// Adapted from https://github.com/mafintosh/dns-packet
import { bytesToString, labelhash, stringToBytes, type ByteArray } from 'viem'
import { encodeLabelhash } from './labels.js'

/*
 * @description Encodes a DNS packet into a ByteArray containing a UDP payload.
 */
export function packetToBytes(packet: string): ByteArray {
  // strip leading and trailing `.`
  const value = packet.replace(/^\.|\.$/gm, '')
  if (value.length === 0) return new Uint8Array(1)

  const bytes = new Uint8Array(stringToBytes(value).byteLength + 2)

  let offset = 0
  const list = value.split('.')
  for (let i = 0; i < list.length; i += 1) {
    let encoded = stringToBytes(list[i])
    // if the length is > 255, make the encoded label value a labelhash
    // this is compatible with the universal resolver
    if (encoded.byteLength > 255)
      encoded = stringToBytes(encodeLabelhash(labelhash(list[i])))
    bytes[offset] = encoded.length
    bytes.set(encoded, offset + 1)
    offset += encoded.length + 1
  }

  if (bytes.byteLength !== offset + 1) return bytes.slice(0, offset + 1)

  return bytes
}

export function bytesToPacket(bytes: ByteArray): string {
  let offset = 0
  let result = ''

  while (offset < bytes.length) {
    const len = bytes[offset]
    if (len === 0) {
      offset += 1
      break
    }

    result += `${bytesToString(bytes.subarray(offset + 1, offset + len + 1))}.`
    offset += len + 1
  }

  return result.replace(/\.$/, '')
}