Add ifElse splice functions

src/Heist/Splices.hs

@@ -1,6 +1,8 @@
 module Heist.Splices
   ( ifISplice
   , ifCSplice
+  , ifElseISplice
+  , ifElseCSplice
   , module Heist.Splices.Apply
   , module Heist.Splices.Bind
   , module Heist.Splices.Cache
@@ -19,6 +21,7 @@ import           Heist.Splices.Html
 import           Heist.Splices.Ignore
 import           Heist.Splices.Markdown
 import           Heist.Internal.Types.HeistState
+import qualified Text.XmlHtml as X
 
 ------------------------------------------------------------------------------
 -- | Run the splice contents if given condition is True, make splice disappear
@@ -47,3 +50,23 @@ ifCSplice predicate runtime = do
           else
             return mempty
 
+
+------------------------------------------------------------------------------
+-- | Implements an if/then/else conditional splice.  It splits its children
+-- around the <else/> element to get the markup to be used for the two cases.
+ifElseISplice :: Monad m => Bool -> I.Splice m
+ifElseISplice cond = getParamNode >>= (rewrite . X.childNodes)
+  where
+    rewrite nodes = 
+      let (ns, ns') = break (\n -> X.tagName n==Just "else") nodes
+      in I.runNodeList $ if cond then ns else (drop 1 ns') 
+
+
+------------------------------------------------------------------------------
+-- | Implements an if/then/else conditional splice.  It splits its children
+-- around the <else/> element to get the markup to be used for the two cases.
+ifElseCSplice :: Monad m => Bool -> C.Splice m
+ifElseCSplice cond = getParamNode >>= (rewrite . X.childNodes)
+  where rewrite nodes = 
+          let (ns, ns') = break (\n -> X.tagName n==Just "else") nodes
+          in C.runNodeList $ if cond then ns else (drop 1 ns')