import * as net from "node:net";
import { domainToASCII } from "node:url";

/**
 * Looks up when a domain registration expires. RDAP (the JSON successor to WHOIS) is used wherever the TLD
 * publishes an RDAP server in IANA's bootstrap file. Plenty of TLDs don't — notably .se, .nu, .de, .io and .eu —
 * so those fall back to classic WHOIS on port 43, found through IANA's own referral, and the expiry line is
 * parsed out of the free-text answer. Only the expiry date and registrar are kept; nothing else about the
 * registrant is read or stored.
 */

export type LookupResult =
  | { ok: true; domain: string; expiresAt: string | null; registrar: string | null; source: "rdap" | "whois" }
  /** unsupported: no RDAP or WHOIS server for the TLD. not_found: the registry has no such domain. error: couldn't ask (network, rate limit, garbled answer) — says nothing about whether it exists. */
  | { ok: false; reason: "unsupported" | "not_found" | "error"; message: string };

export interface LookupDeps {
  fetchJson: (url: string) => Promise<{ status: number; json: any }>;
  whoisQuery: (server: string, query: string) => Promise<string>;
  now: () => number;
}

const BOOTSTRAP_URL = "https://data.iana.org/rdap/dns.json";
const BOOTSTRAP_TTL_MS = 24 * 60 * 60 * 1000;
const USER_AGENT = "homelab-manager (domain expiry check)";

export const defaultDeps: LookupDeps = {
  async fetchJson(url) {
    const res = await fetch(url, {
      headers: { Accept: "application/rdap+json, application/json", "User-Agent": USER_AGENT },
      redirect: "follow",
      signal: AbortSignal.timeout(15_000),
    });
    const text = await res.text();
    let json: any = null;
    try {
      json = text ? JSON.parse(text) : null;
    } catch {
      // not JSON (an HTML error page, say)
    }
    return { status: res.status, json };
  },
  whoisQuery(server, query) {
    return new Promise((resolve, reject) => {
      const socket = net.connect({ host: server, port: 43 });
      let out = "";
      socket.setTimeout(12_000, () => {
        socket.destroy();
        reject(new Error(`Timed out asking ${server}`));
      });
      socket.on("connect", () => socket.write(`${query}\r\n`));
      socket.on("data", (chunk) => {
        out += chunk;
        if (out.length > 200_000) socket.destroy(); // a WHOIS answer is a few KB; anything larger isn't one
      });
      socket.on("end", () => resolve(out));
      socket.on("close", () => resolve(out));
      socket.on("error", reject);
    });
  },
  now: () => Date.now(),
};

// ─── Names ──────────────────────────────────────────────────────────────────

/** Lowercased ASCII (punycode) form of a domain, or null if it isn't a plausible registrable name. */
export function normalizeDomain(input: string): string | null {
  const trimmed = input.trim().toLowerCase().replace(/\.$/, "");
  if (!trimmed) return null;
  // domainToASCII quietly drops anything after a "/" or "?" — a pasted URL would be accepted as its host. Refuse instead.
  if (/[\s/\:@?#]/.test(trimmed)) return null;
  const ascii = domainToASCII(trimmed);
  if (!ascii || ascii.length > 253) return null;
  const labels = ascii.split(".");
  if (labels.length < 2) return null;
  if (!labels.every((l) => /^[a-z0-9]([a-z0-9-]{0,61}[a-z0-9])?$/.test(l))) return null;
  return ascii;
}

/** The name itself, then each parent with one fewer label, stopping at two labels: "a.b.example.se" → a.b.example.se, b.example.se, example.se. */
export function candidateNames(domain: string): string[] {
  const labels = domain.split(".");
  const out: string[] = [];
  for (let i = 0; i <= labels.length - 2; i++) out.push(labels.slice(i).join("."));
  return out;
}

function tldOf(domain: string): string {
  return domain.slice(domain.lastIndexOf(".") + 1);
}

// ─── RDAP ───────────────────────────────────────────────────────────────────

let bootstrapCache: { at: number; byTld: Map<string, string> } | null = null;

async function rdapBase(tld: string, deps: LookupDeps): Promise<string | null> {
  if (!bootstrapCache || deps.now() - bootstrapCache.at > BOOTSTRAP_TTL_MS) {
    try {
      const { status, json } = await deps.fetchJson(BOOTSTRAP_URL);
      if (status !== 200 || !Array.isArray(json?.services)) throw new Error(`HTTP ${status}`);
      const byTld = new Map<string, string>();
      for (const [tlds, urls] of json.services as [string[], string[]][]) {
        const url = urls.find((u) => u.startsWith("https://")) ?? urls[0];
        if (url) for (const t of tlds) byTld.set(t.toLowerCase(), url.endsWith("/") ? url : `${url}/`);
      }
      bootstrapCache = { at: deps.now(), byTld };
    } catch (err) {
      // A stale list is far better than none — it changes rarely.
      if (!bootstrapCache) throw new Error(`Couldn't load IANA's RDAP server list: ${err instanceof Error ? err.message : err}`);
    }
  }
  return bootstrapCache!.byTld.get(tld) ?? null;
}

function rdapFromJson(json: any, domain: string): LookupResult {
  const events: { eventAction?: string; eventDate?: string }[] = Array.isArray(json?.events) ? json.events : [];
  const expiry = events.find((e) => /^expiration$|^expiry$/i.test(e.eventAction ?? ""))?.eventDate;
  const time = expiry ? Date.parse(expiry) : NaN;
  const registrarEntity = (Array.isArray(json?.entities) ? json.entities : []).find((e: any) => (e.roles ?? []).includes("registrar"));
  const fn = registrarEntity?.vcardArray?.[1]?.find((v: unknown[]) => v[0] === "fn")?.[3];
  return {
    ok: true,
    domain,
    expiresAt: Number.isFinite(time) ? new Date(time).toISOString().slice(0, 10) : null,
    registrar: typeof fn === "string" && fn ? fn : null,
    source: "rdap",
  };
}

// ─── WHOIS ──────────────────────────────────────────────────────────────────

const whoisServerCache = new Map<string, { at: number; server: string | null }>();

async function whoisServerFor(tld: string, deps: LookupDeps): Promise<string | null> {
  const cached = whoisServerCache.get(tld);
  if (cached && deps.now() - cached.at < BOOTSTRAP_TTL_MS) return cached.server;
  const answer = await deps.whoisQuery("whois.iana.org", tld);
  const server = /^whois:\s*(\S+)/im.exec(answer)?.[1] ?? null;
  whoisServerCache.set(tld, { at: deps.now(), server });
  return server;
}

const MONTHS: Record<string, number> = { jan: 0, feb: 1, mar: 2, apr: 3, may: 4, jun: 5, jul: 6, aug: 7, sep: 8, oct: 9, nov: 10, dec: 11 };

/** The date formats registries actually use, as a YYYY-MM-DD string (or null). */
export function parseWhoisDate(raw: string): string | null {
  const s = raw.trim();
  let m = /^(\d{4})[-./](\d{1,2})[-./](\d{1,2})/.exec(s); // 2031-03-09, 2031.03.09, 2027-08-13T04:00:00Z
  if (m) return ymd(Number(m[1]), Number(m[2]) - 1, Number(m[3]));
  m = /^(\d{1,2})[-\s]([A-Za-z]{3})[a-z]*[-\s](\d{4})/.exec(s); // 13-Aug-2027, 13 August 2027
  if (m && MONTHS[m[2].toLowerCase()] !== undefined) return ymd(Number(m[3]), MONTHS[m[2].toLowerCase()], Number(m[1]));
  m = /^(\d{1,2})\.(\d{1,2})\.(\d{4})/.exec(s); // 13.08.2027
  if (m) return ymd(Number(m[3]), Number(m[2]) - 1, Number(m[1]));
  return null;
}

function ymd(y: number, mo: number, d: number): string | null {
  const date = new Date(Date.UTC(y, mo, d));
  if (date.getUTCFullYear() !== y || date.getUTCMonth() !== mo || date.getUTCDate() !== d) return null;
  return date.toISOString().slice(0, 10);
}

const EXPIRY_LINE = /^\s*(?:registry\s+expiry\s+date|registrar\s+registration\s+expiration\s+date|expiration\s+date|expiry\s+date|expire\s+date|expires(?:\s+on)?|expire|paid-till|renewal\s+date)\s*:\s*(.+?)\s*$/i;
const NOT_FOUND = /no match|not found|no entries found|no data found|domain not found|status:\s*(?:free|available)|is free|no object found/i;

export function parseWhois(text: string, domain: string): LookupResult {
  let expiresAt: string | null = null;
  for (const line of text.split(/\r?\n/)) {
    const m = EXPIRY_LINE.exec(line);
    if (m) {
      expiresAt = parseWhoisDate(m[1]);
      if (expiresAt) break;
    }
  }
  const registrar = /^\s*registrar(?:\s+name)?\s*:\s*(.+?)\s*$/im.exec(text)?.[1] ?? null;
  if (expiresAt) return { ok: true, domain, expiresAt, registrar, source: "whois" };
  if (NOT_FOUND.test(text)) return { ok: false, reason: "not_found", message: `${domain} isn't registered.` };
  // A server pushing back on us isn't the same as a registry that doesn't publish expiry dates.
  if (/quota|rate.?limit|too many|exceeded|access denied|blocked|try again/i.test(text)) {
    return { ok: false, reason: "error", message: `The WHOIS server for ${domain} refused the query (rate limited?). It will be retried.` };
  }
  // Answered, but with no expiry we can read (e.g. .de and .eu don't publish one).
  return { ok: true, domain, expiresAt: null, registrar, source: "whois" };
}

// ─── Lookup ─────────────────────────────────────────────────────────────────

/** Looks up exactly this name (no parent walking). */
export async function lookupRegistration(domain: string, deps: LookupDeps = defaultDeps): Promise<LookupResult> {
  const tld = tldOf(domain);
  try {
    const base = await rdapBase(tld, deps);
    if (base) {
      const { status, json } = await deps.fetchJson(`${base}domain/${encodeURIComponent(domain)}`);
      if (status === 200 && json) return rdapFromJson(json, domain);
      if (status === 404) return { ok: false, reason: "not_found", message: `${domain} isn't registered.` };
      return { ok: false, reason: "error", message: `The RDAP server for .${tld} answered HTTP ${status}.` };
    }

    const server = await whoisServerFor(tld, deps);
    if (!server) return { ok: false, reason: "unsupported", message: `.${tld} has no public RDAP or WHOIS server to ask.` };
    return parseWhois(await deps.whoisQuery(server, domain), domain);
  } catch (err) {
    return { ok: false, reason: "error", message: err instanceof Error ? err.message : String(err) };
  }
}

/**
 * Finds the registration a name belongs to by trying it and then its parents ("lab.example.se" → "example.se"),
 * so a DNS zone that's a subdomain still resolves to the domain that actually expires — without needing a
 * public-suffix list. A transient error anywhere means we can't conclude "not registered".
 */
export async function resolveRegistration(name: string, deps: LookupDeps = defaultDeps): Promise<LookupResult> {
  let sawError: LookupResult | null = null;
  let sawNotFound: LookupResult | null = null;
  let firstUnsupported: LookupResult | null = null;
  for (const candidate of candidateNames(name)) {
    const result = await lookupRegistration(candidate, deps);
    if (result.ok) return result;
    if (result.reason === "unsupported") {
      // Every candidate shares the TLD, so nothing further up can be answered either.
      firstUnsupported = result;
      break;
    }
    if (result.reason === "error") sawError = sawError ?? result;
    else sawNotFound = sawNotFound ?? result;
  }
  return sawError ?? firstUnsupported ?? sawNotFound ?? { ok: false, reason: "not_found", message: `${name} isn't registered.` };
}

/** For tests: forget cached RDAP/WHOIS server lists. */
export function resetLookupCaches(): void {
  bootstrapCache = null;
  whoisServerCache.clear();
}