{-# LANGUAGE GADTs #-}
{-# LANGUAGE LambdaCase #-}
{-# LANGUAGE RankNTypes #-}
{-# LANGUAGE TupleSections #-}

module Lib where

import Data.Char (chr, ord)
import qualified Data.List as L
import qualified Data.Map as M
import Data.Maybe (fromJust)
import qualified Data.Set as S
import Debug.Trace ()
import Parser
import qualified Text.Parsec as Parsec

mget :: (Ord a) => a -> M.Map a b -> b
mget a m = fromJust $ M.lookup a m

automatizem :: M.Map Addend Int -> Matrix -> DFA [Int] Int
automatizem dir (MEq as bs) = eq (fromIntegral $ length dir) (map (`mget` dir) as) (map (`mget` dir) bs)
automatizem dir (MLe a b) = le (mget a dir) (mget b dir)
automatizem dir (MLt a b) = lt (mget a dir) (mget b dir)
automatizem dir (MAnd x y) = conj (automatizem dir x) (automatizem dir y)
automatizem dir (MOr x y) = disj (automatizem dir x) (automatizem dir y)
automatizem dir (MNot x) = compl (automatizem dir x)

automatize :: M.Map Addend Int -> QNMFormula -> NFA [Int] Int
automatize dir (QNMFormula [] m) = minimize (fromIntegral $ length dir) $ nondeterminize $ automatizem dir m
automatize dir (QNMFormula (Neg : quas) m) =
  let nfa = automatize dir (QNMFormula quas m)
   in minimize (fromIntegral (length dir)) (ncompl nfa)
automatize dir (QNMFormula (Qua (Exists, v) : quas) m) =
  let nfa = automatize dir (QNMFormula quas m)
   in case M.lookup (Var v) dir of
        Nothing -> nfa
        (Just i) -> minimize (fromIntegral $ length dir) $ existentialize i nfa

assign :: S.Set Addend -> M.Map Addend Int
assign xs = M.fromList (zip (S.toList xs) [0 ..])

collect :: Matrix -> S.Set Addend
collect (MEq as bs) = S.fromList (as ++ bs)
collect (MLe a b) = S.fromList [a, b]
collect (MLt a b) = S.fromList [a, b]
collect (MAnd x y) = S.union (collect x) (collect y)
collect (MOr x y) = S.union (collect x) (collect y)
collect (MNot x) = collect x

literals :: M.Map Addend Int -> [[Int]]
literals m =
  let addends = L.sortOn snd (M.toList m)
      reversedLiterals = map (\(a, i) -> addendReverseBinary a) addends
      max = L.maximum (map length reversedLiterals)
      paddedReversed = map (\x -> x ++ replicate (max - length x) 0) reversedLiterals
      padded = map reverse paddedReversed
   in L.transpose padded

addendReverseBinary :: Addend -> [Int]
addendReverseBinary (Var x) = []
addendReverseBinary (Con n) = reverseBinary n

reverseBinary :: Integer -> [Int]
reverseBinary 0 = []
reverseBinary n = fromIntegral (mod n 2) : reverseBinary (div n 2)

eval :: QNMFormula -> Bool
eval f@(QNMFormula q m) =
  let dir = (assign $ collect m)
      nfa = automatize dir f
      input = literals (assign $ collect m)
   in runNFA nfa input

data State a = Single a | Double (State a, State a) | Multi [State a] deriving (Eq, Ord, Show)

data DFA c a = DFA [State a] (State a) [State a] (State a -> c -> State a)

data NFA c a = NFA [State a] [State a] [State a] (State a -> c -> [State a])

runDFA :: (Ord a) => DFA c a -> [c] -> Bool
runDFA (DFA _ start accepts f) cs = foldl f start cs `elem` accepts

runNFA :: (Ord a) => NFA c a -> [c] -> Bool
runNFA (NFA _ starts accepts f) cs =
  foldl (\xs c -> L.nub $ concatMap (`f` c) xs) starts cs `L.intersect` accepts /= []

reversal :: (Ord a) => NFA c a -> NFA c a
reversal (NFA states starts accepts f) = NFA states accepts starts f'
  where
    f' s c = filter (\state -> s `elem` f state c) states

eq :: Integer -> [Int] -> [Int] -> DFA [Int] Int
eq n is js = determinize $ minimize n $ reversal $ nondeterminize dfa
  where
    states = Single <$> [- (length js - 1) .. length is - 1 + 1]
    start = Single 0
    accepts = [Single 0]
    rejector = last states
    f :: State Int -> [Int] -> State Int
    f carrystate@(Single carry) c =
      if carrystate == rejector
        then rejector
        else
          let si = sum (map (c !!) is)
              sj = sum (map (c !!) js)
              parityok = mod (carry + si) 2 == mod sj 2
              newcarry = div (carry + si - sj) 2
           in if parityok
                then Single newcarry
                else rejector
    dfa = DFA states start accepts f

le :: Int -> Int -> DFA [Int] Int
le = less LessEqual

lt :: Int -> Int -> DFA [Int] Int
lt = less LessThan

data LessType = LessEqual | LessThan deriving (Eq, Ord, Show)

less :: LessType -> Int -> Int -> DFA [Int] Int
less lt i j = DFA [Single 0, Single 1, Single 2] (Single 0) accepts f
  where
    accepts = if lt == LessEqual then [Single 0, Single 2] else [Single 2]
    f s c = case (s, (c !! i, c !! j)) of
      (Single 0, (1, 1)) -> Single 0
      (Single 0, (0, 0)) -> Single 0
      (Single 0, (1, 0)) -> Single 1
      (Single 0, _) -> Single 2
      (Single 1, _) -> Single 1
      (_, _) -> Single 2

prod :: [a] -> [b] -> [(a, b)]
prod xs [] = []
prod [] ys = []
prod (x : xs) ys = fmap (x,) ys ++ prod xs ys

data JunctionType = Conj | Disj deriving (Eq, Ord, Show)

junction :: (Ord a) => JunctionType -> DFA c a -> DFA c a -> DFA c a
junction jt (DFA states1 start1 accepts1 f1) (DFA states2 start2 accepts2 f2) =
  DFA states' start' accepts' f'
  where
    newStates = prod states1 states2
    states' = Double <$> newStates
    start' = Double (start1, start2)
    accepts' =
      if jt == Conj
        then Double <$> prod accepts1 accepts2
        else Double <$> filter (\(s, t) -> s `elem` accepts1 || t `elem` accepts2) newStates
    f' (Double (s, t)) c = Double (f1 s c, f2 t c)

conj :: (Ord a) => DFA c a -> DFA c a -> DFA c a
conj = junction Conj

disj :: (Ord a) => DFA c a -> DFA c a -> DFA c a
disj = junction Disj

compl :: (Ord a) => DFA c a -> DFA c a
compl (DFA states start accepts f) =
  DFA states start (states L.\\ accepts) f

nondeterminize :: (Ord a) => DFA c a -> NFA c a
nondeterminize (DFA states start accepts f) =
  NFA states [start] accepts f'
  where
    f' s c = [f s c]

change :: [a] -> Int -> a -> [a]
change xs idx b = take idx xs ++ [b] ++ drop (idx + 1) xs

closure :: (Ord a) => NFA c a -> [c] -> [State a] -> [State a]
closure nfa@(NFA states starts accepts f) cs initstates =
  let new = concatMap (\state -> concatMap (f state) cs) initstates
   in if L.nub new L.\\ L.nub initstates /= []
        then closure nfa cs (L.nub $ new ++ initstates)
        else L.nub initstates

existentialize :: (Ord a) => Int -> NFA [Int] a -> NFA [Int] a
existentialize idx nfa@(NFA states starts accepts f) =
  NFA states starts' accepts f'
  where
    zeroer = replicate 50 0
    oneer = change zeroer idx 1
    starts' = closure nfa [zeroer, oneer] starts
    f' s c = f s (change c idx 0) ++ f s (change c idx 1)

powerset :: [a] -> [[a]]
powerset [] = [[]]
powerset (x : xs) = let rest = powerset xs in map (x :) rest ++ rest

determinize :: (Ord a) => NFA c a -> DFA c a
determinize (NFA states start accepts f) =
  DFA states' start' accepts' f'
  where
    newStates = map L.sort $ powerset states
    states' = Multi <$> newStates
    start' = Multi $ L.sort start
    accepts' = Multi <$> filter (\state' -> state' `L.intersect` accepts /= []) newStates
    f' (Multi s) c = Multi $ L.nub $ L.sort $ concatMap (`f` c) s

ncompl :: (Ord a) => NFA c a -> NFA c a
ncompl = nondeterminize . compl . determinize

chars :: Integer -> [[Int]]
chars 0 = [[]]
chars n =
  let r = chars (n -1)
   in map (1 :) r ++ map (0 :) r

minimize :: (Ord a) => Integer -> NFA [Int] a -> NFA [Int] a
minimize n nfa@(NFA _ starts accepts f) = NFA states' starts' accepts' f
  where
    states' = closure nfa (chars n) starts
    starts' = starts `L.intersect` states'
    accepts' = accepts `L.intersect` states'