add multiple channels example

yesod-websockets/chat-with-multiple-channels.hs

@@ -0,0 +1,122 @@
+{-# LANGUAGE QuasiQuotes, TemplateHaskell, TypeFamilies, OverloadedStrings #-}
+import Yesod.Core
+import Yesod.WebSockets
+import qualified Data.Text.Lazy as TL
+import Control.Monad (forever)
+import Control.Monad.Trans.Reader
+import Control.Concurrent (threadDelay)
+import Data.Time
+import Conduit
+import Data.Monoid ((<>))
+import Control.Concurrent.STM.Lifted
+import Data.Text (Text)
+import qualified Data.Map as M
+
+data App = App (TVar (M.Map Text (TChan Text)))
+
+instance Yesod App
+
+mkYesod "App" [parseRoutes|
+/ HomeR GET
+|]
+
+chatApp :: WebSocketsT Handler ()
+chatApp = do
+    sendTextData ("Welcome to the chat server, please enter your name." :: Text)
+    name <- receiveData
+    sendTextData $ "Welcome, " <> name <> ". Please enter your channel ID"
+    channelId <- receiveData
+    sendTextData $ name <> " just joined " <> channelId
+
+    App channelMapTVar <- getYesod
+
+    channelMap <- readTVarIO channelMapTVar
+
+    let maybeChan = M.lookup channelId channelMap
+
+    writeChan <- atomically $ case maybeChan of
+                                Nothing -> do
+                                    chan <- newBroadcastTChan
+                                    writeTVar channelMapTVar $ M.insert channelId chan channelMap
+                                    return chan
+                                Just writeChan -> return writeChan
+
+    readChan <- atomically $ do
+        writeTChan writeChan $ name <> " has joined the chat"
+        dupTChan writeChan
+    race_
+        (forever $ atomically (readTChan readChan) >>= sendTextData)
+        (sourceWS $$ mapM_C (\msg ->
+            atomically $ writeTChan writeChan $ name <> ": " <> msg))
+
+getHomeR :: Handler Html
+getHomeR = do
+    webSockets chatApp
+    defaultLayout $ do
+        [whamlet|
+            <div #output>
+            <form #form>
+                <input #input autofocus>
+        |]
+        toWidget [lucius|
+            \#output {
+                width: 600px;
+                height: 400px;
+                border: 1px solid black;
+                margin-bottom: 1em;
+                p {
+                    margin: 0 0 0.5em 0;
+                    padding: 0 0 0.5em 0;
+                    border-bottom: 1px dashed #99aa99;
+                }
+            }
+            \#input {
+                width: 600px;
+                display: block;
+            }
+        |]
+        toWidget [julius|
+            var url = document.URL,
+                output = document.getElementById("output"),
+                form = document.getElementById("form"),
+                input = document.getElementById("input"),
+                conn;
+
+            url = url.replace("http:", "ws:").replace("https:", "wss:");
+            conn = new WebSocket(url);
+
+            conn.onmessage = function(e) {
+                var p = document.createElement("p");
+                p.appendChild(document.createTextNode(e.data));
+                output.appendChild(p);
+            };
+/* ******************************************************************************************************* 
+The following code demonstrates one way to prevent timeouts. The "if" test is added to prevent chat participants from getting the ping message “dcba” every twenty seconds. It also prevents participants from receiving any message ending with “dcba” sent by any chat participant. “ e.data.split("").reverse().join("").substring(0,4)” changes, for example, “user:abc123dcba” to “abcd321cba:resu” and grabs the first four characters; i.e., “abcd”. Messages are broadcast only if the last four characters are not “dcba”. Note that the variable "t" controls the length of the timeout period. t = 3 allows one minute of inactivity. t = 30 allows ten minutes, and t = 180 allows an hour. The value inserted below is 360 (2 hours).
+*/
+            conn.onmessage = function(e) {
+                var p = document.createElement("p");
+                p.appendChild(document.createTextNode(e.data));
+                if (e.data.split("").reverse().join("").substring(0,4) != "abcd") {
+                    output.appendChild(p);
+                }   
+            };
+            var t = 360                                 
+            setInterval (function () {
+            	t = t - 1;
+            	if (t > 0) 
+            	{
+                  conn.send("dcba");
+                }
+            }, 20000);
+/* ****************************************************************************************************** */
+            form.addEventListener("submit", function(e){
+                conn.send(input.value);
+                input.value = "";
+                e.preventDefault();
+            });
+        |]
+
+main :: IO ()
+main = do
+    channelMapTVar <- newTVarIO M.empty
+    warp 3000 $ App channelMapTVar