84 lines
2.2 KiB
Haskell
84 lines
2.2 KiB
Haskell
{- git-annex-shell command
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-
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- Copyright 2014 Joey Hess <id@joeyh.name>
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-
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- Licensed under the GNU GPL version 3 or higher.
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-}
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module Command.NotifyChanges where
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import Command
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import Utility.DirWatcher
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import Utility.DirWatcher.Types
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import qualified Git
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import Git.Sha
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import RemoteDaemon.Transport.Ssh.Types
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import Control.Concurrent
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import Control.Concurrent.Async
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import Control.Concurrent.STM
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cmd :: Command
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cmd = noCommit $
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command "notifychanges" SectionPlumbing
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"sends notification when git refs are changed"
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paramNothing (withParams seek)
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seek :: CmdParams -> CommandSeek
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seek = withNothing start
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start :: CommandStart
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start = do
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-- This channel is used to accumulate notifcations,
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-- because the DirWatcher might have multiple threads that find
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-- changes at the same time.
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chan <- liftIO newTChanIO
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g <- gitRepo
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let refdir = Git.localGitDir g </> "refs"
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liftIO $ createDirectoryIfMissing True refdir
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let notifyhook = Just $ notifyHook chan
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let hooks = mkWatchHooks
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{ addHook = notifyhook
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, modifyHook = notifyhook
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}
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void $ liftIO $ watchDir refdir (const False) True hooks id
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let sender = do
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send READY
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forever $ send . CHANGED =<< drain chan
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-- No messages need to be received from the caller,
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-- but when it closes the connection, notice and terminate.
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let receiver = forever $ void getLine
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void $ liftIO $ concurrently sender receiver
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stop
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notifyHook :: TChan Git.Sha -> FilePath -> Maybe FileStatus -> IO ()
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notifyHook chan reffile _
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| ".lock" `isSuffixOf` reffile = noop
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| otherwise = void $ do
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sha <- catchDefaultIO Nothing $
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extractSha <$> readFile reffile
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maybe noop (atomically . writeTChan chan) sha
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-- When possible, coalesce ref writes that occur closely together
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-- in time. Delay up to 0.05 seconds to get more ref writes.
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drain :: TChan Git.Sha -> IO [Git.Sha]
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drain chan = do
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r <- atomically $ readTChan chan
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threadDelay 50000
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rs <- atomically $ drain' chan
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return (r:rs)
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drain' :: TChan Git.Sha -> STM [Git.Sha]
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drain' chan = loop []
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where
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loop rs = maybe (return rs) (\r -> loop (r:rs)) =<< tryReadTChan chan
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send :: Notification -> IO ()
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send n = do
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putStrLn $ unwords $ formatMessage n
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hFlush stdout
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