From 8646a6338c33f999a340cb598237d2b20e7c686e Mon Sep 17 00:00:00 2001
From: Julian Ospald <hasufell@posteo.de>
Date: Sun, 8 May 2016 23:06:40 +0200
Subject: [PATCH] LIB/GTK: simplify error handling, add 'reactOnError'

---
 src/HSFM/FileSystem/Errors.hs       | 39 ++++++++++++++++++++++++++---
 src/HSFM/GUI/Gtk/Callbacks/Utils.hs | 32 ++++++-----------------
 2 files changed, 43 insertions(+), 28 deletions(-)

diff --git a/src/HSFM/FileSystem/Errors.hs b/src/HSFM/FileSystem/Errors.hs
index e47868f..9b4680f 100644
--- a/src/HSFM/FileSystem/Errors.hs
+++ b/src/HSFM/FileSystem/Errors.hs
@@ -17,6 +17,7 @@ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 --}
 
 {-# LANGUAGE DeriveDataTypeable #-}
+{-# LANGUAGE ScopedTypeVariables #-}
 {-# OPTIONS_HADDOCK ignore-exports #-}
 
 -- |Provides error handling.
@@ -26,19 +27,27 @@ module HSFM.FileSystem.Errors where
 import Control.Exception
 import Control.Monad
   (
-    when
-  , forM
+    forM
+  , when
   )
 import Data.ByteString
   (
     ByteString
   )
+import Data.Data
+  (
+    Data(..)
+  )
 import Data.Typeable
 import Foreign.C.Error
   (
     getErrno
   , Errno
   )
+import GHC.IO.Exception
+  (
+    IOErrorType
+  )
 import qualified HPath as P
 import HPath
     (
@@ -49,6 +58,7 @@ import HSFM.Utils.IO
 import System.IO.Error
   (
     catchIOError
+  , ioeGetErrorType
   )
 
 import qualified System.Posix.Directory.ByteString as PFD
@@ -76,7 +86,7 @@ data FmIOException = FileDoesNotExist ByteString
                    | Can'tOpenDirectory ByteString
                    | CopyFailed String
                    | MoveFailed String
-  deriving (Typeable, Eq)
+  deriving (Typeable, Eq, Data)
 
 
 instance Show FmIOException where
@@ -304,3 +314,26 @@ bracketeer before after afterEx thing =
     r <- restore (thing a) `onException` afterEx a
     _ <- after a
     return r
+
+
+reactOnError :: IO a
+             -> [(IOErrorType, IO a)]   -- ^ reaction on IO errors
+             -> [(FmIOException, IO a)] -- ^ reaction on FmIOException
+             -> IO a
+reactOnError a ios fmios =
+  a `catches` [iohandler, fmiohandler]
+  where
+    iohandler = Handler $
+      \(ex :: IOException) ->
+         foldr (\(t, a') y -> if ioeGetErrorType ex == t
+                                then a'
+                                else y)
+               (throwIO ex)
+               ios
+    fmiohandler = Handler $
+      \(ex :: FmIOException) ->
+         foldr (\(t, a') y -> if toConstr ex == toConstr t
+                                then a'
+                                else y)
+               (throwIO ex)
+               fmios
diff --git a/src/HSFM/GUI/Gtk/Callbacks/Utils.hs b/src/HSFM/GUI/Gtk/Callbacks/Utils.hs
index 7d1bfef..2594c5d 100644
--- a/src/HSFM/GUI/Gtk/Callbacks/Utils.hs
+++ b/src/HSFM/GUI/Gtk/Callbacks/Utils.hs
@@ -46,17 +46,8 @@ import HSFM.Utils.IO
     modifyTVarIO
   )
 import Prelude hiding(readFile)
-import System.IO.Error
-  (
-    ioeGetErrorType
-  )
-import Control.Exception
-  (
-    catches
-  , throwIO
-  , IOException
-  , Handler(..)
-  )
+
+
 
 
 -- |Carries out a file operation with the appropriate error handling
@@ -83,21 +74,12 @@ _doFileOperation [] _ _ _ _ = return ()
 _doFileOperation (f:fs) to mcOverwrite mc rest = do
   toname <- P.basename f
   let topath = to P.</> toname
-  catches (mc f topath >> rest)
-          [iohandler topath, fmiohandler topath]
+  reactOnError (mc f topath >> rest)
+    [(AlreadyExists  , collisionAction fileCollisionDialog topath)]
+    [(FileDoesExist{}, collisionAction fileCollisionDialog topath)
+    ,(DirDoesExist{} , collisionAction fileCollisionDialog topath)
+    ,(SameFile{}     , collisionAction renameDialog topath)]
   where
-    iohandler topath =
-      Handler $ \ (ex :: IOException) ->
-                   if ioeGetErrorType ex == AlreadyExists
-                     then collisionAction fileCollisionDialog topath
-                     else throwIO ex
-    fmiohandler topath =
-      Handler $ \ (ex :: FmIOException) ->
-                   if isFileDoesExist ex || isDirDoesExist ex
-                     then collisionAction fileCollisionDialog topath
-                     else (if isSameFile ex
-                             then collisionAction renameDialog topath
-                             else throwIO ex)
     collisionAction diag topath = do
       mcm <- diag . P.fpToString . P.fromAbs $ topath
       forM_ mcm $ \cm -> case cm of