module Vm where

import Control.Monad.Trans.State as St

data Instr = Noop | Addx Integer
data CpuState = CS {regx :: Integer, step :: Integer}

initState = CS 1 0

eval :: Instr -> St.State CpuState ()
eval Noop = do
    s <- St.get
    put $ s {step = step s + 1}

eval (Addx i) = do
    s <- St.get
    let step' = step s + 2
    let x' = regx s + i
    put $ CS x' step'

instrFromWords :: [String] -> Instr
instrFromWords ["noop"] = Noop
instrFromWords ["addx", i] = Addx (read i)

readProgram :: IO [Instr]
readProgram = do
    x <- lines <$> getContents
    pure $ map (instrFromWords . words) x