"""Unit: the phase-93 page-head surface panel contract (task 03 —
source pins).

Owner direction (TODO.md L3): "Also the header and description of each
page needs a background - the grid makes it hard to read." Every
page's ``h1`` + description (the shell's standard ``.page-head`` frame)
sits on a solid ``var(--surface)`` panel — the house card language —
so the 44px background grid never fights the heading text. Browser
behavior (computed ``background-color`` non-transparent on every head,
the History flex row + 360px wrap unbroken, the monochrome theme
graying the panel) is E2E-gated by ``tests/e2e/
test_theme_semantic_completion.py`` (task 04) and the existing
header/nav/responsive suites; here we pin the source-level contract
(house pattern: ``tests/unit/test_background_no_motion.py`` parses
``styles.css`` rules):

* the shared ``.page-head`` rule declares the panel — a NON-transparent
  ``background`` built from ``var(--surface)`` (no color literal of any
  kind, no blur — the phase-08 perf anchor), the 1px ``var(--line)``
  border, the house card radius, and card-rhythm padding;
* the ``#view-history`` page-head keeps its SCOPED flex row (padding
  lives on the flex container — the base rule — never on the
  children), and the mobile ``.page-head-row { flex-wrap: wrap; }``
  survives;
* every shell view that carries a ``.page-head`` in the shell markup
  is covered by the ONE rule (six views; ``#view-chat`` carries no
  ``.page-head`` — its head is the navbar, audited), and
  ``doc-edit.html`` keeps its ``.page-head``;
* the standalone pages: the shared page's head (``h1#shared-title`` +
  the lede) is wrapped in the same ``.page-head`` class, while the two
  heads that already sit inside a surfaced card are deliberately
  UNTOUCHED (login's ``.login-card`` — surface card; document viewer's
  ``.doc-titlebar`` inside the sticky surface ``.doc-header``).
"""
from __future__ import annotations

import re
from pathlib import Path

FRONTEND = Path(__file__).resolve().parents[2] / "frontend"
STYLES_CSS = FRONTEND / "assets" / "styles.css"
INDEX_HTML = FRONTEND / "index.html"
SHARED_HTML = FRONTEND / "shared.html"
DOC_EDIT_HTML = FRONTEND / "doc-edit.html"
LOGIN_HTML = FRONTEND / "login.html"
DOCUMENT_HTML = FRONTEND / "document.html"

# The six shell views whose h1 + description sit in a .page-head
# (#view-chat carries none — its head is the navbar; audited).
SHELL_VIEWS_WITH_PAGE_HEAD = (
    "view-tuning",
    "view-rag",
    "view-git-sources",
    "view-history",
    "view-tokens",
    "view-theme",
)


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


def _css_no_comments() -> str:
    return re.sub(r"/\*[\s\S]*?\*/", "", _css())


def _find_rule(css: str, selector: str) -> re.Match[str] | None:
    """The first top-level ``selector { ... }`` rule (comments
    stripped by the caller when prose must not interfere)."""
    return re.search(r"(?m)^" + re.escape(selector) + r"\s*\{([\s\S]*?)\n\}", css)


def _rule_block(css: str, selector: str) -> str:
    rule = _find_rule(css, selector)
    assert rule, f"styles.css must define a {selector} rule"
    return rule.group(1)


def _view_section(body: str, view_id: str) -> str:
    """The view section slice — from its opening tag to the next
    sibling view (or ``</main>``). A first-``</section>`` slice would
    cut short: the views nest gate sections (``<section
    class="sources-gate">``) INSIDE, and the Git-sources / Theme
    ``.page-head`` sits after the first nested close."""
    start = body.find(f'<section class="view" id="{view_id}"')
    assert start != -1, f"the #{view_id} section must be in the shell"
    boundaries = [
        e
        for e in (body.find('<section class="view"', start + 1), body.find("</main>", start))
        if e != -1
    ]
    assert boundaries, "the shell must have a closing </main>"
    return body[start : min(boundaries)]


# --------------------------------------------------------------------------
# The shared .page-head rule — the surface panel
# --------------------------------------------------------------------------


def test_page_head_rule_is_the_surface_panel() -> None:
    """The one shared rule declares the panel: a non-transparent
    background from ``var(--surface)`` (itself tab-controlled — a
    monochrome theme grays the head automatically), the 1px
    ``var(--line)`` border, the house card radius, and card-rhythm
    padding (the phase-93 panel: 1rem block / 1.25rem inline)."""
    block = _rule_block(_css_no_comments(), ".page-head")
    assert "background: var(--surface)" in block, (
        "the .page-head panel must fill with var(--surface) — solid, "
        "never transparent, never a literal"
    )
    assert "border: 1px solid var(--line)" in block, (
        "the panel must carry the house 1px --line border"
    )
    assert "border-radius: var(--radius)" in block, (
        "the panel must use the house card radius"
    )
    assert re.search(r"padding:\s*1rem\s+1\.25rem", block), (
        "the panel must carry the card-rhythm padding (1rem 1.25rem)"
    )


def test_page_head_rule_has_no_color_literal_and_no_blur() -> None:
    """Phase-92 invariant + phase-08 perf anchor: the panel rule
    introduces NO new color literal (hex / rgb / hsl / color-mix —
    ``var(--…)`` only) and no filter/blur."""
    block = _rule_block(_css_no_comments(), ".page-head")
    assert not re.search(r"#[0-9a-fA-F]{3,8}\b", block), (
        "no hex color literal in the .page-head panel (phase-92 invariant)"
    )
    for func in ("rgb(", "hsl(", "color-mix("):
        assert func not in block, f"no {func}… literal in the .page-head panel"
    assert "filter" not in block and "blur" not in block, (
        "no filter/blur in the .page-head panel (phase-08 perf anchor)"
    )


def test_page_head_background_is_solid_not_translucent() -> None:
    """The panel is SOLID — the assumption the phase locked (not
    translucent, not a full-bleed band, no blur): the background
    declaration names exactly the surface variable, nothing mixed."""
    block = _rule_block(_css_no_comments(), ".page-head")
    backgrounds = re.findall(r"(?m)^\s*background(?:-color)?:\s*([^;]+);", block)
    assert backgrounds == ["var(--surface)"], (
        f"the .page-head background must be exactly var(--surface), "
        f"got {backgrounds}"
    )


# --------------------------------------------------------------------------
# Layout safety — the History flex row and the mobile wrap
# --------------------------------------------------------------------------


def test_history_page_head_keeps_its_scoped_flex_row() -> None:
    """The ``#view-history .page-head`` flex row (title left, refresh
    pill right — phase 77) survives the panel: the scoped rule keeps
    its flex declarations and adds NO padding of its own (the task-03
    rule — padding on the flex container, i.e. the base ``.page-head``
    rule, never on the children, so space-between + align stay intact
    inside the padded box)."""
    scoped = _rule_block(_css_no_comments(), "#view-history .page-head")
    for decl in (
        "display: flex",
        "flex-wrap: wrap",
        "align-items: flex-start",
        "justify-content: space-between",
    ):
        assert decl in scoped, f"#view-history .page-head must keep {decl!r}"
    assert not re.search(r"(?m)^\s*padding\b", scoped), (
        "the scoped History rule must not add its own padding — the "
        "base .page-head rule (the flex container) carries it"
    )


def test_mobile_page_head_row_wrap_survives() -> None:
    """≤640px: ``.page-head-row { flex-wrap: wrap; }`` (the RAG head's
    Sync pill drops below the title at full width) still exists in the
    mobile block — the wrap keeps working INSIDE the panel."""
    mobile = re.search(r"@media \(max-width: 640px\) \{([\s\S]*?)\n\}\n", _css())
    assert mobile, "the mobile media query must exist"
    assert ".page-head-row { flex-wrap: wrap; }" in mobile.group(1), (
        "the mobile .page-head-row wrap must survive the panel"
    )


# --------------------------------------------------------------------------
# Coverage — every head that sits on the grid gets the panel
# --------------------------------------------------------------------------


def test_every_shell_view_with_a_page_head_is_covered() -> None:
    """The ONE rule covers every shell view that carries the class:
    all six do (their ``class="page-head"`` div is static markup in
    the shell); #view-chat carries NO .page-head (its head is the
    navbar — audited, untouched)."""
    body = INDEX_HTML.read_text(encoding="utf-8")
    for view_id in SHELL_VIEWS_WITH_PAGE_HEAD:
        assert 'class="page-head"' in _view_section(body, view_id), (
            f"#{view_id} must keep its .page-head (the shared rule panels it)"
        )
    assert 'class="page-head"' not in _view_section(body, "view-chat"), (
        "#view-chat carries no .page-head (its head is the navbar)"
    )


def test_doc_edit_page_head_is_covered() -> None:
    """doc-edit.html's head already IS a .page-head (h1 'Edit doc' +
    the .page-sub lede) — the shared rule panels it with no markup
    change."""
    html = DOC_EDIT_HTML.read_text(encoding="utf-8")
    head = re.search(
        r'<div class="page-head">\s*<h1>Edit doc</h1>[\s\S]*?class="page-sub"',
        html,
    )
    assert head, "doc-edit.html must keep its .page-head (h1 + page-sub)"


def test_shared_page_head_is_wrapped_in_page_head() -> None:
    """The shared page's head (``h1#shared-title`` + the read-only
    lede) was a direct child of the grid-exposed ``.shared-shell`` —
    it is now wrapped in the same ``.page-head`` class, so the shared
    rule panels it (the h1 keeps the ``.page-head h1`` size per the
    ``#shared-title`` rule)."""
    html = SHARED_HTML.read_text(encoding="utf-8")
    wrapped = re.search(
        r'<div class="page-head">\s*'
        r"<h1 id=\"shared-title\">Shared conversation</h1>\s*"
        r'<p class="shared-note">Shared via Brain of Reese — read-only\.</p>\s*'
        r"</div>",
        html,
    )
    assert wrapped, (
        "shared.html must wrap the h1 + lede in a .page-head div"
    )


# --------------------------------------------------------------------------
# Deliberate skips — heads already inside a surfaced card
# --------------------------------------------------------------------------


def test_login_head_is_already_carded_and_untouched() -> None:
    """login.html: h1#login-title lives inside section.login-card,
    which is ALREADY the surface card (var(--surface) fill + border +
    radius + shadow) — the TODO targets grid-exposed text, so the
    login head gets no double panel."""
    html = LOGIN_HTML.read_text(encoding="utf-8")
    card = re.search(
        r'<section class="login-card"[^>]*>[\s\S]*?'
        r'<h1 id="login-title">Sign in</h1>',
        html,
    )
    assert card, "the login h1 must sit inside the .login-card"
    card_css = _rule_block(_css_no_comments(), ".login-card")
    assert "background: var(--surface)" in card_css
    assert "border: 1px solid var(--line)" in card_css
    assert "border-radius: var(--radius)" in card_css
    assert 'class="page-head"' not in html, (
        "login.html must not gain a .page-head (the card already panels it)"
    )


def test_document_head_is_already_carded_and_untouched() -> None:
    """document.html: h1#doc-title lives in the .doc-titlebar row 2
    inside the STICKY .doc-header, which is already surface-filled
    (var(--surface) — the two-row pinned bar) — no double panel."""
    html = DOCUMENT_HTML.read_text(encoding="utf-8")
    titlebar = re.search(
        r'<div class="doc-titlebar">[\s\S]*?<h1 id="doc-title">', html
    )
    assert titlebar, "the document h1 must sit inside the .doc-titlebar"
    header_css = _rule_block(_css_no_comments(), ".doc-header")
    assert "background: var(--surface)" in header_css, (
        "the sticky .doc-header must stay surface-filled"
    )
    assert 'class="page-head"' not in html, (
        "document.html must not gain a .page-head (the titlebar is "
        "already inside the surface header)"
    )