{-

here i show how to use lenses to handle states (didnt found any example on states in internet)

-}


{-# LANGUAGE TemplateHaskell #-}
import Lens.Micro.TH (makeLenses)
import Lens.Micro ((%~), (.~), (&), _2)
import Lens.Micro.Platform (at)  -- Correct import for Map operations
import Data.IORef (IORef, newIORef, modifyIORef', readIORef)
import Data.Map (Map)
import qualified Data.Map as Map


data AppState = AppState
  { _ui :: UIState
  , _user :: User
  } deriving (Show)  

data UIState = UIState
  { _theme :: String
  , _windowSize :: (Int, Int)
  , _keyBindings :: Map String String
  } deriving (Show)  

data User = User
  { _name :: String
  , _prefs :: UserPrefs
  } deriving (Show) 

data UserPrefs = UserPrefs
  { _fontSize :: Int
  , _darkMode :: Bool
  } deriving (Show) 


makeLenses ''AppState
makeLenses ''UIState
makeLenses ''User
makeLenses ''UserPrefs

main :: IO ()
main = do
  let initialState = AppState
        { _ui = UIState
          { _theme = "light"
          , _windowSize = (800, 600)
          , _keyBindings = Map.fromList [("Ctrl+S", "save")]
          }
        , _user = User
          { _name = "Alice"
          , _prefs = UserPrefs
            { _fontSize = 12
            , _darkMode = False
            }
          }
        }

  stateRef <- newIORef initialState

  -- Corrected lens chain with &
  {-
  & is just backwards function application;
  x f , in which f will be applied to the value x 
  -}
  modifyIORef' stateRef $ \s ->
    s & ui . keyBindings . at "Ctrl+X" .~ Just "cut"
      & user . prefs . darkMode .~ True
      & ui . windowSize . _2 %~ (+100)

  finalState <- readIORef stateRef
  print finalState