module Part2 where

import Commons
import Data.Array (bounds, assocs)
import Data.List (sortBy, elemIndices)


tiltNorth :: Platform -> Platform
tiltNorth platform = tilt (-1, 0) (map fst $ filter (\ (_, r) -> r == Round) $ assocs platform) platform

tiltWest :: Platform -> Platform
tiltWest platform = tilt (0, -1) (sortBy (\ (y1, x1) (y2, x2) -> if x1 < x2 then LT else GT) $ map fst
                    $ filter (\ (_, r) -> r == Round) $ assocs platform) platform

tiltSouth :: Platform -> Platform
tiltSouth platform = tilt (1, 0) (reverse $ map fst $ filter (\ (_, r) -> r == Round) $ assocs platform) platform

tiltEast :: Platform -> Platform
tiltEast platform = tilt (0, 1) (sortBy (\ (y1, x1) (y2, x2) -> if x1 > x2 then LT else GT) $ map fst
                    $ filter (\ (_, r) -> r == Round) $ assocs platform) platform

applyCycles :: [Platform] -> Platform -> [Platform]
applyCycles history platform
  | history /= [] && platform `elem` tail history = history
  | otherwise = let newPlatform = tiltEast $ tiltSouth $ tiltWest $ tiltNorth platform
                in applyCycles (newPlatform: history) newPlatform



getExpectedIndex :: [Platform] -> Int
getExpectedIndex history = let endIndex = length history
                               startIndex = endIndex - last (elemIndices (head history) history)
                           in endIndex - (((1000000000 - startIndex) `mod` (endIndex - startIndex)) + startIndex)

getLoads :: Platform -> [Int]
getLoads platform =
  let (yMax, _) = snd $ bounds platform
      cyclesHistory = applyCycles [] platform
  in map (\ ((y, _), r) -> if r == Round then yMax + 1 - y else 0)
     $ assocs (cyclesHistory !! getExpectedIndex cyclesHistory)