{-# LANGUAGE OverloadedStrings #-} --needed for ByteString arguments
import Network.HTTP.Simple
import System.Environment (lookupEnv)
import Data.ByteString.UTF8 (fromString) --to convert acquired API key to ByteString
import Data.Time as T

import Plot
import qualified DataTypes as DT

data WhichDay = Yesterday | Today | Tomorrow
    deriving (Show, Eq)


main :: IO ()
main = do
    apiKey <- getWeatherKey

    putStrLn "Enter a city name: "
    city <- getLine

    let cityRequest = apiRequestCity apiKey city
    cityResponse <- httpLBS cityRequest

    if getResponseBody cityResponse == "[]" || getResponseStatusCode cityResponse /= 200
    then error "City not found!"
    else do
        currentDate <- getCurrentDate

        --request for yesterday's weather
        let yesterdayDate = formatDate $ addDays (-1) currentDate
        let yesterdayRequest = apiRequestBuilder apiKey Yesterday city yesterdayDate
        yesterdayResponse <- httpLBS yesterdayRequest
        yesterdayDecoded <- DT.weatherDecode $ getResponseBody yesterdayResponse
        putStr $ "Yesterday's temperature: " ++ show (DT.getTemperature yesterdayDecoded) ++ " celsius\n"

        --request for today's weather
        let todayDate = formatDate currentDate
        let todayRequest = apiRequestBuilder apiKey Today city todayDate
        todayResponse <- httpLBS todayRequest
        todayDecoded <- DT.weatherDecode $ getResponseBody todayResponse
        putStr $ "Today's temperature: " ++ show (DT.getTemperature todayDecoded) ++ " celsius\n"

        --request for tomorrow's weather
        let tomorrowDate = formatDate $ addDays 1 currentDate
        let tomorrowRequest = apiRequestBuilder apiKey Tomorrow city tomorrowDate
        tomorrowResponse <- httpLBS tomorrowRequest
        tomorrowDecoded <- DT.weatherDecode $ getResponseBody tomorrowResponse
        putStr $ "Tomorrow's temperature: " ++ show (DT.getTemperature tomorrowDecoded) ++ " celsius\n"

        generatePlot (DT.getTemperature yesterdayDecoded) (DT.getTemperature todayDecoded) (DT.getTemperature tomorrowDecoded)
        openPlot


--apiKey is stored in an env variable, not something that should be pushed onto git
getWeatherKey :: IO String
getWeatherKey = do
    result <- lookupEnv "WEATHER_API_KEY"
    case result of
        Just a -> return a
        Nothing -> error "API key not set in environmental variables!" -- exception thrown (but not handled) per project requirement


apiRequestCity :: String -> String -> Request
apiRequestCity apiKey city =
            setRequestHost "api.weatherapi.com"
            $ setRequestPath "/v1/search.json"
            $ setRequestMethod "GET"
            $ setRequestQueryString [("key", Just (fromString apiKey)), ("q", Just (fromString city))]
            $ setRequestPort 443
            $ setRequestSecure True defaultRequest


apiRequestBuilder :: String -> WhichDay -> String -> String -> Request
apiRequestBuilder apiKey day city date =
            setRequestHost "api.weatherapi.com"
            $ setRequestPath path
            $ setRequestMethod "GET"
            $ setRequestQueryString query
            $ setRequestPort 443
            $ setRequestSecure True defaultRequest
                where {
                    path
                        | day == Yesterday = "/v1/history.json"
                        | day == Today = "/v1/current.json"
                        | day == Tomorrow = "/v1/forecast.json"
                        | otherwise = error "Invalid day argument!";
                    query
                        | day == Yesterday = [("key", Just (fromString apiKey)), ("q", Just (fromString city)), ("dt", Just (fromString date))]
                        | day == Today = [("key", Just (fromString apiKey)), ("q", Just (fromString city))]
                        | day == Tomorrow = [("key", Just (fromString apiKey)), ("q", Just (fromString city)), ("dt", Just (fromString date)), ("days", Just (fromString "1"))]
                        | otherwise = error "Invalid day argument!";
                    }


getCurrentDate :: IO T.Day
getCurrentDate = do
    currentTime <- getCurrentTime
    timeZone <- getCurrentTimeZone
    let localTime = utcToLocalTime timeZone currentTime
    let currentDate = localDay localTime
    return currentDate


formatDate :: T.Day -> String
formatDate = formatTime defaultTimeLocale "%Y-%m-%d"