Querying

src/Control/Addressbook/Query.hs

@@ -0,0 +1,48 @@
+{-# LANGUAGE TypeApplications #-}
+module Control.Addressbook.Query where
+
+import Data.Text
+       (Text)
+import qualified Data.Text as T
+import qualified Data.Text.Encoding as TE
+
+import Conduit
+import qualified Data.Conduit.Binary as CB
+import qualified Data.Conduit.Combinators as C
+import qualified Data.Conduit.List as CL
+import qualified Data.Conduit.Text as CT
+
+import qualified Data.Trie as Trie
+
+import System.IO
+       (stdout)
+
+import Data.Maybe
+       (fromMaybe)
+import System.Environment
+       (lookupEnv)
+import System.FilePath
+       ((</>))
+
+import Control.Exception
+       (catch)
+
+query :: Text -> IO ()
+query prefix = do
+  datDir <- fromMaybe "./" <$> lookupEnv "HOME"
+  state <- catch @IOError (runResourceT $ runConduit $ readState datDir) (\_ -> pure Trie.empty)
+  runConduit $ outputResults state
+  where
+    readState :: FilePath -> ConduitM () Void (ResourceT IO) (Trie.Trie [Text])
+    readState dir =
+      CB.sourceFile (dir </> ".addressbook.dat")
+        .| CT.decode CT.utf8
+        .| CT.lines
+        .| C.foldMap (\s -> Trie.singleton (TE.encodeUtf8 $ T.toLower s) [s])
+    outputResults :: Trie.Trie [Text] -> ConduitM () Void IO ()
+    outputResults state =
+      CL.sourceList (Trie.elems $ Trie.submap (TE.encodeUtf8 prefix) state)
+        .| C.concat
+        .| C.map (<> "\n")
+        .| CT.encode CT.utf8
+        .| CB.sinkHandle stdout