module Task1 (task1) where

import Common (Position, readWorld, multiMapFromList, pairPermutations)
import qualified Data.Map.Strict as Map
import qualified Data.Set as Set
import Control.Monad (join)
import Flow

task1 :: String -> Int
task1 input = case readWorld input of
  ((width, height), antennas) -> multiMapFromList antennas |> Map.elems |> map antinodesOfFrequency |> join |> filter isInWorld |> Set.fromList |> length
    where
      antinodesOfFrequency :: [Position] -> [Position]
      antinodesOfFrequency nodes = pairPermutations nodes >>= antinodesOfPair

      antinodesOfPair :: (Position, Position) -> [Position]
      antinodesOfPair ((ax, ay), (bx, by)) =
        let diffX = bx - ax
            diffY = by - ay
        in [(ax - diffX, ay - diffY), (bx + diffX, by + diffY)]

      isInWorld :: Position -> Bool
      isInWorld (x, y)
        | x < 0 = False
        | x >= width = False
        | y < 0 = False
        | y >= height = False
        | otherwise = True