{-|
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