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

function cleanString(str: string): string {
  return str
    .replace(/;[^"]+$/, '') // Remove comments from the end
    .replace(/\s+/g, ' ') // Remove duplicate whitespace
    .trim(); // Remove whitespace from start and end
}

function parseRecordLine(
  line: string,
  index: number,
  lines: string[],
): DNSRecord | SOARecord | null {
  let actualLine = '';
  const clean = cleanString(line);
  if (clean.includes('(')) {
    actualLine += clean;
    const trimLines = lines.slice(index + 1);
    for (const trimLine of trimLines) {
      actualLine += ' ' + cleanString(trimLine);
      if (trimLine.includes(')')) {
        break;
      }
    }
    actualLine = cleanString(actualLine.replace(/\(|\)/g, ''));
  } else {
    actualLine = clean;
  }

  const split = actualLine.replace(/"\s"/g, '').split(' ');
  if (split[0] === 'IN' && split[1] === 'NS') {
    return {
      name: '',
      type: DNSRecordType.NS,
      value: split.slice(2).join(' '),
    };
  }

  if (split[2] === 'SOA') {
    return {
      name: split[0],
      type: DNSRecordType.SOA,
      value: split.slice(3).join(' '),
      nameserver: split[3],
      email: split[4],
      serial: parseInt(split[5], 10),
      refresh: parseInt(split[6], 10),
      retry: parseInt(split[7], 10),
      expire: parseInt(split[8], 10),
      minimum: parseInt(split[9], 10),
    };
  }

  if (!actualLine.includes('IN')) {
    return null;
  }

  return {
    name: split[0],
    type: DNSRecordType[<keyof typeof DNSRecordType>split[2]],
    value: split.slice(3).join(' '),
  };
}

export function parseZoneFile(lines: string[]): DNSZone {
  let ttl = 0;
  const includes = [];
  const records: DNSRecord[] = [];

  for (const index in lines) {
    const line = lines[index];
    if (line.startsWith('$TTL')) {
      ttl = parseInt(line.split(' ')[1], 10);
      continue;
    }

    if (line.startsWith('$INCLUDE')) {
      includes.push(...line.split(' ').slice(1));
      continue;
    }

    const record = parseRecordLine(line, parseInt(index, 10), lines);
    if (record) {
      records.push(record);
    }
  }

  return {
    ttl,
    includes,
    records,
  };
}

export async function readZoneFile(file: string): Promise<DNSZone> {
  const lines = await fs.readFile(file, { encoding: 'utf-8' });
  const splitLines = lines.split('\n');
  return parseZoneFile(splitLines);
}