"""HTTP-GET mit DNS-Rückfall für Health-Checks.

Der Resolver des Admin-Servers (Coolify/Docker) cacht „Name nicht gefunden“ für neue Hostnamen oft lange – obwohl der Name öffentlich
längst existiert. Schlägt die Auflösung fehl, fragen wir die Adresse per DNS-over-HTTPS (Cloudflare, dann Google) ab und verbinden uns
direkt zur IP (Host-Header + SNI = Hostname, Zertifikat wird normal geprüft).
"""
from __future__ import annotations

import socket
from urllib.parse import urlsplit

import httpx


def _is_dns_error(exc: BaseException) -> bool:
    seen = set()
    while exc is not None and id(exc) not in seen:
        seen.add(id(exc))
        if isinstance(exc, socket.gaierror):
            return True
        exc = exc.__cause__ or exc.__context__
    return False


def is_dns_failure_text(msg: str) -> bool:
    m = msg.lower()
    return "name or service not known" in m or "temporary failure in name resolution" in m or "nodename nor servname" in m or "gaierror" in m


def doh_resolve(host: str, timeout: float = 5.0) -> list[str]:
    for url in ("https://cloudflare-dns.com/dns-query", "https://dns.google/resolve"):
        try:
            r = httpx.get(url, params={"name": host, "type": "A"}, headers={"accept": "application/dns-json"}, timeout=timeout)
            ips = [a["data"] for a in r.json().get("Answer", []) if a.get("type") == 1]
            if ips:
                return ips
        except Exception:  # noqa: BLE001
            continue
    return []


def get_json(url: str, timeout: float = 8.0) -> tuple[int, dict]:
    """GET mit DNS-Rückfall → (status, json-dict oder {}). Bei Rückfall enthält das Dict `_dns_fallback: true`."""
    def parse(r):
        return r.status_code, (r.json() if r.headers.get("content-type", "").startswith("application/json") else {})
    try:
        return parse(httpx.get(url, timeout=timeout, follow_redirects=True))
    except httpx.ConnectError as exc:
        if not _is_dns_error(exc):
            raise
        parts = urlsplit(url)
        for ip in doh_resolve(parts.hostname or ""):
            try:
                r = httpx.get(f"{parts.scheme}://{ip}{parts.path or '/'}", headers={"Host": parts.hostname}, extensions={"sni_hostname": parts.hostname},
                              timeout=timeout, follow_redirects=True)
                status, body = parse(r)
                return status, {**body, "_dns_fallback": True}
            except Exception:  # noqa: BLE001
                continue
        raise