"""Drift-detection: brand palette in `app/branding.py` must match the CSS.

Both the website (cassandra.css) and the email templates use the same
palette. The CSS hand-authors the values in :root and [data-theme="light"]
blocks; this test parses those blocks and asserts every variable matches
its counterpart in branding.py. If a colour changes, both must change.
"""
from __future__ import annotations

import re
from pathlib import Path

import pytest

from app import branding


CSS_PATH = Path(__file__).resolve().parent.parent / "app" / "static" / "css" / "cassandra.css"


def _extract_vars(css: str, selector: str) -> dict[str, str]:
    """Parse `--name: value;` declarations inside the first matching
    selector block. Strips whitespace; lowercases hex values."""
    # Match the selector followed by its block. Non-greedy on the body to
    # stop at the first closing brace at the same depth (these blocks
    # don't nest in cassandra.css).
    pattern = re.escape(selector) + r"\s*\{([^}]*)\}"
    m = re.search(pattern, css)
    if not m:
        raise AssertionError(f"selector {selector!r} not found in CSS")
    body = m.group(1)
    out: dict[str, str] = {}
    for line in body.splitlines():
        decl = re.match(r"\s*--([a-z0-9-]+)\s*:\s*([^;]+);", line)
        if not decl:
            continue
        name, value = decl.group(1), decl.group(2).strip().lower()
        out[name] = value
    return out


@pytest.fixture(scope="module")
def css_text() -> str:
    return CSS_PATH.read_text(encoding="utf-8")


def test_light_palette_matches_css(css_text):
    # Light is the default — lives in `:root`. Dark is opt-in via the
    # data-theme attribute toggle.
    css_light = _extract_vars(css_text, ":root")
    for key, expected in branding.LIGHT.items():
        actual = css_light.get(key)
        assert actual == expected.lower(), (
            f"LIGHT[{key!r}] mismatch: branding.py={expected!r} vs css={actual!r}"
        )


def test_dark_palette_matches_css(css_text):
    css_dark = _extract_vars(css_text, '[data-theme="dark"]')
    for key, expected in branding.DARK.items():
        actual = css_dark.get(key)
        assert actual == expected.lower(), (
            f"DARK[{key!r}] mismatch: branding.py={expected!r} vs css={actual!r}"
        )


def test_palette_keys_match_between_themes():
    """If a colour is defined in dark, it must also be defined in light
    (and vice versa) — otherwise the theme switch leaves elements
    unstyled."""
    assert set(branding.DARK.keys()) == set(branding.LIGHT.keys())


def test_email_uses_branding_palette():
    """Sanity: the rendered OTP HTML should contain at least one of each
    theme's key colours, confirming the substitution actually wired up."""
    from app.services.email_service import render_otp_email

    _, _, html = render_otp_email("123456", 15)
    assert branding.LIGHT["accent"] in html
    assert branding.DARK["accent"] in html
    assert branding.LIGHT["bg"] in html
    assert branding.DARK["bg"] in html