Implement reusable upload platform

upload/frontend/table/add_file_with_dedup.js

@@ -0,0 +1,27 @@
+export function addFileWithDedup(state, file, cfg) {
+  const originalName = file.name;
+  const existing = state.fileMeta.get(originalName);
+  let name = originalName;
+
+  if (existing) {
+    if (existing.size === file.size) return false;
+    const dot = originalName.lastIndexOf('.');
+    const base = dot > 0 ? originalName.slice(0, dot) : originalName;
+    const extension = dot > 0 ? originalName.slice(dot) : '';
+    let suffix = 2;
+    while (state.fileMeta.has(`${base}_${suffix}${extension}`)) suffix += 1;
+    name = `${base}_${suffix}${extension}`;
+  }
+
+  const storedFile = new File([file], name, { lastModified: file.lastModified });
+  state.fileMeta.set(name, { size: storedFile.size });
+  const includedBytes = state.files.reduce(
+    (total, item) => total + (state.overNames.has(item.name) ? 0 : item.size), 0,
+  );
+  if (storedFile.size > cfg.maxFileBytes
+      || includedBytes + storedFile.size > cfg.maxSessionBytes) {
+    state.overNames.add(name);
+  }
+  state.files.push(storedFile);
+  return true;
+}