from html.parser import HTMLParser
from pathlib import Path

from app.auth.services import create_user
from app.tasks.services import configure_focus, create_task


class PageAuditParser(HTMLParser):
    def __init__(self) -> None:
        super().__init__()
        self.ids: list[str] = []
        self.labels: set[str] = set()
        self.controls: list[tuple[str, str | None, str | None, str | None]] = []
        self.button_stack: list[list[str]] = []
        self.button_names: list[str] = []
        self.lang: str | None = None
        self.title_parts: list[str] = []
        self.in_title = False
        self.has_main = False
        self.has_skip_link = False
        self.h1_count = 0

    def handle_starttag(self, tag: str, attrs) -> None:
        attributes = dict(attrs)
        if element_id := attributes.get("id"):
            self.ids.append(element_id)
        if tag == "html":
            self.lang = attributes.get("lang")
        elif tag == "title":
            self.in_title = True
        elif tag == "main" and attributes.get("id") == "main-content":
            self.has_main = True
        elif tag == "a" and attributes.get("href") == "#main-content":
            self.has_skip_link = True
        elif tag == "h1":
            self.h1_count += 1
        elif tag == "label" and attributes.get("for"):
            self.labels.add(attributes["for"])
        elif tag in {"input", "select", "textarea"}:
            self.controls.append(
                (
                    tag,
                    attributes.get("id"),
                    attributes.get("type"),
                    attributes.get("aria-label"),
                )
            )
        elif tag == "button":
            self.button_stack.append([attributes.get("aria-label", "")])

    def handle_endtag(self, tag: str) -> None:
        if tag == "title":
            self.in_title = False
        elif tag == "button" and self.button_stack:
            parts = self.button_stack.pop()
            self.button_names.append(" ".join(parts).strip())

    def handle_data(self, data: str) -> None:
        if self.in_title:
            self.title_parts.append(data)
        if self.button_stack:
            self.button_stack[-1].append(data)


def login(client, email: str) -> None:
    client.post(
        "/auth/login",
        data={"email": email, "password": "secure password"},
    )


def test_primary_pages_have_structural_accessibility(client, db):
    user = create_user("audit_user", "audit@example.com", "secure password")
    task = create_task(
        user.id,
        title="Audited task",
        description="Readable details",
        status="not_started",
        priority="important",
        due_date=None,
    )
    configure_focus(
        task,
        timer_minutes=5,
        context="Quiet desk",
        chunk_minutes=[5, 10],
    )
    login(client, user.email)

    pages = (
        "/",
        "/tasks/",
        "/tasks/today",
        f"/tasks/{task.id}",
        f"/tasks/{task.id}/focus",
        "/tasks/new",
        "/tasks/transfer",
        "/settings/",
    )
    for path in pages:
        response = client.get(path)
        parser = PageAuditParser()
        parser.feed(response.get_data(as_text=True))

        assert response.status_code == 200, path
        assert parser.lang == "en", path
        assert "".join(parser.title_parts).strip(), path
        assert parser.has_main, path
        assert parser.has_skip_link, path
        assert parser.h1_count >= 1, path
        assert len(parser.ids) == len(set(parser.ids)), path
        assert all(parser.button_names), path

        for _tag, element_id, input_type, aria_label in parser.controls:
            if input_type in {"hidden", "submit"}:
                continue
            assert element_id, (path, input_type)
            assert element_id in parser.labels or aria_label, (path, element_id)


def test_css_contains_reflow_focus_target_and_motion_contracts():
    css = Path("app/static/css/style.css").read_text(encoding="utf-8")

    assert "width: min(100% - 2rem, 62rem)" in css
    assert "@media (max-width: 38rem)" in css
    assert "grid-template-columns: 1fr" in css
    assert "min-height: 2.75rem" in css
    assert "outline: 3px solid var(--focus)" in css
    assert "@media (prefers-reduced-motion: reduce)" in css
    reduced_motion = css.split("@media (prefers-reduced-motion: reduce)", 1)[1]
    assert "transition-duration: 0.01ms !important" in reduced_motion
    assert "animation: none" in reduced_motion
    assert "@media (forced-colors: active)" in css


def relative_luminance(hex_color: str) -> float:
    channels = [int(hex_color[index : index + 2], 16) / 255 for index in (1, 3, 5)]
    linear = [
        value / 12.92
        if value <= 0.04045
        else ((value + 0.055) / 1.055) ** 2.4
        for value in channels
    ]
    return 0.2126 * linear[0] + 0.7152 * linear[1] + 0.0722 * linear[2]


def contrast_ratio(first: str, second: str) -> float:
    light, dark = sorted(
        (relative_luminance(first), relative_luminance(second)),
        reverse=True,
    )
    return (light + 0.05) / (dark + 0.05)


def test_primary_color_tokens_meet_contrast_contract():
    css = Path("app/static/css/style.css").read_text(encoding="utf-8").lower()
    text_pairs = (
        ("#2d2d3a", "#f5f0e8"),
        ("#2d2d3a", "#fffdf9"),
        ("#626274", "#fffdf9"),
        ("#57436c", "#fffdf9"),
        ("#f5f0e8", "#1e1e24"),
        ("#c5bdcc", "#292932"),
        ("#d9c5f1", "#292932"),
    )
    for foreground, background in text_pairs:
        assert foreground in css
        assert background in css
        assert contrast_ratio(foreground, background) >= 4.5

    assert contrast_ratio("#67547d", "#fffdf9") >= 3
    assert contrast_ratio("#d4c0ee", "#292932") >= 3