"""Unit: the phase-109 never-frozen-turn frontend contract (tasks
01-02), updated by phase 158 (task 02).

No new Python app logic exists for this task — the behavior lives in
``frontend/assets/app.js`` and is E2E-gated by the story suite (task 03).
Like the other frontend-adjacent unit files (the house
read-the-assets-as-text pattern, cf. ``test_frontend_tool_states.py``),
this module pins the JS markers the phase depends on: the phase-109
D15 re-open pin is REPLACED by the phase-158 per-run contract (owner
direction 2026-10-04 — ``thinking`` frames open a NEW block per
contiguous run, ``delta`` frames fold the active run, a later
thinking frame opens a NEW run, not a re-open) — while the
phase-14 restore path and the phase-17 follow-the-tail pin logic stay
byte-for-byte untouched (the capture moves verbatim, per block).
Task 02 (phase 109) pins the persistent in-turn loader (D16): the
static ``#turn-loader`` markup, ``setUiState`` as its SOLE visibility
owner (the structural never-stale guarantee), and the CSS contract
(reused typing-dot animation + reduced-motion + provenance).
"""
from __future__ import annotations

import re
from pathlib import Path

FRONTEND = Path(__file__).resolve().parents[2] / "frontend"
APP_JS = FRONTEND / "assets" / "app.js"
INDEX_HTML = FRONTEND / "index.html"
STYLES_CSS = FRONTEND / "assets" / "styles.css"


def _js() -> str:
    return APP_JS.read_text(encoding="utf-8")


def _html() -> str:
    return INDEX_HTML.read_text(encoding="utf-8")


def _css() -> str:
    return STYLES_CSS.read_text(encoding="utf-8")


def _thinking_branch() -> str:
    """The `thinking` handler branch (between the thinking and tool
    branches of the turn dispatch)."""
    js = _js()
    thinking_idx = js.find('ev.type === "thinking"')
    tool_idx = js.find('ev.type === "tool"')
    assert -1 < thinking_idx < tool_idx, (
        "the turn handler must branch on thinking frames"
    )
    return js[thinking_idx:tool_idx]


def test_thinking_handler_opens_a_new_block_per_run() -> None:
    """Phase 158 (D1 — the phase-109 D15 re-open pin, replaced by
    owner direction 2026-10-04): the `thinking` handler opens a NEW
    block per contiguous run — ``ensureThinkingRun(wrap)`` sits in the
    handler (a frame of a new kind closes the previous run and opens
    a new block), the RUN's text accumulates + re-renders into THAT
    block, and the D15 re-open assignment (``block.open = true``) is
    GONE from the branch — the open state is owned by the builder
    (a new run opens; the active run stays open)."""
    branch = _thinking_branch()
    ensure_idx = branch.find("ensureThinkingRun(wrap)")
    assert ensure_idx != -1, (
        "the handler must open/extend the run's block (D1: per-run — "
        "a new kind opens a NEW block)"
    )
    assert "currentRun.run.text += ev.text || \"\"" in branch, (
        "the RUN's text accumulates (the block renders the run, not "
        "the whole-turn accumulator)"
    )
    assert "block.open = true" not in branch, (
        "the D15 re-open assignment is GONE — ensureThinkingRun owns "
        "the open state"
    )


def test_delta_handler_folds_the_active_run() -> None:
    """Phase 158 (D5 — the phase-109 D15 close-side pin, updated):
    the close side of the per-run contract — the `delta` handler calls
    ``closeCurrentRun()`` (folds the active run, idempotent); a later
    thinking frame opens a NEW run above the bubble (the D15 re-open
    of the shared block is gone)."""
    js = _js()
    delta_idx = js.find('ev.type === "delta"')
    done_idx = js.find('ev.type === "done"')
    assert -1 < delta_idx < done_idx, "the turn handler must branch on delta"
    branch = js[delta_idx:done_idx]
    assert "closeCurrentRun()" in branch, (
        "the `delta` handler must fold the active run (D5: "
        "folded-while-answering)"
    )


def test_section_comment_says_per_run_not_reopen() -> None:
    """Phase 158 (D1 — the phase-109 D15 narrative, replaced): the
    section comment documenting the run builders no longer claims the
    D15 toggle contract (the "re-opens" narrative is gone — nowhere
    in app.js does "never reopens" survive either) — it names the
    per-run timeline instead: each CONTIGUOUS run its own block,
    arrival order, D2 placement, and the D15 contract as replaced."""
    js = _js()
    assert "never reopens" not in js, (
        "the one-way-door narrative must not survive anywhere in app.js"
    )
    # The block comment that documents the builders: walk back from
    # the first builder to its section comment start.
    comment_start = js.rfind("/*", 0, js.find("function createThinkingBlock"))
    assert comment_start != -1
    section = js[comment_start : js.find("function createThinkingBlock")]
    assert "re-opens" not in section, (
        "the D15 re-open narrative is gone (phase 158, D1)"
    )
    assert "PER-RUN" in section or "per-run" in section, (
        "the contract is named: per-run"
    )
    assert "CONTIGUOUS" in section, "a contiguous run per block is named"
    assert "arrival order" in section, "D2: arrival order is named"
    assert "REPLACED" in section or "superseded" in section.lower(), (
        "the D15 contract is named as replaced"
    )


def test_restore_path_still_collapses_stored_blocks() -> None:
    """Phase-14 contract regression: ``renderStoredMessage`` restores
    stored thinking blocks COLLAPSED (``block.open = false`` — the
    shared ``createThinkingBlock`` builder, phase 158 task 02) — the
    phase-158 per-run live path never opens a restored block."""
    js = _js()
    fn = js.find("function renderStoredMessage")
    assert fn != -1, "renderStoredMessage must exist"
    body = js[fn : js.find("\n}\n", fn)]
    assert "if (m.thinking)" in body
    assert "createThinkingBlock()" in body
    assert "block.open = false" in body, "stored blocks restore collapsed"
    # The live re-open must NOT have leaked into the restore path:
    # only the collapse assignment may appear in the function body.
    assert "block.open = true" not in body, (
        "the restore path must never open a stored block (phase-14)"
    )


def test_follow_the_tail_pin_logic_is_untouched() -> None:
    """Cross-file regression (phase 17): the follow-the-tail pin is
    unchanged — ``THINKING_NEAR_BOTTOM_PX`` (32px band) +
    ``isThinkingNearBottom`` and the pre-render capture
    ``const pinned = block.open && isThinkingNearBottom(textEl);``
    (measured BEFORE the re-render) still sit in the `thinking`
    handler — now operating per block (phase 158: the re-render is
    the RUN's text, not the whole-turn accumulator). The capture
    already keys off ``block.open``, so a live-open block resumes
    pinned tail-following exactly like the phase-17 flow."""
    js = _js()
    assert "export const THINKING_NEAR_BOTTOM_PX = 32;" in js, (
        "the 32px window band is unchanged"
    )
    fn = re.search(
        r"function isThinkingNearBottom\(textEl\) \{([\s\S]*?)\n\}", js
    )
    assert fn, "isThinkingNearBottom must still exist"
    assert "THINKING_NEAR_BOTTOM_PX" in fn.group(1)
    branch = _thinking_branch()
    capture = "const pinned = block.open && isThinkingNearBottom(textEl);"
    assert capture in branch, (
        "the pre-render `block.open &&` guard line is unchanged — the "
        "pin logic moves verbatim into the per-run branch (phase 17 "
        "regression)"
    )
    capture_idx = branch.find(capture)
    render_idx = branch.find("textEl.innerHTML = renderMarkdown(currentRun.run.text)")
    assert -1 < capture_idx < render_idx, (
        "pin state is still measured BEFORE the re-render (phase-17 "
        "regression — the 2-newline-gap fix)"
    )
    assert "textEl.scrollTop = textEl.scrollHeight" in branch, (
        "pinned tail-following is intact"
    )


# ---------- task 02: the persistent in-turn loader (D16) ----------


def test_index_html_carries_exactly_one_turn_loader() -> None:
    """Phase 109 (D16) + phase 117 redesign: ``index.html`` carries
    exactly ONE static ``#turn-loader`` — the equalizer shell holding
    the FIVE static ``.eq`` square spans (never constructed in JS: the
    createElement/textContent house rule), ``aria-hidden="true"``
    (decorative — ``#send-status`` carries the meaning), ``hidden`` by
    default (idle on load), sitting INSIDE the composer form and LEFT
    of the send button (phase 117, owner requirement: the loader's
    appearance/disappearance must never shift the button — it eats the
    flex:1 textarea's space instead)."""
    html = _html()
    assert html.count('id="turn-loader"') == 1, (
        "exactly one #turn-loader — static markup, never JS-built"
    )
    match = re.search(r'<div\s+id="turn-loader"[^>]*>', html)
    assert match, "the loader must be a static <div>"
    tag = match.group(0)
    assert 'class="turn-loader"' in tag
    assert 'aria-hidden="true"' in tag, "decorative — aria-hidden"
    # the hidden attribute (a standalone word in the tag, not the
    # substring of some other attribute value): ships hidden (idle).
    assert re.search(r"\shidden\s*/?>$", tag), (
        "the loader ships hidden (idle on load)"
    )
    # Phase 117: the static brain-wave SVG — EXACTLY the ghost trace +
    # the pulse sweep (pathLength-normalized for the CSS dash math),
    # and nothing else. No JS-built HTML anywhere near it.
    close_idx = html.index("</div>", match.end())
    block = html[match.end():close_idx]
    assert '<svg class="bw"' in block, (
        "the loader carries the static brain-wave SVG"
    )
    assert block.count("<path") == 2, (
        "the SVG carries exactly two paths (ghost trace + pulse sweep)"
    )
    assert 'class="bw-ghost"' in block, "the dim ghost trace is pinned"
    assert 'class="bw-pulse"' in block, "the brand sweep path is pinned"
    assert 'pathLength="140"' in block, (
        "pathLength normalizes the sweep's dash math (styles.css)"
    )
    assert '<span class="eq"' not in block, (
        "the first-mock equalizer spans are gone (the owner picked the "
        "brain wave)"
    )
    # inside the composer form, LEFT of the send button (phase 117):
    # textarea → loader → button, so the button stays pinned at the
    # row's right edge.
    composer_idx = html.find('<form class="composer" id="composer"')
    assert composer_idx != -1
    form_end = html.find("</form>", composer_idx)
    assert composer_idx < match.start() < form_end, (
        "the loader sits in the composer"
    )
    input_idx = html.find('id="message-input"', composer_idx)
    btn_idx = html.find('id="send-btn"', composer_idx)
    assert input_idx < match.start() < btn_idx, (
        "the loader sits LEFT of the send button (the button never "
        "shifts when the loader appears/disappears)"
    )


def test_set_ui_state_is_the_sole_owner_of_the_loader() -> None:
    """Phase 109 (D16) — the never-stale guarantee, structural: in
    ``app.js`` the string ``turnLoader.hidden`` appears EXACTLY ONCE,
    inside ``setUiState`` (the cross-file single-owner check — any
    second write site fails this test). The toggle is
    ``turnLoader.hidden = !inFlight`` next to the existing ``is-stop``
    toggle: shown iff ``uiState`` is thinking|streaming. Every terminal
    path funnels through ``setUiState`` (done → idle, error → error,
    stop/timeout → their landings), so the loader hides in every
    terminal state BY CONSTRUCTION — no per-handler cleanup."""
    js = _js()
    # The element lookup joins the other module-top lookups.
    assert 'const turnLoader = document.querySelector("#turn-loader");' in js
    # THE invariant: exactly one write site in the whole file.
    assert js.count("turnLoader.hidden") == 1, (
        "setUiState is the SOLE writer of the loader's hidden attribute — "
        "a second write site breaks the §7.4 never-stale guarantee"
    )
    # ...and it sits INSIDE setUiState, next to the is-stop toggle.
    fn = js.find("export function setUiState")
    assert fn != -1
    body_end = js.find("\n}\n", fn)
    owner_idx = js.find("turnLoader.hidden")
    assert fn < owner_idx < body_end, (
        "the toggle must live inside setUiState (the single entry point)"
    )
    stop_idx = js.find('sendBtn.classList.toggle("is-stop", inFlight);', fn)
    assert -1 < stop_idx < owner_idx, (
        "the loader toggle joins the existing is-stop toggle"
    )
    assert "turnLoader.hidden = !inFlight;" in js, (
        "shown iff inFlight (thinking|streaming)"
    )


def test_loader_css_brain_wave_contract() -> None:
    """Phase 117 (the phase-109 D16 CSS pin, superseded by the owner's
    brain-wave design — picked over the first equalizer mock): the
    ``.turn-loader`` rule sits NEXT TO the typing-dots rules (after
    the ``@keyframes typing`` block); the sweep is a NEW ``bwdraw``
    keyframe (a ``stroke-dashoffset`` travel — the 42/140 dash segment
    loops the pathLength-normalized path seamlessly); the equalizer
    machinery (``.eq`` squares + ``eqpulse``) is GONE; the ghost trace
    stays decorative-dim; a ``prefers-reduced-motion`` block stills the
    sweep (the full trace shows static — §7.2 house law); the
    provenance comment names phase 117."""
    css = _css()
    keyframes_idx = css.find("@keyframes typing")
    assert keyframes_idx != -1, (
        "the typing-dot keyframes still exist (the chat-log typing bubble)"
    )
    # The MAIN rule (".turn-loader {" — the reduced-motion block's
    # selector never starts that exact string) must sit next to
    # (after) the typing-dots rules.
    rule_idx = css.find(".turn-loader {")
    assert rule_idx != -1, "styles.css must carry a .turn-loader rule"
    assert keyframes_idx < rule_idx, (
        "the .turn-loader rule sits next to (after) the typing-dots rules"
    )
    # The provenance comment: the /* ... */ block immediately preceding
    # the rule names phase 117 (the brain-wave redesign).
    comment_start = css.rfind("/*", 0, rule_idx)
    assert comment_start != -1
    comment = css[comment_start:rule_idx]
    assert "Phase 117" in comment, "the provenance comment names phase 117"
    # The sweep: the .bw-pulse path runs the NEW bwdraw keyframe (the
    # phase-109 "reuse the typing animation" pin is superseded by the
    # owner's redesign — an explicit decision, not a silent deviation).
    pulse_idx = css.find(".turn-loader .bw-pulse {")
    assert pulse_idx != -1, "styles.css must carry a .turn-loader .bw-pulse rule"
    pulse_rule = css[pulse_idx : css.find("}", pulse_idx)]
    assert re.search(r"animation:\s*bwdraw\b", pulse_rule), (
        "the sweep runs the bwdraw keyframe"
    )
    assert "stroke-dasharray: 42 98" in pulse_rule, (
        "the 42/140 bright segment is pinned (the owner-tuned sweep — "
        "the dash cycle equals the pathLength-normalized path: seamless)"
    )
    draw_idx = css.find("@keyframes bwdraw")
    assert draw_idx != -1, "the bwdraw keyframes must exist"
    draw_block = css[draw_idx : css.find("\n}", draw_idx) + 2]
    assert "stroke-dashoffset: 140" in draw_block, "the travel starts at 140"
    assert "stroke-dashoffset: 0" in draw_block, (
        "the travel ends at 0 (one full normalized loop — seamless)"
    )
    # The ghost trace stays decorative-dim (ink-soft at 30% — the shape
    # must be readable between sweep peaks).
    ghost_idx = css.find(".turn-loader .bw-ghost {")
    assert ghost_idx != -1, "styles.css must carry a .turn-loader .bw-ghost rule"
    ghost_rule = css[ghost_idx : css.find("}", ghost_idx)]
    assert "stroke-opacity: 0.3" in ghost_rule, (
        "the ghost trace stays dim (the sweep carries the attention)"
    )
    # The old machinery is GONE: the phase-109 pseudo-dots, the
    # typing-animation reuse inside the loader's rules, and the first-
    # mock equalizer (.eq squares + eqpulse).
    assert ".turn-loader::before" not in css, (
        "the phase-109 pseudo-dot rules are gone"
    )
    loader_region = css[rule_idx:draw_idx]
    assert "animation: typing" not in loader_region, (
        "the loader no longer reuses the typing animation (phase 117)"
    )
    assert ".turn-loader .eq" not in css, (
        "the first-mock equalizer rules are gone (the owner picked the "
        "brain wave)"
    )
    assert "@keyframes eqpulse" not in css, "the eqpulse keyframes are gone"
    # The prefers-reduced-motion block stills the SWEEP: the full trace
    # shows static — §7.2 (stilling never hides: visibility is the JS
    # hidden attribute in setUiState, D16).
    reduced_ok = False
    for m in re.finditer(r"@media \(prefers-reduced-motion: reduce\) \{([\s\S]*?)\n\}", css):
        if ".turn-loader .bw-pulse" in m.group(1) and "animation: none" in m.group(1):
            reduced_ok = True
            break
    assert reduced_ok, (
        "a prefers-reduced-motion block must still the sweep (static "
        "trace, no motion — §7.2)"
    )


def test_loader_is_aria_hidden_and_status_untouched() -> None:
    """Phase 109 (D16) — the a11y split is untouched: the loader is
    ``aria-hidden`` (decoration), and ``#send-status`` keeps its exact
    attributes in ``index.html`` — still the sole ``aria-live``
    announcer (the house a11y split: visual cues are aria-hidden, the
    live region carries the state text)."""
    html = _html()
    match = re.search(r'<div\s+id="turn-loader"[^>]*>', html)
    assert match and 'aria-hidden="true"' in match.group(0)
    # #send-status is unchanged: one element, the exact same tag —
    # the visually-hidden polite live region inside the send button,
    # still the chat view's state announcer.
    assert html.count('id="send-status"') == 1
    status = re.search(r'<span[^>]*id="send-status"[^>]*></span>', html)
    assert status, "the #send-status live region is intact"
    tag = status.group(0)
    assert tag == (
        '<span class="visually-hidden" aria-live="polite" '
        'id="send-status"></span>'
    ), "the #send-status attributes are byte-unchanged"
    # the loader added no a11y surface: it is aria-hidden and carries
    # no live region of its own.
    assert 'aria-live' not in match.group(0)