1 files changed, 61 insertions, 0 deletions
diff --git a/src/Script/Expr/Class.hs b/src/Script/Expr/Class.hs
new file mode 100644
index 0000000..590b99c
--- /dev/null
+++ b/src/Script/Expr/Class.hs
@@ -0,0 +1,61 @@
+module Script.Expr.Class (
+    ExprType(..),
+    RecordSelector(..),
+    ExprListUnpacker(..),
+    ExprEnumerator(..),
+) where
+
+import Data.Scientific
+import Data.Text (Text)
+import Data.Text qualified as T
+import Data.Typeable
+import Data.Void
+
+class Typeable a => ExprType a where
+    textExprType :: proxy a -> Text
+    textExprValue :: a -> Text
+
+    recordMembers :: [(Text, RecordSelector a)]
+    recordMembers = []
+
+    exprListUnpacker :: proxy a -> Maybe (ExprListUnpacker a)
+    exprListUnpacker _ = Nothing
+
+    exprEnumerator :: proxy a -> Maybe (ExprEnumerator a)
+    exprEnumerator _ = Nothing
+
+instance ExprType Integer where
+    textExprType _ = T.pack "integer"
+    textExprValue x = T.pack (show x)
+
+    exprEnumerator _ = Just $ ExprEnumerator enumFromTo enumFromThenTo
+
+instance ExprType Scientific where
+    textExprType _ = T.pack "number"
+    textExprValue x = T.pack (show x)
+
+instance ExprType Bool where
+    textExprType _ = T.pack "bool"
+    textExprValue True = T.pack "true"
+    textExprValue False = T.pack "false"
+
+instance ExprType Text where
+    textExprType _ = T.pack "string"
+    textExprValue x = T.pack (show x)
+
+instance ExprType Void where
+    textExprType _ = T.pack "void"
+    textExprValue _ = T.pack "<void>"
+
+instance ExprType a => ExprType [a] where
+    textExprType _ = "[" <> textExprType @a Proxy <> "]"
+    textExprValue x = "[" <> T.intercalate ", " (map textExprValue x) <> "]"
+
+    exprListUnpacker _ = Just $ ExprListUnpacker id (const Proxy)
+
+
+data RecordSelector a = forall b. ExprType b => RecordSelector (a -> b)
+
+data ExprListUnpacker a = forall e. ExprType e => ExprListUnpacker (a -> [e]) (Proxy a -> Proxy e)
+
+data ExprEnumerator a = ExprEnumerator (a -> a -> [a]) (a -> a -> a -> [a])