// @vitest-environment jsdom
//
// The per-history-entry scroll-id helpers + nav bus that back PageScroller's scroll restoration:
// a fresh id per new view (so a forward navigation opens at the top), a stable id per entry (so Back
// restores it), and a bus so a sub-view open that doesn't re-render the scroller still triggers it.
import { describe, it, expect, beforeEach, vi } from "vitest";
import { nextNavId, ensureNavId, peekNavId, subscribeNav, notifyNav } from "./history";

beforeEach(() => {
  window.history.replaceState(null, "");
});

describe("nav scroll ids", () => {
  it("nextNavId hands out strictly increasing ids", () => {
    const a = nextNavId();
    const b = nextNavId();
    expect(b).toBeGreaterThan(a);
  });

  it("ensureNavId assigns an id to a stateless entry, then is idempotent", () => {
    expect(peekNavId()).toBe(0); // no id yet
    const id = ensureNavId();
    expect(id).toBeGreaterThan(0);
    expect(peekNavId()).toBe(id);
    expect(ensureNavId()).toBe(id); // does not reassign
    expect((window.history.state as { sfScroll?: number }).sfScroll).toBe(id);
  });

  it("ensureNavId preserves other history.state keys", () => {
    window.history.replaceState({ sfPage: "plex" }, "");
    ensureNavId();
    expect((window.history.state as { sfPage?: string }).sfPage).toBe("plex");
  });

  it("a pushed entry keeps its own id (so Back restores the right one)", () => {
    const first = ensureNavId();
    window.history.pushState({ sfScroll: nextNavId() }, "");
    const second = peekNavId();
    expect(second).not.toBe(first);
    window.history.back();
    // jsdom doesn't truly pop synchronously, but the ids are distinct per entry — the invariant we need.
    expect(second).toBeGreaterThan(first);
  });

  it("ensureNavId advances the counter past a higher persisted id (post-reload collision guard)", () => {
    // After a full reload the module counter resets to 0 while sfScroll ids persist in history.state.
    // Landing on an entry whose id is above the counter must push the counter past it, so the next
    // minted id can't duplicate a live back-stack entry and mis-restore its scroll.
    const high = 999999;
    window.history.replaceState({ sfScroll: high }, "");
    expect(ensureNavId()).toBe(high); // returns the persisted id, doesn't reassign
    expect(nextNavId()).toBeGreaterThan(high); // and the next mint clears it
  });

  it("notifyNav fires subscribers until they unsubscribe", () => {
    const cb = vi.fn();
    const unsub = subscribeNav(cb);
    notifyNav();
    expect(cb).toHaveBeenCalledTimes(1);
    notifyNav();
    expect(cb).toHaveBeenCalledTimes(2);
    unsub();
    notifyNav();
    expect(cb).toHaveBeenCalledTimes(2);
  });
});