{- git-annex command
 -
 - Copyright 2010-2016 Joey Hess <id@joeyh.name>
 -
 - Licensed under the GNU GPL version 3 or higher.
 -}

{-# LANGUAGE BangPatterns #-}

module Command.Unused where

import qualified Data.Map as M

import Command
import Logs.Unused
import Annex.Content
import Logs.Location
import qualified Annex
import qualified Git
import qualified Git.Command
import qualified Git.Ref
import qualified Git.Branch
import qualified Git.RefLog
import qualified Git.LsFiles as LsFiles
import qualified Git.DiffTree as DiffTree
import qualified Remote
import qualified Annex.Branch
import Annex.Link
import Annex.CatFile
import Annex.WorkTree
import Types.RefSpec
import Git.Types
import Git.Sha
import Git.FilePath
import Logs.View (is_branchView)
import Annex.BloomFilter
import qualified Database.Keys
import Annex.InodeSentinal

cmd :: Command
cmd = command "unused" SectionMaintenance "look for unused file content"
	paramNothing (seek <$$> optParser)

data UnusedOptions = UnusedOptions
	{ fromRemote :: Maybe RemoteName
	, refSpecOption :: Maybe RefSpec
	}

optParser :: CmdParamsDesc -> Parser UnusedOptions
optParser _ = UnusedOptions
	<$> optional (strOption
		( long "from" <> short 'f' <> metavar paramRemote
		<> help "remote to check for unused content"
		))
	<*> optional (option (eitherReader parseRefSpec)
		( long "used-refspec" <> metavar paramRefSpec
		<> help "refs to consider used (default: all branches)"
		))

seek :: UnusedOptions -> CommandSeek
seek = commandAction . start

start :: UnusedOptions -> CommandStart
start o = do
	cfgrefspec <- fromMaybe allRefSpec . annexUsedRefSpec
		<$> Annex.getGitConfig
	let refspec = fromMaybe cfgrefspec (refSpecOption o)
	let (name, perform) = case fromRemote o of
		Nothing -> (".", checkUnused refspec)
		Just "." -> (".", checkUnused refspec)
		Just "here" -> (".", checkUnused refspec)
		Just n -> (n, checkRemoteUnused n refspec)
	showStart "unused" name
	next perform

checkUnused :: RefSpec -> CommandPerform
checkUnused refspec = chain 0
	[ check "" unusedMsg $ findunused =<< Annex.getState Annex.fast
	, check "bad" staleBadMsg $ staleKeysPrune gitAnnexBadDir False
	, check "tmp" staleTmpMsg $ staleKeysPrune gitAnnexTmpObjectDir True
	]
  where
	findunused True = do
		showNote "fast mode enabled; only finding stale files"
		return []
	findunused False = do
		showAction "checking for unused data"
		-- InAnnex, not InRepository because if a direct mode
		-- file exists, it is obviously not unused.
		excludeReferenced refspec =<< getKeysPresent InAnnex
	chain _ [] = next $ return True
	chain v (a:as) = do
		v' <- a v
		chain v' as

checkRemoteUnused :: String -> RefSpec -> CommandPerform
checkRemoteUnused name refspec = go =<< fromJust <$> Remote.byNameWithUUID (Just name)
  where
	go r = do
		showAction "checking for unused data"
		_ <- check "" (remoteUnusedMsg r) (remoteunused r) 0
		next $ return True
	remoteunused r = excludeReferenced refspec <=< loggedKeysFor $ Remote.uuid r

check :: FilePath -> ([(Int, Key)] -> String) -> Annex [Key] -> Int -> Annex Int
check file msg a c = do
	l <- a
	let unusedlist = number c l
	unless (null l) $ showLongNote $ msg unusedlist
	updateUnusedLog file $ M.fromList unusedlist
	return $ c + length l

number :: Int -> [a] -> [(Int, a)]
number _ [] = []
number n (x:xs) = (n+1, x) : number (n+1) xs

table :: [(Int, Key)] -> [String]
table l = "  NUMBER  KEY" : map cols l
  where
	cols (n,k) = "  " ++ pad 6 (show n) ++ "  " ++ key2file k
	pad n s = s ++ replicate (n - length s) ' '

staleTmpMsg :: [(Int, Key)] -> String
staleTmpMsg t = unlines $ 
	["Some partially transferred data exists in temporary files:"]
	++ table t ++ [dropMsg Nothing]

staleBadMsg :: [(Int, Key)] -> String
staleBadMsg t = unlines $ 
	["Some corrupted files have been preserved by fsck, just in case:"]
	++ table t ++ [dropMsg Nothing]

unusedMsg :: [(Int, Key)] -> String
unusedMsg u = unusedMsg' u
	["Some annexed data is no longer used by any files:"]
	[dropMsg Nothing]
unusedMsg' :: [(Int, Key)] -> [String] -> [String] -> String
unusedMsg' u mheader mtrailer = unlines $
	mheader ++
	table u ++
	["(To see where data was previously used, try: git log --stat -S'KEY')"] ++
	mtrailer

remoteUnusedMsg :: Remote -> [(Int, Key)] -> String
remoteUnusedMsg r u = unusedMsg' u
	["Some annexed data on " ++ name ++ " is not used by any files:"]
	[dropMsg $ Just r]
  where
	name = Remote.name r 

dropMsg :: Maybe Remote -> String
dropMsg Nothing = dropMsg' ""
dropMsg (Just r) = dropMsg' $ " --from " ++ Remote.name r
dropMsg' :: String -> String
dropMsg' s = "\nTo remove unwanted data: git-annex dropunused" ++ s ++ " NUMBER\n"

{- Finds keys in the list that are not referenced in the git repository.
 -
 - Strategy:
 -
 - Pass keys through these filters in order, only creating each bloom
 - filter on demand if the previous one didn't filter out all keys.
 -
 - 1. Bloom filter containing all keys referenced by files in the work tree.
 -    This is the fastest one to build and will filter out most keys.
 - 2. Bloom filter containing all keys in the diff from the work tree to
 -    the index.
 - 3. Associated files filter. A v6 unlocked file may have had its content
 -    added to the annex (by eg, git diff running the smudge filter),
 -    but the new key is not yet staged in the index. But if so, it will 
 -    have an associated file.
 - 4. Bloom filter containing all keys in the diffs between the index and
 -    branches matching the RefSpec. (This can take quite a while to build).
 -}
excludeReferenced :: RefSpec -> [Key] -> Annex [Key]
excludeReferenced refspec ks = runbloomfilter withKeysReferencedM ks
	>>= runbloomfilter withKeysReferencedDiffIndex
	>>= runfilter associatedFilesFilter
	>>= runbloomfilter (withKeysReferencedDiffGitRefs refspec)
  where
	runfilter _ [] = return [] -- optimisation
	runfilter a l = a l
	runbloomfilter a = runfilter $ \l -> bloomFilter l <$> genBloomFilter a

{- Given an initial value, folds it with each key referenced by
 - files in the working tree. -}
withKeysReferenced :: v -> (Key -> v -> v) -> Annex v
withKeysReferenced initial a = withKeysReferenced' Nothing initial folda
  where
	folda k _ v = return $ a k v

{- Runs an action on each referenced key in the working tree. -}
withKeysReferencedM :: (Key -> Annex ()) -> Annex ()
withKeysReferencedM a = withKeysReferenced' Nothing () calla
  where
	calla k _ _ = a k

{- Folds an action over keys and files referenced in a particular directory. -}
withKeysFilesReferencedIn :: FilePath -> v -> (Key -> FilePath -> v -> Annex v) -> Annex v
withKeysFilesReferencedIn = withKeysReferenced' . Just

withKeysReferenced' :: Maybe FilePath -> v -> (Key -> FilePath -> v -> Annex v) -> Annex v
withKeysReferenced' mdir initial a = do
	(files, clean) <- getfiles
	r <- go initial files
	liftIO $ void clean
	return r
  where
	getfiles = case mdir of
		Nothing -> ifM isBareRepo
			( return ([], return True)
			, do
				top <- fromRepo Git.repoPath
				inRepo $ LsFiles.allFiles [top]
			)
		Just dir -> inRepo $ LsFiles.inRepo [dir]
	go v [] = return v
	go v (f:fs) = do
		mk <- lookupFile f
		case mk of
			Nothing -> go v fs
			Just k -> do
				!v' <- a k f v
				go v' fs

withKeysReferencedDiffGitRefs :: RefSpec -> (Key -> Annex ()) -> Annex ()
withKeysReferencedDiffGitRefs refspec a = do
	rs <- relevantrefs <$> inRepo (Git.Command.pipeReadStrict [Param "show-ref"])
	shaHead <- maybe (return Nothing) (inRepo . Git.Ref.sha)
		=<< inRepo Git.Branch.currentUnsafe
	let haveHead = any (\(shaRef, _) -> Just shaRef == shaHead) rs
	let rs' = map snd (nubRefs rs)
	usedrefs <- applyRefSpec refspec rs' (getreflog rs')
	forM_ (if haveHead then usedrefs else Git.Ref.headRef : usedrefs) $
		withKeysReferencedDiffGitRef a
  where
	relevantrefs = map (\(r, h) -> (Git.Ref r, Git.Ref h)) .
		filter ourbranches .
		map (separate (== ' ')) .
		lines
	nubRefs = nubBy (\(x, _) (y, _) -> x == y)
	ourbranchend = '/' : Git.fromRef Annex.Branch.name
	ourbranches (_, b) = not (ourbranchend `isSuffixOf` b)
		&& not ("refs/synced/" `isPrefixOf` b)
		&& not (is_branchView (Git.Ref b))
	getreflog rs = inRepo $ Git.RefLog.getMulti rs

{- Runs an action on keys referenced in the given Git reference which
 - differ from those referenced in the index. -}
withKeysReferencedDiffGitRef :: (Key -> Annex ()) -> Git.Ref -> Annex ()
withKeysReferencedDiffGitRef a ref = do
	showAction $ "checking " ++ Git.Ref.describe ref
	withKeysReferencedDiff a
		(inRepo $ DiffTree.diffIndex ref)
		DiffTree.srcsha

{- Runs an action on keys referenced in the index which differ from the
 - work tree. -}
withKeysReferencedDiffIndex :: (Key -> Annex ()) -> Annex ()
withKeysReferencedDiffIndex a = unlessM (isBareRepo) $
	withKeysReferencedDiff a
		(inRepo $ DiffTree.diffFiles [])
		DiffTree.srcsha

withKeysReferencedDiff :: (Key -> Annex ()) -> (Annex ([DiffTree.DiffTreeItem], IO Bool)) -> (DiffTree.DiffTreeItem -> Sha) -> Annex ()
withKeysReferencedDiff a getdiff extractsha = do
	(ds, clean) <- getdiff
	forM_ ds go
	liftIO $ void clean
  where
	go d = do
		let sha = extractsha d
		unless (sha == nullSha) $
			(parseLinkOrPointer <$> catObject sha)
				>>= maybe noop a

{- Filters out keys that have an associated file that's not modified. -}
associatedFilesFilter :: [Key] -> Annex [Key]
associatedFilesFilter = filterM go
  where
	go k = do
		cs <- Database.Keys.getInodeCaches k
		if null cs
			then return True
			else checkunmodified cs
				=<< Database.Keys.getAssociatedFiles k
	checkunmodified _ [] = return True
	checkunmodified cs (f:fs) = do
		relf <- fromRepo $ fromTopFilePath f
		ifM (sameInodeCache relf cs)
			( return False
			, checkunmodified cs fs
			)

data UnusedMaps = UnusedMaps
	{ unusedMap :: UnusedMap
	, unusedBadMap :: UnusedMap
	, unusedTmpMap :: UnusedMap
	}

withUnusedMaps :: (UnusedMaps -> Int -> CommandStart) -> CmdParams -> CommandSeek
withUnusedMaps a params = do
	unused <- readUnusedMap ""
	unusedbad <- readUnusedMap "bad"
	unusedtmp <- readUnusedMap "tmp"
	let m = unused `M.union` unusedbad `M.union` unusedtmp
	let unusedmaps = UnusedMaps unused unusedbad unusedtmp
	seekActions $ return $ map (a unusedmaps) $
		concatMap (unusedSpec m) params

unusedSpec :: UnusedMap -> String -> [Int]
unusedSpec m spec
	| spec == "all" = if M.null m
		then []
		else [fst (M.findMin m)..fst (M.findMax m)]
	| "-" `isInfixOf` spec = range $ separate (== '-') spec
	| otherwise = maybe badspec (: []) (readish spec)
  where
	range (a, b) = case (readish a, readish b) of
		(Just x, Just y) -> [x..y]
		_ -> badspec
	badspec = error $ "Expected number or range, not \"" ++ spec ++ "\""

{- Seek action for unused content. Finds the number in the maps, and
 - calls one of 3 actions, depending on the type of unused file. -}
startUnused :: String
	-> (Key -> CommandPerform)
	-> (Key -> CommandPerform) 
	-> (Key -> CommandPerform)
	-> UnusedMaps -> Int -> CommandStart
startUnused message unused badunused tmpunused maps n = search
	[ (unusedMap maps, unused)
	, (unusedBadMap maps, badunused)
	, (unusedTmpMap maps, tmpunused)
	]
  where
	search [] = error $ show n ++ " not valid (run git annex unused for list)"
	search ((m, a):rest) =
		case M.lookup n m of
			Nothing -> search rest
			Just key -> do
				showStart message (show n)
				next $ a key
