feat(gs/xanthous): Creatures drop their items when they die r/3099

When a creature is killed, it now drops all the contents of its
inventory on the ground.

Change-Id: Ie95c397308ba2c9861f10e58b99c91c9cc759c56

3 files changed, 24 insertions, 4 deletions

diff --git a/users/grfn/xanthous/src/Xanthous/App.hs b/users/grfn/xanthous/src/Xanthous/App.hs
index b29614383bcd..a251833955cd 100644
--- a/users/grfn/xanthous/src/Xanthous/App.hs
+++ b/users/grfn/xanthous/src/Xanthous/App.hs
@@ -48,17 +48,18 @@ import           Xanthous.Game.Draw (drawGame)
 import           Xanthous.Game.Prompt hiding (Fire)
 import qualified Xanthous.Messages as Messages
 import           Xanthous.Random
-import           Xanthous.Util (removeVectorIndex)
+import           Xanthous.Util (removeVectorIndex, useListOf)
 import           Xanthous.Util.Inflection (toSentence)
 import           Xanthous.Physics (throwDistance, bluntThrowDamage)
 import           Xanthous.Data.EntityMap.Graphics (lineOfSight)
 import           Xanthous.Data.EntityMap (EntityID)
 --------------------------------------------------------------------------------
+--------------------------------------------------------------------------------
 import           Xanthous.Entities.Common
                  ( InventoryPosition, describeInventoryPosition, backpack
                  , wieldableItem, wieldedItems, wielded, itemsWithPosition
                  , removeItemFromPosition, asWieldedItem, inRightHand
-                 , wieldedItem
+                 , wieldedItem, items
                  )
 import qualified Xanthous.Entities.Character as Character
 import           Xanthous.Entities.Character hiding (pickUpItem)
@@ -462,7 +463,18 @@ damageCreature (creatureID, creature) dam = do
   if Creature.isDead creature'
     then do
       say ["combat", "killed"] msgParams
+      floorItems <- useListOf
+                   $ entities
+                   . ix creatureID
+                   . positioned
+                   . _SomeEntity @Creature
+                   . inventory
+                   . items
+      mCreaturePos <- preuse $ entities . ix creatureID . position
       entities . at creatureID .= Nothing
+      for_ mCreaturePos $ \creaturePos ->
+        entities . EntityMap.atPosition creaturePos
+          %= (<> fromList (SomeEntity <$> floorItems))
     else entities . ix creatureID . positioned .= SomeEntity creature'
   pure creature'
 
diff --git a/users/grfn/xanthous/src/Xanthous/Entities/Creature.hs b/users/grfn/xanthous/src/Xanthous/Entities/Creature.hs
index 3af2cafe3349..3ea610795e98 100644
--- a/users/grfn/xanthous/src/Xanthous/Entities/Creature.hs
+++ b/users/grfn/xanthous/src/Xanthous/Entities/Creature.hs
@@ -42,7 +42,7 @@ import           Xanthous.Data
 import           Xanthous.Data.Entities
 import           Xanthous.Entities.Creature.Hippocampus
 import           Xanthous.Util.QuickCheck (GenericArbitrary(..))
-import           Xanthous.Entities.Common (Inventory)
+import           Xanthous.Entities.Common (Inventory, HasInventory(..))
 --------------------------------------------------------------------------------
 
 data Creature = Creature
diff --git a/users/grfn/xanthous/src/Xanthous/Util.hs b/users/grfn/xanthous/src/Xanthous/Util.hs
index 6678cffe6a17..f918340f055b 100644
--- a/users/grfn/xanthous/src/Xanthous/Util.hs
+++ b/users/grfn/xanthous/src/Xanthous/Util.hs
@@ -34,7 +34,7 @@ module Xanthous.Util
   , times, times_, endoTimes
 
     -- * State utilities
-  , modifyK, modifyKL
+  , modifyK, modifyKL, useListOf
 
     -- * Type-level programming utils
   , KnownBool(..)
@@ -311,6 +311,14 @@ modifyK k = get >>= k >>= put
 modifyKL :: MonadState s m => LensLike m s s a b -> (a -> m b) -> m ()
 modifyKL l k = get >>= traverseOf l k >>= put
 
+-- | Use a list of all the targets of a 'Fold' in the current state
+--
+-- @@
+-- evalState (useListOf folded) === toList
+-- @@
+useListOf :: MonadState s m => Getting (Endo [a]) s a -> m [a]
+useListOf = gets . toListOf
+
 --------------------------------------------------------------------------------
 
 -- | A newtype wrapper around 'Char' whose 'Enum' and 'Bounded' instances only