{-# LANGUAGE DeriveDataTypeable #-} {-# LANGUAGE OverloadedStrings #-} -- | An OptionalConfiguration is just like a 'Configuration', except -- all of its fields are optional. The user can set options in two -- places: the command-line, and a configuration file. Obviously if -- a parameter is set in one place, it doesn't need to be set in the -- other. Thus, the latter needs to be optional. -- module OptionalConfiguration ( OptionalConfiguration(..), from_rc, merge_maybes ) where import qualified Data.Configurator as DC ( Worth(Optional), load, lookup ) import Data.Maybe ( fromMaybe ) import Data.Monoid ( Monoid(..) ) import Data.Data ( Data ) import Data.Typeable ( Typeable ) import Paths_list_remote_forwards ( getSysconfDir ) import System.Directory ( getHomeDirectory ) import System.FilePath ( () ) import System.IO.Error ( catchIOError ) import MxList ( MxList(..) ) -- | The same as Configuration, except everything is optional. It's easy to -- merge two of these by simply dropping the Nothings in favor of -- the Justs. The 'feed_hosts' are left un-maybed so that cmdargs -- can parse more than one of them. -- data OptionalConfiguration = OptionalConfiguration { database :: Maybe String, domain_query :: Maybe String, exclude_mx :: MxList, forward_query :: Maybe String, host :: Maybe String, password :: Maybe String, port :: Maybe Int, username :: Maybe String } deriving (Show, Data, Typeable) -- | Combine two Maybes into one, essentially mashing them -- together. We give precedence to the second argument when both are -- Justs. merge_maybes :: (Maybe a) -> (Maybe a) -> (Maybe a) merge_maybes Nothing Nothing = Nothing merge_maybes (Just x) Nothing = Just x merge_maybes Nothing (Just x) = Just x merge_maybes (Just _) (Just y) = Just y -- | The Monoid instance for these lets us "combine" two -- OptionalConfigurations. The "combine" operation that we'd like to -- perform is, essentially, to mash them together. So if we have two -- OptionalConfigurations, each half full, we could combine them -- into one big one. -- -- This is used to merge command-line and config-file settings. -- instance Monoid OptionalConfiguration where -- | An empty OptionalConfiguration. mempty = OptionalConfiguration Nothing Nothing (MxList []) Nothing Nothing Nothing Nothing Nothing -- | Combine @cfg1@ and @cfg2@, giving precedence to @cfg2@. cfg1 `mappend` cfg2 = OptionalConfiguration (merge_maybes (database cfg1) (database cfg2)) (merge_maybes (domain_query cfg1) (domain_query cfg2)) all_excluded_mx (merge_maybes (forward_query cfg1) (forward_query cfg2)) (merge_maybes (host cfg1) (host cfg2)) (merge_maybes (password cfg1) (password cfg2)) (merge_maybes (port cfg1) (port cfg2)) (merge_maybes (username cfg1) (username cfg2)) where -- Use only the latter exclude_mx if there are any. all_excluded_mx = exclude_mx $ if (null (get_mxs $ exclude_mx cfg2)) then cfg1 else cfg2 -- | Obtain an OptionalConfiguration from list-remote-forwardsrc in -- either the global configuration directory or the user's home -- directory. The one in $HOME is prefixed by a dot so that it is -- hidden. -- -- We make an attempt at cross-platform compatibility; we will try -- to find the correct directory even on Windows. But if the calls -- to getHomeDirectory/getSysconfDir fail for whatever reason, we -- fall back to using the Unix-specific /etc and $HOME. -- from_rc :: IO OptionalConfiguration from_rc = do etc <- catchIOError getSysconfDir (\e -> do putStrLn $ "ERROR: " ++ (show e) return "/etc") home <- catchIOError getHomeDirectory (\e -> do putStrLn $ "ERROR: " ++ (show e) return "$(HOME)") let global_config_path = etc "list-remote-forwardsrc" let user_config_path = home ".list-remote-forwardsrc" cfg <- DC.load [ DC.Optional global_config_path, DC.Optional user_config_path ] cfg_database <- DC.lookup cfg "database" cfg_domain_query <- DC.lookup cfg "domain_query" cfg_exclude_mx <- DC.lookup cfg "exclude_mx" cfg_forward_query <- DC.lookup cfg "forward_query" cfg_host <- DC.lookup cfg "host" cfg_password <- DC.lookup cfg "password" cfg_port <- DC.lookup cfg "port" cfg_username <- DC.lookup cfg "username" return $ OptionalConfiguration cfg_database cfg_domain_query (fromMaybe (MxList []) cfg_exclude_mx) cfg_forward_query cfg_host cfg_password cfg_port cfg_username