Add endpoint to obtain logs

It goes through a WebSocket; the secret is sent, and if valid, the logs
are sent back.

lib/log.js

@@ -1,5 +1,7 @@
 'use strict';
 
+const listeners = [];
+
 // Zero-pad a number in a string.
 // eg. 4 becomes 04 but 17 stays 17.
 function pad(string) {
@@ -19,9 +21,23 @@ function date() {
 }
 
 module.exports = function log(...msg) {
-  console.log(date(), ...msg);
+  const d = date();
+  listeners.forEach(f => f(d, ...msg))
+  console.log(d, ...msg);
 };
 
 module.exports.error = function error(...msg) {
-  console.error(date(), ...msg);
+  const d = date();
+  listeners.forEach(f => f(d, ...msg))
+  console.error(d, ...msg);
+};
+
+module.exports.addListener = function addListener(func) {
+  listeners.push(func);
+};
+
+module.exports.removeListener = function removeListener(func) {
+  const index = listeners.indexOf(func);
+  if (index < 0) { return; }
+  listeners.splice(index, 1);
 };

lib/sys/monitor.js

@@ -1,15 +1,45 @@
+'use strict';
+
 const secretIsValid = require('./secret-is-valid');
 const serverSecrets = require('../server-secrets');
+const log = require('../log');
+
+function secretInvalid(req, res) {
+  if (!secretIsValid(req.password)) {
+    // An unknown entity tries to connect. Let the connection linger for a minute.
+    setTimeout(function() {
+      res.json({errors: [{code: 'invalid_secrets'}]});
+    }, 10000);
+    return true;
+  }
+  return false;
+}
 
 function setRoutes(server) {
-  server.get('/sys/network', (req, res) => {
-    if (!secretIsValid(req.password)) {
-      // An unknown entity tries to connect. Let the connection linger for a minute.
-      return setTimeout(function() {
-        res.end(JSON.stringify({errors: [{code: 'invalid_secrets'}]}));
-      }, 10000);
+  server.handle(function(req, res, next) {
+    if (req.url.startsWith('/sys/')) {
+      if (secretInvalid(req, res)) { return; }
     }
-    res.end(JSON.stringify({ips: serverSecrets.shieldsIps}));
+    next();
+  });
+
+  server.get('/sys/network', (req, res) => {
+    res.json({ips: serverSecrets.shieldsIps});
+  });
+
+  server.ws('/sys/logs', socket => {
+    const listener = (...msg) => socket.send(msg.join(' '));
+    socket.on('close', () => log.removeListener(listener));
+    socket.on('message', msg => {
+      let req;
+      try {
+        req = JSON.parse(msg);
+      } catch(e) { return; }
+      if (!secretIsValid(req.secret)) {
+        return socket.close();
+      }
+      log.addListener(listener);
+    });
   });
 }
 

lib/sys/secret-is-valid.js

@@ -1,3 +1,5 @@
+'use strict';
+
 const serverSecrets = require('../server-secrets');
 
 function secretIsValid(secret = '') {