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 (OptionalConfiguration(..))
  14 import TSN.FeedHosts (FeedHosts(..))
  15
  16 data Configuration =
  17   Configuration {
  18     feed_hosts       :: FeedHosts,
  19     log_file         :: FilePath,
  20     log_level        :: Priority,
  21     password         :: String,
  22     output_directory :: FilePath,
  23     syslog           :: Bool,
  24     username         :: String }
  25     deriving (Show)
  26
  27 -- | A Configuration with all of its fields set to their default
  28 --   values.
  29 instance Default Configuration where
  30   def = Configuration def "htsn.log" INFO def "." True def
  31
  32
  33 -- | Merge a Configuration with an OptionalConfiguration. This is more
  34 --   or less the Monoid instance for OptionalConfiguration, but since
  35 --   the two types are different, we have to repeat ourselves.
  36 merge_optional :: Configuration
  37                -> OC.OptionalConfiguration
  38                -> Configuration
  39 merge_optional cfg opt_cfg =
  40   Configuration
  41     all_feed_hosts
  42     (merge (log_file cfg) (OC.log_file opt_cfg))
  43     (merge (log_level cfg) (OC.log_level opt_cfg))
  44     (merge (password cfg) (OC.password opt_cfg))
  45     (merge (output_directory cfg) (OC.output_directory opt_cfg))
  46     (merge (syslog cfg) (OC.syslog opt_cfg))
  47     (merge (username cfg) (OC.username opt_cfg))
  48   where
  49     merge :: a -> Maybe a -> a
  50     merge x Nothing  = x
  51     merge _ (Just y) = y
  52
  53     -- If there are any optional usernames, use only those.
  54     all_feed_hosts = if (null (get_feed_hosts (OC.feed_hosts opt_cfg)))
  55                      then (feed_hosts cfg)
  56                      else (OC.feed_hosts opt_cfg)
  57