    {-# LANGUAGE FlexibleContexts, GADTs, DeriveDataTypeable #-}

    module Propellor.Property.Chroot (
    	debootstrapped,
    	bootstrapped,
    	provisioned,
    	hostChroot,
    	Chroot(..),
    	ChrootBootstrapper(..),
    	Debootstrapped(..),
    	ChrootTarball(..),
    	inChroot,
    	exposeTrueLocaldir,
    	-- * Internal use
    	provisioned',
    	propagateChrootInfo,
    	propellChroot,
    	chain,
    	chrootSystem,
    ) where

    import Propellor.Base
    import Propellor.Container
    import Propellor.Types.CmdLine
    import Propellor.Types.Chroot
    import Propellor.Types.Info
    import Propellor.Types.Core
    import Propellor.Property.Chroot.Util
    import qualified Propellor.Property.Debootstrap as Debootstrap
    import qualified Propellor.Property.Systemd.Core as Systemd
    import qualified Propellor.Property.File as File
    import qualified Propellor.Shim as Shim
    import Propellor.Property.Mount
    import Utility.Split

    import qualified Data.Map as M
    import System.Posix.Directory

    -- | Specification of a chroot. Normally you'll use `debootstrapped` or
    -- `bootstrapped` or `hostChroot` to construct a Chroot value.
    data Chroot where
    	Chroot :: ChrootBootstrapper b => FilePath -> b -> InfoPropagator -> Host -> Chroot

    instance IsContainer Chroot where
    	containerProperties (Chroot _ _ _ h) = containerProperties h
    	containerInfo (Chroot _ _ _ h) = containerInfo h
    	setContainerProperties (Chroot loc b p h) ps =
    		let h' = setContainerProperties h ps
    		in Chroot loc b p h'

    chrootSystem :: Chroot -> Maybe System
    chrootSystem = fromInfoVal . fromInfo . containerInfo

    instance Show Chroot where
    	show c@(Chroot loc _ _ _) = "Chroot " ++ loc ++ " " ++ show (chrootSystem c)

    -- | Class of things that can do initial bootstrapping of an operating
    -- System in a chroot.
    class ChrootBootstrapper b where
    	-- | Do initial bootstrapping of an operating system in a chroot.
    	-- If the operating System is not supported, return
    	-- Left error message.
    	buildchroot :: b -> Maybe System -> FilePath -> Either String (Property Linux)

    -- | Use this to bootstrap a chroot by extracting a tarball.
    --
    -- The tarball is expected to contain a root directory (no top-level
    -- directory, also known as a "tarbomb").
    -- It may be optionally compressed with any format `tar` knows how to
    -- detect automatically.
    data ChrootTarball = ChrootTarball FilePath

    instance ChrootBootstrapper ChrootTarball where
    	buildchroot (ChrootTarball tb) _ loc = Right $
    		tightenTargets $ extractTarball loc tb

    extractTarball :: FilePath -> FilePath -> Property UnixLike
    extractTarball target src = check (isUnpopulated target) $
    	cmdProperty "tar" params
    		`assume` MadeChange
    		`requires` File.dirExists target
      where
    	params =
    		[ "-C"
    		, target
    		, "-xf"
    		, src
    		]

    -- | Use this to bootstrap a chroot with debootstrap.
    data Debootstrapped = Debootstrapped Debootstrap.DebootstrapConfig

    instance ChrootBootstrapper Debootstrapped where
    	buildchroot (Debootstrapped cf) system loc = case system of
    		(Just s@(System (Debian _ _) _)) -> Right $ debootstrap s
    		(Just s@(System (Buntish _) _)) -> Right $ debootstrap s
    		(Just (System ArchLinux _)) -> Left "Arch Linux not supported by debootstrap."
    		(Just (System (FreeBSD _) _)) -> Left "FreeBSD not supported by debootstrap."
    		Nothing -> Left "Cannot debootstrap; OS not specified"
    	  where
    		debootstrap s = Debootstrap.built loc s cf

    -- | Defines a Chroot at the given location, built with debootstrap.
    --
    -- Properties can be added to configure the Chroot. At a minimum,
    -- add a property such as `osDebian` to specify the operating system
    -- to bootstrap.
    --
    -- > debootstrapped Debootstrap.BuildD "/srv/chroot/ghc-dev" $ props
    -- >	& osDebian Unstable X86_64
    -- >	& Apt.installed ["ghc", "haskell-platform"]
    -- >	& ...
    debootstrapped :: Debootstrap.DebootstrapConfig -> FilePath -> Props metatypes -> Chroot
    debootstrapped conf = bootstrapped (Debootstrapped conf)

    -- | Defines a Chroot at the given location, bootstrapped with the
    -- specified ChrootBootstrapper.
    bootstrapped :: ChrootBootstrapper b => b -> FilePath -> Props metatypes -> Chroot
    bootstrapped bootstrapper location ps = c
      where
    	c = Chroot location bootstrapper propagateChrootInfo (host location ps)

    -- | Ensures that the chroot exists and is provisioned according to its
    -- properties.
    --
    -- Reverting this property removes the chroot. Anything mounted inside it
    -- is first unmounted. Note that it does not ensure that any processes
    -- that might be running inside the chroot are stopped.
    provisioned :: Chroot -> RevertableProperty (HasInfo + Linux) Linux
    provisioned c = provisioned' c False

    provisioned'
    	:: Chroot
    	-> Bool
    	-> RevertableProperty (HasInfo + Linux) Linux
    provisioned' c@(Chroot loc bootstrapper infopropigator _) systemdonly =
    	(infopropigator c normalContainerInfo $ setup `describe` chrootDesc c "exists")
    		<!>
    	(teardown `describe` chrootDesc c "removed")
      where
    	setup :: Property Linux
    	setup = propellChroot c (inChrootProcess (not systemdonly) c) systemdonly
    		`requires` built

    	built = case buildchroot bootstrapper (chrootSystem c) loc of
    		Right p -> p
    		Left e -> cantbuild e

    	cantbuild e = property (chrootDesc c "built") (error e)

    	teardown :: Property Linux
    	teardown = check (not <$> isUnpopulated loc) $
    		property ("removed " ++ loc) $
    			makeChange (removeChroot loc)

    type InfoPropagator = Chroot -> (PropagateInfo -> Bool) -> Property Linux -> Property (HasInfo + Linux)

    propagateChrootInfo :: InfoPropagator
    propagateChrootInfo c@(Chroot location _ _ _) pinfo p =
    	propagateContainer location c pinfo $
    		p `setInfoProperty` chrootInfo c

    chrootInfo :: Chroot -> Info
    chrootInfo (Chroot loc _ _ h) = mempty `addInfo`
    	mempty { _chroots = M.singleton loc h }

    -- | Propellor is run inside the chroot to provision it.
    propellChroot :: Chroot -> ([String] -> IO (CreateProcess, IO ())) -> Bool -> Property UnixLike
    propellChroot c@(Chroot loc _ _ _) mkproc systemdonly = property (chrootDesc c "provisioned") $ do
    	let d = localdir </> shimdir c
    	let me = localdir </> "propellor"
    	shim <- liftIO $ ifM (doesDirectoryExist d)
    		( pure (Shim.file me d)
    		, Shim.setup me Nothing d
    		)
    	ifM (liftIO $ bindmount shim)
    		( chainprovision shim
    		, return FailedChange
    		)
      where
    	bindmount shim = ifM (doesFileExist (loc ++ shim))
    		( return True
    		, do
    			let mntpnt = loc ++ localdir
    			createDirectoryIfMissing True mntpnt
    			boolSystem "mount"
    				[ Param "--bind"
    				, File localdir, File mntpnt
    				]
    		)

    	chainprovision shim = do
    		parenthost <- asks hostName
    		cmd <- liftIO $ toChain parenthost c systemdonly
    		pe <- liftIO standardPathEnv
    		(p, cleanup) <- liftIO $ mkproc
    			[ shim
    			, "--continue"
    			, show cmd
    			]
    		r <- liftIO $ chainPropellor (p { env = Just pe })
    		liftIO cleanup
    		return r

    toChain :: HostName -> Chroot -> Bool -> IO CmdLine
    toChain parenthost (Chroot loc _ _ _) systemdonly = do
    	onconsole <- isConsole <$> getMessageHandle
    	return $ ChrootChain parenthost loc systemdonly onconsole

    chain :: [Host] -> CmdLine -> IO ()
    chain hostlist (ChrootChain hn loc systemdonly onconsole) =
    	case findHostNoAlias hostlist hn of
    		Nothing -> errorMessage ("cannot find host " ++ hn)
    		Just parenthost -> case M.lookup loc (_chroots $ fromInfo $ hostInfo parenthost) of
    			Nothing -> errorMessage ("cannot find chroot " ++ loc ++ " on host " ++ hn)
    			Just h -> go h
      where
    	go h = do
    		changeWorkingDirectory localdir
    		when onconsole forceConsole
    		onlyProcess (provisioningLock loc) $
    			runChainPropellor (setInChroot h) $
    				ensureChildProperties $
    					if systemdonly
    						then [toChildProperty Systemd.installed]
    						else hostProperties h
    chain _ _ = errorMessage "bad chain command"

    inChrootProcess :: Bool -> Chroot -> [String] -> IO (CreateProcess, IO ())
    inChrootProcess keepprocmounted (Chroot loc _ _ _) cmd = do
    	mountproc
    	return (proc "chroot" (loc:cmd), cleanup)
      where
    	-- /proc needs to be mounted in the chroot for the linker to use
    	-- /proc/self/exe which is necessary for some commands to work
    	mountproc = unlessM (elem procloc <$> mountPointsBelow loc) $
    		void $ mount "proc" "proc" procloc mempty

    	procloc = loc </> "proc"

    	cleanup
    		| keepprocmounted = noop
    		| otherwise = whenM (elem procloc <$> mountPointsBelow loc) $
    			umountLazy procloc

    provisioningLock :: FilePath -> FilePath
    provisioningLock containerloc = "chroot" </> mungeloc containerloc ++ ".lock"

    shimdir :: Chroot -> FilePath
    shimdir (Chroot loc _ _ _) = "chroot" </> mungeloc loc ++ ".shim"

    mungeloc :: FilePath -> String
    mungeloc = replace "/" "_"

    chrootDesc :: Chroot -> String -> String
    chrootDesc (Chroot loc _ _ _) desc = "chroot " ++ loc ++ " " ++ desc

    -- | Check if propellor is currently running within a chroot.
    --
    -- This allows properties to check and avoid performing actions that
    -- should not be done in a chroot.
    inChroot :: Propellor Bool
    inChroot = extract . fromMaybe (InChroot False) . fromInfoVal <$> askInfo
      where
    	extract (InChroot b) = b

    setInChroot :: Host -> Host
    setInChroot h = h { hostInfo = hostInfo h `addInfo` InfoVal (InChroot True) }

    newtype InChroot = InChroot Bool
    	deriving (Typeable, Show)

    -- | Runs an action with the true localdir exposed,
    -- not the one bind-mounted into a chroot. The action is passed the
    -- path containing the contents of the localdir outside the chroot.
    --
    -- In a chroot, this is accomplished by temporily bind mounting the localdir
    -- to a temp directory, to preserve access to the original bind mount. Then
    -- we unmount the localdir to expose the true localdir. Finally, to cleanup,
    -- the temp directory is bind mounted back to the localdir.
    exposeTrueLocaldir :: (FilePath -> Propellor a) -> Propellor a
    exposeTrueLocaldir a = ifM inChroot
    	( withTmpDirIn (takeDirectory localdir) "propellor.tmp" $ \tmpdir ->
    		bracket_
    			(movebindmount localdir tmpdir)
    			(movebindmount tmpdir localdir)
    			(a tmpdir)
    	, a localdir
    	)
      where
    	movebindmount from to = liftIO $ do
    		run "mount" [Param "--bind", File from, File to]
    		-- Have to lazy unmount, because the propellor process
    		-- is running in the localdir that it's unmounting..
    		run "umount" [Param "-l", File from]
    		-- We were in the old localdir; move to the new one after
    		-- flipping the bind mounts. Otherwise, commands that try
    		-- to access the cwd will fail because it got umounted out
    		-- from under.
    		changeWorkingDirectory "/"
    		changeWorkingDirectory localdir
    	run cmd ps = unlessM (boolSystem cmd ps) $
    		error $ "exposeTrueLocaldir failed to run " ++ show (cmd, ps)

    -- | Generates a Chroot that has all the properties of a Host.
    --
    -- Note that it's possible to create loops using this, where a host
    -- contains a Chroot containing itself etc. Such loops will be detected at
    -- runtime.
    hostChroot :: ChrootBootstrapper bootstrapper => Host -> bootstrapper -> FilePath -> Chroot
    hostChroot h bootstrapper d = chroot
      where
    	chroot = Chroot d bootstrapper pinfo h
    	pinfo = propagateHostChrootInfo h

    -- This is different than propagateChrootInfo in that Info using
    -- HostContext is not made to use the name of the chroot as its context,
    -- but instead uses the hostname of the Host.
    propagateHostChrootInfo :: Host -> InfoPropagator
    propagateHostChrootInfo h c pinfo p =
    	propagateContainer (hostName h) c pinfo $
    		p `setInfoProperty` chrootInfo c