#!/usr/bin/env node
/**
 * HSD Zone Cache — on-demand query with SOA-based invalidation
 *
 * Instead of periodic dumps, this:
 *   1. Queries HSD tree root hash every N seconds
 *   2. If tree root changed → regenerate zone from HSD
 *   3. If unchanged → serve cached zone
 *   4. CoreDNS reads the cached zone file
 *
 * The zone file is ONLY written from HSD RPC data.
 * No manual edits. The sidechain IS the source of truth.
 *
 * Usage:
 *   node zone-cache.js
 *   # Runs as daemon, writes to /opt/noc/coredns/db.lthn.auto
 */

const fs = require('fs');
const { execFileSync } = require('child_process');

const HSD_URL = process.env.HSD_URL || 'http://127.0.0.1:14037';
const HSD_API_KEY = process.env.HSD_API_KEY || 'testkey';
const ZONE_FILE = process.env.ZONE_FILE || '/opt/noc/coredns/db.lthn.auto';
const CHECK_INTERVAL = parseInt(process.env.CHECK_INTERVAL || '15') * 1000;

// Known names to query — in production, scan the UTXO set
const KNOWN_NAMES = [
  'lethean', 'snider', 'darbs', 'charon', 'cladius',
  'explorer', 'testnet', 'trading', 'gateway', 'network',
  'monitor', 'storage', 'support', 'trade',
  'builder', 'develop', 'miners', 'relayer',
];

let lastTreeRoot = null;
let lastZone = null;

async function rpcHSD(method, params = []) {
  const auth = Buffer.from(`x:${HSD_API_KEY}`).toString('base64');
  const resp = await fetch(HSD_URL, {
    method: 'POST',
    headers: { 'Content-Type': 'application/json', 'Authorization': `Basic ${auth}` },
    body: JSON.stringify({ method, params }),
  });
  const data = await resp.json();
  if (data.error) throw new Error(data.error.message);
  return data.result;
}

async function getTreeRoot() {
  const info = await rpcHSD('getinfo');
  return { height: info.blocks, treeRoot: info.treeroot || 'unknown' };
}

async function generateZone(height) {
  const serial = `${new Date().toISOString().slice(0, 10).replace(/-/g, '')}${String(height).padStart(4, '0')}`;
  const lines = [
    `; .lthn zone — generated from HSD sidechain (height ${height})`,
    `; Generated: ${new Date().toISOString()}`,
    `; Source: ${HSD_URL} (READ-ONLY — do not edit this file)`,
    `; Invalidation: SOA changes when HSD tree root changes`,
    ``,
    `lthn. 300 IN SOA ns5.lthn.io. admin.lthn.io. ${serial} 3600 600 86400 300`,
    `lthn. 300 IN NS  ns5.lthn.io.`,
    `lthn. 300 IN NS  ns6.lthn.io.`,
    ``,
    `; === Records from HSD sidechain (source of truth) ===`,
  ];

  for (const name of KNOWN_NAMES) {
    try {
      const resource = await rpcHSD('getnameresource', [name]);
      if (resource && resource.records && resource.records.length > 0) {
        lines.push(`; ${name}.lthn`);
        for (const record of resource.records) {
          switch (record.type) {
            case 'GLUE4':
              lines.push(`${name}.lthn. 300 IN NS  ${record.ns}`);
              lines.push(`${record.ns.replace(/\.$/, '')}.lthn. 300 IN A   ${record.address}`);
              break;
            case 'GLUE6':
              lines.push(`${name}.lthn. 300 IN NS  ${record.ns}`);
              lines.push(`${record.ns.replace(/\.$/, '')}.lthn. 300 IN AAAA ${record.address}`);
              break;
            case 'TXT':
              for (const txt of record.txt || []) lines.push(`${name}.lthn. 300 IN TXT  "${txt}"`);
              break;
            case 'DS':
              lines.push(`${name}.lthn. 300 IN DS   ${record.keyTag} ${record.algorithm} ${record.digestType} ${record.digest}`);
              break;
            case 'NS':
              lines.push(`${name}.lthn. 300 IN NS  ${record.ns}`);
              break;
          }
        }
      }
    } catch { /* name not registered — skip */ }
  }

  lines.push(``, `; === End (${KNOWN_NAMES.length} names checked) ===`);
  return lines.join('\n') + '\n';
}

async function checkAndUpdate() {
  try {
    const { height, treeRoot } = await getTreeRoot();

    if (treeRoot === lastTreeRoot) {
      return; // No change — cache is valid
    }

    console.log(`[${new Date().toISOString().slice(11, 19)}] Tree root changed at height ${height} — regenerating zone`);

    const zone = await generateZone(height);

    // Atomic write — temp file then rename
    const tmpFile = `${ZONE_FILE}.tmp`;
    fs.writeFileSync(tmpFile, zone);

    // Validate before replacing
    if (!zone.includes('$ORIGIN lthn.')) {
      console.error('Zone validation failed — not replacing');
      fs.unlinkSync(tmpFile);
      return;
    }

    fs.renameSync(tmpFile, ZONE_FILE);
    lastTreeRoot = treeRoot;
    lastZone = zone;

    const recordCount = (zone.match(/\tIN\s/g) || []).length;
    console.log(`  Zone updated: ${recordCount} records, serial based on height ${height}`);

  } catch (err) {
    console.error(`  Error: ${err.message} — keeping cached zone`);
  }
}

console.log('HSD Zone Cache');
console.log(`  HSD: ${HSD_URL}`);
console.log(`  Zone: ${ZONE_FILE}`);
console.log(`  Check: every ${CHECK_INTERVAL / 1000}s`);
console.log(`  Source: HSD sidechain ONLY (read-only output)`);
console.log('');

// Initial generation
checkAndUpdate();

// Polling loop — checks tree root, only regenerates on change
setInterval(checkAndUpdate, CHECK_INTERVAL);