Progressively reveal the map to the player

As the character walks around the map, progressively reveal the entities
on the map to them, using an algorithm based on well known
circle-rasterizing and line-rasterizing algorithms to calculate lines of
sight that are potentially obscured by walls.

src/Xanthous/Data/EntityMap.hs

@@ -1,27 +1,31 @@
-{-# LANGUAGE DeriveTraversable #-}
-{-# LANGUAGE TupleSections #-}
-{-# LANGUAGE TemplateHaskell #-}
+{-# LANGUAGE UndecidableInstances #-}
+{-# LANGUAGE RecordWildCards #-}
+{-# LANGUAGE DeriveTraversable  #-}
+{-# LANGUAGE TupleSections      #-}
+{-# LANGUAGE TemplateHaskell    #-}
 {-# LANGUAGE StandaloneDeriving #-}
-{-# LANGUAGE DeriveFunctor #-}
-
+{-# LANGUAGE DeriveFunctor      #-}
+--------------------------------------------------------------------------------
 module Xanthous.Data.EntityMap
   ( EntityMap
+  , _EntityMap
   , EntityID
   , emptyEntityMap
   , insertAt
   , insertAtReturningID
+  , fromEIDsAndPositioned
   , atPosition
+  , atPositionWithIDs
   , positions
   , lookup
   , lookupWithPosition
   -- , positionedEntities
   , neighbors
+  , Deduplicate(..)
+
+    -- * Querying an entityMap
   ) where
-
-import Data.Monoid (Endo(..))
-import Test.QuickCheck (Arbitrary(..))
-import Test.QuickCheck.Checkers (EqProp)
-
+--------------------------------------------------------------------------------
 import Xanthous.Prelude hiding (lookup)
 import Xanthous.Data
   ( Position
@@ -33,7 +37,11 @@ import Xanthous.Data
   )
 import Xanthous.Orphans ()
 import Xanthous.Util (EqEqProp(..))
-
+--------------------------------------------------------------------------------
+import Data.Monoid (Endo(..))
+import Test.QuickCheck (Arbitrary(..))
+import Test.QuickCheck.Checkers (EqProp)
+--------------------------------------------------------------------------------
 type EntityID = Word32
 type NonNullVector a = NonNull (Vector a)
 
@@ -43,7 +51,7 @@ data EntityMap a where
     , _byID       :: HashMap EntityID (Positioned a)
     , _lastID     :: EntityID
     } -> EntityMap a
-  deriving stock (Functor, Foldable, Traversable)
+  deriving stock (Functor, Foldable, Traversable, Generic)
 deriving via (EqEqProp (EntityMap a)) instance Eq a => EqProp (EntityMap a)
 makeLenses ''EntityMap
 
@@ -85,9 +93,36 @@ instance At (EntityMap a) where
       removeEIDAtPos pos =
         byPosition . at pos %~ (>>= fromNullable . nfilter (/= eid))
 
+instance Semigroup (EntityMap a) where
+  em₁ <> em₂ = alaf Endo foldMap (uncurry insertAt) (em₂ ^. _EntityMap) em₁
+
+instance Monoid (EntityMap a) where
+  mempty = emptyEntityMap
+
 emptyEntityMap :: EntityMap a
 emptyEntityMap = EntityMap mempty mempty 0
 
+newtype Deduplicate a = Deduplicate (EntityMap a)
+  deriving stock (Show, Traversable, Generic)
+  deriving newtype (Eq, Functor, Foldable, EqProp, Arbitrary)
+
+instance Semigroup (Deduplicate a) where
+  (Deduplicate em₁) <> (Deduplicate em₂) =
+    let _byID = em₁ ^. byID <> em₂ ^. byID
+        _byPosition = mempty &~ do
+          ifor_ _byID $ \eid (Positioned pos _) ->
+            at pos %= \case
+              Just eids -> Just $ eid <| eids
+              Nothing -> Just $ ncons eid mempty
+        _lastID = fromMaybe 1 $ maximumOf (ifolded . asIndex) _byID
+    in Deduplicate EntityMap{..}
+
+instance Monoid (Deduplicate a) where
+  mempty = Deduplicate emptyEntityMap
+
+
+--------------------------------------------------------------------------------
+
 _EntityMap :: Iso' (EntityMap a) [(Position, a)]
 _EntityMap = iso hither yon
   where
@@ -100,12 +135,6 @@ _EntityMap = iso hither yon
     yon :: [(Position, a)] -> EntityMap a
     yon poses = alaf Endo foldMap (uncurry insertAt) poses emptyEntityMap
 
-instance Semigroup (EntityMap a) where
-  em₁ <> em₂ = alaf Endo foldMap (uncurry insertAt) (em₂ ^. _EntityMap) em₁
-
-instance Monoid (EntityMap a) where
-  mempty = emptyEntityMap
-
 
 insertAtReturningID :: forall a. Position -> a -> EntityMap a -> (EntityID, EntityMap a)
 insertAtReturningID pos e em =
@@ -124,17 +153,37 @@ atPosition :: forall a. Position -> Lens' (EntityMap a) (Vector a)
 atPosition pos = lens getter setter
   where
     getter em =
-      let
-        eids :: Vector EntityID
-        eids = maybe mempty toNullable $ em ^. byPosition . at pos
-
-        getEIDAssume :: EntityID -> a
-        getEIDAssume eid = fromMaybe byIDInvariantError
-          $ em ^? byID . ix eid . positioned
-      in getEIDAssume <$> eids
+      let eids :: Vector EntityID
+          eids = maybe mempty toNullable $ em ^. byPosition . at pos
+      in getEIDAssume em <$> eids
     setter em Empty = em & byPosition . at pos .~ Nothing
     setter em entities = alaf Endo foldMap (insertAt pos) entities em
 
+getEIDAssume :: EntityMap a -> EntityID -> a
+getEIDAssume em eid = fromMaybe byIDInvariantError
+  $ em ^? byID . ix eid . positioned
+
+atPositionWithIDs :: Position -> EntityMap a -> Vector (EntityID, Positioned a)
+atPositionWithIDs pos em =
+  let eids = maybe mempty toNullable $ em ^. byPosition . at pos
+  in (id &&& Positioned pos . getEIDAssume em) <$> eids
+
+fromEIDsAndPositioned
+  :: (MonoFoldable mono, Element mono ~ (EntityID, Positioned a))
+  => mono
+  -> EntityMap a
+fromEIDsAndPositioned eps = newLastID $ alaf Endo foldMap insert' eps mempty
+  where
+    insert' (eid, pe@(Positioned pos _))
+      = (byID . at eid ?~ pe)
+      . (byPosition . at pos %~ \case
+            Just eids -> Just $ eid <| eids
+            Nothing   -> Just $ ncons eid mempty
+        )
+    newLastID em = em & lastID
+      .~ fromMaybe 1
+         (maximumOf (ifolded . asIndex) (em ^. byID))
+
 positions :: EntityMap a -> [Position]
 positions = toListOf $ byPosition . to keys . folded
 
@@ -150,3 +199,6 @@ lookup eid = fmap (view positioned) . lookupWithPosition eid
 
 neighbors :: Position -> EntityMap a -> Neighbors (Vector a)
 neighbors pos em = (\p -> view (atPosition p) em) <$> neighborPositions pos
+
+--------------------------------------------------------------------------------
+makeWrapped ''Deduplicate