{-|
Ministries can be encoded to and decoded from JSON:

>>> import Data.Aeson (decode, encode)
>>> import Data.ByteString.Lazy.Char8 (pack)

>>> encode Defense
"\"Defense\""

>>> encode [ Defense, Welfare ]
"[\"Defense\",\"Welfare\"]"

>>> decode . pack $ "[ \"Science\" ]" :: Maybe [Ministry]
Just [Science]
-}
{-# LANGUAGE DeriveAnyClass #-}
{-# LANGUAGE DeriveGeneric #-}

module Malodivo.Types.Ministry
  ( Ministry(..)
  , MinistryInfo
  , MinistryLimits
  , mi2ml
  ) where

import Control.Arrow ((&&&))
import GHC.Generics (Generic)

import Data.Aeson (FromJSON, ToJSON)
import qualified Data.HashMap.Strict as HM
import Data.Hashable (Hashable)

-- | Ministry of the Kingdom of Malodivo.
data Ministry
  = Defense
  | Science
  | Welfare
  deriving (Eq, Hashable, Show, Generic, FromJSON, ToJSON)

-- | Convenient type. Describes maximum money a ministry can get.
type MinistryLimits = HM.HashMap Ministry Integer

{-|
We use this data type instead of 'MinistryLimits' 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 MinistryInfo = MinistryInfo
  { name :: Ministry
  , amount :: Integer
  } deriving (Generic, FromJSON)

mi2ml :: [MinistryInfo] -> MinistryLimits
mi2ml = HM.fromListWith (+) . map (name &&& amount)