{-|
Module      : Utils.Time
Copyright   : (c) UU, 2019
License     : MIT
Maintainer  : Tom Smeding
Stability   : experimental
Portability : POSIX, macOS, Windows
-}
module Utils.Time where

import Data.Time.Clock.System hiding (getSystemTime)
import qualified Data.Time.Clock.System as Sys


-- | A timestamp in milliseconds.
newtype TimeStamp = TimeStamp Int
  deriving (Show, Read, Eq, Ord)

-- | The number of milliseconds stored in the timestamp newtype.
timestampMS :: TimeStamp -> Int
timestampMS (TimeStamp n) = n

-- | Offset the timestamp by the given number of milliseconds.
plusMS :: TimeStamp -> Int -> TimeStamp
plusMS (TimeStamp n) m = TimeStamp (n + m)

-- | The number of milliseconds that the first timestamp is later than the
-- second.
subtractMS :: TimeStamp -> TimeStamp -> Int
subtractMS (TimeStamp n) (TimeStamp m) = n - m

-- | Return the current system time as a timestamp.
getSystemTime :: IO TimeStamp
getSystemTime = TimeStamp . systemToMS <$> Sys.getSystemTime
  where
    systemToMS tm = let MkSystemTime s ns = truncateSystemTimeLeapSecond tm
                    in fromIntegral s * 1000 + fromIntegral ns `div` 1000000