module Indexation.Potoki.Transform
(
  Transform,
  Index(..),
  Indexer,
  EntityTable,
  ReindexTable,
  index,
  reindex,
  lookup,
)
where

import Indexation.Prelude hiding (runState, index, lookup)
import Indexation.Types
import Indexation.Instances ()
import Potoki.Transform
import qualified Focus
import qualified StmContainers.Map as StmMap
import qualified Data.Vector as Vector
import qualified Indexation.Functions as Functions


index :: (Eq entity, Hashable entity) => Indexer entity -> Transform entity (Index entity)
index (Indexer sizeVar map) =
  {-# SCC "index" #-} 
  mapInIO $ \ entity -> atomically $ StmMap.focus focus entity map
  where
    focus = Focus.Focus conceal reveal where
      conceal = do
        size <- readTVar sizeVar
        writeTVar sizeVar $! succ size
        return (Index size, Focus.Set size)
      reveal indexInt = return (Index indexInt, Focus.Leave)

reindex :: ReindexTable entity -> Transform (Index entity) (Index entity)
reindex table = mapFilter (\ oldIndex -> Functions.lookupNewIndex oldIndex table)

lookup :: EntityTable entity -> Transform (Index entity) (Maybe entity)
lookup (EntityTable entityTableVector) =
  {-# SCC "lookup" #-} 
  arr $ \ (Index indexInt) -> if Vector.length entityTableVector > indexInt
    then Just $! Vector.unsafeIndex entityTableVector indexInt
    else Nothing