Adding in middleware for enabling websockets.

mod.ts

@@ -1,3 +1,4 @@
 // Copyright 2020 the oak authors. All rights reserved. MIT license.
 
 export { responseTimeHeader } from "./observability/response_time_header.ts";
+export { WebSocketMiddleware } from "./websocket/enable_websockets.ts";

websocket/README.md

@@ -0,0 +1,49 @@
+The following is a re-implementation of the example server in [std/ws](https://deno.land/[email protected]/ws):
+
+```ts
+import { WebSocketMiddleware } from "https://deno.land/x/oak-middleware/mod.ts";
+import { Application } from "https://deno.land/x/oak/mod.ts";
+import {
+  isWebSocketCloseEvent,
+  isWebSocketPingEvent,
+  WebSocket,
+} from "https://deno.land/[email protected]/ws/mod.ts";
+
+async function handleWs(sock: WebSocket) {
+  console.log("socket connected!");
+  try {
+    for await (const ev of sock) {
+      if (typeof ev === "string") {
+        // text message.
+        console.log("ws:Text", ev);
+        await sock.send(ev);
+      } else if (ev instanceof Uint8Array) {
+        // binary message.
+        console.log("ws:Binary", ev);
+      } else if (isWebSocketPingEvent(ev)) {
+        const [, body] = ev;
+        // ping.
+        console.log("ws:Ping", body);
+      } else if (isWebSocketCloseEvent(ev)) {
+        // close.
+        const { code, reason } = ev;
+        console.log("ws:Close", code, reason);
+      }
+    }
+  } catch (err) {
+    console.error(`failed to receive frame: ${err}`);
+
+    if (!sock.isClosed) {
+      await sock.close(1000).catch(console.error);
+    }
+  }
+}
+
+const app = new App();
+app.use(WebSocketMiddleware(handleWs));
+
+// other middleware
+
+await app.listen(":80");
+
+```

websocket/enable_websockets.ts

@@ -0,0 +1,14 @@
+import type { Middleware, Context } from "https://deno.land/x/[email protected]/mod.ts";
+import { WebSocket, acceptable } from 'https://deno.land/[email protected]/ws/mod.ts'
+export type WebSocketHandler = (socket: WebSocket, url: URL, headers: Headers) => Promise<void>;
+
+export function WebSocketMiddleware(handler: WebSocketHandler){
+    return async function real_middleware(ctx: Context, next: () => Promise<void>) {
+            if(acceptable(ctx.request)) {
+            let ws = await ctx.upgrade();
+            await handler(ws, ctx.request.url, ctx.request.headers);
+        } else {
+            return await next();
+        }
+    };
+}