src/Configuration.hs

   1 -- | This module defines the 'Configuration' type, which is just a
   2 --   wrapper around all of the configuration options we accept on the
   3 --   command line.
   4 --
   5 module Configuration (
   6   Configuration(..),
   7   merge_optional )
   8 where
   9
  10 import System.Console.CmdArgs.Default ( Default(..) )
  11 import System.Log ( Priority( INFO ) )
  12
  13 import qualified OptionalConfiguration as OC (
  14   OptionalConfiguration(..),
  15   merge_maybes )
  16 import TSN.FeedHosts (FeedHosts(..))
  17
  18 data Configuration =
  19   Configuration {
  20     feed_hosts       :: FeedHosts,
  21     log_file         :: Maybe FilePath,
  22     log_level        :: Priority,
  23     password         :: String,
  24     output_directory :: FilePath,
  25     syslog           :: Bool,
  26     username         :: String }
  27     deriving (Show)
  28
  29 -- | A Configuration with all of its fields set to their default
  30 --   values.
  31 instance Default Configuration where
  32   def = Configuration def def INFO def "." def def
  33
  34
  35 -- | Merge a Configuration with an OptionalConfiguration. This is more
  36 --   or less the Monoid instance for OptionalConfiguration, but since
  37 --   the two types are different, we have to repeat ourselves.
  38 merge_optional :: Configuration
  39                -> OC.OptionalConfiguration
  40                -> Configuration
  41 merge_optional cfg opt_cfg =
  42   Configuration
  43     all_feed_hosts
  44     (OC.merge_maybes (log_file cfg) (OC.log_file opt_cfg))
  45     (merge (log_level cfg) (OC.log_level opt_cfg))
  46     (merge (password cfg) (OC.password opt_cfg))
  47     (merge (output_directory cfg) (OC.output_directory opt_cfg))
  48     (merge (syslog cfg) (OC.syslog opt_cfg))
  49     (merge (username cfg) (OC.username opt_cfg))
  50   where
  51     -- | If the thing on the right is Just something, return that
  52     --   something, otherwise return the thing on the left.
  53     merge :: a -> Maybe a -> a
  54     merge x Nothing  = x
  55     merge _ (Just y) = y
  56
  57     -- If there are any optional usernames, use only those.
  58     all_feed_hosts = if (null (get_feed_hosts (OC.feed_hosts opt_cfg)))
  59                      then (feed_hosts cfg)
  60                      else (OC.feed_hosts opt_cfg)
  61