/**
 * SSRF Guard — prevents tasks from targeting internal/private addresses.
 * Used when creating scheduled tasks to ensure webhooks only hit allowed targets.
 */

const BLOCKED_HOSTS = new Set([
  'localhost',
  'nftcache',
  'schedy',
  'ntfy',
  'frontend',
  'web',
  'redis',
  'db',
  'postgres',
  'mysql',
  'mongo',
]);

const BLOCKED_HEADERS = new Set([
  'host',
  'content-length',
  'transfer-encoding',
  'connection',
  'upgrade',
  'proxy-authorization',
  'proxy-authenticate',
]);

export function isAllowedUrl(urlStr: string): { ok: true } | { ok: false; reason: string } {
  let parsed: URL;
  try {
    parsed = new URL(urlStr);
  } catch {
    return { ok: false, reason: 'Invalid URL' };
  }

  // Enforce HTTPS in production; allow HTTP only for localhost dev
  const isDev = process.env.NODE_ENV === 'development';
  if (parsed.protocol !== 'https:' && !(isDev && parsed.hostname === 'localhost')) {
    return { ok: false, reason: 'URL must use HTTPS' };
  }

  const hostname = parsed.hostname.toLowerCase();

  // Block internal Docker / service hostnames
  if (BLOCKED_HOSTS.has(hostname)) {
    return { ok: false, reason: 'Blocked internal hostname' };
  }

  // Block IPv4 private/reserved ranges
  const ipv4Match = hostname.match(/^(\d{1,3})\.(\d{1,3})\.(\d{1,3})\.(\d{1,3})$/);
  if (ipv4Match) {
    const octets = ipv4Match.slice(1).map(Number);
    if (octets.some((o) => o > 255)) {
      return { ok: false, reason: 'Invalid IP address' };
    }
    const [a, b, c, d] = octets;
    // 10.0.0.0/8
    if (a === 10) return { ok: false, reason: 'Private IP range' };
    // 172.16.0.0/12
    if (a === 172 && b >= 16 && b <= 31) return { ok: false, reason: 'Private IP range' };
    // 192.168.0.0/16
    if (a === 192 && b === 168) return { ok: false, reason: 'Private IP range' };
    // 127.0.0.0/8
    if (a === 127) return { ok: false, reason: 'Loopback IP' };
    // 169.254.0.0/16 (link-local)
    if (a === 169 && b === 254) return { ok: false, reason: 'Link-local IP' };
    // 0.0.0.0/8
    if (a === 0) return { ok: false, reason: 'Reserved IP' };
  }

  // Block IPv6 loopback / private indicators
  if (hostname === '::1' || hostname === '::' || hostname.startsWith('fe80:') || hostname.startsWith('fc') || hostname.startsWith('fd')) {
    return { ok: false, reason: 'IPv6 private/loopback' };
  }

  // Block metadata endpoints
  if (hostname === '169.254.169.254') {
    return { ok: false, reason: 'Cloud metadata endpoint' };
  }

  return { ok: true };
}

export function sanitizeHeaders(headers: Record<string, string>): Record<string, string> {
  const out: Record<string, string> = {};
  for (const [k, v] of Object.entries(headers)) {
    const lower = k.toLowerCase();
    if (!BLOCKED_HEADERS.has(lower)) {
      out[k] = v;
    }
  }
  return out;
}