4 files changed, 42 insertions, 8 deletions

diff --git a/src/Data/Torrent/JSON.hs b/src/Data/Torrent/JSON.hs
new file mode 100644
index 00000000..3fa8973d
--- /dev/null
+++ b/src/Data/Torrent/JSON.hs
@@ -0,0 +1,31 @@
+module Data.Torrent.JSON
+       ( omitLensPrefix
+       , omitRecordPrefix
+       ) where
+
+import Data.Aeson.TH
+import Data.Char
+import Data.List as L
+
+
+-- | Ignore '_' prefix.
+omitLensPrefix :: Options
+omitLensPrefix = defaultOptions
+  { fieldLabelModifier     = L.dropWhile (== '_')
+  , constructorTagModifier = id
+  , allNullaryToStringTag  = True
+  , omitNothingFields      = True
+  }
+
+mapWhile :: (a -> Bool) -> (a -> a) -> [a] -> [a]
+mapWhile p f = go
+  where
+    go []       = []
+    go (x : xs)
+      |    p x    = f x : go xs
+      | otherwise = xs
+
+omitRecordPrefix :: Options
+omitRecordPrefix = omitLensPrefix
+  { fieldLabelModifier = mapWhile isUpper toLower . L.dropWhile isLower
+  }
\ No newline at end of file
diff --git a/src/Data/Torrent/Layout.hs b/src/Data/Torrent/Layout.hs
index a32d74fa..453c0d4f 100644
--- a/src/Data/Torrent/Layout.hs
+++ b/src/Data/Torrent/Layout.hs
@@ -70,7 +70,6 @@ import Data.BEncode.Types
 import Data.ByteString as BS
 import Data.ByteString.Base16 as Base16
 import Data.ByteString.Char8 as BC
-import Data.Char as Char
 import Data.Foldable as F
 import Data.List as L
 import Data.Text as T
@@ -81,6 +80,7 @@ import Text.PrettyPrint.Class
 import System.FilePath
 import System.Posix.Types
 
+import Data.Torrent.JSON
 
 {-----------------------------------------------------------------------
 --  File attribytes
@@ -123,7 +123,7 @@ data FileInfo a = FileInfo {
                , Functor, Foldable
                )
 
-$(deriveJSON defaultOptions { fieldLabelModifier =  (L.map Char.toLower . L.dropWhile isLower) } ''FileInfo)
+$(deriveJSON omitRecordPrefix ''FileInfo)
 
 makeLensesFor
   [ ("fiLength", "fileLength")
@@ -208,7 +208,7 @@ data LayoutInfo
     , liDirName  :: !ByteString
     } deriving (Show, Read, Eq, Typeable)
 
-$(deriveJSON defaultOptions { fieldLabelModifier =  (L.map Char.toLower . L.dropWhile isLower) } ''LayoutInfo)
+$(deriveJSON omitRecordPrefix ''LayoutInfo)
 
 makeLensesFor
   [ ("liFile"   , "singleFile" )
diff --git a/src/Data/Torrent/Piece.hs b/src/Data/Torrent/Piece.hs
index 00d4b843..d79da2ee 100644
--- a/src/Data/Torrent/Piece.hs
+++ b/src/Data/Torrent/Piece.hs
@@ -54,14 +54,15 @@ import Data.Bits.Extras
 import           Data.ByteString as BS
 import qualified Data.ByteString.Lazy as BL
 import qualified Data.ByteString.Base64 as Base64
-import Data.Char
 import Data.Int
-import Data.List as L
 import Data.Text.Encoding as T
 import Data.Typeable
 import Text.PrettyPrint
 import Text.PrettyPrint.Class
 
+import Data.Torrent.JSON
+
+
 -- TODO add torrent file validation
 class Lint a where
    lint :: a -> Either String a
@@ -129,7 +130,7 @@ data Piece a = Piece
   , pieceData  :: !a
   } deriving (Show, Read, Eq, Functor, Typeable)
 
-$(deriveJSON defaultOptions { fieldLabelModifier =  (L.map toLower . L.dropWhile isLower) } ''Piece)
+$(deriveJSON omitRecordPrefix ''Piece)
 
 instance NFData (Piece a)
 
@@ -166,7 +167,7 @@ data PieceInfo = PieceInfo
     -- ^ Concatenation of all 20-byte SHA1 hash values.
   } deriving (Show, Read, Eq, Typeable)
 
-$(deriveJSON defaultOptions { fieldLabelModifier =  (L.map toLower . L.dropWhile isLower) } ''PieceInfo)
+$(deriveJSON omitRecordPrefix ''PieceInfo)
 
 -- | Number of bytes in each piece.
 makeLensesFor [("piPieceLength", "pieceLength")] ''PieceInfo
diff --git a/src/Data/Torrent/Progress.hs b/src/Data/Torrent/Progress.hs
index 34f8f299..ffcbf2aa 100644
--- a/src/Data/Torrent/Progress.hs
+++ b/src/Data/Torrent/Progress.hs
@@ -49,6 +49,8 @@ import Network.HTTP.Types.QueryLike
 import Text.PrettyPrint as PP
 import Text.PrettyPrint.Class
 
+import Data.Torrent.JSON
+
 
 -- | Progress data is considered as dynamic within one client
 -- session. This data also should be shared across client application
@@ -62,7 +64,7 @@ data Progress = Progress
   } deriving (Show, Read, Eq)
 
 $(makeLenses ''Progress)
-$(deriveJSON defaultOptions { fieldLabelModifier = L.tail } ''Progress)
+$(deriveJSON omitLensPrefix ''Progress)
 
 -- | UDP tracker compatible encoding.
 instance Serialize Progress where