tam

client/frontend/src/examViewer.js

@@ -0,0 +1,78 @@
+import * as pdfjsLib from 'pdfjs-dist/build/pdf';
+import pdfjsWorker from 'pdfjs-dist/build/pdf.worker.min.js?url';
+
+pdfjsLib.GlobalWorkerOptions.workerSrc = pdfjsWorker;
+
+function decodeBase64(b64) {
+  const bin = atob(b64);
+  const bytes = new Uint8Array(bin.length);
+  for (let i = 0; i < bin.length; i += 1) bytes[i] = bin.charCodeAt(i);
+  return bytes;
+}
+
+export function detectExamViewKind(fileName, mime, bytes) {
+  if (bytes && bytes.length >= 4) {
+    if (bytes[0] === 0x25 && bytes[1] === 0x50 && bytes[2] === 0x44 && bytes[3] === 0x46) return 'pdf';
+    if (bytes[0] === 0x89 && bytes[1] === 0x50 && bytes[2] === 0x4e && bytes[3] === 0x47) return 'image';
+    if (bytes[0] === 0xff && bytes[1] === 0xd8 && bytes[2] === 0xff) return 'image';
+    if (bytes[0] === 0x47 && bytes[1] === 0x49 && bytes[2] === 0x46) return 'image';
+  }
+  const name = String(fileName || '').toLowerCase();
+  const type = String(mime || '').toLowerCase();
+  if (type.includes('pdf') || name.endsWith('.pdf')) return 'pdf';
+  if (type.startsWith('image/') || /\.(png|jpe?g|gif|webp)$/.test(name)) return 'image';
+  if (type.startsWith('text/') || name.endsWith('.txt')) return 'text';
+  return 'unsupported';
+}
+
+export async function renderSecurePdf(container, bytes) {
+  container.innerHTML = '';
+  const pdf = await pdfjsLib.getDocument({ data: bytes }).promise;
+  const pad = 16;
+  const width = container.clientWidth || container.parentElement?.clientWidth || 900;
+  const maxWidth = Math.max(360, width - pad * 2);
+
+  for (let pageNum = 1; pageNum <= pdf.numPages; pageNum += 1) {
+    const page = await pdf.getPage(pageNum);
+    const base = page.getViewport({ scale: 1 });
+    const scale = Math.min(1.6, maxWidth / base.width);
+    const viewport = page.getViewport({ scale });
+
+    const wrap = document.createElement('div');
+    wrap.className = 'exam-pdf-page-wrap';
+    const canvas = document.createElement('canvas');
+    canvas.className = 'exam-pdf-page';
+    canvas.width = viewport.width;
+    canvas.height = viewport.height;
+    wrap.appendChild(canvas);
+    container.appendChild(wrap);
+
+    await page.render({
+      canvasContext: canvas.getContext('2d'),
+      viewport,
+    }).promise;
+  }
+}
+
+export function renderSecureImage(container, bytes, mime) {
+  container.innerHTML = '';
+  const blob = new Blob([bytes], { type: mime || 'image/png' });
+  const img = document.createElement('img');
+  img.className = 'exam-view-image';
+  img.alt = 'Tài nguyên';
+  img.draggable = false;
+  img.src = URL.createObjectURL(blob);
+  container.appendChild(img);
+}
+
+export function renderSecureText(container, bytes) {
+  container.innerHTML = '';
+  const pre = document.createElement('pre');
+  pre.className = 'exam-view-text';
+  pre.textContent = new TextDecoder('utf-8').decode(bytes);
+  container.appendChild(pre);
+}
+
+export function decodeExamFilePayload(payload) {
+  return decodeBase64(payload.data || payload);
+}