package be.vandewalleh.aoc.days

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

@Day
class Day05 : BaseDay() {

    data class Point(val x: Int, val y: Int)

    private val re = "(\\d+),(\\d+) -> (\\d+),(\\d+)".toRegex()

    private fun path(start: Point, end: Point): Sequence<Point> {
        val dx = end.x.compareTo(start.x)
        val dy = end.y.compareTo(start.y)
        return generateSequence(start) {
            if (it == end) null
            else Point(it.x + dx, it.y + dy)
        }
    }

    override fun part1(): Int {
        val visited = HashMap<Point, Int>()
        input.lines.value
            .map {
                re.find(it)!!.destructured.let { (x1, y1, x2, y2) ->
                    Point(x1.toInt(), y1.toInt()) to Point(x2.toInt(), y2.toInt())
                }
            }
            .filter { (start, end) -> start.x == end.x || start.y == end.y }
            .flatMap { (start, end) -> path(start, end) }
            .forEach { visited.compute(it) { _, value -> (value ?: 0) + 1 } }

        return visited.values.count { it >= 2 }
    }

    override fun part2(): Int {
        val visited = HashMap<Point, Int>()
        input.lines.value
            .map {
                re.find(it)!!.destructured.let { (x1, y1, x2, y2) ->
                    Point(x1.toInt(), y1.toInt()) to Point(x2.toInt(), y2.toInt())
                }
            }
            .flatMap { (start, end) -> path(start, end) }
            .forEach { visited.compute(it) { _, value -> (value ?: 0) + 1 } }

        return visited.values.count { it >= 2 }
    }
}