feat: convert file manager into a plugin

plugins/file-manager/tests/frontend/file-manager-utils.test.ts

@@ -0,0 +1,53 @@
+import { describe, it, expect } from "vitest";
+import {
+  formatFileSize,
+  runWithConcurrency,
+} from "../../src/frontend/file-manager-utils.js";
+
+describe("formatFileSize", () => {
+  it("returns a dash for undefined or null", () => {
+    expect(formatFileSize(undefined)).toBe("-");
+    expect(formatFileSize(null as unknown as number)).toBe("-");
+  });
+
+  it("returns 0 B for zero", () => {
+    expect(formatFileSize(0)).toBe("0 B");
+  });
+
+  it("formats bytes without decimals", () => {
+    expect(formatFileSize(512)).toBe("512 B");
+    expect(formatFileSize(1023)).toBe("1023 B");
+  });
+
+  it("formats kilobytes with one decimal under 10", () => {
+    expect(formatFileSize(1024)).toBe("1.0 KB");
+    expect(formatFileSize(1536)).toBe("1.5 KB");
+  });
+
+  it("rounds to whole numbers at or above 10 units", () => {
+    expect(formatFileSize(10 * 1024)).toBe("10 KB");
+    expect(formatFileSize(1024 * 1024)).toBe("1.0 MB");
+  });
+
+  it("scales up to larger units", () => {
+    expect(formatFileSize(1024 * 1024 * 1024)).toBe("1.0 GB");
+    expect(formatFileSize(1024 * 1024 * 1024 * 1024)).toBe("1.0 TB");
+  });
+
+  it("limits concurrent work", async () => {
+    let active = 0;
+    let maxActive = 0;
+    const completed: number[] = [];
+
+    await runWithConcurrency([1, 2, 3, 4, 5], 2, async (item) => {
+      active += 1;
+      maxActive = Math.max(maxActive, active);
+      await new Promise((resolve) => setTimeout(resolve, 1));
+      completed.push(item);
+      active -= 1;
+    });
+
+    expect(maxActive).toBe(2);
+    expect(completed.sort()).toEqual([1, 2, 3, 4, 5]);
+  });
+});