import Data.List.Split
import qualified Data.List as L
import Data.Vector as V
import Data.Char
import Control.DeepSeq as DeepSeq

data OutAction = Continue | Output | Halt deriving (Enum, Eq, Show)
data Mode = Position | Immediate | Relative deriving (Enum, Eq, Show)
type Tape = Vector Integer
type TapeSection = Vector Integer
type TuringMachine = (Tape,Integer,Integer)

main = do
    content <- readFile "input"
    let tape = fromList $ L.concatMap (L.map read . splitOn ",") (lines content)
    let (tm,_,out,_) = execSteps ((tapePreprocess tape,0,0),[2],[],Continue)
    print $ L.reverse out

tapePreprocess :: TapeSection -> TapeSection
tapePreprocess t = (V.++) t $ V.replicate 99999 0

opLength :: Integer -> Integer
opLength x
    | n`L.elem`"1278"=4
    | n`L.elem`"56"=3
    | n`L.elem`"349"=2
    | otherwise=1
    where n = L.last $ show x

parseModes :: String -> [Mode]
parseModes m = L.replicate (3 - L.length l) Position L.++ l
    where l = L.map (toEnum . digitToInt) m

paramChange :: [Mode] -> Integer -> TapeSection -> Tape -> TapeSection
paramChange m rbase opvec t = imap f (V.tail opvec)
    where f i a = case m !! i of
                    Immediate -> a
                    Position  -> t ! fromInteger a
                    Relative  -> t ! fromInteger (a + rbase)

getOpModes :: TapeSection -> (String, [Mode])
getOpModes opvec = (op_dedup,parsed_modes)
    where (op,modes) = L.splitAt 2 $ L.reverse $ show $ opvec ! 0
          parsed_modes = L.reverse $ parseModes $ L.reverse modes
          op_dedup = if L.last op == '0' then [L.head op] else op

step :: TapeSection -> (TuringMachine, [Integer], [Integer]) -> (TuringMachine, OutAction, [Integer], [Integer])
step opvec ((t,p,rbase),input,val) = case op of
    "1" -> (tm_binop (+),Continue,input,val)
    "2" -> (tm_binop (*),Continue,input,val)
    "3" -> (new_tm t $ L.head input,Continue,L.tail input,val)
    "4" -> ((t,p,rbase),Output,input,V.last params:val)
    "5" -> ((t, if params ! 0/=0 then params ! 1 else p,rbase),Continue,input,val)
    "6" -> ((t, if params ! 0==0 then params ! 1 else p,rbase),Continue,input,val)
    "7" -> (new_tm t (if (params ! 0)<(params ! 1)
                    then 1 else 0),Continue,input,val)
    "8" -> (new_tm t (if (params ! 0)==(params ! 1)
                    then 1 else 0),Continue,input,val)
    "9" -> ((t,p,rbase + (params ! 0)),Continue,input,val)
    "99" -> ((t,p,rbase),Halt,input,val)
    where (op,m) = getOpModes opvec
          params = paramChange m rbase opvec t
          tm_binop x = new_tm t ((params ! 0) `x` (params ! 1))
          --without the following DeepSeq call, thunks build up eternally
          --and the vectors won’t be garbage collected (>4GB RAM usage)
          new_tm t x = DeepSeq.force (t // [(target, x)],p,rbase)
          target = fromInteger $ case m !! (L.length params -1) of
                     Relative -> V.last opvec + rbase
                     _ -> V.last opvec

execSteps :: (TuringMachine, [Integer], [Integer], OutAction) -> (TuringMachine, [Integer], [Integer], OutAction)
execSteps ((t,p,rbase),input,output,halt) =
    let command_length = opLength $! t ! fromInteger p
        opvec = slice (fromInteger p) (fromInteger command_length) t
        ((t_new,p_new,rbase_new),cond,input_new,output_new) =
            step opvec ((t,p+command_length,rbase),input,output) in
    case cond of
      Halt -> ((t_new,p_new,rbase_new),input_new,output_new,cond)
      _ -> execSteps ((t_new,p_new,rbase_new),input_new,output_new,cond)