"""Unit: the Sources (git sources) page card rhythm (phase 174, task 01).

Owner bug report 2026-10-21: "the bubbles on the sources page are
really smooshed together" — the "Git sources" header card, the
"Add a git source" card, the "Upload a source archive" card, and the
sources table card stacked flush (only their 1px borders separated
them). Root cause: the `.git-sources-shell` gap (1.25rem) only
separates the sign-in gate from the single ``#git-sources-content``
wrapper; every visible card is a child of THAT div, which was a plain
block. The fix is the phase-171 ``#settings-content`` idiom applied to
the one remaining admin view whose cards live inside a wrapper div:
``#git-sources-content`` itself becomes ``display: flex;
flex-direction: column; gap: 1.25rem;`` — the shell's OWN existing
token (no new spacing value).

This module pins the source-level contract a silent regression would
break; the browser behavior (bounding-box gaps at 1440px and 375px,
hidden-children pin, gate reveal) is E2E-gated by the phase-174 story
suite (``tests/e2e/test_git_sources_card_rhythm.py``, task 02).

Pinned:

* the ``#git-sources-content`` rule exists in ``styles.css`` and
  carries ``display: flex``, ``flex-direction: column``, and
  ``gap: 1.25rem`` EXACTLY (a regression to any other gap value or a
  missing flex line fails);
* the ``.git-sources-shell`` rule still carries ``gap: 1.25rem`` and
  ``flex: 1`` (the fix must not have "fixed" the shell — D3);
* the structural pin: in ``index.html``, ``#git-sources-content`` sits
  inside ``.container.git-sources-shell`` and the ``.sources-gate``
  (``#git-sources-gate``) is a sibling of it — if a future refactor
  moves the cards to the shell's direct children, this rule becomes
  dead weight and this pin names it;
* ``#git-sources-load-error`` (role=alert) and the env note
  (id ``git-sources-env-note``, class ``git-source-env-note`` — the
  phase docstring's ``#git-source-env-note`` names the class) still
  carry ``hidden`` in ``index.html`` (the D2 premise the E2E pin
  proves in a browser: the UA ``[hidden] → display:none`` holds inside
  a flex parent, so the reveal lifecycle is untouched).
"""
from __future__ import annotations

import re
from pathlib import Path

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

GAP_TOKEN = "1.25rem"


def _read(path: Path) -> str:
    return path.read_text(encoding="utf-8")


def _css_rule(css: str, selector: str) -> str:
    """The body of one CSS rule: ``selector { … }`` (no nested
    braces in these rules), whitespace-normalized. Raises if the
    selector's rule is absent (a missing rule IS the regression)."""
    m = re.search(re.escape(selector) + r"\s*\{([^}]*)\}", css)
    assert m is not None, f"rule for {selector!r} not found in styles.css"
    return " ".join(m.group(1).split())


def _div_span(html: str, open_tag: str) -> str:
    """The substring from an opening <div …> to its matching </div>
    (balanced div-tag counting — the test_git_source_branch_ui.py
    brace-counting helper, applied to HTML)."""
    start = html.index(open_tag)
    depth = 0
    for m in re.finditer(r"<div\b|</div>", html[start:]):
        if m.group(0) == "</div>":
            depth -= 1
            if depth == 0:
                return html[start : start + m.end()]
        else:
            depth += 1
    raise AssertionError(f"unbalanced divs from {open_tag!r}")


def _direct_children_tags(html: str) -> list[str]:
    """The element tags that open at DEPTH 1 (direct children) of the
    substring (the leading <div> is depth 0 — the counted element).
    Void elements (input/br/img/… — this markup uses non-self-closing
    <input …>) change no depth."""
    VOID = {"input", "br", "img", "hr", "meta", "link", "source", "wbr"}
    out: list[str] = []
    depth = 1  # we are inside the shell div
    for m in re.finditer(r"</?[a-zA-Z][^>]*?>", html):
        tag = m.group(0)
        mname = re.match(r"</?([a-zA-Z]+)", tag)
        name = mname.group(1).lower() if mname else ""
        if tag.startswith("</"):
            depth -= 1
            if depth == 0:
                break
        elif name not in VOID and not tag.endswith("/>"):
            if depth == 1:
                out.append(tag)
            depth += 1
    return out


def test_content_wrapper_is_the_flex_rhythm_column() -> None:
    """D1: #git-sources-content carries the exact flex-column rhythm —
    display: flex, flex-direction: column, gap: 1.25rem (the shell's
    own token; a different gap value or a missing flex line fails)."""
    body = _css_rule(_read(STYLES_CSS), "#git-sources-content")
    assert "display: flex" in body, body
    assert "flex-direction: column" in body, body
    # The EXACT token — ``gap: 1.25rem`` and no other gap declaration:
    gaps = re.findall(r"gap\s*:\s*([^;]+)", body)
    assert gaps == [GAP_TOKEN], f"gap regression: {gaps}"


def test_shell_rule_unchanged() -> None:
    """D3: the fix must not have 'fixed' the shell — .git-sources-shell
    keeps flex-direction: column, gap: 1.25rem, and flex: 1 (the
    gate↔content separation at anonymous)."""
    body = _css_rule(_read(STYLES_CSS), ".git-sources-shell")
    assert "display: flex" in body, body
    assert "flex-direction: column" in body, body
    gaps = re.findall(r"gap\s*:\s*([^;]+)", body)
    assert gaps == [GAP_TOKEN], f"shell gap regression: {gaps}"
    assert "flex: 1" in body, body


def test_content_div_sits_inside_shell_with_gate_sibling() -> None:
    """The structural pin: #git-sources-content is a direct child of
    .container.git-sources-shell, and the .sources-gate
    (#git-sources-gate) is its sibling. If a future refactor moves the
    cards back to the shell's direct children, the phase-174 rule
    becomes dead weight — this pin names that."""
    html = _read(SHELL_HTML)
    shell_open = '<div class="container git-sources-shell">'
    assert shell_open in html, "the .git-sources-shell container is gone"
    shell = _div_span(html, shell_open)[len(shell_open):]
    children = _direct_children_tags(shell)
    gates = [t for t in children if 'id="git-sources-gate"' in t]
    contents = [t for t in children if 'id="git-sources-content"' in t]
    assert len(gates) == 1, (
        "the #git-sources-gate section is no longer a DIRECT child of "
        f"the shell (children: {children})"
    )
    assert len(contents) == 1, (
        "the #git-sources-content div is no longer a DIRECT child of "
        f"the shell (children: {children}) — if the cards moved back to "
        "the shell's direct children, the phase-174 wrapper rule is "
        "dead weight: move the rule or the cards, and update this pin"
    )
    # The gate precedes the content (the reveal hides the gate and
    # flips the content):
    assert children.index(gates[0]) < children.index(contents[0])


def test_hidden_children_keep_hidden_in_markup() -> None:
    """The D2 premise: #git-sources-load-error (role=alert) and the env
    note (id git-sources-env-note, role=note) still carry ``hidden``
    in the markup — inside the flex wrapper the UA [hidden]
    display:none holds (the parent's display never overrides a child's
    own), so git-sources.js's reveal lifecycle is untouched."""
    html = _read(SHELL_HTML)
    # The phase docstring's #git-source-env-note is the element's CLASS;
    # its id is git-sources-env-note — pin the id, fall back to the
    # class (both name the same element).
    for tag_id in ("git-sources-load-error", "git-sources-env-note"):
        m = re.search(rf'<[a-z]+ [^>]*id="{tag_id}"[^>]*>', html)
        assert m is not None, f"the {tag_id} element is gone"
        tag = m.group(0)
        assert " hidden" in tag or tag.rstrip(">").endswith("hidden"), (
            f"{tag_id} lost its hidden attribute — the E2E hidden pin "
            f"would break: {tag}"
        )