git-annex-3.20111011: Remote/Web.hs

{- Web remotes.
 -
 - Copyright 2011 Joey Hess <joey@kitenet.net>
 -
 - Licensed under the GNU GPL version 3 or higher.
 -}

module Remote.Web (
	remote,
	setUrl
) where

import Common.Annex
import Types.Remote
import qualified Git
import UUID
import Config
import PresenceLog
import LocationLog
import qualified Utility.Url as Url

type URLString = String

remote :: RemoteType Annex
remote = RemoteType {
	typename = "web",
	enumerate = list,
	generate = gen,
	setup = error "not supported"
}

-- There is only one web remote, and it always exists.
-- (If the web should cease to exist, remove this module and redistribute
-- a new release to the survivors by carrier pigeon.)
list :: Annex [Git.Repo]
list = return [Git.repoRemoteNameSet Git.repoFromUnknown "remote.web.dummy"]

-- Dummy uuid for the whole web. Do not alter.
webUUID :: UUID
webUUID = "00000000-0000-0000-0000-000000000001"

gen :: Git.Repo -> UUID -> Maybe RemoteConfig -> Annex (Remote Annex)
gen r _ _ = 
	return Remote {
		uuid = webUUID,
		cost = expensiveRemoteCost,
		name = Git.repoDescribe r,
		storeKey = uploadKey,
		retrieveKeyFile = downloadKey,
		removeKey = dropKey,
		hasKey = checkKey,
		hasKeyCheap = False,
		config = Nothing,
		repo = r
	}

{- The urls for a key are stored in remote/web/hash/key.log 
 - in the git-annex branch. -}
urlLog :: Key -> FilePath
urlLog key = "remote/web" </> hashDirLower key </> keyFile key ++ ".log"
oldurlLog :: Key -> FilePath
{- A bug used to store the urls elsewhere. -}
oldurlLog key = "remote/web" </> hashDirLower key </> show key ++ ".log"

getUrls :: Key -> Annex [URLString]
getUrls key = do
	us <- currentLog (urlLog key)
	if null us
		then currentLog (oldurlLog key)
		else return us

{- Records a change in an url for a key. -}
setUrl :: Key -> URLString -> LogStatus -> Annex ()
setUrl key url status = do
	g <- gitRepo
	addLog (urlLog key) =<< logNow status url

	-- update location log to indicate that the web has the key, or not
	us <- getUrls key
	logChange g key webUUID (if null us then InfoMissing else InfoPresent)

downloadKey :: Key -> FilePath -> Annex Bool
downloadKey key file = get =<< getUrls key
	where
		get [] = do
			warning "no known url"
			return False
		get urls = anyM (`Url.download` file) urls

uploadKey :: Key -> Annex Bool
uploadKey _ = do
	warning "upload to web not supported"
	return False

dropKey :: Key -> Annex Bool
dropKey _ = do
	warning "removal from web not supported"
	return False

checkKey :: Key -> Annex (Either IOException Bool)
checkKey key = do
	us <- getUrls key
	if null us
		then return $ Right False
		else return . Right =<< checkKey' us
checkKey' :: [URLString] -> Annex Bool
checkKey' [] = return False
checkKey' (u:us) = do
	showAction $ "checking " ++ u
	e <- liftIO $ Url.exists u
	if e then return e else checkKey' us