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+{-# LANGUAGE TemplateHaskell #-}
+{-# LANGUAGE StandaloneDeriving #-}
+{-# LANGUAGE RecordWildCards #-}
+--------------------------------------------------------------------------------
+module Xanthous.Entities.Item
+  ( Item(..)
+  , itemType
+  , density
+  , volume
+  , newWithType
+  , isEdible
+  , weight
+  , fullDescription
+  ) where
+--------------------------------------------------------------------------------
+import           Xanthous.Prelude
+import           Test.QuickCheck (Arbitrary, CoArbitrary, Function)
+import           Data.Aeson (ToJSON, FromJSON)
+import           Data.Aeson.Generic.DerivingVia
+import           Control.Monad.Random (MonadRandom)
+--------------------------------------------------------------------------------
+import           Xanthous.Entities.RawTypes (ItemType)
+import qualified Xanthous.Entities.RawTypes as Raw
+import           Xanthous.Game.State
+import           Xanthous.Data (Grams, Per, Cubic, Meters, (|*|))
+import           Xanthous.Util.QuickCheck (GenericArbitrary(GenericArbitrary))
+import           Xanthous.Random (choose, FiniteInterval(..))
+--------------------------------------------------------------------------------
+
+data Item = Item
+  { _itemType :: ItemType
+  , _density  :: Grams `Per` Cubic Meters
+  , _volume   :: Cubic Meters
+  }
+  deriving stock (Eq, Show, Ord, Generic)
+  deriving anyclass (NFData, CoArbitrary, Function)
+  deriving Draw via DrawRawChar "_itemType" Item
+  deriving Arbitrary via GenericArbitrary Item
+  deriving (ToJSON, FromJSON)
+       via WithOptions '[ FieldLabelModifier '[Drop 1] ]
+                       Item
+makeLenses ''Item
+
+-- deriving via (Brainless Item) instance Brain Item
+instance Brain Item where step = brainVia Brainless
+
+instance Entity Item where
+  description = view $ itemType . Raw.description
+  entityChar = view $ itemType . Raw.char
+  entityCollision = const Nothing
+
+newWithType :: MonadRandom m => ItemType -> m Item
+newWithType _itemType = do
+  _density <- choose . FiniteInterval $ _itemType ^. Raw.density
+  _volume  <- choose . FiniteInterval $ _itemType ^. Raw.volume
+  pure Item {..}
+
+isEdible :: Item -> Bool
+isEdible = Raw.isEdible . view itemType
+
+-- | The weight of this item, calculated by multiplying its volume by the
+-- density of its material
+weight :: Item -> Grams
+weight item = (item ^. density) |*| (item ^. volume)
+
+-- | Describe the item in full detail
+fullDescription :: Item -> Text
+fullDescription item = unlines
+  [ item ^. itemType . Raw.description
+  , ""
+  , item ^. itemType . Raw.longDescription
+  , ""
+  , "volume: " <> tshow (item ^. volume)
+  , "density: " <> tshow (item ^. density)
+  , "weight: " <> tshow (weight item)
+  ]