84 lines
3.0 KiB
Haskell
84 lines
3.0 KiB
Haskell
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module Language.Haskell.GhcMod.Caching where
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import Control.Monad.Trans.Maybe
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import Data.Maybe
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import Data.Serialize
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import qualified Data.ByteString as BS
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import System.FilePath
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import Language.Haskell.GhcMod.Monad.Types
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import Language.Haskell.GhcMod.Logging
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import Utils
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data Cached m d a =
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Cached { cacheFile :: FilePath,
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cachedAction :: TimedCacheFiles -> d -> m ([FilePath], a)
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-- ^ The cached action, will only run if
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-- * The cache doesn\'t exist yet
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-- * The cache exists and 'inputData' changed
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-- * any files in 'inputFiles' are older than 'cacheFile'.
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}
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data TimedCacheFiles =
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TimedCacheFiles { tcCacheFile :: Maybe TimedFile,
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tcFiles :: [TimedFile]
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}
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-- | Cache a MonadIO action with proper invalidation.
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cached :: forall m a d. (MonadIO m, GmLog m, Serialize a, Eq d, Serialize d)
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=> FilePath -- ^ Directory to prepend to 'cacheFile'
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-> Cached m d a -- ^ Cache descriptor
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-> d
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-> m a
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cached dir cd d = do
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mcc <- readCache
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tcfile <- liftIO $ timeMaybe (cacheFile cd)
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let defTcf = TimedCacheFiles tcfile []
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case mcc of
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Nothing -> writeCache defTcf "cache missing"
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Just (ifs, d', _) | d /= d' -> do
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tcf <- timeCacheInput dir (cacheFile cd) ifs
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writeCache tcf "input data changed"
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Just (ifs, _, a) -> do
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tcf <- timeCacheInput dir (cacheFile cd) ifs
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let invifs = invalidatingInputFiles tcf
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case invifs of
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Nothing -> writeCache tcf "cache missing, existed a sec ago WTF?"
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Just [] -> return a
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Just _ -> writeCache tcf "input files changed"
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where
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writeCache tcf cause = do
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(ifs', a) <- (cachedAction cd) tcf d
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gmLog GmDebug "" $ (text "regenerating cache") <+>: text (cacheFile cd)
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<+> parens (text cause)
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liftIO $ BS.writeFile (dir </> cacheFile cd) $ encode (ifs', d, a)
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return a
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readCache :: m (Maybe ([FilePath], d, a))
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readCache = runMaybeT $ do
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f <- MaybeT $ liftIO $ mightExist $ cacheFile cd
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MaybeT $ readCache' f
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where
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readCache' f = do
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gmLog GmDebug "" $ (text "reading cache") <+>: text (cacheFile cd)
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cc <- liftIO $ BS.readFile f
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return $ either (const Nothing) Just $ decode cc
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timeCacheInput :: MonadIO m => FilePath -> FilePath -> [FilePath] -> m TimedCacheFiles
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timeCacheInput dir cfile ifs = liftIO $ do
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-- TODO: is checking the times this way around race free?
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ins <- (timeMaybe . (dir </>)) `mapM` ifs
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mtcfile <- timeMaybe cfile
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return $ TimedCacheFiles mtcfile (catMaybes ins)
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invalidatingInputFiles :: TimedCacheFiles -> Maybe [FilePath]
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invalidatingInputFiles tcf =
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case tcCacheFile tcf of
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Nothing -> Nothing
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Just tcfile -> Just $ map tfPath $
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-- get input files older than tcfile
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filter (tcfile<) $ tcFiles tcf
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