src/Hakyll/Preview/Poll.hs · hakyll

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1--------------------------------------------------------------------------------

2-- | Interval-based implementation of preview polling

3{-# LANGUAGE CPP #-}

4module Hakyll.Preview.Poll

5 ( previewPoll

6 ) where

9--------------------------------------------------------------------------------

10import Control.Applicative ((<$>))

11import Control.Concurrent (threadDelay)

12import Control.Monad (filterM)

13#if MIN_VERSION_directory(1,2,0)

14import Data.Time (getCurrentTime)

15#else

16import System.Time (getClockTime)

17#endif

18import System.Directory (doesFileExist, getModificationTime)

21--------------------------------------------------------------------------------

22import Hakyll.Core.Configuration

25--------------------------------------------------------------------------------

26-- | A preview thread that periodically recompiles the site.

27previewPoll :: Configuration -- ^ Configuration

28 -> IO [FilePath] -- ^ Updating action

29 -> IO () -- ^ Can block forever

30previewPoll _ update = do

31#if MIN_VERSION_directory(1,2,0)

32 time <- getCurrentTime

33#else

34 time <- getClockTime

35#endif

36 loop time =<< update

37 where

38 delay = 1000000

39 loop time files = do

40 threadDelay delay

41 files' <- filterM doesFileExist files

42 filesTime <- case files' of

43 [] -> return time

44 _ -> maximum <$> mapM getModificationTime files'

46 if filesTime > time || files' /= files

47 then loop filesTime =<< update

48 else loop time files'