diff --git a/LICENSE b/LICENSE
new file mode 100644
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,165 @@
+                  GNU LESSER GENERAL PUBLIC LICENSE
+                       Version 3, 29 June 2007
+
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diff --git a/Setup.hs b/Setup.hs
new file mode 100644
--- /dev/null
+++ b/Setup.hs
@@ -0,0 +1,2 @@
+import Distribution.Simple
+main = defaultMain
diff --git a/delta.cabal b/delta.cabal
new file mode 100644
--- /dev/null
+++ b/delta.cabal
@@ -0,0 +1,102 @@
+-- Initial delta.cabal generated by cabal init.  For further documentation,
+--  see http://haskell.org/cabal/users-guide/
+
+-- The name of the package.
+name:                delta
+
+-- The package version.  See the Haskell package versioning policy (PVP) 
+-- for standards guiding when and how versions should be incremented.
+-- http://www.haskell.org/haskellwiki/Package_versioning_policy
+-- PVP summary:      +-+------- breaking API changes
+--                   | | +----- non-breaking API additions
+--                   | | | +--- code changes with no API change
+version:             0.1.0.0
+
+-- A short (one-line) description of the package.
+synopsis:            A library for detecting file changes
+
+-- A longer description of the package.
+description:         Delta is a library for detecting file changes in any given
+                     directory. The package is written using the sodium FRP library
+                     but it also provides a callback based API.
+
+                     The project also contains an executable, delta-cli which
+                     runs on the command line and prints detected changes to stdout.
+
+-- URL for the project homepage or repository.
+homepage:            https://github.com/kryoxide/delta
+
+-- The license under which the package is released.
+license:             LGPL-3
+
+-- The file containing the license text.
+license-file:        LICENSE
+
+-- The package author(s).
+author:              Christof Schramm
+
+-- An email address to which users can send suggestions, bug reports, and 
+-- patches.
+maintainer:          christof.schramm@campus.lmu.de
+
+-- A copyright notice.
+-- copyright:           
+
+category:            Data
+
+build-type:          Simple
+
+-- Extra files to be distributed with the package, such as examples or a 
+-- README.
+-- extra-source-files:  
+
+-- Constraint on the version of Cabal needed to build this package.
+cabal-version:       >=1.16
+
+source-repository head
+  type:              git
+  location:          https://github.com/kryoxide/delta/
+
+library
+  -- Modules exported by the library.
+  exposed-modules:     System.Delta.Base
+                     , System.Delta.Poll
+                     , System.Delta.Callback
+                     , System.Delta.Class
+                     , System.Delta
+  -- Modules included in this library but not exported.
+  -- other-modules:       
+  
+  -- LANGUAGE extensions used by modules in this package.
+  -- other-extensions:    
+  
+  -- Other library packages from which modules are imported.
+  build-depends:       base >=4.6 && <4.9
+                     , containers >= 0.5
+                     , directory >= 1.2
+                     , filepath >= 1.3
+                     , time >= 1.5
+                     , sodium >= 0.11
+                     , fs-events
+  
+  -- Directories containing source files.
+  hs-source-dirs:      src
+  
+  -- Base language which the package is written in.
+  default-language:    Haskell2010
+
+executable delta-cli
+
+  build-depends:       base >= 4.8 && < 4.9
+                     , containers >= 0.5
+                     , directory >= 1.2
+                     , filepath >= 1.3
+                     , time >= 1.5
+                     , sodium >= 0.11
+                     , delta
+
+  hs-source-dirs:      src/delta-cli
+
+  main-is:             Main.hs
+
+  default-language:    Haskell2010
diff --git a/src/System/Delta.hs b/src/System/Delta.hs
new file mode 100644
--- /dev/null
+++ b/src/System/Delta.hs
@@ -0,0 +1,24 @@
+{-# LANGUAGE RankNTypes #-}
+module System.Delta ( module System.Delta.Base
+                    , module System.Delta.Poll
+                    , module System.Delta.Class
+                    , module System.Delta.Callback
+                    , deltaDir
+                    , deltaDirWithCallbacks
+                    )where
+
+import System.Delta.Base
+import System.Delta.Poll
+import System.Delta.Class
+import System.Delta.Callback
+
+-- | Build a file watcher
+deltaDir :: (FileWatcher a) => FilePath -> IO a
+deltaDir path = defaultWatcher path >>= return . watcherId
+
+-- | Build a file watcher that allows to register callbacks
+deltaDirWithCallbacks :: (FileWatcher a) => FilePath -> IO (CallbackWatcher a)
+deltaDirWithCallbacks path = deltaDir path >>= withCallbacks
+
+watcherId :: (FileWatcher a) => a -> a
+watcherId a = a
diff --git a/src/System/Delta/Base.hs b/src/System/Delta/Base.hs
new file mode 100644
--- /dev/null
+++ b/src/System/Delta/Base.hs
@@ -0,0 +1,28 @@
+module System.Delta.Base where
+
+import System.IO.Error
+import System.FilePath
+import System.Directory
+import Data.Time.Clock.POSIX
+
+newtype FileInfo = FileInfo (FilePath,Integer,Bool)
+                 deriving (Ord,Eq,Show)
+
+fileInfoPath :: FileInfo -> FilePath
+fileInfoPath (FileInfo (path,_,_)) = path
+
+-- | File modification time in milliseconds
+fileInfoTimestamp :: FileInfo -> Integer
+fileInfoTimestamp (FileInfo (_,time,_)) = time
+
+-- | Is the file a directory
+fileInfoIsDir :: FileInfo -> Bool
+fileInfoIsDir (FileInfo (_,_,dir)) = dir
+
+mkFileInfo :: FilePath -> IO (FileInfo)
+mkFileInfo path  = do
+  isDir  <- doesDirectoryExist path
+  isFile <- doesFileExist path
+  modTime <- getModificationTime path
+  let timeMillis = 1000 * (floor $ utcTimeToPOSIXSeconds modTime)
+  return $ FileInfo (path, timeMillis, isDir)
diff --git a/src/System/Delta/Callback.hs b/src/System/Delta/Callback.hs
new file mode 100644
--- /dev/null
+++ b/src/System/Delta/Callback.hs
@@ -0,0 +1,115 @@
+{-# LANGUAGE GADTs #-}
+module System.Delta.Callback ( CallbackWatcher
+                             , CallbackId
+                               
+                             -- * Construction
+                             , withCallbacks
+                               
+                             -- * Adding callbacks
+                             , withDeleteCallback
+                             , withChangedCallback
+                             , withNewCallback
+
+                             -- * Removing callbacks
+                             , unregisterCallback
+                             , removeAllCallbacks
+
+                             -- * Closing the watcher
+                             , closeCallbackWatcher
+                             )where
+
+import FRP.Sodium
+import System.Delta.Base
+import System.Delta.Class
+
+import qualified Data.Map as M
+
+import Control.Concurrent.MVar
+
+newtype CallbackId = CallbackId Integer
+                   deriving (Eq, Ord)  
+
+data CallbackWatcher w where
+  CallbackWatcher :: FileWatcher w => {
+    baseWatcher :: w
+  , nextCallbackId :: MVar CallbackId
+  , watcherCallbacks :: MVar (M.Map CallbackId (IO ()))
+  } -> CallbackWatcher w
+
+
+-- | Raise the callback id of a callback watcher
+raiseId :: CallbackWatcher w -> IO (CallbackId)
+raiseId w = do
+  (CallbackId n) <- takeMVar $ nextCallbackId w
+  putMVar (nextCallbackId w) (CallbackId $ n+1)
+  return (CallbackId n)
+
+-- | Add an action to unregister a callback
+addCallbackUnregister :: CallbackWatcher w -> IO () -> IO CallbackId
+addCallbackUnregister w removeCallback = do
+  newId <- raiseId w
+  mp <- takeMVar $ watcherCallbacks w
+  putMVar (watcherCallbacks w) (M.insert newId removeCallback mp)
+  return newId
+  
+-- | Wrap a file watcher in a datatype that allows adding callbacks
+withCallbacks :: (FileWatcher a) => a -> IO (CallbackWatcher a)
+withCallbacks w = do
+  nextIdVar <- newMVar (CallbackId 0)
+  callbacks <- newMVar (M.empty)
+  return $ CallbackWatcher w nextIdVar callbacks
+
+-- | Add a callback that is executed when file deletion is detected
+withDeleteCallback :: (FileWatcher a)
+                      => CallbackWatcher a
+                        -> (FilePath -> IO ()) -- ^ An IO action on the deleted path
+                        -> IO (CallbackId)
+withDeleteCallback watcher action = do
+  unregisterCallback <- callbackOnEvent (deletedFiles $ baseWatcher watcher) action
+  addCallbackUnregister watcher unregisterCallback
+
+-- | Add a callback that is executed when file creation is detected
+withNewCallback :: (FileWatcher a)
+                      => CallbackWatcher a
+                        -> (FilePath -> IO ()) -- ^ An IO action on the new path
+                        -> IO (CallbackId)
+withNewCallback watcher action = do
+  unregisterCallback <- callbackOnEvent (newFiles $ baseWatcher watcher) action
+  addCallbackUnregister watcher unregisterCallback
+
+-- | Add a callback on a changed file
+withChangedCallback :: (FileWatcher a)
+                      => CallbackWatcher a
+                        -> (FileInfo -> IO ()) -- ^ Action on changed file
+                        -> IO (CallbackId)
+withChangedCallback watcher action = do
+  unregisterCallback <- callbackOnEvent (changedFiles $ baseWatcher watcher) action
+  addCallbackUnregister watcher unregisterCallback
+
+-- | Unregister the given CallbackId from the FileWatcher
+-- does nothing if the CallbackId is not in the watcher
+unregisterCallback :: (FileWatcher a) => CallbackWatcher a -> CallbackId -> IO ()
+unregisterCallback watcher cId = do
+  mp <- takeMVar $ watcherCallbacks watcher
+  case M.lookup cId mp of
+    Nothing -> return ()
+    Just action -> action
+  putMVar (watcherCallbacks watcher) (M.delete cId mp)
+
+-- | Remove all callbacks form the watcher. They will not be called after this
+removeAllCallbacks :: (FileWatcher a) => CallbackWatcher a -> IO ()
+removeAllCallbacks watcher = do
+  mp <- takeMVar $ watcherCallbacks watcher
+  putMVar (watcherCallbacks watcher) M.empty
+  sequence_ (M.elems mp)
+
+-- | Remove all callbacks and close the underlying FileWatcher
+closeCallbackWatcher :: FileWatcher a => CallbackWatcher a -> IO ()
+closeCallbackWatcher watcher = do
+  removeAllCallbacks watcher
+  cleanUpAndClose $ baseWatcher watcher
+  
+
+-- | Add a listener to an event, return the action to unregister the listener
+callbackOnEvent :: Event a -> (a -> IO ()) -> IO (IO ())
+callbackOnEvent e action = sync $ listen e action
diff --git a/src/System/Delta/Class.hs b/src/System/Delta/Class.hs
new file mode 100644
--- /dev/null
+++ b/src/System/Delta/Class.hs
@@ -0,0 +1,23 @@
+module System.Delta.Class where
+
+import FRP.Sodium
+import System.Delta.Base
+
+class FileWatcher a where
+  -- | Each type provides a default watcher for a pass
+  defaultWatcher  :: FilePath -> IO a
+
+  -- | An event that gives some info on changed files (disjunct from
+  -- deleted and new files)
+  changedFiles    :: a -> Event FileInfo
+
+  -- | An event that fires for each new file
+  newFiles        :: a -> Event FilePath
+
+  -- | An event that fires for each deleted path
+  deletedFiles    :: a -> Event FilePath
+
+  -- | Free all possibly used resources. No event will fire after
+  -- this.
+  cleanUpAndClose :: a -> IO ()
+
diff --git a/src/System/Delta/Poll.hs b/src/System/Delta/Poll.hs
new file mode 100644
--- /dev/null
+++ b/src/System/Delta/Poll.hs
@@ -0,0 +1,112 @@
+module System.Delta.Poll ( PollWatcher
+                         , createPollWatcher
+                         )where
+
+import Control.Applicative ((<$>))
+import Control.Concurrent
+import Control.Monad (foldM)
+
+import qualified Data.Map as M
+import Data.Maybe (catMaybes)
+
+import FRP.Sodium
+
+import System.Delta.Base
+import System.Delta.Class
+
+import System.Directory
+import System.FilePath
+
+data PollWatcher = PollWatcher
+                     FilePath
+                     (Event FileInfo)
+                     (Event FilePath)
+                     (Event FilePath)
+                     ThreadId
+
+instance FileWatcher PollWatcher where
+  defaultWatcher = createPollWatcher 15
+  changedFiles (PollWatcher _ e _ _ _) = e
+  newFiles     (PollWatcher _ _ e _ _) = e
+  deletedFiles (PollWatcher _ _ _ e _) = e
+  cleanUpAndClose (PollWatcher _ _ _ _ tId) = killThread tId
+
+-- | Watch files in this directory recursively for changes every
+-- n seconds.
+createPollWatcher :: Int      -- ^ seconds interval
+                  -> FilePath -- ^ path to watch
+                  -> IO PollWatcher
+createPollWatcher secs path = do
+  (changedEvent, pushChanged) <- sync $ newEvent
+  (deletedEvent, pushDeleted) <- sync $ newEvent
+  (newFileEvent, pushNewFile) <- sync $ newEvent
+  watcherId <- startWatchThread path pushNewFile pushDeleted pushChanged secs
+  return $ PollWatcher path changedEvent newFileEvent deletedEvent watcherId
+
+-- | Recursively traverse a folder, follow symbolic links but don't
+-- visit a file twice.
+recursiveDescent path = recursiveDescent' M.empty path
+
+-- | Recursively traverse a folder, follows symbolic links,
+-- doesn't loop however.
+recursiveDescent' :: M.Map FilePath FileInfo
+                  -> FilePath
+                  -> IO (M.Map FilePath FileInfo)
+recursiveDescent' visited path | M.member path visited = return visited
+recursiveDescent' visited path = do
+  isDir  <- doesDirectoryExist path
+  inf <- mkFileInfo path
+  let visitedWithCurrent = M.insert path inf visited
+  if not isDir
+  then return $ visitedWithCurrent
+  else do
+    contentsUnfiltered <- getDirectoryContents path
+    let contentsFiltered = filter (\x -> x /= "." && x /= "..") contentsUnfiltered
+        contentsAbs = (combine path) <$> contentsFiltered
+    foldM recursiveDescent' visitedWithCurrent contentsAbs
+
+
+-- | List all files that have a larger modification time in the second
+-- map than in the first
+diffChangedFiles :: M.Map FilePath FileInfo 
+             -> M.Map FilePath FileInfo
+             -> [FileInfo]
+diffChangedFiles before after =
+  catMaybes . M.elems $ M.intersectionWith f before after
+  where
+    f beforeInfo afterInfo =
+      if fileInfoTimestamp beforeInfo < fileInfoTimestamp afterInfo
+      then Just afterInfo
+      else Nothing
+
+-- | List all files that occur in the second map but not the first
+diffNewFiles :: M.Map FilePath FileInfo
+             -> M.Map FilePath FileInfo
+             -> [FileInfo]
+diffNewFiles before after = M.elems $ M.difference after before
+
+-- | List all files that occur in the first map but not the second
+diffDeletedFiles :: M.Map FilePath FileInfo
+                 -> M.Map FilePath FileInfo
+                 -> [FileInfo]
+diffDeletedFiles before after = M.elems $ M.difference before after
+
+-- | Fork a thread that continuously polls the given paht and compares
+-- the results of two polls.
+startWatchThread :: FilePath
+                 -> (FilePath -> Reactive ()) -- ^ Push new files / dirs
+                 -> (FilePath -> Reactive ()) -- ^ Push deleted files / dirs
+                 -> (FileInfo -> Reactive ()) -- ^ Push changed files / dirs
+                 -> Int -- ^ Seconds between polls
+                 -> IO ThreadId
+startWatchThread path pushNew pushDeleted pushChanged secs = do
+  curr <- recursiveDescent path
+  forkIO $ go curr
+  where
+    go last = do
+      threadDelay $ secs * 1000 * 1000
+      curr <- recursiveDescent path
+      sync $ mapM_ (pushChanged) (diffChangedFiles last curr)
+      sync $ mapM_ (pushNew    ) (fileInfoPath <$> diffNewFiles last curr)
+      sync $ mapM_ (pushDeleted) (fileInfoPath <$> diffDeletedFiles last curr)
+      go curr
diff --git a/src/delta-cli/Main.hs b/src/delta-cli/Main.hs
new file mode 100644
--- /dev/null
+++ b/src/delta-cli/Main.hs
@@ -0,0 +1,24 @@
+module Main where
+
+import System.Delta
+import System.Environment
+
+import Control.Monad
+import Control.Concurrent
+
+main = do
+  args <- getArgs
+  case args of
+    [path] -> do
+                watcher <- createPollWatcher 1 path >>= withCallbacks
+                withNewCallback watcher (\x -> putStrLn $ "new:\t" ++ x)
+                withDeleteCallback watcher (\x -> putStrLn $ "del:\t" ++ x)
+                withChangedCallback watcher (\(FileInfo(x,_,_)) ->
+                                              putStrLn $ "changed:\t" ++ x
+                                            )
+                forever $ threadDelay (1000 * 1000)
+    _      -> putStrLn errorString
+
+errorString = "This is a simple command line interface to the delta\
+              \library. Call the program with delta-cli <path>, where path\
+              \is the path of the folder / file you want to watch."