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{-# LANGUAGE StandaloneDeriving #-}
{-# LANGUAGE RecordWildCards #-}
{-# LANGUAGE TemplateHaskell #-}
--------------------------------------------------------------------------------
module Xanthous.Data.Levels
( Levels
, allLevels
, nextLevel
, prevLevel
, mkLevels1
, mkLevels
, oneLevel
, current
, ComonadStore(..)
) where
--------------------------------------------------------------------------------
import Xanthous.Prelude hiding ((<.>), Empty, foldMap, levels)
import Xanthous.Util (between, EqProp, EqEqProp(..))
import Xanthous.Util.Comonad (current)
import Xanthous.Orphans ()
--------------------------------------------------------------------------------
import Control.Comonad.Store
import Control.Comonad.Store.Zipper
import Data.Aeson (ToJSON(..), FromJSON(..))
import Data.Aeson.Generic.DerivingVia
import Data.Functor.Apply
import Data.Foldable (foldMap)
import Data.List.NonEmpty (NonEmpty)
import qualified Data.List.NonEmpty as NE
import Data.Maybe (fromJust)
import Data.Sequence (Seq((:<|), Empty))
import Data.Semigroup.Foldable.Class
import Data.Text (replace)
import Test.QuickCheck
--------------------------------------------------------------------------------
-- | Collection of levels plus a pointer to the current level
--
-- Navigation is via the 'Comonad' instance. We can get the current level with
-- 'extract':
--
-- extract @Levels :: Levels level -> level
--
-- For access to and modification of the level, use
-- 'Xanthous.Util.Comonad.current'
newtype Levels a = Levels { levelZipper :: Zipper Seq a }
deriving stock (Generic)
deriving (Functor, Comonad, Foldable) via (Zipper Seq)
deriving (ComonadStore Int) via (Zipper Seq)
type instance Element (Levels a) = a
instance MonoFoldable (Levels a)
instance MonoFunctor (Levels a)
instance MonoTraversable (Levels a)
instance Traversable Levels where
traverse f (Levels z) = Levels <$> traverse f z
instance Foldable1 Levels
instance Traversable1 Levels where
traverse1 f (Levels z) = seek (pos z) . partialMkLevels <$> go (unzipper z)
where
go Empty = error "empty seq, unreachable"
go (x :<| xs) = (<|) <$> f x <.> go xs
-- | Always takes the position of the latter element
instance Semigroup (Levels a) where
levs₁ <> levs₂
= seek (pos levs₂)
. partialMkLevels
$ allLevels levs₁ <> allLevels levs₂
-- | Make Levels from a Seq. Throws an error if the seq is not empty
partialMkLevels :: Seq a -> Levels a
partialMkLevels = Levels . fromJust . zipper
-- | Make Levels from a possibly-empty structure
mkLevels :: Foldable1 f => f level -> Maybe (Levels level)
mkLevels = fmap Levels . zipper . foldMap pure
-- | Make Levels from a non-empty structure
mkLevels1 :: Foldable1 f => f level -> Levels level
mkLevels1 = fromJust . mkLevels
oneLevel :: a -> Levels a
oneLevel = mkLevels1 . Identity
-- | Get a sequence of all the levels
allLevels :: Levels a -> Seq a
allLevels = unzipper . levelZipper
-- | Step to the next level, generating a new level if necessary using the given
-- applicative action
nextLevel
:: Applicative m
=> m level -- ^ Generate a new level, if necessary
-> Levels level
-> m (Levels level)
nextLevel genLevel levs
| pos levs + 1 < size (levelZipper levs)
= pure $ seeks succ levs
| otherwise
= genLevel <&> \level ->
seek (pos levs + 1) . partialMkLevels $ level <| allLevels levs
-- | Go to the previous level. Returns Nothing if 'pos' is 0
prevLevel :: Levels level -> Maybe (Levels level)
prevLevel levs | pos levs == 0 = Nothing
| otherwise = Just $ seeks pred levs
--------------------------------------------------------------------------------
-- | alternate, slower representation of Levels we can Iso into to perform
-- various operations
data AltLevels a = AltLevels
{ _levels :: NonEmpty a
, _currentLevel :: Int -- ^ invariant: is within the bounds of _levels
}
deriving stock (Show, Eq, Generic)
deriving anyclass (NFData, CoArbitrary, Function)
deriving (ToJSON, FromJSON)
via WithOptions '[ FieldLabelModifier '[Drop 1] ]
(AltLevels a)
makeLenses ''AltLevels
alt :: Iso (Levels a) (Levels b) (AltLevels a) (AltLevels b)
alt = iso hither yon
where
hither levs = AltLevels (NE.fromList . toList $ allLevels levs) (pos levs)
yon (AltLevels levs curr) = seek curr $ mkLevels1 levs
instance Eq a => Eq (Levels a) where
(==) = (==) `on` view alt
deriving via EqEqProp (Levels a) instance Eq a => EqProp (Levels a)
instance Show a => Show (Levels a) where
show = unpack . replace "AltLevels" "Levels" . pack . show . view alt
instance NFData a => NFData (Levels a) where
rnf = rnf . view alt
instance ToJSON a => ToJSON (Levels a) where
toJSON = toJSON . view alt
instance FromJSON a => FromJSON (Levels a) where
parseJSON = fmap (review alt) . parseJSON
instance Arbitrary a => Arbitrary (AltLevels a) where
arbitrary = do
_levels <- arbitrary
_currentLevel <- choose (0, length _levels - 1)
pure AltLevels {..}
shrink als = do
_levels <- shrink $ als ^. levels
_currentLevel <- filter (between 0 $ length _levels - 1)
$ shrink $ als ^. currentLevel
pure AltLevels {..}
instance Arbitrary a => Arbitrary (Levels a) where
arbitrary = review alt <$> arbitrary
shrink = fmap (review alt) . shrink . view alt
instance CoArbitrary a => CoArbitrary (Levels a) where
coarbitrary = coarbitrary . view alt
instance Function a => Function (Levels a) where
function = functionMap (view alt) (review alt)
|
