src/OptionalConfiguration.hs

   1 {-# LANGUAGE DeriveDataTypeable #-}
   2 {-# LANGUAGE FlexibleInstances #-}
   3 {-# LANGUAGE OverloadedStrings #-}
   4 {-# LANGUAGE StandaloneDeriving #-}
   5
   6 -- | An OptionalConfiguration is just like a 'Configuration', except
   7 --   all of its fields are optional. The user can set options in two
   8 --   places: the command-line, and a configuration file. Obviously if
   9 --   a parameter is set in one place, it doesn't need to be set in the
  10 --   other. Thus, the latter needs to be optional.
  11 --
  12
  13 module OptionalConfiguration (
  14   OptionalConfiguration(..),
  15   from_rc,
  16   merge_maybes )
  17 where
  18
  19 import qualified Data.Configurator as DC (
  20   Worth(Optional),
  21   load,
  22   lookup )
  23 import qualified Data.Configurator.Types as DCT (
  24   Configured,
  25   Value( String ),
  26   convert )
  27 import Data.Data ( Data )
  28 import Data.Maybe ( fromMaybe )
  29 import Data.Monoid ( Monoid(..) )
  30 import Data.Typeable ( Typeable )
  31 import Paths_htsn ( getSysconfDir )
  32 import System.Directory ( getHomeDirectory )
  33 import System.FilePath ( (</>) )
  34 import System.IO.Error ( catchIOError )
  35 import System.Log ( Priority(..) )
  36
  37 import FeedHosts ( FeedHosts(..) )
  38 import Logging ( log_error ) -- Can't import report_error from Main
  39 import Terminal ( display_error ) -- 'cause of circular imports.
  40
  41
  42 -- Derive standalone instances of Data and Typeable for Priority. This
  43 -- is necessary for OptionalConfiguration (which contains a Maybe
  44 -- Priority) to derive Data and Typeable.
  45 deriving instance Data Priority
  46 deriving instance Typeable Priority
  47
  48 -- | The same as Configuration, except everything is optional. It's easy to
  49 --   merge two of these by simply dropping the Nothings in favor of
  50 --   the Justs. The 'feed_hosts' are left un-maybed so that cmdargs
  51 --   can parse more than one of them.
  52 --
  53 data OptionalConfiguration =
  54   OptionalConfiguration {
  55     daemonize        :: Maybe Bool,
  56     feed_hosts       :: FeedHosts,
  57     log_file         :: Maybe FilePath,
  58     log_level        :: Maybe Priority,
  59     output_directory :: Maybe FilePath,
  60     password         :: Maybe String,
  61     pidfile          :: Maybe FilePath,
  62     run_as_group     :: Maybe String,
  63     run_as_user      :: Maybe String,
  64     syslog           :: Maybe Bool,
  65     username         :: Maybe String }
  66     deriving (Show, Data, Typeable)
  67
  68
  69 -- | Combine two Maybes into one, essentially mashing them
  70 --   together. We give precedence to the second argument when both are
  71 --   Justs.
  72 merge_maybes :: (Maybe a) -> (Maybe a) -> (Maybe a)
  73 merge_maybes Nothing Nothing   = Nothing
  74 merge_maybes (Just x) Nothing  = Just x
  75 merge_maybes Nothing (Just x)  = Just x
  76 merge_maybes (Just _) (Just y) = Just y
  77
  78
  79 -- | The Monoid instance for these lets us "combine" two
  80 --   OptionalConfigurations. The "combine" operation that we'd like to
  81 --   perform is, essentially, to mash them together. So if we have two
  82 --   OptionalConfigurations, each half full, we could combine them
  83 --   into one big one.
  84 --
  85 --   This is used to merge command-line and config-file settings.
  86 --
  87 instance Monoid OptionalConfiguration where
  88   -- | An empty OptionalConfiguration.
  89   mempty = OptionalConfiguration
  90              Nothing
  91              (FeedHosts [])
  92              Nothing
  93              Nothing
  94              Nothing
  95              Nothing
  96              Nothing
  97              Nothing
  98              Nothing
  99              Nothing
 100              Nothing
 101
 102
 103   -- | Combine @cfg1@ and @cfg2@, giving precedence to @cfg2@.
 104   cfg1 `mappend` cfg2 =
 105     OptionalConfiguration
 106       (merge_maybes (daemonize cfg1) (daemonize cfg2))
 107       all_feed_hosts
 108       (merge_maybes (log_file cfg1) (log_file cfg2))
 109       (merge_maybes (log_level cfg1) (log_level cfg2))
 110       (merge_maybes (output_directory cfg1) (output_directory cfg2))
 111       (merge_maybes (password cfg1) (password cfg2))
 112       (merge_maybes (pidfile cfg1) (pidfile cfg2))
 113       (merge_maybes (run_as_group cfg1) (run_as_group cfg2))
 114       (merge_maybes (run_as_user cfg1) (run_as_user cfg2))
 115       (merge_maybes (syslog cfg1) (syslog cfg2))
 116       (merge_maybes (username cfg1) (username cfg2))
 117     where
 118       -- Use only the latter feed_hosts if there are any.
 119       all_feed_hosts =
 120         feed_hosts $ if (null (get_feed_hosts (feed_hosts cfg2)))
 121                     then cfg1
 122                     else cfg2
 123
 124
 125 instance DCT.Configured Priority where
 126   -- | This allows us to read a Priority level out of a Configurator
 127   --   config file. By default Configurator wouldn't know what to do,
 128   --   so we have to tell it that we expect one of the valid Priority
 129   --   constructors.
 130   convert (DCT.String "INFO") = Just INFO
 131   convert (DCT.String "WARNING") = Just WARNING
 132   convert (DCT.String "ERROR") = Just ERROR
 133   convert _ = Nothing
 134
 135
 136 -- | Obtain an OptionalConfiguration from htsnrc in either the global
 137 --   configuration directory or the user's home directory. The one in
 138 --   $HOME is prefixed by a dot so that it is hidden.
 139 --
 140 --   We make an attempt at cross-platform compatibility; we will try
 141 --   to find the correct directory even on Windows. But if the calls
 142 --   to getHomeDirectory/getSysconfDir fail for whatever reason, we
 143 --   fall back to using the Unix-specific /etc and $HOME.
 144 --
 145 from_rc :: IO OptionalConfiguration
 146 from_rc = do
 147   etc  <- catchIOError getSysconfDir (\e -> do
 148                                         display_error (show e)
 149                                         log_error (show e)
 150                                         return "/etc")
 151   home <- catchIOError getHomeDirectory (\e -> do
 152                                            display_error (show e)
 153                                            log_error (show e)
 154                                            return "$(HOME)")
 155   let global_config_path = etc </> "htsnrc"
 156   let user_config_path = home </> ".htsnrc"
 157   cfg <- DC.load [ DC.Optional global_config_path,
 158                    DC.Optional user_config_path ]
 159   cfg_daemonize <- DC.lookup cfg "daemonize"
 160   cfg_feed_hosts <- DC.lookup cfg "feed_hosts"
 161   cfg_log_file <- DC.lookup cfg "log_file"
 162   cfg_log_level <- DC.lookup cfg "log_level"
 163   cfg_output_directory <- DC.lookup cfg "output_directory"
 164   cfg_password <- DC.lookup cfg "password"
 165   cfg_pidfile <- DC.lookup cfg "pidfile"
 166   cfg_run_as_group <- DC.lookup cfg "run_as_group"
 167   cfg_run_as_user <- DC.lookup cfg "run_as_user"
 168   cfg_syslog <- DC.lookup cfg "syslog"
 169   cfg_username <- DC.lookup cfg "username"
 170
 171   return $ OptionalConfiguration
 172              cfg_daemonize
 173              (fromMaybe (FeedHosts []) cfg_feed_hosts)
 174              cfg_log_file
 175              cfg_log_level
 176              cfg_output_directory
 177              cfg_password
 178              cfg_pidfile
 179              cfg_run_as_group
 180              cfg_run_as_user
 181              cfg_syslog
 182              cfg_username