Feature/undo page break (#2389)

* Fix delete selected
Fix add page break where selected
Added undo logic for page breaks

* Add pages undo capability

* Fix page break when selected logic

src/main/resources/static/js/multitool/commands/page-break.js

@@ -0,0 +1,59 @@
+import {Command} from './command.js';
+
+export class PageBreakCommand extends Command {
+  constructor(elements, isSelectedInWindow, selectedPages, pageBreakCallback, pagesContainer) {
+    super();
+    this.elements = elements;
+    this.isSelectedInWindow = isSelectedInWindow;
+    this.selectedPages = selectedPages;
+    this.pageBreakCallback = pageBreakCallback;
+    this.pagesContainer = pagesContainer;
+    this.addedElements = [];
+    this.originalStates = Array.from(elements, (element) => ({
+      element,
+      hasContent: element.innerHTML.trim() !== '',
+    }));
+  }
+
+  async execute() {
+    const undoBtn = document.getElementById('undo-btn');
+    undoBtn.disabled = true;
+    for (const [index, element] of this.elements.entries()) {
+      if (!this.isSelectedInWindow || this.selectedPages.includes(index)) {
+        if (index !== 0) {
+          const newElement = await this.pageBreakCallback(element, this.addedElements);
+
+          if (newElement) {
+            this.addedElements = newElement;
+          }
+        }
+      }
+    }
+    undoBtn.disabled = false;
+  }
+
+  undo() {
+    this.addedElements.forEach((element) => {
+      const nextSibling = element.nextSibling;
+
+      this.pagesContainer.removeChild(element);
+
+      if (this.pagesContainer.childElementCount === 0) {
+        const filenameInput = document.getElementById('filename-input');
+        const filenameParagraph = document.getElementById('filename');
+        const downloadBtn = document.getElementById('export-button');
+
+        filenameInput.disabled = true;
+        filenameInput.value = '';
+        filenameParagraph.innerText = '';
+        downloadBtn.disabled = true;
+      }
+
+      element._nextSibling = nextSibling;
+    });
+  }
+
+  redo() {
+    this.execute();
+  }
+}