From 323ab51762b16b3973cd49322cb5b6e8b062b511 Mon Sep 17 00:00:00 2001
From: Ece Eren <aybikeceren@gmail.com>
Date: Mon, 4 Nov 2024 08:30:11 +0100
Subject: [PATCH 01/11] Add hide icon to slide pages

---
 .../pdf-preview-thumbnail-grid.component.html |  1 +
 .../pdf-preview-thumbnail-grid.component.ts   | 21 ++++++++++++++++++-
 2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/src/main/webapp/app/lecture/pdf-preview/pdf-preview-thumbnail-grid/pdf-preview-thumbnail-grid.component.html b/src/main/webapp/app/lecture/pdf-preview/pdf-preview-thumbnail-grid/pdf-preview-thumbnail-grid.component.html
index 01ca1b9617a2..07d67be26971 100644
--- a/src/main/webapp/app/lecture/pdf-preview/pdf-preview-thumbnail-grid/pdf-preview-thumbnail-grid.component.html
+++ b/src/main/webapp/app/lecture/pdf-preview/pdf-preview-thumbnail-grid/pdf-preview-thumbnail-grid.component.html
@@ -1,3 +1,4 @@
+<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/6.0.0-beta3/css/all.min.css" />
 <div class="pdf-container" #pdfContainer>
     @if (isEnlargedView()) {
         <jhi-pdf-preview-enlarged-canvas-component
diff --git a/src/main/webapp/app/lecture/pdf-preview/pdf-preview-thumbnail-grid/pdf-preview-thumbnail-grid.component.ts b/src/main/webapp/app/lecture/pdf-preview/pdf-preview-thumbnail-grid/pdf-preview-thumbnail-grid.component.ts
index 84a220ad8cba..c4173bf84db1 100644
--- a/src/main/webapp/app/lecture/pdf-preview/pdf-preview-thumbnail-grid/pdf-preview-thumbnail-grid.component.ts
+++ b/src/main/webapp/app/lecture/pdf-preview/pdf-preview-thumbnail-grid/pdf-preview-thumbnail-grid.component.ts
@@ -135,15 +135,19 @@ export class PdfPreviewThumbnailGridComponent {
 
         const overlay = this.createOverlay(pageIndex);
         const checkbox = this.createCheckbox(pageIndex);
+        const hideShowIcon = this.createHideShowIcon(pageIndex);
         container.appendChild(canvas);
         container.appendChild(overlay);
         container.appendChild(checkbox);
+        container.appendChild(hideShowIcon);
 
         container.addEventListener('mouseenter', () => {
             overlay.style.opacity = '1';
+            hideShowIcon.style.opacity = '1';
         });
         container.addEventListener('mouseleave', () => {
             overlay.style.opacity = '0';
+            hideShowIcon.style.opacity = '0';
         });
         overlay.addEventListener('click', () => this.displayEnlargedCanvas(canvas));
 
@@ -165,6 +169,11 @@ export class PdfPreviewThumbnailGridComponent {
         return overlay;
     }
 
+    /**
+     * Generates a checkbox for each PDF page to allow for selection of pages.
+     * @param pageIndex The index of the page.
+     * @returns An input element styled as a checkbox.
+     */
     private createCheckbox(pageIndex: number): HTMLDivElement {
         const checkbox = document.createElement('input');
         checkbox.type = 'checkbox';
@@ -183,9 +192,19 @@ export class PdfPreviewThumbnailGridComponent {
         return checkbox;
     }
 
+    private createHideShowIcon(pageIndex: number): HTMLAnchorElement {
+        const icon = document.createElement('a');
+        icon.type = 'button';
+        icon.id = `hide-icon-${String(pageIndex)}`;
+        icon.className = 'btn btn-secondary';
+        icon.innerHTML = `<i class="fa fa-eye-slash" style="color: white"></i>`;
+        icon.style.cssText = `opacity: 0; position: absolute; bottom: -20px; left: 50%; transform: translateX(-50%); color: gray; cursor: pointer; z-index: 4;`;
+        return icon;
+    }
+
     /**
      * Displays the selected PDF page in an enlarged view for detailed examination.
-     * @param originalCanvas - The original canvas element of the PDF page to be enlarged.
+     * @param originalCanvas - The originala canvas element of the PDF page to be enlarged.
      * */
     displayEnlargedCanvas(originalCanvas: HTMLCanvasElement) {
         this.originalCanvas.set(originalCanvas);

From a14fe4fa4748032fff9e2fd911c969d52a274f3f Mon Sep 17 00:00:00 2001
From: Ece Eren <aybikeceren@gmail.com>
Date: Tue, 5 Nov 2024 00:46:47 +0100
Subject: [PATCH 02/11] Add functionality to hide-show buttons

---
 .../pdf-preview-thumbnail-grid.component.ts   | 51 ++++++++++++++-----
 1 file changed, 37 insertions(+), 14 deletions(-)

diff --git a/src/main/webapp/app/lecture/pdf-preview/pdf-preview-thumbnail-grid/pdf-preview-thumbnail-grid.component.ts b/src/main/webapp/app/lecture/pdf-preview/pdf-preview-thumbnail-grid/pdf-preview-thumbnail-grid.component.ts
index c4173bf84db1..4d4503aaf2bc 100644
--- a/src/main/webapp/app/lecture/pdf-preview/pdf-preview-thumbnail-grid/pdf-preview-thumbnail-grid.component.ts
+++ b/src/main/webapp/app/lecture/pdf-preview/pdf-preview-thumbnail-grid/pdf-preview-thumbnail-grid.component.ts
@@ -135,20 +135,22 @@ export class PdfPreviewThumbnailGridComponent {
 
         const overlay = this.createOverlay(pageIndex);
         const checkbox = this.createCheckbox(pageIndex);
-        const hideShowIcon = this.createHideShowIcon(pageIndex);
+        const hideButton = this.createHideButton(pageIndex);
         container.appendChild(canvas);
         container.appendChild(overlay);
         container.appendChild(checkbox);
-        container.appendChild(hideShowIcon);
+        container.appendChild(hideButton);
 
         container.addEventListener('mouseenter', () => {
             overlay.style.opacity = '1';
-            hideShowIcon.style.opacity = '1';
+            hideButton.style.opacity = '1';
         });
         container.addEventListener('mouseleave', () => {
             overlay.style.opacity = '0';
-            hideShowIcon.style.opacity = '0';
+            hideButton.style.opacity = '0';
         });
+
+        hideButton.addEventListener('click', () => this.toggleVisibility(container, hideButton));
         overlay.addEventListener('click', () => this.displayEnlargedCanvas(canvas));
 
         return container;
@@ -165,7 +167,7 @@ export class PdfPreviewThumbnailGridComponent {
         /* Dynamically created elements are not detected by DOM, that is why we need to set the styles manually.
          * See: https://stackoverflow.com/a/70911189
          */
-        overlay.style.cssText = `position: absolute; top: 0; left: 0; width: 100%; height: 100%; display: flex; justify-content: center; align-items: center; font-size: 24px; color: white; z-index: 1; transition: opacity 0.3s ease; opacity: 0; cursor: pointer; background-color: var(--pdf-preview-container-overlay)`;
+        overlay.style.cssText = `position: absolute; top: 0; left: 0; width: 100%; height: 100%; display: flex; justify-content: center; align-items: center; font-size: 24px; color: white; z-index: 2; transition: opacity 0.3s ease; opacity: 0; cursor: pointer; background-color: var(--pdf-preview-container-overlay)`;
         return overlay;
     }
 
@@ -192,19 +194,40 @@ export class PdfPreviewThumbnailGridComponent {
         return checkbox;
     }
 
-    private createHideShowIcon(pageIndex: number): HTMLAnchorElement {
-        const icon = document.createElement('a');
-        icon.type = 'button';
-        icon.id = `hide-icon-${String(pageIndex)}`;
-        icon.className = 'btn btn-secondary';
-        icon.innerHTML = `<i class="fa fa-eye-slash" style="color: white"></i>`;
-        icon.style.cssText = `opacity: 0; position: absolute; bottom: -20px; left: 50%; transform: translateX(-50%); color: gray; cursor: pointer; z-index: 4;`;
-        return icon;
+    private createHideButton(pageIndex: number): HTMLAnchorElement {
+        const hideButton = document.createElement('a');
+        hideButton.type = 'button';
+        hideButton.id = `hide-icon-${pageIndex}`;
+        hideButton.className = 'btn btn-secondary';
+        hideButton.style.cssText = `opacity: 0; position: absolute; bottom: -20px; left: 50%; transform: translateX(-50%); cursor: pointer; z-index: 4;`;
+        hideButton.innerHTML = `<i class="fa fa-eye-slash"></i>`;
+
+        return hideButton;
+    }
+
+    private toggleVisibility(container: HTMLDivElement, hideButton: HTMLAnchorElement): void {
+        const overlay = document.createElement('div');
+        overlay.id = 'pdf-page-overlay';
+        overlay.style.cssText = `position: absolute; top: 0; width: 100%; height: 100%; z-index: 1; transition: opacity 0.3s ease; background-color: var(--pdf-preview-container-overlay)`;
+
+        const diagonalLine = document.createElement('div');
+        diagonalLine.style.cssText = `position: absolute; top: 0; left: 0; width: 115%; height: 2px; background-color: white; transform: rotate(29deg); transform-origin: top left;`;
+        overlay.appendChild(diagonalLine);
+
+        if (hideButton.className === 'btn btn-secondary') {
+            container.appendChild(overlay);
+            hideButton.className = 'btn btn-success';
+            hideButton.children[0].className = 'fa fa-eye';
+        } else {
+            container.removeChild(container.querySelector(`#pdf-page-overlay`)!);
+            hideButton.className = 'btn btn-secondary';
+            hideButton.children[0].className = 'fa fa-eye-slash';
+        }
     }
 
     /**
      * Displays the selected PDF page in an enlarged view for detailed examination.
-     * @param originalCanvas - The originala canvas element of the PDF page to be enlarged.
+     * @param originalCanvas - The original canvas element of the PDF page to be enlarged.
      * */
     displayEnlargedCanvas(originalCanvas: HTMLCanvasElement) {
         this.originalCanvas.set(originalCanvas);

From e9a4ace13c895db6c1a77334e2733cfbbe3c3537 Mon Sep 17 00:00:00 2001
From: Ece Eren <aybikeceren@gmail.com>
Date: Sun, 10 Nov 2024 18:12:27 +0100
Subject: [PATCH 03/11] Add slide hiding capability & creating a hidden version
 of the file

---
 .../artemis/lecture/domain/Attachment.java    |  26 +++-
 .../repository/AttachmentRepository.java      |   7 +
 .../lecture/web/AttachmentResource.java       |  13 ++
 .../changelog/20241110173144_changelog.xml    |  22 +++
 .../resources/config/liquibase/master.xml     |   1 +
 .../webapp/app/entities/attachment.model.ts   |   2 +
 .../webapp/app/lecture/attachment.service.ts  |  12 ++
 .../pdf-preview-thumbnail-grid.component.ts   |  56 +++++---
 .../pdf-preview/pdf-preview.component.html    |   9 +-
 .../pdf-preview/pdf-preview.component.ts      | 126 +++++++++++++++++-
 10 files changed, 250 insertions(+), 24 deletions(-)
 create mode 100644 src/main/resources/config/liquibase/changelog/20241110173144_changelog.xml

diff --git a/src/main/java/de/tum/cit/aet/artemis/lecture/domain/Attachment.java b/src/main/java/de/tum/cit/aet/artemis/lecture/domain/Attachment.java
index 6806850fd86b..ca2bb2104d85 100644
--- a/src/main/java/de/tum/cit/aet/artemis/lecture/domain/Attachment.java
+++ b/src/main/java/de/tum/cit/aet/artemis/lecture/domain/Attachment.java
@@ -61,6 +61,13 @@ public class Attachment extends DomainObject implements Serializable {
     @JoinColumn(name = "attachment_unit_id")
     private AttachmentUnit attachmentUnit;
 
+    @Column(name = "hidden_pages")
+    private String hiddenPages;
+
+    @OneToOne
+    @JoinColumn(name = "parent_attachment_id")
+    private Attachment parentAttachment;
+
     // jhipster-needle-entity-add-field - JHipster will add fields here, do not remove
 
     public String getName() {
@@ -135,6 +142,22 @@ public void setAttachmentUnit(AttachmentUnit attachmentUnit) {
         this.attachmentUnit = attachmentUnit;
     }
 
+    public String getHiddenPages() {
+        return hiddenPages;
+    }
+
+    public void setHiddenPages(String hiddenPages) {
+        this.hiddenPages = hiddenPages;
+    }
+
+    public Attachment getParentAttachment() {
+        return parentAttachment;
+    }
+
+    public void setParentAttachment(Attachment parentAttachment) {
+        this.parentAttachment = parentAttachment;
+    }
+
     public Boolean isVisibleToStudents() {
         if (releaseDate == null) {  // no release date means the attachment is visible to students
             return Boolean.TRUE;
@@ -145,6 +168,7 @@ public Boolean isVisibleToStudents() {
     @Override
     public String toString() {
         return "Attachment{" + "id=" + getId() + ", name='" + getName() + "'" + ", link='" + getLink() + "'" + ", version='" + getVersion() + "'" + ", uploadDate='"
-                + getUploadDate() + "'" + ", releaseDate='" + getReleaseDate() + "'" + ", attachmentType='" + getAttachmentType() + "'" + "}";
+                + getUploadDate() + "'" + ", releaseDate='" + getReleaseDate() + "'" + ", attachmentType='" + getAttachmentType() + "'" + ", hiddenPages='" + getHiddenPages() + "'"
+                + ", parentAttachment='" + getParentAttachment() + "'" + "}";
     }
 }
diff --git a/src/main/java/de/tum/cit/aet/artemis/lecture/repository/AttachmentRepository.java b/src/main/java/de/tum/cit/aet/artemis/lecture/repository/AttachmentRepository.java
index 30b1068ed687..fc7a355223bc 100644
--- a/src/main/java/de/tum/cit/aet/artemis/lecture/repository/AttachmentRepository.java
+++ b/src/main/java/de/tum/cit/aet/artemis/lecture/repository/AttachmentRepository.java
@@ -29,4 +29,11 @@ public interface AttachmentRepository extends ArtemisJpaRepository<Attachment, L
     default Attachment findByIdOrElseThrow(Long attachmentId) {
         return getValueElseThrow(findById(attachmentId), attachmentId);
     }
+
+    @Query("""
+            SELECT a
+            FROM Attachment a
+            WHERE a.parentAttachment.id = :parentAttachmentId
+            """)
+    Attachment findAttachmentByParentAttachmentId(@Param("parentAttachmentId") Long parentAttachmentId);
 }
diff --git a/src/main/java/de/tum/cit/aet/artemis/lecture/web/AttachmentResource.java b/src/main/java/de/tum/cit/aet/artemis/lecture/web/AttachmentResource.java
index 3b5e44b6ac2f..aeb10b752e16 100644
--- a/src/main/java/de/tum/cit/aet/artemis/lecture/web/AttachmentResource.java
+++ b/src/main/java/de/tum/cit/aet/artemis/lecture/web/AttachmentResource.java
@@ -210,4 +210,17 @@ else if (attachment.getExercise() != null) {
         }
         return ResponseEntity.ok().headers(HeaderUtil.createEntityDeletionAlert(applicationName, true, ENTITY_NAME, attachmentId.toString())).build();
     }
+
+    /**
+     * GET /attachments/:parentAttachmentId/hiddenAttachment : retrieve the hidden attachment associated with the given parent attachment ID.
+     *
+     * @param parentAttachmentId the ID of the parent attachment for which to retrieve the hidden attachment
+     * @return the ResponseEntity with status 200 (OK) and the Attachment in the body, or a 404 (Not Found) if no matching attachment exists
+     */
+    @GetMapping("attachments/{parentAttachmentId}/hiddenAttachment")
+    @EnforceAtLeastTutor
+    public ResponseEntity<Attachment> getAttachmentByParentAttachmentId(@PathVariable Long parentAttachmentId) {
+        log.debug("REST request to get attachment by the parent attachment Id : {}", parentAttachmentId);
+        return ResponseEntity.ok(attachmentRepository.findAttachmentByParentAttachmentId(parentAttachmentId));
+    }
 }
diff --git a/src/main/resources/config/liquibase/changelog/20241110173144_changelog.xml b/src/main/resources/config/liquibase/changelog/20241110173144_changelog.xml
new file mode 100644
index 000000000000..c36a705137ba
--- /dev/null
+++ b/src/main/resources/config/liquibase/changelog/20241110173144_changelog.xml
@@ -0,0 +1,22 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<databaseChangeLog xmlns="http://www.liquibase.org/xml/ns/dbchangelog"
+                   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+                   xsi:schemaLocation="http://www.liquibase.org/xml/ns/dbchangelog https://www.liquibase.org/xml/ns/dbchangelog/dbchangelog-latest.xsd">
+    <changeSet id="20241110173144" author="ece.eren">
+        <addColumn tableName="attachment">
+            <column name="hidden_pages" type="VARCHAR(255)"/>
+        </addColumn>
+
+        <addColumn tableName="attachment">
+            <column name="parent_attachment_id" type="BIGINT"/>
+        </addColumn>
+
+        <addForeignKeyConstraint
+                baseTableName="attachment"
+                baseColumnNames="parent_attachment_id"
+                referencedTableName="attachment"
+                referencedColumnNames="id"
+                constraintName="fk_attachment_parent_attachment_id"
+                onDelete="CASCADE"/>
+    </changeSet>
+</databaseChangeLog>
diff --git a/src/main/resources/config/liquibase/master.xml b/src/main/resources/config/liquibase/master.xml
index 5ae5903ea896..d3cecd760366 100644
--- a/src/main/resources/config/liquibase/master.xml
+++ b/src/main/resources/config/liquibase/master.xml
@@ -32,6 +32,7 @@
     <include file="classpath:config/liquibase/changelog/20241010101010_changelog.xml" relativeToChangelogFile="false"/>
     <include file="classpath:config/liquibase/changelog/20241018053210_changelog.xml" relativeToChangelogFile="false"/>
     <include file="classpath:config/liquibase/changelog/20241023456789_changelog.xml" relativeToChangelogFile="false"/>
+    <include file="classpath:config/liquibase/changelog/20241110173144_changelog.xml" relativeToChangelogFile="false"/>
 
     <!-- NOTE: please use the format "YYYYMMDDhhmmss_changelog.xml", i.e. year month day hour minutes seconds and not something else! -->
     <!-- we should also stay in a chronological order! -->
diff --git a/src/main/webapp/app/entities/attachment.model.ts b/src/main/webapp/app/entities/attachment.model.ts
index c070019513ee..a169618ca2ca 100644
--- a/src/main/webapp/app/entities/attachment.model.ts
+++ b/src/main/webapp/app/entities/attachment.model.ts
@@ -20,6 +20,8 @@ export class Attachment implements BaseEntity {
     lecture?: Lecture;
     exercise?: Exercise;
     attachmentUnit?: AttachmentUnit;
+    hiddenPages?: string;
+    parentAttachment?: Attachment;
 
     constructor() {}
 }
diff --git a/src/main/webapp/app/lecture/attachment.service.ts b/src/main/webapp/app/lecture/attachment.service.ts
index 446d26960f8b..ae576a073e86 100644
--- a/src/main/webapp/app/lecture/attachment.service.ts
+++ b/src/main/webapp/app/lecture/attachment.service.ts
@@ -147,4 +147,16 @@ export class AttachmentService {
     getAttachmentFile(courseId: number, attachmentId: number): Observable<Blob> {
         return this.http.get(`api/files/courses/${courseId}/attachments/${attachmentId}`, { responseType: 'blob' });
     }
+
+    /**
+     * Retrieve the hidden attachment associated with a given parent attachment ID
+     *
+     * @param parentAttachmentId The ID of the parent attachment whose hidden attachment is to be retrieved
+     * @returns An Observable that emits an EntityResponseType containing the Attachment object when the HTTP request completes successfully
+     */
+    getAttachmentByParentAttachmentId(parentAttachmentId: number): Observable<EntityResponseType> {
+        return this.http
+            .get<Attachment>(`${this.resourceUrl}/${parentAttachmentId}/hiddenAttachment`, { observe: 'response' })
+            .pipe(map((res: EntityResponseType) => this.convertAttachmentResponseDatesFromServer(res)));
+    }
 }
diff --git a/src/main/webapp/app/lecture/pdf-preview/pdf-preview-thumbnail-grid/pdf-preview-thumbnail-grid.component.ts b/src/main/webapp/app/lecture/pdf-preview/pdf-preview-thumbnail-grid/pdf-preview-thumbnail-grid.component.ts
index 4d4503aaf2bc..e74093fd8400 100644
--- a/src/main/webapp/app/lecture/pdf-preview/pdf-preview-thumbnail-grid/pdf-preview-thumbnail-grid.component.ts
+++ b/src/main/webapp/app/lecture/pdf-preview/pdf-preview-thumbnail-grid/pdf-preview-thumbnail-grid.component.ts
@@ -5,6 +5,7 @@ import { ArtemisSharedModule } from 'app/shared/shared.module';
 import { onError } from 'app/shared/util/global.utils';
 import { AlertService } from 'app/core/util/alert.service';
 import { PdfPreviewEnlargedCanvasComponent } from 'app/lecture/pdf-preview/pdf-preview-enlarged-canvas/pdf-preview-enlarged-canvas.component';
+import { clone } from 'lodash-es';
 
 @Component({
     selector: 'jhi-pdf-preview-thumbnail-grid-component',
@@ -21,17 +22,21 @@ export class PdfPreviewThumbnailGridComponent {
     // Inputs
     currentPdfUrl = input<string>();
     appendFile = input<boolean>();
+    hiddenPages = input<Set<number>>();
 
     // Signals
     isEnlargedView = signal<boolean>(false);
     totalPages = signal<number>(0);
     selectedPages = signal<Set<number>>(new Set());
     originalCanvas = signal<HTMLCanvasElement | undefined>(undefined);
+    newHiddenPages = signal(new Set<number>(this.hiddenPages()!));
 
     // Outputs
     isPdfLoading = output<boolean>();
     totalPagesOutput = output<number>();
     selectedPagesOutput = output<Set<number>>();
+    newHiddenPagesOutput = output<Set<number>>();
+    hiddenPagesChangedOutput = output<boolean>();
 
     // Injected services
     private readonly alertService = inject(AlertService);
@@ -39,6 +44,7 @@ export class PdfPreviewThumbnailGridComponent {
     constructor() {
         effect(
             () => {
+                this.newHiddenPages.set(clone(this.hiddenPages()!));
                 this.loadOrAppendPdf(this.currentPdfUrl()!, this.appendFile());
             },
             { allowSignalWrites: true },
@@ -135,22 +141,22 @@ export class PdfPreviewThumbnailGridComponent {
 
         const overlay = this.createOverlay(pageIndex);
         const checkbox = this.createCheckbox(pageIndex);
-        const hideButton = this.createHideButton(pageIndex);
+        const hideShowButton = this.createHideShowButton(pageIndex, container);
         container.appendChild(canvas);
         container.appendChild(overlay);
         container.appendChild(checkbox);
-        container.appendChild(hideButton);
+        container.appendChild(hideShowButton);
 
         container.addEventListener('mouseenter', () => {
             overlay.style.opacity = '1';
-            hideButton.style.opacity = '1';
+            hideShowButton.style.opacity = '1';
         });
         container.addEventListener('mouseleave', () => {
             overlay.style.opacity = '0';
-            hideButton.style.opacity = '0';
+            hideShowButton.style.opacity = '0';
         });
 
-        hideButton.addEventListener('click', () => this.toggleVisibility(container, hideButton));
+        hideShowButton.addEventListener('click', () => this.toggleVisibility(container, hideShowButton));
         overlay.addEventListener('click', () => this.displayEnlargedCanvas(canvas));
 
         return container;
@@ -194,18 +200,35 @@ export class PdfPreviewThumbnailGridComponent {
         return checkbox;
     }
 
-    private createHideButton(pageIndex: number): HTMLAnchorElement {
+    private createHideShowButton(pageIndex: number, container: HTMLDivElement): HTMLAnchorElement {
         const hideButton = document.createElement('a');
         hideButton.type = 'button';
-        hideButton.id = `hide-icon-${pageIndex}`;
-        hideButton.className = 'btn btn-secondary';
         hideButton.style.cssText = `opacity: 0; position: absolute; bottom: -20px; left: 50%; transform: translateX(-50%); cursor: pointer; z-index: 4;`;
-        hideButton.innerHTML = `<i class="fa fa-eye-slash"></i>`;
+
+        if (this.hiddenPages()!.has(pageIndex)) {
+            hideButton.className = 'btn btn-success';
+            hideButton.id = `show-button-${pageIndex}`;
+            hideButton.innerHTML = `<i class="fa fa-eye"></i>`;
+
+            const overlay = document.createElement('div');
+            overlay.id = 'pdf-page-overlay';
+            overlay.style.cssText = `position: absolute; top: 0; width: 100%; height: 100%; z-index: 1; transition: opacity 0.3s ease; background-color: var(--pdf-preview-container-overlay)`;
+
+            const diagonalLine = document.createElement('div');
+            diagonalLine.style.cssText = `position: absolute; top: 0; left: 0; width: 115%; height: 2px; background-color: white; transform: rotate(29deg); transform-origin: top left;`;
+            overlay.appendChild(diagonalLine);
+
+            container.appendChild(overlay);
+        } else {
+            hideButton.className = 'btn btn-secondary';
+            hideButton.id = `hide-button-${pageIndex}`;
+            hideButton.innerHTML = `<i class="fa fa-eye-slash"></i>`;
+        }
 
         return hideButton;
     }
 
-    private toggleVisibility(container: HTMLDivElement, hideButton: HTMLAnchorElement): void {
+    private toggleVisibility(container: HTMLDivElement, hideShowButton: HTMLAnchorElement): void {
         const overlay = document.createElement('div');
         overlay.id = 'pdf-page-overlay';
         overlay.style.cssText = `position: absolute; top: 0; width: 100%; height: 100%; z-index: 1; transition: opacity 0.3s ease; background-color: var(--pdf-preview-container-overlay)`;
@@ -214,15 +237,18 @@ export class PdfPreviewThumbnailGridComponent {
         diagonalLine.style.cssText = `position: absolute; top: 0; left: 0; width: 115%; height: 2px; background-color: white; transform: rotate(29deg); transform-origin: top left;`;
         overlay.appendChild(diagonalLine);
 
-        if (hideButton.className === 'btn btn-secondary') {
+        if (hideShowButton.className === 'btn btn-secondary') {
             container.appendChild(overlay);
-            hideButton.className = 'btn btn-success';
-            hideButton.children[0].className = 'fa fa-eye';
+            hideShowButton.className = 'btn btn-success';
+            hideShowButton.children[0].className = 'fa fa-eye';
+            this.newHiddenPages().add(Number(hideShowButton.id.split('-')[2]));
         } else {
             container.removeChild(container.querySelector(`#pdf-page-overlay`)!);
-            hideButton.className = 'btn btn-secondary';
-            hideButton.children[0].className = 'fa fa-eye-slash';
+            hideShowButton.className = 'btn btn-secondary';
+            hideShowButton.children[0].className = 'fa fa-eye-slash';
+            this.newHiddenPages().delete(Number(hideShowButton.id.split('-')[2]));
         }
+        this.newHiddenPagesOutput.emit(this.newHiddenPages());
     }
 
     /**
diff --git a/src/main/webapp/app/lecture/pdf-preview/pdf-preview.component.html b/src/main/webapp/app/lecture/pdf-preview/pdf-preview.component.html
index 16fc58678b07..dd0276af421f 100644
--- a/src/main/webapp/app/lecture/pdf-preview/pdf-preview.component.html
+++ b/src/main/webapp/app/lecture/pdf-preview/pdf-preview.component.html
@@ -43,9 +43,11 @@ <h4>
             <jhi-pdf-preview-thumbnail-grid-component
                 [currentPdfUrl]="currentPdfUrl()"
                 [appendFile]="appendFile()"
+                [hiddenPages]="hiddenPages()"
                 (isPdfLoading)="isPdfLoading.set($event)"
                 (selectedPagesOutput)="selectedPages.set($event)"
                 (totalPagesOutput)="totalPages.set($event)"
+                (newHiddenPagesOutput)="newHiddenPages.set($event)"
             />
         }
         <div class="d-flex justify-content-between">
@@ -65,7 +67,12 @@ <h4>
                 </a>
             </div>
             <div>
-                <button type="submit" (click)="updateAttachmentWithFile()" class="btn btn-primary" [disabled]="isPdfLoading() || totalPages() === 0 || !isFileChanged()">
+                <button
+                    type="submit"
+                    (click)="updateAttachmentWithFile()"
+                    class="btn btn-primary"
+                    [disabled]="(isPdfLoading() || totalPages() === 0 || !isFileChanged()) && !hiddenPagesChanged()"
+                >
                     <fa-icon [icon]="faSave" [ngbTooltip]="'entity.action.save' | artemisTranslate"></fa-icon>
                     <span jhiTranslate="entity.action.save"></span>
                 </button>
diff --git a/src/main/webapp/app/lecture/pdf-preview/pdf-preview.component.ts b/src/main/webapp/app/lecture/pdf-preview/pdf-preview.component.ts
index c912c211d3c7..0f0c8feded99 100644
--- a/src/main/webapp/app/lecture/pdf-preview/pdf-preview.component.ts
+++ b/src/main/webapp/app/lecture/pdf-preview/pdf-preview.component.ts
@@ -1,4 +1,4 @@
-import { Component, ElementRef, OnDestroy, OnInit, inject, signal, viewChild } from '@angular/core';
+import { Component, ElementRef, OnDestroy, OnInit, effect, inject, signal, viewChild } from '@angular/core';
 import { ActivatedRoute, Router } from '@angular/router';
 import { AttachmentService } from 'app/lecture/attachment.service';
 import { Attachment } from 'app/entities/attachment.model';
@@ -17,6 +17,7 @@ import { MAX_FILE_SIZE } from 'app/shared/constants/input.constants';
 import { PdfPreviewThumbnailGridComponent } from 'app/lecture/pdf-preview/pdf-preview-thumbnail-grid/pdf-preview-thumbnail-grid.component';
 import { LectureUnitService } from 'app/lecture/lecture-unit/lecture-unit-management/lectureUnit.service';
 import { PDFDocument } from 'pdf-lib';
+import { cloneDeep } from 'lodash-es';
 
 @Component({
     selector: 'jhi-pdf-preview-component',
@@ -42,6 +43,8 @@ export class PdfPreviewComponent implements OnInit, OnDestroy {
     appendFile = signal<boolean>(false);
     isFileChanged = signal<boolean>(false);
     selectedPages = signal<Set<number>>(new Set());
+    hiddenPages = signal<Set<number>>(new Set());
+    newHiddenPages = signal<Set<number>>(new Set());
 
     // Injected services
     private readonly route = inject(ActivatedRoute);
@@ -66,6 +69,7 @@ export class PdfPreviewComponent implements OnInit, OnDestroy {
 
             if ('attachment' in data) {
                 this.attachment.set(data.attachment);
+                this.hiddenPages.set(new Set(data.attachment.hiddenPages?.split(',').map(Number) || []));
                 this.attachmentSub = this.attachmentService.getAttachmentFile(this.course()!.id!, this.attachment()!.id!).subscribe({
                     next: (blob: Blob) => {
                         this.currentPdfBlob.set(blob);
@@ -75,6 +79,7 @@ export class PdfPreviewComponent implements OnInit, OnDestroy {
                 });
             } else if ('attachmentUnit' in data) {
                 this.attachmentUnit.set(data.attachmentUnit);
+                this.hiddenPages.set(new Set(data.attachmentUnit.attachment.hiddenPages?.split(',').map(Number) || []));
                 this.attachmentUnitSub = this.attachmentUnitService.getAttachmentFile(this.course()!.id!, this.attachmentUnit()!.id!).subscribe({
                     next: (blob: Blob) => {
                         this.currentPdfBlob.set(blob);
@@ -91,6 +96,15 @@ export class PdfPreviewComponent implements OnInit, OnDestroy {
         this.attachmentUnitSub?.unsubscribe();
     }
 
+    constructor() {
+        effect(
+            () => {
+                this.hiddenPagesChanged();
+            },
+            { allowSignalWrites: true },
+        );
+    }
+
     /**
      * Checks if all pages are selected.
      * @returns True if the number of selected pages equals the total number of pages, otherwise false.
@@ -106,6 +120,23 @@ export class PdfPreviewComponent implements OnInit, OnDestroy {
         this.fileInput().nativeElement.click();
     }
 
+    /**
+     * Checks if there has been any change between the current set of hidden pages and the new set of hidden pages.
+     *
+     * @returns Returns true if the sets differ in size or if any element in `newHiddenPages` is not found in `hiddenPages`, otherwise false.
+     */
+    hiddenPagesChanged() {
+        if (this.hiddenPages()!.size !== this.newHiddenPages()!.size) return true;
+
+        for (const elem of this.newHiddenPages()!) {
+            if (!this.hiddenPages()!.has(elem)) return true;
+        }
+        return false;
+    }
+
+    /**
+     * Updates the existing attachment file or creates a new hidden version of the attachment.
+     */
     updateAttachmentWithFile(): void {
         const pdfFile = new File([this.currentPdfBlob()!], 'updatedAttachment.pdf', { type: 'application/pdf' });
 
@@ -118,11 +149,48 @@ export class PdfPreviewComponent implements OnInit, OnDestroy {
             this.attachmentToBeEdited.set(this.attachment());
             this.attachmentToBeEdited()!.version!++;
             this.attachmentToBeEdited()!.uploadDate = dayjs();
+            this.attachmentToBeEdited()!.hiddenPages = Array.from(this.newHiddenPages()).join(',');
 
             this.attachmentService.update(this.attachmentToBeEdited()!.id!, this.attachmentToBeEdited()!, pdfFile).subscribe({
-                next: () => {
-                    this.alertService.success('artemisApp.attachment.pdfPreview.attachmentUpdateSuccess');
-                    this.router.navigate(['course-management', this.course()?.id, 'lectures', this.attachment()!.lecture!.id, 'attachments']);
+                next: async () => {
+                    if (this.newHiddenPages().size > 0) {
+                        const pdfFileWithHiddenPages = await this.createHiddenVersionOfAttachment(Array.from(this.newHiddenPages()));
+                        this.attachmentService.getAttachmentByParentAttachmentId(this.attachment()!.id!).subscribe({
+                            next: async (attachmentRes) => {
+                                if (attachmentRes.body && attachmentRes.body.id) {
+                                    attachmentRes.body.version!++;
+                                    this.attachmentService.update(attachmentRes.body.id, attachmentRes.body, pdfFileWithHiddenPages!).subscribe({
+                                        next: () => {
+                                            this.router.navigate(['course-management', this.course()?.id, 'lectures', this.attachment()!.lecture!.id, 'attachments']);
+                                        },
+                                        error: (error) => {
+                                            this.alertService.error('artemisApp.attachment.pdfPreview.hiddenAttachmentUpdateError', { error: error.message });
+                                        },
+                                    });
+                                } else {
+                                    const attachmentWithHiddenPages = cloneDeep(this.attachment()!);
+                                    attachmentWithHiddenPages.parentAttachment = this.attachment()!;
+                                    attachmentWithHiddenPages.name = `${attachmentWithHiddenPages.name}_hidden`;
+                                    attachmentWithHiddenPages.hiddenPages = undefined;
+                                    this.attachmentService.create(attachmentWithHiddenPages, pdfFileWithHiddenPages!).subscribe({
+                                        next: () => {
+                                            this.alertService.success('artemisApp.attachment.pdfPreview.hiddenAttachmentCreateSuccess');
+                                            this.router.navigate(['course-management', this.course()?.id, 'lectures', this.attachment()!.lecture!.id, 'attachments']);
+                                        },
+                                        error: (error) => {
+                                            this.alertService.error('artemisApp.attachment.pdfPreview.hiddenAttachmentCreateError', { error: error.message });
+                                        },
+                                    });
+                                }
+                            },
+                            error: (error) => {
+                                this.alertService.error('artemisApp.attachment.pdfPreview.attachmentUpdateError', { error: error.message });
+                            },
+                        });
+                    } else {
+                        this.alertService.success('artemisApp.attachment.pdfPreview.attachmentUpdateSuccess');
+                        this.router.navigate(['course-management', this.course()?.id, 'lectures', this.attachment()!.lecture!.id, 'attachments']);
+                    }
                 },
                 error: (error) => {
                     this.alertService.error('artemisApp.attachment.pdfPreview.attachmentUpdateError', { error: error.message });
@@ -132,6 +200,7 @@ export class PdfPreviewComponent implements OnInit, OnDestroy {
             this.attachmentToBeEdited.set(this.attachmentUnit()!.attachment!);
             this.attachmentToBeEdited()!.version!++;
             this.attachmentToBeEdited()!.uploadDate = dayjs();
+            this.attachmentToBeEdited()!.hiddenPages = Array.from(this.hiddenPages()).join(',');
 
             const formData = new FormData();
             formData.append('file', pdfFile);
@@ -139,9 +208,28 @@ export class PdfPreviewComponent implements OnInit, OnDestroy {
             formData.append('attachmentUnit', objectToJsonBlob(this.attachmentUnit()!));
 
             this.attachmentUnitService.update(this.attachmentUnit()!.lecture!.id!, this.attachmentUnit()!.id!, formData).subscribe({
-                next: () => {
-                    this.alertService.success('artemisApp.attachment.pdfPreview.attachmentUpdateSuccess');
-                    this.router.navigate(['course-management', this.course()?.id, 'lectures', this.attachmentUnit()!.lecture!.id, 'unit-management']);
+                next: async () => {
+                    if (this.hiddenPages().size > 0) {
+                        const attachmentWithHiddenPages = cloneDeep(this.attachmentUnit()?.attachment!);
+                        attachmentWithHiddenPages.parentAttachment = this.attachmentUnit()?.attachment!;
+                        const pdfFileWithHiddenPages = await this.createHiddenVersionOfAttachment(Array.from(this.hiddenPages()));
+
+                        formData.append('file', pdfFileWithHiddenPages!);
+                        formData.append('attachment', objectToJsonBlob(attachmentWithHiddenPages));
+
+                        this.attachmentUnitService.create(formData, this.attachmentUnit()?.lecture!.id!).subscribe({
+                            next: () => {
+                                this.alertService.success('artemisApp.attachment.pdfPreview.attachmentUpdateSuccess');
+                                this.router.navigate(['course-management', this.course()?.id, 'lectures', this.attachmentUnit()!.lecture!.id, 'unit-management']);
+                            },
+                            error: (error) => {
+                                this.alertService.error('artemisApp.attachment.pdfPreview.attachmentUpdateError', { error: error.message });
+                            },
+                        });
+                    } else {
+                        this.alertService.success('artemisApp.attachment.pdfPreview.attachmentUpdateSuccess');
+                        this.router.navigate(['course-management', this.course()?.id, 'lectures', this.attachment()!.lecture!.id, 'attachments']);
+                    }
                 },
                 error: (error) => {
                     this.alertService.error('artemisApp.attachment.pdfPreview.attachmentUpdateError', { error: error.message });
@@ -210,6 +298,30 @@ export class PdfPreviewComponent implements OnInit, OnDestroy {
         }
     }
 
+    /**
+     * Creates a hidden version of the current PDF attachment by removing specified pages.
+     *
+     * @param hiddenPages - An array of page numbers to be removed from the original PDF.
+     * @returns A promise that resolves to a new `File` object representing the modified PDF, or undefined if an error occurs.
+     */
+    async createHiddenVersionOfAttachment(hiddenPages: number[]) {
+        try {
+            const fileName = this.attachment()!.name;
+            const existingPdfBytes = await this.currentPdfBlob()!.arrayBuffer();
+            const hiddenPdfDoc = await PDFDocument.load(existingPdfBytes);
+
+            const pagesToDelete = hiddenPages.map((page) => page - 1).sort((a, b) => b - a);
+            pagesToDelete.forEach((pageIndex) => {
+                hiddenPdfDoc.removePage(pageIndex);
+            });
+
+            const pdfBytes = await hiddenPdfDoc.save();
+            return new File([pdfBytes], `${fileName}_hidden.pdf`, { type: 'application/pdf' });
+        } catch (error) {
+            this.alertService.error('artemisApp.attachment.pdfPreview.pageDeleteError', { error: error.message });
+        }
+    }
+
     /**
      * Adds a selected PDF file at the end of the current PDF document.
      * @param event - The event containing the file input.

From 1c53219172204064390f63eb28ebe2bcf619c61f Mon Sep 17 00:00:00 2001
From: Ece Eren <aybikeceren@gmail.com>
Date: Tue, 12 Nov 2024 02:44:20 +0100
Subject: [PATCH 04/11] Adapt hidden pages to attachment units & remove from
 attachments

---
 .../artemis/lecture/domain/Attachment.java    |  26 +----
 .../lecture/domain/AttachmentUnit.java        |  26 +++++
 .../repository/AttachmentRepository.java      |   7 --
 .../repository/AttachmentUnitRepository.java  |   8 ++
 .../service/AttachmentUnitService.java        |   1 +
 .../lecture/web/AttachmentResource.java       |  13 ---
 .../lecture/web/AttachmentUnitResource.java   |  15 +++
 ...gelog.xml => 20241112002519_changelog.xml} |  16 +--
 .../resources/config/liquibase/master.xml     |   2 +-
 .../webapp/app/entities/attachment.model.ts   |   2 -
 .../lecture-unit/attachmentUnit.model.ts      |   2 +
 .../webapp/app/lecture/attachment.service.ts  |  12 --
 .../attachment-unit-form.component.ts         |   3 +
 .../attachmentUnit.service.ts                 |  13 +++
 .../create-attachment-unit.component.ts       |   4 +-
 .../pdf-preview-thumbnail-grid.component.ts   |  47 ++++----
 .../pdf-preview/pdf-preview.component.html    |   1 +
 .../pdf-preview/pdf-preview.component.ts      | 105 +++++++++---------
 18 files changed, 162 insertions(+), 141 deletions(-)
 rename src/main/resources/config/liquibase/changelog/{20241110173144_changelog.xml => 20241112002519_changelog.xml} (57%)

diff --git a/src/main/java/de/tum/cit/aet/artemis/lecture/domain/Attachment.java b/src/main/java/de/tum/cit/aet/artemis/lecture/domain/Attachment.java
index ca2bb2104d85..a0e7d5ef5d49 100644
--- a/src/main/java/de/tum/cit/aet/artemis/lecture/domain/Attachment.java
+++ b/src/main/java/de/tum/cit/aet/artemis/lecture/domain/Attachment.java
@@ -61,13 +61,6 @@ public class Attachment extends DomainObject implements Serializable {
     @JoinColumn(name = "attachment_unit_id")
     private AttachmentUnit attachmentUnit;
 
-    @Column(name = "hidden_pages")
-    private String hiddenPages;
-
-    @OneToOne
-    @JoinColumn(name = "parent_attachment_id")
-    private Attachment parentAttachment;
-
     // jhipster-needle-entity-add-field - JHipster will add fields here, do not remove
 
     public String getName() {
@@ -142,22 +135,6 @@ public void setAttachmentUnit(AttachmentUnit attachmentUnit) {
         this.attachmentUnit = attachmentUnit;
     }
 
-    public String getHiddenPages() {
-        return hiddenPages;
-    }
-
-    public void setHiddenPages(String hiddenPages) {
-        this.hiddenPages = hiddenPages;
-    }
-
-    public Attachment getParentAttachment() {
-        return parentAttachment;
-    }
-
-    public void setParentAttachment(Attachment parentAttachment) {
-        this.parentAttachment = parentAttachment;
-    }
-
     public Boolean isVisibleToStudents() {
         if (releaseDate == null) {  // no release date means the attachment is visible to students
             return Boolean.TRUE;
@@ -168,7 +145,6 @@ public Boolean isVisibleToStudents() {
     @Override
     public String toString() {
         return "Attachment{" + "id=" + getId() + ", name='" + getName() + "'" + ", link='" + getLink() + "'" + ", version='" + getVersion() + "'" + ", uploadDate='"
-                + getUploadDate() + "'" + ", releaseDate='" + getReleaseDate() + "'" + ", attachmentType='" + getAttachmentType() + "'" + ", hiddenPages='" + getHiddenPages() + "'"
-                + ", parentAttachment='" + getParentAttachment() + "'" + "}";
+                + getUploadDate() + "'" + ", releaseDate='" + getReleaseDate() + "'" + ", attachmentType='" + getAttachmentType() + "'" + ", }";
     }
 }
diff --git a/src/main/java/de/tum/cit/aet/artemis/lecture/domain/AttachmentUnit.java b/src/main/java/de/tum/cit/aet/artemis/lecture/domain/AttachmentUnit.java
index 1af955b43d89..1107327567ae 100644
--- a/src/main/java/de/tum/cit/aet/artemis/lecture/domain/AttachmentUnit.java
+++ b/src/main/java/de/tum/cit/aet/artemis/lecture/domain/AttachmentUnit.java
@@ -9,9 +9,11 @@
 import jakarta.persistence.DiscriminatorValue;
 import jakarta.persistence.Entity;
 import jakarta.persistence.FetchType;
+import jakarta.persistence.JoinColumn;
 import jakarta.persistence.OneToMany;
 import jakarta.persistence.OneToOne;
 
+import com.fasterxml.jackson.annotation.JsonIgnore;
 import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
 import com.fasterxml.jackson.annotation.JsonInclude;
 
@@ -32,6 +34,14 @@ public class AttachmentUnit extends LectureUnit {
     @JsonIgnoreProperties("attachmentUnit")
     private List<Slide> slides = new ArrayList<>();
 
+    @Column(name = "hidden_pages")
+    private String hiddenPages;
+
+    @OneToOne
+    @JoinColumn(name = "parent_attachment_unit_id")
+    @JsonIgnore
+    private AttachmentUnit parentAttachmentUnit;
+
     @Override
     public boolean isVisibleToStudents() {
         if (attachment == null) {
@@ -91,4 +101,20 @@ public void setReleaseDate(ZonedDateTime releaseDate) {
     public String getType() {
         return "attachment";
     }
+
+    public String getHiddenPages() {
+        return hiddenPages;
+    }
+
+    public void setHiddenPages(String hiddenPages) {
+        this.hiddenPages = hiddenPages;
+    }
+
+    public AttachmentUnit getParentAttachmentUnit() {
+        return parentAttachmentUnit;
+    }
+
+    public void setParentAttachmentUnit(AttachmentUnit parentAttachmentUnit) {
+        this.parentAttachmentUnit = parentAttachmentUnit;
+    }
 }
diff --git a/src/main/java/de/tum/cit/aet/artemis/lecture/repository/AttachmentRepository.java b/src/main/java/de/tum/cit/aet/artemis/lecture/repository/AttachmentRepository.java
index fc7a355223bc..30b1068ed687 100644
--- a/src/main/java/de/tum/cit/aet/artemis/lecture/repository/AttachmentRepository.java
+++ b/src/main/java/de/tum/cit/aet/artemis/lecture/repository/AttachmentRepository.java
@@ -29,11 +29,4 @@ public interface AttachmentRepository extends ArtemisJpaRepository<Attachment, L
     default Attachment findByIdOrElseThrow(Long attachmentId) {
         return getValueElseThrow(findById(attachmentId), attachmentId);
     }
-
-    @Query("""
-            SELECT a
-            FROM Attachment a
-            WHERE a.parentAttachment.id = :parentAttachmentId
-            """)
-    Attachment findAttachmentByParentAttachmentId(@Param("parentAttachmentId") Long parentAttachmentId);
 }
diff --git a/src/main/java/de/tum/cit/aet/artemis/lecture/repository/AttachmentUnitRepository.java b/src/main/java/de/tum/cit/aet/artemis/lecture/repository/AttachmentUnitRepository.java
index 61f268d75b95..2a4774fa6e87 100644
--- a/src/main/java/de/tum/cit/aet/artemis/lecture/repository/AttachmentUnitRepository.java
+++ b/src/main/java/de/tum/cit/aet/artemis/lecture/repository/AttachmentUnitRepository.java
@@ -63,4 +63,12 @@ default List<AttachmentUnit> findAllByLectureIdAndAttachmentTypeElseThrow(Long l
             WHERE attachmentUnit.id = :attachmentUnitId
             """)
     AttachmentUnit findOneWithSlidesAndCompetencies(@Param("attachmentUnitId") long attachmentUnitId);
+
+    @Query("""
+            SELECT attachmentUnit
+            FROM AttachmentUnit attachmentUnit
+            WHERE attachmentUnit.lecture.id = :lectureId
+                 AND attachmentUnit.parentAttachmentUnit.id = :parentAttachmentUnitId
+            """)
+    AttachmentUnit findAttachmentUnitByLectureIdAndParentAttachmentUnitId(@Param("lectureId") Long lectureId, @Param("parentAttachmentUnitId") Long parentAttachmentUnitId);
 }
diff --git a/src/main/java/de/tum/cit/aet/artemis/lecture/service/AttachmentUnitService.java b/src/main/java/de/tum/cit/aet/artemis/lecture/service/AttachmentUnitService.java
index e86d7c22e7f5..7f9da38f5f5d 100644
--- a/src/main/java/de/tum/cit/aet/artemis/lecture/service/AttachmentUnitService.java
+++ b/src/main/java/de/tum/cit/aet/artemis/lecture/service/AttachmentUnitService.java
@@ -117,6 +117,7 @@ public AttachmentUnit updateAttachmentUnit(AttachmentUnit existingAttachmentUnit
         existingAttachmentUnit.setDescription(updateUnit.getDescription());
         existingAttachmentUnit.setName(updateUnit.getName());
         existingAttachmentUnit.setReleaseDate(updateUnit.getReleaseDate());
+        existingAttachmentUnit.setHiddenPages(updateUnit.getHiddenPages());
 
         AttachmentUnit savedAttachmentUnit = lectureUnitService.saveWithCompetencyLinks(existingAttachmentUnit, attachmentUnitRepository::saveAndFlush);
 
diff --git a/src/main/java/de/tum/cit/aet/artemis/lecture/web/AttachmentResource.java b/src/main/java/de/tum/cit/aet/artemis/lecture/web/AttachmentResource.java
index aeb10b752e16..3b5e44b6ac2f 100644
--- a/src/main/java/de/tum/cit/aet/artemis/lecture/web/AttachmentResource.java
+++ b/src/main/java/de/tum/cit/aet/artemis/lecture/web/AttachmentResource.java
@@ -210,17 +210,4 @@ else if (attachment.getExercise() != null) {
         }
         return ResponseEntity.ok().headers(HeaderUtil.createEntityDeletionAlert(applicationName, true, ENTITY_NAME, attachmentId.toString())).build();
     }
-
-    /**
-     * GET /attachments/:parentAttachmentId/hiddenAttachment : retrieve the hidden attachment associated with the given parent attachment ID.
-     *
-     * @param parentAttachmentId the ID of the parent attachment for which to retrieve the hidden attachment
-     * @return the ResponseEntity with status 200 (OK) and the Attachment in the body, or a 404 (Not Found) if no matching attachment exists
-     */
-    @GetMapping("attachments/{parentAttachmentId}/hiddenAttachment")
-    @EnforceAtLeastTutor
-    public ResponseEntity<Attachment> getAttachmentByParentAttachmentId(@PathVariable Long parentAttachmentId) {
-        log.debug("REST request to get attachment by the parent attachment Id : {}", parentAttachmentId);
-        return ResponseEntity.ok(attachmentRepository.findAttachmentByParentAttachmentId(parentAttachmentId));
-    }
 }
diff --git a/src/main/java/de/tum/cit/aet/artemis/lecture/web/AttachmentUnitResource.java b/src/main/java/de/tum/cit/aet/artemis/lecture/web/AttachmentUnitResource.java
index 0c7c2996e162..07a839a6c930 100644
--- a/src/main/java/de/tum/cit/aet/artemis/lecture/web/AttachmentUnitResource.java
+++ b/src/main/java/de/tum/cit/aet/artemis/lecture/web/AttachmentUnitResource.java
@@ -36,6 +36,7 @@
 import de.tum.cit.aet.artemis.core.exception.InternalServerErrorException;
 import de.tum.cit.aet.artemis.core.security.Role;
 import de.tum.cit.aet.artemis.core.security.annotations.EnforceAtLeastEditor;
+import de.tum.cit.aet.artemis.core.security.annotations.EnforceAtLeastTutor;
 import de.tum.cit.aet.artemis.core.service.AuthorizationCheckService;
 import de.tum.cit.aet.artemis.core.service.FileService;
 import de.tum.cit.aet.artemis.lecture.domain.Attachment;
@@ -332,4 +333,18 @@ private void checkFile(Path filePath) {
             throw new BadRequestAlertException("The file must be a pdf", ENTITY_NAME, "wrongFileType");
         }
     }
+
+    /**
+     * GET /lectures/:lectureId/attachment-units/:parentAttachmentUnitId/hiddenAttachment : retrieve the hidden attachment associated with the given parent attachment ID.
+     *
+     * @param lectureId              the ID of the lecture to which the attachment unit belongs
+     * @param parentAttachmentUnitId the ID of the parent attachment unit for which to retrieve the hidden attachment unit
+     * @return the ResponseEntity with status 200 (OK) and the Attachment in the body, or a 404 (Not Found) if no matching attachment exists
+     */
+    @GetMapping("lectures/{lectureId}/attachment-units/{parentAttachmentUnitId}/hiddenAttachment")
+    @EnforceAtLeastTutor
+    public ResponseEntity<AttachmentUnit> getAttachmentByParentAttachmentId(@PathVariable Long lectureId, @PathVariable Long parentAttachmentUnitId) {
+        log.debug("REST request to get attachment unit by the parent attachment unit Id : {}", parentAttachmentUnitId);
+        return ResponseEntity.ok(attachmentUnitRepository.findAttachmentUnitByLectureIdAndParentAttachmentUnitId(lectureId, parentAttachmentUnitId));
+    }
 }
diff --git a/src/main/resources/config/liquibase/changelog/20241110173144_changelog.xml b/src/main/resources/config/liquibase/changelog/20241112002519_changelog.xml
similarity index 57%
rename from src/main/resources/config/liquibase/changelog/20241110173144_changelog.xml
rename to src/main/resources/config/liquibase/changelog/20241112002519_changelog.xml
index c36a705137ba..8157408b9c6e 100644
--- a/src/main/resources/config/liquibase/changelog/20241110173144_changelog.xml
+++ b/src/main/resources/config/liquibase/changelog/20241112002519_changelog.xml
@@ -2,21 +2,21 @@
 <databaseChangeLog xmlns="http://www.liquibase.org/xml/ns/dbchangelog"
                    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
                    xsi:schemaLocation="http://www.liquibase.org/xml/ns/dbchangelog https://www.liquibase.org/xml/ns/dbchangelog/dbchangelog-latest.xsd">
-    <changeSet id="20241110173144" author="ece.eren">
-        <addColumn tableName="attachment">
+    <changeSet id="20241112002519" author="ece.eren">
+        <addColumn tableName="lecture_unit">
             <column name="hidden_pages" type="VARCHAR(255)"/>
         </addColumn>
 
-        <addColumn tableName="attachment">
-            <column name="parent_attachment_id" type="BIGINT"/>
+        <addColumn tableName="lecture_unit">
+            <column name="parent_attachment_unit_id" type="BIGINT"/>
         </addColumn>
 
         <addForeignKeyConstraint
-                baseTableName="attachment"
-                baseColumnNames="parent_attachment_id"
-                referencedTableName="attachment"
+                baseTableName="lecture_unit"
+                baseColumnNames="parent_attachment_unit_id"
+                referencedTableName="lecture_unit"
                 referencedColumnNames="id"
-                constraintName="fk_attachment_parent_attachment_id"
+                constraintName="fk_attachment_unit_parent_attachment_unit_id"
                 onDelete="CASCADE"/>
     </changeSet>
 </databaseChangeLog>
diff --git a/src/main/resources/config/liquibase/master.xml b/src/main/resources/config/liquibase/master.xml
index d3cecd760366..d6fec267baac 100644
--- a/src/main/resources/config/liquibase/master.xml
+++ b/src/main/resources/config/liquibase/master.xml
@@ -32,7 +32,7 @@
     <include file="classpath:config/liquibase/changelog/20241010101010_changelog.xml" relativeToChangelogFile="false"/>
     <include file="classpath:config/liquibase/changelog/20241018053210_changelog.xml" relativeToChangelogFile="false"/>
     <include file="classpath:config/liquibase/changelog/20241023456789_changelog.xml" relativeToChangelogFile="false"/>
-    <include file="classpath:config/liquibase/changelog/20241110173144_changelog.xml" relativeToChangelogFile="false"/>
+    <include file="classpath:config/liquibase/changelog/20241112002519_changelog.xml" relativeToChangelogFile="false"/>
 
     <!-- NOTE: please use the format "YYYYMMDDhhmmss_changelog.xml", i.e. year month day hour minutes seconds and not something else! -->
     <!-- we should also stay in a chronological order! -->
diff --git a/src/main/webapp/app/entities/attachment.model.ts b/src/main/webapp/app/entities/attachment.model.ts
index a169618ca2ca..c070019513ee 100644
--- a/src/main/webapp/app/entities/attachment.model.ts
+++ b/src/main/webapp/app/entities/attachment.model.ts
@@ -20,8 +20,6 @@ export class Attachment implements BaseEntity {
     lecture?: Lecture;
     exercise?: Exercise;
     attachmentUnit?: AttachmentUnit;
-    hiddenPages?: string;
-    parentAttachment?: Attachment;
 
     constructor() {}
 }
diff --git a/src/main/webapp/app/entities/lecture-unit/attachmentUnit.model.ts b/src/main/webapp/app/entities/lecture-unit/attachmentUnit.model.ts
index 9d1e9986329e..0baa633022fa 100644
--- a/src/main/webapp/app/entities/lecture-unit/attachmentUnit.model.ts
+++ b/src/main/webapp/app/entities/lecture-unit/attachmentUnit.model.ts
@@ -6,6 +6,8 @@ export class AttachmentUnit extends LectureUnit {
     public description?: string;
     public attachment?: Attachment;
     public slides?: Slide[];
+    public hiddenPages?: string;
+    public parentAttachmentUnit?: AttachmentUnit;
 
     constructor() {
         super(LectureUnitType.ATTACHMENT);
diff --git a/src/main/webapp/app/lecture/attachment.service.ts b/src/main/webapp/app/lecture/attachment.service.ts
index ae576a073e86..446d26960f8b 100644
--- a/src/main/webapp/app/lecture/attachment.service.ts
+++ b/src/main/webapp/app/lecture/attachment.service.ts
@@ -147,16 +147,4 @@ export class AttachmentService {
     getAttachmentFile(courseId: number, attachmentId: number): Observable<Blob> {
         return this.http.get(`api/files/courses/${courseId}/attachments/${attachmentId}`, { responseType: 'blob' });
     }
-
-    /**
-     * Retrieve the hidden attachment associated with a given parent attachment ID
-     *
-     * @param parentAttachmentId The ID of the parent attachment whose hidden attachment is to be retrieved
-     * @returns An Observable that emits an EntityResponseType containing the Attachment object when the HTTP request completes successfully
-     */
-    getAttachmentByParentAttachmentId(parentAttachmentId: number): Observable<EntityResponseType> {
-        return this.http
-            .get<Attachment>(`${this.resourceUrl}/${parentAttachmentId}/hiddenAttachment`, { observe: 'response' })
-            .pipe(map((res: EntityResponseType) => this.convertAttachmentResponseDatesFromServer(res)));
-    }
 }
diff --git a/src/main/webapp/app/lecture/lecture-unit/lecture-unit-management/attachment-unit-form/attachment-unit-form.component.ts b/src/main/webapp/app/lecture/lecture-unit/lecture-unit-management/attachment-unit-form/attachment-unit-form.component.ts
index 766379c5847b..40ae7faf8e9c 100644
--- a/src/main/webapp/app/lecture/lecture-unit/lecture-unit-management/attachment-unit-form/attachment-unit-form.component.ts
+++ b/src/main/webapp/app/lecture/lecture-unit/lecture-unit-management/attachment-unit-form/attachment-unit-form.component.ts
@@ -6,6 +6,7 @@ import { faQuestionCircle, faTimes } from '@fortawesome/free-solid-svg-icons';
 import { UPLOAD_FILE_EXTENSIONS } from 'app/shared/constants/file-extensions.constants';
 import { CompetencyLectureUnitLink } from 'app/entities/competency.model';
 import { MAX_FILE_SIZE } from 'app/shared/constants/input.constants';
+import { AttachmentUnit } from 'app/entities/lecture-unit/attachmentUnit.model';
 
 export interface AttachmentUnitFormData {
     formProperties: FormProperties;
@@ -20,6 +21,8 @@ export interface FormProperties {
     version?: number;
     updateNotificationText?: string;
     competencyLinks?: CompetencyLectureUnitLink[];
+    hiddenPages?: string;
+    parentAttachmentUnit?: AttachmentUnit;
 }
 
 // file input is a special case and is not included in the reactive form structure
diff --git a/src/main/webapp/app/lecture/lecture-unit/lecture-unit-management/attachmentUnit.service.ts b/src/main/webapp/app/lecture/lecture-unit/lecture-unit-management/attachmentUnit.service.ts
index 533d454f9a06..ccb02546d0da 100644
--- a/src/main/webapp/app/lecture/lecture-unit/lecture-unit-management/attachmentUnit.service.ts
+++ b/src/main/webapp/app/lecture/lecture-unit/lecture-unit-management/attachmentUnit.service.ts
@@ -71,4 +71,17 @@ export class AttachmentUnitService {
     getAttachmentFile(courseId: number, attachmentUnitId: number): Observable<Blob> {
         return this.httpClient.get(`${this.resourceURL}/files/courses/${courseId}/attachment-units/${attachmentUnitId}`, { responseType: 'blob' });
     }
+
+    /**
+     * Retrieve the hidden attachment unit associated with a given parent attachment unit ID
+     *
+     * @param lectureId The ID of the lecture that the attachment unit belongs to
+     * @param parentAttachmentUnitId The ID of the parent attachment unit whose hidden attachment unit is to be retrieved
+     * @returns An Observable that emits an EntityResponseType containing the Attachment object when the HTTP request completes successfully
+     */
+    getAttachmentUnitByParentAttachmentUnitId(lectureId: number, parentAttachmentUnitId: number): Observable<EntityResponseType> {
+        return this.httpClient
+            .get<AttachmentUnit>(`${this.resourceURL}/lectures/${lectureId}/attachment-units/${parentAttachmentUnitId}/hiddenAttachment`, { observe: 'response' })
+            .pipe(map((res: EntityResponseType) => this.lectureUnitService.convertLectureUnitResponseDatesFromServer(res)));
+    }
 }
diff --git a/src/main/webapp/app/lecture/lecture-unit/lecture-unit-management/create-attachment-unit/create-attachment-unit.component.ts b/src/main/webapp/app/lecture/lecture-unit/lecture-unit-management/create-attachment-unit/create-attachment-unit.component.ts
index 55a07861bac9..fab8f71dba61 100644
--- a/src/main/webapp/app/lecture/lecture-unit/lecture-unit-management/create-attachment-unit/create-attachment-unit.component.ts
+++ b/src/main/webapp/app/lecture/lecture-unit/lecture-unit-management/create-attachment-unit/create-attachment-unit.component.ts
@@ -47,7 +47,7 @@ export class CreateAttachmentUnitComponent implements OnInit {
         if (!attachmentUnitFormData?.formProperties?.name || !attachmentUnitFormData?.fileProperties?.file || !attachmentUnitFormData?.fileProperties?.fileName) {
             return;
         }
-        const { description, name, releaseDate, competencyLinks } = attachmentUnitFormData.formProperties;
+        const { description, name, releaseDate, competencyLinks, hiddenPages, parentAttachmentUnit } = attachmentUnitFormData.formProperties;
         const { file, fileName } = attachmentUnitFormData.fileProperties;
 
         // === Setting attachment ===
@@ -60,6 +60,8 @@ export class CreateAttachmentUnitComponent implements OnInit {
         // === Setting attachmentUnit ===
         this.attachmentUnitToCreate.description = description;
         this.attachmentUnitToCreate.competencyLinks = competencyLinks || [];
+        this.attachmentUnitToCreate.hiddenPages = hiddenPages;
+        this.attachmentUnitToCreate.parentAttachmentUnit = parentAttachmentUnit;
 
         this.isLoading = true;
 
diff --git a/src/main/webapp/app/lecture/pdf-preview/pdf-preview-thumbnail-grid/pdf-preview-thumbnail-grid.component.ts b/src/main/webapp/app/lecture/pdf-preview/pdf-preview-thumbnail-grid/pdf-preview-thumbnail-grid.component.ts
index e74093fd8400..50bd4e11433d 100644
--- a/src/main/webapp/app/lecture/pdf-preview/pdf-preview-thumbnail-grid/pdf-preview-thumbnail-grid.component.ts
+++ b/src/main/webapp/app/lecture/pdf-preview/pdf-preview-thumbnail-grid/pdf-preview-thumbnail-grid.component.ts
@@ -23,6 +23,7 @@ export class PdfPreviewThumbnailGridComponent {
     currentPdfUrl = input<string>();
     appendFile = input<boolean>();
     hiddenPages = input<Set<number>>();
+    isAttachmentUnit = input<boolean>();
 
     // Signals
     isEnlargedView = signal<boolean>(false);
@@ -141,24 +142,30 @@ export class PdfPreviewThumbnailGridComponent {
 
         const overlay = this.createOverlay(pageIndex);
         const checkbox = this.createCheckbox(pageIndex);
-        const hideShowButton = this.createHideShowButton(pageIndex, container);
+
         container.appendChild(canvas);
         container.appendChild(overlay);
         container.appendChild(checkbox);
-        container.appendChild(hideShowButton);
 
         container.addEventListener('mouseenter', () => {
             overlay.style.opacity = '1';
-            hideShowButton.style.opacity = '1';
         });
         container.addEventListener('mouseleave', () => {
             overlay.style.opacity = '0';
-            hideShowButton.style.opacity = '0';
         });
-
-        hideShowButton.addEventListener('click', () => this.toggleVisibility(container, hideShowButton));
         overlay.addEventListener('click', () => this.displayEnlargedCanvas(canvas));
 
+        if (this.isAttachmentUnit()) {
+            const hideShowButton = this.createHideShowButton(pageIndex, container);
+            container.appendChild(hideShowButton);
+            container.addEventListener('mouseenter', () => {
+                hideShowButton.style.opacity = '1';
+            });
+            container.addEventListener('mouseleave', () => {
+                hideShowButton.style.opacity = '0';
+            });
+            hideShowButton.addEventListener('click', () => this.toggleVisibility(pageIndex, container, hideShowButton));
+        }
         return container;
     }
 
@@ -201,14 +208,14 @@ export class PdfPreviewThumbnailGridComponent {
     }
 
     private createHideShowButton(pageIndex: number, container: HTMLDivElement): HTMLAnchorElement {
-        const hideButton = document.createElement('a');
-        hideButton.type = 'button';
-        hideButton.style.cssText = `opacity: 0; position: absolute; bottom: -20px; left: 50%; transform: translateX(-50%); cursor: pointer; z-index: 4;`;
+        const hideShowButton = document.createElement('a');
+        hideShowButton.type = 'button';
+        hideShowButton.style.cssText = `opacity: 0; position: absolute; bottom: -20px; left: 50%; transform: translateX(-50%); cursor: pointer; z-index: 4;`;
 
         if (this.hiddenPages()!.has(pageIndex)) {
-            hideButton.className = 'btn btn-success';
-            hideButton.id = `show-button-${pageIndex}`;
-            hideButton.innerHTML = `<i class="fa fa-eye"></i>`;
+            hideShowButton.className = 'btn btn-success';
+            hideShowButton.id = `show-button-${pageIndex}`;
+            hideShowButton.innerHTML = `<i class="fa fa-eye"></i>`;
 
             const overlay = document.createElement('div');
             overlay.id = 'pdf-page-overlay';
@@ -220,15 +227,15 @@ export class PdfPreviewThumbnailGridComponent {
 
             container.appendChild(overlay);
         } else {
-            hideButton.className = 'btn btn-secondary';
-            hideButton.id = `hide-button-${pageIndex}`;
-            hideButton.innerHTML = `<i class="fa fa-eye-slash"></i>`;
+            hideShowButton.className = 'btn btn-secondary';
+            hideShowButton.id = `hide-button-${pageIndex}`;
+            hideShowButton.innerHTML = `<i class="fa fa-eye-slash"></i>`;
         }
 
-        return hideButton;
+        return hideShowButton;
     }
 
-    private toggleVisibility(container: HTMLDivElement, hideShowButton: HTMLAnchorElement): void {
+    private toggleVisibility(pageIndex: number, container: HTMLDivElement, hideShowButton: HTMLAnchorElement): void {
         const overlay = document.createElement('div');
         overlay.id = 'pdf-page-overlay';
         overlay.style.cssText = `position: absolute; top: 0; width: 100%; height: 100%; z-index: 1; transition: opacity 0.3s ease; background-color: var(--pdf-preview-container-overlay)`;
@@ -241,12 +248,14 @@ export class PdfPreviewThumbnailGridComponent {
             container.appendChild(overlay);
             hideShowButton.className = 'btn btn-success';
             hideShowButton.children[0].className = 'fa fa-eye';
-            this.newHiddenPages().add(Number(hideShowButton.id.split('-')[2]));
+            hideShowButton.id = `show-button-${pageIndex}`;
+            this.newHiddenPages().add(pageIndex);
         } else {
             container.removeChild(container.querySelector(`#pdf-page-overlay`)!);
             hideShowButton.className = 'btn btn-secondary';
             hideShowButton.children[0].className = 'fa fa-eye-slash';
-            this.newHiddenPages().delete(Number(hideShowButton.id.split('-')[2]));
+            hideShowButton.id = `hide-button-${pageIndex}`;
+            this.newHiddenPages().delete(Number(pageIndex));
         }
         this.newHiddenPagesOutput.emit(this.newHiddenPages());
     }
diff --git a/src/main/webapp/app/lecture/pdf-preview/pdf-preview.component.html b/src/main/webapp/app/lecture/pdf-preview/pdf-preview.component.html
index dd0276af421f..1861481a86c6 100644
--- a/src/main/webapp/app/lecture/pdf-preview/pdf-preview.component.html
+++ b/src/main/webapp/app/lecture/pdf-preview/pdf-preview.component.html
@@ -44,6 +44,7 @@ <h4>
                 [currentPdfUrl]="currentPdfUrl()"
                 [appendFile]="appendFile()"
                 [hiddenPages]="hiddenPages()"
+                [isAttachmentUnit]="!!attachmentUnit()"
                 (isPdfLoading)="isPdfLoading.set($event)"
                 (selectedPagesOutput)="selectedPages.set($event)"
                 (totalPagesOutput)="totalPages.set($event)"
diff --git a/src/main/webapp/app/lecture/pdf-preview/pdf-preview.component.ts b/src/main/webapp/app/lecture/pdf-preview/pdf-preview.component.ts
index 0f0c8feded99..d759b56c5cb0 100644
--- a/src/main/webapp/app/lecture/pdf-preview/pdf-preview.component.ts
+++ b/src/main/webapp/app/lecture/pdf-preview/pdf-preview.component.ts
@@ -69,7 +69,6 @@ export class PdfPreviewComponent implements OnInit, OnDestroy {
 
             if ('attachment' in data) {
                 this.attachment.set(data.attachment);
-                this.hiddenPages.set(new Set(data.attachment.hiddenPages?.split(',').map(Number) || []));
                 this.attachmentSub = this.attachmentService.getAttachmentFile(this.course()!.id!, this.attachment()!.id!).subscribe({
                     next: (blob: Blob) => {
                         this.currentPdfBlob.set(blob);
@@ -79,7 +78,7 @@ export class PdfPreviewComponent implements OnInit, OnDestroy {
                 });
             } else if ('attachmentUnit' in data) {
                 this.attachmentUnit.set(data.attachmentUnit);
-                this.hiddenPages.set(new Set(data.attachmentUnit.attachment.hiddenPages?.split(',').map(Number) || []));
+                this.hiddenPages.set(new Set(data.attachmentUnit.hiddenPages?.split(',').map(Number) || []));
                 this.attachmentUnitSub = this.attachmentUnitService.getAttachmentFile(this.course()!.id!, this.attachmentUnit()!.id!).subscribe({
                     next: (blob: Blob) => {
                         this.currentPdfBlob.set(blob);
@@ -134,6 +133,12 @@ export class PdfPreviewComponent implements OnInit, OnDestroy {
         return false;
     }
 
+    getHiddenPages() {
+        return Array.from(document.querySelectorAll('[id^="show-button-"]'))
+            .map((el) => el.id.match(/show-button-(\d+)/)?.[1])
+            .join(',');
+    }
+
     /**
      * Updates the existing attachment file or creates a new hidden version of the attachment.
      */
@@ -149,58 +154,22 @@ export class PdfPreviewComponent implements OnInit, OnDestroy {
             this.attachmentToBeEdited.set(this.attachment());
             this.attachmentToBeEdited()!.version!++;
             this.attachmentToBeEdited()!.uploadDate = dayjs();
-            this.attachmentToBeEdited()!.hiddenPages = Array.from(this.newHiddenPages()).join(',');
 
             this.attachmentService.update(this.attachmentToBeEdited()!.id!, this.attachmentToBeEdited()!, pdfFile).subscribe({
-                next: async () => {
-                    if (this.newHiddenPages().size > 0) {
-                        const pdfFileWithHiddenPages = await this.createHiddenVersionOfAttachment(Array.from(this.newHiddenPages()));
-                        this.attachmentService.getAttachmentByParentAttachmentId(this.attachment()!.id!).subscribe({
-                            next: async (attachmentRes) => {
-                                if (attachmentRes.body && attachmentRes.body.id) {
-                                    attachmentRes.body.version!++;
-                                    this.attachmentService.update(attachmentRes.body.id, attachmentRes.body, pdfFileWithHiddenPages!).subscribe({
-                                        next: () => {
-                                            this.router.navigate(['course-management', this.course()?.id, 'lectures', this.attachment()!.lecture!.id, 'attachments']);
-                                        },
-                                        error: (error) => {
-                                            this.alertService.error('artemisApp.attachment.pdfPreview.hiddenAttachmentUpdateError', { error: error.message });
-                                        },
-                                    });
-                                } else {
-                                    const attachmentWithHiddenPages = cloneDeep(this.attachment()!);
-                                    attachmentWithHiddenPages.parentAttachment = this.attachment()!;
-                                    attachmentWithHiddenPages.name = `${attachmentWithHiddenPages.name}_hidden`;
-                                    attachmentWithHiddenPages.hiddenPages = undefined;
-                                    this.attachmentService.create(attachmentWithHiddenPages, pdfFileWithHiddenPages!).subscribe({
-                                        next: () => {
-                                            this.alertService.success('artemisApp.attachment.pdfPreview.hiddenAttachmentCreateSuccess');
-                                            this.router.navigate(['course-management', this.course()?.id, 'lectures', this.attachment()!.lecture!.id, 'attachments']);
-                                        },
-                                        error: (error) => {
-                                            this.alertService.error('artemisApp.attachment.pdfPreview.hiddenAttachmentCreateError', { error: error.message });
-                                        },
-                                    });
-                                }
-                            },
-                            error: (error) => {
-                                this.alertService.error('artemisApp.attachment.pdfPreview.attachmentUpdateError', { error: error.message });
-                            },
-                        });
-                    } else {
-                        this.alertService.success('artemisApp.attachment.pdfPreview.attachmentUpdateSuccess');
-                        this.router.navigate(['course-management', this.course()?.id, 'lectures', this.attachment()!.lecture!.id, 'attachments']);
-                    }
+                next: () => {
+                    this.alertService.success('artemisApp.attachment.pdfPreview.attachmentUpdateSuccess');
+                    this.router.navigate(['course-management', this.course()?.id, 'lectures', this.attachment()!.lecture!.id, 'attachments']);
                 },
                 error: (error) => {
                     this.alertService.error('artemisApp.attachment.pdfPreview.attachmentUpdateError', { error: error.message });
                 },
             });
         } else if (this.attachmentUnit()) {
+            const finalHiddenPages = this.getHiddenPages();
             this.attachmentToBeEdited.set(this.attachmentUnit()!.attachment!);
             this.attachmentToBeEdited()!.version!++;
             this.attachmentToBeEdited()!.uploadDate = dayjs();
-            this.attachmentToBeEdited()!.hiddenPages = Array.from(this.hiddenPages()).join(',');
+            this.attachmentUnit()!.hiddenPages = finalHiddenPages;
 
             const formData = new FormData();
             formData.append('file', pdfFile);
@@ -209,18 +178,48 @@ export class PdfPreviewComponent implements OnInit, OnDestroy {
 
             this.attachmentUnitService.update(this.attachmentUnit()!.lecture!.id!, this.attachmentUnit()!.id!, formData).subscribe({
                 next: async () => {
-                    if (this.hiddenPages().size > 0) {
-                        const attachmentWithHiddenPages = cloneDeep(this.attachmentUnit()?.attachment!);
-                        attachmentWithHiddenPages.parentAttachment = this.attachmentUnit()?.attachment!;
-                        const pdfFileWithHiddenPages = await this.createHiddenVersionOfAttachment(Array.from(this.hiddenPages()));
+                    if (finalHiddenPages!.length > 0) {
+                        const pdfFileWithHiddenPages = await this.createHiddenVersionOfAttachment(Array.from(finalHiddenPages!.split(',').map(Number)));
+                        const attachmentUnitWithHiddenPages = cloneDeep(this.attachmentUnit()!);
+                        const attachmentWithHiddenPages = cloneDeep(this.attachmentUnit()!.attachment!);
+
+                        attachmentWithHiddenPages.id = undefined;
+                        attachmentWithHiddenPages.name = `${attachmentWithHiddenPages.name}_hidden`;
+                        attachmentUnitWithHiddenPages.id = undefined;
+                        attachmentUnitWithHiddenPages.hiddenPages = undefined;
+                        attachmentUnitWithHiddenPages.parentAttachmentUnit = this.attachmentUnit();
+
+                        const formData = new FormData();
 
                         formData.append('file', pdfFileWithHiddenPages!);
-                        formData.append('attachment', objectToJsonBlob(attachmentWithHiddenPages));
+                        formData.append('attachment', objectToJsonBlob(attachmentWithHiddenPages!));
+                        formData.append('attachmentUnit', objectToJsonBlob(attachmentUnitWithHiddenPages!));
 
-                        this.attachmentUnitService.create(formData, this.attachmentUnit()?.lecture!.id!).subscribe({
-                            next: () => {
-                                this.alertService.success('artemisApp.attachment.pdfPreview.attachmentUpdateSuccess');
-                                this.router.navigate(['course-management', this.course()?.id, 'lectures', this.attachmentUnit()!.lecture!.id, 'unit-management']);
+                        this.attachmentUnitService.getAttachmentUnitByParentAttachmentUnitId(this.attachmentUnit()!.lecture!.id!, this.attachmentUnit()!.id!).subscribe({
+                            next: async (attachmentUnitRes) => {
+                                if (attachmentUnitRes.body && attachmentUnitRes.body.id) {
+                                    this.attachmentUnitService.update(this.attachmentUnit()!.lecture!.id!, attachmentUnitRes.body.id, formData).subscribe({
+                                        next: () => {
+                                            this.alertService.success('artemisApp.attachment.pdfPreview.attachmentUpdateSuccess');
+                                            this.alertService.success('artemisApp.attachment.pdfPreview.hiddenAttachmentUnitUpdateSuccess');
+                                            this.router.navigate(['course-management', this.course()?.id, 'lectures', this.attachmentUnit()!.lecture!.id, 'unit-management']);
+                                        },
+                                        error: (error) => {
+                                            this.alertService.error('artemisApp.attachment.pdfPreview.hiddenAttachmentUnitUpdateError', { error: error.message });
+                                        },
+                                    });
+                                } else {
+                                    this.attachmentUnitService.create(formData, this.attachmentUnit()!.lecture!.id!).subscribe({
+                                        next: () => {
+                                            this.alertService.success('artemisApp.attachment.pdfPreview.attachmentUpdateSuccess');
+                                            this.alertService.success('artemisApp.attachment.pdfPreview.hiddenAttachmentUnitCreateSuccess');
+                                            this.router.navigate(['course-management', this.course()?.id, 'lectures', this.attachmentUnit()!.lecture!.id, 'unit-management']);
+                                        },
+                                        error: (error) => {
+                                            this.alertService.error('artemisApp.attachment.pdfPreview.hiddenAttachmentUnitCreateError', { error: error.message });
+                                        },
+                                    });
+                                }
                             },
                             error: (error) => {
                                 this.alertService.error('artemisApp.attachment.pdfPreview.attachmentUpdateError', { error: error.message });
@@ -306,7 +305,7 @@ export class PdfPreviewComponent implements OnInit, OnDestroy {
      */
     async createHiddenVersionOfAttachment(hiddenPages: number[]) {
         try {
-            const fileName = this.attachment()!.name;
+            const fileName = this.attachmentUnit()!.attachment!.name;
             const existingPdfBytes = await this.currentPdfBlob()!.arrayBuffer();
             const hiddenPdfDoc = await PDFDocument.load(existingPdfBytes);
 

From a90a928e3a71234bae3d9e29cf7114a28306029a Mon Sep 17 00:00:00 2001
From: Ece Eren <aybikeceren@gmail.com>
Date: Tue, 12 Nov 2024 14:16:36 +0100
Subject: [PATCH 05/11] Fix typos

---
 .../de/tum/cit/aet/artemis/lecture/domain/Attachment.java   | 2 +-
 .../cit/aet/artemis/lecture/web/AttachmentUnitResource.java | 6 +++---
 .../lecture-unit-management/attachmentUnit.service.ts       | 2 +-
 3 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/src/main/java/de/tum/cit/aet/artemis/lecture/domain/Attachment.java b/src/main/java/de/tum/cit/aet/artemis/lecture/domain/Attachment.java
index a0e7d5ef5d49..6806850fd86b 100644
--- a/src/main/java/de/tum/cit/aet/artemis/lecture/domain/Attachment.java
+++ b/src/main/java/de/tum/cit/aet/artemis/lecture/domain/Attachment.java
@@ -145,6 +145,6 @@ public Boolean isVisibleToStudents() {
     @Override
     public String toString() {
         return "Attachment{" + "id=" + getId() + ", name='" + getName() + "'" + ", link='" + getLink() + "'" + ", version='" + getVersion() + "'" + ", uploadDate='"
-                + getUploadDate() + "'" + ", releaseDate='" + getReleaseDate() + "'" + ", attachmentType='" + getAttachmentType() + "'" + ", }";
+                + getUploadDate() + "'" + ", releaseDate='" + getReleaseDate() + "'" + ", attachmentType='" + getAttachmentType() + "'" + "}";
     }
 }
diff --git a/src/main/java/de/tum/cit/aet/artemis/lecture/web/AttachmentUnitResource.java b/src/main/java/de/tum/cit/aet/artemis/lecture/web/AttachmentUnitResource.java
index 07a839a6c930..8ec7e41248dc 100644
--- a/src/main/java/de/tum/cit/aet/artemis/lecture/web/AttachmentUnitResource.java
+++ b/src/main/java/de/tum/cit/aet/artemis/lecture/web/AttachmentUnitResource.java
@@ -335,15 +335,15 @@ private void checkFile(Path filePath) {
     }
 
     /**
-     * GET /lectures/:lectureId/attachment-units/:parentAttachmentUnitId/hiddenAttachment : retrieve the hidden attachment associated with the given parent attachment ID.
+     * GET /lectures/:lectureId/attachment-units/:parentAttachmentUnitId/hiddenAttachment : retrieve the hidden attachment unit associated with the given parent attachment unit ID.
      *
      * @param lectureId              the ID of the lecture to which the attachment unit belongs
      * @param parentAttachmentUnitId the ID of the parent attachment unit for which to retrieve the hidden attachment unit
-     * @return the ResponseEntity with status 200 (OK) and the Attachment in the body, or a 404 (Not Found) if no matching attachment exists
+     * @return the ResponseEntity with status 200 (OK) and the AttachmentUnit in the body, or a 404 (Not Found) if no matching attachment unit exists
      */
     @GetMapping("lectures/{lectureId}/attachment-units/{parentAttachmentUnitId}/hiddenAttachment")
     @EnforceAtLeastTutor
-    public ResponseEntity<AttachmentUnit> getAttachmentByParentAttachmentId(@PathVariable Long lectureId, @PathVariable Long parentAttachmentUnitId) {
+    public ResponseEntity<AttachmentUnit> getAttachmentUnitByParentAttachmentUnitId(@PathVariable Long lectureId, @PathVariable Long parentAttachmentUnitId) {
         log.debug("REST request to get attachment unit by the parent attachment unit Id : {}", parentAttachmentUnitId);
         return ResponseEntity.ok(attachmentUnitRepository.findAttachmentUnitByLectureIdAndParentAttachmentUnitId(lectureId, parentAttachmentUnitId));
     }
diff --git a/src/main/webapp/app/lecture/lecture-unit/lecture-unit-management/attachmentUnit.service.ts b/src/main/webapp/app/lecture/lecture-unit/lecture-unit-management/attachmentUnit.service.ts
index ccb02546d0da..d2a33f5f2a06 100644
--- a/src/main/webapp/app/lecture/lecture-unit/lecture-unit-management/attachmentUnit.service.ts
+++ b/src/main/webapp/app/lecture/lecture-unit/lecture-unit-management/attachmentUnit.service.ts
@@ -77,7 +77,7 @@ export class AttachmentUnitService {
      *
      * @param lectureId The ID of the lecture that the attachment unit belongs to
      * @param parentAttachmentUnitId The ID of the parent attachment unit whose hidden attachment unit is to be retrieved
-     * @returns An Observable that emits an EntityResponseType containing the Attachment object when the HTTP request completes successfully
+     * @returns An Observable that emits an EntityResponseType containing the Attachment Unit object when the HTTP request completes successfully
      */
     getAttachmentUnitByParentAttachmentUnitId(lectureId: number, parentAttachmentUnitId: number): Observable<EntityResponseType> {
         return this.httpClient

From 10b9133b5966f02ad4ba83355faa680ae3a01a21 Mon Sep 17 00:00:00 2001
From: Ece Eren <aybikeceren@gmail.com>
Date: Tue, 12 Nov 2024 16:48:11 +0100
Subject: [PATCH 06/11] Fix parentAttachmentId problem

---
 .../lecture/service/AttachmentUnitService.java   |  4 +++-
 .../service/LectureUnitProcessingService.java    |  2 +-
 .../lecture/web/AttachmentUnitResource.java      | 16 +++++++++-------
 .../attachment-unit-form.component.ts            |  2 --
 .../create-attachment-unit.component.ts          |  3 +--
 .../lecture/pdf-preview/pdf-preview.component.ts |  3 ++-
 src/main/webapp/i18n/en/lecture.json             |  6 +++++-
 7 files changed, 21 insertions(+), 15 deletions(-)

diff --git a/src/main/java/de/tum/cit/aet/artemis/lecture/service/AttachmentUnitService.java b/src/main/java/de/tum/cit/aet/artemis/lecture/service/AttachmentUnitService.java
index 7f9da38f5f5d..7ca722fb2b49 100644
--- a/src/main/java/de/tum/cit/aet/artemis/lecture/service/AttachmentUnitService.java
+++ b/src/main/java/de/tum/cit/aet/artemis/lecture/service/AttachmentUnitService.java
@@ -77,12 +77,14 @@ public AttachmentUnitService(SlideRepository slideRepository, SlideSplitterServi
      * @param keepFilename   Whether to keep the original filename or not.
      * @return The created attachment unit
      */
-    public AttachmentUnit createAttachmentUnit(AttachmentUnit attachmentUnit, Attachment attachment, Lecture lecture, MultipartFile file, boolean keepFilename) {
+    public AttachmentUnit createAttachmentUnit(AttachmentUnit attachmentUnit, Attachment attachment, Lecture lecture, AttachmentUnit parentAttachmentUnit, MultipartFile file,
+            boolean keepFilename) {
         // persist lecture unit before lecture to prevent "null index column for collection" error
         attachmentUnit.setLecture(null);
 
         AttachmentUnit savedAttachmentUnit = lectureUnitService.saveWithCompetencyLinks(attachmentUnit, attachmentUnitRepository::saveAndFlush);
 
+        savedAttachmentUnit.setParentAttachmentUnit(parentAttachmentUnit);
         attachmentUnit.setLecture(lecture);
         lecture.addLectureUnit(savedAttachmentUnit);
 
diff --git a/src/main/java/de/tum/cit/aet/artemis/lecture/service/LectureUnitProcessingService.java b/src/main/java/de/tum/cit/aet/artemis/lecture/service/LectureUnitProcessingService.java
index 602106099847..1a770071b687 100644
--- a/src/main/java/de/tum/cit/aet/artemis/lecture/service/LectureUnitProcessingService.java
+++ b/src/main/java/de/tum/cit/aet/artemis/lecture/service/LectureUnitProcessingService.java
@@ -108,7 +108,7 @@ public List<AttachmentUnit> splitAndSaveUnits(LectureUnitSplitInformationDTO lec
                 attachment.setUploadDate(ZonedDateTime.now());
 
                 MultipartFile multipartFile = fileService.convertByteArrayToMultipart(lectureUnit.unitName(), ".pdf", outputStream.toByteArray());
-                AttachmentUnit savedAttachmentUnit = attachmentUnitService.createAttachmentUnit(attachmentUnit, attachment, lecture, multipartFile, true);
+                AttachmentUnit savedAttachmentUnit = attachmentUnitService.createAttachmentUnit(attachmentUnit, attachment, lecture, null, multipartFile, true);
                 slideSplitterService.splitAttachmentUnitIntoSingleSlides(documentUnits.getFirst(), savedAttachmentUnit, multipartFile.getOriginalFilename());
                 documentUnits.getFirst().close(); // make sure to close the document
                 units.add(savedAttachmentUnit);
diff --git a/src/main/java/de/tum/cit/aet/artemis/lecture/web/AttachmentUnitResource.java b/src/main/java/de/tum/cit/aet/artemis/lecture/web/AttachmentUnitResource.java
index 8ec7e41248dc..9a504b83020a 100644
--- a/src/main/java/de/tum/cit/aet/artemis/lecture/web/AttachmentUnitResource.java
+++ b/src/main/java/de/tum/cit/aet/artemis/lecture/web/AttachmentUnitResource.java
@@ -142,18 +142,20 @@ public ResponseEntity<AttachmentUnit> updateAttachmentUnit(@PathVariable Long le
     /**
      * POST lectures/:lectureId/attachment-units : creates a new attachment unit.
      *
-     * @param lectureId      the id of the lecture to which the attachment unit should be added
-     * @param attachmentUnit the attachment unit that should be created
-     * @param attachment     the attachment that should be created
-     * @param file           the file to upload
-     * @param keepFilename   specifies if the original filename should be kept or not
+     * @param lectureId            the id of the lecture to which the attachment unit should be added
+     * @param attachmentUnit       the attachment unit that should be created
+     * @param attachment           the attachment that should be created
+     * @param parentAttachmentUnit the parent attachment unit of the new attachment unit
+     * @param file                 the file to upload
+     * @param keepFilename         specifies if the original filename should be kept or not
      * @return the ResponseEntity with status 201 (Created) and with body the new attachment unit
      * @throws URISyntaxException if the Location URI syntax is incorrect
      */
     @PostMapping(value = "lectures/{lectureId}/attachment-units", consumes = MediaType.MULTIPART_FORM_DATA_VALUE)
     @EnforceAtLeastEditor
     public ResponseEntity<AttachmentUnit> createAttachmentUnit(@PathVariable Long lectureId, @RequestPart AttachmentUnit attachmentUnit, @RequestPart Attachment attachment,
-            @RequestPart MultipartFile file, @RequestParam(defaultValue = "false") boolean keepFilename) throws URISyntaxException {
+            @RequestPart AttachmentUnit parentAttachmentUnit, @RequestPart MultipartFile file, @RequestParam(defaultValue = "false") boolean keepFilename)
+            throws URISyntaxException {
         log.debug("REST request to create AttachmentUnit {} with Attachment {}", attachmentUnit, attachment);
         if (attachmentUnit.getId() != null) {
             throw new BadRequestAlertException("A new attachment unit cannot already have an ID", ENTITY_NAME, "idexists");
@@ -168,7 +170,7 @@ public ResponseEntity<AttachmentUnit> createAttachmentUnit(@PathVariable Long le
         }
         authorizationCheckService.checkHasAtLeastRoleInCourseElseThrow(Role.EDITOR, lecture.getCourse(), null);
 
-        AttachmentUnit savedAttachmentUnit = attachmentUnitService.createAttachmentUnit(attachmentUnit, attachment, lecture, file, keepFilename);
+        AttachmentUnit savedAttachmentUnit = attachmentUnitService.createAttachmentUnit(attachmentUnit, attachment, lecture, parentAttachmentUnit, file, keepFilename);
         lectureRepository.save(lecture);
         if (Objects.equals(FilenameUtils.getExtension(file.getOriginalFilename()), "pdf")) {
             slideSplitterService.splitAttachmentUnitIntoSingleSlides(savedAttachmentUnit);
diff --git a/src/main/webapp/app/lecture/lecture-unit/lecture-unit-management/attachment-unit-form/attachment-unit-form.component.ts b/src/main/webapp/app/lecture/lecture-unit/lecture-unit-management/attachment-unit-form/attachment-unit-form.component.ts
index 40ae7faf8e9c..30a4a3c250db 100644
--- a/src/main/webapp/app/lecture/lecture-unit/lecture-unit-management/attachment-unit-form/attachment-unit-form.component.ts
+++ b/src/main/webapp/app/lecture/lecture-unit/lecture-unit-management/attachment-unit-form/attachment-unit-form.component.ts
@@ -6,7 +6,6 @@ import { faQuestionCircle, faTimes } from '@fortawesome/free-solid-svg-icons';
 import { UPLOAD_FILE_EXTENSIONS } from 'app/shared/constants/file-extensions.constants';
 import { CompetencyLectureUnitLink } from 'app/entities/competency.model';
 import { MAX_FILE_SIZE } from 'app/shared/constants/input.constants';
-import { AttachmentUnit } from 'app/entities/lecture-unit/attachmentUnit.model';
 
 export interface AttachmentUnitFormData {
     formProperties: FormProperties;
@@ -22,7 +21,6 @@ export interface FormProperties {
     updateNotificationText?: string;
     competencyLinks?: CompetencyLectureUnitLink[];
     hiddenPages?: string;
-    parentAttachmentUnit?: AttachmentUnit;
 }
 
 // file input is a special case and is not included in the reactive form structure
diff --git a/src/main/webapp/app/lecture/lecture-unit/lecture-unit-management/create-attachment-unit/create-attachment-unit.component.ts b/src/main/webapp/app/lecture/lecture-unit/lecture-unit-management/create-attachment-unit/create-attachment-unit.component.ts
index fab8f71dba61..adaa070f4d89 100644
--- a/src/main/webapp/app/lecture/lecture-unit/lecture-unit-management/create-attachment-unit/create-attachment-unit.component.ts
+++ b/src/main/webapp/app/lecture/lecture-unit/lecture-unit-management/create-attachment-unit/create-attachment-unit.component.ts
@@ -47,7 +47,7 @@ export class CreateAttachmentUnitComponent implements OnInit {
         if (!attachmentUnitFormData?.formProperties?.name || !attachmentUnitFormData?.fileProperties?.file || !attachmentUnitFormData?.fileProperties?.fileName) {
             return;
         }
-        const { description, name, releaseDate, competencyLinks, hiddenPages, parentAttachmentUnit } = attachmentUnitFormData.formProperties;
+        const { description, name, releaseDate, competencyLinks, hiddenPages } = attachmentUnitFormData.formProperties;
         const { file, fileName } = attachmentUnitFormData.fileProperties;
 
         // === Setting attachment ===
@@ -61,7 +61,6 @@ export class CreateAttachmentUnitComponent implements OnInit {
         this.attachmentUnitToCreate.description = description;
         this.attachmentUnitToCreate.competencyLinks = competencyLinks || [];
         this.attachmentUnitToCreate.hiddenPages = hiddenPages;
-        this.attachmentUnitToCreate.parentAttachmentUnit = parentAttachmentUnit;
 
         this.isLoading = true;
 
diff --git a/src/main/webapp/app/lecture/pdf-preview/pdf-preview.component.ts b/src/main/webapp/app/lecture/pdf-preview/pdf-preview.component.ts
index d759b56c5cb0..84fec91a967f 100644
--- a/src/main/webapp/app/lecture/pdf-preview/pdf-preview.component.ts
+++ b/src/main/webapp/app/lecture/pdf-preview/pdf-preview.component.ts
@@ -187,13 +187,14 @@ export class PdfPreviewComponent implements OnInit, OnDestroy {
                         attachmentWithHiddenPages.name = `${attachmentWithHiddenPages.name}_hidden`;
                         attachmentUnitWithHiddenPages.id = undefined;
                         attachmentUnitWithHiddenPages.hiddenPages = undefined;
-                        attachmentUnitWithHiddenPages.parentAttachmentUnit = this.attachmentUnit();
+                        //attachmentUnitWithHiddenPages.parentAttachmentUnit = this.attachmentUnit();
 
                         const formData = new FormData();
 
                         formData.append('file', pdfFileWithHiddenPages!);
                         formData.append('attachment', objectToJsonBlob(attachmentWithHiddenPages!));
                         formData.append('attachmentUnit', objectToJsonBlob(attachmentUnitWithHiddenPages!));
+                        formData.append('parentAttachmentUnit', objectToJsonBlob(this.attachmentUnit()!));
 
                         this.attachmentUnitService.getAttachmentUnitByParentAttachmentUnitId(this.attachmentUnit()!.lecture!.id!, this.attachmentUnit()!.id!).subscribe({
                             next: async (attachmentUnitRes) => {
diff --git a/src/main/webapp/i18n/en/lecture.json b/src/main/webapp/i18n/en/lecture.json
index 79525529f4c5..b0912601f5d4 100644
--- a/src/main/webapp/i18n/en/lecture.json
+++ b/src/main/webapp/i18n/en/lecture.json
@@ -109,7 +109,11 @@
                 "pageDeleteError": "Failed to delete pages: {{error}}",
                 "fileSizeError": "The file size exceeds the limit of 20MB.",
                 "deletePagesQuestion": "Are you sure you want to delete the selected pages?",
-                "deleteAllPagesQuestion": "Are you sure you want to delete all pages? This will result in the deletion of the attachment."
+                "deleteAllPagesQuestion": "Are you sure you want to delete all pages? This will result in the deletion of the attachment.",
+                "hiddenAttachmentUnitCreateSuccess": "Attachment unit with hidden pages created successfully.",
+                "hiddenAttachmentUnitCreateError": "Failed to create attachment unit with hidden pages: {{error}}",
+                "hiddenAttachmentUnitUpdateSuccess": "Attachment unit with hidden pages updated successfully.",
+                "hiddenAttachmentUnitUpdateError": "Failed to update attachment unit with hidden pages: {{error}}"
             }
         }
     }

From e73a9407ed40096a9e6783fd55ac0449b9590cae Mon Sep 17 00:00:00 2001
From: Ece Eren <aybikeceren@gmail.com>
Date: Sun, 17 Nov 2024 19:24:22 +0100
Subject: [PATCH 07/11] Remove changes from Attachment Unit and add it to the
 Attachment

---
 .../artemis/lecture/domain/Attachment.java    |  4 +++
 .../lecture/domain/AttachmentUnit.java        | 26 ----------------
 .../repository/AttachmentRepository.java      |  7 +++++
 .../repository/AttachmentUnitRepository.java  |  8 -----
 .../service/AttachmentUnitService.java        |  5 +--
 .../service/LectureUnitProcessingService.java |  2 +-
 .../lecture/web/AttachmentResource.java       | 13 ++++++++
 .../lecture/web/AttachmentUnitResource.java   | 31 +++++--------------
 .../changelog/20241112002519_changelog.xml    | 22 -------------
 .../resources/config/liquibase/master.xml     |  2 +-
 .../lecture-unit/attachmentUnit.model.ts      |  2 --
 .../attachment-unit-form.component.ts         |  1 -
 .../create-attachment-unit.component.ts       |  3 +-
 .../pdf-preview/pdf-preview.component.ts      |  4 ---
 14 files changed, 35 insertions(+), 95 deletions(-)
 delete mode 100644 src/main/resources/config/liquibase/changelog/20241112002519_changelog.xml

diff --git a/src/main/java/de/tum/cit/aet/artemis/lecture/domain/Attachment.java b/src/main/java/de/tum/cit/aet/artemis/lecture/domain/Attachment.java
index 6806850fd86b..3b6c8ae2092b 100644
--- a/src/main/java/de/tum/cit/aet/artemis/lecture/domain/Attachment.java
+++ b/src/main/java/de/tum/cit/aet/artemis/lecture/domain/Attachment.java
@@ -61,6 +61,10 @@ public class Attachment extends DomainObject implements Serializable {
     @JoinColumn(name = "attachment_unit_id")
     private AttachmentUnit attachmentUnit;
 
+    @OneToOne
+    @JoinColumn(name = "parent_attachment_id")
+    private Attachment parentAttachment;
+
     // jhipster-needle-entity-add-field - JHipster will add fields here, do not remove
 
     public String getName() {
diff --git a/src/main/java/de/tum/cit/aet/artemis/lecture/domain/AttachmentUnit.java b/src/main/java/de/tum/cit/aet/artemis/lecture/domain/AttachmentUnit.java
index 1107327567ae..1af955b43d89 100644
--- a/src/main/java/de/tum/cit/aet/artemis/lecture/domain/AttachmentUnit.java
+++ b/src/main/java/de/tum/cit/aet/artemis/lecture/domain/AttachmentUnit.java
@@ -9,11 +9,9 @@
 import jakarta.persistence.DiscriminatorValue;
 import jakarta.persistence.Entity;
 import jakarta.persistence.FetchType;
-import jakarta.persistence.JoinColumn;
 import jakarta.persistence.OneToMany;
 import jakarta.persistence.OneToOne;
 
-import com.fasterxml.jackson.annotation.JsonIgnore;
 import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
 import com.fasterxml.jackson.annotation.JsonInclude;
 
@@ -34,14 +32,6 @@ public class AttachmentUnit extends LectureUnit {
     @JsonIgnoreProperties("attachmentUnit")
     private List<Slide> slides = new ArrayList<>();
 
-    @Column(name = "hidden_pages")
-    private String hiddenPages;
-
-    @OneToOne
-    @JoinColumn(name = "parent_attachment_unit_id")
-    @JsonIgnore
-    private AttachmentUnit parentAttachmentUnit;
-
     @Override
     public boolean isVisibleToStudents() {
         if (attachment == null) {
@@ -101,20 +91,4 @@ public void setReleaseDate(ZonedDateTime releaseDate) {
     public String getType() {
         return "attachment";
     }
-
-    public String getHiddenPages() {
-        return hiddenPages;
-    }
-
-    public void setHiddenPages(String hiddenPages) {
-        this.hiddenPages = hiddenPages;
-    }
-
-    public AttachmentUnit getParentAttachmentUnit() {
-        return parentAttachmentUnit;
-    }
-
-    public void setParentAttachmentUnit(AttachmentUnit parentAttachmentUnit) {
-        this.parentAttachmentUnit = parentAttachmentUnit;
-    }
 }
diff --git a/src/main/java/de/tum/cit/aet/artemis/lecture/repository/AttachmentRepository.java b/src/main/java/de/tum/cit/aet/artemis/lecture/repository/AttachmentRepository.java
index 30b1068ed687..dfe3d1f675c1 100644
--- a/src/main/java/de/tum/cit/aet/artemis/lecture/repository/AttachmentRepository.java
+++ b/src/main/java/de/tum/cit/aet/artemis/lecture/repository/AttachmentRepository.java
@@ -29,4 +29,11 @@ public interface AttachmentRepository extends ArtemisJpaRepository<Attachment, L
     default Attachment findByIdOrElseThrow(Long attachmentId) {
         return getValueElseThrow(findById(attachmentId), attachmentId);
     }
+
+    @Query("""
+            SELECT attachment
+            FROM Attachment attachment
+            WHERE attachment.parentAttachment.id = :parentAttachmentId
+            """)
+    Attachment findAttachmentByParentAttachmentId(@Param("parentAttachmentId") Long parentAttachmentId);
 }
diff --git a/src/main/java/de/tum/cit/aet/artemis/lecture/repository/AttachmentUnitRepository.java b/src/main/java/de/tum/cit/aet/artemis/lecture/repository/AttachmentUnitRepository.java
index 2a4774fa6e87..61f268d75b95 100644
--- a/src/main/java/de/tum/cit/aet/artemis/lecture/repository/AttachmentUnitRepository.java
+++ b/src/main/java/de/tum/cit/aet/artemis/lecture/repository/AttachmentUnitRepository.java
@@ -63,12 +63,4 @@ default List<AttachmentUnit> findAllByLectureIdAndAttachmentTypeElseThrow(Long l
             WHERE attachmentUnit.id = :attachmentUnitId
             """)
     AttachmentUnit findOneWithSlidesAndCompetencies(@Param("attachmentUnitId") long attachmentUnitId);
-
-    @Query("""
-            SELECT attachmentUnit
-            FROM AttachmentUnit attachmentUnit
-            WHERE attachmentUnit.lecture.id = :lectureId
-                 AND attachmentUnit.parentAttachmentUnit.id = :parentAttachmentUnitId
-            """)
-    AttachmentUnit findAttachmentUnitByLectureIdAndParentAttachmentUnitId(@Param("lectureId") Long lectureId, @Param("parentAttachmentUnitId") Long parentAttachmentUnitId);
 }
diff --git a/src/main/java/de/tum/cit/aet/artemis/lecture/service/AttachmentUnitService.java b/src/main/java/de/tum/cit/aet/artemis/lecture/service/AttachmentUnitService.java
index 7ca722fb2b49..e86d7c22e7f5 100644
--- a/src/main/java/de/tum/cit/aet/artemis/lecture/service/AttachmentUnitService.java
+++ b/src/main/java/de/tum/cit/aet/artemis/lecture/service/AttachmentUnitService.java
@@ -77,14 +77,12 @@ public AttachmentUnitService(SlideRepository slideRepository, SlideSplitterServi
      * @param keepFilename   Whether to keep the original filename or not.
      * @return The created attachment unit
      */
-    public AttachmentUnit createAttachmentUnit(AttachmentUnit attachmentUnit, Attachment attachment, Lecture lecture, AttachmentUnit parentAttachmentUnit, MultipartFile file,
-            boolean keepFilename) {
+    public AttachmentUnit createAttachmentUnit(AttachmentUnit attachmentUnit, Attachment attachment, Lecture lecture, MultipartFile file, boolean keepFilename) {
         // persist lecture unit before lecture to prevent "null index column for collection" error
         attachmentUnit.setLecture(null);
 
         AttachmentUnit savedAttachmentUnit = lectureUnitService.saveWithCompetencyLinks(attachmentUnit, attachmentUnitRepository::saveAndFlush);
 
-        savedAttachmentUnit.setParentAttachmentUnit(parentAttachmentUnit);
         attachmentUnit.setLecture(lecture);
         lecture.addLectureUnit(savedAttachmentUnit);
 
@@ -119,7 +117,6 @@ public AttachmentUnit updateAttachmentUnit(AttachmentUnit existingAttachmentUnit
         existingAttachmentUnit.setDescription(updateUnit.getDescription());
         existingAttachmentUnit.setName(updateUnit.getName());
         existingAttachmentUnit.setReleaseDate(updateUnit.getReleaseDate());
-        existingAttachmentUnit.setHiddenPages(updateUnit.getHiddenPages());
 
         AttachmentUnit savedAttachmentUnit = lectureUnitService.saveWithCompetencyLinks(existingAttachmentUnit, attachmentUnitRepository::saveAndFlush);
 
diff --git a/src/main/java/de/tum/cit/aet/artemis/lecture/service/LectureUnitProcessingService.java b/src/main/java/de/tum/cit/aet/artemis/lecture/service/LectureUnitProcessingService.java
index 1a770071b687..602106099847 100644
--- a/src/main/java/de/tum/cit/aet/artemis/lecture/service/LectureUnitProcessingService.java
+++ b/src/main/java/de/tum/cit/aet/artemis/lecture/service/LectureUnitProcessingService.java
@@ -108,7 +108,7 @@ public List<AttachmentUnit> splitAndSaveUnits(LectureUnitSplitInformationDTO lec
                 attachment.setUploadDate(ZonedDateTime.now());
 
                 MultipartFile multipartFile = fileService.convertByteArrayToMultipart(lectureUnit.unitName(), ".pdf", outputStream.toByteArray());
-                AttachmentUnit savedAttachmentUnit = attachmentUnitService.createAttachmentUnit(attachmentUnit, attachment, lecture, null, multipartFile, true);
+                AttachmentUnit savedAttachmentUnit = attachmentUnitService.createAttachmentUnit(attachmentUnit, attachment, lecture, multipartFile, true);
                 slideSplitterService.splitAttachmentUnitIntoSingleSlides(documentUnits.getFirst(), savedAttachmentUnit, multipartFile.getOriginalFilename());
                 documentUnits.getFirst().close(); // make sure to close the document
                 units.add(savedAttachmentUnit);
diff --git a/src/main/java/de/tum/cit/aet/artemis/lecture/web/AttachmentResource.java b/src/main/java/de/tum/cit/aet/artemis/lecture/web/AttachmentResource.java
index 6c280a0ce0be..609495721f5d 100644
--- a/src/main/java/de/tum/cit/aet/artemis/lecture/web/AttachmentResource.java
+++ b/src/main/java/de/tum/cit/aet/artemis/lecture/web/AttachmentResource.java
@@ -210,4 +210,17 @@ else if (attachment.getExercise() != null) {
         }
         return ResponseEntity.ok().headers(HeaderUtil.createEntityDeletionAlert(applicationName, true, ENTITY_NAME, attachmentId.toString())).build();
     }
+
+    /**
+     * GET /attachments/:attachmentId/hiddenAttachment : retrieve the hidden attachment associated with the given parent attachment ID.
+     *
+     * @param parentAttachmentId the ID of the parent attachment for which to retrieve the hidden attachment
+     * @return the ResponseEntity with status 200 (OK) and the AttachmentUnit in the body, or a 404 (Not Found) if no matching attachment unit exists
+     */
+    @GetMapping("attachments/{parentAttachmentId}/hiddenAttachment")
+    @EnforceAtLeastTutor
+    public ResponseEntity<Attachment> getAttachmentByParentAttachmentId(@PathVariable Long parentAttachmentId) {
+        log.debug("REST request to get attachment by the parent attachment Id : {}", parentAttachmentId);
+        return ResponseEntity.ok(attachmentRepository.findAttachmentByParentAttachmentId(parentAttachmentId));
+    }
 }
diff --git a/src/main/java/de/tum/cit/aet/artemis/lecture/web/AttachmentUnitResource.java b/src/main/java/de/tum/cit/aet/artemis/lecture/web/AttachmentUnitResource.java
index 9a504b83020a..0c7c2996e162 100644
--- a/src/main/java/de/tum/cit/aet/artemis/lecture/web/AttachmentUnitResource.java
+++ b/src/main/java/de/tum/cit/aet/artemis/lecture/web/AttachmentUnitResource.java
@@ -36,7 +36,6 @@
 import de.tum.cit.aet.artemis.core.exception.InternalServerErrorException;
 import de.tum.cit.aet.artemis.core.security.Role;
 import de.tum.cit.aet.artemis.core.security.annotations.EnforceAtLeastEditor;
-import de.tum.cit.aet.artemis.core.security.annotations.EnforceAtLeastTutor;
 import de.tum.cit.aet.artemis.core.service.AuthorizationCheckService;
 import de.tum.cit.aet.artemis.core.service.FileService;
 import de.tum.cit.aet.artemis.lecture.domain.Attachment;
@@ -142,20 +141,18 @@ public ResponseEntity<AttachmentUnit> updateAttachmentUnit(@PathVariable Long le
     /**
      * POST lectures/:lectureId/attachment-units : creates a new attachment unit.
      *
-     * @param lectureId            the id of the lecture to which the attachment unit should be added
-     * @param attachmentUnit       the attachment unit that should be created
-     * @param attachment           the attachment that should be created
-     * @param parentAttachmentUnit the parent attachment unit of the new attachment unit
-     * @param file                 the file to upload
-     * @param keepFilename         specifies if the original filename should be kept or not
+     * @param lectureId      the id of the lecture to which the attachment unit should be added
+     * @param attachmentUnit the attachment unit that should be created
+     * @param attachment     the attachment that should be created
+     * @param file           the file to upload
+     * @param keepFilename   specifies if the original filename should be kept or not
      * @return the ResponseEntity with status 201 (Created) and with body the new attachment unit
      * @throws URISyntaxException if the Location URI syntax is incorrect
      */
     @PostMapping(value = "lectures/{lectureId}/attachment-units", consumes = MediaType.MULTIPART_FORM_DATA_VALUE)
     @EnforceAtLeastEditor
     public ResponseEntity<AttachmentUnit> createAttachmentUnit(@PathVariable Long lectureId, @RequestPart AttachmentUnit attachmentUnit, @RequestPart Attachment attachment,
-            @RequestPart AttachmentUnit parentAttachmentUnit, @RequestPart MultipartFile file, @RequestParam(defaultValue = "false") boolean keepFilename)
-            throws URISyntaxException {
+            @RequestPart MultipartFile file, @RequestParam(defaultValue = "false") boolean keepFilename) throws URISyntaxException {
         log.debug("REST request to create AttachmentUnit {} with Attachment {}", attachmentUnit, attachment);
         if (attachmentUnit.getId() != null) {
             throw new BadRequestAlertException("A new attachment unit cannot already have an ID", ENTITY_NAME, "idexists");
@@ -170,7 +167,7 @@ public ResponseEntity<AttachmentUnit> createAttachmentUnit(@PathVariable Long le
         }
         authorizationCheckService.checkHasAtLeastRoleInCourseElseThrow(Role.EDITOR, lecture.getCourse(), null);
 
-        AttachmentUnit savedAttachmentUnit = attachmentUnitService.createAttachmentUnit(attachmentUnit, attachment, lecture, parentAttachmentUnit, file, keepFilename);
+        AttachmentUnit savedAttachmentUnit = attachmentUnitService.createAttachmentUnit(attachmentUnit, attachment, lecture, file, keepFilename);
         lectureRepository.save(lecture);
         if (Objects.equals(FilenameUtils.getExtension(file.getOriginalFilename()), "pdf")) {
             slideSplitterService.splitAttachmentUnitIntoSingleSlides(savedAttachmentUnit);
@@ -335,18 +332,4 @@ private void checkFile(Path filePath) {
             throw new BadRequestAlertException("The file must be a pdf", ENTITY_NAME, "wrongFileType");
         }
     }
-
-    /**
-     * GET /lectures/:lectureId/attachment-units/:parentAttachmentUnitId/hiddenAttachment : retrieve the hidden attachment unit associated with the given parent attachment unit ID.
-     *
-     * @param lectureId              the ID of the lecture to which the attachment unit belongs
-     * @param parentAttachmentUnitId the ID of the parent attachment unit for which to retrieve the hidden attachment unit
-     * @return the ResponseEntity with status 200 (OK) and the AttachmentUnit in the body, or a 404 (Not Found) if no matching attachment unit exists
-     */
-    @GetMapping("lectures/{lectureId}/attachment-units/{parentAttachmentUnitId}/hiddenAttachment")
-    @EnforceAtLeastTutor
-    public ResponseEntity<AttachmentUnit> getAttachmentUnitByParentAttachmentUnitId(@PathVariable Long lectureId, @PathVariable Long parentAttachmentUnitId) {
-        log.debug("REST request to get attachment unit by the parent attachment unit Id : {}", parentAttachmentUnitId);
-        return ResponseEntity.ok(attachmentUnitRepository.findAttachmentUnitByLectureIdAndParentAttachmentUnitId(lectureId, parentAttachmentUnitId));
-    }
 }
diff --git a/src/main/resources/config/liquibase/changelog/20241112002519_changelog.xml b/src/main/resources/config/liquibase/changelog/20241112002519_changelog.xml
deleted file mode 100644
index 8157408b9c6e..000000000000
--- a/src/main/resources/config/liquibase/changelog/20241112002519_changelog.xml
+++ /dev/null
@@ -1,22 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<databaseChangeLog xmlns="http://www.liquibase.org/xml/ns/dbchangelog"
-                   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-                   xsi:schemaLocation="http://www.liquibase.org/xml/ns/dbchangelog https://www.liquibase.org/xml/ns/dbchangelog/dbchangelog-latest.xsd">
-    <changeSet id="20241112002519" author="ece.eren">
-        <addColumn tableName="lecture_unit">
-            <column name="hidden_pages" type="VARCHAR(255)"/>
-        </addColumn>
-
-        <addColumn tableName="lecture_unit">
-            <column name="parent_attachment_unit_id" type="BIGINT"/>
-        </addColumn>
-
-        <addForeignKeyConstraint
-                baseTableName="lecture_unit"
-                baseColumnNames="parent_attachment_unit_id"
-                referencedTableName="lecture_unit"
-                referencedColumnNames="id"
-                constraintName="fk_attachment_unit_parent_attachment_unit_id"
-                onDelete="CASCADE"/>
-    </changeSet>
-</databaseChangeLog>
diff --git a/src/main/resources/config/liquibase/master.xml b/src/main/resources/config/liquibase/master.xml
index 5b8d5ea88e86..51e4fe5294ea 100644
--- a/src/main/resources/config/liquibase/master.xml
+++ b/src/main/resources/config/liquibase/master.xml
@@ -33,7 +33,7 @@
     <include file="classpath:config/liquibase/changelog/20241010101010_changelog.xml" relativeToChangelogFile="false"/>
     <include file="classpath:config/liquibase/changelog/20241018053210_changelog.xml" relativeToChangelogFile="false"/>
     <include file="classpath:config/liquibase/changelog/20241023456789_changelog.xml" relativeToChangelogFile="false"/>
-    <include file="classpath:config/liquibase/changelog/20241112002519_changelog.xml" relativeToChangelogFile="false"/>
+    <include file="classpath:config/liquibase/changelog/20241117192154_changelog.xml" relativeToChangelogFile="false"/>
 
     <!-- NOTE: please use the format "YYYYMMDDhhmmss_changelog.xml", i.e. year month day hour minutes seconds and not something else! -->
     <!-- we should also stay in a chronological order! -->
diff --git a/src/main/webapp/app/entities/lecture-unit/attachmentUnit.model.ts b/src/main/webapp/app/entities/lecture-unit/attachmentUnit.model.ts
index 0baa633022fa..9d1e9986329e 100644
--- a/src/main/webapp/app/entities/lecture-unit/attachmentUnit.model.ts
+++ b/src/main/webapp/app/entities/lecture-unit/attachmentUnit.model.ts
@@ -6,8 +6,6 @@ export class AttachmentUnit extends LectureUnit {
     public description?: string;
     public attachment?: Attachment;
     public slides?: Slide[];
-    public hiddenPages?: string;
-    public parentAttachmentUnit?: AttachmentUnit;
 
     constructor() {
         super(LectureUnitType.ATTACHMENT);
diff --git a/src/main/webapp/app/lecture/lecture-unit/lecture-unit-management/attachment-unit-form/attachment-unit-form.component.ts b/src/main/webapp/app/lecture/lecture-unit/lecture-unit-management/attachment-unit-form/attachment-unit-form.component.ts
index e0bea9c512bc..6ed702b59547 100644
--- a/src/main/webapp/app/lecture/lecture-unit/lecture-unit-management/attachment-unit-form/attachment-unit-form.component.ts
+++ b/src/main/webapp/app/lecture/lecture-unit/lecture-unit-management/attachment-unit-form/attachment-unit-form.component.ts
@@ -20,7 +20,6 @@ export interface FormProperties {
     version?: number;
     updateNotificationText?: string;
     competencyLinks?: CompetencyLectureUnitLink[];
-    hiddenPages?: string;
 }
 
 // file input is a special case and is not included in the reactive form structure
diff --git a/src/main/webapp/app/lecture/lecture-unit/lecture-unit-management/create-attachment-unit/create-attachment-unit.component.ts b/src/main/webapp/app/lecture/lecture-unit/lecture-unit-management/create-attachment-unit/create-attachment-unit.component.ts
index adaa070f4d89..55a07861bac9 100644
--- a/src/main/webapp/app/lecture/lecture-unit/lecture-unit-management/create-attachment-unit/create-attachment-unit.component.ts
+++ b/src/main/webapp/app/lecture/lecture-unit/lecture-unit-management/create-attachment-unit/create-attachment-unit.component.ts
@@ -47,7 +47,7 @@ export class CreateAttachmentUnitComponent implements OnInit {
         if (!attachmentUnitFormData?.formProperties?.name || !attachmentUnitFormData?.fileProperties?.file || !attachmentUnitFormData?.fileProperties?.fileName) {
             return;
         }
-        const { description, name, releaseDate, competencyLinks, hiddenPages } = attachmentUnitFormData.formProperties;
+        const { description, name, releaseDate, competencyLinks } = attachmentUnitFormData.formProperties;
         const { file, fileName } = attachmentUnitFormData.fileProperties;
 
         // === Setting attachment ===
@@ -60,7 +60,6 @@ export class CreateAttachmentUnitComponent implements OnInit {
         // === Setting attachmentUnit ===
         this.attachmentUnitToCreate.description = description;
         this.attachmentUnitToCreate.competencyLinks = competencyLinks || [];
-        this.attachmentUnitToCreate.hiddenPages = hiddenPages;
 
         this.isLoading = true;
 
diff --git a/src/main/webapp/app/lecture/pdf-preview/pdf-preview.component.ts b/src/main/webapp/app/lecture/pdf-preview/pdf-preview.component.ts
index f0a4a0b1b342..ec5e7f96945c 100644
--- a/src/main/webapp/app/lecture/pdf-preview/pdf-preview.component.ts
+++ b/src/main/webapp/app/lecture/pdf-preview/pdf-preview.component.ts
@@ -163,7 +163,6 @@ export class PdfPreviewComponent implements OnInit, OnDestroy {
             this.attachmentToBeEdited.set(this.attachmentUnit()!.attachment!);
             this.attachmentToBeEdited()!.version!++;
             this.attachmentToBeEdited()!.uploadDate = dayjs();
-            this.attachmentUnit()!.hiddenPages = finalHiddenPages;
 
             const formData = new FormData();
             formData.append('file', pdfFile);
@@ -180,15 +179,12 @@ export class PdfPreviewComponent implements OnInit, OnDestroy {
                         attachmentWithHiddenPages.id = undefined;
                         attachmentWithHiddenPages.name = `${attachmentWithHiddenPages.name}_hidden`;
                         attachmentUnitWithHiddenPages.id = undefined;
-                        attachmentUnitWithHiddenPages.hiddenPages = undefined;
-                        //attachmentUnitWithHiddenPages.parentAttachmentUnit = this.attachmentUnit();
 
                         const formData = new FormData();
 
                         formData.append('file', pdfFileWithHiddenPages!);
                         formData.append('attachment', objectToJsonBlob(attachmentWithHiddenPages!));
                         formData.append('attachmentUnit', objectToJsonBlob(attachmentUnitWithHiddenPages!));
-                        formData.append('parentAttachmentUnit', objectToJsonBlob(this.attachmentUnit()!));
 
                         this.attachmentUnitService.getAttachmentUnitByParentAttachmentUnitId(this.attachmentUnit()!.lecture!.id!, this.attachmentUnit()!.id!).subscribe({
                             next: async (attachmentUnitRes) => {

From 3696f8cedc2505c99d58fe49dc66d99ec731a257 Mon Sep 17 00:00:00 2001
From: Ece Eren <aybikeceren@gmail.com>
Date: Mon, 18 Nov 2024 01:19:39 +0100
Subject: [PATCH 08/11] Add Slide table hidden page column setting

---
 .../artemis/lecture/domain/Attachment.java    |  4 --
 .../cit/aet/artemis/lecture/domain/Slide.java | 13 ++++
 .../repository/AttachmentRepository.java      |  7 ---
 .../lecture/service/SlideSplitterService.java | 32 +++++++---
 .../lecture/web/AttachmentResource.java       | 13 ----
 .../lecture/web/AttachmentUnitResource.java   |  8 ++-
 .../changelog/20241117234100_changelog.xml    | 10 ++++
 .../resources/config/liquibase/master.xml     |  2 +-
 .../attachmentUnit.service.ts                 | 18 +-----
 .../pdf-preview/pdf-preview.component.ts      | 60 ++-----------------
 10 files changed, 61 insertions(+), 106 deletions(-)
 create mode 100644 src/main/resources/config/liquibase/changelog/20241117234100_changelog.xml

diff --git a/src/main/java/de/tum/cit/aet/artemis/lecture/domain/Attachment.java b/src/main/java/de/tum/cit/aet/artemis/lecture/domain/Attachment.java
index 3b6c8ae2092b..6806850fd86b 100644
--- a/src/main/java/de/tum/cit/aet/artemis/lecture/domain/Attachment.java
+++ b/src/main/java/de/tum/cit/aet/artemis/lecture/domain/Attachment.java
@@ -61,10 +61,6 @@ public class Attachment extends DomainObject implements Serializable {
     @JoinColumn(name = "attachment_unit_id")
     private AttachmentUnit attachmentUnit;
 
-    @OneToOne
-    @JoinColumn(name = "parent_attachment_id")
-    private Attachment parentAttachment;
-
     // jhipster-needle-entity-add-field - JHipster will add fields here, do not remove
 
     public String getName() {
diff --git a/src/main/java/de/tum/cit/aet/artemis/lecture/domain/Slide.java b/src/main/java/de/tum/cit/aet/artemis/lecture/domain/Slide.java
index 1eb21299bc15..b89be6e2e39c 100644
--- a/src/main/java/de/tum/cit/aet/artemis/lecture/domain/Slide.java
+++ b/src/main/java/de/tum/cit/aet/artemis/lecture/domain/Slide.java
@@ -1,5 +1,7 @@
 package de.tum.cit.aet.artemis.lecture.domain;
 
+import java.util.Date;
+
 import jakarta.persistence.Column;
 import jakarta.persistence.Entity;
 import jakarta.persistence.JoinColumn;
@@ -27,6 +29,9 @@ public class Slide extends DomainObject {
     @Column(name = "slide_number")
     private int slideNumber;
 
+    @Column(name = "hidden")
+    private Date hidden;
+
     public AttachmentUnit getAttachmentUnit() {
         return attachmentUnit;
     }
@@ -50,4 +55,12 @@ public int getSlideNumber() {
     public void setSlideNumber(int slideNumber) {
         this.slideNumber = slideNumber;
     }
+
+    public Date getHidden() {
+        return hidden;
+    }
+
+    public void setHidden(Date hidden) {
+        this.hidden = hidden;
+    }
 }
diff --git a/src/main/java/de/tum/cit/aet/artemis/lecture/repository/AttachmentRepository.java b/src/main/java/de/tum/cit/aet/artemis/lecture/repository/AttachmentRepository.java
index dfe3d1f675c1..30b1068ed687 100644
--- a/src/main/java/de/tum/cit/aet/artemis/lecture/repository/AttachmentRepository.java
+++ b/src/main/java/de/tum/cit/aet/artemis/lecture/repository/AttachmentRepository.java
@@ -29,11 +29,4 @@ public interface AttachmentRepository extends ArtemisJpaRepository<Attachment, L
     default Attachment findByIdOrElseThrow(Long attachmentId) {
         return getValueElseThrow(findById(attachmentId), attachmentId);
     }
-
-    @Query("""
-            SELECT attachment
-            FROM Attachment attachment
-            WHERE attachment.parentAttachment.id = :parentAttachmentId
-            """)
-    Attachment findAttachmentByParentAttachmentId(@Param("parentAttachmentId") Long parentAttachmentId);
 }
diff --git a/src/main/java/de/tum/cit/aet/artemis/lecture/service/SlideSplitterService.java b/src/main/java/de/tum/cit/aet/artemis/lecture/service/SlideSplitterService.java
index 2801cab5c02f..212c565055c1 100644
--- a/src/main/java/de/tum/cit/aet/artemis/lecture/service/SlideSplitterService.java
+++ b/src/main/java/de/tum/cit/aet/artemis/lecture/service/SlideSplitterService.java
@@ -8,6 +8,11 @@
 import java.io.IOException;
 import java.net.URI;
 import java.nio.file.Path;
+import java.time.LocalDate;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+import java.util.Optional;
 
 import javax.imageio.ImageIO;
 
@@ -39,6 +44,8 @@ public class SlideSplitterService {
 
     private static final Logger log = LoggerFactory.getLogger(SlideSplitterService.class);
 
+    static final LocalDate FOREVER = LocalDate.of(9999, 12, 31);
+
     private final FileService fileService;
 
     private final SlideRepository slideRepository;
@@ -54,12 +61,12 @@ public SlideSplitterService(FileService fileService, SlideRepository slideReposi
      * @param attachmentUnit The attachment unit to which the slides belong.
      */
     @Async
-    public void splitAttachmentUnitIntoSingleSlides(AttachmentUnit attachmentUnit) {
+    public void splitAttachmentUnitIntoSingleSlides(AttachmentUnit attachmentUnit, String hiddenPages) {
         Path attachmentPath = FilePathService.actualPathForPublicPath(URI.create(attachmentUnit.getAttachment().getLink()));
         File file = attachmentPath.toFile();
         try (PDDocument document = Loader.loadPDF(file)) {
             String pdfFilename = file.getName();
-            splitAttachmentUnitIntoSingleSlides(document, attachmentUnit, pdfFilename);
+            splitAttachmentUnitIntoSingleSlides(document, attachmentUnit, pdfFilename, hiddenPages);
         }
         catch (IOException e) {
             log.error("Error while splitting Attachment Unit {} into single slides", attachmentUnit.getId(), e);
@@ -68,19 +75,22 @@ public void splitAttachmentUnitIntoSingleSlides(AttachmentUnit attachmentUnit) {
     }
 
     /**
-     * Splits an Attachment Unit file into single slides and saves them as PNG files. Document is closed where this method is called.
+     * Splits an Attachment Unit file into single slides and saves them as PNG files or updates existing slides.
      *
      * @param attachmentUnit The attachment unit to which the slides belong.
      * @param document       The PDF document that is already loaded.
      * @param pdfFilename    The name of the PDF file.
      */
-    public void splitAttachmentUnitIntoSingleSlides(PDDocument document, AttachmentUnit attachmentUnit, String pdfFilename) {
+    public void splitAttachmentUnitIntoSingleSlides(PDDocument document, AttachmentUnit attachmentUnit, String pdfFilename, String hiddenPages) {
         log.debug("Splitting Attachment Unit file {} into single slides", attachmentUnit.getAttachment().getName());
         try {
             String fileNameWithOutExt = FilenameUtils.removeExtension(pdfFilename);
             int numPages = document.getNumberOfPages();
             PDFRenderer pdfRenderer = new PDFRenderer(document);
 
+            List<Integer> hiddenPagesList = hiddenPages != null && !hiddenPages.isEmpty() ? Arrays.stream(hiddenPages.split(",")).map(Integer::parseInt).toList()
+                    : Collections.emptyList();
+
             for (int page = 0; page < numPages; page++) {
                 BufferedImage bufferedImage = pdfRenderer.renderImageWithDPI(page, 72, ImageType.RGB);
                 byte[] imageInByte = bufferedImageToByteArray(bufferedImage, "png");
@@ -89,11 +99,15 @@ public void splitAttachmentUnitIntoSingleSlides(PDDocument document, AttachmentU
                 MultipartFile slideFile = fileService.convertByteArrayToMultipart(filename, ".png", imageInByte);
                 Path savePath = fileService.saveFile(slideFile, FilePathService.getAttachmentUnitFilePath().resolve(attachmentUnit.getId().toString()).resolve("slide")
                         .resolve(String.valueOf(slideNumber)).resolve(filename));
-                Slide slideEntity = new Slide();
-                slideEntity.setSlideImagePath(FilePathService.publicPathForActualPath(savePath, (long) slideNumber).toString());
-                slideEntity.setSlideNumber(slideNumber);
-                slideEntity.setAttachmentUnit(attachmentUnit);
-                slideRepository.save(slideEntity);
+
+                Optional<Slide> existingSlideOpt = Optional.ofNullable(slideRepository.findSlideByAttachmentUnitIdAndSlideNumber(attachmentUnit.getId(), slideNumber));
+                Slide slide = existingSlideOpt.orElseGet(Slide::new);
+                slide.setSlideImagePath(FilePathService.publicPathForActualPath(savePath, (long) slideNumber).toString());
+                slide.setSlideNumber(slideNumber);
+                slide.setAttachmentUnit(attachmentUnit);
+                slide.setHidden(hiddenPagesList.contains(slide.getSlideNumber()) ? java.sql.Date.valueOf(FOREVER) : null);
+                slideRepository.save(slide);
+
             }
         }
         catch (IOException e) {
diff --git a/src/main/java/de/tum/cit/aet/artemis/lecture/web/AttachmentResource.java b/src/main/java/de/tum/cit/aet/artemis/lecture/web/AttachmentResource.java
index 609495721f5d..6c280a0ce0be 100644
--- a/src/main/java/de/tum/cit/aet/artemis/lecture/web/AttachmentResource.java
+++ b/src/main/java/de/tum/cit/aet/artemis/lecture/web/AttachmentResource.java
@@ -210,17 +210,4 @@ else if (attachment.getExercise() != null) {
         }
         return ResponseEntity.ok().headers(HeaderUtil.createEntityDeletionAlert(applicationName, true, ENTITY_NAME, attachmentId.toString())).build();
     }
-
-    /**
-     * GET /attachments/:attachmentId/hiddenAttachment : retrieve the hidden attachment associated with the given parent attachment ID.
-     *
-     * @param parentAttachmentId the ID of the parent attachment for which to retrieve the hidden attachment
-     * @return the ResponseEntity with status 200 (OK) and the AttachmentUnit in the body, or a 404 (Not Found) if no matching attachment unit exists
-     */
-    @GetMapping("attachments/{parentAttachmentId}/hiddenAttachment")
-    @EnforceAtLeastTutor
-    public ResponseEntity<Attachment> getAttachmentByParentAttachmentId(@PathVariable Long parentAttachmentId) {
-        log.debug("REST request to get attachment by the parent attachment Id : {}", parentAttachmentId);
-        return ResponseEntity.ok(attachmentRepository.findAttachmentByParentAttachmentId(parentAttachmentId));
-    }
 }
diff --git a/src/main/java/de/tum/cit/aet/artemis/lecture/web/AttachmentUnitResource.java b/src/main/java/de/tum/cit/aet/artemis/lecture/web/AttachmentUnitResource.java
index 0c7c2996e162..4ec38db09a74 100644
--- a/src/main/java/de/tum/cit/aet/artemis/lecture/web/AttachmentUnitResource.java
+++ b/src/main/java/de/tum/cit/aet/artemis/lecture/web/AttachmentUnitResource.java
@@ -123,7 +123,7 @@ public ResponseEntity<AttachmentUnit> getAttachmentUnit(@PathVariable Long attac
     @EnforceAtLeastEditor
     public ResponseEntity<AttachmentUnit> updateAttachmentUnit(@PathVariable Long lectureId, @PathVariable Long attachmentUnitId, @RequestPart AttachmentUnit attachmentUnit,
             @RequestPart Attachment attachment, @RequestPart(required = false) MultipartFile file, @RequestParam(defaultValue = "false") boolean keepFilename,
-            @RequestParam(value = "notificationText", required = false) String notificationText) {
+            @RequestParam(value = "notificationText", required = false) String notificationText, @RequestParam(value = "hiddenPages", required = false) String hiddenPages) {
         log.debug("REST request to update an attachment unit : {}", attachmentUnit);
         AttachmentUnit existingAttachmentUnit = attachmentUnitRepository.findOneWithSlidesAndCompetencies(attachmentUnitId);
         checkAttachmentUnitCourseAndLecture(existingAttachmentUnit, lectureId);
@@ -135,6 +135,10 @@ public ResponseEntity<AttachmentUnit> updateAttachmentUnit(@PathVariable Long le
             groupNotificationService.notifyStudentGroupAboutAttachmentChange(savedAttachmentUnit.getAttachment(), notificationText);
         }
 
+        if (Objects.equals(FilenameUtils.getExtension(file.getOriginalFilename()), "pdf")) {
+            slideSplitterService.splitAttachmentUnitIntoSingleSlides(savedAttachmentUnit, hiddenPages);
+        }
+
         return ResponseEntity.ok(savedAttachmentUnit);
     }
 
@@ -170,7 +174,7 @@ public ResponseEntity<AttachmentUnit> createAttachmentUnit(@PathVariable Long le
         AttachmentUnit savedAttachmentUnit = attachmentUnitService.createAttachmentUnit(attachmentUnit, attachment, lecture, file, keepFilename);
         lectureRepository.save(lecture);
         if (Objects.equals(FilenameUtils.getExtension(file.getOriginalFilename()), "pdf")) {
-            slideSplitterService.splitAttachmentUnitIntoSingleSlides(savedAttachmentUnit);
+            slideSplitterService.splitAttachmentUnitIntoSingleSlides(savedAttachmentUnit, null);
         }
         attachmentUnitService.prepareAttachmentUnitForClient(savedAttachmentUnit);
         competencyProgressService.updateProgressByLearningObjectAsync(savedAttachmentUnit);
diff --git a/src/main/resources/config/liquibase/changelog/20241117234100_changelog.xml b/src/main/resources/config/liquibase/changelog/20241117234100_changelog.xml
new file mode 100644
index 000000000000..b6588d31153a
--- /dev/null
+++ b/src/main/resources/config/liquibase/changelog/20241117234100_changelog.xml
@@ -0,0 +1,10 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<databaseChangeLog xmlns="http://www.liquibase.org/xml/ns/dbchangelog"
+                   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+                   xsi:schemaLocation="http://www.liquibase.org/xml/ns/dbchangelog https://www.liquibase.org/xml/ns/dbchangelog/dbchangelog-latest.xsd">
+    <changeSet id="20241117234100" author="ece.eren">
+        <addColumn tableName="slide">
+            <column name="hidden" type="datetime(3)"/>
+        </addColumn>
+    </changeSet>
+</databaseChangeLog>
\ No newline at end of file
diff --git a/src/main/resources/config/liquibase/master.xml b/src/main/resources/config/liquibase/master.xml
index 51e4fe5294ea..c545405054ae 100644
--- a/src/main/resources/config/liquibase/master.xml
+++ b/src/main/resources/config/liquibase/master.xml
@@ -33,7 +33,7 @@
     <include file="classpath:config/liquibase/changelog/20241010101010_changelog.xml" relativeToChangelogFile="false"/>
     <include file="classpath:config/liquibase/changelog/20241018053210_changelog.xml" relativeToChangelogFile="false"/>
     <include file="classpath:config/liquibase/changelog/20241023456789_changelog.xml" relativeToChangelogFile="false"/>
-    <include file="classpath:config/liquibase/changelog/20241117192154_changelog.xml" relativeToChangelogFile="false"/>
+    <include file="classpath:config/liquibase/changelog/20241117234100_changelog.xml" relativeToChangelogFile="false"/>
 
     <!-- NOTE: please use the format "YYYYMMDDhhmmss_changelog.xml", i.e. year month day hour minutes seconds and not something else! -->
     <!-- we should also stay in a chronological order! -->
diff --git a/src/main/webapp/app/lecture/lecture-unit/lecture-unit-management/attachmentUnit.service.ts b/src/main/webapp/app/lecture/lecture-unit/lecture-unit-management/attachmentUnit.service.ts
index d2a33f5f2a06..11f7c790736f 100644
--- a/src/main/webapp/app/lecture/lecture-unit/lecture-unit-management/attachmentUnit.service.ts
+++ b/src/main/webapp/app/lecture/lecture-unit/lecture-unit-management/attachmentUnit.service.ts
@@ -31,11 +31,12 @@ export class AttachmentUnitService {
             .pipe(map((res: EntityResponseType) => this.lectureUnitService.convertLectureUnitResponseDatesFromServer(res)));
     }
 
-    update(lectureId: number, attachmentUnitId: number, formData: FormData, notificationText?: string): Observable<EntityResponseType> {
+    update(lectureId: number, attachmentUnitId: number, formData: FormData, notificationText?: string, hiddenPages?: string): Observable<EntityResponseType> {
         return this.httpClient
             .put<AttachmentUnit>(
                 `${this.resourceURL}/lectures/${lectureId}/attachment-units/${attachmentUnitId}?keepFilename=true` +
-                    (notificationText ? `&notificationText=${notificationText}` : ''),
+                    (notificationText ? `&notificationText=${notificationText}` : '') +
+                    (hiddenPages ? `&hiddenPages=${hiddenPages}` : ''),
                 formData,
                 { observe: 'response' },
             )
@@ -71,17 +72,4 @@ export class AttachmentUnitService {
     getAttachmentFile(courseId: number, attachmentUnitId: number): Observable<Blob> {
         return this.httpClient.get(`${this.resourceURL}/files/courses/${courseId}/attachment-units/${attachmentUnitId}`, { responseType: 'blob' });
     }
-
-    /**
-     * Retrieve the hidden attachment unit associated with a given parent attachment unit ID
-     *
-     * @param lectureId The ID of the lecture that the attachment unit belongs to
-     * @param parentAttachmentUnitId The ID of the parent attachment unit whose hidden attachment unit is to be retrieved
-     * @returns An Observable that emits an EntityResponseType containing the Attachment Unit object when the HTTP request completes successfully
-     */
-    getAttachmentUnitByParentAttachmentUnitId(lectureId: number, parentAttachmentUnitId: number): Observable<EntityResponseType> {
-        return this.httpClient
-            .get<AttachmentUnit>(`${this.resourceURL}/lectures/${lectureId}/attachment-units/${parentAttachmentUnitId}/hiddenAttachment`, { observe: 'response' })
-            .pipe(map((res: EntityResponseType) => this.lectureUnitService.convertLectureUnitResponseDatesFromServer(res)));
-    }
 }
diff --git a/src/main/webapp/app/lecture/pdf-preview/pdf-preview.component.ts b/src/main/webapp/app/lecture/pdf-preview/pdf-preview.component.ts
index ec5e7f96945c..da1e95da20b6 100644
--- a/src/main/webapp/app/lecture/pdf-preview/pdf-preview.component.ts
+++ b/src/main/webapp/app/lecture/pdf-preview/pdf-preview.component.ts
@@ -17,7 +17,6 @@ import { MAX_FILE_SIZE } from 'app/shared/constants/input.constants';
 import { PdfPreviewThumbnailGridComponent } from 'app/lecture/pdf-preview/pdf-preview-thumbnail-grid/pdf-preview-thumbnail-grid.component';
 import { LectureUnitService } from 'app/lecture/lecture-unit/lecture-unit-management/lectureUnit.service';
 import { PDFDocument } from 'pdf-lib';
-import { cloneDeep } from 'lodash-es';
 
 @Component({
     selector: 'jhi-pdf-preview-component',
@@ -128,9 +127,7 @@ export class PdfPreviewComponent implements OnInit, OnDestroy {
     }
 
     getHiddenPages() {
-        return Array.from(document.querySelectorAll('[id^="show-button-"]'))
-            .map((el) => el.id.match(/show-button-(\d+)/)?.[1])
-            .join(',');
+        return Array.from(document.querySelectorAll('[id^="show-button-"]')).map((el) => el.id.match(/show-button-(\d+)/)?.[1]);
     }
 
     /**
@@ -159,7 +156,7 @@ export class PdfPreviewComponent implements OnInit, OnDestroy {
                 },
             });
         } else if (this.attachmentUnit()) {
-            const finalHiddenPages = this.getHiddenPages();
+            const finalHiddenPages = this.getHiddenPages().join(',');
             this.attachmentToBeEdited.set(this.attachmentUnit()!.attachment!);
             this.attachmentToBeEdited()!.version!++;
             this.attachmentToBeEdited()!.uploadDate = dayjs();
@@ -169,57 +166,10 @@ export class PdfPreviewComponent implements OnInit, OnDestroy {
             formData.append('attachment', objectToJsonBlob(this.attachmentToBeEdited()!));
             formData.append('attachmentUnit', objectToJsonBlob(this.attachmentUnit()!));
 
-            this.attachmentUnitService.update(this.attachmentUnit()!.lecture!.id!, this.attachmentUnit()!.id!, formData).subscribe({
+            this.attachmentUnitService.update(this.attachmentUnit()!.lecture!.id!, this.attachmentUnit()!.id!, formData, undefined, finalHiddenPages).subscribe({
                 next: async () => {
-                    if (finalHiddenPages!.length > 0) {
-                        const pdfFileWithHiddenPages = await this.createHiddenVersionOfAttachment(Array.from(finalHiddenPages!.split(',').map(Number)));
-                        const attachmentUnitWithHiddenPages = cloneDeep(this.attachmentUnit()!);
-                        const attachmentWithHiddenPages = cloneDeep(this.attachmentUnit()!.attachment!);
-
-                        attachmentWithHiddenPages.id = undefined;
-                        attachmentWithHiddenPages.name = `${attachmentWithHiddenPages.name}_hidden`;
-                        attachmentUnitWithHiddenPages.id = undefined;
-
-                        const formData = new FormData();
-
-                        formData.append('file', pdfFileWithHiddenPages!);
-                        formData.append('attachment', objectToJsonBlob(attachmentWithHiddenPages!));
-                        formData.append('attachmentUnit', objectToJsonBlob(attachmentUnitWithHiddenPages!));
-
-                        this.attachmentUnitService.getAttachmentUnitByParentAttachmentUnitId(this.attachmentUnit()!.lecture!.id!, this.attachmentUnit()!.id!).subscribe({
-                            next: async (attachmentUnitRes) => {
-                                if (attachmentUnitRes.body && attachmentUnitRes.body.id) {
-                                    this.attachmentUnitService.update(this.attachmentUnit()!.lecture!.id!, attachmentUnitRes.body.id, formData).subscribe({
-                                        next: () => {
-                                            this.alertService.success('artemisApp.attachment.pdfPreview.attachmentUpdateSuccess');
-                                            this.alertService.success('artemisApp.attachment.pdfPreview.hiddenAttachmentUnitUpdateSuccess');
-                                            this.router.navigate(['course-management', this.course()?.id, 'lectures', this.attachmentUnit()!.lecture!.id, 'unit-management']);
-                                        },
-                                        error: (error) => {
-                                            this.alertService.error('artemisApp.attachment.pdfPreview.hiddenAttachmentUnitUpdateError', { error: error.message });
-                                        },
-                                    });
-                                } else {
-                                    this.attachmentUnitService.create(formData, this.attachmentUnit()!.lecture!.id!).subscribe({
-                                        next: () => {
-                                            this.alertService.success('artemisApp.attachment.pdfPreview.attachmentUpdateSuccess');
-                                            this.alertService.success('artemisApp.attachment.pdfPreview.hiddenAttachmentUnitCreateSuccess');
-                                            this.router.navigate(['course-management', this.course()?.id, 'lectures', this.attachmentUnit()!.lecture!.id, 'unit-management']);
-                                        },
-                                        error: (error) => {
-                                            this.alertService.error('artemisApp.attachment.pdfPreview.hiddenAttachmentUnitCreateError', { error: error.message });
-                                        },
-                                    });
-                                }
-                            },
-                            error: (error) => {
-                                this.alertService.error('artemisApp.attachment.pdfPreview.attachmentUpdateError', { error: error.message });
-                            },
-                        });
-                    } else {
-                        this.alertService.success('artemisApp.attachment.pdfPreview.attachmentUpdateSuccess');
-                        this.router.navigate(['course-management', this.course()?.id, 'lectures', this.attachment()!.lecture!.id, 'attachments']);
-                    }
+                    this.alertService.success('artemisApp.attachment.pdfPreview.attachmentUpdateSuccess');
+                    this.router.navigate(['course-management', this.course()?.id, 'lectures', this.attachment()!.lecture!.id, 'attachments']);
                 },
                 error: (error) => {
                     this.alertService.error('artemisApp.attachment.pdfPreview.attachmentUpdateError', { error: error.message });

From e8b80546bc2eab037424a5408edd424c42ac4391 Mon Sep 17 00:00:00 2001
From: Ece Eren <aybikeceren@gmail.com>
Date: Mon, 18 Nov 2024 01:25:32 +0100
Subject: [PATCH 09/11] Update JSDoc and JavaDoc

---
 .../lecture/service/SlideSplitterService.java |  2 ++
 .../lecture/web/AttachmentUnitResource.java   |  1 +
 .../pdf-preview/pdf-preview.component.ts      | 29 ++++---------------
 3 files changed, 8 insertions(+), 24 deletions(-)

diff --git a/src/main/java/de/tum/cit/aet/artemis/lecture/service/SlideSplitterService.java b/src/main/java/de/tum/cit/aet/artemis/lecture/service/SlideSplitterService.java
index 212c565055c1..269b9ece502a 100644
--- a/src/main/java/de/tum/cit/aet/artemis/lecture/service/SlideSplitterService.java
+++ b/src/main/java/de/tum/cit/aet/artemis/lecture/service/SlideSplitterService.java
@@ -59,6 +59,7 @@ public SlideSplitterService(FileService fileService, SlideRepository slideReposi
      * Splits an Attachment Unit file into single slides and saves them as PNG files asynchronously.
      *
      * @param attachmentUnit The attachment unit to which the slides belong.
+     * @param hiddenPages    The hidden pages of the attachment unit.
      */
     @Async
     public void splitAttachmentUnitIntoSingleSlides(AttachmentUnit attachmentUnit, String hiddenPages) {
@@ -80,6 +81,7 @@ public void splitAttachmentUnitIntoSingleSlides(AttachmentUnit attachmentUnit, S
      * @param attachmentUnit The attachment unit to which the slides belong.
      * @param document       The PDF document that is already loaded.
      * @param pdfFilename    The name of the PDF file.
+     * @param hiddenPages    The hidden pages of the attachment unit.
      */
     public void splitAttachmentUnitIntoSingleSlides(PDDocument document, AttachmentUnit attachmentUnit, String pdfFilename, String hiddenPages) {
         log.debug("Splitting Attachment Unit file {} into single slides", attachmentUnit.getAttachment().getName());
diff --git a/src/main/java/de/tum/cit/aet/artemis/lecture/web/AttachmentUnitResource.java b/src/main/java/de/tum/cit/aet/artemis/lecture/web/AttachmentUnitResource.java
index 4ec38db09a74..2a883f789b6c 100644
--- a/src/main/java/de/tum/cit/aet/artemis/lecture/web/AttachmentUnitResource.java
+++ b/src/main/java/de/tum/cit/aet/artemis/lecture/web/AttachmentUnitResource.java
@@ -117,6 +117,7 @@ public ResponseEntity<AttachmentUnit> getAttachmentUnit(@PathVariable Long attac
      * @param file             the optional file to upload
      * @param keepFilename     specifies if the original filename should be kept or not
      * @param notificationText the text to be used for the notification. No notification will be sent if the parameter is not set
+     * @param hiddenPages      the pages to be hidden in the attachment unit. No hidden pages will be sent if the parameter is not set
      * @return the ResponseEntity with status 200 (OK) and with body the updated attachmentUnit
      */
     @PutMapping(value = "lectures/{lectureId}/attachment-units/{attachmentUnitId}", consumes = MediaType.MULTIPART_FORM_DATA_VALUE)
diff --git a/src/main/webapp/app/lecture/pdf-preview/pdf-preview.component.ts b/src/main/webapp/app/lecture/pdf-preview/pdf-preview.component.ts
index da1e95da20b6..c4be3fd625dd 100644
--- a/src/main/webapp/app/lecture/pdf-preview/pdf-preview.component.ts
+++ b/src/main/webapp/app/lecture/pdf-preview/pdf-preview.component.ts
@@ -126,6 +126,11 @@ export class PdfPreviewComponent implements OnInit, OnDestroy {
         return false;
     }
 
+    /**
+     * Retrieves an array of hidden page numbers from elements with IDs starting with "show-button-".
+     *
+     * @returns An array of strings representing the hidden page numbers.
+     */
     getHiddenPages() {
         return Array.from(document.querySelectorAll('[id^="show-button-"]')).map((el) => el.id.match(/show-button-(\d+)/)?.[1]);
     }
@@ -238,30 +243,6 @@ export class PdfPreviewComponent implements OnInit, OnDestroy {
         }
     }
 
-    /**
-     * Creates a hidden version of the current PDF attachment by removing specified pages.
-     *
-     * @param hiddenPages - An array of page numbers to be removed from the original PDF.
-     * @returns A promise that resolves to a new `File` object representing the modified PDF, or undefined if an error occurs.
-     */
-    async createHiddenVersionOfAttachment(hiddenPages: number[]) {
-        try {
-            const fileName = this.attachmentUnit()!.attachment!.name;
-            const existingPdfBytes = await this.currentPdfBlob()!.arrayBuffer();
-            const hiddenPdfDoc = await PDFDocument.load(existingPdfBytes);
-
-            const pagesToDelete = hiddenPages.map((page) => page - 1).sort((a, b) => b - a);
-            pagesToDelete.forEach((pageIndex) => {
-                hiddenPdfDoc.removePage(pageIndex);
-            });
-
-            const pdfBytes = await hiddenPdfDoc.save();
-            return new File([pdfBytes], `${fileName}_hidden.pdf`, { type: 'application/pdf' });
-        } catch (error) {
-            this.alertService.error('artemisApp.attachment.pdfPreview.pageDeleteError', { error: error.message });
-        }
-    }
-
     /**
      * Adds a selected PDF file at the end of the current PDF document.
      * @param event - The event containing the file input.

From 1c24c93ce4a71234b28f29d10eea8dca9b8eeee2 Mon Sep 17 00:00:00 2001
From: Ece Eren <aybikeceren@gmail.com>
Date: Mon, 18 Nov 2024 19:19:43 +0100
Subject: [PATCH 10/11] Fix bugs and get hidden sides from Slide table

---
 .../lecture/repository/SlideRepository.java   | 17 +++++++++++++
 .../service/AttachmentUnitService.java        |  5 ++--
 .../service/LectureUnitImportService.java     |  2 +-
 .../service/LectureUnitProcessingService.java |  2 +-
 .../lecture/service/SlideSplitterService.java |  2 +-
 .../lecture/web/AttachmentUnitResource.java   | 24 ++++++++++++++-----
 .../attachmentUnit.service.ts                 | 11 +++++++++
 .../pdf-preview/pdf-preview.component.ts      |  9 +++++--
 8 files changed, 59 insertions(+), 13 deletions(-)

diff --git a/src/main/java/de/tum/cit/aet/artemis/lecture/repository/SlideRepository.java b/src/main/java/de/tum/cit/aet/artemis/lecture/repository/SlideRepository.java
index 3470d2ccf477..1fa0138a16bd 100644
--- a/src/main/java/de/tum/cit/aet/artemis/lecture/repository/SlideRepository.java
+++ b/src/main/java/de/tum/cit/aet/artemis/lecture/repository/SlideRepository.java
@@ -2,7 +2,11 @@
 
 import static de.tum.cit.aet.artemis.core.config.Constants.PROFILE_CORE;
 
+import java.util.List;
+
 import org.springframework.context.annotation.Profile;
+import org.springframework.data.jpa.repository.Query;
+import org.springframework.data.repository.query.Param;
 import org.springframework.stereotype.Repository;
 
 import de.tum.cit.aet.artemis.core.repository.base.ArtemisJpaRepository;
@@ -17,4 +21,17 @@ public interface SlideRepository extends ArtemisJpaRepository<Slide, Long> {
 
     Slide findSlideByAttachmentUnitIdAndSlideNumber(Long attachmentUnitId, Integer slideNumber);
 
+    /**
+     * Finds the list of hidden slide IDs for a specific attachment unit ID.
+     *
+     * @param attachmentUnitId The ID of the attachment unit.
+     * @return List of hidden slide IDs.
+     */
+    @Query("""
+            SELECT s.slideNumber
+            FROM Slide s
+            WHERE s.attachmentUnit.id = :attachmentUnitId AND s.hidden IS NOT NULL
+            """)
+    List<Integer> findHiddenSlideNumbersByAttachmentUnitId(@Param("attachmentUnitId") Long attachmentUnitId);
+
 }
diff --git a/src/main/java/de/tum/cit/aet/artemis/lecture/service/AttachmentUnitService.java b/src/main/java/de/tum/cit/aet/artemis/lecture/service/AttachmentUnitService.java
index e86d7c22e7f5..6ba2522707c7 100644
--- a/src/main/java/de/tum/cit/aet/artemis/lecture/service/AttachmentUnitService.java
+++ b/src/main/java/de/tum/cit/aet/artemis/lecture/service/AttachmentUnitService.java
@@ -108,10 +108,11 @@ public AttachmentUnit createAttachmentUnit(AttachmentUnit attachmentUnit, Attach
      * @param updateAttachment       The new attachment data.
      * @param updateFile             The optional file.
      * @param keepFilename           Whether to keep the original filename or not.
+     * @param hiddenPages            The hidden pages of attachment unit.
      * @return The updated attachment unit.
      */
     public AttachmentUnit updateAttachmentUnit(AttachmentUnit existingAttachmentUnit, AttachmentUnit updateUnit, Attachment updateAttachment, MultipartFile updateFile,
-            boolean keepFilename) {
+            boolean keepFilename, String hiddenPages) {
         Set<CompetencyLectureUnitLink> existingCompetencyLinks = new HashSet<>(existingAttachmentUnit.getCompetencyLinks());
 
         existingAttachmentUnit.setDescription(updateUnit.getDescription());
@@ -144,7 +145,7 @@ public AttachmentUnit updateAttachmentUnit(AttachmentUnit existingAttachmentUnit
             }
             // Split the updated file into single slides only if it is a pdf
             if (Objects.equals(FilenameUtils.getExtension(updateFile.getOriginalFilename()), "pdf")) {
-                slideSplitterService.splitAttachmentUnitIntoSingleSlides(savedAttachmentUnit);
+                slideSplitterService.splitAttachmentUnitIntoSingleSlides(savedAttachmentUnit, hiddenPages);
             }
             if (pyrisWebhookService.isPresent() && irisSettingsRepository.isPresent()) {
                 pyrisWebhookService.get().autoUpdateAttachmentUnitsInPyris(savedAttachmentUnit.getLecture().getCourse().getId(), List.of(savedAttachmentUnit));
diff --git a/src/main/java/de/tum/cit/aet/artemis/lecture/service/LectureUnitImportService.java b/src/main/java/de/tum/cit/aet/artemis/lecture/service/LectureUnitImportService.java
index 0c537eda34bc..f72dc1b8a1b5 100644
--- a/src/main/java/de/tum/cit/aet/artemis/lecture/service/LectureUnitImportService.java
+++ b/src/main/java/de/tum/cit/aet/artemis/lecture/service/LectureUnitImportService.java
@@ -119,7 +119,7 @@ public LectureUnit importLectureUnit(final LectureUnit importedLectureUnit) {
                 attachment.setAttachmentUnit(attachmentUnit);
                 attachmentRepository.save(attachment);
                 if (attachment.getLink().endsWith(".pdf")) {
-                    slideSplitterService.splitAttachmentUnitIntoSingleSlides(attachmentUnit);
+                    slideSplitterService.splitAttachmentUnitIntoSingleSlides(attachmentUnit, null);
                 }
                 attachmentUnit.setAttachment(attachment);
                 return attachmentUnit;
diff --git a/src/main/java/de/tum/cit/aet/artemis/lecture/service/LectureUnitProcessingService.java b/src/main/java/de/tum/cit/aet/artemis/lecture/service/LectureUnitProcessingService.java
index 602106099847..9c96272a9da7 100644
--- a/src/main/java/de/tum/cit/aet/artemis/lecture/service/LectureUnitProcessingService.java
+++ b/src/main/java/de/tum/cit/aet/artemis/lecture/service/LectureUnitProcessingService.java
@@ -109,7 +109,7 @@ public List<AttachmentUnit> splitAndSaveUnits(LectureUnitSplitInformationDTO lec
 
                 MultipartFile multipartFile = fileService.convertByteArrayToMultipart(lectureUnit.unitName(), ".pdf", outputStream.toByteArray());
                 AttachmentUnit savedAttachmentUnit = attachmentUnitService.createAttachmentUnit(attachmentUnit, attachment, lecture, multipartFile, true);
-                slideSplitterService.splitAttachmentUnitIntoSingleSlides(documentUnits.getFirst(), savedAttachmentUnit, multipartFile.getOriginalFilename());
+                slideSplitterService.splitAttachmentUnitIntoSingleSlides(documentUnits.getFirst(), savedAttachmentUnit, multipartFile.getOriginalFilename(), null);
                 documentUnits.getFirst().close(); // make sure to close the document
                 units.add(savedAttachmentUnit);
             }
diff --git a/src/main/java/de/tum/cit/aet/artemis/lecture/service/SlideSplitterService.java b/src/main/java/de/tum/cit/aet/artemis/lecture/service/SlideSplitterService.java
index 269b9ece502a..b228cd223357 100644
--- a/src/main/java/de/tum/cit/aet/artemis/lecture/service/SlideSplitterService.java
+++ b/src/main/java/de/tum/cit/aet/artemis/lecture/service/SlideSplitterService.java
@@ -107,7 +107,7 @@ public void splitAttachmentUnitIntoSingleSlides(PDDocument document, AttachmentU
                 slide.setSlideImagePath(FilePathService.publicPathForActualPath(savePath, (long) slideNumber).toString());
                 slide.setSlideNumber(slideNumber);
                 slide.setAttachmentUnit(attachmentUnit);
-                slide.setHidden(hiddenPagesList.contains(slide.getSlideNumber()) ? java.sql.Date.valueOf(FOREVER) : null);
+                slide.setHidden(hiddenPagesList.contains(slideNumber) ? java.sql.Date.valueOf(FOREVER) : null);
                 slideRepository.save(slide);
 
             }
diff --git a/src/main/java/de/tum/cit/aet/artemis/lecture/web/AttachmentUnitResource.java b/src/main/java/de/tum/cit/aet/artemis/lecture/web/AttachmentUnitResource.java
index 2a883f789b6c..1118fc386477 100644
--- a/src/main/java/de/tum/cit/aet/artemis/lecture/web/AttachmentUnitResource.java
+++ b/src/main/java/de/tum/cit/aet/artemis/lecture/web/AttachmentUnitResource.java
@@ -44,6 +44,7 @@
 import de.tum.cit.aet.artemis.lecture.dto.LectureUnitSplitInformationDTO;
 import de.tum.cit.aet.artemis.lecture.repository.AttachmentUnitRepository;
 import de.tum.cit.aet.artemis.lecture.repository.LectureRepository;
+import de.tum.cit.aet.artemis.lecture.repository.SlideRepository;
 import de.tum.cit.aet.artemis.lecture.service.AttachmentUnitService;
 import de.tum.cit.aet.artemis.lecture.service.LectureUnitProcessingService;
 import de.tum.cit.aet.artemis.lecture.service.SlideSplitterService;
@@ -75,9 +76,11 @@ public class AttachmentUnitResource {
 
     private final FileService fileService;
 
+    private final SlideRepository slideRepository;
+
     public AttachmentUnitResource(AttachmentUnitRepository attachmentUnitRepository, LectureRepository lectureRepository, LectureUnitProcessingService lectureUnitProcessingService,
             AuthorizationCheckService authorizationCheckService, GroupNotificationService groupNotificationService, AttachmentUnitService attachmentUnitService,
-            CompetencyProgressService competencyProgressService, SlideSplitterService slideSplitterService, FileService fileService) {
+            CompetencyProgressService competencyProgressService, SlideSplitterService slideSplitterService, FileService fileService, SlideRepository slideRepository) {
         this.attachmentUnitRepository = attachmentUnitRepository;
         this.lectureUnitProcessingService = lectureUnitProcessingService;
         this.lectureRepository = lectureRepository;
@@ -87,6 +90,7 @@ public AttachmentUnitResource(AttachmentUnitRepository attachmentUnitRepository,
         this.competencyProgressService = competencyProgressService;
         this.slideSplitterService = slideSplitterService;
         this.fileService = fileService;
+        this.slideRepository = slideRepository;
     }
 
     /**
@@ -130,16 +134,12 @@ public ResponseEntity<AttachmentUnit> updateAttachmentUnit(@PathVariable Long le
         checkAttachmentUnitCourseAndLecture(existingAttachmentUnit, lectureId);
         authorizationCheckService.checkHasAtLeastRoleInCourseElseThrow(Role.EDITOR, existingAttachmentUnit.getLecture().getCourse(), null);
 
-        AttachmentUnit savedAttachmentUnit = attachmentUnitService.updateAttachmentUnit(existingAttachmentUnit, attachmentUnit, attachment, file, keepFilename);
+        AttachmentUnit savedAttachmentUnit = attachmentUnitService.updateAttachmentUnit(existingAttachmentUnit, attachmentUnit, attachment, file, keepFilename, hiddenPages);
 
         if (notificationText != null) {
             groupNotificationService.notifyStudentGroupAboutAttachmentChange(savedAttachmentUnit.getAttachment(), notificationText);
         }
 
-        if (Objects.equals(FilenameUtils.getExtension(file.getOriginalFilename()), "pdf")) {
-            slideSplitterService.splitAttachmentUnitIntoSingleSlides(savedAttachmentUnit, hiddenPages);
-        }
-
         return ResponseEntity.ok(savedAttachmentUnit);
     }
 
@@ -337,4 +337,16 @@ private void checkFile(Path filePath) {
             throw new BadRequestAlertException("The file must be a pdf", ENTITY_NAME, "wrongFileType");
         }
     }
+
+    @GetMapping("lectures/{lectureId}/attachment-units/{attachmentUnitId}/hidden-slides")
+    @EnforceAtLeastEditor
+    public ResponseEntity<List<Integer>> getAttachmentUnitHiddenSlides(@PathVariable Long attachmentUnitId, @PathVariable Long lectureId) {
+        log.debug("REST request to get hidden slides of AttachmentUnit : {}", attachmentUnitId);
+        List<Integer> hiddenSlides = slideRepository.findHiddenSlideNumbersByAttachmentUnitId(attachmentUnitId);
+        AttachmentUnit attachmentUnit = attachmentUnitRepository.findByIdElseThrow(attachmentUnitId);
+        checkAttachmentUnitCourseAndLecture(attachmentUnit, lectureId);
+        authorizationCheckService.checkHasAtLeastRoleInCourseElseThrow(Role.EDITOR, attachmentUnit.getLecture().getCourse(), null);
+
+        return ResponseEntity.ok().body(hiddenSlides);
+    }
 }
diff --git a/src/main/webapp/app/lecture/lecture-unit/lecture-unit-management/attachmentUnit.service.ts b/src/main/webapp/app/lecture/lecture-unit/lecture-unit-management/attachmentUnit.service.ts
index 11f7c790736f..1eaec59a56e8 100644
--- a/src/main/webapp/app/lecture/lecture-unit/lecture-unit-management/attachmentUnit.service.ts
+++ b/src/main/webapp/app/lecture/lecture-unit/lecture-unit-management/attachmentUnit.service.ts
@@ -72,4 +72,15 @@ export class AttachmentUnitService {
     getAttachmentFile(courseId: number, attachmentUnitId: number): Observable<Blob> {
         return this.httpClient.get(`${this.resourceURL}/files/courses/${courseId}/attachment-units/${attachmentUnitId}`, { responseType: 'blob' });
     }
+
+    /**
+     * Retrieve the hidden slide numbers associated with a given attachment unit ID.
+     *
+     * @param lectureId The ID of the lecture that the Attachment Unit belongs to.
+     * @param attachmentUnitId The ID of the attachment unit.
+     * @returns An Observable that emits a list of integers representing hidden slide numbers.
+     */
+    getHiddenSlides(lectureId: number, attachmentUnitId: number): Observable<number[]> {
+        return this.httpClient.get<number[]>(`${this.resourceURL}/lectures/${lectureId}/attachment-units/${attachmentUnitId}/hidden-slides`);
+    }
 }
diff --git a/src/main/webapp/app/lecture/pdf-preview/pdf-preview.component.ts b/src/main/webapp/app/lecture/pdf-preview/pdf-preview.component.ts
index c4be3fd625dd..b113c8dea87b 100644
--- a/src/main/webapp/app/lecture/pdf-preview/pdf-preview.component.ts
+++ b/src/main/webapp/app/lecture/pdf-preview/pdf-preview.component.ts
@@ -79,7 +79,12 @@ export class PdfPreviewComponent implements OnInit, OnDestroy {
                 });
             } else if ('attachmentUnit' in data) {
                 this.attachmentUnit.set(data.attachmentUnit);
-                this.hiddenPages.set(new Set(data.attachmentUnit.hiddenPages?.split(',').map(Number) || []));
+                this.attachmentUnitService.getHiddenSlides(this.attachmentUnit()!.lecture!.id!, this.attachmentUnit()!.id!).subscribe({
+                    next: (hiddenPages: number[]) => {
+                        this.hiddenPages.set(new Set(hiddenPages));
+                    },
+                    error: (error: HttpErrorResponse) => onError(this.alertService, error),
+                });
                 this.attachmentUnitSub = this.attachmentUnitService.getAttachmentFile(this.course()!.id!, this.attachmentUnit()!.id!).subscribe({
                     next: (blob: Blob) => {
                         this.currentPdfBlob.set(blob);
@@ -174,7 +179,7 @@ export class PdfPreviewComponent implements OnInit, OnDestroy {
             this.attachmentUnitService.update(this.attachmentUnit()!.lecture!.id!, this.attachmentUnit()!.id!, formData, undefined, finalHiddenPages).subscribe({
                 next: async () => {
                     this.alertService.success('artemisApp.attachment.pdfPreview.attachmentUpdateSuccess');
-                    this.router.navigate(['course-management', this.course()?.id, 'lectures', this.attachment()!.lecture!.id, 'attachments']);
+                    this.router.navigate(['course-management', this.course()?.id, 'lectures', this.attachmentUnit()!.lecture!.id, 'unit-management']);
                 },
                 error: (error) => {
                     this.alertService.error('artemisApp.attachment.pdfPreview.attachmentUpdateError', { error: error.message });

From caf29325ab9b65e88dd8fd43ea74f2c61b68231b Mon Sep 17 00:00:00 2001
From: Ece Eren <aybikeceren@gmail.com>
Date: Mon, 18 Nov 2024 21:48:53 +0100
Subject: [PATCH 11/11] Track hidden slides indexes

---
 .../pdf-preview-thumbnail-grid.component.ts   | 11 +++++--
 .../pdf-preview/pdf-preview.component.html    |  2 +-
 .../pdf-preview/pdf-preview.component.ts      | 30 ++++++++++++++++---
 3 files changed, 35 insertions(+), 8 deletions(-)

diff --git a/src/main/webapp/app/lecture/pdf-preview/pdf-preview-thumbnail-grid/pdf-preview-thumbnail-grid.component.ts b/src/main/webapp/app/lecture/pdf-preview/pdf-preview-thumbnail-grid/pdf-preview-thumbnail-grid.component.ts
index 50bd4e11433d..e20bd50d9f08 100644
--- a/src/main/webapp/app/lecture/pdf-preview/pdf-preview-thumbnail-grid/pdf-preview-thumbnail-grid.component.ts
+++ b/src/main/webapp/app/lecture/pdf-preview/pdf-preview-thumbnail-grid/pdf-preview-thumbnail-grid.component.ts
@@ -1,4 +1,4 @@
-import { Component, ElementRef, effect, inject, input, output, signal, viewChild } from '@angular/core';
+import { Component, ElementRef, OnChanges, SimpleChanges, effect, inject, input, output, signal, viewChild } from '@angular/core';
 import * as PDFJS from 'pdfjs-dist';
 import 'pdfjs-dist/build/pdf.worker';
 import { ArtemisSharedModule } from 'app/shared/shared.module';
@@ -14,7 +14,7 @@ import { clone } from 'lodash-es';
     standalone: true,
     imports: [ArtemisSharedModule, PdfPreviewEnlargedCanvasComponent],
 })
-export class PdfPreviewThumbnailGridComponent {
+export class PdfPreviewThumbnailGridComponent implements OnChanges {
     pdfContainer = viewChild.required<ElementRef<HTMLDivElement>>('pdfContainer');
 
     readonly DEFAULT_SLIDE_WIDTH = 250;
@@ -42,10 +42,15 @@ export class PdfPreviewThumbnailGridComponent {
     // Injected services
     private readonly alertService = inject(AlertService);
 
+    ngOnChanges(changes: SimpleChanges): void {
+        if (changes['hiddenPages']) {
+            this.newHiddenPages.set(clone(this.hiddenPages()!));
+        }
+    }
+
     constructor() {
         effect(
             () => {
-                this.newHiddenPages.set(clone(this.hiddenPages()!));
                 this.loadOrAppendPdf(this.currentPdfUrl()!, this.appendFile());
             },
             { allowSignalWrites: true },
diff --git a/src/main/webapp/app/lecture/pdf-preview/pdf-preview.component.html b/src/main/webapp/app/lecture/pdf-preview/pdf-preview.component.html
index 5ed0f41459f8..b4b2ec510e1a 100644
--- a/src/main/webapp/app/lecture/pdf-preview/pdf-preview.component.html
+++ b/src/main/webapp/app/lecture/pdf-preview/pdf-preview.component.html
@@ -48,7 +48,7 @@ <h4>
                 (isPdfLoading)="isPdfLoading.set($event)"
                 (selectedPagesOutput)="selectedPages.set($event)"
                 (totalPagesOutput)="totalPages.set($event)"
-                (newHiddenPagesOutput)="newHiddenPages.set($event)"
+                (newHiddenPagesOutput)="hiddenPages.set($event)"
             />
         } @else {
             <div class="empty-pdf-container"></div>
diff --git a/src/main/webapp/app/lecture/pdf-preview/pdf-preview.component.ts b/src/main/webapp/app/lecture/pdf-preview/pdf-preview.component.ts
index b113c8dea87b..cb41ce2f1f8a 100644
--- a/src/main/webapp/app/lecture/pdf-preview/pdf-preview.component.ts
+++ b/src/main/webapp/app/lecture/pdf-preview/pdf-preview.component.ts
@@ -114,7 +114,8 @@ export class PdfPreviewComponent implements OnInit, OnDestroy {
      * Triggers the file input to select files.
      */
     triggerFileInput(): void {
-        this.fileInput().nativeElement.click();
+        //this.fileInput().nativeElement.click();
+        console.log(this.hiddenPages());
     }
 
     /**
@@ -228,9 +229,9 @@ export class PdfPreviewComponent implements OnInit, OnDestroy {
             const pagesToDelete = Array.from(this.selectedPages()!)
                 .map((page) => page - 1)
                 .sort((a, b) => b - a);
-            pagesToDelete.forEach((pageIndex) => {
-                pdfDoc.removePage(pageIndex);
-            });
+
+            this.updateHiddenPages(pagesToDelete);
+            pagesToDelete.forEach((pageIndex) => pdfDoc.removePage(pageIndex));
 
             this.isFileChanged.set(true);
             const pdfBytes = await pdfDoc.save();
@@ -248,6 +249,27 @@ export class PdfPreviewComponent implements OnInit, OnDestroy {
         }
     }
 
+    /**
+     * Updates hidden pages after selected pages are deleted.
+     * @param pagesToDelete - Array of pages to be deleted (0-indexed).
+     */
+    private updateHiddenPages(pagesToDelete: number[]) {
+        const updatedHiddenPages = new Set<number>();
+        this.hiddenPages().forEach((hiddenPage) => {
+            // Adjust hiddenPage based on the deleted pages
+            const adjustedPage = pagesToDelete.reduce((acc, pageIndex) => {
+                if (acc === pageIndex + 1) {
+                    return;
+                }
+                return pageIndex < acc - 1 ? acc - 1 : acc;
+            }, hiddenPage);
+            if (adjustedPage !== -1) {
+                updatedHiddenPages.add(adjustedPage!);
+            }
+        });
+        this.hiddenPages.set(updatedHiddenPages);
+    }
+
     /**
      * Adds a selected PDF file at the end of the current PDF document.
      * @param event - The event containing the file input.