{-# LANGUAGE OverloadedStrings #-}

import Data.Aeson
import Data.Aeson.Types
import Data.Time
import Data.Text

import qualified Data.HashMap.Strict as HM

parseRecords :: Value -> Parser [(Day, Double)]
parseRecords = withObject "record" $ \obj -> do
    mapM (uncurry parseRecord) (HM.toList obj)
    where
        parseRecord :: Text -> Value -> Parser (Day, Double)
        parseRecord s val = flip (withText "price") val $ \text -> do
          day <- getDay $ unpack s
          return (day, getPrice text)
        getDay str = parseTimeM True defaultTimeLocale "%Y-%m-%d" str :: Parser Day
        getPrice str = read $ unpack str :: Double