diff --git a/LICENSE b/LICENSE
new file mode 100644
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,30 @@
+Copyright (c) 2016, Sönke Hahn
+
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+    * Redistributions of source code must retain the above copyright
+      notice, this list of conditions and the following disclaimer.
+
+    * Redistributions in binary form must reproduce the above
+      copyright notice, this list of conditions and the following
+      disclaimer in the documentation and/or other materials provided
+      with the distribution.
+
+    * Neither the name of Sönke Hahn nor the names of other
+      contributors may be used to endorse or promote products derived
+      from this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
diff --git a/Setup.hs b/Setup.hs
new file mode 100644
--- /dev/null
+++ b/Setup.hs
@@ -0,0 +1,3 @@
+#!/usr/bin/env runhaskell
+import Distribution.Simple
+main = defaultMain
diff --git a/src/Network/Wai/MakeAssets.hs b/src/Network/Wai/MakeAssets.hs
new file mode 100644
--- /dev/null
+++ b/src/Network/Wai/MakeAssets.hs
@@ -0,0 +1,63 @@
+{-# LANGUAGE TemplateHaskell #-}
+{-# LANGUAGE TupleSections #-}
+
+module Network.Wai.MakeAssets (serveAssets) where
+
+import           Control.Concurrent
+import           Control.Exception
+import           Control.Monad
+import           Data.List (intercalate)
+import           Data.Monoid
+import           Data.String.Conversions
+import           Development.Shake (cmd, Exit(..), Stderr(..), CmdOption(..))
+import           Network.HTTP.Types.Status
+import           Network.Wai
+import           Network.Wai.Application.Static
+import           System.Directory
+import           System.Exit
+
+serveAssets :: IO Application
+serveAssets = do
+  startupChecks
+  let fileApp = staticApp $ defaultFileServerSettings "assets/"
+  mvar <- newMVar ()
+  return $ \ request respond -> do
+    (Exit exitCode, Stderr errs) <- synchronize mvar $
+      cmd (Cwd "client") "make"
+    case exitCode of
+      ExitSuccess -> fileApp request respond
+      ExitFailure _ -> respond $ responseLBS internalServerError500 [] $
+        cs "make error:\n" <> errs
+
+synchronize :: MVar () -> IO a -> IO a
+synchronize mvar action = modifyMVar mvar $ \ () -> ((), ) <$> action
+
+startupChecks :: IO ()
+startupChecks = do
+  checkExists Dir "client/" $
+    "You should put sources for assets in there."
+  checkExists File "client/Makefile" $ unwords $
+    "Which will be invoked to build the assets." :
+    "It should put compiled assets into 'assets/'." :
+    []
+  checkExists Dir "assets/" $
+    "All files in 'assets/' will be served."
+
+data FileType
+  = File
+  | Dir
+
+checkExists :: FileType -> FilePath -> String -> IO ()
+checkExists typ path hint = do
+  exists <- (isFile doesFileExist doesDirectoryExist) path
+  when (not exists) $ do
+    throwIO $ ErrorCall $ intercalate "\n" $
+      ("missing " ++ isFile "file" "directory" ++ ": '" ++ path ++ "'") :
+      ("Please create '" ++ path ++ "'.") :
+      ("(" ++ hint ++ ")") :
+      []
+  where
+    isFile :: a -> a -> a
+    isFile a b = case typ of
+      File -> a
+      Dir -> b
diff --git a/src/wai-make-assets.hs b/src/wai-make-assets.hs
new file mode 100644
--- /dev/null
+++ b/src/wai-make-assets.hs
@@ -0,0 +1,24 @@
+{-# LANGUAGE DeriveGeneric #-}
+
+import           Network.Wai.Handler.Warp
+import           System.IO
+import           WithCli
+
+import           Network.Wai.MakeAssets
+
+data Args
+  = Args {
+    port :: Int
+  }
+  deriving (Generic)
+
+instance HasArguments Args
+
+main :: IO ()
+main = withCliModified [AddShortOption "port" 'p'] $ \ (Args port) -> do
+  let settings =
+        setPort port $
+        setBeforeMainLoop (hPutStrLn stderr
+          ("listening to " ++ show port ++ "...")) $
+        defaultSettings
+  runSettings settings =<< serveAssets
diff --git a/test/Network/Wai/MakeAssetsSpec.hs b/test/Network/Wai/MakeAssetsSpec.hs
new file mode 100644
--- /dev/null
+++ b/test/Network/Wai/MakeAssetsSpec.hs
@@ -0,0 +1,92 @@
+{-# LANGUAGE OverloadedStrings #-}
+
+module Network.Wai.MakeAssetsSpec where
+
+import           Control.Exception
+import           Control.Lens
+import           Data.ByteString.Lazy (isPrefixOf)
+import           Data.List (intercalate)
+import           Network.Wai.Handler.Warp
+import           Network.Wreq
+import           System.Directory
+import           System.IO.Silently
+import           Test.Hspec
+import           Test.Mockery.Directory
+
+import           Network.Wai.MakeAssets
+
+spec :: Spec
+spec = do
+  around_ silence $ do
+    describe "serverClient" $ do
+      it "returns static files" $ do
+        inTempDirectory $ do
+          createDirectoryIfMissing True "client"
+          createDirectoryIfMissing True "assets"
+          writeFile "assets/foo" "bar"
+          writeFile "client/Makefile" "all:\n\ttrue"
+          testWithApplication serveAssets $ \ port -> do
+            let url = "http://localhost:" ++ show port ++ "/foo"
+            response <- get url
+            response ^. responseBody `shouldBe` "bar"
+
+      it "runs 'make' in 'client/' before answering requests" $ do
+        inTempDirectory $ do
+          createDirectoryIfMissing True "client"
+          createDirectoryIfMissing True "assets"
+          writeFile "client/Makefile" "all:\n\techo bar > ../assets/foo"
+          testWithApplication serveAssets $ \ port -> do
+            let url = "http://localhost:" ++ show port ++ "/foo"
+            response <- get url
+            response ^. responseBody `shouldBe` "bar\n"
+
+      it "returns the error messages in case 'make' fails" $ do
+        inTempDirectory $ do
+          createDirectoryIfMissing True "client"
+          createDirectoryIfMissing True "assets"
+          writeFile "client/Makefile" "all:\n\t>&2 echo error message ; false"
+          testWithApplication serveAssets $ \ port -> do
+            let url = "http://localhost:" ++ show port ++ "/foo"
+            response <- getWith acceptErrors url
+            let body = response ^. responseBody
+            body `shouldSatisfy` ("make error:\nerror message\n" `isPrefixOf`)
+
+      context "complains about missing files or directories" $ do
+        it "missing client/" $ do
+          inTempDirectory $ do
+            createDirectoryIfMissing True "assets"
+            let expected = intercalate "\n" $
+                  "missing directory: 'client/'" :
+                  "Please create 'client/'." :
+                  "(You should put sources for assets in there.)" :
+                  []
+            testWithApplication serveAssets (\ _ -> return ())
+              `shouldThrow` errorCall expected
+
+        it "missing client/Makefile" $ do
+          inTempDirectory $ do
+            createDirectoryIfMissing True "client"
+            createDirectoryIfMissing True "assets"
+            let expected = intercalate "\n" $
+                  "missing file: 'client/Makefile'" :
+                  "Please create 'client/Makefile'." :
+                  "(Which will be invoked to build the assets. It should put compiled assets into 'assets/'.)" :
+                  []
+            testWithApplication serveAssets (\ _ -> return ())
+              `shouldThrow` errorCall expected
+
+        it "missing assets/" $ do
+          inTempDirectory $ do
+            touch "client/Makefile"
+            let expected = intercalate "\n" $
+                  "missing directory: 'assets/'" :
+                  "Please create 'assets/'." :
+                  "(All files in 'assets/' will be served.)" :
+                  []
+            catch (testWithApplication serveAssets (\ _ -> return ())) $
+              \ (ErrorCall message) -> do
+                message `shouldBe` expected
+
+acceptErrors :: Options
+acceptErrors = defaults &
+  checkStatus .~ Just (\ _ _ _ -> Nothing)
diff --git a/test/Spec.hs b/test/Spec.hs
new file mode 100644
--- /dev/null
+++ b/test/Spec.hs
@@ -0,0 +1,1 @@
+{-# OPTIONS_GHC -F -pgmF hspec-discover #-}
diff --git a/wai-make-assets.cabal b/wai-make-assets.cabal
new file mode 100644
--- /dev/null
+++ b/wai-make-assets.cabal
@@ -0,0 +1,82 @@
+-- This file has been generated from package.yaml by hpack version 0.14.0.
+--
+-- see: https://github.com/sol/hpack
+
+name:           wai-make-assets
+version:        0.1
+synopsis:       Compiling and serving assets
+description:    Small wai library and command line tool for compiling and serving assets (e.g. through ghcjs, elm, sass)
+category:       Development
+homepage:       https://github.com/soenkehahn/wai-make-assets#readme
+bug-reports:    https://github.com/soenkehahn/wai-make-assets/issues
+maintainer:     SoenkeHahn@gmail.com
+license:        BSD3
+license-file:   LICENSE
+build-type:     Simple
+cabal-version:  >= 1.10
+
+source-repository head
+  type: git
+  location: https://github.com/soenkehahn/wai-make-assets
+
+library
+  hs-source-dirs:
+      src
+  build-depends:
+      base < 99
+    , wai-app-static
+    , wai
+    , warp
+    , string-conversions
+    , bytestring
+    , shake
+    , http-types
+    , directory
+  exposed-modules:
+      Network.Wai.MakeAssets
+  default-language: Haskell2010
+
+executable wai-make-assets
+  main-is: wai-make-assets.hs
+  hs-source-dirs:
+      src
+  build-depends:
+      base < 99
+    , wai-app-static
+    , wai
+    , warp
+    , string-conversions
+    , bytestring
+    , shake
+    , http-types
+    , directory
+    , getopt-generics
+  other-modules:
+      Network.Wai.MakeAssets
+  default-language: Haskell2010
+
+test-suite spec
+  type: exitcode-stdio-1.0
+  main-is: Spec.hs
+  hs-source-dirs:
+      test
+    , src
+  build-depends:
+      base < 99
+    , wai-app-static
+    , wai
+    , warp
+    , string-conversions
+    , bytestring
+    , shake
+    , http-types
+    , directory
+    , hspec
+    , wreq
+    , mockery
+    , lens
+    , silently
+  other-modules:
+      Network.Wai.MakeAssetsSpec
+      Network.Wai.MakeAssets
+  default-language: Haskell2010