package be.vandewalleh.aoc.days

import be.vandewalleh.aoc.utils.BaseDay
import be.vandewalleh.aoc.utils.input.Day

@Day
class Day08 : BaseDay() {

    override fun part1() = input.lines.value
        .map { it.split(" | ")[1].split(" ") }
        .sumOf { it.count { it.length in setOf(2, 3, 4, 7) } }

    override fun part2() = input.lines.value
        .map { it.split(" | ").map { it.split(" ") } }
        .sumOf { (pattern, digits) ->
            val patterns = decodePatterns(pattern)
            digits.map { patterns[it.sortChars()] }.joinToString("").toInt()
        }

    private fun decodePatterns(patterns: List<String>): Map<String, Int> {
        val result = Array(10) { "" }

        result[1] = patterns.single { it.length == 2 }
        result[7] = patterns.single { it.length == 3 }
        result[4] = patterns.single { it.length == 4 }
        result[8] = patterns.single { it.length == 7 }

        val frequency = patterns.flatMap { it.toCharArray().toList() }.groupBy { it }.mapValues { it.value.size }
        val a = (result.letters(7) - result.letters(1)).first()
        val b = frequency.findKey { it.value == 6 }
        val c = frequency.findKey { it.value == 8 && it.key != a }
        val d = frequency.findKey { it.value == 7 && it.key in result.letters(4) }
        val e = frequency.findKey { it.value == 4 }
        val f = frequency.findKey { it.value == 9 }

        result[0] = patterns.find { it.length == 6 && d !in it }!!
        result[2] = patterns.find { it.length == 5 && b !in it && f !in it }!!
        result[3] = patterns.find { it.length == 5 && b !in it && e !in it }!!
        result[5] = patterns.find { it.length == 5 && c !in it && e !in it }!!
        result[6] = patterns.find { it.length == 6 && c !in it }!!
        result[9] = patterns.find { it.length == 6 && e !in it }!!

        return result.mapIndexed { index, value -> value.sortChars() to index }.toMap()
    }

    private fun Array<String>.letters(number: Int) = this[number].toCharArray().toSet()
    private fun <K, V> Map<K, V>.findKey(predicate: (Map.Entry<K, V>) -> Boolean) = entries.find(predicate)!!.key
    private fun String.sortChars() = toCharArray().sorted().joinToString("")
}