{-# LANGUAGE CPP #-}
{-# LANGUAGE JavaScriptFFI #-}

{-# OPTIONS_HADDOCK hide #-} -- for doctests

module Chronos.Internal.CTimespec
  (
#ifndef mingw32_HOST_OS
    getPosixNanoseconds
#ifndef ghcjs_HOST_OS
  , CTimespec(..)
#endif
#endif
  ) where

import Foreign
import Foreign.C

#if defined(ghcjs_HOST_OS)

foreign import javascript unsafe "Date.now()" currentSeconds :: IO Double
getPosixNanoseconds :: IO Int64
getPosixNanoseconds = do
  x <- currentSeconds
  pure $ fromIntegral $ 1000000 * (round x)

#elif defined(mingw32_HOST_OS)

#else

data CTimespec = CTimespec
  { ctimespecSeconds :: {-# UNPACK #-} !CTime
  , ctimespecNanoseconds :: {-# UNPACK #-} !CLong
  }

instance Storable CTimespec where
    sizeOf _ = (16)
    alignment _ = alignment (undefined :: CLong)
    peek p = do
        s  <- (\hsc_ptr -> peekByteOff hsc_ptr 0) p
        ns <- (\hsc_ptr -> peekByteOff hsc_ptr 8) p
        return (CTimespec s ns)
    poke p (CTimespec s ns) = do
        (\hsc_ptr -> pokeByteOff hsc_ptr 0) p s
        (\hsc_ptr -> pokeByteOff hsc_ptr 8) p ns

#ifdef darwin_HOST_OS
foreign import ccall unsafe "cbits/hs-time.c clock_gettime"
    clock_gettime :: Int32 -> Ptr CTimespec -> IO CInt
#else
foreign import ccall unsafe "time.h clock_gettime"
    clock_gettime :: Int32 -> Ptr CTimespec -> IO CInt
#endif

-- | Get the current POSIX time from the system clock.
getPosixNanoseconds :: IO Int64
getPosixNanoseconds = do
  CTimespec (CTime s) (CLong ns) <- alloca $ \ptspec -> do
    throwErrnoIfMinus1_ "clock_gettime" $
      clock_gettime 0 ptspec
    peek ptspec
  -- On most 64-bit platforms, the uses of fromIntegral here end up
  -- being i64->i64, but on 32-bit platforms, they are i32->i64.
  return ((fromIntegral s * 1000000000) + fromIntegral ns)

#endif