Day16.kt

package aoc2021.day16

import aoc2020.day05.binaryToDecimal

fun expandAndSumVersion(hexInput: String): Int {
  val hexToBin = getHexToBinMap()
  val packetsToProcess = mutableListOf<Packet>()
  var binaryInput = ""
  hexInput.forEach { binaryInput += hexToBin[it] }

  var versionChecksum = -1

  packetsToProcess.add(
    Packet(
      binaryInput.substring(6),
      binaryToDecimal(binaryInput.substring(0, 3).toInt()),
      binaryToDecimal(binaryInput.substring(3, 6).toInt())
    )
  )

  while (packetsToProcess.isNotEmpty()) {
    val packet = packetsToProcess[0]

//    when (packet.typeId) {
//      4 -> {
//        val bits = packet.content.windowed(5, 5)
//        var number = ""
//        bits.forEach { number += it.substring(1) }
//        val result = binaryToDecimal(number.toInt())
//      }
//      else -> {
//        val lengthTypeId = packet.content.substring(0, 1).toInt()
//        val length = if (lengthTypeId == 0) 15 else 11
//      }
//    }

    versionChecksum += (packet.version)
    packetsToProcess.removeAt(0)
  }

  return versionChecksum
}


fun processPacket(binaryInput: String): Int {

  val packet = Packet(
    binaryInput.substring(6),
    binaryToDecimal(binaryInput.substring(0, 3).toInt()),
    binaryToDecimal(binaryInput.substring(3, 6).toInt())
  )

  var versionChecksum = 0
  when (packet.typeId) {
    4 -> {
      val bits = packet.content.windowed(5, 5)
      val bitsToKeep = mutableListOf<String>()

      for (idx in 1..bits.size) {
        bitsToKeep.add(bits[idx])
        if (bits[idx].startsWith("0")) {
          break
        }
      }

      var number = ""
      bits.forEach { number += it.substring(1) }
      val result = binaryToDecimal(number.toInt())
      versionChecksum += packet.version
    }
    else -> {
      val lengthTypeId = packet.content.substring(6, 7).toInt()
      if (lengthTypeId == 0) {
        val totalLengthBits = 15
        val totalLength = binaryToDecimal(packet.content.substring(7, 7 + totalLengthBits).toInt())
      } else {
        val subPacketsNumBits = 11
        val subPacketsNum = binaryToDecimal(packet.content.substring(7, 7 + subPacketsNumBits).toInt())
      }
    }
  }

  return versionChecksum
}

fun processLiteralPacket(literalPacket: String): Int {

  return -1
}

fun processOperatorPackets(operatorPackets: String): Int {
  val versionChecksum = 0

  return versionChecksum
}

fun getHexToBinMap(): Map<Char, String> {
  val map = mutableMapOf<Char, String>()
  map['0'] = "0000"
  map['1'] = "0001"
  map['2'] = "0010"
  map['3'] = "0011"
  map['4'] = "0100"
  map['5'] = "0101"
  map['6'] = "0110"
  map['7'] = "0111"
  map['8'] = "1000"
  map['9'] = "1001"
  map['A'] = "1010"
  map['B'] = "1011"
  map['C'] = "1100"
  map['D'] = "1101"
  map['E'] = "1110"
  map['F'] = "1111"
  return map
}

class Packet(val content: String, val version: Int, val typeId: Int) {
  override fun toString(): String {
    return "{version: $version, typeId: $typeId, packet: $content}"
  }
}