import * as fs from 'fs/promises';
import { DNSRecordType } from 'src/types/dns.enum';
import { SOARecord, DNSRecord, DNSZone } from 'src/types/dns.interfaces';

const maxStrLength = 255;
const magicPadding = 3;

/**
 * Splits and comments SOA record
 * @param record
 * @param padI
 * @param padJ
 * @returns new lines
 */
function createSOAString(
  record: SOARecord,
  padI: number,
  padJ: number,
): string[] {
  const name = record.name.padEnd(padI, ' ');
  const type = record.type.toString().padEnd(padJ, ' ');
  const padK = ' '.padStart(padI + magicPadding);
  const padL =
    ['serial', 'refresh', 'retry', 'expire', 'minimum'].reduce(
      (previous, current) => {
        const len = `${record[current]}`.length;
        return previous > len ? previous : len;
      },
      0,
    ) + 1;
  return [
    `${name} IN ${type} ${record.nameserver} ${record.email} (`,
    `${padK} ${record.serial.toString().padEnd(padL, ' ')} ; Serial`,
    `${padK} ${record.refresh.toString().padEnd(padL, ' ')} ; Refresh`,
    `${padK} ${record.retry.toString().padEnd(padL, ' ')} ; Retry`,
    `${padK} ${record.expire.toString().padEnd(padL, ' ')} ; Expire`,
    `${padK} ${record.minimum.toString().padEnd(padL, ' ')} ; Minimum`,
    `)`,
  ];
}

/**
 * Splits very long TXT records into multiple lines.
 * Mandatory for DKIM keys, for example.
 * @param record
 * @param padI
 * @param padJ
 * @returns new lines
 */
function splitTXTString(
  record: DNSRecord,
  padI: number,
  padJ: number,
): string[] {
  const name = record.name.padEnd(padI, ' ');
  const type = record.type.toString().padEnd(padJ, ' ');
  const strLen = maxStrLength - padI - magicPadding;
  const padK = ' '.padStart(padI + magicPadding);
  const splitStrings = [];

  if (record.value.length < strLen) {
    return [`${name} IN ${type} ${record.value}`];
  }

  let temporary = record.value.replace(/"/g, '');
  while (temporary.length > strLen) {
    splitStrings.push(temporary.substr(0, strLen));
    temporary = temporary.substr(strLen);
  }

  splitStrings.push(temporary);

  return [
    `${name} IN ${type} (`,
    ...splitStrings.map((str) => `${padK} "${str}"`),
    `)`,
  ];
}

export function createZoneFile(zone: DNSZone): string[] {
  const file: string[] = [];
  file.push(`$TTL ${zone.ttl}`);
  file.push(`; GENERATED BY ICYDNS`);

  let longestName = 0;
  let longestType = 0;

  // First pass: for nice alignments
  zone.records.forEach((record) => {
    if (record.name.length > longestName) {
      longestName = record.name.length;
    }

    if (record.type.toString().length > longestType) {
      longestType = record.type.toString().length;
    }
  });

  zone.records.forEach((record) => {
    if (record.type === DNSRecordType.SOA) {
      file.push(
        ...createSOAString(record as SOARecord, longestName, longestType),
      );
      return;
    }

    if (record.type === DNSRecordType.TXT) {
      file.push(...splitTXTString(record, longestName, longestType));
      return;
    }

    const name = record.name.padEnd(longestName, ' ');
    const type = record.type.toString().padEnd(longestType, ' ');
    file.push(`${name} IN ${type} ${record.value}`);
  });

  zone.includes.forEach((include) => {
    file.push(`$INCLUDE ${include}`);
  });

  file.push('');

  return file;
}

export async function writeZoneFile(
  zone: DNSZone,
  file: string,
): Promise<string[]> {
  const fullText = createZoneFile(zone);
  await fs.writeFile(file, fullText.join('\n'));
  return fullText;
}