35 lines
1.1 KiB
Haskell
35 lines
1.1 KiB
Haskell
-- | Interval-based implementation of preview polling, for the platforms which
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-- are not supported by inotify.
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--
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module Hakyll.Web.Preview.Poll
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( previewPoll
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) where
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import Control.Applicative ((<$>))
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import Control.Concurrent (threadDelay)
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import Control.Monad (filterM)
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import System.Time (getClockTime)
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import System.Directory (getModificationTime, doesFileExist)
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import Hakyll.Core.Configuration
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-- | A preview thread that periodically recompiles the site.
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--
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previewPoll :: HakyllConfiguration -- ^ Configuration
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-> IO [FilePath] -- ^ Updating action
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-> IO () -- ^ Can block forever
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previewPoll _ update = do
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time <- getClockTime
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loop time =<< update
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where
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delay = 1000000
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loop time files = do
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threadDelay delay
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files' <- filterM doesFileExist files
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filesTime <- case files' of
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[] -> return time
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_ -> maximum <$> mapM getModificationTime files'
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if filesTime > time || files' /= files
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then loop filesTime =<< update
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else loop time files'
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