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{-|
Districts can be encoded to and decoded from JSON:
>>> import Data.Aeson (decode, encode)
>>> import Data.ByteString.Lazy.Char8 (pack)
>>> encode Palolene
"\"Palolene\""
>>> encode [ Lakos, SouthernPalolene ]
"[\"Lakos\",\"SouthernPalolene\"]"
>>> decode . pack $ "[ \"Lakos\" ]" :: Maybe [District]
Just [Lakos]
-}
{-# LANGUAGE DeriveAnyClass #-}
{-# LANGUAGE DeriveGeneric #-}
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.
data District
= Palolene
| SouthernPalolene
| Lakos
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
|
