Added streaming demo

demo/streaming/streaming.hs

@@ -0,0 +1,48 @@
+{-# LANGUAGE OverloadedStrings, TemplateHaskell, QuasiQuotes, TypeFamilies #-}
+import Yesod.Core
+import Data.Conduit
+import qualified Data.Conduit.Binary as CB
+import Control.Concurrent.Lifted (threadDelay)
+import Data.Monoid ((<>))
+import qualified Data.Text as T
+import Control.Monad (forM_)
+
+data App = App
+
+mkYesod "App" [parseRoutes|
+/ HomeR GET
+|]
+
+instance Yesod App
+
+fibs :: [Int]
+fibs = 1 : 1 : zipWith (+) fibs (tail fibs)
+
+getHomeR :: Handler TypedContent
+getHomeR = do
+    value <- lookupGetParam "x"
+    case value of
+        Just "file" -> respondSource typePlain $ do
+            sendChunkText "Going to read a file\n\n"
+            CB.sourceFile "streaming.hs" $= awaitForever sendChunkBS
+            sendChunkText "Finished reading the file\n"
+        Just "fibs" -> respondSource typePlain $ do
+            forM_ fibs $ \fib -> do
+                $logError $ "Got fib: " <> T.pack (show fib)
+                sendChunkText $ "Next fib is: " <> T.pack (show fib) <> "\n"
+                yield Flush
+                sendFlush
+                threadDelay 1000000
+        _ -> fmap toTypedContent $ defaultLayout $ do
+            setTitle "Streaming"
+            [whamlet|
+                <p>Notice how in the code above we perform selection before starting the stream.
+                <p>Anyway, choose one of the options below.
+                <ul>
+                    <li>
+                        <a href=?x=file>Read a file
+                    <li>
+                        <a href=?x=fibs>See the fibs
+            |]
+
+main = warp 3000 App