add web special remote

Generalized LocationLog to PresenceLog, and use a presence log to record
urls for the web special remote.

LocationLog.hs

@@ -5,11 +5,6 @@
  -
  - Repositories record their UUID and the date when they --get or --drop
  - a value.
- -
- - A line of the log will look like: "date N UUID"
- - Where N=1 when the repo has the file, and 0 otherwise.
- - (After the UUID can optionally come a white space and other data, 
- - for future expansion.)
  - 
  - Copyright 2010-2011 Joey Hess <joey@kitenet.net>
  -
@@ -25,61 +20,16 @@ module LocationLog (
 	loggedKeys
 ) where
 
-import Data.Time.Clock.POSIX
-import Data.Time
-import System.Locale
 import System.FilePath
-import qualified Data.Map as Map
 import Control.Monad (when)
 import Data.Maybe
-import Control.Monad.State (liftIO)
 
 import qualified Git
 import qualified Branch
 import UUID
 import Types
 import Locations
-
-data LogLine = LogLine {
-	date :: POSIXTime,
-	status :: LogStatus,
-	uuid :: UUID
-} deriving (Eq)
-
-data LogStatus = ValuePresent | ValueMissing | Undefined
-	deriving (Eq)
-
-instance Show LogStatus where
-	show ValuePresent = "1"
-	show ValueMissing = "0"
-	show Undefined = "undefined"
-
-instance Read LogStatus where
-	readsPrec _ "1" = [(ValuePresent, "")]
-	readsPrec _ "0" = [(ValueMissing, "")]
-	readsPrec _ _   = [(Undefined, "")]
-
-instance Show LogLine where
-	show (LogLine d s u) = unwords [show d, show s, u]
-
-instance Read LogLine where
-	-- This parser is robust in that even unparsable log lines are
-	-- read without an exception being thrown.
-	-- Such lines have a status of Undefined.
-	readsPrec _ string = 
-		if length w >= 3
-			then maybe bad good pdate
-			else bad
-		where
-			w = words string
-			s = read $ w !! 1
-			u = w !! 2
-			pdate :: Maybe UTCTime
-			pdate = parseTime defaultTimeLocale "%s%Qs" $ head w
-
-			good v = ret $ LogLine (utcTimeToPOSIXSeconds v) s u
-			bad = ret $ LogLine 0 Undefined ""
-			ret v = [(v, "")]
+import PresenceLog
 
 {- Log a change in the presence of a key's value in a repository. -}
 logChange :: Git.Repo -> Key -> UUID -> LogStatus -> Annex ()
@@ -92,59 +42,10 @@ logChange repo key u s = do
 	ls <- readLog f
 	writeLog f (compactLog $ line:ls)
 
-{- Reads a log file.
- - Note that the LogLines returned may be in any order. -}
-readLog :: FilePath -> Annex [LogLine]
-readLog file = return . parseLog =<< Branch.get file
-
-parseLog :: String -> [LogLine]
-parseLog s = filter parsable $ map read $ lines s
-	where
-		-- some lines may be unparseable, avoid them
-		parsable l = status l /= Undefined
-
-{- Stores a set of lines in a log file -}
-writeLog :: FilePath -> [LogLine] -> Annex ()
-writeLog file ls = Branch.change file (unlines $ map show ls)
-
-{- Generates a new LogLine with the current date. -}
-logNow :: LogStatus -> UUID -> Annex LogLine
-logNow s u = do
-	now <- liftIO $ getPOSIXTime
-	return $ LogLine now s u
-
 {- Returns a list of repository UUIDs that, according to the log, have
  - the value of a key. -}
 keyLocations :: Key -> Annex [UUID]
-keyLocations key = do
-	ls <- readLog $ logFile key
-	return $ map uuid $ filterPresent ls
-
-{- Filters the list of LogLines to find ones where the value
- - is (or should still be) present. -}
-filterPresent :: [LogLine] -> [LogLine]
-filterPresent ls = filter (\l -> ValuePresent == status l) $ compactLog ls
-
-type LogMap = Map.Map UUID LogLine
-
-{- Compacts a set of logs, returning a subset that contains the current
- - status. -}
-compactLog :: [LogLine] -> [LogLine]
-compactLog ls = compactLog' Map.empty ls
-compactLog' :: LogMap -> [LogLine] -> [LogLine]
-compactLog' m [] = Map.elems m
-compactLog' m (l:ls) = compactLog' (mapLog m l) ls
-
-{- Inserts a log into a map of logs, if the log has better (ie, newer)
- - information about a repo than the other logs in the map -}
-mapLog :: LogMap -> LogLine -> LogMap
-mapLog m l = 
-	if better
-		then Map.insert u l m
-		else m
-	where
-		better = maybe True (\l' -> date l' <= date l) $ Map.lookup u m
-		u = uuid l
+keyLocations key = currentLog $ logFile key
 
 {- Finds all keys that have location log information.
  - (There may be duplicate keys in the list.) -}