{- git-annex command
 -
 - Copyright 2010 Joey Hess <joey@kitenet.net>
 -
 - Licensed under the GNU GPL version 3 or higher.
 -}

module Command.Drop where

import Common.Annex
import Command
import qualified Remote
import qualified Annex
import Annex.UUID
import Logs.Location
import Logs.Trust
import Annex.Content
import Config
import qualified Option
import Git.FilePath
import Logs.PreferredContent

import qualified Data.Set as S

def :: [Command]
def = [withOptions [fromOption] $ command "drop" paramPaths seek
	"indicate content of files not currently wanted"]

fromOption :: Option
fromOption = Option.field ['f'] "from" paramRemote "drop content from a remote"

seek :: [CommandSeek]
seek = [withField fromOption Remote.byName $ \from ->
	withFilesInGit $ whenAnnexed $ start from]

start :: Maybe Remote -> FilePath -> (Key, Backend) -> CommandStart
start from file (key, _) = shouldDrop $ \numcopies ->
	case from of
		Nothing -> startLocal file numcopies key
		Just remote -> do
			u <- getUUID
			if Remote.uuid remote == u
				then startLocal file numcopies key
				else startRemote file numcopies key remote
	where
		{- In --auto mode, drop if there are enough copies,
		 - and the repository being dropped from doesn't prefer
		 - to keep the content. -}
		shouldDrop a = autoCopiesWith file key (>) $ \numcopies ->
			ifM (Annex.getState Annex.auto)
				( do
					fp <- inRepo $ toTopFilePath file
					u <- maybe getUUID (return . Remote.uuid) from
					ifM (isPreferredContent (Just u) (S.singleton u) fp)
						( a numcopies, stop )
				, a numcopies
				)

startLocal :: FilePath -> Maybe Int -> Key -> CommandStart
startLocal file numcopies key = stopUnless (inAnnex key) $ do
	showStart "drop" file
	next $ performLocal key numcopies

startRemote :: FilePath -> Maybe Int -> Key -> Remote -> CommandStart
startRemote file numcopies key remote = do
	showStart "drop" file
	next $ performRemote key numcopies remote

performLocal :: Key -> Maybe Int -> CommandPerform
performLocal key numcopies = lockContent key $ do
	(remotes, trusteduuids) <- Remote.keyPossibilitiesTrusted key
	untrusteduuids <- trustGet UnTrusted
	let tocheck = Remote.remotesWithoutUUID remotes (trusteduuids++untrusteduuids)
	stopUnless (canDropKey key numcopies trusteduuids tocheck []) $ do
		whenM (inAnnex key) $ removeAnnex key
		next $ cleanupLocal key

performRemote :: Key -> Maybe Int -> Remote -> CommandPerform
performRemote key numcopies remote = lockContent key $ do
	-- Filter the remote it's being dropped from out of the lists of
	-- places assumed to have the key, and places to check.
	-- When the local repo has the key, that's one additional copy.
	(remotes, trusteduuids) <- Remote.keyPossibilitiesTrusted key
	present <- inAnnex key
	u <- getUUID
	let have = filter (/= uuid) $
		if present then u:trusteduuids else trusteduuids
	untrusteduuids <- trustGet UnTrusted
	let tocheck = filter (/= remote) $
		Remote.remotesWithoutUUID remotes (have++untrusteduuids)
	stopUnless (canDropKey key numcopies have tocheck [uuid]) $ do
		ok <- Remote.removeKey remote key
		next $ cleanupRemote key remote ok
	where
		uuid = Remote.uuid remote

cleanupLocal :: Key -> CommandCleanup
cleanupLocal key = do
	logStatus key InfoMissing
	return True

cleanupRemote :: Key -> Remote -> Bool -> CommandCleanup
cleanupRemote key remote ok = do
	-- better safe than sorry: assume the remote dropped the key
	-- even if it seemed to fail; the failure could have occurred
	-- after it really dropped it
	Remote.logStatus remote key InfoMissing
	return ok

{- Checks specified remotes to verify that enough copies of a key exist to
 - allow it to be safely removed (with no data loss). Can be provided with
 - some locations where the key is known/assumed to be present. -}
canDropKey :: Key -> Maybe Int -> [UUID] -> [Remote] -> [UUID] -> Annex Bool
canDropKey key numcopiesM have check skip = do
	force <- Annex.getState Annex.force
	if force || numcopiesM == Just 0
		then return True
		else do
			need <- getNumCopies numcopiesM
			findCopies key need skip have check

findCopies :: Key -> Int -> [UUID] -> [UUID] -> [Remote] -> Annex Bool
findCopies key need skip = helper []
	where
		helper bad have []
			| length have >= need = return True
			| otherwise = notEnoughCopies key need have skip bad
		helper bad have (r:rs)
			| length have >= need = return True
			| otherwise = do
				let u = Remote.uuid r
				let duplicate = u `elem` have
				haskey <- Remote.hasKey r key
				case (duplicate, haskey) of
					(False, Right True) -> helper bad (u:have) rs
					(False, Left _)     -> helper (r:bad) have rs
					_                   -> helper bad have rs

notEnoughCopies :: Key -> Int -> [UUID] -> [UUID] -> [Remote] -> Annex Bool
notEnoughCopies key need have skip bad = do
	unsafe
	showLongNote $
		"Could only verify the existence of " ++
		show (length have) ++ " out of " ++ show need ++ 
		" necessary copies"
	Remote.showTriedRemotes bad
	Remote.showLocations key (have++skip)
	hint
	return False
	where
		unsafe = showNote "unsafe"
		hint = showLongNote "(Use --force to override this check, or adjust annex.numcopies.)"