictedDates[year][month][day];
-
-            if (Object.keys(this.restrictedDates[year][month]).length === 0) {
-                delete this.restrictedDates[year][month];
-            }
-
-            return true;
-        },
-        isDateRestricted(date, return_bool = true) {
-            const [year, month, day] = this.convertDateForRestriction(date);
-            if (
-                this.restrictedDates[year] === undefined
-                || this.restrictedDates[year][month] === undefined
-                || this.restrictedDates[year][month][day] === undefined
-            ) {
-                return return_bool ? false : {
-                    reason: null,
-                    lock: false,
-                };
-            }
-
-            return return_bool ? true : this.restrictedDates[year][month][day];
-        },
-        convertDateForRestriction(date) {
-            return [date.getFullYear(), date.getMonth() + 1, date.getDate()];
-        }
-    });
     STUDIP.UI.Datepicker = {
         selector: '.has-date-picker,[data-date-picker]',
         // Initialize all datepickers that not yet been initialized (e.g. in dialogs)