1 files changed, 27 insertions, 7 deletions
diff --git a/lib/Malodivo/Types/District.hs b/lib/Malodivo/Types/District.hs
index 058377b..2e78634 100644
--- a/lib/Malodivo/Types/District.hs
+++ b/lib/Malodivo/Types/District.hs
@@ -18,11 +18,17 @@ Just [Lakos]
 
 module Malodivo.Types.District
   ( District(..)
+  , DistrictFunds
+  , DistrictInfo(..)
+  , di2df
+  , df2di
   ) where
 
+import Control.Arrow ((&&&))
 import GHC.Generics (Generic)
 
 import Data.Aeson (FromJSON, ToJSON)
+import qualified Data.HashMap.Strict as HM
 import Data.Hashable (Hashable)
 
 -- | District of the Kindom of Malodivo.
@@ -30,10 +36,24 @@ data District
   = Palolene
   | SouthernPalolene
   | Lakos
-  deriving ( Eq
-           , Hashable
-           , Show
-           , Generic
-           , FromJSON
-           , ToJSON
-           )
+  deriving (Eq, Hashable, Show, Generic, FromJSON, ToJSON)
+
+-- | Convenient type.
+type DistrictFunds = HM.HashMap District Integer
+
+{-|
+We use this data type instead of 'DistrictFunds' for JSON,
+because maps other than @HashMap Text _@ are hard to decode/encode see
+<https://github.com/bos/aeson/issues/79>.  Anyway, we still have type-checked
+typos-proof structure.
+-}
+data DistrictInfo = DistrictInfo
+  { name :: District
+  , amount :: Integer
+  } deriving (Generic, FromJSON, ToJSON)
+
+di2df :: [DistrictInfo] -> DistrictFunds
+di2df = HM.fromListWith (+) . map (name &&& amount)
+
+df2di :: DistrictFunds -> [DistrictInfo]
+df2di = map (\(n, a) -> DistrictInfo {name = n, amount = a}) . HM.toList