fix: redundant imports, exposed internals

src/Language/Java/Classfile/Resolvable.hs

@@ -17,7 +17,7 @@ module Language.Java.Classfile.Resolvable (Resolver, Resolvable(..), Stageable(.
 import Data.Kind (Type)
 
 import Language.Java.Classfile.Resolver (Resolver, enterDatatype, enterConstructor, enterField)
-import GHC.Generics (K1 (K1), U1 (U1), (:*:) ((:*:)), (:+:) (..), M1 (M1), Meta(MetaData, MetaCons, MetaSel), Generic, Generically (Generically))
+import GHC.Generics (K1 (K1), U1 (U1), (:*:) ((:*:)), (:+:) (..), M1 (M1), Meta(MetaData, MetaCons, MetaSel), Generic)
 import GHC.TypeLits (symbolVal, KnownSymbol)
 import qualified Data.Text as Text
 import Data.Proxy (Proxy(Proxy))

src/Language/Java/Classfile/Resolver.hs

@@ -3,6 +3,9 @@
 {-# LANGUAGE DeriveFunctor #-}
 {-# LANGUAGE InstanceSigs #-}
 {-# LANGUAGE OverloadedRecordDot #-}
+{-# LANGUAGE NoFieldSelectors #-}
+{-# LANGUAGE FlexibleInstances #-}
+{-# LANGUAGE MultiParamTypeClasses #-}
 -- | Monad for the resolvable computation.
 
 module Language.Java.Classfile.Resolver (Resolver, State(..), Reply(..), runResolver, enterDatatype, enterConstructor, enterField) where
@@ -10,6 +13,7 @@ module Language.Java.Classfile.Resolver (Resolver, State(..), Reply(..), runReso
 import Language.Java.Classfile.ConstantPool (ConstantPool)
 import Language.Java.Classfile.Stage ( Stage(Parse) )
 import Data.Text (Text)
+import Control.Monad.Reader (MonadReader (local), ask)
 
 -- | Fed to the Resolver Monad
 
@@ -25,12 +29,15 @@ data Reply a = Reply
   }
   deriving stock (Functor)
 
+-- | Contains a computation that will resolve to something of type 'a' when supplied with a 'ConstantPool'.
 
 newtype Resolver a = Resolver (State -> Reply a)
   deriving stock (Functor)
 
-runResolver :: State -> Resolver a -> Reply a
-runResolver state (Resolver computeReply) = computeReply state
+-- | Supply the constant pool needed for the computation.
+
+runResolver :: ConstantPool Parse -> Resolver a -> Reply a
+runResolver pool (Resolver computeReply) = computeReply (State pool)
 
 instance Applicative Resolver where
   pure :: a -> Resolver a
@@ -53,6 +60,15 @@ instance Monad Resolver where
 
     in computeB replyA.nextState
 
+instance MonadReader (ConstantPool Parse) Resolver where
+  ask :: Resolver (ConstantPool Parse)
+  ask = Resolver $ \ input -> Reply input input.pool
+  
+  local :: (ConstantPool Parse -> ConstantPool Parse) -> Resolver a -> Resolver a
+  local f (Resolver computeA) = Resolver $ \ input -> let
+    modifiedInput = input { pool = f input.pool }
+    in computeA modifiedInput
+
 enterDatatype, enterConstructor, enterField :: Text -> Resolver a -> Resolver a
 enterDatatype    name body = body
 enterConstructor name body = body