import { CachedZone, DNSRecord, DNSZone, SOARecord } from "../models/interfaces";
import { readZoneFile } from "./reader";
import { DNSRecordType } from "./records";
import { writeZoneFile } from "./writer";

export class DNSCache {
  private cached: Record<string, CachedZone> = {};

  constructor(private ttl = 1600) {}

  has(name: string): boolean {
    return this.cached[name] != null;
  }

  async get(name: string): Promise<CachedZone | null> {
    const cached = this.cached[name];
    if (!cached) {
      return null;
    }

    if (cached.changed.getTime() < new Date().getTime() - this.ttl * 1000) {
      return this.load(name, cached.file);
    }

    return this.cached[name];
  }

  async set(name: string, zone: CachedZone): Promise<void> {
    this.cached[name] = zone;
  }

  async load(name: string, file: string): Promise<CachedZone> {
    const zoneFile = await readZoneFile(file);
    const cache = {
      name,
      file,
      zone: zoneFile,
      added: new Date(),
      changed: new Date()
    }
    this.cached[name] = cache;
    return cache;
  }

  async save(name: string): Promise<void> {
    const zone = await this.get(name);
    if (!zone) {
      throw new Error('No such cached zone file!');
    }
    await writeZoneFile(zone.zone, zone.file);
  }

  async update(name: string, newZone?: CachedZone): Promise<void> {
    let zone: CachedZone | null;
    if (newZone) {
      zone = newZone;
    } else {
      zone = await this.get(name);
    }

    if (!zone) {
      throw new Error('No such cached zone file!');
    }

    zone.changed = new Date();
    const soa = zone.zone.records.find((record) => record.type === DNSRecordType.SOA) as SOARecord;
    soa.serial = Math.floor(Date.now() / 1000);

    this.set(name, zone);
    return this.save(name);
  }
}