Urls can now be claimed by remotes. This will allow creating, for example, a external special remote that handles magnet: and *.torrent urls.

27 files changed, 344 insertions, 112 deletions

diff --git a/Annex.hs b/Annex.hs
index a04bfd1bb..82a378f79 100644
--- a/Annex.hs
+++ b/Annex.hs
@@ -63,6 +63,7 @@ import Types.CleanupActions
 import Utility.Quvi (QuviVersion)
 #endif
 import Utility.InodeCache
+import Utility.Url
 
 import "mtl" Control.Monad.Reader
 import Control.Concurrent
@@ -128,6 +129,7 @@ data AnnexState = AnnexState
 	, useragent :: Maybe String
 	, errcounter :: Integer
 	, unusedkeys :: Maybe (S.Set Key)
+	, tempurls :: M.Map Key URLString
 #ifdef WITH_QUVI
 	, quviversion :: Maybe QuviVersion
 #endif
@@ -173,6 +175,7 @@ newState c r = AnnexState
 	, useragent = Nothing
 	, errcounter = 0
 	, unusedkeys = Nothing
+	, tempurls = M.empty
 #ifdef WITH_QUVI
 	, quviversion = Nothing
 #endif
diff --git a/Command/AddUrl.hs b/Command/AddUrl.hs
index 81da67639..76095d6e4 100644
--- a/Command/AddUrl.hs
+++ b/Command/AddUrl.hs
@@ -1,6 +1,6 @@
 {- git-annex command
  -
- - Copyright 2011-2013 Joey Hess <joey@kitenet.net>
+ - Copyright 2011-2014 Joey Hess <joey@kitenet.net>
  -
  - Licensed under the GNU GPL version 3 or higher.
  -}
@@ -19,6 +19,8 @@ import qualified Annex
 import qualified Annex.Queue
 import qualified Annex.Url as Url
 import qualified Backend.URL
+import qualified Remote
+import qualified Types.Remote as Remote
 import Annex.Content
 import Logs.Web
 import Types.Key
@@ -26,6 +28,7 @@ import Types.KeySource
 import Config
 import Annex.Content.Direct
 import Logs.Location
+import Utility.Metered
 import qualified Annex.Transfer as Transfer
 #ifdef WITH_QUVI
 import Annex.Quvi
@@ -54,7 +57,71 @@ seek ps = do
 	withStrings (start relaxed f d) ps
 
 start :: Bool -> Maybe FilePath -> Maybe Int -> String -> CommandStart
-start relaxed optfile pathdepth s = go $ fromMaybe bad $ parseURI s
+start relaxed optfile pathdepth s = do
+	r <- Remote.claimingUrl s
+	if Remote.uuid r == webUUID
+		then startWeb relaxed optfile pathdepth s
+		else startRemote r relaxed optfile pathdepth s
+
+startRemote :: Remote -> Bool -> Maybe FilePath -> Maybe Int -> String -> CommandStart
+startRemote r relaxed optfile pathdepth s = do
+	url <- case Url.parseURIRelaxed s of
+		Nothing -> error $ "bad uri " ++ s
+		Just u -> pure u
+	pathmax <- liftIO $ fileNameLengthLimit "."
+	let file = choosefile $ url2file url pathdepth pathmax
+	showStart "addurl" file
+	showNote $ "using " ++ Remote.name r 
+	next $ performRemote r relaxed s file
+  where
+	choosefile = flip fromMaybe optfile
+
+performRemote :: Remote -> Bool -> URLString -> FilePath -> CommandPerform
+performRemote r relaxed uri file = ifAnnexed file adduri geturi
+  where
+	loguri = setDownloader uri OtherDownloader
+	adduri = addUrlChecked relaxed loguri (Remote.uuid r) checkexistssize
+	checkexistssize key = do
+		res <- tryNonAsync $ Remote.checkUrl r uri
+		case res of
+			Left e -> do
+				warning (show e)
+				return (False, False)
+			Right Nothing ->
+				return (True, True)
+			Right (Just sz) ->
+				return (True, sz == fromMaybe sz (keySize key))
+	geturi = do
+		dummykey <- Backend.URL.fromUrl uri =<<
+			if relaxed
+				then return Nothing
+				else Remote.checkUrl r uri
+		liftIO $ createDirectoryIfMissing True (parentDir file)
+		next $ ifM (Annex.getState Annex.fast <||> pure relaxed)
+			( do
+				res <- tryNonAsync $ Remote.checkUrl r uri
+				case res of
+					Left e -> do
+						warning (show e)
+						return False
+					Right size -> do
+						key <- Backend.URL.fromUrl uri size
+						cleanup (Remote.uuid r) loguri file key Nothing
+						return True
+			, do
+				-- Set temporary url for the dummy key
+				-- so that the remote knows what url it
+				-- should use to download it.
+				setTempUrl dummykey uri
+				let downloader = Remote.retrieveKeyFile r dummykey (Just file)
+				ok <- isJust <$>
+					downloadWith downloader dummykey (Remote.uuid r) loguri file
+				removeTempUrl dummykey
+				return ok
+			)
+
+startWeb :: Bool -> Maybe FilePath -> Maybe Int -> String -> CommandStart
+startWeb relaxed optfile pathdepth s = go $ fromMaybe bad $ parseURI s
   where
 	(s', downloader) = getDownloader s
 	bad = fromMaybe (error $ "bad url " ++ s') $
@@ -62,7 +129,7 @@ start relaxed optfile pathdepth s = go $ fromMaybe bad $ parseURI s
 	choosefile = flip fromMaybe optfile
 	go url = case downloader of
 		QuviDownloader -> usequvi
-		DefaultDownloader -> 
+		_ -> 
 #ifdef WITH_QUVI
 			ifM (quviSupported s')
 				( usequvi
@@ -75,7 +142,7 @@ start relaxed optfile pathdepth s = go $ fromMaybe bad $ parseURI s
 		pathmax <- liftIO $ fileNameLengthLimit "."
 		let file = choosefile $ url2file url pathdepth pathmax
 		showStart "addurl" file
-		next $ perform relaxed s' file
+		next $ performWeb relaxed s' file
 #ifdef WITH_QUVI
 	badquvi = error $ "quvi does not know how to download url " ++ s'
 	usequvi = do
@@ -96,7 +163,9 @@ performQuvi :: Bool -> URLString -> URLString -> FilePath -> CommandPerform
 performQuvi relaxed pageurl videourl file = ifAnnexed file addurl geturl
   where
 	quviurl = setDownloader pageurl QuviDownloader
-	addurl key = next $ cleanup quviurl file key Nothing
+	addurl key = next $ do
+		cleanup webUUID quviurl file key Nothing
+		return True
 	geturl = next $ isJust <$> addUrlFileQuvi relaxed quviurl videourl file
 #endif
 
@@ -106,7 +175,7 @@ addUrlFileQuvi relaxed quviurl videourl file = do
 	key <- Backend.URL.fromUrl quviurl Nothing
 	ifM (pure relaxed <||> Annex.getState Annex.fast)
 		( do
-			cleanup' quviurl file key Nothing
+			cleanup webUUID quviurl file key Nothing
 			return (Just key)
 		, do
 			{- Get the size, and use that to check
@@ -124,55 +193,65 @@ addUrlFileQuvi relaxed quviurl videourl file = do
 						downloadUrl [videourl] tmp
 				if ok
 					then do
-						cleanup' quviurl file key (Just tmp)
+						cleanup webUUID quviurl file key (Just tmp)
 						return (Just key)
 					else return Nothing
 		)
 #endif
 
-perform :: Bool -> URLString -> FilePath -> CommandPerform
-perform relaxed url file = ifAnnexed file addurl geturl
+performWeb :: Bool -> URLString -> FilePath -> CommandPerform
+performWeb relaxed url file = ifAnnexed file addurl geturl
   where
 	geturl = next $ isJust <$> addUrlFile relaxed url file
-	addurl key
-		| relaxed = do
-			setUrlPresent key url
-			next $ return True
-		| otherwise = ifM (elem url <$> getUrls key)
-			( stop
-			, do
-				(exists, samesize) <- Url.withUrlOptions $ Url.check url (keySize key)
-				if exists && samesize
-					then do
-						setUrlPresent key url
-						next $ return True
-					else do
-						warning $ "while adding a new url to an already annexed file, " ++ if exists
-							then "url does not have expected file size (use --relaxed to bypass this check) " ++ url
-							else "failed to verify url exists: " ++ url
-						stop
-			)
+	addurl = addUrlChecked relaxed url webUUID checkexistssize
+	checkexistssize = Url.withUrlOptions . Url.check url . keySize
+
+addUrlChecked :: Bool -> URLString -> UUID -> (Key -> Annex (Bool, Bool)) -> Key -> CommandPerform
+addUrlChecked relaxed url u checkexistssize key
+	| relaxed = do
+		setUrlPresent u key url
+		next $ return True
+	| otherwise = ifM (elem url <$> getUrls key)
+		( stop
+		, do
+			(exists, samesize) <- checkexistssize key
+			if exists && samesize
+				then do
+					setUrlPresent u key url
+					next $ return True
+				else do
+					warning $ "while adding a new url to an already annexed file, " ++ if exists
+						then "url does not have expected file size (use --relaxed to bypass this check) " ++ url
+						else "failed to verify url exists: " ++ url
+					stop
+		)
 
 addUrlFile :: Bool -> URLString -> FilePath -> Annex (Maybe Key)
 addUrlFile relaxed url file = do
 	liftIO $ createDirectoryIfMissing True (parentDir file)
 	ifM (Annex.getState Annex.fast <||> pure relaxed)
 		( nodownload relaxed url file
-		, do
-			showAction $ "downloading " ++ url ++ " "
-			download url file
+		, downloadWeb url file
 		)
 
-download :: URLString -> FilePath -> Annex (Maybe Key)
-download url file = do
-	{- Generate a dummy key to use for this download, before we can
-	 - examine the file and find its real key. This allows resuming
-	 - downloads, as the dummy key for a given url is stable. -}
+downloadWeb :: URLString -> FilePath -> Annex (Maybe Key)
+downloadWeb url file = do
 	dummykey <- addSizeUrlKey url =<< Backend.URL.fromUrl url Nothing
+	let downloader f _ = do
+		showOutput
+		downloadUrl [url] f
+	showAction $ "downloading " ++ url ++ " "
+	downloadWith downloader dummykey webUUID url file
+
+{- The Key should be a dummy key, based on the URL, which is used
+ - for this download, before we can examine the file and find its real key.
+ - For resuming downloads to work, the dummy key for a given url should be
+ - stable. -}
+downloadWith :: (FilePath -> MeterUpdate -> Annex Bool) -> Key -> UUID -> URLString -> FilePath -> Annex (Maybe Key)
+downloadWith downloader dummykey u url file =
 	prepGetViaTmpChecked dummykey Nothing $ do
 		tmp <- fromRepo $ gitAnnexTmpObjectLocation dummykey
-		showOutput
-		ifM (runtransfer dummykey tmp)
+		ifM (runtransfer tmp)
 			( do
 				backend <- chooseBackend file
 				let source = KeySource
@@ -184,15 +263,15 @@ download url file = do
 				case k of
 					Nothing -> return Nothing
 					Just (key, _) -> do
-						cleanup' url file key (Just tmp)
+						cleanup u url file key (Just tmp)
 						return (Just key)
 			, return Nothing
 			)
   where
-	runtransfer dummykey tmp =  Transfer.notifyTransfer Transfer.Download (Just file) $
-		Transfer.download webUUID dummykey (Just file) Transfer.forwardRetry $ const $ do
+	runtransfer tmp =  Transfer.notifyTransfer Transfer.Download (Just file) $
+		Transfer.download webUUID dummykey (Just file) Transfer.forwardRetry $ \p -> do
 			liftIO $ createDirectoryIfMissing True (parentDir tmp)
-			downloadUrl [url] tmp
+			downloader tmp p
 
 {- Hits the url to get the size, if available.
  -
@@ -204,16 +283,11 @@ addSizeUrlKey url key = do
 	size <- snd <$> Url.withUrlOptions (Url.exists url)
 	return $ key { keySize = size }
 
-cleanup :: URLString -> FilePath -> Key -> Maybe FilePath -> Annex Bool
-cleanup url file key mtmp = do
-	cleanup' url file key mtmp
-	return True
-
-cleanup' :: URLString -> FilePath -> Key -> Maybe FilePath -> Annex ()
-cleanup' url file key mtmp = do
+cleanup :: UUID -> URLString -> FilePath -> Key -> Maybe FilePath -> Annex ()
+cleanup u url file key mtmp = do
 	when (isJust mtmp) $
 		logStatus key InfoPresent
-	setUrlPresent key url
+	setUrlPresent u key url
 	Command.Add.addLink file key Nothing
 	whenM isDirect $ do
 		void $ addAssociatedFile key file
@@ -230,7 +304,7 @@ nodownload relaxed url file = do
 	if exists
 		then do
 			key <- Backend.URL.fromUrl url size
-			cleanup' url file key Nothing
+			cleanup webUUID url file key Nothing
 			return (Just key)
 		else do
 			warning $ "unable to access url: " ++ url
@@ -245,8 +319,11 @@ url2file url pathdepth pathmax = case pathdepth of
 		| depth < 0 -> frombits $ reverse . take (negate depth) . reverse
 		| otherwise -> error "bad --pathdepth"
   where
-	fullurl = uriRegName auth ++ uriPath url ++ uriQuery url
+	fullurl = concat
+		[ maybe "" uriRegName (uriAuthority url)
+		, uriPath url
+		, uriQuery url
+		]
 	frombits a = intercalate "/" $ a urlbits
 	urlbits = map (truncateFilePath pathmax . sanitizeFilePath) $
 		filter (not . null) $ split "/" fullurl
-	auth = fromMaybe (error $ "bad url " ++ show url) $ uriAuthority url
diff --git a/Command/ReKey.hs b/Command/ReKey.hs
index a203ab8d5..5dadf4e60 100644
--- a/Command/ReKey.hs
+++ b/Command/ReKey.hs
@@ -16,6 +16,7 @@ import qualified Command.Add
 import Logs.Web
 import Logs.Location
 import Utility.CopyFile
+import qualified Remote
 
 cmd :: [Command]
 cmd = [notDirect $ command "rekey"
@@ -61,8 +62,9 @@ cleanup file oldkey newkey = do
 	-- If the old key had some associated urls, record them for
 	-- the new key as well.
 	urls <- getUrls oldkey
-	unless (null urls) $
-		mapM_ (setUrlPresent newkey) urls
+	forM_ urls $ \url -> do
+		r <- Remote.claimingUrl url
+		setUrlPresent (Remote.uuid r) newkey url
 
 	-- Update symlink to use the new key.
 	liftIO $ removeFile file
diff --git a/Command/RmUrl.hs b/Command/RmUrl.hs
index 1582d0f3f..570004266 100644
--- a/Command/RmUrl.hs
+++ b/Command/RmUrl.hs
@@ -10,6 +10,7 @@ module Command.RmUrl where
 import Common.Annex
 import Command
 import Logs.Web
+import qualified Remote
 
 cmd :: [Command]
 cmd = [notBareRepo $
@@ -26,5 +27,9 @@ start (file, url) = flip whenAnnexed file $ \_ key -> do
 
 cleanup :: String -> Key -> CommandCleanup
 cleanup url key = do
-	setUrlMissing key url
+	r <- Remote.claimingUrl url
+	let url' = if Remote.uuid r == webUUID
+		then url
+		else setDownloader url OtherDownloader
+	setUrlMissing (Remote.uuid r) key url'
 	return True
diff --git a/Command/Whereis.hs b/Command/Whereis.hs
index 582aaffc2..314c204be 100644
--- a/Command/Whereis.hs
+++ b/Command/Whereis.hs
@@ -1,6 +1,6 @@
 {- git-annex command
  -
- - Copyright 2010 Joey Hess <joey@kitenet.net>
+ - Copyright 2010-2014 Joey Hess <joey@kitenet.net>
  -
  - Licensed under the GNU GPL version 3 or higher.
  -}
@@ -13,6 +13,7 @@ import Common.Annex
 import Command
 import Remote
 import Logs.Trust
+import Logs.Web
 
 cmd :: [Command]
 cmd = [noCommit $ withOptions (jsonOption : keyOptions) $
@@ -57,9 +58,17 @@ perform remotemap key = do
 	untrustedheader = "The following untrusted locations may also have copies:\n"
 
 performRemote :: Key -> Remote -> Annex () 
-performRemote key remote = maybe noop go $ whereisKey remote
+performRemote key remote = do
+	ls <- (++)
+		<$> askremote
+		<*> claimedurls
+	unless (null ls) $ showLongNote $ unlines $
+		map (\l -> name remote ++ ": " ++ l) ls
   where
-	go a = do
-		ls <- a key
-		unless (null ls) $ showLongNote $ unlines $
-			map (\l -> name remote ++ ": " ++ l) ls
+	askremote = maybe (pure []) (flip id key) (whereisKey remote)
+	claimedurls = do
+		us <- map fst 
+			. filter (\(_, d) -> d == OtherDownloader)
+			. map getDownloader
+			<$> getUrls key
+		filterM (\u -> (==) <$> pure remote <*> claimingUrl u) us
diff --git a/Logs/Web.hs b/Logs/Web.hs
index 19a3084ef..c3e5c3432 100644
--- a/Logs/Web.hs
+++ b/Logs/Web.hs
@@ -1,6 +1,6 @@
 {- Web url logs.
  -
- - Copyright 2011, 2013 Joey Hess <joey@kitenet.net>
+ - Copyright 2011-2014 Joey Hess <joey@kitenet.net>
  -
  - Licensed under the GNU GPL version 3 or higher.
  -}
@@ -16,12 +16,16 @@ module Logs.Web (
 	Downloader(..),
 	getDownloader,
 	setDownloader,
+	setTempUrl,
+	removeTempUrl,
 ) where
 
 import qualified Data.ByteString.Lazy.Char8 as L
+import qualified Data.Map as M
 import Data.Tuple.Utils
 
 import Common.Annex
+import qualified Annex
 import Logs
 import Logs.Presence
 import Logs.Location
@@ -37,7 +41,10 @@ webUUID = UUID "00000000-0000-0000-0000-000000000001"
 
 {- Gets all urls that a key might be available from. -}
 getUrls :: Key -> Annex [URLString]
-getUrls key = go $ urlLogFile key : oldurlLogs key
+getUrls key = do
+	l <- go $ urlLogFile key : oldurlLogs key
+	tmpl <- Annex.getState (maybeToList . M.lookup key . Annex.tempurls)
+	return (tmpl ++ l)
   where
 	go [] = return []
 	go (l:ls) = do
@@ -49,19 +56,18 @@ getUrls key = go $ urlLogFile key : oldurlLogs key
 getUrlsWithPrefix :: Key -> String -> Annex [URLString]
 getUrlsWithPrefix key prefix = filter (prefix `isPrefixOf`) <$> getUrls key
 
-setUrlPresent :: Key -> URLString -> Annex ()
-setUrlPresent key url = do
+setUrlPresent :: UUID -> Key -> URLString -> Annex ()
+setUrlPresent uuid key url = do
 	us <- getUrls key
 	unless (url `elem` us) $ do
 		addLog (urlLogFile key) =<< logNow InfoPresent url
-		-- update location log to indicate that the web has the key
-		logChange key webUUID InfoPresent
+		logChange key uuid InfoPresent
 
-setUrlMissing :: Key -> URLString -> Annex ()
-setUrlMissing key url = do
+setUrlMissing :: UUID -> Key -> URLString -> Annex ()
+setUrlMissing uuid key url = do
 	addLog (urlLogFile key) =<< logNow InfoMissing url
 	whenM (null <$> getUrls key) $
-		logChange key webUUID InfoMissing
+		logChange key uuid InfoMissing
 
 {- Finds all known urls. -}
 knownUrls :: Annex [URLString]
@@ -81,18 +87,27 @@ knownUrls = do
 	geturls Nothing = return []
 	geturls (Just logsha) = getLog . L.unpack <$> catObject logsha
 
-data Downloader = DefaultDownloader | QuviDownloader
+setTempUrl :: Key -> URLString -> Annex ()
+setTempUrl key url = Annex.changeState $ \s ->
+	s { Annex.tempurls = M.insert key url (Annex.tempurls s) }
+
+removeTempUrl :: Key -> Annex ()
+removeTempUrl key = Annex.changeState $ \s ->
+	s { Annex.tempurls = M.delete key (Annex.tempurls s) }
+
+data Downloader = WebDownloader | QuviDownloader | OtherDownloader
+	deriving (Eq)
+
+{- To keep track of how an url is downloaded, it's mangled slightly in
+ - the log. For quvi, "quvi:" is prefixed. For urls that are handled by
+ - some other remote, ":" is prefixed. -}
+setDownloader :: URLString -> Downloader -> String
+setDownloader u WebDownloader = u
+setDownloader u QuviDownloader = "quvi:" ++ u
+setDownloader u OtherDownloader = ":" ++ u
 
-{- Determines the downloader for an URL.
- -
- - Some URLs are not downloaded by normal means, and this is indicated
- - by prefixing them with downloader: when they are recorded in the url
- - logs. -}
 getDownloader :: URLString -> (URLString, Downloader)
 getDownloader u = case separate (== ':') u of
 	("quvi", u') -> (u', QuviDownloader)
-	_ -> (u, DefaultDownloader)
-
-setDownloader :: URLString -> Downloader -> URLString
-setDownloader u DefaultDownloader = u
-setDownloader u QuviDownloader = "quvi:" ++ u
+	("", u') -> (u', OtherDownloader)
+	_ -> (u, WebDownloader)
diff --git a/Remote.hs b/Remote.hs
index 37dfafa1f..65e725338 100644
--- a/Remote.hs
+++ b/Remote.hs
@@ -45,7 +45,8 @@ module Remote (
 	forceTrust,
 	logStatus,
 	checkAvailable,
-	isXMPPRemote
+	isXMPPRemote,
+	claimingUrl,
 ) where
 
 import qualified Data.Map as M
@@ -60,6 +61,7 @@ import Annex.UUID
 import Logs.UUID
 import Logs.Trust
 import Logs.Location hiding (logStatus)
+import Logs.Web
 import Remote.List
 import Config
 import Git.Types (RemoteName)
@@ -318,3 +320,12 @@ hasKey r k = either (Left  . show) Right <$> tryNonAsync (checkPresent r k)
 
 hasKeyCheap :: Remote -> Bool
 hasKeyCheap = checkPresentCheap
+
+{- The web special remote claims urls by default. -}
+claimingUrl :: URLString -> Annex Remote
+claimingUrl url = do
+	rs <- remoteList
+	let web = Prelude.head $ filter (\r -> uuid r == webUUID) rs
+	fromMaybe web <$> firstM checkclaim rs
+  where
+	checkclaim = maybe (pure False) (flip id url) . claimUrl
diff --git a/Remote/Bup.hs b/Remote/Bup.hs
index 8744aa357..405ce3056 100644
--- a/Remote/Bup.hs
+++ b/Remote/Bup.hs
@@ -75,6 +75,7 @@ gen r u c gc = do
 		, mkUnavailable = return Nothing
 		, getInfo = return [("repo", buprepo)]
 		, claimUrl = Nothing
+		, checkUrl = const $ return Nothing
 		}
 	return $ Just $ specialRemote' specialcfg c
 		(simplyPrepare $ store this buprepo)
diff --git a/Remote/Ddar.hs b/Remote/Ddar.hs
index a57f5f6c3..1b8003dd8 100644
--- a/Remote/Ddar.hs
+++ b/Remote/Ddar.hs
@@ -72,6 +72,7 @@ gen r u c gc = do
 		, mkUnavailable = return Nothing
 		, getInfo = return [("repo", ddarrepo)]
 		, claimUrl = Nothing
+		, checkUrl = const $ return Nothing
 		}
 	ddarrepo = fromMaybe (error "missing ddarrepo") $ remoteAnnexDdarRepo gc
 	specialcfg = (specialRemoteCfg c)
diff --git a/Remote/Directory.hs b/Remote/Directory.hs
index d83ab2dae..fec40baa8 100644
--- a/Remote/Directory.hs
+++ b/Remote/Directory.hs
@@ -69,7 +69,8 @@ gen r u c gc = do
 			mkUnavailable = gen r u c $
 				gc { remoteAnnexDirectory = Just "/dev/null" },
 			getInfo = return [("directory", dir)],
-			claimUrl = Nothing
+			claimUrl = Nothing,
+			checkUrl = const $ return Nothing
 		}
   where
 	dir = fromMaybe (error "missing directory") $ remoteAnnexDirectory gc
diff --git a/Remote/External.hs b/Remote/External.hs
index 97aa247ba..b6928a827 100644
--- a/Remote/External.hs
+++ b/Remote/External.hs
@@ -70,7 +70,8 @@ gen r u c gc = do
 			mkUnavailable = gen r u c $
 				gc { remoteAnnexExternalType = Just "!dne!" },
 			getInfo = return [("externaltype", externaltype)],
-			claimUrl = Just (claimurl external)
+			claimUrl = Just (claimurl external),
+			checkUrl = checkurl external
 		}
   where
 	externaltype = fromMaybe (error "missing externaltype") (remoteAnnexExternalType gc)
@@ -217,8 +218,10 @@ handleRequest' lck external req mp responsehandler
 		state <- fromMaybe ""
 			<$> getRemoteState (externalUUID external) key
 		send $ VALUE state
-	handleRemoteRequest (SETURLPRESENT key url) = setUrlPresent key url
-	handleRemoteRequest (SETURLMISSING key url) = setUrlMissing key url
+	handleRemoteRequest (SETURLPRESENT key url) =
+		setUrlPresent (externalUUID external) key url
+	handleRemoteRequest (SETURLMISSING key url) =
+		setUrlMissing (externalUUID external) key url
 	handleRemoteRequest (GETURLS key prefix) = do
 		mapM_ (send . VALUE) =<< getUrlsWithPrefix key prefix
 		send (VALUE "") -- end of list
@@ -425,3 +428,11 @@ claimurl external url =
 		UNSUPPORTED_REQUEST -> Just $ return False
 		_ -> Nothing
 
+checkurl :: External -> URLString -> Annex (Maybe Integer)
+checkurl external url = 
+	handleRequest external (CHECKURL url) Nothing $ \req -> case req of
+		CHECKURL_SIZE sz -> Just $ return $ Just sz
+		CHECKURL_SIZEUNKNOWN -> Just $ return Nothing
+		CHECKURL_FAILURE errmsg -> Just $ error errmsg
+		UNSUPPORTED_REQUEST -> error "CHECKURL not implemented by external special remote"
+		_ -> Nothing
diff --git a/Remote/External/Types.hs b/Remote/External/Types.hs
index 2fc29e5b4..b00352702 100644
--- a/Remote/External/Types.hs
+++ b/Remote/External/Types.hs
@@ -92,6 +92,7 @@ data Request
 	| GETCOST
 	| GETAVAILABILITY
 	| CLAIMURL URLString
+	| CHECKURL URLString
 	| TRANSFER Direction Key FilePath
 	| CHECKPRESENT Key
 	| REMOVE Key
@@ -109,6 +110,7 @@ instance Proto.Sendable Request where
 	formatMessage GETCOST = ["GETCOST"]
 	formatMessage GETAVAILABILITY = ["GETAVAILABILITY"]
 	formatMessage (CLAIMURL url) = [ "CLAIMURL", Proto.serialize url ]
+	formatMessage (CHECKURL url) = [ "CHECKURL", Proto.serialize url ]
 	formatMessage (TRANSFER direction key file) =
 		[ "TRANSFER"
 		, Proto.serialize direction
@@ -135,6 +137,9 @@ data Response
 	| INITREMOTE_FAILURE ErrorMsg
 	| CLAIMURL_SUCCESS
 	| CLAIMURL_FAILURE
+	| CHECKURL_SIZE Size
+	| CHECKURL_SIZEUNKNOWN
+	| CHECKURL_FAILURE ErrorMsg
 	| UNSUPPORTED_REQUEST
 	deriving (Show)
 
@@ -154,6 +159,9 @@ instance Proto.Receivable Response where
 	parseCommand "INITREMOTE-FAILURE" = Proto.parse1 INITREMOTE_FAILURE
 	parseCommand "CLAIMURL-SUCCESS" = Proto.parse0 CLAIMURL_SUCCESS
 	parseCommand "CLAIMURL-FAILURE" = Proto.parse0 CLAIMURL_FAILURE
+	parseCommand "CHECKURL-SIZE" = Proto.parse1 CHECKURL_SIZE
+	parseCommand "CHECKURL-SIZEUNKNOWN" = Proto.parse0 CHECKURL_SIZEUNKNOWN
+	parseCommand "CHECKURL-FAILURE" = Proto.parse1 CHECKURL_FAILURE
 	parseCommand "UNSUPPORTED-REQUEST" = Proto.parse0 UNSUPPORTED_REQUEST
 	parseCommand _ = Proto.parseFail
 
@@ -225,6 +233,7 @@ instance Proto.Receivable AsyncMessage where
 type ErrorMsg = String
 type Setting = String
 type ProtocolVersion = Int
+type Size = Integer
 
 supportedProtocolVersions :: [ProtocolVersion]
 supportedProtocolVersions = [1]
@@ -253,6 +262,10 @@ instance Proto.Serializable Cost where
 	serialize = show
 	deserialize = readish
 
+instance Proto.Serializable Size where
+	serialize = show
+	deserialize = readish
+
 instance Proto.Serializable Availability where
 	serialize GloballyAvailable = "GLOBAL"
 	serialize LocallyAvailable = "LOCAL"
diff --git a/Remote/GCrypt.hs b/Remote/GCrypt.hs
index 43e3d8b16..6bf99c135 100644
--- a/Remote/GCrypt.hs
+++ b/Remote/GCrypt.hs
@@ -123,6 +123,7 @@ gen' r u c gc = do
 		, mkUnavailable = return Nothing
 		, getInfo = return $ gitRepoInfo r
 		, claimUrl = Nothing
+		, checkUrl = const $ return Nothing
 	}
 	return $ Just $ specialRemote' specialcfg c
 		(simplyPrepare $ store this rsyncopts)
diff --git a/Remote/Git.hs b/Remote/Git.hs
index fdadac2d6..74fb81965 100644
--- a/Remote/Git.hs
+++ b/Remote/Git.hs
@@ -161,6 +161,7 @@ gen r u c gc
 			, mkUnavailable = unavailable r u c gc
 			, getInfo = return $ gitRepoInfo r
 			, claimUrl = Nothing
+			, checkUrl = const $ return Nothing
 			}
 
 unavailable :: Git.Repo -> UUID -> RemoteConfig -> RemoteGitConfig -> Annex (Maybe Remote)
diff --git a/Remote/Glacier.hs b/Remote/Glacier.hs
index 5484a0d2f..17f755000 100644
--- a/Remote/Glacier.hs
+++ b/Remote/Glacier.hs
@@ -69,7 +69,8 @@ gen r u c gc = new <$> remoteCost gc veryExpensiveRemoteCost
 			mkUnavailable = return Nothing,
 			getInfo = includeCredsInfo c (AWS.creds u) $
 				[ ("glacier vault", getVault c) ],
-			claimUrl = Nothing
+			claimUrl = Nothing,
+			checkUrl = const $ return Nothing
 		}
 	specialcfg = (specialRemoteCfg c)
 		-- Disabled until jobList gets support for chunks.
diff --git a/Remote/Hook.hs b/Remote/Hook.hs
index a84ee8554..09297a6e2 100644
--- a/Remote/Hook.hs
+++ b/Remote/Hook.hs
@@ -62,7 +62,8 @@ gen r u c gc = do
 			mkUnavailable = gen r u c $
 				gc { remoteAnnexHookType = Just "!dne!" },
 			getInfo = return [("hooktype", hooktype)],
-			claimUrl = Nothing
+			claimUrl = Nothing,
+			checkUrl = const $ return Nothing
 		}
   where
 	hooktype = fromMaybe (error "missing hooktype") $ remoteAnnexHookType gc
diff --git a/Remote/Rsync.hs b/Remote/Rsync.hs
index 6e71cb2bb..7a7f68165 100644
--- a/Remote/Rsync.hs
+++ b/Remote/Rsync.hs
@@ -85,6 +85,7 @@ gen r u c gc = do
 			, mkUnavailable = return Nothing
 			, getInfo = return [("url", url)]
 			, claimUrl = Nothing
+			, checkUrl = const $ return Nothing
 			}
   where
 	specialcfg = (specialRemoteCfg c)
diff --git a/Remote/S3.hs b/Remote/S3.hs
index 42f4f1ffb..f56904729 100644
--- a/Remote/S3.hs
+++ b/Remote/S3.hs
@@ -93,7 +93,8 @@ gen r u c gc = do
 					else Nothing
 				, Just ("partsize", maybe "unlimited" (roughSize storageUnits False) (getPartSize c))
 				],
-			claimUrl = Nothing
+			claimUrl = Nothing,
+			checkUrl = const $ return Nothing
 		}
 
 s3Setup :: Maybe UUID -> Maybe CredPair -> RemoteConfig -> Annex (RemoteConfig, UUID)
@@ -163,7 +164,7 @@ store r h = fileStorer $ \k f p -> do
 		_ -> singlepartupload k f p	
 	-- Store public URL to item in Internet Archive.
 	when (isIA (hinfo h) && not (isChunkKey k)) $
-		setUrlPresent k (iaKeyUrl r k)
+		setUrlPresent webUUID k (iaKeyUrl r k)
 	return True
   where
 	singlepartupload k f p = do
diff --git a/Remote/Tahoe.hs b/Remote/Tahoe.hs
index 8df590f57..8b56bbd50 100644
--- a/Remote/Tahoe.hs
+++ b/Remote/Tahoe.hs
@@ -86,7 +86,8 @@ gen r u c gc = do
 		remotetype = remote,
 		mkUnavailable = return Nothing,
 		getInfo = return [],
-		claimUrl = Nothing
+		claimUrl = Nothing,
+		checkUrl = const $ return Nothing
 	}
 
 tahoeSetup :: Maybe UUID -> Maybe CredPair -> RemoteConfig -> Annex (RemoteConfig, UUID)
diff --git a/Remote/Web.hs b/Remote/Web.hs
index 6ddf1a45a..3845dddf5 100644
--- a/Remote/Web.hs
+++ b/Remote/Web.hs
@@ -1,4 +1,4 @@
-{- Web remotes.
+{- Web remote.
  -
  - Copyright 2011 Joey Hess <joey@kitenet.net>
  -
@@ -52,7 +52,7 @@ gen r _ c gc =
 		removeKey = dropKey,
 		checkPresent = checkKey,
 		checkPresentCheap = False,
-		whereisKey = Just getUrls,
+		whereisKey = Just getWebUrls,
 		remoteFsck = Nothing,
 		repairRepo = Nothing,
 		config = c,
@@ -64,11 +64,12 @@ gen r _ c gc =
 		remotetype = remote,
 		mkUnavailable = return Nothing,
 		getInfo = return [],
-		claimUrl = Nothing -- implicitly claims all urls
+		claimUrl = Nothing, -- implicitly claims all urls
+		checkUrl = const $ return Nothing
 	}
 
 downloadKey :: Key -> AssociatedFile -> FilePath -> MeterUpdate -> Annex Bool
-downloadKey key _file dest _p = get =<< getUrls key
+downloadKey key _file dest _p = get =<< getWebUrls key
   where
 	get [] = do
 		warning "no known url"
@@ -86,7 +87,7 @@ downloadKey key _file dest _p = get =<< getUrls key
 					warning "quvi support needed for this url"
 					return False
 #endif
-				DefaultDownloader -> downloadUrl [u'] dest
+				_ -> downloadUrl [u'] dest
 
 downloadKeyCheap :: Key -> FilePath -> Annex Bool
 downloadKeyCheap _ _ = return False
@@ -98,12 +99,12 @@ uploadKey _ _ _ = do
 
 dropKey :: Key -> Annex Bool
 dropKey k = do
-	mapM_ (setUrlMissing k) =<< getUrls k
+	mapM_ (setUrlMissing webUUID k) =<< getWebUrls k
 	return True
 
 checkKey :: Key -> Annex Bool
 checkKey key = do
-	us <- getUrls key
+	us <- getWebUrls key
 	if null us
 		then return False
 		else either error return =<< checkKey' key us
@@ -118,7 +119,7 @@ checkKey' key us = firsthit us (Right False) $ \u -> do
 #else
 			return $ Left "quvi support needed for this url"
 #endif
-		DefaultDownloader -> do
+		_ -> do
 			Url.withUrlOptions $ catchMsgIO .
 				Url.checkBoth u' (keySize key)
   where
@@ -128,3 +129,9 @@ checkKey' key us = firsthit us (Right False) $ \u -> do
 		case r of
 			Right _ -> return r
 			Left _ -> firsthit rest r a
+
+getWebUrls :: Key -> Annex [URLString]
+getWebUrls key = filter supported <$> getUrls key
+  where
+	supported u = snd (getDownloader u) 
+		`elem` [WebDownloader, QuviDownloader]
diff --git a/Remote/WebDAV.hs b/Remote/WebDAV.hs
index 6b56acca6..57e1dd785 100644
--- a/Remote/WebDAV.hs
+++ b/Remote/WebDAV.hs
@@ -74,7 +74,8 @@ gen r u c gc = new <$> remoteCost gc expensiveRemoteCost
 			mkUnavailable = gen r u (M.insert "url" "http://!dne!/" c) gc,
 			getInfo = includeCredsInfo c (davCreds u) $
 				[("url", fromMaybe "unknown" (M.lookup "url" c))],
-			claimUrl = Nothing
+			claimUrl = Nothing,
+			checkUrl = const $ return Nothing
 		}
 		chunkconfig = getChunkConfig c
 
diff --git a/Types/Remote.hs b/Types/Remote.hs
index 3f71e1fb4..baa857906 100644
--- a/Types/Remote.hs
+++ b/Types/Remote.hs
@@ -103,7 +103,12 @@ data RemoteA a = Remote {
 	-- Information about the remote, for git annex info to display.
 	getInfo :: a [(String, String)],
 	-- Some remotes can download from an url (or uri).
-	claimUrl :: Maybe (URLString -> a Bool)
+	claimUrl :: Maybe (URLString -> a Bool),
+	-- Checks that the url is accessible, and gets the size of its
+	-- content. Returns Nothing if the url is accessible, but
+	-- its size cannot be determined inexpensively.
+	-- Throws an exception if the url is inaccessible.
+	checkUrl :: URLString -> a (Maybe Integer)
 }
 
 instance Show (RemoteA a) where
diff --git a/debian/changelog b/debian/changelog
index 270d3187f..39f165d6b 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -4,6 +4,9 @@ git-annex (5.20141204) UNRELEASED; urgency=medium
     Thanks, Jon Ander Peñalba.
   * External special remote protocol now includes commands for setting
     and getting the urls associated with a key.
+  * Urls can now be claimed by remotes. This will allow creating,
+    for example, a external special remote that handles magnet: and
+    *.torrent urls.
 
  -- Joey Hess <id@joeyh.name>  Fri, 05 Dec 2014 13:42:08 -0400
 
diff --git a/doc/design/external_special_remote_protocol.mdwn b/doc/design/external_special_remote_protocol.mdwn
index 332cc37b1..6c06fd902 100644
--- a/doc/design/external_special_remote_protocol.mdwn
+++ b/doc/design/external_special_remote_protocol.mdwn
@@ -125,10 +125,16 @@ replying with `UNSUPPORTED-REQUEST` is acceptable.
   If the remote replies with `UNSUPPORTED-REQUEST`, its availability
   is assumed to be global. So, only remotes that are only reachable
   locally need to worry about implementing this.
-* `CLAIMURL Value`  
+* `CLAIMURL Url`  
   Asks the remote if it wishes to claim responsibility for downloading
   an url. If so, the remote should send back an `CLAIMURL-SUCCESS` reply.
   If not, it can send `CLAIMURL-FAILURE`.
+* `CHECKURL Url`  
+  Asks the remote to check if the url's content can currently be downloaded
+  (without downloading it). If the url is not accessible, send
+  `CHECKURL-FAILURE`. If the url is accessible and the size is known,
+  send the size in `CHECKURL-SIZE`. If the url is accessible, but the size
+  is unknown, send `CHECKURL-SIZEUNOWN`.
 
 More optional requests may be added, without changing the protocol version,
 so if an unknown request is seen, reply with `UNSUPPORTED-REQUEST`.
@@ -175,6 +181,14 @@ while it's handling a request.
   Indicates that the CLAIMURL url will be handled by this remote.
 * `CLAIMURL-FAILURE`  
   Indicates that the CLAIMURL url wil not be handled by this remote.
+* `CHECKURL-SIZE Size`  
+  Indicates that the requested url has been verified to exist,
+  and its size is known. The size is in bytes.
+* `CHECKURL-SIZEUNKNOWN`  
+  Indicates that the requested url has been verified to exist,
+  but its size could not be determined.
+* `CHECKURL-FAILURE`  
+  Indicates that the requested url could not be accessed.
 * `UNSUPPORTED-REQUEST`  
   Indicates that the special remote does not know how to handle a request.
 
@@ -255,14 +269,14 @@ in control.
 * `GETSTATE Key`  
   Gets any state that has been stored for the key.  
   (git-annex replies with VALUE followed by the state.)
-* `SETURLPRESENT Key Value`  
+* `SETURLPRESENT Key Url`  
   Records an url (or uri) where the Key can be downloaded from.
-* `SETURLMISSING Key Value`  
+* `SETURLMISSING Key Url`  
   Records that the key can no longer be downloaded from the specified
   url (or uri).
-* `GETURLS Key Value`  
+* `GETURLS Key Prefix`  
   Gets the recorded urls where a Key can be downloaded from.
-  Only urls that start with the Value will be returned. The Value
+  Only urls that start with the Prefix will be returned. The Prefix
   may be empty to get all urls.
   (git-annex replies one or more times with VALUE for each url.
   The final VALUE has an empty value, indicating the end of the url list.)
diff --git a/doc/devblog/day_237__extending_addurl.mdwn b/doc/devblog/day_237__extending_addurl.mdwn
new file mode 100644
index 000000000..e0129398e
--- /dev/null
+++ b/doc/devblog/day_237__extending_addurl.mdwn
@@ -0,0 +1,14 @@
+Worked on [[todo/extensible_addurl]] today. When `git annex addurl` is run,
+remotes will be asked if they claim the url, and whichever remote does will
+be used to download it, and location tracking will indicate that remote
+contains the object. This is a masive 1000 line patch touching 30 files,
+including follow-on changes in `rmurl` and `whereis` and even `rekey`.
+
+It should now be possible to build an external special remote that handles
+*.torrent and magnet: urls and passes them off to a bittorrent client for
+download, for example.
+
+Another use for this would be to make an external special remote that
+uses youtube-dl or some other program than quvi for downloading web videos.
+The builtin quvi support could probably be moved out of the web special
+remote, to a separate remote. I haven't tried to do that yet.
diff --git a/doc/internals.mdwn b/doc/internals.mdwn
index 9970a0bbd..b8cb559b6 100644
--- a/doc/internals.mdwn
+++ b/doc/internals.mdwn
@@ -182,8 +182,9 @@ Example:
 ## `aaa/bbb/*.log.web`
 
 These log files record urls used by the
-[[web_special_remote|special_remotes/web]]. Their format is similar
-to the location tracking files, but with urls rather than UUIDs.
+[[web_special_remote|special_remotes/web]] and sometimes by other remotes.
+Their format is similar to the location tracking files, but with urls
+rather than UUIDs.
 
 ## `aaa/bbb/*.log.rmt`
 
diff --git a/doc/todo/extensible_addurl.mdwn b/doc/todo/extensible_addurl.mdwn
index e9a8d070a..44b19fef0 100644
--- a/doc/todo/extensible_addurl.mdwn
+++ b/doc/todo/extensible_addurl.mdwn
@@ -25,11 +25,40 @@ Solution: Add a new method to remotes:
 	claimUrl :: Maybe (URLString -> Annex Bool)
 
 Remotes that implement this method (including special remotes) will
-be queried when such an uri is added, to see which claims it. Once the
-remote is known, addurl will record that the Key is present on that remote,
-and record the uri in the url log. 
+be queried when such an uri is added, to see which claims it.
 
-Then retrieval of the Key works more or less as usual. The only
+Once the remote is known, addurl --file will record that the Key is present
+on that remote, and record the uri in the url log.
+
+----
+
+What about using addurl to add a new file? In this mode, the Key is not yet
+known. addurl currently handles this by generating a dummy Key for the url
+(hitting the url to get its size), and running a Transfer using the dummy
+key that downloads from the web. Once the download is done, the dummy Key
+is upgraded to the final Key. 
+
+Something similar could be done for other remotes, but the url log for the
+dummy key would need to have the url added to it, for the remote to know
+what to download, and then that could be removed after the download. Which
+causes ugly churn in git, and would leave a mess if interrupted.
+
+One option is to add another new method to remotes:
+
+	downloadUrl :: Maybe (URLString -> Annex FilePath)
+
+Or, the url log could have support added for recording temporary key
+urls in memory. (done)
+
+Another problem is that the size of the Key isn't known. addurl
+could always operate in relaxed mode, where it generates a size-less Key.
+Or, yet another method could be added: (done)
+
+	sizeUrl :: URLString -> Annex (Maybe Integer)
+
+----
+
+Retrieval of the Key works more or less as usual. The only
 difference being that remotes that support this interface can look
 at the url log to find the one with the right "$downloader:" prefix,
 and so know where to download from. (Much as the web special remote already
@@ -55,3 +84,5 @@ This could be implemented in either the web special remote or even in an
 external special remote.
 
 Some other discussion at <https://github.com/datalad/datalad/issues/10>
+
+> [[done]]! --[[Joey]]