import Control.Applicative
import Data.Set (fromList)
import Data.Bifunctor (bimap)

type Freq = Char
type Coords = (Int, Int)
data Antenna = Antenna { frequency :: Freq
                       , coordinates :: Coords
                       } deriving (Show, Eq)

readAntenna :: Freq -> Coords -> Antenna
readAntenna frequency coordinates = Antenna {frequency=frequency, coordinates=coordinates}

getAntennas :: [String] -> [Antenna]
getAntennas grid = concat . getZipList $ getAntennasRow <$> ZipList [0..] <*> ZipList grid
                     where getAntennasRow n row = [ readAntenna x (n, y) | (x, y) <- zip row [0..], x /= '.' ]

isInside :: Coords -> Int -> Int -> Bool
isInside c x y = fst c >= 0 && fst c < x && snd c >= 0 && snd c < y

generateCoords :: Coords -> Coords -> [Coords]
generateCoords c offset = scanl shiftCoords c (repeat offset)
                              where shiftCoords c = bimap (fst c +) (snd c +)

getAntinodes :: Antenna -> Antenna -> Int -> Int -> [Coords]
getAntinodes a b maxX maxY = let xa = fst $ coordinates a
                                 ya = snd $ coordinates a
                                 xb = fst $ coordinates b
                                 yb = snd $ coordinates b
                                 distX = abs $ xa - xb
                                 distY = abs $ ya - yb
                             in  if frequency a /= frequency b || coordinates a == coordinates b
                                     then []
                                 else if xa > xb && ya > yb
                                     then filter (\c -> isInside c maxX maxY) [(xa + distX, ya + distY), (xb - distX, yb - distY)]
                                          ++ takeWhile (\c -> isInside c maxX maxY) (generateCoords (coordinates a) (distX, distY))
                                          ++ takeWhile (\c -> isInside c maxX maxY) (generateCoords (coordinates b) (-distX, -distY))
                                          ++ [coordinates a, coordinates b]
                                 else if xa > xb && ya < yb
                                     then filter (\c -> isInside c maxX maxY) [(xa + distX, ya - distY), (xb - distX, yb + distY)]
                                          ++ takeWhile (\c -> isInside c maxX maxY) (generateCoords (coordinates a) (distX, -distY))
                                          ++ takeWhile (\c -> isInside c maxX maxY) (generateCoords (coordinates b) (-distX, distY))
                                          ++ [coordinates a, coordinates b]
                                 else if xa == xb && ya > yb
                                     then filter (\c -> isInside c maxX maxY) [(xa, ya + distY), (xb, yb - distY)]
                                          ++ takeWhile (\c -> isInside c maxX maxY) (generateCoords (coordinates a) (0, distY))
                                          ++ takeWhile (\c -> isInside c maxX maxY) (generateCoords (coordinates b) (0, -distY))
                                          ++ [coordinates a, coordinates b]
                                 else if xa == xb && ya < yb
                                     then filter (\c -> isInside c maxX maxY) [(xa, ya - distY), (xb, yb + distY)]
                                          ++ takeWhile (\c -> isInside c maxX maxY) (generateCoords (coordinates a) (0, -distY))
                                          ++ takeWhile (\c -> isInside c maxX maxY) (generateCoords (coordinates b) (0, distY))
                                          ++ [coordinates a, coordinates b]
                                 else if ya == yb && xa > xb
                                     then filter (\c -> isInside c maxX maxY) [(xa + distX, ya), (xb - distX, yb)]
                                          ++ takeWhile (\c -> isInside c maxX maxY) (generateCoords (coordinates a) (distX, 0))
                                          ++ takeWhile (\c -> isInside c maxX maxY) (generateCoords (coordinates b) (-distX, 0))
                                          ++ [coordinates a, coordinates b]
                                 else if ya == yb && xa < xb
                                     then filter (\c -> isInside c maxX maxY) [(xa - distX, ya), (xb + distX, yb)]
                                          ++ takeWhile (\c -> isInside c maxX maxY) (generateCoords (coordinates a) (-distX, 0))
                                          ++ takeWhile (\c -> isInside c maxX maxY) (generateCoords (coordinates b) (distX, 0))
                                          ++ [coordinates a, coordinates b]
                                 else if xa < xb && ya > yb
                                     then filter (\c -> isInside c maxX maxY) [(xa - distX, ya + distY), (xb + distX, yb - distY)]
                                          ++ takeWhile (\c -> isInside c maxX maxY) (generateCoords (coordinates a) (-distX, distY))
                                          ++ takeWhile (\c -> isInside c maxX maxY) (generateCoords (coordinates b) (distX, -distY))
                                          ++ [coordinates a, coordinates b]
                                 else filter (\c -> isInside c maxX maxY) [(xa - distX, ya - distY), (xb + distX, yb + distY)]
                                          ++ takeWhile (\c -> isInside c maxX maxY) (generateCoords (coordinates a) (-distX, -distY))
                                          ++ takeWhile (\c -> isInside c maxX maxY) (generateCoords (coordinates b) (distX, distY))
                                          ++ [coordinates a, coordinates b]


main = do
    contents <- lines <$> readFile "day8.txt"
    let antennas = getAntennas contents
        x = length contents
        y = length $ head contents
        antinodes = fromList $ concat [ getAntinodes a b x y | a <- antennas, b <- antennas, a /= b, frequency a == frequency b ] 
    print $ length antinodes