"""U3 — the declared embed seam, in a real DOM.

The Python suite can prove what the server OFFERS. It cannot prove where a
fragment lands, whether the author's own markup survived the mount, or whether
four radio groups scattered down a report still submit as one POST — and that
last one is the operator's most important workflow. Before U3 those properties
were true by construction, because the server did the placing and the `form=`
bindings were static by the time the page was parsed. Now they are true because
`/_booth/embed.js` does it in a live document, which is a different kind of
claim and needs a different kind of test.

So: a real uvicorn on an ephemeral port, a real Chromium.

SKIPS, NEVER FAILS, when playwright or the shared browser is unavailable. The
box-wide store at /opt/ms-playwright pins specific Chromium revisions and a
playwright release that wants a newer one dies with an opaque "Executable
doesn't exist" — see pyproject's version bound. A test layer that goes red for
an environment reason teaches nothing and trains people to ignore it.
"""
import json
import socket
import threading
import time

import pytest

from booth.app import create_app

playwright_api = pytest.importorskip(
    "playwright.sync_api", reason="playwright is not installed"
)


@pytest.fixture(scope="module")
def browser():
    with playwright_api.sync_playwright() as pw:
        try:
            b = pw.chromium.launch()
        except Exception as exc:  # noqa: BLE001 - any launch failure is a skip
            pytest.skip(f"no usable chromium: {exc}")
        yield b
        b.close()


@pytest.fixture
def live(tmp_path):
    """A real server, because a browser cannot talk to a TestClient."""
    import uvicorn

    sock = socket.socket()
    sock.bind(("127.0.0.1", 0))
    port = sock.getsockname()[1]
    # ⚠ THE SOCKET IS HANDED TO UVICORN STILL BOUND, never closed and
    # re-opened by port number. The old form did bind -> getsockname -> CLOSE ->
    # tell uvicorn the number, which leaves a window where the kernel can give
    # that port to somebody else — and this suite runs TWO browser files that
    # each start a server per test, so the other one is right there competing
    # for it. Passing the live socket removes the window rather than narrowing
    # it.
    #
    # Honest about the evidence: two different browser tests failed once each
    # across full-suite runs while passing 3/3 and 5/5 on their own, which is
    # the signature of contention. We cannot prove from two samples that this
    # race was the cause. It is a real defect either way, and it is the only
    # one visible in the harness.


    app = create_app(tmp_path, ttl_hours=24, start_sweeper=False)
    config = uvicorn.Config(app, host="127.0.0.1", port=port, log_level="error")
    server = uvicorn.Server(config)
    thread = threading.Thread(target=lambda: server.run(sockets=[sock]), daemon=True)
    thread.start()
    deadline = time.time() + 10
    while not server.started and time.time() < deadline:
        time.sleep(0.02)
    if not server.started:
        pytest.skip("uvicorn did not come up")
    try:
        yield f"http://127.0.0.1:{port}", tmp_path
    finally:
        server.should_exit = True
        thread.join(timeout=10)


PNG = b"\x89PNG\r\n\x1a\n"
SEAM = '<script src="/_booth/embed.js" defer></script>'


def _multi(booth):
    from booth.marks import declare_pick

    booth.mkdir(parents=True, exist_ok=True)
    declare_pick(booth, "batch", {"title": "Round one", "questions": [
        {"key": "r1", "prompt": "First?", "options": ["keep", "cut"]},
        {"key": "r2", "prompt": "Second?", "options": ["keep", "cut"]},
    ]})
    return booth


def _single(booth):
    from booth.marks import declare_pick

    booth.mkdir(parents=True, exist_ok=True)
    declare_pick(booth, "winner", {"prompt": "Which render wins?",
                                   "options": ["A — baseline", "B — async"]})
    return booth


def _open(browser, base, name, html, booth):
    (booth / "index.html").write_text(html, encoding="utf-8")
    page = browser.new_page()
    page.goto(f"{base}/b/{name}/", wait_until="networkidle")
    return page


def _answer(booth):
    raw = json.loads((booth / ".marks.json").read_text())
    return raw["marks"][0].get("answer")


# ---- the chrome --------------------------------------------------------------


def test_a_declaring_page_gets_its_chrome_mounted(browser, live):
    base, data = live
    b = _single(data / "b")
    page = _open(browser, base, "b", f"<!doctype html><title>r</title><body><h1>R</h1>{SEAM}</body>", b)
    page.wait_for_selector(".booth-nav-home")
    assert page.locator("h1").inner_text() == "R"            # the report is intact
    assert page.locator(".booth-nav-home").get_attribute("href").endswith("/")
    # the favicon question, asked of a parsed document instead of raw text
    assert page.locator('link[rel="icon"]').count() == 1
    page.close()


def test_a_page_that_never_declared_the_seam_still_mounts(browser, live):
    """The appended path: every verbatim booth that predates U3 keeps working
    without its author touching it."""
    base, data = live
    b = _single(data / "b")
    page = _open(browser, base, "b", "<!doctype html><body><h1>OLD</h1></body>", b)
    page.wait_for_selector(".bk-ask")
    assert page.locator("h1").inner_text() == "OLD"
    assert page.locator(".booth-nav-home").count() == 1
    page.close()


def test_a_page_that_declares_its_own_icon_keeps_it(browser, live):
    base, data = live
    b = _single(data / "b")
    page = _open(
        browser, base, "b",
        f'<!doctype html><head><link rel="icon" href="data:image/png;base64,AAAA">'
        f"</head><body>x{SEAM}</body>", b)
    page.wait_for_selector(".booth-nav-home")
    icons = page.locator('link[rel="icon"]')
    assert icons.count() == 1
    assert icons.get_attribute("href").startswith("data:image/png")
    page.close()


# ---- placement ---------------------------------------------------------------


REPORT = f"""<!doctype html><title>audition</title><body>
<h1>Three voices</h1>
<section id="lawson"><audio src="a.wav"></audio>
<div data-booth-ask="batch:r1"></div></section>
<section id="jo"><audio src="b.wav"></audio>
<div data-booth-mark="batch:r2"></div></section>
<div data-booth-ask-submit="batch"></div>
{SEAM}
</body>"""


def test_each_question_lands_where_the_author_put_it(browser, live):
    """The 2026-09-09 ruling, enforced in the DOM: the question for a voice sits
    under that voice, not on another page and not in a pile at the end. Both
    attribute spellings, because live reports use the older one."""
    base, data = live
    b = _multi(data / "b")
    page = _open(browser, base, "b", REPORT, b)
    page.wait_for_selector("#lawson .bk-ask")
    assert page.locator('#lawson input[name="choice.r1"]').count() == 2
    assert page.locator('#jo input[name="choice.r2"]').count() == 2
    # nothing spilled to the end of the body: every piece had an anchor
    assert page.locator("body > .bk-ask").count() == 0
    assert page.locator("form#bk-ask-form-batch").count() == 1
    page.close()


def test_the_authors_wrapper_and_its_contents_survive_the_mount(browser, live):
    """The live `dfa-concepts` shape — a non-empty styled wrapper carrying the
    anchor attribute. The regex this replaced matched the opening tag and
    SUBSTITUTED it, eating the class and orphaning the heading. beforeend keeps
    both and puts the radios under the heading, which is what the markup says."""
    base, data = live
    b = _multi(data / "b")
    page = _open(browser, base, "b", (
        '<!doctype html><body><div class="ask" data-booth-ask="batch:r1">'
        f"<h3>The one asset that must survive</h3></div>{SEAM}</body>"), b)
    page.wait_for_selector(".ask .bk-ask")
    assert page.locator("div.ask").count() == 1                       # class kept
    assert page.locator(".ask h3").inner_text() == "The one asset that must survive"
    assert page.locator('.ask input[name="choice.r1"]').count() == 2  # radios inside
    page.close()


def test_an_unplaced_question_is_appended_and_so_is_its_submit(browser, live):
    """INV-7. A multi-question pick needs EVERY question on submit or the POST is
    unanswerable: a question that never reaches the page cannot be picked, and
    a submission with nothing picked at all is refused outright."""
    base, data = live
    b = _multi(data / "b")
    page = _open(browser, base, "b",
                 f'<!doctype html><body><div data-booth-mark="batch:r1"></div>{SEAM}</body>', b)
    # attached, not visible: the shared <form> is deliberately empty and so has
    # no box — the controls that bind to it are what the operator sees.
    page.wait_for_selector("form#bk-ask-form-batch", state="attached")
    # BOTH halves. Asserting only the appended r2 let a mutation that silently
    # swallowed the anchored r1 — while still recording it as placed — pass.
    assert page.locator('input[name="choice.r1"]').count() == 2   # anchored, mounted
    assert page.locator('input[name="choice.r2"]').count() == 2   # unplaced, appended
    assert page.locator("form#bk-ask-form-batch").count() == 1    # submittable
    page.close()


def test_a_page_with_no_anchors_gets_the_whole_ask(browser, live):
    base, data = live
    b = _multi(data / "b")
    page = _open(browser, base, "b", f"<!doctype html><body><p>x</p>{SEAM}</body>", b)
    page.wait_for_selector(".bk-ask")
    assert page.locator('input[name="choice.r1"]').count() == 2
    assert page.locator('input[name="choice.r2"]').count() == 2
    page.close()


def test_an_anchor_naming_no_mark_is_left_alone(browser, live):
    """A typo'd id stays visible as the author's own empty element rather than
    being blanked — and the real ask is still never lost."""
    base, data = live
    b = _multi(data / "b")
    page = _open(browser, base, "b",
                 f'<!doctype html><body><div id="t" data-booth-mark="typo"></div>{SEAM}</body>', b)
    page.wait_for_selector(".bk-ask")
    assert page.locator("#t").inner_html().strip() == ""
    assert page.locator('input[name="choice.r1"]').count() == 2
    page.close()


def test_the_tail_follows_payload_order(browser, live):
    """INV-6. Creation order and alphabetical order DISAGREE here on purpose:
    `winner` is created first, `batch` second, so payload order is
    winner-then-batch while an id sort would give the reverse. The first version
    of this fixture made the two identical, so sorting the tail alphabetically
    in JavaScript passed it — caught by a panel reading the fixture."""
    base, data = live
    b = _single(data / "b")
    _multi(b)
    raw = json.loads((b / ".marks.json").read_text())
    stamps = {"winner": "2026-09-22T10:00:00.000000-07:00",   # first
              "batch": "2026-09-22T11:00:00.000000-07:00"}    # second
    for e in raw["marks"]:
        e["created"] = stamps[e["id"]]
    (b / ".marks.json").write_text(json.dumps(raw))
    page = _open(browser, base, "b", f"<!doctype html><body>{SEAM}</body>", b)
    page.wait_for_selector(".bk-ask")
    ids = page.eval_on_selector_all("[id^='bk-ask-']", "els => els.map(e => e.id)")
    batch = [i for i, v in enumerate(ids) if "batch" in v]
    winner = [i for i, v in enumerate(ids) if "winner" in v]
    assert batch and winner, ids
    # winner (created first) ahead of batch (created second) — the OPPOSITE of
    # alphabetical, so an id sort cannot pass this.
    assert max(winner) < min(batch), ids
    page.close()


# ---- the one that actually matters ------------------------------------------


def test_a_form_scattered_down_the_report_submits_every_question(browser, live):
    """THE load-bearing browser test.

    Four radio groups under four different artifacts, one <form> somewhere else
    entirely, bound only by the HTML5 `form=` attribute — and now inserted into
    a live document in visual order, which means a control can land before the
    form it points at. If form-owner resolution does not survive that, the
    operator fills the whole thing in and the button saves nothing.

    It was true by construction before U3 (static HTML, resolved at parse). It
    is true by measurement now. That is the trade this test pays for.
    """
    base, data = live
    b = _multi(data / "b")
    page = _open(browser, base, "b", REPORT, b)
    page.wait_for_selector("#lawson .bk-ask")
    page.check('#lawson input[name="choice.r1"][value="keep"]')
    page.check('#jo input[name="choice.r2"][value="cut"]')
    with page.expect_navigation():
        page.click("button.bk-ask-go")
    ans = _answer(b)
    assert ans is not None, "the scattered form submitted nothing"
    assert ans["answers"]["r1"]["choice"] == "keep"
    assert ans["answers"]["r2"]["choice"] == "cut", \
        "a question bound by form= did not reach the POST"
    assert ans["complete"] is True
    page.close()


def test_the_chip_jumps_to_the_first_fragment_of_the_open_ask(browser, live):
    base, data = live
    b = _multi(data / "b")
    page = _open(browser, base, "b", REPORT, b)
    page.wait_for_selector(".booth-nav-asks")
    chip = page.locator(".booth-nav-asks")
    assert chip.inner_text() == "? 1 open ask"
    target = chip.get_attribute("href")
    # the EARLIEST match in document order, not merely a match: the report
    # anchors r1 above r2 above the submit block, so any later one is wrong.
    ids = page.eval_on_selector_all("[id^='bk-ask-batch']", "els => els.map(e => e.id)")
    assert ids, "no batch fragment mounted"
    assert target == "#" + ids[0], (target, ids)
    page.close()


def test_an_anchor_named_like_an_object_property_does_not_kill_the_page(browser, live):
    """`toString` is a legal mark id (`asks.valid_stem`) and therefore a legal
    thing for an author to typo into an anchor. Against a plain `{}` lookup it
    came back as Object.prototype.toString — truthy, so it sailed past the
    unknown-mark guard and threw on `.questions.length`, aborting placement
    before the tail and costing the page EVERY ask. One typo, no chrome, no
    error the operator would see. Found by a cross-frontier panel."""
    base, data = live
    b = _multi(data / "b")
    page = _open(browser, base, "b", (
        '<!doctype html><body><div id="t" data-booth-mark="toString"></div>'
        f'<div id="v" data-booth-mark="valueOf:r1"></div>{SEAM}</body>'), b)
    page.wait_for_selector(".bk-ask")
    assert page.locator("#t").inner_html().strip() == ""      # left alone
    assert page.locator("#v").inner_html().strip() == ""      # left alone
    # and the real ask still mounted, which is what the bug destroyed
    assert page.locator('input[name="choice.r1"]').count() == 2
    assert page.locator('input[name="choice.r2"]').count() == 2
    assert page.locator("form#bk-ask-form-batch").count() == 1
    page.close()


def test_a_question_keyed_like_an_object_property_is_not_swallowed(browser, live):
    """The mirror of the same bug, on the `placed` set. `constructor` matches
    `asks._KEY_RE`, and against a plain object an inherited `got.constructor`
    read as ALREADY PLACED — so a question the author did not anchor was
    silently dropped from the tail, which is INV-7's whole subject."""
    from booth.marks import declare_pick

    base, data = live
    b = data / "b"
    b.mkdir(parents=True, exist_ok=True)
    declare_pick(b, "batch", {"title": "Round one", "questions": [
        {"key": "r1", "prompt": "First?", "options": ["keep", "cut"]},
        {"key": "constructor", "prompt": "Second?", "options": ["keep", "cut"]},
    ]})
    page = _open(browser, base, "b",
                 f'<!doctype html><body><div data-booth-mark="batch:r1"></div>{SEAM}</body>', b)
    page.wait_for_selector("form#bk-ask-form-batch", state="attached")
    assert page.locator('input[name="choice.r1"]').count() == 2
    assert page.locator('input[name="choice.constructor"]').count() == 2, \
        "an unplaced question was swallowed by an inherited property"
    page.close()


def test_a_submit_anchor_inside_the_authors_own_form_still_submits(browser, live):
    """A submit anchor placed inside the author's own `<form>` loses ours: the
    HTML parser drops a nested form element outright. The controls' `form=`
    then points at nothing, the button does nothing, and the operator finds out
    by filling the whole thing in. Found by a cross-frontier bug-hunt panel; the
    fix is to count the anchor submitted only if the form actually survived, so
    the tail supplies one at body level where no form encloses it."""
    base, data = live
    b = _multi(data / "b")
    page = _open(browser, base, "b", (
        '<!doctype html><body>'
        '<div data-booth-mark="batch:r1"></div>'
        '<div data-booth-mark="batch:r2"></div>'
        '<form id="mine" action="/elsewhere">'
        '<div data-booth-ask-submit="batch"></div></form>'
        f"{SEAM}</body>"), b)
    page.wait_for_selector("form#bk-ask-form-batch", state="attached")
    assert page.locator("form#bk-ask-form-batch").count() == 1
    page.check('input[name="choice.r1"][value="keep"]')
    page.check('input[name="choice.r2"][value="cut"]')
    with page.expect_navigation():
        page.click("button.bk-ask-go")
    ans = _answer(b)
    assert ans is not None, "the button reached no form"
    assert ans["answers"]["r1"]["choice"] == "keep"
    assert ans["answers"]["r2"]["choice"] == "cut"
    page.close()


def test_a_broken_pick_shows_its_diagnostic_even_from_a_submit_anchor(browser, live):
    """A broken pick has no submit block — its `submit` is empty and the
    diagnostic lives in `whole`. Mounting that empty string and then recording
    the pick as placed made the tail skip it, so the 'broken ask' box never
    rendered at the one surface built to show it. A question the session
    believes it posted has to be visible."""
    base, data = live
    b = _single(data / "b")
    raw = json.loads((b / ".marks.json").read_text())
    raw["marks"][0]["declaration"] = {"prompt": "p"}      # no options -> AskError
    (b / ".marks.json").write_text(json.dumps(raw))
    page = _open(browser, base, "b",
                 f'<!doctype html><body><div id="s" data-booth-ask-submit="winner">'
                 f"</div>{SEAM}</body>", b)
    page.wait_for_selector(".bk-ask")
    assert page.locator("#s").inner_html().strip() == ""     # anchor left alone
    # inner_text() is the RENDERED text, and `.bk-ask-tag` is uppercased by CSS —
    # so assert the diagnostic itself, which is the part that has to reach him.
    shown = page.locator("body").inner_text()
    assert "this question could not be read" in shown, shown
    assert "options" in shown                                # the actual reason
    page.close()


def test_an_author_element_cannot_hijack_the_chip(browser, live):
    """`<section id="bk-ask-winner-background">` satisfies any id-prefix rule,
    hyphen boundary included. The chip therefore searches only the elements THIS
    SCRIPT MOUNTED — the identity the deleted `bk-ask-<id>-top` anchor used to
    guarantee — and takes the earliest of those in document order."""
    base, data = live
    b = _single(data / "b")
    page = _open(browser, base, "b", (
        '<!doctype html><body><section id="bk-ask-winner-background">notes</section>'
        f"<p>report</p>{SEAM}</body>"), b)
    page.wait_for_selector(".booth-nav-asks")
    target = page.locator(".booth-nav-asks").get_attribute("href")
    assert target != "#bk-ask-winner-background"
    landed = page.locator(target)
    assert landed.count() == 1
    assert landed.evaluate("e => e.classList.contains('bk-ask')"), \
        "the chip jumped to something the Booth did not mount"
    page.close()


def test_the_chip_does_not_jump_to_a_mark_that_merely_shares_a_prefix(browser, live):
    """A SIBLING MARK's fragment must not take the chip, even when it is earlier
    in the document. `batch2`'s id starts with `batch`, so the original
    id-prefix rule could land on it; the mounted-elements rule cannot, because
    the candidates are partitioned by mark.

    ⚠ The first version of this test put the sibling's fragment AFTER the open
    mark's, so the right answer was also the first answer and pooling every
    mark's elements passed it. The vacuity pass caught that; the fixture now
    puts the sibling FIRST, which is the only arrangement that can tell the two
    implementations apart.
    """
    from booth.marks import declare_pick

    base, data = live
    b = _multi(data / "b")                       # `batch`, created first
    declare_pick(b, "batch2", {"prompt": "Unrelated?", "options": ["x", "y"]})

    # batch2 is anchored at the very top; batch is unanchored and so lands in
    # the tail, at the END of the body. Document order is therefore batch2's
    # fragments, then batch's.
    page = _open(browser, base, "b", (
        '<!doctype html><body><div data-booth-mark="batch2"></div>'
        f"<p>report</p>{SEAM}</body>"), b)
    page.wait_for_selector(".booth-nav-asks")

    ids = page.eval_on_selector_all("[id^='bk-ask-']", "els => els.map(e => e.id)")
    assert any("batch2" in i for i in ids) and any(
        "batch2" not in i and "batch" in i for i in ids), ids
    assert ids.index(next(i for i in ids if "batch2" in i)) < \
        ids.index(next(i for i in ids if "batch2" not in i and "batch" in i)), \
        f"fixture is wrong: the sibling must come FIRST, got {ids}"

    # `open` is (created, id) -> batch before batch2, so the chip targets batch
    target = page.locator(".booth-nav-asks").get_attribute("href")
    assert "batch2" not in target, f"the chip landed on the sibling mark: {target}"
    assert target.startswith("#bk-ask-batch")
    assert page.locator(target).count() == 1
    page.close()


def test_the_canonical_attribute_wins_when_both_are_present(browser, live):
    """`data-booth-mark` is canonical and `data-booth-ask` is the kept alias.
    An element carrying both is not a case any live report has, but the
    precedence has to be decided somewhere rather than by selector order."""
    base, data = live
    b = _multi(data / "b")
    page = _open(browser, base, "b", (
        '<!doctype html><body><div id="a" data-booth-mark="batch:r2" '
        f'data-booth-ask="batch:r1"></div>{SEAM}</body>'), b)
    page.wait_for_selector("#a .bk-ask")
    assert page.locator('#a input[name="choice.r2"]').count() == 2   # canonical
    assert page.locator('#a input[name="choice.r1"]').count() == 0   # alias ignored
    # r1 was never placed, so INV-7 still puts it somewhere
    assert page.locator('input[name="choice.r1"]').count() == 2
    page.close()


def test_the_chip_count_comes_from_the_server(browser, live):
    """INV-4. A half-answered multi-question pick is STILL OPEN, and the page
    does not get to have an opinion about that — `open_marks` decides."""
    from booth.marks import answer_pick

    base, data = live
    b = _multi(data / "b")
    answer_pick(b, "batch", {"r1": "keep"})
    page = _open(browser, base, "b", REPORT, b)
    page.wait_for_selector(".bk-ask")
    assert page.locator(".booth-nav-asks").count() == 1
    answer_pick(b, "batch", {"r1": "keep", "r2": "cut"})
    page.reload(wait_until="networkidle")
    page.wait_for_selector(".bk-ask")
    assert page.locator(".booth-nav-asks").count() == 0
    page.close()


def test_the_chip_follows_a_payload_that_disagrees_with_the_fragments(browser, live):
    """INV-4, and the version that actually falsifies it.

    The test above uses honest fixtures, so a client that INFERRED openness from
    the rendered fragments would pass it — the fragments and `open` always agree
    when the server computes both. A panel pointed out that this never creates
    the disagreement it claims to test.

    So: intercept the response and make `open` lie. The fragments say fully
    answered; the payload says two are open. The chip must follow the payload,
    because the payload is the only thing that decides.
    """
    import json as _json

    from booth.marks import answer_pick

    base, data = live
    b = _multi(data / "b")
    answer_pick(b, "batch", {"r1": "keep", "r2": "cut"})   # nothing is open
    (b / "index.html").write_text(f"<!doctype html><body>{SEAM}</body>", encoding="utf-8")

    def lie(route):
        body = _json.loads(route.fetch().text())
        assert body["open"] == [], "fixture is not answered; the lie would be true"
        body["open"] = ["batch", "batch"]
        route.fulfill(status=200, content_type="application/json",
                      body=_json.dumps(body))

    page = browser.new_page()
    page.route("**/embed.json", lie)
    page.goto(f"{base}/b/b/", wait_until="networkidle")
    page.wait_for_selector(".booth-nav-asks")
    assert page.locator(".booth-nav-asks").inner_text() == "? 2 open asks"
    page.close()


# --- the grid keyboard, which is the OTHER thing no string assertion sees ----
# Added 2026-09-22 after the heid bug-hunt panel found a defect whose entire
# expression is viewport geometry: a group jump moves the scroll position, the
# keyboard cursor does not know, and the next arrow key scrolls back.


def _gallery(root, name="g"):
    """Enough tiles that the grid must scroll, in two groups."""
    b = root / name
    b.mkdir()
    for i in range(1, 13):
        (b / f"aa{i:02d}.png").write_bytes(PNG)
    for i in range(1, 13):
        (b / f"zz{i:02d}.png").write_bytes(PNG)
    return b


def test_an_arrow_after_a_group_jump_does_not_scroll_back(browser, live):
    """GRÓA's solo. The jump scrolled the viewport but left the cursor at -1,
    so the next ArrowRight focused tile 0 and `scrollIntoView` yanked the page
    back to the top — silently reversing the jump the operator just made.

    The whole failure is geometry, so it is asserted on geometry: scroll
    position after the arrow must stay near where the jump landed, not return
    to the top. Defeating change: `focus(at + 1)` with `at` starting at -1."""
    base, root = live
    _gallery(root)
    page = browser.new_page()
    page.set_viewport_size({"width": 900, "height": 600})
    page.goto(f"{base}/b/g/", wait_until="networkidle")

    page.click('.rail-g[data-group="zz"]')
    page.wait_for_timeout(250)
    after_jump = page.evaluate("window.scrollY")
    assert after_jump > 0, "the group jump did not scroll at all"

    page.keyboard.press("ArrowRight")
    page.wait_for_timeout(250)
    after_key = page.evaluate("window.scrollY")
    page.close()

    assert after_key > after_jump / 2, (
        f"the arrow key undid the jump: scrollY {after_jump} -> {after_key}"
    )


def test_the_keyboard_flag_actually_submits(browser, live):
    """HULDA's solo. `f` selected `.flagbtn, [name="target"]`; nothing in this
    repo emits `.flagbtn`, so it clicked the HIDDEN target input — and clicking
    a hidden input does not submit its form. The shortcut never worked while
    still swallowing the keystroke.

    Asserted end to end: press f, and the flag must come back from the server.

    R2 C3 (docs/contracts/r2_flow.contract.md, "Assertions that change"): this
    used to expect a NAVIGATION — the flag form POSTed, 303'd and reloaded. That
    was the no-JS design working, not a defect, and it still is with scripts
    off (tests/golden/r2_mark_303.json replays those responses byte for byte).
    What changed is that WITH JS ON the flag now applies in place. The claim
    that matters is kept and tightened: the flag must come back from the SERVER
    (the swapped tile is server-rendered), and a marker set on the window before
    the keypress must survive, which a reload would wipe."""
    base, root = live
    _gallery(root)
    page = browser.new_page()
    page.goto(f"{base}/b/g/", wait_until="networkidle")
    page.evaluate("window.__noReload = 1")

    page.keyboard.press("ArrowRight")
    # ⚠ WAIT FOR THE CURSOR TO LAND BEFORE PRESSING `f`. Firing both keys
    # back to back assumed the first had finished, and `focus()` does a
    # `scrollIntoView` — so under full-suite load `f` could arrive with no
    # cursor set and flag nothing. It failed once in roughly five whole-suite
    # runs while passing 3/3 on its own, which is the signature of a race
    # rather than a defect, and a test that goes red one time in five trains
    # people to ignore red.
    page.wait_for_selector("figure.item.is-cursor", timeout=10000)
    page.keyboard.press("f")
    page.wait_for_selector("figure.item.is-flagged", timeout=10000)
    flagged = page.locator("figure.item.is-flagged").count()
    survived = page.evaluate("window.__noReload === 1")
    page.close()

    assert flagged == 1, f"the f key flagged {flagged} items, expected 1"
    assert survived, "the flag reloaded the page; in-place judgment must not"