refactor(gs/xanthous): Break out inventory into a common module r/3081

Creatures are going to have an inventory too now in addition to
characters, so all the data types and lenses and stuff that define
inventory need to be broken out into a separate module so the Creature
entity can use them.

Change-Id: I83f1c70d316afaaf2e75901f9dc28f79fd2cd31f
Reviewed-on: https://cl.tvl.fyi/c/depot/+/3901
Tested-by: BuildkiteCI
Reviewed-by: grfn <grfn@gws.fyi>

8 files changed, 293 insertions, 247 deletions

diff --git a/users/grfn/xanthous/src/Xanthous/App.hs b/users/grfn/xanthous/src/Xanthous/App.hs
index 78f9e76775d9..b29614383bcd 100644
--- a/users/grfn/xanthous/src/Xanthous/App.hs
+++ b/users/grfn/xanthous/src/Xanthous/App.hs
@@ -54,6 +54,12 @@ 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
+                 )
 import qualified Xanthous.Entities.Character as Character
 import           Xanthous.Entities.Character hiding (pickUpItem)
 import           Xanthous.Entities.Item (Item, weight)
diff --git a/users/grfn/xanthous/src/Xanthous/Entities/Character.hs b/users/grfn/xanthous/src/Xanthous/Entities/Character.hs
index 4d641e46dc48..b86e9e17d3f9 100644
--- a/users/grfn/xanthous/src/Xanthous/Entities/Character.hs
+++ b/users/grfn/xanthous/src/Xanthous/Entities/Character.hs
@@ -14,30 +14,6 @@ module Xanthous.Entities.Character
   , speed
   , body
 
-    -- ** Inventory
-  , Inventory(..)
-  , backpack
-  , wielded
-  , items
-  , InventoryPosition(..)
-  , describeInventoryPosition
-  , inventoryPosition
-  , itemsWithPosition
-  , removeItemFromPosition
-    -- *** Wielded items
-  , Wielded(..)
-  , hands
-  , leftHand
-  , rightHand
-  , inLeftHand
-  , inRightHand
-  , doubleHanded
-  , wieldedItems
-  , WieldedItem(..)
-  , wieldedItem
-  , wieldableItem
-  , asWieldedItem
-
     -- *** Body
   , Body(..)
   , initialBody
@@ -72,214 +48,14 @@ import           Control.Monad.Trans.State.Lazy (execStateT)
 import           Xanthous.Util.QuickCheck
 import           Xanthous.Game.State
 import           Xanthous.Entities.Item
+import           Xanthous.Entities.Common
 import           Xanthous.Data
-                 ( TicksPerTile, Hitpoints, Per, Ticks, (|*|), positioned
-                 , Positioned(..)
-                 )
-import           Xanthous.Entities.RawTypes (WieldableItem, wieldable)
+                 ( TicksPerTile, Hitpoints, Per, Ticks, (|*|), positioned )
 import qualified Xanthous.Entities.RawTypes as Raw
-import           Xanthous.Util (EqEqProp(EqEqProp), modifyKL, removeFirst)
+import           Xanthous.Util (EqEqProp(EqEqProp), modifyKL)
 import           Xanthous.Monad (say_)
 --------------------------------------------------------------------------------
 
-data WieldedItem = WieldedItem
-  { _wieldedItem :: Item
-  , _wieldableItem :: WieldableItem
-    -- ^ Invariant: item ^. itemType . wieldable ≡ Just wieldableItem
-  }
-  deriving stock (Eq, Show, Ord, Generic)
-  deriving anyclass (NFData, CoArbitrary, Function)
-  deriving (ToJSON, FromJSON)
-       via WithOptions '[ FieldLabelModifier '[Drop 1] ]
-           WieldedItem
-makeFieldsNoPrefix ''WieldedItem
-
-asWieldedItem :: Prism' Item WieldedItem
-asWieldedItem = prism' hither yon
- where
-   yon item = WieldedItem item <$> item ^. itemType . wieldable
-   hither (WieldedItem item _) = item
-
-instance Brain WieldedItem where
-  step ticks (Positioned p wi) =
-    over positioned (\i -> WieldedItem i $ wi ^. wieldableItem)
-    <$> step ticks (Positioned p $ wi ^. wieldedItem)
-
-instance Draw WieldedItem where
-  draw = draw . view wieldedItem
-
-instance Entity WieldedItem where
-  entityAttributes = entityAttributes . view wieldedItem
-  description = description . view wieldedItem
-  entityChar = entityChar . view wieldedItem
-
-instance Arbitrary WieldedItem where
-  arbitrary = genericArbitrary <&> \wi ->
-    wi & wieldedItem . itemType . wieldable ?~ wi ^. wieldableItem
-
-data Wielded
-  = DoubleHanded WieldedItem
-  | Hands { _leftHand :: !(Maybe WieldedItem)
-          , _rightHand :: !(Maybe WieldedItem)
-          }
-  deriving stock (Eq, Show, Ord, Generic)
-  deriving anyclass (NFData, CoArbitrary, Function)
-  deriving Arbitrary via GenericArbitrary Wielded
-  deriving (ToJSON, FromJSON)
-       via WithOptions '[ 'SumEnc 'ObjWithSingleField ]
-           Wielded
-
-nothingWielded :: Wielded
-nothingWielded = Hands Nothing Nothing
-
-hands :: Prism' Wielded (Maybe WieldedItem, Maybe WieldedItem)
-hands = prism' (uncurry Hands) $ \case
-  Hands l r -> Just (l, r)
-  _ -> Nothing
-
-leftHand :: Traversal' Wielded (Maybe WieldedItem)
-leftHand = hands . _1
-
-inLeftHand :: WieldedItem -> Wielded
-inLeftHand wi = Hands (Just wi) Nothing
-
-rightHand :: Traversal' Wielded (Maybe WieldedItem)
-rightHand = hands . _2
-
-inRightHand :: WieldedItem -> Wielded
-inRightHand wi = Hands Nothing (Just wi)
-
-doubleHanded :: Prism' Wielded WieldedItem
-doubleHanded = prism' DoubleHanded $ \case
-  DoubleHanded i -> Just i
-  _ -> Nothing
-
-wieldedItems :: Traversal' Wielded WieldedItem
-wieldedItems k (DoubleHanded wielded) = DoubleHanded <$> k wielded
-wieldedItems k (Hands l r) = Hands <$> _Just k l <*> _Just k r
-
-data Inventory = Inventory
-  { _backpack :: Vector Item
-  , _wielded :: Wielded
-  }
-  deriving stock (Eq, Show, Ord, Generic)
-  deriving anyclass (NFData, CoArbitrary, Function)
-  deriving Arbitrary via GenericArbitrary Inventory
-  deriving (ToJSON, FromJSON)
-       via WithOptions '[ FieldLabelModifier '[Drop 1] ]
-           Inventory
-makeFieldsNoPrefix ''Inventory
-
-items :: Traversal' Inventory Item
-items k (Inventory bp w) = Inventory
-  <$> traversed k bp
-  <*> (wieldedItems . wieldedItem) k w
-
-type instance Element Inventory = Item
-
-instance MonoFunctor Inventory where
-  omap = over items
-
-instance MonoFoldable Inventory where
-  ofoldMap = foldMapOf items
-  ofoldr = foldrOf items
-  ofoldl' = foldlOf' items
-  otoList = toListOf items
-  oall = allOf items
-  oany = anyOf items
-  onull = nullOf items
-  ofoldr1Ex = foldr1Of items
-  ofoldl1Ex' = foldl1Of' items
-  headEx = headEx . toListOf items
-  lastEx = lastEx . toListOf items
-
-instance MonoTraversable Inventory where
-  otraverse = traverseOf items
-
-instance Semigroup Inventory where
-  inv₁ <> inv₂ =
-    let backpack' = inv₁ ^. backpack <> inv₂ ^. backpack
-        (wielded', backpack'') = case (inv₁ ^. wielded, inv₂ ^. wielded) of
-          (wielded₁, wielded₂@(DoubleHanded _)) ->
-            (wielded₂, backpack' <> fromList (wielded₁ ^.. wieldedItems . wieldedItem))
-          (wielded₁, wielded₂@(Hands (Just _) (Just _))) ->
-            (wielded₂, backpack' <> fromList (wielded₁ ^.. wieldedItems . wieldedItem))
-          (wielded₁, Hands Nothing Nothing) -> (wielded₁, backpack')
-          (Hands Nothing Nothing, wielded₂) -> (wielded₂, backpack')
-          (Hands (Just l₁) Nothing, Hands Nothing (Just r₂)) ->
-            (Hands (Just l₁) (Just r₂), backpack')
-          (wielded₁@(DoubleHanded _), wielded₂) ->
-            (wielded₁, backpack' <> fromList (wielded₂ ^.. wieldedItems . wieldedItem))
-          (Hands Nothing (Just r₁), Hands Nothing (Just r₂)) ->
-            (Hands Nothing (Just r₂), r₁ ^. wieldedItem <| backpack')
-          (Hands Nothing r₁, Hands (Just l₂) Nothing) ->
-            (Hands (Just l₂) r₁, backpack')
-          (Hands (Just l₁) Nothing, Hands (Just l₂) Nothing) ->
-            (Hands (Just l₂) Nothing, l₁ ^. wieldedItem <| backpack')
-          (Hands (Just l₁) (Just r₁), Hands Nothing (Just r₂)) ->
-            (Hands (Just l₁) (Just r₂), r₁ ^. wieldedItem <| backpack')
-          (Hands (Just l₁) (Just r₁), Hands (Just l₂) Nothing) ->
-            (Hands (Just l₂) (Just r₁), l₁ ^. wieldedItem <| backpack')
-    in Inventory backpack'' wielded'
-
-instance Monoid Inventory where
-  mempty = Inventory mempty $ Hands Nothing Nothing
-
--- | Representation for where in the inventory an item might be
-data InventoryPosition
-  = Backpack
-  | LeftHand
-  | RightHand
-  | BothHands
-  deriving stock (Eq, Show, Ord, Generic)
-  deriving anyclass (NFData, CoArbitrary, Function)
-  deriving Arbitrary via GenericArbitrary InventoryPosition
-
--- | Return a human-readable description of the given 'InventoryPosition'
-describeInventoryPosition :: InventoryPosition -> Text
-describeInventoryPosition Backpack  = "In backpack"
-describeInventoryPosition LeftHand  = "Wielded, in left hand"
-describeInventoryPosition RightHand = "Wielded, in right hand"
-describeInventoryPosition BothHands = "Wielded, in both hands"
-
--- | Given a position in the inventory, return a traversal on the inventory over
--- all the items in that position
-inventoryPosition :: InventoryPosition -> Traversal' Inventory Item
-inventoryPosition Backpack = backpack . traversed
-inventoryPosition LeftHand = wielded . leftHand . _Just . wieldedItem
-inventoryPosition RightHand = wielded . leftHand . _Just . wieldedItem
-inventoryPosition BothHands = wielded . doubleHanded . wieldedItem
-
--- | A fold over all the items in the inventory accompanied by their position in
--- the inventory
---
--- Invariant: This will return items in the same order as 'items'
-itemsWithPosition :: Fold Inventory (InventoryPosition, Item)
-itemsWithPosition = folding $ (<>) <$> backpackItems <*> handItems
-  where
-    backpackItems = toListOf $ backpack . folded . to (Backpack ,)
-    handItems inventory = case inventory ^. wielded of
-       DoubleHanded i -> pure (BothHands, i ^. wieldedItem)
-       Hands l r -> (l ^.. folded . wieldedItem . to (LeftHand ,))
-                 <> (r ^.. folded . wieldedItem . to (RightHand ,))
-
--- | Remove the first item equal to 'Item' from the given position in the
--- inventory
-removeItemFromPosition :: InventoryPosition -> Item -> Inventory -> Inventory
-removeItemFromPosition Backpack item inv
-  = inv & backpack %~ removeFirst (== item)
-removeItemFromPosition LeftHand item inv
-  = inv & wielded . leftHand %~ filter ((/= item) . view wieldedItem)
-removeItemFromPosition RightHand item inv
-  = inv & wielded . rightHand %~ filter ((/= item) . view wieldedItem)
-removeItemFromPosition BothHands item inv
-  | has (wielded . doubleHanded . wieldedItem . filtered (== item)) inv
-  = inv & wielded .~ nothingWielded
-  | otherwise
-  = inv
-
---------------------------------------------------------------------------------
-
 -- | The status of the character's knuckles
 --
 -- This struct is used to track the damage and then eventual build-up of
diff --git a/users/grfn/xanthous/src/Xanthous/Entities/Common.hs b/users/grfn/xanthous/src/Xanthous/Entities/Common.hs
new file mode 100644
index 000000000000..1444f3ce1639
--- /dev/null
+++ b/users/grfn/xanthous/src/Xanthous/Entities/Common.hs
@@ -0,0 +1,245 @@
+{-# LANGUAGE TemplateHaskell #-}
+--------------------------------------------------------------------------------
+-- |
+-- Module      : Xanthous.Entities.Common
+-- Description : Common data type definitions and utilities for entities
+--
+--------------------------------------------------------------------------------
+module Xanthous.Entities.Common
+  ( -- * Inventory
+    Inventory(..)
+  , backpack
+  , wielded
+  , items
+  , InventoryPosition(..)
+  , describeInventoryPosition
+  , inventoryPosition
+  , itemsWithPosition
+  , removeItemFromPosition
+
+    -- ** Wielded items
+  , Wielded(..)
+  , hands
+  , leftHand
+  , rightHand
+  , inLeftHand
+  , inRightHand
+  , doubleHanded
+  , wieldedItems
+  , WieldedItem(..)
+  , wieldedItem
+  , wieldableItem
+  , asWieldedItem
+  ) where
+--------------------------------------------------------------------------------
+import           Xanthous.Prelude
+--------------------------------------------------------------------------------
+import           Data.Aeson (ToJSON, FromJSON)
+import           Data.Aeson.Generic.DerivingVia
+import           Test.QuickCheck
+import           Test.QuickCheck.Checkers (EqProp)
+--------------------------------------------------------------------------------
+import           Xanthous.Data (Positioned(..), positioned)
+import           Xanthous.Util.QuickCheck
+import           Xanthous.Game.State
+import           Xanthous.Entities.Item
+import           Xanthous.Entities.RawTypes (WieldableItem, wieldable)
+import           Xanthous.Util (removeFirst, EqEqProp(..))
+--------------------------------------------------------------------------------
+
+data WieldedItem = WieldedItem
+  { _wieldedItem :: Item
+  , _wieldableItem :: WieldableItem
+    -- ^ Invariant: item ^. itemType . wieldable ≡ Just wieldableItem
+  }
+  deriving stock (Eq, Show, Ord, Generic)
+  deriving anyclass (NFData, CoArbitrary, Function)
+  deriving (ToJSON, FromJSON)
+       via WithOptions '[ FieldLabelModifier '[Drop 1] ]
+           WieldedItem
+makeFieldsNoPrefix ''WieldedItem
+
+asWieldedItem :: Prism' Item WieldedItem
+asWieldedItem = prism' hither yon
+ where
+   yon item = WieldedItem item <$> item ^. itemType . wieldable
+   hither (WieldedItem item _) = item
+
+instance Brain WieldedItem where
+  step ticks (Positioned p wi) =
+    over positioned (\i -> WieldedItem i $ wi ^. wieldableItem)
+    <$> step ticks (Positioned p $ wi ^. wieldedItem)
+
+instance Draw WieldedItem where
+  draw = draw . view wieldedItem
+
+instance Entity WieldedItem where
+  entityAttributes = entityAttributes . view wieldedItem
+  description = description . view wieldedItem
+  entityChar = entityChar . view wieldedItem
+
+instance Arbitrary WieldedItem where
+  arbitrary = genericArbitrary <&> \wi ->
+    wi & wieldedItem . itemType . wieldable ?~ wi ^. wieldableItem
+
+data Wielded
+  = DoubleHanded WieldedItem
+  | Hands { _leftHand :: !(Maybe WieldedItem)
+          , _rightHand :: !(Maybe WieldedItem)
+          }
+  deriving stock (Eq, Show, Ord, Generic)
+  deriving anyclass (NFData, CoArbitrary, Function)
+  deriving Arbitrary via GenericArbitrary Wielded
+  deriving (ToJSON, FromJSON)
+       via WithOptions '[ 'SumEnc 'ObjWithSingleField ]
+           Wielded
+
+nothingWielded :: Wielded
+nothingWielded = Hands Nothing Nothing
+
+hands :: Prism' Wielded (Maybe WieldedItem, Maybe WieldedItem)
+hands = prism' (uncurry Hands) $ \case
+  Hands l r -> Just (l, r)
+  _ -> Nothing
+
+leftHand :: Traversal' Wielded (Maybe WieldedItem)
+leftHand = hands . _1
+
+inLeftHand :: WieldedItem -> Wielded
+inLeftHand wi = Hands (Just wi) Nothing
+
+rightHand :: Traversal' Wielded (Maybe WieldedItem)
+rightHand = hands . _2
+
+inRightHand :: WieldedItem -> Wielded
+inRightHand wi = Hands Nothing (Just wi)
+
+doubleHanded :: Prism' Wielded WieldedItem
+doubleHanded = prism' DoubleHanded $ \case
+  DoubleHanded i -> Just i
+  _ -> Nothing
+
+wieldedItems :: Traversal' Wielded WieldedItem
+wieldedItems k (DoubleHanded wielded) = DoubleHanded <$> k wielded
+wieldedItems k (Hands l r) = Hands <$> _Just k l <*> _Just k r
+
+data Inventory = Inventory
+  { _backpack :: Vector Item
+  , _wielded :: Wielded
+  }
+  deriving stock (Eq, Show, Ord, Generic)
+  deriving anyclass (NFData, CoArbitrary, Function)
+  deriving Arbitrary via GenericArbitrary Inventory
+  deriving EqProp via EqEqProp Inventory
+  deriving (ToJSON, FromJSON)
+       via WithOptions '[ FieldLabelModifier '[Drop 1] ]
+           Inventory
+makeFieldsNoPrefix ''Inventory
+
+items :: Traversal' Inventory Item
+items k (Inventory bp w) = Inventory
+  <$> traversed k bp
+  <*> (wieldedItems . wieldedItem) k w
+
+type instance Element Inventory = Item
+
+instance MonoFunctor Inventory where
+  omap = over items
+
+instance MonoFoldable Inventory where
+  ofoldMap = foldMapOf items
+  ofoldr = foldrOf items
+  ofoldl' = foldlOf' items
+  otoList = toListOf items
+  oall = allOf items
+  oany = anyOf items
+  onull = nullOf items
+  ofoldr1Ex = foldr1Of items
+  ofoldl1Ex' = foldl1Of' items
+  headEx = headEx . toListOf items
+  lastEx = lastEx . toListOf items
+
+instance MonoTraversable Inventory where
+  otraverse = traverseOf items
+
+instance Semigroup Inventory where
+  inv₁ <> inv₂ =
+    let backpack' = inv₁ ^. backpack <> inv₂ ^. backpack
+        (wielded', backpack'') = case (inv₁ ^. wielded, inv₂ ^. wielded) of
+          (wielded₁, wielded₂@(DoubleHanded _)) ->
+            (wielded₂, backpack' <> fromList (wielded₁ ^.. wieldedItems . wieldedItem))
+          (wielded₁, wielded₂@(Hands (Just _) (Just _))) ->
+            (wielded₂, backpack' <> fromList (wielded₁ ^.. wieldedItems . wieldedItem))
+          (wielded₁, Hands Nothing Nothing) -> (wielded₁, backpack')
+          (Hands Nothing Nothing, wielded₂) -> (wielded₂, backpack')
+          (Hands (Just l₁) Nothing, Hands Nothing (Just r₂)) ->
+            (Hands (Just l₁) (Just r₂), backpack')
+          (wielded₁@(DoubleHanded _), wielded₂) ->
+            (wielded₁, backpack' <> fromList (wielded₂ ^.. wieldedItems . wieldedItem))
+          (Hands Nothing (Just r₁), Hands Nothing (Just r₂)) ->
+            (Hands Nothing (Just r₂), r₁ ^. wieldedItem <| backpack')
+          (Hands Nothing r₁, Hands (Just l₂) Nothing) ->
+            (Hands (Just l₂) r₁, backpack')
+          (Hands (Just l₁) Nothing, Hands (Just l₂) Nothing) ->
+            (Hands (Just l₂) Nothing, l₁ ^. wieldedItem <| backpack')
+          (Hands (Just l₁) (Just r₁), Hands Nothing (Just r₂)) ->
+            (Hands (Just l₁) (Just r₂), r₁ ^. wieldedItem <| backpack')
+          (Hands (Just l₁) (Just r₁), Hands (Just l₂) Nothing) ->
+            (Hands (Just l₂) (Just r₁), l₁ ^. wieldedItem <| backpack')
+    in Inventory backpack'' wielded'
+
+instance Monoid Inventory where
+  mempty = Inventory mempty $ Hands Nothing Nothing
+
+-- | Representation for where in the inventory an item might be
+data InventoryPosition
+  = Backpack
+  | LeftHand
+  | RightHand
+  | BothHands
+  deriving stock (Eq, Show, Ord, Generic)
+  deriving anyclass (NFData, CoArbitrary, Function)
+  deriving Arbitrary via GenericArbitrary InventoryPosition
+
+-- | Return a human-readable description of the given 'InventoryPosition'
+describeInventoryPosition :: InventoryPosition -> Text
+describeInventoryPosition Backpack  = "In backpack"
+describeInventoryPosition LeftHand  = "Wielded, in left hand"
+describeInventoryPosition RightHand = "Wielded, in right hand"
+describeInventoryPosition BothHands = "Wielded, in both hands"
+
+-- | Given a position in the inventory, return a traversal on the inventory over
+-- all the items in that position
+inventoryPosition :: InventoryPosition -> Traversal' Inventory Item
+inventoryPosition Backpack = backpack . traversed
+inventoryPosition LeftHand = wielded . leftHand . _Just . wieldedItem
+inventoryPosition RightHand = wielded . leftHand . _Just . wieldedItem
+inventoryPosition BothHands = wielded . doubleHanded . wieldedItem
+
+-- | A fold over all the items in the inventory accompanied by their position in
+-- the inventory
+--
+-- Invariant: This will return items in the same order as 'items'
+itemsWithPosition :: Fold Inventory (InventoryPosition, Item)
+itemsWithPosition = folding $ (<>) <$> backpackItems <*> handItems
+  where
+    backpackItems = toListOf $ backpack . folded . to (Backpack ,)
+    handItems inventory = case inventory ^. wielded of
+       DoubleHanded i -> pure (BothHands, i ^. wieldedItem)
+       Hands l r -> (l ^.. folded . wieldedItem . to (LeftHand ,))
+                 <> (r ^.. folded . wieldedItem . to (RightHand ,))
+
+-- | Remove the first item equal to 'Item' from the given position in the
+-- inventory
+removeItemFromPosition :: InventoryPosition -> Item -> Inventory -> Inventory
+removeItemFromPosition Backpack item inv
+  = inv & backpack %~ removeFirst (== item)
+removeItemFromPosition LeftHand item inv
+  = inv & wielded . leftHand %~ filter ((/= item) . view wieldedItem)
+removeItemFromPosition RightHand item inv
+  = inv & wielded . rightHand %~ filter ((/= item) . view wieldedItem)
+removeItemFromPosition BothHands item inv
+  | has (wielded . doubleHanded . wieldedItem . filtered (== item)) inv
+  = inv & wielded .~ nothingWielded
+  | otherwise
+  = inv
diff --git a/users/grfn/xanthous/src/Xanthous/Game/Draw.hs b/users/grfn/xanthous/src/Xanthous/Game/Draw.hs
index 5b51ca67292b..53ea1c96f8af 100644
--- a/users/grfn/xanthous/src/Xanthous/Game/Draw.hs
+++ b/users/grfn/xanthous/src/Xanthous/Game/Draw.hs
@@ -17,6 +17,7 @@ import           Xanthous.Data.App (ResourceName, Panel(..))
 import qualified Xanthous.Data.App as Resource
 import qualified Xanthous.Data.EntityMap as EntityMap
 import           Xanthous.Game.State
+import           Xanthous.Entities.Common (Wielded(..), wielded, backpack)
 import           Xanthous.Entities.Character
 import           Xanthous.Entities.Item (Item)
 import           Xanthous.Game
diff --git a/users/grfn/xanthous/test/Spec.hs b/users/grfn/xanthous/test/Spec.hs
index 80826053866a..64c10cf21e20 100644
--- a/users/grfn/xanthous/test/Spec.hs
+++ b/users/grfn/xanthous/test/Spec.hs
@@ -9,6 +9,7 @@ import qualified Xanthous.Data.LevelsSpec
 import qualified Xanthous.Data.MemoSpec
 import qualified Xanthous.Data.NestedMapSpec
 import qualified Xanthous.DataSpec
+import qualified Xanthous.Entities.CommonSpec
 import qualified Xanthous.Entities.RawsSpec
 import qualified Xanthous.Entities.RawTypesSpec
 import qualified Xanthous.Entities.CharacterSpec
@@ -38,6 +39,7 @@ test = testGroup "Xanthous"
   , Xanthous.Data.MemoSpec.test
   , Xanthous.Data.NestedMapSpec.test
   , Xanthous.DataSpec.test
+  , Xanthous.Entities.CommonSpec.test
   , Xanthous.Entities.RawsSpec.test
   , Xanthous.Entities.CharacterSpec.test
   , Xanthous.Entities.RawTypesSpec.test
diff --git a/users/grfn/xanthous/test/Xanthous/Entities/CharacterSpec.hs b/users/grfn/xanthous/test/Xanthous/Entities/CharacterSpec.hs
index 9210355d2dbb..734cce1efbbe 100644
--- a/users/grfn/xanthous/test/Xanthous/Entities/CharacterSpec.hs
+++ b/users/grfn/xanthous/test/Xanthous/Entities/CharacterSpec.hs
@@ -3,7 +3,6 @@
 module Xanthous.Entities.CharacterSpec (main, test) where
 --------------------------------------------------------------------------------
 import           Test.Prelude
-import           Data.Vector.Lens (toVectorOf)
 --------------------------------------------------------------------------------
 import           Xanthous.Entities.Character
 import           Xanthous.Util (endoTimes)
@@ -22,21 +21,4 @@ test = testGroup "Xanthous.Entities.CharacterSpec"
           in _knuckleDamage knuckles' @?= 5
       ]
     ]
-  , testGroup "Inventory"
-    [ testProperty "items === itemsWithPosition . _2" $ \inv ->
-        inv ^.. items === inv ^.. itemsWithPosition . _2
-    , testGroup "removeItemFromPosition" $
-      let rewield w inv =
-            let (old, inv') = inv & wielded <<.~ w
-            in inv' & backpack <>~ toVectorOf (wieldedItems . wieldedItem) old
-      in [ (Backpack, \item -> backpack %~ (item ^. wieldedItem <|))
-         , (LeftHand, rewield . inLeftHand)
-         , (RightHand, rewield . inRightHand)
-         , (BothHands, rewield . review doubleHanded)
-         ] <&> \(pos, addItem) ->
-           testProperty (show pos) $ \inv item ->
-             let inv' = addItem item inv
-                 inv'' = removeItemFromPosition pos (item ^. wieldedItem) inv'
-             in inv'' ^.. items === inv ^.. items
-    ]
   ]
diff --git a/users/grfn/xanthous/test/Xanthous/Entities/CommonSpec.hs b/users/grfn/xanthous/test/Xanthous/Entities/CommonSpec.hs
new file mode 100644
index 000000000000..ba27e3cbca4e
--- /dev/null
+++ b/users/grfn/xanthous/test/Xanthous/Entities/CommonSpec.hs
@@ -0,0 +1,32 @@
+--------------------------------------------------------------------------------
+module Xanthous.Entities.CommonSpec (main, test) where
+--------------------------------------------------------------------------------
+import           Test.Prelude
+import           Data.Vector.Lens (toVectorOf)
+--------------------------------------------------------------------------------
+import           Xanthous.Entities.Common
+--------------------------------------------------------------------------------
+
+main :: IO ()
+main = defaultMain test
+
+test :: TestTree
+test = testGroup "Xanthous.Entities.CommonSpec"
+  [ testGroup "Inventory"
+    [ testProperty "items === itemsWithPosition . _2" $ \inv ->
+        inv ^.. items === inv ^.. itemsWithPosition . _2
+    , testGroup "removeItemFromPosition" $
+      let rewield w inv =
+            let (old, inv') = inv & wielded <<.~ w
+            in inv' & backpack <>~ toVectorOf (wieldedItems . wieldedItem) old
+      in [ (Backpack, \item -> backpack %~ (item ^. wieldedItem <|))
+         , (LeftHand, rewield . inLeftHand)
+         , (RightHand, rewield . inRightHand)
+         , (BothHands, rewield . review doubleHanded)
+         ] <&> \(pos, addItem) ->
+           testProperty (show pos) $ \inv item ->
+             let inv' = addItem item inv
+                 inv'' = removeItemFromPosition pos (item ^. wieldedItem) inv'
+             in inv'' ^.. items === inv ^.. items
+    ]
+  ]
diff --git a/users/grfn/xanthous/xanthous.cabal b/users/grfn/xanthous/xanthous.cabal
index e23f3968ee44..987e1f48f693 100644
--- a/users/grfn/xanthous/xanthous.cabal
+++ b/users/grfn/xanthous/xanthous.cabal
@@ -1,10 +1,10 @@
 cabal-version: 1.12
 
--- This file has been generated from package.yaml by hpack version 0.34.4.
+-- This file has been generated from package.yaml by hpack version 0.34.5.
 --
 -- see: https://github.com/sol/hpack
 --
--- hash: 96c5446afd429c3e2166158e317c18a69be9bad8ce76de85f69abda4f9aa162c
+-- hash: 8cae8550487b6092c18c82a0dc29bf22980d416771c66f6fca3e151875c66495
 
 name:           xanthous
 version:        0.1.0.0
@@ -47,6 +47,7 @@ library
       Xanthous.Data.NestedMap
       Xanthous.Data.VectorBag
       Xanthous.Entities.Character
+      Xanthous.Entities.Common
       Xanthous.Entities.Creature
       Xanthous.Entities.Creature.Hippocampus
       Xanthous.Entities.Draw.Util
@@ -301,6 +302,7 @@ test-suite test
       Xanthous.Data.NestedMapSpec
       Xanthous.DataSpec
       Xanthous.Entities.CharacterSpec
+      Xanthous.Entities.CommonSpec
       Xanthous.Entities.RawsSpec
       Xanthous.Entities.RawTypesSpec
       Xanthous.Game.PromptSpec