{-# LANGUAGE DeriveGeneric #-}
{-# LANGUAGE OverloadedStrings #-} --needed for ByteString arguments
module DataTypes where
import Data.Aeson
import GHC.Generics
import qualified Data.ByteString.Lazy.Char8 as BL


data Location = Location
  { name :: String
  , region :: String
  , country :: String
  , lat :: Float
  , lon :: Float
  , tz_id :: String
  , localtime_epoch :: Int
  , localtime :: String
  } deriving (Show, Generic)


data Current = Current
  { temp_c :: Float
  } deriving (Show, Generic)


data Day = Day
  { avgtemp_c :: Float
  } deriving (Show, Generic)


data ForecastDay = ForecastDay
  { day :: Day
  } deriving (Show, Generic)


data Forecast = Forecast
  { forecastday :: [ForecastDay]
  } deriving (Show, Generic)


data WeatherResponse = WeatherResponse
    { location :: Location
    , current :: Maybe Current
    , forecast :: Maybe Forecast
    } deriving (Show, Generic)


instance FromJSON Location
instance ToJSON Location
instance FromJSON Current
instance ToJSON Current
instance FromJSON Day
instance ToJSON Day
instance FromJSON ForecastDay
instance ToJSON ForecastDay
instance FromJSON Forecast
instance ToJSON Forecast
instance FromJSON WeatherResponse
instance ToJSON WeatherResponse


weatherDecode :: BL.ByteString -> IO WeatherResponse
weatherDecode jsonBody =
    case decode jsonBody :: Maybe WeatherResponse of
        Just decoded -> return decoded
        Nothing -> error "Invalid JSON"

getTemperature :: WeatherResponse -> Float
getTemperature (WeatherResponse _ Nothing Nothing) = error "No data provided!"
getTemperature (WeatherResponse _ (Just curr) Nothing) = getTemperatureFromCurrent curr
getTemperature (WeatherResponse _ Nothing (Just fore)) = getTemperatureFromForecastDay $ getForecastDayFromForecast fore
getTemperature (WeatherResponse _ (Just _) (Just fore)) = getTemperatureFromForecastDay $ getForecastDayFromForecast fore

getForecastDayFromForecast :: Forecast -> ForecastDay
getForecastDayFromForecast (Forecast forecasts) = head forecasts

getTemperatureFromCurrent :: Current -> Float
getTemperatureFromCurrent (Current temp) = temp

getTemperatureFromForecastDay :: ForecastDay -> Float
getTemperatureFromForecastDay (ForecastDay (Day temp)) = temp