    module Propellor.Property.Fstab (
            FsType,
            Source,
            MountPoint,
            MountOpts(..),
            module Propellor.Property.Fstab,
    ) where

    import Propellor.Base
    import qualified Propellor.Property.File as File
    import Propellor.Property.Mount

    import Data.Char
    import Data.List
    import Utility.Table

    -- | Ensures that </etc/fstab> contains a line mounting the specified
    -- `Source` on the specified `MountPoint`, and that it's currently mounted.
    --
    -- For example:
    --
    -- > mounted "auto" "/dev/sdb1" "/srv" mempty
    --
    -- Note that if anything else is already mounted at the `MountPoint`, it
    -- will be left as-is by this property.
    mounted :: FsType -> Source -> MountPoint -> MountOpts -> Property Linux
    mounted fs src mnt opts = tightenTargets $
            listed fs src mnt opts
                    `before` mountnow
                    `requires` File.dirExists mnt
      where
            -- This use of mountPoints, which is linux-only, is why this
            -- property currently only supports linux.
            mountnow = check (notElem mnt <$> mountPoints) $
                    cmdProperty "mount" [mnt]

    -- | Ensures that </etc/fstab> contains a line mounting the specified
    -- `Source` on the specified `MountPoint`. Does not ensure that it's
    -- currently `mounted`.
    listed :: FsType -> Source -> MountPoint -> MountOpts -> Property UnixLike
    listed fs src mnt opts = "/etc/fstab" `File.containsLine` l
            `describe` (mnt ++ " mounted by fstab")
      where
            l = intercalate "\t" [src, mnt, fs, formatMountOpts opts, dump, passno]
            dump = "0"
            passno = "2"

    -- | Ensures that </etc/fstab> contains a line enabling the specified
    -- `Source` to be used as swap space, and that it's enabled.
    swap :: Source -> Property Linux
    swap src = listed "swap" src "none" mempty
            `onChange` swapOn src

    newtype SwapPartition = SwapPartition FilePath

    -- | Replaces </etc/fstab> with a file that should cause the currently
    -- mounted partitions to be re-mounted the same way on boot.
    --
    -- For each specified MountPoint, the UUID of each partition
    -- (or if there is no UUID, its label), its filesystem type,
    -- and its mount options are all automatically probed.
    --
    -- The SwapPartitions are also included in the generated fstab.
    fstabbed :: [MountPoint] -> [SwapPartition] -> Property Linux
    fstabbed mnts swaps = property' "fstabbed" $ \o -> do
            fstab <- liftIO $ genFstab mnts swaps id
            ensureProperty o $
                    "/etc/fstab" `File.hasContent` fstab

    genFstab :: [MountPoint] -> [SwapPartition] -> (MountPoint -> MountPoint) -> IO [String]
    genFstab mnts swaps mnttransform = do
            fstab <- liftIO $ mapM getcfg (sort mnts)
            swapfstab <- liftIO $ mapM getswapcfg swaps
            return $ header ++ formatTable (legend : fstab ++ swapfstab)
      where
            header =
                    [ "# /etc/fstab: static file system information. See fstab(5)"
                    , "# "
                    ]
            legend = ["# <file system>", "<mount point>", "<type>", "<options>", "<dump>", "<pass>"]
            getcfg mnt = sequence
                    [ fromMaybe (error $ "unable to find mount source for " ++ mnt)
                            <$> getM (\a -> a mnt)
                                    [ uuidprefix getMountUUID
                                    , sourceprefix getMountLabel
                                    , getMountSource
                                    ]
                    , pure (mnttransform mnt)
                    , fromMaybe "auto" <$> getFsType mnt
                    , formatMountOpts <$> getFsMountOpts mnt
                    , pure "0"
                    , pure (if mnt == "/" then "1" else "2")
                    ]
            getswapcfg (SwapPartition s) = sequence
                    [ fromMaybe s <$> getM (\a -> a s)
                            [ uuidprefix getSourceUUID
                            , sourceprefix getSourceLabel
                            ]
                    , pure "none"
                    , pure "swap"
                    , pure (formatMountOpts mempty)
                    , pure "0"
                    , pure "0"
                    ]
            prefix s getter m = fmap (s ++) <$> getter m
            uuidprefix = prefix "UUID="
            sourceprefix = prefix "LABEL="

    -- | Checks if </etc/fstab> is not configured.
    -- This is the case if it doesn't exist, or
    -- consists entirely of blank lines or comments.
    --
    -- So, if you want to only replace the fstab once, and then never touch it
    -- again, allowing local modifications:
    --
    -- > check noFstab (fstabbed mnts [])
    noFstab :: IO Bool
    noFstab = ifM (doesFileExist "/etc/fstab")
            ( null . filter iscfg . lines <$> readFile "/etc/fstab"
            , return True
            )
      where
            iscfg l
                    | null l = False
                    | otherwise = not $ "#" `isPrefixOf` dropWhile isSpace l