Revert "Remove check for DRep metadata size"

cardano-api/internal/Cardano/Api/DRepMetadata.hs

@@ -7,14 +7,16 @@
 module Cardano.Api.DRepMetadata (
     -- * DRep off-chain metadata
     DRepMetadata(..),
-    hashDRepMetadata,
+    validateAndHashDRepMetadata,
+    DRepMetadataValidationError(..),
 
     -- * Data family instances
     AsType(..),
     Hash(..),
   ) where
 
 import           Cardano.Api.Eras
+import           Cardano.Api.Error
 import           Cardano.Api.Hash
 import           Cardano.Api.HasTypeProxy
 import           Cardano.Api.Keys.Byron
@@ -27,7 +29,9 @@ import           Cardano.Ledger.Crypto (StandardCrypto)
 import qualified Cardano.Ledger.Keys as Shelley
 
 import           Data.ByteString (ByteString)
+import qualified Data.ByteString as BS
 import           Data.Either.Combinators (maybeToRight)
+import           Prettyprinter
 
 -- ----------------------------------------------------------------------------
 -- DRep metadata
@@ -53,12 +57,37 @@ instance SerialiseAsRawBytes (Hash DRepMetadata) where
     maybeToRight (SerialiseAsRawBytesError "Unable to deserialise Hash DRepMetadata") $
       DRepMetadataHash <$> Crypto.hashFromBytes bs
 
--- | Return the decoded metadata and the hash of the original bytes.
-hashDRepMetadata
-  :: ByteString
-  -> (DRepMetadata, Hash DRepMetadata)
-hashDRepMetadata bs =
-  let md  = DRepMetadata bs
-      mdh = DRepMetadataHash (Crypto.hashWith id bs) in
-  (md, mdh)
+-- | A drep metadata validation error.
+data DRepMetadataValidationError
+  = DRepMetadataInvalidLengthError
+    -- ^ The length of the JSON-encoded drep metadata exceeds the
+    -- maximum.
+      !Int
+      -- ^ Maximum byte length.
+      !Int
+      -- ^ Actual byte length.
+  deriving Show
+
+instance Error DRepMetadataValidationError where
+  prettyError = \case
+    DRepMetadataInvalidLengthError maxLen actualLen ->
+      mconcat
+        [ "DRep metadata must consist of at most "
+        , pretty maxLen
+        , " bytes, but it consists of "
+        , pretty actualLen
+        , " bytes."
+        ]
 
+-- | Decode and validate the provided JSON-encoded bytes as 'DRepMetadata'.
+-- Return the decoded metadata and the hash of the original bytes.
+validateAndHashDRepMetadata
+  :: ByteString
+  -> Either DRepMetadataValidationError (DRepMetadata, Hash DRepMetadata)
+validateAndHashDRepMetadata bs
+  -- TODO confirm if there are size limits to the DRep metadata
+  | BS.length bs <= 512 = do
+      let md = DRepMetadata bs
+      let mdh = DRepMetadataHash (Crypto.hashWith id bs)
+      return (md, mdh)
+  | otherwise = Left $ DRepMetadataInvalidLengthError 512 (BS.length bs)

cardano-api/src/Cardano/Api.hs

@@ -969,7 +969,8 @@ module Cardano.Api (
     DRepExtendedKey,
     DRepMetadata,
     DRepMetadataReference,
-    hashDRepMetadata,
+    DRepMetadataValidationError,
+    validateAndHashDRepMetadata,
 
     -- ** Governance related certificates
     AnchorDataHash(..),