module Hakyll.Web.Preview.Poll
( previewPoll
) where
import Control.Applicative ((<$>))
import Control.Concurrent (threadDelay)
import Control.Monad (when, filterM)
import System.Time (getClockTime)
import Data.Set (Set)
import qualified Data.Set as S
import System.Directory (getModificationTime, doesFileExist)
import Hakyll.Core.Configuration
import Hakyll.Core.Resource
previewPoll :: HakyllConfiguration
-> Set Resource
-> IO ()
-> IO ()
previewPoll _ resources callback = do
let files = map unResource $ S.toList resources
time <- getClockTime
loop files time
where
delay = 1000000
loop files time = do
threadDelay delay
files' <- filterM doesFileExist files
modified <- any (time <) <$> mapM getModificationTime files'
when (modified || files' /= files) callback
loop files' =<< getClockTime