module Day6

import Prelude
import Node
import Aoc

data Oper = Plus | Times

getOp : Char → Maybe Oper
getOp '+' = Just Plus
getOp '*' = Just Times
getOp _ = Nothing

head' : ∀ a. List a → Maybe a
head' (x :: xs) = Just x
head' _ = Nothing

transpose : ∀ a. List (List a) → List (List a)
transpose {a} Nil = Nil
transpose {a} (Nil :: xs) = Nil
transpose {a} xs = mapMaybe head' xs :: transpose (map tail xs)

calc : List (List Int) → List Oper → Int
calc rows ops = foldl _+_ 0 $ map go $ zip ops $ rows
    where
      go : Oper × List Int → Int
      go (Plus, nums) = foldl _+_ 0 nums
      go (Times, nums) = foldl _*_ 1 nums

part1 : String → Int
part1 text =
  let lines = split (trim text) "\n" in
  case reverse lines of
    Nil => -1
    last :: rest =>
      let key = unpack last
       in calc (transpose (map (splitLine 0 key ∘ unpack) rest)) $ mapMaybe getOp key
  where
    splitLine : Int → List Char → List Char → List Int
    splitLine acc (a :: b :: cs) (d :: ds) =
      if b == ' '
        then let acc = if d == ' ' then acc else acc * 10 + (ord d - 48)
              in splitLine acc (b :: cs) ds
        else acc :: splitLine 0 (b :: cs) ds
    splitLine acc _ (d :: ds) =
      let acc = if d == ' ' then acc else acc * 10 + (ord d - 48)
       in splitLine acc Nil ds
    splitLine acc _ Nil = acc :: Nil

part2 : String → Int
part2 text =
  let lines = split (trim text) "\n" in
  case reverse lines of
      Nil => -1
      last :: rest =>
        let key = unpack last
        in calc (splitOn 0 $ map (packNum 0) $ transpose $ map unpack $ reverse rest) $ mapMaybe getOp key
  where
    packNum : Int → List Char → Int
    packNum acc Nil = acc
    packNum acc (' ' :: cs) = packNum acc cs
    packNum acc (c :: cs) = packNum (acc * 10 + (ord c - 48)) cs

run : String -> IO Unit
run fn = do
  putStrLn fn
  text <- readFile fn
  putStrLn $ "part1 \{show $ part1 text}"
  putStrLn $ "part2 \{show $ part2 text}"

main : IO Unit
main = do
  run "aoc2025/day6/eg.txt"
  run "aoc2025/day6/input.txt"