/**
 * @module mcp-server/tools/dns
 * MCP Tool: DNS intelligence — rDNS, delegation checks, WHOIS lookups.
 *
 * Provides DNS-related network intelligence using DNS-over-HTTPS resolution,
 * delegation verification, and WHOIS queries.
 */

import { z } from "zod";

// ── Tool Schemas ─────────────────────────────────────────

/** Input schema for reverse DNS lookup */
export const reverseDnsSchema = z.object({
  ips: z
    .array(z.string())
    .min(1)
    .max(100)
    .describe("IP addresses to look up (max 100)"),
  verifyForward: z
    .boolean()
    .optional()
    .default(true)
    .describe("Verify forward-confirmed reverse DNS (FCrDNS)"),
});

/** Input schema for delegation check */
export const delegationCheckSchema = z.object({
  domain: z
    .string()
    .describe("Domain to check delegation for (e.g., 'cloudflare.com')"),
  checkDnssec: z
    .boolean()
    .optional()
    .default(true)
    .describe("Include DNSSEC validation check"),
});

/** Input schema for WHOIS lookup */
export const whoisLookupSchema = z.object({
  resource: z
    .string()
    .describe("IP address, prefix, ASN, or domain to look up"),
});

// ── Result Types ─────────────────────────────────────────

/** Reverse DNS result for a single IP */
export interface ReverseDnsEntry {
  readonly ip: string;
  readonly hostname: string | null;
  readonly forwardConfirmed: boolean;
  readonly inferredOrg: string | null;
}

/** Reverse DNS batch result */
export interface ReverseDnsResult {
  readonly entries: ReadonlyArray<ReverseDnsEntry>;
  readonly resolvedCount: number;
  readonly totalCount: number;
  readonly fcrdnsPassCount: number;
}

/** Delegation check result */
export interface DelegationCheckResult {
  readonly domain: string;
  readonly nameservers: ReadonlyArray<{
    readonly hostname: string;
    readonly ipv4: ReadonlyArray<string>;
    readonly ipv6: ReadonlyArray<string>;
    readonly responsive: boolean;
  }>;
  readonly dnssec: {
    readonly enabled: boolean;
    readonly valid: boolean;
    readonly algorithm: string | null;
    readonly dsRecordCount: number;
  };
  readonly glueRecords: boolean;
  readonly registrar: string | null;
  readonly issues: ReadonlyArray<string>;
  readonly recommendations: ReadonlyArray<string>;
}

/** WHOIS result */
export interface WhoisResult {
  readonly resource: string;
  readonly resourceType: "ip" | "asn" | "domain";
  readonly registrant: string;
  readonly organization: string;
  readonly country: string;
  readonly registrar: string;
  readonly creationDate: string;
  readonly expirationDate: string;
  readonly abuseContact: string;
  readonly networkName: string | null;
  readonly networkRange: string | null;
  readonly rir: string | null;
}

// ── Tool Handlers ────────────────────────────────────────

/**
 * Perform reverse DNS lookups for one or more IP addresses.
 *
 * Resolves each IP to its PTR record and optionally verifies that
 * the resulting hostname resolves back to the original IP (FCrDNS).
 *
 * @param input - Validated lookup parameters
 * @returns Batch reverse DNS results
 *
 * @example
 * ```
 * > Reverse DNS for the hops in a traceroute to identify ASes
 *
 * Returns: Hostname and organization for each IP, with FCrDNS verification.
 * ```
 */
export async function handleReverseDns(
  input: z.infer<typeof reverseDnsSchema>
): Promise<ReverseDnsResult> {
  // TODO: Use DNS client for batch reverse lookups
  // TODO: Optionally verify FCrDNS for each result
  // TODO: Infer organization from hostname patterns

  return {
    entries: input.ips.map((ip) => ({
      ip,
      hostname: null,     // TODO: Resolve via DNS client
      forwardConfirmed: false,
      inferredOrg: null,
    })),
    resolvedCount: 0,
    totalCount: input.ips.length,
    fcrdnsPassCount: 0,
  };
}

/**
 * Check DNS delegation for a domain.
 *
 * Verifies nameserver configuration, DNSSEC status, glue records,
 * and identifies potential delegation issues.
 *
 * @param input - Validated check parameters
 * @returns Delegation check result with issues and recommendations
 */
export async function handleDelegationCheck(
  input: z.infer<typeof delegationCheckSchema>
): Promise<DelegationCheckResult> {
  // TODO: Query NS records for the domain via DNS client
  // TODO: Resolve each NS to IPs and check responsiveness
  // TODO: Check DNSSEC (DS records, DNSKEY, signature validity)
  // TODO: Verify glue records are present and correct
  // TODO: Identify issues (lame delegation, missing glue, DNSSEC problems)

  return {
    domain: input.domain,
    nameservers: [],
    dnssec: {
      enabled: false,
      valid: false,
      algorithm: null,
      dsRecordCount: 0,
    },
    glueRecords: false,
    registrar: null,
    issues: [],
    recommendations: [
      "Enable DNSSEC for improved domain security",
      "Ensure at least two nameservers in different networks",
      "Configure both IPv4 and IPv6 glue records",
    ],
  };
}

/**
 * Perform a WHOIS lookup for an IP, ASN, or domain.
 *
 * @param input - Validated lookup parameters
 * @returns Structured WHOIS information
 */
export async function handleWhoisLookup(
  input: z.infer<typeof whoisLookupSchema>
): Promise<WhoisResult> {
  // TODO: Use DNS client / node-whois for WHOIS query
  // TODO: Detect resource type (IP, ASN, domain)
  // TODO: Parse raw WHOIS text into structured fields

  return {
    resource: input.resource,
    resourceType: "domain", // TODO: Auto-detect
    registrant: "",
    organization: "",
    country: "",
    registrar: "",
    creationDate: "",
    expirationDate: "",
    abuseContact: "",
    networkName: null,
    networkRange: null,
    rir: null,
  };
}
