/**
 * Simple JSON file-based cache for DNS records.
 * No native dependencies — works on any Node version.
 *
 * Structure of dns-cache.json:
 * {
 *   "cloudflare": {
 *     "zone123": {
 *       "synced_at": "2024-01-01T00:00:00.000Z",
 *       "records": [ { id, type, name, content, ttl, priority }, ... ]
 *     }
 *   }
 * }
 */

const fs   = require('fs');
const path = require('path');

const CACHE_PATH = process.env.DB_PATH || path.join(__dirname, '..', 'dns-cache.json');

// ─── Load / save ─────────────────────────────────────────────────────────────

function load() {
  try {
    return JSON.parse(fs.readFileSync(CACHE_PATH, 'utf8'));
  } catch {
    return {};
  }
}

function save(data) {
  fs.writeFileSync(CACHE_PATH, JSON.stringify(data, null, 2), 'utf8');
}

// ─── Public API ──────────────────────────────────────────────────────────────

function getRecords(provider, zoneId) {
  const data = load();
  return data[provider]?.[zoneId]?.records ?? [];
}

function getSyncedAt(provider, zoneId) {
  const data = load();
  return data[provider]?.[zoneId]?.synced_at ?? null;
}

// Returns { [zoneId]: { synced_at, record_count } } for all cached zones of a provider
function getProviderSyncStatus(provider) {
  const data = load();
  const zones = data[provider] ?? {};
  const result = {};
  for (const [zoneId, zone] of Object.entries(zones)) {
    result[zoneId] = {
      synced_at:    zone.synced_at ?? null,
      record_count: (zone.records ?? []).length,
    };
  }
  return result;
}

function getZoneName(provider, zoneId) {
  const data = load();
  return data[provider]?.[zoneId]?.zone_name ?? zoneId;
}

function replaceZoneRecords(provider, zoneId, records, zoneName) {
  const data = load();
  if (!data[provider]) data[provider] = {};
  data[provider][zoneId] = {
    zone_name: zoneName ?? data[provider]?.[zoneId]?.zone_name ?? zoneId,
    synced_at: new Date().toISOString(),
    records: records.map(r => ({
      id:       r.id,
      type:     r.type,
      name:     r.name,
      content:  r.content,
      ttl:      r.ttl ?? null,
      priority: r.priority ?? null,
    })),
  };
  save(data);
}

function upsertRecord(provider, zoneId, record) {
  const data = load();
  if (!data[provider]) data[provider] = {};
  if (!data[provider][zoneId]) data[provider][zoneId] = { synced_at: null, records: [] };

  const records = data[provider][zoneId].records;
  const idx = records.findIndex(r => r.id === record.id);
  const entry = {
    id:       record.id,
    type:     record.type,
    name:     record.name,
    content:  record.content,
    ttl:      record.ttl ?? null,
    priority: record.priority ?? null,
  };

  if (idx >= 0) records[idx] = entry;
  else records.push(entry);

  save(data);
}

function deleteRecord(provider, zoneId, recordId) {
  const data = load();
  const zone = data[provider]?.[zoneId];
  if (!zone) return;
  zone.records = zone.records.filter(r => r.id !== recordId);
  save(data);
}

/**
 * Returns all cached zones across all providers as a flat list.
 * Groups duplicate zone names so you can spot the same domain on multiple providers.
 */
function getAllZones() {
  const data   = load();
  const byName = {};

  for (const [provider, zones] of Object.entries(data)) {
    for (const [zoneId, zone] of Object.entries(zones)) {
      const name = zone.zone_name ?? zoneId;
      if (!byName[name]) byName[name] = [];
      byName[name].push({
        provider,
        zone_id:      zoneId,
        record_count: (zone.records ?? []).length,
        synced_at:    zone.synced_at ?? null,
      });
    }
  }

  return Object.entries(byName)
    .map(([name, entries]) => ({ name, entries, duplicate: entries.length > 1 }))
    .sort((a, b) => a.name.localeCompare(b.name));
}

function getStats() {
  const data = load();
  const typeCounts = {};
  let totalZones = 0;
  let zonesWithMx = 0;
  const perProvider = {};

  for (const [provider, zones] of Object.entries(data)) {
    const zoneCount = Object.keys(zones).length;
    totalZones += zoneCount;
    perProvider[provider] = { zones: zoneCount };

    for (const zone of Object.values(zones)) {
      const records = zone.records ?? [];
      const hasMx = records.some(r => r.type === 'MX');
      if (hasMx) zonesWithMx++;

      for (const r of records) {
        typeCounts[r.type] = (typeCounts[r.type] || 0) + 1;
      }
    }
  }

  const recordTypes = Object.entries(typeCounts)
    .map(([type, count]) => ({ type, count }))
    .sort((a, b) => b.count - a.count);

  return { totalZones, zonesWithMx, recordTypes, perProvider };
}

module.exports = { getRecords, getSyncedAt, getZoneName, getProviderSyncStatus, getAllZones, replaceZoneRecords, upsertRecord, deleteRecord, getStats };