Display error descriptions

lib/SlackBuilder/Trans.hs

@@ -11,12 +11,14 @@ module SlackBuilder.Trans
 
 import Control.Monad.Trans.Reader (ReaderT(..), asks)
 import Data.Text (Text)
+import qualified Data.Text as Text
 import SlackBuilder.Config
 import Control.Monad.IO.Class (MonadIO(..))
 import Control.Monad.Catch (MonadCatch(..), MonadThrow(..))
 import Control.Exception (Exception(..))
 import System.FilePath ((</>))
 import Text.URI (URI)
+import qualified Text.URI as URI
 import qualified Codec.Compression.Lzma as Lzma
 
 data SlackBuilderException
@@ -26,7 +28,34 @@ data SlackBuilderException
     deriving Show
 
 instance Exception SlackBuilderException
-
+  where
+    displayException (UpdaterNotFound updateName) = Text.unpack
+        $ Text.concat ["Requested package \"", updateName, "\" was not found"]
+    displayException (HttpsUrlExpected givenURI) = Text.unpack
+        $ "Only https URLs are supported, got: " <> URI.render givenURI
+    displayException (LzmaDecompressionFailed Lzma.LzmaRetOK) =
+        "Operation completed successfully"
+    displayException (LzmaDecompressionFailed Lzma.LzmaRetStreamEnd) =
+        "End of stream was reached"
+    displayException (LzmaDecompressionFailed Lzma.LzmaRetUnsupportedCheck) =
+        "Cannot calculate the integrity check"
+    displayException (LzmaDecompressionFailed Lzma.LzmaRetGetCheck) =
+        "Integrity check type is now available"
+    displayException (LzmaDecompressionFailed Lzma.LzmaRetMemError) =
+        "Cannot allocate memory"
+    displayException (LzmaDecompressionFailed Lzma.LzmaRetMemlimitError) =
+        "Memory usage limit was reached"
+    displayException (LzmaDecompressionFailed Lzma.LzmaRetFormatError) =
+        "File format not recognized"
+    displayException (LzmaDecompressionFailed Lzma.LzmaRetOptionsError) =
+        "Invalid or unsupported options"
+    displayException (LzmaDecompressionFailed Lzma.LzmaRetDataError) =
+        "Data is corrupt"
+    displayException (LzmaDecompressionFailed Lzma.LzmaRetBufError) =
+        "No progress is possible"
+    displayException (LzmaDecompressionFailed Lzma.LzmaRetProgError) =
+        "Programming error"
+ 
 newtype SlackBuilderT a = SlackBuilderT
     { runSlackBuilderT :: ReaderT Settings IO a
     }