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. We thread this throughout the rest of the program.
   4
   5 module Configuration (
   6   Configuration(..),
   7   merge_optional )
   8 where
   9
  10 import System.Console.CmdArgs.Default (Default(..))
  11
  12 import FeedHosts (FeedHosts(..))
  13 import qualified OptionalConfiguration as OC (OptionalConfiguration(..))
  14
  15 data Configuration =
  16   Configuration {
  17     feed_hosts       :: FeedHosts,
  18     password         :: String,
  19     output_directory :: FilePath,
  20     username         :: String }
  21     deriving (Show)
  22
  23 -- | A Configuration with all of its fields set to their default
  24 --   values.
  25 instance Default Configuration where
  26   def = Configuration def def "." def
  27
  28 merge_optional :: Configuration
  29                -> OC.OptionalConfiguration
  30                -> Configuration
  31 merge_optional cfg opt_cfg =
  32   Configuration
  33     all_feed_hosts
  34     (merge (password cfg) (OC.password opt_cfg))
  35     (merge (output_directory cfg) (OC.output_directory opt_cfg))
  36     (merge (username cfg) (OC.username opt_cfg))
  37   where
  38     merge :: a -> Maybe a -> a
  39     merge x Nothing  = x
  40     merge _ (Just y) = y
  41
  42     -- If there are any optional usernames, use only those.
  43     all_feed_hosts = if (null (get_feed_hosts (OC.feed_hosts opt_cfg)))
  44                     then (feed_hosts cfg)
  45                     else (OC.feed_hosts opt_cfg)
  46