{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE RecordWildCards   #-}

import           Data.Aeson                 as AE
import           Data.Aeson.Types           as AET
import           Data.ByteString.Lazy       as BL
import           Data.ByteString.Lazy.Char8 as BL8
import           Data.HashMap.Strict        as HM
import           Prelude                    as P

data Team = Team { _id :: Value, country :: Value } deriving (Show)

instance ToJSON Team where
    toJSON Team{..} = object [ "i" .= _id, "c" .= country ]

instance FromJSON Team where
    parseJSON = withObject "team" $ \o -> do
        _id <- o .: "id"
        country <- o .: "title"
        return Team{..}

reduce :: [Team] -> Value -> [Team]
reduce acc x = case (parseEither parseJSON x :: Either String Team) of
    (Left s)  -> error s
    (Right v) -> v : acc

parseTeams :: Either String [Value] -> [Team]
parseTeams (Left x)   = error x
parseTeams (Right xs) = P.foldl reduce [] xs

parseResult :: [Team] -> [(String, Value)]
parseResult = P.foldl (\acc x -> (extractId x, country x) : acc) []
    where
        extractId = BL8.unpack . encode . _id

main :: IO ()
main = do
    src <- BL.readFile "./data/teams.json"
    let teams = parseTeams (AE.eitherDecode src :: Either String [Value])
    BL.writeFile "teams.json" $ encode $ HM.fromList $ parseResult teams