-----------------------------------------------------------------------------
-- |
-- Module      :  Miso.Diff
-- Copyright   :  (C) 2016-2017 David M. Johnson
-- License     :  BSD3-style (see the file LICENSE)
-- Maintainer  :  David M. Johnson <djohnson.m@gmail.com>
-- Stability   :  experimental
-- Portability :  non-portable
----------------------------------------------------------------------------
module Miso.Diff ( diff ) where

import GHCJS.Foreign.Internal     hiding (Object)
import GHCJS.Types
import JavaScript.Object
import JavaScript.Object.Internal
import Miso.Html.Internal

-- | Entry point for diffing / patching algorithm
diff :: Maybe VTree -> Maybe VTree -> IO ()
diff current new = do
  body <- getBody
  case (current, new) of
    (Nothing, Nothing) -> pure ()
    (Just (VTree current'), Just (VTree new')) -> do
      diff' current' new' body
    (Nothing, Just (VTree new')) -> do
      diff' (Object jsNull) new' body
    (Just (VTree current'), Nothing) -> do
      diff' current' (Object jsNull) body

foreign import javascript unsafe "$r = document.body;"
  getBody :: IO JSVal

foreign import javascript unsafe "diff($1, $2, $3);"
  diff'
    :: Object -- ^ current object
    -> Object -- ^ new object
    -> JSVal  -- ^ parent node
    -> IO ()