"""Unit: the phase-62 example theme (``frontend/assets/themes/``) and
the Containerfile line that ships it (A7).

No Python logic exists for this task — the mechanism lives in
``brand.js`` (pinned by test_frontend_brand.py) and the theme is a
drop-in stylesheet. Like the other frontend-adjacent unit files, this
module pins the assets as text, so a silent regression (a theme file
gaining a selector, a declaration drifting, the Containerfile line
vanishing) is caught without a browser. The browser-visible layer
(computed ``--brand``, the inserted ``<link>``) is E2E-gated by
``tests/e2e/test_ui_customization.py`` (task 05).
"""
from __future__ import annotations

import re
from pathlib import Path

REPO_ROOT = Path(__file__).resolve().parents[2]
FRONTEND = REPO_ROOT / "frontend"
THEMES = FRONTEND / "assets" / "themes"
INDIGO = THEMES / "indigo.css"
GUIDE = THEMES / "README.md"
CONTAINERFILE = REPO_ROOT / "Containerfile"

#: The 8 identity variables a theme may override — and the EXACT set
#: indigo.css ships (the semantic families accent/ok/err are states,
#: not identity: a theme that overrides them stops being honest).
IDENTITY_VARS = (
    "--bg",
    "--surface",
    "--ink",
    "--ink-soft",
    "--line",
    "--brand",
    "--brand-soft",
    "--brand-ink",
)

INDIGO_VALUES: dict[str, str] = {
    "--bg": "#0a0e1a",
    "--surface": "#111726",
    "--ink": "#e6e9f0",
    "--ink-soft": "#a8b0c8",
    "--line": "#232c44",
    "--brand": "#818cf8",
    "--brand-soft": "#1a1f38",
    "--brand-ink": "#c7d2fe",
}


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


def _strip_comments(css: str) -> str:
    """Drop ``/* … */`` comments — the pins assert against declarations,
    not prose."""
    return re.sub(r"/\*.*?\*/", "", css, flags=re.S)


def _declarations(css: str) -> dict[str, str]:
    """The ``--name: value`` declarations of the (single) ``:root``
    block, in file order."""
    return dict(re.findall(r"(--[a-z-]+)\s*:\s*([^;]+);", css))


def test_example_theme_files_exist() -> None:
    """The example theme and its authoring guide ship in the static
    dir (served at /assets/themes/… in dev AND in the image)."""
    assert INDIGO.is_file(), f"missing example theme: {INDIGO}"
    assert GUIDE.is_file(), f"missing authoring guide: {GUIDE}"


def test_indigo_starts_with_a_single_root_block_and_nothing_else() -> None:
    """The whole file is ONE ``:root`` block (the cascade is the entire
    mechanism): after stripping comments the first non-whitespace
    content is ``:root``, and no other rule, selector, or declaration
    exists anywhere in the file."""
    css = _strip_comments(_text(INDIGO))
    assert css.lstrip().startswith(":root"), (
        "indigo.css must start with the :root block (after its header "
        "comment) — nothing may precede it"
    )
    assert re.fullmatch(r"\s*:root\s*\{[^{}]*\}\s*", css, re.S) is not None, (
        "indigo.css must be exactly one :root block — no selectors, "
        "no @media, no nested or extra rules"
    )


def test_indigo_overrides_exactly_the_eight_identity_variables() -> None:
    """EXACTLY the 8 identity overrides with the locked values — no
    other declarations (a 9th declaration here would be the theme
    reaching past the palette), and the semantic families
    (accent/ok/err) must be untouched (they encode states)."""
    decls = _declarations(_strip_comments(_text(INDIGO)))
    assert set(decls) == set(IDENTITY_VARS), (
        f"indigo.css must override exactly the 8 identity variables, got "
        f"{sorted(decls)}"
    )
    for name in IDENTITY_VARS:
        assert decls[name].strip() == INDIGO_VALUES[name], (
            f"{name} drifted from the locked value "
            f"{INDIGO_VALUES[name]!r}, got {decls[name].strip()!r}"
        )
    for family in ("--accent-", "--ok-", "--err-"):
        assert not any(k.startswith(family) for k in decls), (
            f"semantic {family}* variables must stay the built-in "
            f"theme (they encode states)"
        )


def test_indigo_identity_pairs_meet_wcag_aa() -> None:
    """The five identity text/background pairs, computed from the file's
    OWN hex values (not re-typed), each meet WCAG 2.1 AA (>= 4.5:1) —
    AGENTS.md rule 5. The pairs are the ones the layout actually pairs:
    ink on bg/surface, ink-soft on surface, the dark bg ink on brand
    (text on brand buttons is --bg, never white — the built-in's
    documented 3.7:1 trap), brand-ink on surface."""
    decls = _declarations(_strip_comments(_text(INDIGO)))

    def lum(hexcolor: str) -> float:
        h = hexcolor.lstrip("#")
        chans = (int(h[i : i + 2], 16) / 255.0 for i in (0, 2, 4))
        lin = [
            c / 12.92 if c <= 0.04045 else ((c + 0.055) / 1.055) ** 2.4
            for c in chans
        ]
        r, g, b = lin
        return 0.2126 * r + 0.7152 * g + 0.0722 * b

    def ratio(fg: str, bg: str) -> float:
        l1, l2 = lum(fg), lum(bg)
        return (max(l1, l2) + 0.05) / (min(l1, l2) + 0.05)

    pairs = (
        ("ink on bg", decls["--ink"], decls["--bg"]),
        ("ink on surface", decls["--ink"], decls["--surface"]),
        ("ink-soft on surface", decls["--ink-soft"], decls["--surface"]),
        ("bg ink on brand", decls["--bg"], decls["--brand"]),
        ("brand-ink on surface", decls["--brand-ink"], decls["--surface"]),
    )
    for name, fg, bg in pairs:
        r = ratio(fg, bg)
        assert r >= 4.5, f"{name}: {r:.2f}:1 < 4.5:1 (WCAG 2.1 AA)"


def test_containerfile_ships_the_whole_themes_directory() -> None:
    """A7: stage 1 copies the WHOLE themes directory (no per-file
    esbuild — a future theme file needs no Containerfile edit), and it
    does so AFTER the styles.css minify line (so the served /assets/
    tree is complete before the pages cp)."""
    cf = _text(CONTAINERFILE)
    stage1 = cf.split("AS frontend", 1)[1].split("\nFROM", 1)[0]
    lines = stage1.splitlines()
    cp_idxs = [
        i
        for i, ln in enumerate(lines)
        if re.search(r"\bcp\s+-r\s+\./assets/themes\s+/out/assets/themes\b", ln)
    ]
    assert len(cp_idxs) == 1, (
        "stage 1 must ship the themes directory with exactly one "
        "'cp -r ./assets/themes /out/assets/themes' line"
    )
    styles_idxs = [
        i for i, ln in enumerate(lines) if "esbuild ./assets/styles.css" in ln
    ]
    assert len(styles_idxs) == 1, "stage 1 must minify styles.css"
    assert cp_idxs[0] > styles_idxs[0], (
        "the themes cp must come AFTER the styles.css minify line"
    )
    cp_line = lines[cp_idxs[0]]
    assert "--bundle" not in cp_line and "esbuild" not in cp_line, (
        "A7: the themes directory is copied verbatim — no per-file "
        "esbuild minify"
    )


def test_authoring_guide_pins_the_contract() -> None:
    """The guide documents the load path (BOR_THEME → /api/config →
    brand.js link after styles.css), the filename validator regex, the
    8-variable table, the 4.5:1 bar, the never-white-on-brand trap,
    and the A7 rebuild story (a new file needs no Containerfile edit)."""
    guide = _text(GUIDE)
    for marker in (
        "BOR_THEME",
        "/api/config",
        "styles.css",
        r"^[a-z0-9_-]+\.css$",
        "4.5:1",
        "white-on-brand",
        "cp -r ./assets/themes /out/assets/themes",
    ):
        assert marker in guide, f"themes/README.md must document {marker!r}"
    for var in IDENTITY_VARS:
        assert var in guide, f"the variable table must list {var}"