fix(xanthous): Only use alphabetic chars for menu items r/2682

Previously, we were using `smallestNotIn` for selecting new characters
for menu items with duplicate chatacters - this uses the 'Bounded'
instance for the type, which for Char meant the first character we would
always select was \NUL - making it look like the menu item had no
character, and making it impossible to actually select the menu item.
This introduces an AlphaChar newtype, which is a wrapper around Char
whose Bounded and Enum instances only use alphabetic characters (a-ZA-Z)
and uses that for menu characters instead.

Change-Id: If34ed9e9ce84f2bcb1cb87432cc6273f40b69f72
Reviewed-on: https://cl.tvl.fyi/c/depot/+/3229
Reviewed-by: grfn <grfn@gws.fyi>
Tested-by: BuildkiteCI

6 files changed, 63 insertions, 3 deletions

diff --git a/users/grfn/xanthous/src/Xanthous/Game/Prompt.hs b/users/grfn/xanthous/src/Xanthous/Game/Prompt.hs
index 30b5fe7545e0..fa4c3903deb1 100644
--- a/users/grfn/xanthous/src/Xanthous/Game/Prompt.hs
+++ b/users/grfn/xanthous/src/Xanthous/Game/Prompt.hs
@@ -28,7 +28,8 @@ import           Brick.Widgets.Edit (Editor, editorText, getEditContents)
 import           Test.QuickCheck
 import           Test.QuickCheck.Arbitrary.Generic
 --------------------------------------------------------------------------------
-import           Xanthous.Util (smallestNotIn)
+--------------------------------------------------------------------------------
+import           Xanthous.Util (smallestNotIn, AlphaChar (..))
 import           Xanthous.Data (Direction, Position)
 import           Xanthous.Data.App (ResourceName)
 import qualified Xanthous.Data.App as Resource
@@ -175,7 +176,7 @@ mkMenuItems :: (MonoFoldable f, Element f ~ (Char, MenuOption a))
             -> Map Char (MenuOption a)
 mkMenuItems = flip foldl' mempty $ \items (chr, option) ->
   let chr' = if has (ix chr) items
-             then smallestNotIn $ keys items
+             then getAlphaChar . smallestNotIn . map AlphaChar $ keys items
              else chr
   in items & at chr' ?~ option
 
diff --git a/users/grfn/xanthous/src/Xanthous/Util.hs b/users/grfn/xanthous/src/Xanthous/Util.hs
index d3e8cdc30138..2f9606b29c50 100644
--- a/users/grfn/xanthous/src/Xanthous/Util.hs
+++ b/users/grfn/xanthous/src/Xanthous/Util.hs
@@ -38,6 +38,9 @@ module Xanthous.Util
 
     -- * Type-level programming utils
   , KnownBool(..)
+
+    -- *
+  , AlphaChar(..)
   ) where
 --------------------------------------------------------------------------------
 import           Xanthous.Prelude hiding (foldr)
@@ -299,3 +302,34 @@ 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
+
+--------------------------------------------------------------------------------
+
+-- | A newtype wrapper around 'Char' whose 'Enum' and 'Bounded' instances only
+-- include the characters @[a-zA-Z]@
+--
+-- >>> succ (AlphaChar 'z')
+-- 'A'
+newtype AlphaChar = AlphaChar { getAlphaChar :: Char }
+  deriving stock Show
+  deriving (Eq, Ord) via Char
+
+instance Enum AlphaChar where
+  toEnum n
+    | between 0 25 n
+    = AlphaChar . toEnum $ n + fromEnum 'a'
+    | between 26 51 n
+    = AlphaChar . toEnum $ n - 26 + fromEnum 'A'
+    | otherwise
+    = error $ "Tag " <> show n <> " out of range [0, 51] for enum AlphaChar"
+  fromEnum (AlphaChar chr)
+    | between 'a' 'z' chr
+    = fromEnum chr - fromEnum 'a'
+    | between 'A' 'Z' chr
+    = fromEnum chr - fromEnum 'A'
+    | otherwise
+    = error $ "Invalid value for alpha char: " <> show chr
+
+instance Bounded AlphaChar where
+  minBound = AlphaChar 'a'
+  maxBound = AlphaChar 'Z'
diff --git a/users/grfn/xanthous/test/Spec.hs b/users/grfn/xanthous/test/Spec.hs
index 85f49fd07c91..dfecfbdd21c5 100644
--- a/users/grfn/xanthous/test/Spec.hs
+++ b/users/grfn/xanthous/test/Spec.hs
@@ -13,6 +13,7 @@ import qualified Xanthous.Entities.RawsSpec
 import qualified Xanthous.Entities.CharacterSpec
 import qualified Xanthous.GameSpec
 import qualified Xanthous.Game.StateSpec
+import qualified Xanthous.Game.PromptSpec
 import qualified Xanthous.Generators.Level.UtilSpec
 import qualified Xanthous.MessageSpec
 import qualified Xanthous.Messages.TemplateSpec
@@ -40,6 +41,7 @@ test = testGroup "Xanthous"
   , Xanthous.Entities.CharacterSpec.test
   , Xanthous.GameSpec.test
   , Xanthous.Game.StateSpec.test
+  , Xanthous.Game.PromptSpec.test
   , Xanthous.Generators.Level.UtilSpec.test
   , Xanthous.MessageSpec.test
   , Xanthous.Messages.TemplateSpec.test
diff --git a/users/grfn/xanthous/test/Xanthous/Game/PromptSpec.hs b/users/grfn/xanthous/test/Xanthous/Game/PromptSpec.hs
new file mode 100644
index 000000000000..d7a3df4acafa
--- /dev/null
+++ b/users/grfn/xanthous/test/Xanthous/Game/PromptSpec.hs
@@ -0,0 +1,19 @@
+--------------------------------------------------------------------------------
+module Xanthous.Game.PromptSpec (main, test) where
+--------------------------------------------------------------------------------
+import           Test.Prelude
+--------------------------------------------------------------------------------
+import           Xanthous.Game.Prompt
+--------------------------------------------------------------------------------
+
+main :: IO ()
+main = defaultMain test
+
+test :: TestTree
+test = testGroup "Xanthous.Game.PromptSpec"
+  [ testGroup "mkMenuItems"
+    [ testCase "with duplicate items"
+      $ mkMenuItems @[_] [('a', MenuOption @Int "a" 1), ('a', MenuOption "a" 2)]
+        @?= mapFromList [('a', MenuOption "a" 1), ('b', MenuOption "a" 2)]
+    ]
+  ]
diff --git a/users/grfn/xanthous/test/Xanthous/UtilSpec.hs b/users/grfn/xanthous/test/Xanthous/UtilSpec.hs
index 0d6b718bc351..684a03b2c7a0 100644
--- a/users/grfn/xanthous/test/Xanthous/UtilSpec.hs
+++ b/users/grfn/xanthous/test/Xanthous/UtilSpec.hs
@@ -40,4 +40,7 @@ test = testGroup "Xanthous.Util"
     , testProperty "the result is the right length" $ \(xs :: [Int]) p ->
         length (removeFirst p xs) `elem` [length xs, length xs - 1]
     ]
+  , testGroup "AlphaChar"
+    [ testCase "succ 'z'" $ succ (AlphaChar 'z') @?= AlphaChar 'A'
+    ]
   ]
diff --git a/users/grfn/xanthous/xanthous.cabal b/users/grfn/xanthous/xanthous.cabal
index baa09fab3e36..45f85616b6d7 100644
--- a/users/grfn/xanthous/xanthous.cabal
+++ b/users/grfn/xanthous/xanthous.cabal
@@ -4,7 +4,7 @@ cabal-version: 1.12
 --
 -- see: https://github.com/sol/hpack
 --
--- hash: fdfa821ad291b11a2d7a7ee9cc38d7980a9b1f494b77216b141d3424168d621d
+-- hash: 761fd1d1a9f9f9fdf8e14e56922558f7968401c879dcb95ca697dab03d1e9eec
 
 name:           xanthous
 version:        0.1.0.0
@@ -359,6 +359,7 @@ test-suite test
       Xanthous.DataSpec
       Xanthous.Entities.CharacterSpec
       Xanthous.Entities.RawsSpec
+      Xanthous.Game.PromptSpec
       Xanthous.Game.StateSpec
       Xanthous.GameSpec
       Xanthous.Generators.Level.UtilSpec