Introduce pandoc timeouts

Sometimes pandoc takes unreasonably long time to parse a
document (though it warns about that in the documentation), so a
safeguard is needed.

2 files changed, 7 insertions, 1 deletions

diff --git a/Pancake/Configuration.hs b/Pancake/Configuration.hs
index 9df236a..9b0f83d 100644
--- a/Pancake/Configuration.hs
+++ b/Pancake/Configuration.hs
@@ -69,6 +69,9 @@ data Config = Config { commands :: M.Map String String
                      -- inside divs.
                      , unclutter :: M.Map String String
                      -- ^ XSLT file and URI regex.
+                     , pandocTimeout :: Int
+                     -- ^ Maximum amount of time (in seconds) allowed
+                     -- for document parsing.
                      } deriving (Generic, Show, Eq)
 
 -- | For configuration parsing.
@@ -117,6 +120,7 @@ instance Default Config where
          "^https://news\\.ycombinator\\.com/((news|show|ask).*)?$")
       , ("mediawiki", "^https://en\\.(m.)?(wiktionary|wikipedia)\\.org/wiki/")
       , ("github", "^https://github\\.com/")]
+    , pandocTimeout = 60
     }
     where
       curl = "curl -A \"pancake/${PANCAKE}\" --compressed -4 -L " ++
diff --git a/Pancake/Reading.hs b/Pancake/Reading.hs
index 7d86219..3a83e46 100644
--- a/Pancake/Reading.hs
+++ b/Pancake/Reading.hs
@@ -54,6 +54,7 @@ import qualified Data.Map as M
 import Control.Monad.IO.Class
 import System.Directory
 import Control.Concurrent.STM.TVar
+import System.Timeout
 
 import Text.Pandoc.Readers.Plain
 import Text.Pandoc.Readers.Gopher
@@ -237,13 +238,14 @@ readDoc c rdfc out dt uri = do
         (parse pEmacsMode (uriToString id uri "") out)
       cols = fromMaybe 80 $ getCapability term termColumns
       opts = def { P.readerColumns = cols, P.readerExtensions = exts }
-  liftIO $ case reader of
+  r <- liftIO $ timeout (pandocTimeout c * 1000000) $ case reader of
     P.TextReader f -> case decodeUtf8' out of
       Left err -> do
         putErrLn $ show err
         P.runIO $ f opts $ decodeLatin1 out
       Right r -> P.runIO $ f opts r
     P.ByteStringReader f -> P.runIO $ f opts $ BL.fromStrict out
+  pure $ fromMaybe (Left (P.PandocSomeError "Timed out.")) r
   where
     http ext = byExtension' ext <|> html
     html = P.getReader "html"