module React.Hook where

import Prelude hiding ((!!))

import Control.Monad
import Control.Monad.Except
import Control.Monad.Reader
import Language.Javascript.JSaddle hiding (Ref)

import React.JSaddle
import React.Misc
import React.Types

--TODO: Input can be an initializer function rather than value
--TODO: `set` can take `a -> a` instead of `a`
--TODO: I bet React always returns the same function object for the setter; if we re-wrap the function using `useCallback` each time, we are probably hurting performance by making it be a new object each time and forcing rerendering of children
useState :: (ToJSVal a, FromJSVal a) => a -> Hook (a, a -> JSM ())
useState initialValue = Hook $ do
  react <- ask
  initialJSVal <- lift $ toJSVal initialValue
  result <- lift $ (react # t "useState") initialJSVal
  Just s <- lift $ fromJSVal =<< result !! 0 --TODO: Exception handling
  setter <- lift $ result !! 1
  pure
    ( s
    , \v' -> void $ call setter nullObject [v']
    )

useRef :: JSVal -> Hook JSVal
useRef initialValue = Hook $ do
  react <- ask
  lift $ (react # t "useRef") initialValue

useEffect :: (JSVal -> JSVal -> [JSVal] -> JSM JSVal) -> Maybe [JSVal] -> Hook ()
useEffect f deps = Hook $ do
  react <- ask
  Function' _ cb <- lift $ function' f
  depsArg <- case deps of
    Nothing -> pure []
    Just someDeps -> do
      depsArray <- lift $ toJSVal someDeps
      pure [depsArray]
  _ <- lift $ (react # t "useEffect") $ [pToJSVal cb] <> depsArg
  pure ()

useMemo :: (ToJSVal a, FromJSVal a) => JSM a -> Maybe [JSVal] -> Hook a
useMemo a deps = Hook $ do
  react <- ask
  Function' _ cb <- lift $ function' $ \_ _ _ -> toJSVal =<< a
  depsArg <- case deps of
    Nothing -> pure []
    Just someDeps -> do
      depsArray <- lift $ toJSVal someDeps
      pure [depsArray]
  resultVal <- lift $ (react # t "useMemo") $ [pToJSVal cb] <> depsArg
  Just result <- lift $ fromJSVal resultVal
  pure result

useCallback :: ToJSVal result => (JSVal -> JSVal -> [JSVal] -> JSM result) -> Maybe [JSM JSVal] -> Hook JSVal
useCallback f deps = Hook $ do
  react <- ask
  Function' _ cb <- lift $ function' $ \fObj this args -> toJSVal =<< f fObj this args
  depsArg <- case deps of
    Nothing -> pure []
    Just someDeps -> do
      depsArray <- lift $ toJSVal =<< sequence someDeps
      pure [depsArray]
  lift $ (react # t "useCallback") $ [pToJSVal cb] <> depsArg