Advent-of-Code/2020/src/main/kotlin/Day16.kt

package be.vandewalleh.aoc.days

import be.vandewalleh.aoc.utils.input.Day
import be.vandewalleh.aoc.utils.input.Groups
import org.eclipse.collections.api.multimap.list.ListMultimap
import org.eclipse.collections.api.multimap.list.MutableListMultimap
import org.eclipse.collections.api.multimap.set.MutableSetMultimap
import org.eclipse.collections.impl.factory.Multimaps
import org.eclipse.collections.impl.multimap.list.FastListMultimap

@Day(16)
class Day16(@Groups val input: List<List<String>>) {

    private val rangesGroup = input[0]
    private val myTicket = input[1][1]
    private val nearbyTicketsGroup = input[2].drop(1)

    private val rangeRe = "(\\d+)-(\\d+)".toRegex()

    private fun extractRanges(line: String): Sequence<IntRange> = rangeRe.findAll(line)
        .map {
            val (min, max) = it.destructured
            min.toInt()..max.toInt()
        }

    fun part1(): Int {
        val minMax = mutableListOf<IntRange>()

        for (line in rangesGroup) {
            minMax.addAll(extractRanges(line))
        }

        val nearbyTickets = mutableListOf<Int>()
        for (line in nearbyTicketsGroup) {
            line.splitToSequence(",").forEach { nearbyTickets.add(it.toInt()) }
        }

        val invalid = mutableListOf<Int>()
        nearbyTickets.forEach { number ->
            if (minMax.none { number in it }) invalid.add(number)
        }

        return invalid.sum()
    }

    private fun isTicketValid(ticket: List<Int>, ranges: Iterable<IntRange>): Boolean {
        for (number in ticket) {
            if (!ranges.any { number in it }) return false
        }
        return true
    }

    private fun inRanges(value: Int, ranges: List<IntRange>) = ranges.any { value in it }

    fun part2(): Long {
        val rangesByName = namedRanges()
        val validTickets = validTickets(rangesByName)
        val indexesByCategory = indexesByCategory(rangesByName, validTickets)

        removeDuplicates(indexesByCategory)

        val myTicketValues = myTicket.split(",").map { it.toInt() }

        var mult = 1L
        indexesByCategory.forEachKeyValue { category, index ->
            if (category.startsWith("departure")) {
                mult *= myTicketValues[index]
            }
        }
        return mult
    }

    private fun removeDuplicates(indexesByCategory: MutableSetMultimap<String, Int>) {
        val toBeRemoved = HashSet<Int>()
        val queue = ArrayDeque<Int>()

        indexesByCategory.multiValuesView()
            .toSortedListBy { it.size() }
            .forEach { it.forEach { if (toBeRemoved.add(it)) queue.add(it) } }

        queue.removeLast()

        val categoriesToRemove = mutableListOf<String>()

        while (queue.isNotEmpty()) {
            val duplicate = queue.removeFirst()

            categoriesToRemove.clear()

            for (entry in indexesByCategory.keyMultiValuePairsView()) {
                if (entry.two.size() < 2) continue
                categoriesToRemove.add(entry.one)
            }

            for (category in categoriesToRemove) {
                indexesByCategory.remove(category, duplicate)
            }
        }
    }

    private fun indexesByCategory(
        rangesByName: ListMultimap<String, IntRange>,
        validTickets: List<List<Int>>,
    ): MutableSetMultimap<String, Int> {
        val indexesByCategory = Multimaps.mutable.set.empty<String, Int>()

        for (entry in rangesByName.keyMultiValuePairsView()) {
            val category = entry.one
            val ranges = entry.two.toList()

            for (i in validTickets.first().indices) {
                var allInRange = true
                for(ticket in validTickets){
                    val current = ticket[i]
                    if(!inRanges(current, ranges)){
                        allInRange = false
                        break
                    }
                }
                if (allInRange) indexesByCategory.put(category, i)
            }
        }
        return indexesByCategory
    }

    private fun validTickets(rangesByName: MutableListMultimap<String, IntRange>): List<List<Int>> {
        val validTickets = mutableListOf<List<Int>>()
        val ranges = rangesByName.valuesView().toList()
        for (line in nearbyTicketsGroup) {
            val ticket = line.split(",").map { it.toInt() }
            if (isTicketValid(ticket, ranges)) {
                validTickets.add(ticket)
            }
        }
        return validTickets
    }

    private fun namedRanges(): MutableListMultimap<String, IntRange> {
        val rangesByName = FastListMultimap<String, IntRange>()
        for (line in rangesGroup) {
            val name = line.substringBefore(":")
            extractRanges(line).forEach {
                rangesByName.put(name, it)
            }
        }
        return rangesByName
    }
}