add FromJSON instances to converters (WIP)

src/ToySolver/Converter/Base.hs

@@ -2,6 +2,7 @@
 {-# OPTIONS_HADDOCK show-extensions #-}
 {-# LANGUAGE FlexibleContexts #-}
 {-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE ScopedTypeVariables #-}
 {-# LANGUAGE TypeFamilies #-}
 {-# LANGUAGE TypeOperators #-}
 -----------------------------------------------------------------------------
@@ -27,8 +28,10 @@ module ToySolver.Converter.Base
   , ReversedTransformer (..)
   ) where
 
+import Control.Monad
 import qualified Data.Aeson as J
-import Data.Aeson ((.=))
+import Data.Aeson ((.=), (.:))
+import qualified Data.Text as T
 
 class (Eq a, Show a) => Transformer a where
   type Source a
@@ -89,6 +92,16 @@ instance (J.ToJSON a, J.ToJSON b) => J.ToJSON (ComposedTransformer a b) where
     , "second" .= b
     ]
 
+instance (J.FromJSON a, J.FromJSON b) => J.FromJSON (ComposedTransformer a b) where
+  parseJSON = J.withObject name $ \v -> do
+    (t :: T.Text) <- v .: "type"
+    unless (t == T.pack name) $ fail ("expectec type " ++ show name ++ ", but found type " ++ show t)
+    ComposedTransformer
+      <$> v .: "first"
+      <*> v .: "second"
+    where
+      name = "ComposedTransformer"
+
 
 data IdentityTransformer a = IdentityTransformer
   deriving (Eq, Show, Read)
@@ -109,6 +122,14 @@ instance J.ToJSON (IdentityTransformer a) where
     [ "type" .= J.String "IdentityTransformer"
     ]
 
+instance J.FromJSON (IdentityTransformer a) where
+  parseJSON = J.withObject name $ \v -> do
+    (t :: T.Text) <- v .: "type"
+    unless (t == T.pack name) $ fail ("expectec type " ++ show name ++ ", but found type " ++ show t)
+    pure IdentityTransformer
+    where
+      name = "IdentityTransformer"
+
 
 data ReversedTransformer t = ReversedTransformer t
   deriving (Eq, Show, Read)
@@ -139,3 +160,11 @@ instance J.ToJSON t => J.ToJSON (ReversedTransformer t) where
     [ "type" .= J.String "ReversedTransformer"
     , "base" .= t
     ]
+
+instance J.FromJSON t => J.FromJSON (ReversedTransformer t) where
+  parseJSON = J.withObject name $ \v -> do
+    (t :: T.Text) <- v .: "type"
+    unless (t == T.pack name) $ fail ("expectec type " ++ show name ++ ", but found type " ++ show t)
+    ReversedTransformer <$> v .: "base"
+    where
+      name = "ReversedTransformer"