refactor to use http agent interface for tunnels

lib/Client.js

@@ -0,0 +1,69 @@
+import http from 'http';
+
+import TunnelAgent from './TunnelAgent';
+
+// A client encapsulates req/res handling using an agent
+//
+// If an agent is destroyed, the request handling will error
+// The caller is responsible for handling a failed request
+class Client {
+    constructor(options) {
+        this.agent = options.agent;
+    }
+
+    handleRequest(req, res) {
+        const opt = {
+            path: req.url,
+            agent: this.agent,
+            method: req.method,
+            headers: req.headers
+        };
+
+        const clientReq = http.request(opt, (clientRes) => {
+            // write response code and headers
+            res.writeHead(clientRes.statusCode, clientRes.headers);
+            clientRes.pipe(res);
+        });
+
+        // this can happen when underlying agent produces an error
+        // in our case we 504 gateway error this?
+        // if we have already sent headers?
+        clientReq.once('error', (err) => {
+
+        });
+
+        req.pipe(clientReq);
+    }
+
+    handleUpgrade(req, socket) {
+        this.agent.createConnection({}, (err, conn) => {
+            // any errors getting a connection mean we cannot service this request
+            if (err) {
+                socket.end();
+                return;
+            }
+
+            // socket met have disconnected while we waiting for a socket
+            if (!socket.readable || !socket.writable) {
+                socket.end();
+                return;
+            }
+
+            // websocket requests are special in that we simply re-create the header info
+            // then directly pipe the socket data
+            // avoids having to rebuild the request and handle upgrades via the http client
+            const arr = [`${req.method} ${req.url} HTTP/${req.httpVersion}`];
+            for (let i=0 ; i < (req.rawHeaders.length-1) ; i+=2) {
+                arr.push(`${req.rawHeaders[i]}: ${req.rawHeaders[i+1]}`);
+            }
+
+            arr.push('');
+            arr.push('');
+
+            conn.pipe(socket).pipe(conn);
+            conn.write(arr.join('\r\n'));
+        });
+    }
+}
+
+export default Client;