1 files changed, 31 insertions, 0 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