-- requires cabal install --lib megaparsec parser-combinators heap vector
module Main (main) where

import           Control.Applicative.Permutations
import           Control.Monad                    (void, when)
import qualified Data.Char                        as C
import           Data.Either
import           Data.Functor
import qualified Data.Heap                        as H
import qualified Data.List                        as L
import qualified Data.Map                         as M
import           Data.Maybe
import qualified Data.Set                         as S
import qualified Data.Vector                      as V
import qualified Data.Vector.Unboxed              as VU
import           Data.Void                        (Void)
import           Text.Megaparsec
import           Text.Megaparsec.Char

import           Debug.Trace

data Pulse = Low | High deriving (Eq, Show)
data Module = Normal | FlipFlop Bool | Conjunction (M.Map String Pulse) | Broadcaster deriving (Eq, Show)
data Configuration = Configuration Module String [String] deriving (Eq, Show)
type Conf = (Module, [String])
type Input = M.Map String Conf

type Parser = Parsec Void String

parseModule :: Parser Module
parseModule = char '%' $> FlipFlop False
          <|> char '&' $> Conjunction M.empty
          <|> lookAhead (string "broadcaster") $> Broadcaster
          <|> lookAhead letterChar $> Normal

parseLabel :: Parser String
parseLabel = some letterChar

parseConfiguration :: Parser Configuration
parseConfiguration = Configuration <$> parseModule
                                   <*> parseLabel <* string " -> "
                                   <*> some (parseLabel <* optional (string ", "))

parseInput' :: Parser Input
parseInput' = M.fromList . map (\(Configuration m s l) -> (s, (m, l))) <$> some (parseConfiguration <* eol) <* eof

parseInput :: String -> IO Input
parseInput filename = do
  input <- readFile filename
  case runParser parseInput' filename input of
    Left bundle  -> error $ errorBundlePretty bundle
    Right input' -> return input'

compute :: Input -> Int
compute input = L.foldl' lcm 1 $ computeX 0 (take (length targets) $ repeat Nothing) $ initConjuctions input
  where
    computeX :: Int -> [Maybe Int] -> Input -> [Int]
    computeX i acc input | all isJust acc = fromJust <$> acc
                         | otherwise = let (acc', input') = compute' [("button", Low, "broadcaster")] i acc input
                                       in computeX (i+1) acc' input'
    compute' :: [(String, Pulse, String)] -> Int -> [Maybe Int] -> Input -> ([Maybe Int], Input)
    compute' signals i acc input | length stepAll == 0 = (acc, input)
                                 | otherwise = let acc' = map (accStep i stepAll) $ L.zip targets acc
                                               in compute' stepAll i acc' alterAll
      where
        alterAll :: Input
        alterAll = L.foldl' alterOne input signals
        alterOne :: Input -> (String, Pulse, String) -> Input
        alterOne acc (prev, p, me) = alter p prev me acc (M.lookup me input)
        alter :: Pulse -> String -> String -> Input -> Maybe Conf -> Input
        alter _    _    _  input (Just (Normal, _))         = input
        alter High _    _  input (Just (FlipFlop _, _))     = input
        alter Low  _    me input (Just (FlipFlop False, l)) = M.insert me (FlipFlop True, l) input
        alter Low  _    me input (Just (FlipFlop True, l))  = M.insert me (FlipFlop False, l) input
        alter p    prev me input (Just (Conjunction m, l))  = M.insert me (Conjunction $ M.insert prev p m, l) input
        alter p    _    _  input (Just (Broadcaster, l))    = input
        alter _    _    _  input Nothing                    = input
        stepAll :: [(String, Pulse, String)]
        stepAll = L.foldl' stepOne [] signals
        stepOne :: [(String, Pulse, String)] -> (String, Pulse, String) -> [(String, Pulse, String)]
        stepOne acc (prev, p, s) = step p prev s acc (M.lookup s input)
        step :: Pulse -> String -> String -> [(String, Pulse, String)] -> Maybe Conf -> [(String, Pulse, String)]
        step _    _    _  acc (Just (Normal, _))         = acc
        step High _    _  acc (Just (FlipFlop _, _))     = acc
        step Low  _    me acc (Just (FlipFlop False, l)) = acc ++ map (set me High) l
        step Low  _    me acc (Just (FlipFlop True, l))  = acc ++ map (set me Low) l
        step p    prev me acc (Just (Conjunction m, l))  = let p2 = if length (M.filter (\x -> x == High) $ M.insert prev p m) == length m then Low else High
                                                           in acc ++ map (set me p2) l
        step p    _    me acc (Just (Broadcaster, l))    = acc ++ map (set me p) l
        step _    _    _  acc Nothing                    = acc
    initConjuctions :: Input -> Input
    initConjuctions input = let r = M.foldrWithKey initConf input input in r
    initConf :: String -> Conf -> Input -> Input
    initConf c (_, l) input = L.foldl' initOne input l
      where
        initOne :: Input -> String -> Input
        initOne input s = case M.lookup s input of
          Just (Conjunction m, l) -> M.insert s (Conjunction (M.insert c Low m), l) input
          _ -> input
    set :: String -> Pulse -> String -> (String, Pulse, String)
    set me p s = (me, p, s)
    targets = pointsTo toRx
    [toRx] = pointsTo "rx"
    pointsTo :: String -> [String]
    pointsTo name = L.foldl' (\acc (k, (_, l)) -> if isJust (L.elemIndex name l) then k:acc else acc) [] $ M.assocs input
    accStep :: Int -> [(String, Pulse, String)] -> (String, Maybe Int) -> Maybe Int
    accStep _ _ (_, Just x) = Just x
    accStep i stepAll (t, Nothing) | triggered = Just (i + 1)
                                   | otherwise = Nothing
      where
        triggered = L.foldl' (trigg t) False stepAll
        trigg _ True _            = True
        trigg t False (_, Low, u) = t == u
        trigg _ _ _               = False

main :: IO ()
main = do
  input <- parseInput "input"
  print $ compute input