LIB: add History module

hsfm.cabal

@@ -26,6 +26,7 @@ library
   exposed-modules:
                        HSFM.FileSystem.FileType
                        HSFM.FileSystem.UtilTypes
+                       HSFM.History
                        HSFM.Utils.IO
                        HSFM.Utils.MyPrelude
 

src/HSFM/History.hs

@@ -0,0 +1,61 @@
+{--
+HSFM, a filemanager written in Haskell.
+Copyright (C) 2016 Julian Ospald
+
+This program is free software; you can redistribute it and/or
+modify it under the terms of the GNU General Public License
+version 2 as published by the Free Software Foundation.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program; if not, write to the Free Software
+Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+--}
+
+{-# OPTIONS_HADDOCK ignore-exports #-}
+
+module HSFM.History where
+
+
+import HPath
+  (
+    Abs
+  , Path
+  )
+
+
+
+-- |Browsing history. For `forwardHistory` and `backwardsHistory`
+-- the first item is the most recent one.
+data BrowsingHistory = BrowsingHistory {
+    backwardsHistory :: [Path Abs]
+  , currentDir       :: Path Abs
+  , forwardHistory   :: [Path Abs]
+  , maxSize          :: Int
+}
+
+
+-- |This is meant to be called after e.g. a new path is entered
+-- (not navigated to via the history) and the history needs updating.
+goNewPath :: Path Abs -> BrowsingHistory -> BrowsingHistory
+goNewPath p (BrowsingHistory b cd _ s) =
+  BrowsingHistory (take s $ cd:b) p [] s
+
+
+-- |Go back in the history.
+goBack :: BrowsingHistory -> BrowsingHistory
+goBack bh@(BrowsingHistory [] _ _ _)   = bh
+goBack (BrowsingHistory (b:bs) cd fs s) =
+  BrowsingHistory bs b (take s $ cd:fs) s
+
+
+-- |Go forward in the history.
+goForward :: BrowsingHistory -> BrowsingHistory
+goForward bh@(BrowsingHistory _ _ [] _) = bh
+goForward (BrowsingHistory bs cd (f:fs) s) =
+  BrowsingHistory (take s $ cd:bs) f fs s
+