siftlode/frontend/src/lib/history.subview.dom.test.ts

// @vitest-environment jsdom
//
// useHistorySubview: a module's active sub-view rides in history.state._sub, with optional address-bar
// mirroring so a deep sub-view (Plex show/season/info/person/playlist) is bookmarkable. This backfills
// the E4 deep-review's deferred coverage for the S2 fix — the seed AND the popstate handler must share
// the SAME URL fallback, so a popstate that lands on a bookmark entry (URL-only, no _sub — e.g. after
// an overlay's programmatic history.back()) restores the sub-view from the URL instead of collapsing
// it to root. The overlay/back-ladder half of history.ts is covered in history.dom.test.ts.
import { describe, it, expect, beforeEach, afterEach, vi } from "vitest";
import { renderHook, act } from "@testing-library/react";
import { useHistorySubview, type SubviewUrl } from "./history";

// A minimal string-view mirror: "root" is the un-mirrored root (encode → null), anything else mirrors
// verbatim to ?v=<view>. decode rejects the empty string (→ null, i.e. not a valid sub-view).
const url: SubviewUrl<string> = {
  key: "v",
  encode: (v) => (v === "root" ? null : v),
  decode: (raw) => raw || null,
};

const setUrl = (search: string, state: unknown = null) =>
  window.history.replaceState(state, "", search || "/");
const popTo = (search: string, state: unknown = null) =>
  act(() => {
    window.history.replaceState(state, "", search || "/");
    window.dispatchEvent(new PopStateEvent("popstate", { state }));
  });

beforeEach(() => setUrl("/"));
afterEach(() => vi.clearAllMocks());

describe("useHistorySubview seed", () => {
  it("decodes the ?<key> URL param when the entry has no _sub (fresh bookmark)", () => {
    setUrl("?v=a");
    const { result } = renderHook(() => useHistorySubview("root", url));
    expect(result.current.view).toBe("a");
  });

  it("prefers history.state._sub over the URL param (in-app entry)", () => {
    setUrl("?v=a", { _sub: "b" });
    const { result } = renderHook(() => useHistorySubview("root", url));
    expect(result.current.view).toBe("b");
  });

  it("falls back to root when neither state nor a decodable URL param is present", () => {
    setUrl("/");
    const { result } = renderHook(() => useHistorySubview("root", url));
    expect(result.current.view).toBe("root");
  });

  it("ignores the URL entirely when no SubviewUrl is supplied (state-only mirror)", () => {
    setUrl("?v=a", { _sub: "fromState" });
    const { result } = renderHook(() => useHistorySubview("root"));
    expect(result.current.view).toBe("fromState");
    // A URL param with no url config must NOT leak in.
    setUrl("?v=a", null);
    const { result: r2 } = renderHook(() => useHistorySubview("root"));
    expect(r2.current.view).toBe("root");
  });
});

describe("useHistorySubview open", () => {
  it("pushes state._sub and mirrors the URL via encode", () => {
    const { result } = renderHook(() => useHistorySubview("root", url));
    act(() => result.current.open("a"));
    expect(result.current.view).toBe("a");
    expect(window.history.state?._sub).toBe("a");
    expect(window.location.search).toBe("?v=a");
  });

  it("clears the mirrored key when encode returns null (root/ephemeral view)", () => {
    setUrl("?v=a");
    const { result } = renderHook(() => useHistorySubview("root", url));
    act(() => result.current.open("root"));
    expect(result.current.view).toBe("root");
    expect(window.history.state?._sub).toBe("root");
    expect(window.location.search).toBe(""); // ?v dropped
  });

  // E24: a cross-module hand-off (Home plays a Plex title) arrives on an entry the page navigation
  // just pushed. Opening the sub-view on TOP of it stranded the user on a module root they never
  // visited — browser-Back from the player landed on the Plex Discover page instead of Home
  // (measured 2026-09-06). `replace` makes the sub-view BE that entry.
  it("replace rewrites the current entry instead of stacking a new one", () => {
    const before = window.history.length;
    const { result } = renderHook(() => useHistorySubview("root", url));
    act(() => result.current.open("a", { replace: true }));
    expect(result.current.view).toBe("a");
    expect(window.history.state?._sub).toBe("a");
    expect(window.location.search).toBe("?v=a");
    expect(window.history.length).toBe(before); // no new entry to Back through
  });

  it("replace is idempotent — two opens of the same view are still one entry", () => {
    // Not a nicety: under StrictMode the jumpTo effect body runs TWICE before its `setJumpTo(null)`
    // re-renders, and two pushes of the identical sub-view left a duplicate whose Back visibly did
    // nothing.
    const before = window.history.length;
    const { result } = renderHook(() => useHistorySubview("root", url));
    act(() => {
      result.current.open("a", { replace: true });
      result.current.open("a", { replace: true });
    });
    expect(window.history.length).toBe(before);
  });

  it("keeps the entry's own sfScroll id on a replace", () => {
    // It is the SAME entry, so it keeps its scroll identity; PageScroller keys offsets per
    // (entry, view), and the view key changed, so the sub-view still opens at the top.
    setUrl("/", { sfScroll: 7 });
    const { result } = renderHook(() => useHistorySubview("root", url));
    act(() => result.current.open("a", { replace: true }));
    expect(window.history.state?.sfScroll).toBe(7);
  });
});

describe("useHistorySubview popstate", () => {
  it("restores the sub-view from state._sub on Back/Forward", () => {
    const { result } = renderHook(() => useHistorySubview("root", url));
    popTo("?v=a", { _sub: "a" });
    expect(result.current.view).toBe("a");
  });

  it("restores from the ?<key> URL when the landed entry has no _sub — the S2 bookmark fix", () => {
    // Start in-app at root, then a popstate lands on a URL-only bookmark entry (no _sub). Reading
    // history.state alone would wrongly collapse to root; the shared URL fallback must decode ?v=b.
    const { result } = renderHook(() => useHistorySubview("root", url));
    expect(result.current.view).toBe("root");
    popTo("?v=b", null);
    expect(result.current.view).toBe("b");
  });

  it("collapses to root when a popstate lands on an entry with neither _sub nor a decodable URL", () => {
    setUrl("?v=a", { _sub: "a" });
    const { result } = renderHook(() => useHistorySubview("root", url));
    expect(result.current.view).toBe("a");
    popTo("/", null);
    expect(result.current.view).toBe("root");
  });
});