+import Data.Maybe ( fromMaybe )
+import Data.String.Utils ( join )
+import Database.HDBC ( SqlError( seNativeError, seErrorMsg ), handleSql )
+import Database.HDBC.PostgreSQL ( connectPostgreSQL )
+import Database.HDBC.Sqlite3 ( connectSqlite3 )
+import System.Console.CmdArgs ( def )
+import System.Directory ( doesFileExist )
+import System.IO ( hPutStrLn, stderr )
+import CommandLine ( get_args )
+import Configuration (
+ Configuration( host, port, username, password, database ),
+ merge_optional )
+import qualified OptionalConfiguration as OC ( from_rc )
+import Report ( report )
+
+
+-- | Construct a connection string (postgres-only, for now) from a
+-- 'Configuration'. All of these are optional, at least for
+-- Postgres, and so we want to avoid appending e.g. \"host=\" to the
+-- connection string if @(host cfg)@ is 'Nothing'.
+--
+-- Examples:
+--
+-- >>> let default_cfg = def :: Configuration
+-- >>> let cfg = default_cfg { host = Just "localhost" }
+-- >>> connection_string cfg
+-- "host=localhost"
+-- >>> let cfg2 = cfg { username = Just "postgres" }
+-- >>> connection_string cfg2
+-- "host=localhost user=postgres"
+--
+connection_string :: Configuration -> String
+connection_string cfg =
+ trim $ join " " [host_part, port_part, user_part, pw_part, db_part]
+ where
+ -- | Strip leading/trailing whitespace, and collapse multiple
+ -- consecutive spaces into one.
+ trim :: String -> String
+ trim = unwords . words
+
+ host_part = let h = fmap ("host=" ++) (host cfg) in fromMaybe "" h
+ port_part = let p = fmap (("port=" ++) . show) (port cfg) in fromMaybe "" p
+ user_part = let u = fmap ("user=" ++) (username cfg) in fromMaybe "" u
+ pw_part = let pw = fmap ("password=" ++) (password cfg) in fromMaybe "" pw
+ db_part = let db = fmap ("dbname=" ++) (database cfg) in fromMaybe "" db
+
+