import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";

import { createDebouncedSaver, formatSavedAt } from "./autosave";

describe("createDebouncedSaver", () => {
  beforeEach(() => vi.useFakeTimers());
  afterEach(() => vi.useRealTimers());

  it("saves only once after the debounce window for rapid edits", () => {
    const save = vi.fn().mockResolvedValue(undefined);
    const saver = createDebouncedSaver(save, 1000);
    saver.schedule("a");
    saver.schedule("ab");
    saver.schedule("abc");
    expect(save).not.toHaveBeenCalled();
    vi.advanceTimersByTime(1000);
    expect(save).toHaveBeenCalledTimes(1);
    expect(save).toHaveBeenCalledWith("abc");
  });

  it("flush triggers the pending save immediately", () => {
    const save = vi.fn().mockResolvedValue(undefined);
    const saver = createDebouncedSaver(save, 1000);
    saver.schedule("hello");
    saver.flush();
    expect(save).toHaveBeenCalledTimes(1);
    expect(save).toHaveBeenCalledWith("hello");
    // No double-fire when the timer would have elapsed.
    vi.advanceTimersByTime(1000);
    expect(save).toHaveBeenCalledTimes(1);
  });

  it("cancel prevents a scheduled save", () => {
    const save = vi.fn().mockResolvedValue(undefined);
    const saver = createDebouncedSaver(save, 1000);
    saver.schedule("x");
    saver.cancel();
    vi.advanceTimersByTime(2000);
    expect(save).not.toHaveBeenCalled();
  });

  it("each new schedule resets the timer (only last value persists)", () => {
    const save = vi.fn().mockResolvedValue(undefined);
    const saver = createDebouncedSaver(save, 1000);
    saver.schedule("one");
    vi.advanceTimersByTime(800);
    saver.schedule("two");
    vi.advanceTimersByTime(800);
    expect(save).not.toHaveBeenCalled();
    vi.advanceTimersByTime(200);
    expect(save).toHaveBeenCalledTimes(1);
    expect(save).toHaveBeenCalledWith("two");
  });
});

describe("formatSavedAt", () => {
  it("formats as 保存于 hh:mm zero-padded", () => {
    const d = new Date(2026, 5, 18, 9, 4);
    expect(formatSavedAt(d)).toBe("保存于 09:04");
  });
});