day5.hs

{-# LANGUAGE QuasiQuotes #-}

module Day5 where

import Control.Monad (void)
import Data.List (transpose)
import Data.Maybe (catMaybes)
import Text.Parsec
import Text.Parsec.String
import Text.RawString.QQ

import Util (regularParse, replaceAtIndex)

testInput1 :: String
testInput1 = [r|
    [D]    
[N] [C]    
[Z] [M] [P]
 1   2   3 

move 1 from 2 to 1
move 3 from 1 to 3
move 2 from 2 to 1
move 1 from 1 to 2
|]

type Item = Maybe Char

data MoveSpec = MoveSpec {
  num :: Int,
  from :: Int,
  to :: Int
} deriving Show

emptyItemParser :: Parser Item
emptyItemParser = Nothing <$ try (string "   ")

filledItemParser :: Parser Item
filledItemParser = do
  void $ char '['
  c <- anyChar
  void $ char ']'
  return $ Just c

itemParser :: Parser Item
itemParser = emptyItemParser <|> filledItemParser

itemsParser :: Parser [Item]
itemsParser = sepBy1 itemParser $ char ' '

stackIndexParser :: Parser [Char]
stackIndexParser = sepBy1 (char ' ' *> digit <* char ' ') (char ' ') <* endOfLine

moveSpecParser :: Parser MoveSpec
moveSpecParser = do
  void $ string "move "
  num <- digit
  void $ string " from "
  from <- digit
  void $ string " to "
  to <- digit
  return MoveSpec { num = read [num], from = read [from], to = read [to] }

inputParser :: Parser ([[Item]], [Char], [MoveSpec])
inputParser = do
  void endOfLine
  items <- endBy1 itemsParser endOfLine
  idxs <- stackIndexParser
  void $ endOfLine
  specs <- endBy1 moveSpecParser endOfLine
  return (items, idxs, specs)