    module Propellor.Property.Network where

    import Propellor.Base
    import Propellor.Property.File

    import Data.Char

    type Interface = String

    -- | Options to put in a stanza of an ifupdown interfaces file.
    type InterfaceOptions = [(String, String)]

    ifUp :: Interface -> Property DebianLike
    ifUp iface = tightenTargets $ cmdProperty "ifup" [iface]
            `assume` MadeChange

    -- | Resets /etc/network/interfaces to a clean and empty state,
    -- containing just the standard loopback interface, and with
    -- interfacesD enabled.
    --
    -- This can be used as a starting point to defining other interfaces.
    --
    -- No interfaces are brought up or down by this property.
    cleanInterfacesFile :: Property DebianLike
    cleanInterfacesFile = interfaceFileContains interfacesFile
            [ "source-directory interfaces.d"
            , ""
            , "# The loopback network interface"
            , "auto lo"
            , "iface lo inet loopback"
            ]
            []
            `describe` ("clean " ++ interfacesFile)

    -- | Configures an interface to get its address via dhcp.
    dhcp :: Interface -> Property DebianLike
    dhcp iface = dhcp' iface mempty

    dhcp' :: Interface -> InterfaceOptions -> Property DebianLike
    dhcp' iface options = interfaceFileContains (interfaceDFile iface)
            [ "auto " ++ iface
            , "iface " ++ iface ++ " inet dhcp"
            ] options
            `describe` ("dhcp " ++ iface)
            `requires` interfacesDEnabled

    newtype Gateway = Gateway IPAddr

    -- | Configures an interface with a static address and gateway.
    static :: Interface -> IPAddr -> Maybe Gateway -> Property DebianLike
    static iface addr gateway = static' iface addr gateway mempty

    static' :: Interface -> IPAddr -> Maybe Gateway -> InterfaceOptions -> Property DebianLike
    static' iface addr gateway options =
            interfaceFileContains (interfaceDFile iface) headerlines options'
            `describe` ("static IP address for " ++ iface)
            `requires` interfacesDEnabled
      where
            headerlines =
                    [ "auto " ++ iface
                    , "iface " ++ iface ++ " " ++ inet ++ " static"
                    ]
            options' = catMaybes
                    [ Just $ ("address", val addr)
                    , case gateway of
                            Just (Gateway gaddr) ->
                                    Just ("gateway", val gaddr)
                            Nothing -> Nothing
                    ] ++ options
            inet = case addr of
                    IPv4 _ -> "inet"
                    IPv6 _ -> "inet6"

    -- | Writes a static interface file for the specified interface
    -- to preserve its current configuration.
    --
    -- The interface has to be up already. It could have been brought up by
    -- DHCP, or by other means. The current ipv4 addresses
    -- and routing configuration of the interface are written into the file.
    --
    -- If the interface file already exists, this property does nothing,
    -- no matter its content.
    --
    -- (ipv6 addresses are not included because it's assumed they come up
    -- automatically in most situations.)
    preserveStatic :: Interface -> Property DebianLike
    preserveStatic iface = tightenTargets $
            check (not <$> doesFileExist f) setup
                    `describe` desc
                    `requires` interfacesDEnabled
      where
            f = interfaceDFile iface
            desc = "static " ++ iface
            setup :: Property DebianLike
            setup = property' desc $ \o -> do
                    ls <- liftIO $ lines <$> readProcess "ip"
                            ["-o", "addr", "show", iface, "scope", "global"]
                    stanzas <- liftIO $ concat <$> mapM mkstanza ls
                    ensureProperty o $ hasContent f $ ("auto " ++ iface) : stanzas
            mkstanza ipline = case words ipline of
                    -- Note that the IP address is written CIDR style, so
                    -- the netmask does not need to be specified separately.
                    (_:iface':"inet":addr:_) | iface' == iface -> do
                            gw <- getgateway
                            return $ catMaybes
                                    [ Just $ "iface " ++ iface ++ " inet static"
                                    , Just $ "\taddress " ++ addr
                                    , ("\tgateway " ++) <$> gw
                                    ]
                    _ -> return []
            getgateway = do
                    rs <- lines <$> readProcess "ip"
                            ["route", "show", "scope", "global", "dev", iface]
                    return $ case words <$> headMaybe rs of
                            Just ("default":"via":gw:_) -> Just gw
                            _ -> Nothing

    -- | 6to4 ipv6 connection, should work anywhere
    ipv6to4 :: Property DebianLike
    ipv6to4 = tightenTargets $ interfaceFileContains (interfaceDFile "sit0")
            [ "auto sit0"
            , "iface sit0 inet6 static"
            ]
            [ ("address", "2002:5044:5531::1")
            , ("netmask", "64")
            , ("gateway", "::192.88.99.1")
            ]
            `describe` "ipv6to4"
            `requires` interfacesDEnabled
            `onChange` ifUp "sit0"

    interfacesFile :: FilePath
    interfacesFile = "/etc/network/interfaces"

    -- | A file in the interfaces.d directory.
    interfaceDFile :: Interface -> FilePath
    interfaceDFile i = "/etc/network/interfaces.d" </> escapeInterfaceDName i

    -- | /etc/network/interfaces.d/ files have to match -- ^[a-zA-Z0-9_-]+$
    -- see "man 5 interfaces"
    escapeInterfaceDName :: Interface -> FilePath
    escapeInterfaceDName = filter (\c -> isAscii c && (isAlphaNum c || c `elem` "_-"))

    -- | Ensures that files in the the interfaces.d directory are used.
    -- interfacesDEnabled :: Property DebianLike
    interfacesDEnabled :: Property DebianLike
    interfacesDEnabled = tightenTargets $
            containsLine interfacesFile "source-directory interfaces.d"
                    `describe` "interfaces.d directory enabled"

    interfaceFileContains :: FilePath -> [String] -> InterfaceOptions -> Property DebianLike
    interfaceFileContains f headerlines options = tightenTargets $ hasContent f $
            warning : headerlines ++ map fmt options
      where
            fmt (k, v) = "\t" ++ k ++ " " ++ v
            warning = "# Deployed by propellor, do not edit."