{-# LANGUAGE ForeignFunctionInterface #-}

#ifndef mingw32_HOST_OS
#include <sys/time.h>
#endif

module Data.Thyme.Clock.POSIX
    ( posixDayLength
    , module Data.Thyme.Clock.POSIX
    ) where

import Prelude
import Control.Lens
import Data.AdditiveGroup
import Data.Thyme.Internal.Micro
import Data.Thyme.Clock.Internal
import Data.VectorSpace

#ifdef mingw32_HOST_OS
import System.Win32.Time
#else
import Foreign.C.Error (throwErrnoIfMinus1_)
import Foreign.C.Types
import Foreign.Marshal.Alloc (allocaBytes)
import Foreign.Ptr (Ptr, nullPtr)
import Foreign.Storable
#endif

type POSIXTime = NominalDiffTime

{-# INLINE posixTime #-}
posixTime :: Iso' UTCTime POSIXTime
posixTime = iso (\ (UTCRep t) -> t ^-^ unixEpoch)
        (UTCRep . (^+^) unixEpoch) where
    unixEpoch = {-ModifiedJulianDay-}40587 *^ posixDayLength

{-# INLINE getPOSIXTime #-}
getPOSIXTime :: IO POSIXTime
#ifdef mingw32_HOST_OS

-- On Windows, the equlvalent of POSIX time is "file time", defined as
-- the number of 100-nanosecond intervals that have elapsed since
-- 12:00 AM January 1, 1601 (UTC). We can convert this into a POSIX
-- time by adjusting the offset to be relative to the POSIX epoch.
getPOSIXTime = do
    FILETIME ft <- System.Win32.Time.getSystemTimeAsFileTime
    return . NominalDiffTime . Micro . fromIntegral $
        quot ft 10 - 11644473600000000{-ftEpoch ^. microseconds-}
--  ftEpoch = utcTime # UTCTime (gregorian # YearMonthDay 1601 1 1) zeroV

#else

getPOSIXTime = allocaBytes #{size struct timeval} $ \ ptv -> do
    throwErrnoIfMinus1_ "gettimeofday" $ gettimeofday ptv nullPtr
    CTime sec <- #{peek struct timeval, tv_sec} ptv
    CSUSeconds usec <- #{peek struct timeval, tv_usec} ptv
    return . NominalDiffTime . Micro $
        1000000 * fromIntegral sec + fromIntegral usec

foreign import ccall unsafe "time.h gettimeofday"
    gettimeofday :: Ptr () -> Ptr () -> IO CInt

#endif