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--------------------------------------------------------------------------------
{-# LANGUAGE CPP #-}
module Hakyll.Preview.Poll
( watchUpdates
) where
--------------------------------------------------------------------------------
import Control.Concurrent (forkIO)
import Control.Concurrent.MVar (newEmptyMVar, takeMVar,
tryPutMVar)
import Control.Exception (AsyncException, fromException,
handle, throw)
import Control.Monad (forever, void, when)
import System.Directory (canonicalizePath)
import System.FilePath (pathSeparators)
import qualified System.FSNotify as FSNotify
#ifdef mingw32_HOST_OS
import Control.Concurrent (threadDelay)
import Control.Exception (IOException, throw, try)
import System.Directory (doesFileExist)
import System.Exit (exitFailure)
import System.FilePath ((</>))
import System.IO (Handle, IOMode (ReadMode),
hClose, openFile)
import System.IO.Error (isPermissionError)
#endif
--------------------------------------------------------------------------------
import Hakyll.Core.Configuration
import Hakyll.Core.Identifier
import Hakyll.Core.Identifier.Pattern
--------------------------------------------------------------------------------
-- | A thread that watches for updates in a 'providerDirectory' and recompiles
-- a site as soon as any changes occur
watchUpdates :: Configuration -> IO Pattern -> IO ()
watchUpdates conf update = do
let providerDir = providerDirectory conf
shouldBuild <- newEmptyMVar
pattern <- update
fullProviderDir <- canonicalizePath $ providerDirectory conf
manager <- FSNotify.startManager
let allowed event = do
-- Absolute path of the changed file. This must be inside provider
-- dir, since that's the only dir we're watching.
let path = FSNotify.eventPath event
relative = dropWhile (`elem` pathSeparators) $
drop (length fullProviderDir) path
identifier = fromFilePath relative
shouldIgnore <- shouldIgnoreFile conf path
return $ not shouldIgnore && matches pattern identifier
-- This thread continually watches the `shouldBuild` MVar and builds
-- whenever a value is present.
_ <- forkIO $ forever $ do
event <- takeMVar shouldBuild
handle
(\e -> case fromException e of
Nothing -> putStrLn (show e)
Just async -> throw (async :: AsyncException))
(update' event providerDir)
-- Send an event whenever something occurs so that the thread described
-- above will do a build.
void $ FSNotify.watchTree manager providerDir (not . isRemove) $ \event -> do
allowed' <- allowed event
when allowed' $ void $ tryPutMVar shouldBuild event
where
#ifndef mingw32_HOST_OS
update' _ _ = void update
#else
update' event provider = do
let path = provider </> FSNotify.eventPath event
-- on windows, a 'Modified' event is also sent on file deletion
fileExists <- doesFileExist path
when fileExists . void $ waitOpen path ReadMode (\_ -> update) 10
-- continuously attempts to open the file in between sleep intervals
-- handler is run only once it is able to open the file
waitOpen :: FilePath -> IOMode -> (Handle -> IO r) -> Integer -> IO r
waitOpen _ _ _ 0 = do
putStrLn "[ERROR] Failed to retrieve modified file for regeneration"
exitFailure
waitOpen path mode handler retries = do
res <- try $ openFile path mode :: IO (Either IOException Handle)
case res of
Left ex -> if isPermissionError ex
then do
threadDelay 100000
waitOpen path mode handler (retries - 1)
else throw ex
Right h -> do
handled <- handler h
hClose h
return handled
#endif
--------------------------------------------------------------------------------
isRemove :: FSNotify.Event -> Bool
isRemove (FSNotify.Removed {}) = True
isRemove _ = False
|
