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]);
  });
});