package day04

import java.io.File

/**
 * author:  vishnu
 * date:    5/20/17
 * purpose:
 */

fun main(args: Array<String>) {
    val rooms = getRooms()
    println("Part 1: total = ${rooms.map { it.id }.sum()}")
    println("Part 2: room  = ${findNorthPoleRoom(rooms)}")
}

private fun getRooms() =
        File("src/day04/rooms.txt").readLines()
                .map {
                    val name = it.substring(0, it.length - 10)
                    val id = it.substring(it.length - 10, it.length - 7).toInt()
                    val checksum = it.substring(it.length - 6, it.length - 1)
                    Room(name, id, checksum)
                }
                .filter { it.isReal() }

private fun findNorthPoleRoom(rooms: List<Room>) =
        rooms[rooms.indexOfFirst { decryptRoomName(it.name, it.id).contains("northpole") }].id

private fun decryptRoomName(name: String, id: Int): String {
    val increase = id % 26
    return name.toCharArray()
            .map {
                when {
                    it == '-' -> ' '
                    it.toInt() + increase > 122 -> it.plus(increase - 26)
                    else -> it.plus(increase)
                }
            }
            .joinToString("")
}

internal class Room(val name: String, val id: Int, val checksum: String) {
    fun isReal(): Boolean {
        val chars: MutableMap<Char, Int> = HashMap(Math.min(name.length, 26))
        name.toCharArray()
                .filterNot { it == '-' }
                .forEach {
                    when {
                        chars.containsKey(it) -> chars.put(it, chars.getValue(it) + 1)
                        else -> chars.put(it, 1)
                    }
                }
        val sortedMap = chars.toSortedMap(ValueComparator(chars))
        val generated = sortedMap.keys.take(5).joinToString("")
        return generated == checksum
    }
}

internal class ValueComparator(val base: Map<Char, Int>) : Comparator<Char> {
    override fun compare(a: Char, b: Char) = if (base.getValue(a) > base.getValue(b)) -1 else 1
}