50 lines
1.7 KiB
Haskell
50 lines
1.7 KiB
Haskell
-- | Filesystem polling with an inotify backend. Works only on linux.
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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.Monad (forM_, when)
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import Data.Set (Set)
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import qualified Data.Set as S
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import System.FilePath (takeDirectory, (</>))
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import Data.List (isPrefixOf)
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import System.INotify
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import Hakyll.Core.Configuration
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import Hakyll.Core.Resource
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-- | Calls the given callback when the directory tree changes
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--
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previewPoll :: HakyllConfiguration -- ^ Configuration
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-> Set Resource -- ^ Resources to watch
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-> IO () -- ^ Action called when something changes
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-> IO () -- ^ Can block forever
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previewPoll _ resources callback = do
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-- Initialize inotify
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inotify <- initINotify
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let -- A set of file paths
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paths = S.map unResource resources
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-- A list of directories. Run it through a set so we have every
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-- directory only once.
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directories = S.toList $ S.map (notEmpty . takeDirectory) paths
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-- Problem: we can't add a watcher for "". So we make sure a directory
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-- name is not empty
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notEmpty "" = "."
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notEmpty x = x
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-- Execute the callback when path is known
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ifResource path =
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let path' = if "./" `isPrefixOf` path then drop 2 path else path
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in when (path' `S.member` paths) callback
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-- Add a watcher for every directory
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forM_ directories $ \directory -> do
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_ <- addWatch inotify [Modify] directory $ \e -> case e of
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(Modified _ (Just p)) -> ifResource $ directory </> p
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_ -> return ()
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return ()
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