do not require a torrent file as argument when WatchDir is set.

src/Combinatorrent.hs

@@ -6,6 +6,7 @@ import Control.Concurrent.STM
 import Control.Monad
 import Control.Monad.State
 
+import Data.Maybe
 import Data.List
 
 import System.Environment
@@ -51,6 +52,17 @@ options =
   , Option ['S']            ["statfile"] (ReqArg StatFile "FILE") "Choose a file to gather stats into"
   ]
 
+(~=) :: Flag -> Flag -> Bool
+Version ~= Version = True
+Debug ~= Debug = True
+LogFile _ ~= LogFile _ = True
+WatchDir _ ~= WatchDir _ = True
+StatFile _ ~= StatFile _ = True
+_ ~= _ = False
+
+flag :: Flag -> [Flag] -> Maybe Flag
+flag x = find (x ~=)
+
 progOpts :: [String] -> IO ([Flag], [String])
 progOpts args = do
     case getOpt Permute options args of
@@ -63,7 +75,7 @@ run (flags, files) = do
     if Version `elem` flags
         then progHeader
         else case files of
-                [] -> putStrLn "No torrentfile input"
+                [] | isNothing $ flag (WatchDir "") flags -> putStrLn "No torrentfile input"
                 names -> progHeader >> download flags names
 
 progHeader :: IO ()
@@ -72,20 +84,17 @@ progHeader = putStrLn $ "This is Combinatorrent \x2620 version " ++ version ++ "
 
 setupLogging :: [Flag] -> IO ()
 setupLogging flags = do
-    fLog <- case logFlag flags of
+    fLog <- case flag (LogFile "") flags of
                 Nothing -> streamHandler SIO.stdout DEBUG
                 Just (LogFile fp) -> fileHandler fp DEBUG
                 Just _ -> error "Impossible match"
     when (Debug `elem` flags)
           (updateGlobalLogger rootLoggerName
                  (setHandlers [fLog] . (setLevel DEBUG)))
-  where logFlag = find (\e -> case e of
-                                LogFile _ -> True
-                                _         -> False)
 
 setupDirWatching :: [Flag] -> TorrentManager.TorrentMgrChan -> IO [Child]
 setupDirWatching flags watchC = do
-    case dirWatchFlag flags of
+    case flag (WatchDir "") flags of
         Nothing -> return []
         Just (WatchDir dir) -> do
             ex <- doesDirectoryExist dir
@@ -94,19 +103,13 @@ setupDirWatching flags watchC = do
                 else do putStrLn $ "Directory does not exist, not watching"
                         return []
         Just _ -> error "Impossible match"
-  where dirWatchFlag = find (\e -> case e of
-                                    WatchDir _ -> True
-                                    _          -> False)
 
 setupStatus :: [Flag] -> Status.StatusChannel -> TVar [Status.PStat] -> Child
 setupStatus flags statusC stv =
-    case statFileFlag flags of
+    case flag (StatFile "") flags of
       Nothing -> Worker $ Status.start Nothing statusC stv
       Just (StatFile fn) -> Worker $ Status.start (Just fn) statusC stv
       Just _ -> error "Impossible match"
-  where statFileFlag = find (\e -> case e of
-                                    StatFile _ -> True
-                                    _          -> False)
 
 generatePeerId :: IO PeerId
 generatePeerId = do