module Engine.DataRecycler where

import RIO

import Control.Concurrent.Chan.Unagi qualified as Unagi

data DataRecycler a = DataRecycler
  { drDump :: DumpResource a
    {- ^
      Filled with resources which aren't destroyed after finishing a frame,
      but instead are used by another frame which executes after that one is
      retired, (taken from ghRecycleOut)

      Make sure not to pass any resources which were created with a frame-only
      scope however!
    -}
  , drWait :: WaitResource a
    -- ^ The resources of prior frames waiting to be taken
  }

type DumpResource a = a -> IO ()

type WaitResource a = IO (Either (IO a) a)

new :: MonadIO m => m (DataRecycler a)
new = do
  (recycleWrite, recycleRead) <- liftIO Unagi.newChan
  pure DataRecycler
    { drDump = Unagi.writeChan recycleWrite
    , drWait = do
        (tryOp, blockOp) <- Unagi.tryReadChan recycleRead
        res <- Unagi.tryRead tryOp
        pure $ maybe (Left blockOp) Right res
    }