X-Git-Url: http://gitweb.michael.orlitzky.com/?a=blobdiff_plain;f=src%2FOptionalConfiguration.hs;fp=src%2FOptionalConfiguration.hs;h=f44f77a43396e80fc313cb66fb765ff1fd00c731;hb=08fce472b305acb2cfbffbe877798378c4079cc4;hp=0000000000000000000000000000000000000000;hpb=5c84cab65a3e74aa50dbc2a4904de0c645d3999d;p=dead%2Fhtsn-import.git

diff --git a/src/OptionalConfiguration.hs b/src/OptionalConfiguration.hs
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+{-# LANGUAGE DeriveDataTypeable #-}
+{-# LANGUAGE FlexibleInstances #-}
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE StandaloneDeriving #-}
+
+-- | 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 qualified Data.Configurator.Types as DCT (
+  Configured,
+  Value( String ),
+  convert )
+import Data.Data ( Data )
+import Data.Monoid ( Monoid(..) )
+import Data.Typeable ( Typeable )
+import Paths_htsn_import ( getSysconfDir )
+import System.Directory ( getHomeDirectory )
+import System.FilePath ( (</>) )
+import System.IO.Error ( catchIOError )
+import System.Log ( Priority(..) )
+
+import Logging ( log_error ) -- Can't import report_error from Main
+import Terminal ( display_error ) -- 'cause of circular imports.
+
+
+-- Derive standalone instances of Data and Typeable for Priority. This
+-- is necessary for OptionalConfiguration (which contains a Maybe
+-- Priority) to derive Data and Typeable.
+deriving instance Data Priority
+deriving instance Typeable Priority
+
+-- | 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 {
+    connection_string :: Maybe String,
+    log_file          :: Maybe FilePath,
+    log_level         :: Maybe Priority,
+    syslog            :: Maybe Bool }
+    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 Nothing Nothing
+
+
+  -- | Combine @cfg1@ and @cfg2@, giving precedence to @cfg2@.
+  cfg1 `mappend` cfg2 =
+    OptionalConfiguration
+      (merge_maybes (connection_string cfg1) (connection_string cfg2))
+      (merge_maybes (log_file cfg1) (log_file cfg2))
+      (merge_maybes (log_level cfg1) (log_level cfg2))
+      (merge_maybes (syslog cfg1) (syslog cfg2))
+
+
+instance DCT.Configured Priority where
+  -- | This allows us to read a Priority level out of a Configurator
+  --   config file. By default Configurator wouldn't know what to do,
+  --   so we have to tell it that we expect one of the valid Priority
+  --   constructors.
+  convert (DCT.String "INFO") = Just INFO
+  convert (DCT.String "WARNING") = Just WARNING
+  convert (DCT.String "ERROR") = Just ERROR
+  convert _ = Nothing
+
+
+-- | Obtain an OptionalConfiguration from htsn-importrc 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 $HOME.
+--
+from_rc :: IO OptionalConfiguration
+from_rc = do
+  etc  <- catchIOError getSysconfDir (\e -> do
+                                        display_error (show e)
+                                        log_error (show e)
+                                        return "/etc")
+  home <- catchIOError getHomeDirectory (\e -> do
+                                           display_error (show e)
+                                           log_error (show e)
+                                           return "$(HOME)")
+  let global_config_path = etc </> "htsn-importrc"
+  let user_config_path = home </> ".htsn-importrc"
+  cfg <- DC.load [ DC.Optional global_config_path,
+                   DC.Optional user_config_path ]
+  cfg_connection_string <- DC.lookup cfg "connection_string"
+  cfg_log_file <- DC.lookup cfg "log_file"
+  cfg_log_level <- DC.lookup cfg "log_level"
+  cfg_syslog <- DC.lookup cfg "syslog"
+
+  return $ OptionalConfiguration
+             cfg_connection_string
+             cfg_log_file
+             cfg_log_level
+             cfg_syslog