"""B22 — Cross-Domain-Legal-Doc-Detector.

Erkennt: vertragsrelevante Dokumente (AGB, DSE, Widerrufsbelehrung,
Nutzungsbedingungen) liegen auf einer anderen Second-Level-Domain als
die Site selbst. Beispiel Elli/LogPay: AGB von Elli (elli.eco) liegt
auf docs.logpay.de.

Norm-Argument:
  - DSGVO Art. 28: das Hosten von Vertragsdokumenten durch einen
    Dritten ist Auftragsverarbeitung — AVV-Pflicht.
  - DSGVO Art. 13 Abs. 1 lit. e: Empfänger / Auftragsverarbeiter
    müssen in der DSE benannt sein.
  - Vertragsrechtlich: AGB-Verbindlichkeit wackelig wenn der
    Dokumenten-Host wechselt — was passiert wenn der externe Host
    den Pfad ändert (Cool-URLs-Problem § 312i BGB).

Severity:
  - HIGH bei AGB / Widerrufsbelehrung (vertragsrelevant)
  - MEDIUM bei DSE / Nutzungsbedingungen
  - INFO bei Cookie-Policy / Impressum (eher Best-Practice)
"""

from __future__ import annotations

import logging
from urllib.parse import urlparse

logger = logging.getLogger(__name__)


_COMPOUND_TLDS = {
    "co.uk", "co.jp", "co.nz", "co.kr", "co.za", "co.in",
    "com.au", "com.br", "com.mx", "com.tr", "com.sg",
}


_SEVERITY_BY_DOC = {
    "agb": "HIGH",
    "widerruf": "HIGH",
    "dse": "MEDIUM",
    "nutzungsbedingungen": "MEDIUM",
    "cookie": "INFO",
    "impressum": "INFO",
    "social_media": "INFO",
}


def _sld(host: str) -> str:
    """Extract the second-level domain. Handles compound TLDs."""
    if not host:
        return ""
    host = host.lower().lstrip("www.")
    parts = host.split(".")
    if len(parts) < 2:
        return host
    if len(parts) >= 3 and ".".join(parts[-2:]) in _COMPOUND_TLDS:
        return parts[-3]
    return parts[-2]


def _site_origin_sld(state: dict) -> str:
    """Find the primary site SLD by counting most common host in
    submitted URLs."""
    counter: dict[str, int] = {}
    for e in (state.get("doc_entries") or []):
        url = (e.get("url") or "").strip()
        if not url or "://" not in url:
            continue
        # Skip auto-discovered docs (they may already be cross-domain
        # by design — we want the USER's stated origin).
        if e.get("auto_discovered"):
            continue
        try:
            host = urlparse(url).netloc
            sld = _sld(host)
            if sld:
                counter[sld] = counter.get(sld, 0) + 1
        except Exception:
            continue
    if not counter:
        # Fallback: use any URL
        for e in (state.get("doc_entries") or []):
            url = (e.get("url") or "").strip()
            if url and "://" in url:
                return _sld(urlparse(url).netloc)
        return ""
    return max(counter, key=counter.get)


def _collect_audit_urls(state: dict) -> list[tuple[str, str]]:
    """Sammle (doc_type, url) aus BEIDEN Quellen — state.doc_entries
    (nach Discovery) UND req.documents (USER-Original-Input). Discovery
    kann Original-URLs verlieren (PDF-Fetch-Fail, Auto-Reclassify), aber
    Cross-Domain-Hosting ist juristisch unabhängig vom Text-Inhalt
    der Datei.
    """
    seen: set[tuple[str, str]] = set()
    out: list[tuple[str, str]] = []
    for e in (state.get("doc_entries") or []):
        url = (e.get("url") or "").strip()
        doc_type = (e.get("doc_type") or "").lower()
        if url and doc_type and (doc_type, url) not in seen:
            seen.add((doc_type, url))
            out.append((doc_type, url))
        # rejected_url ist die Original-URL die Discovery rejected hat
        rej = (e.get("rejected_url") or "").strip()
        if rej and doc_type and (doc_type, rej) not in seen:
            seen.add((doc_type, rej))
            out.append((doc_type, rej))
    # Fallback: req.documents — USER hat sie explizit eingegeben
    req = state.get("req")
    if req is not None:
        for d in getattr(req, "documents", []) or []:
            url = (getattr(d, "url", "") or "").strip()
            doc_type = (getattr(d, "doc_type", "") or "").lower()
            if url and doc_type and (doc_type, url) not in seen:
                seen.add((doc_type, url))
                out.append((doc_type, url))
    return out


def check_cross_domain_docs(state: dict) -> list[dict]:
    """Emit findings for doc-URLs whose host has a different SLD
    than the site origin."""
    primary = _site_origin_sld(state)
    if not primary:
        logger.info("B22 cross-domain: kein primary SLD ermittelbar")
        return []
    findings: list[dict] = []
    audit_urls = _collect_audit_urls(state)
    logger.info("B22 cross-domain: primary=%s, prüfe %d URL(s)",
                primary, len(audit_urls))
    emitted_keys: set[tuple[str, str]] = set()
    for doc_type, url in audit_urls:
        if "://" not in url:
            continue
        try:
            host = urlparse(url).netloc
            url_sld = _sld(host)
        except Exception:
            continue
        if not url_sld or url_sld == primary:
            continue
        # Dedup pro (doc_type, host_sld) damit rejected_url + url nicht
        # doppelt gemeldet werden
        e_key = (doc_type, url_sld)
        if e_key in emitted_keys:
            continue
        emitted_keys.add(e_key)
        # Cross-Domain detected
        severity = _SEVERITY_BY_DOC.get(doc_type, "MEDIUM")
        doc_label = {
            "agb": "Allgemeine Geschäftsbedingungen",
            "widerruf": "Widerrufsbelehrung",
            "dse": "Datenschutzerklärung",
            "nutzungsbedingungen": "Nutzungsbedingungen",
            "cookie": "Cookie-Richtlinie",
            "impressum": "Impressum",
            "social_media": "Social-Media-Hinweise",
        }.get(doc_type, doc_type.upper())
        findings.append({
            "check_id": "CROSS-DOMAIN-DOC-001",
            "severity": severity,
            "severity_reason": "third_party_hosted",
            "doc_type": doc_type,
            "site_sld": primary,
            "host_sld": url_sld,
            "url": url,
            "title": (
                f"{doc_label} liegt auf Drittanbieter-Domain "
                f"({host}) statt {primary}"
            ),
            "norm": (
                "DSGVO Art. 28 (AVV) + Art. 13 Abs. 1 lit. e (Empfänger) + "
                "§ 312i BGB (Cool-URLs / Vertragspflicht)"
            ),
            "evidence": (
                f"Site-Origin: {primary} · "
                f"Dokument gehostet auf: {host} · "
                f"URL: {url[:120]}"
            ),
            "recommended_action": (
                f"Entweder das Dokument auf eigene Domain ({primary}) "
                "migrieren ODER (a) den externen Host {host} als "
                "Auftragsverarbeiter in der DSE benennen, (b) AVV "
                "abschließen, (c) sicherstellen dass URL-Stabilität "
                f"vertraglich garantiert ist (§ 312i BGB Cool-URL-Pflicht)."
            ),
        })
    if findings:
        logger.info("B22 cross-domain: %d finding(s)", len(findings))
    return findings