{-# LANGUAGE CPP #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE LambdaCase #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE RankNTypes #-}
{-# LANGUAGE RecursiveDo #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE UndecidableInstances #-}
#ifdef USE_REFLEX_OPTIMIZER
{-# OPTIONS_GHC -fplugin=Reflex.Optimizer #-}
#endif
-- |
-- Module:
--   Reflex.Collection
module Reflex.Collection
  (
  -- * Widgets on Collections
    listHoldWithKey
  , listWithKey
  , listWithKeyShallowDiff
  , listViewWithKey
  , selectViewListWithKey
  , selectViewListWithKey_
  -- * List Utils
  , list
  , simpleList
  ) where

#ifdef MIN_VERSION_semialign
import Prelude hiding (zip, zipWith)
#if MIN_VERSION_semialign(1,1,0)
import Data.Zip (Zip (..))
#endif
#endif

import Control.Monad
import Control.Monad.Fix
import Control.Monad.Identity
import Data.Align
import Data.Functor.Misc
import Data.Map (Map)
import qualified Data.Map as Map
import Data.Map.Misc
import Data.These

import Reflex.Class
import Reflex.Adjustable.Class
import Reflex.Dynamic
import Reflex.PostBuild.Class

-- | Create a set of widgets based on the provided 'Map'. When the
-- input 'Event' fires, remove widgets for keys with the value 'Nothing'
-- and add/replace widgets for keys with 'Just' values.
listHoldWithKey
  :: forall t m k v a
   . (Ord k, Adjustable t m, MonadHold t m)
  => Map k v
  -> Event t (Map k (Maybe v))
  -> (k -> v -> m a)
  -> m (Dynamic t (Map k a))
listHoldWithKey m0 m' f = do
  let dm0 = mapWithFunctorToDMap $ Map.mapWithKey f m0
      dm' = fmap
        (PatchDMap . mapWithFunctorToDMap . Map.mapWithKey
          (\k v -> ComposeMaybe $ fmap (f k) v)
        )
        m'
  (a0, a') <- sequenceDMapWithAdjust dm0 dm'

  --TODO: Move the dmapToMap to the righthand side so it doesn't get
  --fully redone every time
  fmap dmapToMap . incrementalToDynamic <$> holdIncremental a0 a'

--TODO: Something better than Dynamic t (Map k v) - we want something
--where the Events carry diffs, not the whole value
listWithKey
  :: forall t k v m a
   . (Ord k, Adjustable t m, PostBuild t m, MonadFix m, MonadHold t m, Eq v)
  => Dynamic t (Map k v)
  -> (k -> Dynamic t v -> m a)
  -> m (Dynamic t (Map k a))
listWithKey vals mkChild = do
  postBuild <- getPostBuild
  let childValChangedSelector = fanMap $ updated vals

      -- We keep track of changes to children values in the mkChild
      -- function we pass to listHoldWithKey The other changes we need
      -- to keep track of are child insertions and
      -- deletions. diffOnlyKeyChanges keeps track of insertions and
      -- deletions but ignores value changes, since they're already
      -- accounted for.
      diffOnlyKeyChanges olds news =
        flip Map.mapMaybe (align olds news) $ \case
          This _    -> Just Nothing
          These _ _ -> Nothing
          That new  -> Just $ Just new
  rec sentVals :: Dynamic t (Map k v) <- foldDyn applyMap Map.empty changeVals
      let changeVals :: Event t (Map k (Maybe v))
          changeVals =
            attachWith diffOnlyKeyChanges (current sentVals) $ leftmost
              [ updated vals

              -- TODO: This should probably be added to the
              -- attachWith, not to the updated; if we were using
              -- diffMap instead of diffMapNoEq, I think it might not
              -- work
              , tag (current vals) postBuild
              ]
  listHoldWithKey Map.empty changeVals $ \k v ->
    mkChild k =<< holdUniqDyn =<< holdDyn v (select childValChangedSelector $ Const2 k)

-- | Display the given map of items (in key order) using the builder
-- function provided, and update it with the given event.  'Nothing'
-- update entries will delete the corresponding children, and 'Just'
-- entries will create them if they do not exist or send an update
-- event to them if they do.
listWithKeyShallowDiff
  :: (Ord k, Adjustable t m, MonadFix m, MonadHold t m)
  => Map k v
  -> Event t (Map k (Maybe v))
  -> (k -> v -> Event t v -> m a)
  -> m (Dynamic t (Map k a))
listWithKeyShallowDiff initialVals valsChanged mkChild = do
  let childValChangedSelector = fanMap $ fmap (Map.mapMaybe id) valsChanged
  sentVals <- foldDyn applyMap (void initialVals) $ fmap (fmap void) valsChanged
  let relevantPatch patch _ = case patch of

        -- Even if we let a Nothing through when the element doesn't
        -- already exist, this doesn't cause a problem because it is
        -- ignored
        Nothing -> Just Nothing

        -- We don't want to let spurious re-creations of items through
        Just _  -> Nothing
  listHoldWithKey
      initialVals
      (attachWith (flip (Map.differenceWith relevantPatch))
                  (current sentVals)
                  valsChanged
      )
    $ \k v -> mkChild k v $ select childValChangedSelector $ Const2 k

--TODO: Something better than Dynamic t (Map k v) - we want something
--where the Events carry diffs, not the whole value
-- | Create a dynamically-changing set of Event-valued widgets.  This
--   is like 'listWithKey', specialized for widgets returning @/Event t a/@.
--   'listWithKey' would return @/Dynamic t (Map k (Event t a))/@ in
--   this scenario, but 'listViewWithKey' flattens this to
--   @/Event t (Map k a)/@ via 'switch'.
listViewWithKey
  :: (Ord k, Adjustable t m, PostBuild t m, MonadHold t m, MonadFix m, Eq v)
  => Dynamic t (Map k v)
  -> (k -> Dynamic t v -> m (Event t a))
  -> m (Event t (Map k a))
listViewWithKey vals mkChild =
  switch . fmap mergeMap <$> listViewWithKey' vals mkChild

listViewWithKey'
  :: (Ord k, Adjustable t m, PostBuild t m, MonadHold t m, MonadFix m, Eq v)
  => Dynamic t (Map k v)
  -> (k -> Dynamic t v -> m a)
  -> m (Behavior t (Map k a))
listViewWithKey' vals mkChild = current <$> listWithKey vals mkChild

-- | Create a dynamically-changing set of widgets, one of which is
-- selected at any time.
selectViewListWithKey
  :: forall t m k v a
   . (Adjustable t m, Ord k, PostBuild t m, MonadHold t m, MonadFix m, Eq v)
  => Dynamic t k
  -- ^ Current selection key
  -> Dynamic t (Map k v)
  -- ^ Dynamic key/value map
  -> (k -> Dynamic t v -> Dynamic t Bool -> m (Event t a))
  -- ^ Function to create a widget for a given key from Dynamic value
  -- and Dynamic Bool indicating if this widget is currently selected
  -> m (Event t (k, a))
  -- ^ Event that fires when any child's return Event fires.  Contains
  -- key of an arbitrary firing widget.
selectViewListWithKey selection vals mkChild = do
  -- For good performance, this value must be shared across all children
  let selectionDemux = demux selection
  selectChild <- listWithKey vals $ \k v -> do
    let selected = demuxed selectionDemux k
    selectSelf <- mkChild k v selected
    return $ fmap ((,) k) selectSelf
  return $ switchPromptlyDyn $ leftmost . Map.elems <$> selectChild

-- | Like 'selectViewListWithKey' but discards the value of the list
-- item widget's output 'Event'.
selectViewListWithKey_
  :: forall t m k v a
   . (Adjustable t m, Ord k, PostBuild t m, MonadHold t m, MonadFix m, Eq v)
  => Dynamic t k
  -- ^ Current selection key
  -> Dynamic t (Map k v)
  -- ^ Dynamic key/value map
  -> (k -> Dynamic t v -> Dynamic t Bool -> m (Event t a))
  -- ^ Function to create a widget for a given key from Dynamic value
  -- and Dynamic Bool indicating if this widget is currently selected
  -> m (Event t k)
  -- ^ Event that fires when any child's return Event fires.  Contains
  -- key of an arbitrary firing widget.
selectViewListWithKey_ selection vals mkChild =
  fmap fst <$> selectViewListWithKey selection vals mkChild

-- | Create a dynamically-changing set of widgets from a Dynamic
--   key/value map.  Unlike the 'withKey' variants, the child widgets
--   are insensitive to which key they're associated with.
list
  :: (Ord k, Adjustable t m, MonadHold t m, PostBuild t m, MonadFix m, Eq v)
  => Dynamic t (Map k v)
  -> (Dynamic t v -> m a)
  -> m (Dynamic t (Map k a))
list dm mkChild = listWithKey dm (\_ dv -> mkChild dv)

-- | Create a dynamically-changing set of widgets from a Dynamic list.
simpleList
  :: (Adjustable t m, MonadHold t m, PostBuild t m, MonadFix m, Eq v)
  => Dynamic t [v]
  -> (Dynamic t v -> m a)
  -> m (Dynamic t [a])
simpleList xs mkChild =
  fmap (fmap (map snd . Map.toList)) $ flip list mkChild $ fmap
    (Map.fromList . zip [(1 :: Int) ..])
    xs