"""Every SVG the browser loads from `frontend/public/` must parse as XML.

A browser renders an SVG used as an image only if it is well-formed XML, and
when it is not, nothing reports it: no console error in most browsers, no
failed build, no failed request — the icon is simply blank. `favicon.svg`
shipped that way (merge #251) because its comment contained a CSS custom
property name, and `--` is illegal inside an XML comment. Both the tab icon and
the nav brand mark went missing, and only a person looking at the page noticed.
"""
from __future__ import annotations

import xml.etree.ElementTree as ET
from pathlib import Path

import pytest

PUBLIC = Path(__file__).resolve().parent.parent / "frontend" / "public"
SVGS = sorted(PUBLIC.rglob("*.svg"))


def test_the_public_dir_has_svgs_to_check():
    """Guards the guard: a moved directory would otherwise pass vacuously."""
    assert {p.name for p in SVGS} >= {"favicon.svg", "logo.svg"}


@pytest.mark.parametrize("svg", SVGS, ids=lambda p: p.name)
def test_svg_is_well_formed_xml(svg):
    root = ET.parse(svg).getroot()
    assert root.tag == "{http://www.w3.org/2000/svg}svg"


def test_the_parser_rejects_the_shape_that_broke_the_favicon():
    """Positive control: the exact defect must fail this parser, or the
    parametrized test above proves nothing."""
    broken = (
        '<svg xmlns="http://www.w3.org/2000/svg">'
        "<!-- matches --fc-chrome-rgb exactly --></svg>"
    )
    with pytest.raises(ET.ParseError):
        ET.fromstring(broken)