simple localstorage api

fixes #1

src/Bonsai/DOM.purs

@@ -34,6 +34,7 @@ module Bonsai.DOM
   , appendChild
   , addEventListener
   , clearElement
+  , defaultView
   , document
   , elementById
   , focusElement

src/Bonsai/Storage.js

@@ -0,0 +1,7 @@
+"use strict";
+
+exports.primitives =
+    { getItem: function (k, win) { return win.localStorage.getItem(k); }
+    , setItem: function (k, v, win) { win.localStorage.setItem(k, v); }
+    , removeItem: function (k, win) { win.localStorage.removeItem(k); }
+    };

src/Bonsai/Storage.purs

@@ -0,0 +1,31 @@
+-- | Wrapper for window.localStorage
+module Bonsai.Storage where
+
+import Prelude
+
+import Bonsai.DOM (Window(..))
+import Data.Function.Uncurried (Fn2, Fn3, runFn2, runFn3)
+import Data.Maybe (Maybe(..), maybe)
+import Foreign (F, Foreign, readNullOrUndefined, readString)
+
+foreign import primitives
+  :: { getItem :: Fn2 String Foreign Foreign
+     , setItem :: Fn3 String String Foreign Unit
+     , removeItem :: Fn2 String Foreign Unit}
+
+-- | Get a string value for the the key from storage.
+getItem :: String -> Window -> F (Maybe String)
+getItem key (Window win) = do
+  runFn2 primitives.getItem key win #
+  readNullOrUndefined >>=
+  maybe (pure Nothing) (map Just <<< readString)
+
+-- | Put the string value at key into the store
+setItem :: String -> String -> Window -> F Unit
+setItem key val (Window win) =
+  pure $ runFn3 primitives.setItem key val win
+
+-- | Remove the key from the store
+removeItem :: String -> Window -> F Unit
+removeItem key (Window win) =
+  pure $ runFn2 primitives.removeItem key win