"""Magic-link delivery. SMTP when configured, dev log fallback otherwise.

Mail design follows the web branding (see frontend/src/theme.ts):
kirchenblau header, serif headline, white card on paper background.
Email-safe by construction: table layout, inline styles only, system
fonts, no external images (many clients block them / track opens).
"""

from __future__ import annotations

import logging
from email.message import EmailMessage
from pathlib import Path

from jinja2 import Template

from app.settings import settings

logger = logging.getLogger(__name__)

# Brand palette (mirrors frontend/src/theme.ts kirchenblau).
BLUE = "#1d4a79"
BLUE_LIGHT = "#eef4fb"
INK = "#162f4c"
MUTED = "#5b6b7c"

_TEMPLATE_PATH = Path(__file__).resolve().parent / "templates" / "magic_link.html"
_template_cache: Template | None = None


def _template() -> Template:
    global _template_cache
    if _template_cache is None:
        _template_cache = Template(_TEMPLATE_PATH.read_text(encoding="utf-8"))
    return _template_cache


def magic_link(token: str) -> str:
    return f"{settings.frontend_url.rstrip('/')}/login?token={token}"


def _page(title: str, intro: str, button_label: str, button_url: str | None, note: str) -> str:
    """Branded HTML mail body (jinja template, byte-identical to the old f-string)."""
    return _template().render(
        title=title,
        intro=intro,
        button_label=button_label,
        button_url=button_url,
        note=note,
        blue=BLUE,
        blue_light=BLUE_LIGHT,
        ink=INK,
        muted=MUTED,
    )


def _send(message: EmailMessage) -> None:
    """Deliver via fastapi-mail (same never-raise contract at call sites)."""
    import asyncio

    from fastapi_mail import ConnectionConfig, FastMail, MessageSchema, MessageType

    config = ConnectionConfig(
        MAIL_USERNAME=settings.smtp_username,
        MAIL_PASSWORD=settings.smtp_password,
        MAIL_FROM=settings.mail_from or settings.contact_to or message["To"],
        MAIL_PORT=settings.smtp_port,
        MAIL_SERVER=settings.smtp_host,
        MAIL_STARTTLS=True,
        MAIL_SSL_TLS=False,
        USE_CREDENTIALS=bool(settings.smtp_username),
    )
    html = message.get_body(preferencelist=("html",))
    plain = message.get_body(preferencelist=("plain",))
    outgoing = MessageSchema(
        subject=str(message["Subject"]),
        recipients=[str(message["To"])],
        body=plain.get_content() if plain else "",
        html=html.get_content() if html else "",
        subtype=MessageType.html,
    )
    asyncio.run(FastMail(config).send_message(outgoing))


def _branded_mail(
    subject: str,
    to_email: str,
    headline: str,
    intro: str,
    button_label: str,
    button_url: str,
    note: str,
) -> EmailMessage:
    """Text + branded HTML alternative; the link is a real button."""
    message = EmailMessage()
    message["Subject"] = subject
    message["To"] = to_email
    message["From"] = settings.mail_from or settings.contact_to or to_email
    if settings.contact_to:
        message["Reply-To"] = settings.contact_to
    message.set_content(f"{headline}\n\n{intro}\n\n{button_label}:\n{button_url}\n\n{note}\n")
    # Email-safe HTML: tables + inline CSS; some clients strip <style>, so
    # the palette is inlined via the f-string constants above.
    message.add_alternative(_page(headline, intro, button_label, button_url, note), subtype="html")
    return message


def send_magic_link(to_email: str, link: str) -> bool:
    """Mail the login link. Returns False (logs instead) when SMTP is unset.

    Never raises: callers invoke it after committing (approve/bootstrap),
    so a delivery failure must not turn into a 500 — the token stays valid
    and the admin sees ``email_sent: false``.

    The plaintext link only ever appears here: service/api logging must
    never include tokens or session ids (see test_auth no-leak test).
    """
    if not settings.smtp_host:
        # Never log the link itself: without SMTP this fallback fires in
        # every environment, and logs are rarely as protected as mail.
        logger.info("SMTP not configured; dropping magic link for %s", to_email)
        return False
    message = _branded_mail(
        subject="Dein Login-Link für Kirche Einfach",
        to_email=to_email,
        headline="Anmeldung bei Kirche Einfach",
        intro=(
            "Klicke auf den Button, um dich anzumelden. Der Link ist "
            "15 Minuten gültig und funktioniert nur einmal."
        ),
        button_label="Jetzt anmelden",
        button_url=link,
        note=(
            "Falls du den Button nicht nutzen kannst, kopiere den Link "
            "aus der Textversion dieser E-Mail in deinen Browser. "
            "Diese E-Mail wurde angefordert — wenn du das warst, ist "
            "alles gut; sonst kannst du sie ignorieren."
        ),
    )
    try:
        _send(message)
    except Exception:  # noqa: BLE001 -- never-raise contract: delivery must not 500
        logger.warning("magic-link delivery failed for %s", to_email)
        return False
    logger.info("magic link mailed to %s", to_email)
    return True


def send_access_notification(request_id: str, name: str, email: str) -> bool:
    """Notify CONTACT_TO about a new access request (best effort)."""
    if not settings.smtp_host or not settings.contact_to:
        logger.info("new access request %s from %s <%s>", request_id, name, email)
        return False
    message = _branded_mail(
        subject=f"Neue Zugangsanfrage: {name}",
        to_email=settings.contact_to,
        headline="Neue Zugangsanfrage",
        intro=(
            f"{name} ({email}) hat Zugang angefordert und wartet auf Freigabe in der Verwaltung."
        ),
        button_label="In der Verwaltung prüfen",
        button_url=f"{settings.frontend_url.rstrip('/')}/app/admin",
        note="Diese Benachrichtigung geht an das Kontakt-Postfach.",
    )
    try:
        _send(message)
    except Exception:  # noqa: BLE001 -- best-effort notification, never raises
        logger.warning("access-request notification failed for %s", request_id)
        return False
    return True