Add SSE example

lib/examples/tick/Main.hs

@@ -0,0 +1,44 @@
+{-# LANGUAGE BlockArguments #-}
+{-# LANGUAGE DataKinds #-}
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE TypeApplications #-}
+
+module Main where
+
+import qualified Control.Concurrent as Concurrent
+import qualified Control.Concurrent.Chan as Chan
+import Control.Monad
+import qualified Data.Binary.Builder as Builder
+import qualified Data.Text as Text
+import qualified Network.HTTP.Types as HTTP
+import qualified Network.Wai as Wai
+import qualified Network.Wai.EventSource as Wai
+import qualified Network.Wai.Handler.Warp as Warp
+import Okapi.App
+import Okapi.Response
+import qualified Web.HttpApiData as Web
+
+ticker :: Chan.Chan Wai.ServerEvent -> Node '[]
+ticker source =
+    choice
+        [ lit "connect" $ events source
+        ]
+
+tick source = do
+    let event =
+            Wai.ServerEvent
+                { Wai.eventName = Nothing
+                , Wai.eventId = Nothing
+                , Wai.eventData = [Builder.putStringUtf8 "tick"]
+                }
+    forever do
+        Concurrent.threadDelay (1 * (10 ^ 6))
+        print "Sending"
+        Chan.writeChan source event
+
+main = do
+    source <- Chan.newChan
+    Concurrent.forkIO $ tick source
+    Warp.run 8003
+        . withDefault (ticker source)
+        $ \_ resp -> resp $ Wai.responseLBS HTTP.status404 [] "Not Found..."

lib/okapi.cabal

@@ -110,6 +110,23 @@ executable bookstore
   ghc-options: -threaded -rtsopts -with-rtsopts=-N
   default-language:    Haskell2010
 
+executable tick
+  main-is:             Main.hs
+  hs-source-dirs:
+      examples/tick
+  build-depends:
+      base
+    , okapi
+    , warp
+    , wai
+    , text
+    , http-api-data
+    , http-types
+    , wai-extra
+    , binary
+  ghc-options: -threaded -rtsopts -with-rtsopts=-N
+  default-language:    Haskell2010
+
 test-suite okapi-test
   type: exitcode-stdio-1.0
   main-is: Spec.hs