{-# LANGUAGE OverloadedStrings, NamedFieldPuns #-}

module Evaluate where

import Base (State(..), BFAction(..))
import Memory
import Formatter

import qualified Data.HashMap as HM
import qualified Data.Text as T
import qualified Data.Text.IO as T

type ActionResult = (State, Maybe (IO ()))

processAction :: State -> BFAction -> ActionResult
processAction s@State {pointer, memory, codePos, jumpTable} instruction = let
    noIO :: State -> ActionResult
    noIO s = (s, Nothing)

    jump :: ActionResult
    jump = case HM.lookup codePos jumpTable of
             Just jumpTo -> noIO $ s { pointer = jumpTo }
             Nothing -> (s, Just $ T.putStrLn "ERROR: no matching jump point")
  in case instruction of
    MoveRight -> noIO $ s { pointer = pointer + 1 }
    MoveLeft -> noIO $ s { pointer = pointer - 1 }
    Increment -> noIO $ s { memory = increment memory pointer }
    Decrement -> noIO $ s { memory = decrement memory pointer }
    Replace -> noIO $ s { memory = setMemAdr memory pointer $ getMemAdr memory $ getMemAdr memory pointer }
    Print -> (s, Just $ prettyPrintState' s)
    JumpRight -> jump
    JumpLeft -> jump