package aoc.day18

import aoc._
import aoc.direction._
import Dir._
import scala.collection.SortedMap
import scala.collection.mutable

case class Dig(dir: Dir, count: Int, color: String):
  lazy val part2 = Parser.parse(Parser.digHex, color).get

  def apply(x: Long, y: Long) = dir.long(x, y, count)

object Parser extends CommonParser with DirParser:
  val dig = dir ~ num ~ "(#" ~ """[0-9a-f]{6}""".r ~ ")" ^^ { case dir ~ num ~ _ ~ color ~ _ =>
    Dig(dir, num, color)
  }

  val hexDigit = """[0-9a-f]""".r ^^ {
    case c if c.charAt(0).isDigit => c.charAt(0) - '0'
    case c                        => c.charAt(0) - 'a' + 10
  }

  def hexNum(len: Int) = repN(len, hexDigit).map(_.foldLeft(0)(_ * 16 + _))

  val toDir = Array(Right, Down, Left, Up)
  val digHex = hexNum(5) ~ hexDigit ^^ { case num ~ dig => Dig(toDir(dig), num, "") }

  def apply(s: String) = parse(dig, s).get

def instructions() = lines.map(Parser(_)).toSeq

def points(ins: Seq[Dig]) =
  ins
    .scanLeft((0L, 0L)) { case ((x, y), in) => in(x, y) }
    .dropRight(1)

extension [T](ss: Seq[T]) def shiftLeft = ss.drop(1) ++ ss.take(1)

def area(pts: Seq[(Long, Long)]) = pts
  .lazyZip(pts.shiftLeft)
  .map { case ((ax, ay), (bx, by)) =>
    (bx - ax) * (by + ay)
  }
  .sum
  .abs

def circum(pts: Seq[(Long, Long)]) = pts
  .lazyZip(pts.shiftLeft)
  .map { case ((ax, ay), (bx, by)) =>
    (bx - ax).abs + (by - ay).abs
  }
  .sum

def areaBlock(pts: Seq[(Long, Long)]) = (area(pts) + circum(pts)) / 2 + 1

def part1 =
  val ins = instructions()
  val pts = points(ins)
  println(areaBlock(pts))

def part2 =
  val ins = instructions().map(_.part2)
  val pts = points(ins)
  println(areaBlock(pts))

@main def Day18(part: Int) = part match
  case 1 => part1
  case 2 => part2