feat(xanthous): Track the volume and density of item types r/2678

Allow the itemType raw to have density and volume fields, both of which
represent *intervals* of both density and volume (because both can
hypothetically vary a bit). The idea here is that when we're making
an *instance* of one of these items, we pick a random value in the
range.

Lots of stuff in this commit is datatype and typeclass instances to
support things like intervals being fields on datatypes that get
serialized to saved games - including a manual definition of Ord for
Item since Ord isn't well-defined for intervals

Change-Id: Ia088f2f75cdce9d00560297e5c269e3310b85bc3
Reviewed-on: https://cl.tvl.fyi/c/depot/+/3225
Reviewed-by: grfn <grfn@gws.fyi>
Tested-by: BuildkiteCI

1 files changed, 21 insertions, 8 deletions

diff --git a/users/grfn/xanthous/test/Test/Prelude.hs b/users/grfn/xanthous/test/Test/Prelude.hs
index c423796184f7..2df0a6290a02 100644
--- a/users/grfn/xanthous/test/Test/Prelude.hs
+++ b/users/grfn/xanthous/test/Test/Prelude.hs
@@ -1,3 +1,5 @@
+{-# LANGUAGE AllowAmbiguousTypes #-}
+--------------------------------------------------------------------------------
 module Test.Prelude
   ( module Xanthous.Prelude
   , module Test.Tasty
@@ -5,15 +7,26 @@ module Test.Prelude
   , module Test.Tasty.QuickCheck
   , module Test.QuickCheck.Classes
   , testBatch
+  , jsonRoundTrip
   ) where
-
-import Xanthous.Prelude hiding (assert, elements)
-import Test.Tasty
-import Test.Tasty.QuickCheck
-import Test.Tasty.HUnit
-import Test.QuickCheck.Classes
-import Test.QuickCheck.Checkers (TestBatch)
-import Test.QuickCheck.Instances.ByteString ()
+--------------------------------------------------------------------------------
+import           Xanthous.Prelude hiding (assert, elements)
+--------------------------------------------------------------------------------
+import           Test.Tasty
+import           Test.Tasty.QuickCheck
+import           Test.Tasty.HUnit
+import           Test.QuickCheck.Classes
+import           Test.QuickCheck.Checkers (TestBatch, EqProp ((=-=)))
+import           Test.QuickCheck.Instances.ByteString ()
+--------------------------------------------------------------------------------
+import qualified Data.Aeson as JSON
+import           Data.Aeson (ToJSON, FromJSON)
+--------------------------------------------------------------------------------
 
 testBatch :: TestBatch -> TestTree
 testBatch (name, tests) = testGroup name $ uncurry testProperty <$> tests
+
+jsonRoundTrip
+  :: forall a. (ToJSON a, FromJSON a, EqProp a, Arbitrary a, Show a) => TestTree
+jsonRoundTrip = testProperty "JSON round trip" $ \(x :: a) ->
+  JSON.decode (JSON.encode x) =-= Just x