batteryCapacityFile = "/sys/class/power_supply/BAT0/capacity" :: FilePath
batteryStatusFile = "/sys/class/power_supply/BAT0/status" :: FilePath

main :: IO ()
main = do
    batteryCapacity <- readFile batteryCapacityFile
    batteryStatus <- readFile batteryStatusFile
    putStrLn $ formatInfo batteryStatus batteryCapacity

formatInfo :: String -> String -> String
formatInfo status capacity = icon ++ " " ++ init capacity ++ "%"
    where icon
            | init status == "Full" = "🙂"
            | init status == "Charging" = "🔋"
            | init status == "Not charging" = "♻"
            | init status == "Unknown" = "Unknown"
            | read capacity <= 20 = "🪫"
            | read capacity <= 100 = "🙃"
            | otherwise = "Silly"