"""Campaign tracked homepage links (UTM) plus optional piha.li short URLs.

utm_source comes from UTM_SOURCE env, else a slug of SITE_NAME — never a
hardcoded client name. Shared by email_sms and directmail.
"""

from __future__ import annotations

import html
import re
from urllib.parse import urlencode

from django.conf import settings
from django.urls import NoReverseMatch, reverse

from contacts.models import Channel
from core.shortener import resolve_display_url

UTM_CAMPAIGN_SLUG_MAX = 80
_UTM_ANCHOR_RE = re.compile(r"(<a\b[^>]*>)(.*?)(</a>)", re.IGNORECASE | re.DOTALL)
_SHORT_TEXT_URL_RE = re.compile(
    r"https?://(?:(?:www\.)?(?:beta\.)?piha\.li|(?:127\.0\.0\.1|localhost):\d+)"
    r"/[a-z0-9]{4,8}",
    re.IGNORECASE,
)


def campaign_utm_slug(name: str) -> str:
    """Lowercase hyphenated slug (utm_campaign / utm_source)."""
    slug = re.sub(r"[^a-z0-9]+", "-", (name or "").strip().lower())
    slug = re.sub(r"-{2,}", "-", slug).strip("-")
    return (slug or "campaign")[:UTM_CAMPAIGN_SLUG_MAX]


def campaign_utm_source() -> str:
    """Brand slug for utm_source. Override with UTM_SOURCE env."""
    explicit = (getattr(settings, "UTM_SOURCE", None) or "").strip()
    if explicit:
        return campaign_utm_slug(explicit)
    return campaign_utm_slug(getattr(settings, "SITE_NAME", None) or "campaign")


def public_site_base_url() -> str:
    """Public homepage used as the UTM landing URL."""
    return (getattr(settings, "PUBLIC_SITE_URL", None) or "").rstrip("/")


def public_site_link_label() -> str:
    """Visible email-link text (host), or SITE_NAME in local/dev."""
    host = (
        public_site_base_url()
        .replace("https://", "")
        .replace("http://", "")
        .split("/")[0]
    )
    brand = (getattr(settings, "SITE_NAME", None) or "").strip() or "our website"
    if (
        not host
        or host.startswith("127.")
        or host.startswith("localhost")
        or host.startswith("0.0.0.0")
    ):
        return brand
    return host


def build_campaign_utm_url(
    *,
    name: str,
    medium: str,
    base_url: str = "",
) -> str:
    """Homepage URL with utm_source / utm_medium / utm_campaign."""
    base = (base_url or public_site_base_url()).rstrip("/")
    channel = (medium or "").strip().lower()
    if channel not in Channel.values:
        channel = Channel.EMAIL
    query = urlencode(
        {
            "utm_source": campaign_utm_source(),
            "utm_medium": channel,
            "utm_campaign": campaign_utm_slug(name),
        }
    )
    return f"{base}/?{query}"


def campaign_shortener_ref(
    *,
    campaign_id=None,
    user_id=None,
    medium: str = "",
    name: str = "",
) -> str:
    """external_ref for the shortener (max 64). Prefer campaign UUID."""
    if campaign_id:
        return str(campaign_id)[:64]
    slug = campaign_utm_slug(name)[:40]
    ch = (medium or "email").strip().lower()[:8]
    uid = "" if user_id is None else str(user_id)
    return f"p{uid}-{ch}-{slug}"[:64]


def resolve_campaign_tracked_url(
    *,
    name: str,
    medium: str,
    campaign_id=None,
    user_id=None,
    shorten: bool = True,
) -> tuple[str, str]:
    """Return (long UTM URL, display URL). Display is short when mint works."""
    target = build_campaign_utm_url(name=name, medium=medium)
    if not shorten:
        return target, target
    display = resolve_display_url(
        target,
        title=f"{(name or 'campaign').strip()} ({medium})"[:200],
        external_ref=campaign_shortener_ref(
            campaign_id=campaign_id, user_id=user_id, medium=medium, name=name
        ),
    )
    return target, display


def _utm_text_url_re() -> re.Pattern[str]:
    return re.compile(
        r"https?://[^\s<>\"]+utm_source="
        + re.escape(campaign_utm_source())
        + r"[^\s<>\"]*",
        re.IGNORECASE,
    )


def _is_our_utm_anchor(attrs: str) -> bool:
    lower = attrs.lower()
    source = campaign_utm_source().lower()
    return "data-campaign-utm" in lower or f"utm_source={source}" in lower


def ensure_campaign_utm_in_html(body: str, url: str, label: str) -> str:
    """Insert or refresh the tracked <a> in an HTML (email) body."""
    href = html.escape(url, quote=True)
    label_html = html.escape(label)
    replaced = False

    def _repl(match: re.Match[str]) -> str:
        nonlocal replaced
        if replaced or not _is_our_utm_anchor(match.group(1)):
            return match.group(0)
        replaced = True
        inner = match.group(2) if (match.group(2) or "").strip() else label_html
        return f'<a href="{href}" data-campaign-utm="1">{inner}</a>'

    out = _UTM_ANCHOR_RE.sub(_repl, body or "")
    if replaced:
        return out
    anchor = f'<a href="{href}" data-campaign-utm="1">{label_html}</a>'
    text = (body or "").rstrip()
    if text:
        return f"{text}\n<p>{anchor}</p>"
    return f"<p>{anchor}</p>"


def ensure_campaign_utm_in_text(body: str, url: str) -> str:
    """Insert or refresh the tracked URL in a plain-text (SMS) body."""
    raw = body or ""
    utm_re = _utm_text_url_re()
    if utm_re.search(raw):
        return utm_re.sub(url, raw, count=1)
    if _SHORT_TEXT_URL_RE.search(raw):
        return _SHORT_TEXT_URL_RE.sub(url, raw, count=1)
    text = raw.rstrip()
    return f"{text}\n\n{url}" if text else url


def ensure_campaign_utm_link(
    body: str,
    *,
    name: str,
    medium: str,
    html: bool,
    campaign_id=None,
    shorten: bool | None = None,
) -> str:
    """Keep a tracked site link in the body, matching campaign name + channel."""
    do_shorten = bool(campaign_id) if shorten is None else shorten
    _target, url = resolve_campaign_tracked_url(
        name=name,
        medium=medium,
        campaign_id=campaign_id,
        shorten=do_shorten,
    )
    if html:
        return ensure_campaign_utm_in_html(body, url, public_site_link_label())
    return ensure_campaign_utm_in_text(body, url)


def postcard_designer_url() -> str:
    try:
        return reverse("directmail:postcard_designer")
    except NoReverseMatch:
        return ""


def utm_panel_context(
    *,
    campaign=None,
    live: bool = False,
    medium: str = "",
) -> dict:
    """Template context for `_utm_link_panel.html`."""
    name = getattr(campaign, "name", "") or ""
    ch = medium or getattr(campaign, "channel", "") or ""
    display = ""
    if campaign is not None:
        _target, display = resolve_campaign_tracked_url(
            name=name,
            medium=ch,
            campaign_id=getattr(campaign, "pk", None),
            shorten=True,
        )
    try:
        shorten_url = reverse("campaign_short_link")
    except NoReverseMatch:
        shorten_url = ""
    return {
        "utm_base_url": public_site_base_url(),
        "utm_link_label": public_site_link_label(),
        "utm_source": campaign_utm_source(),
        "utm_shorten_url": shorten_url,
        "utm_url": display,
        "utm_live": live,
        "utm_medium": ch,
        "utm_campaign_name": name,
        "utm_campaign_id": str(getattr(campaign, "pk", "") or ""),
        "utm_postcard_designer_url": postcard_designer_url(),
    }