Add safe shudown

- SIGINT is intercepted and force-quits the 2nd time
 - Live countdown on Web UI
 - Countdown ignored if all clients disconnect
 - Clean exit function

app/client/public/client.htm

@@ -19,6 +19,7 @@
       </div>
       <div id="footer"></div>
       <div id="status"></div>
+      <div id="countdown"></div>
     </div>
   </div>
 <script src="/ssh/webssh2.bundle.js" defer></script>

app/client/public/webssh2.css

@@ -246,6 +246,30 @@ body, html  {
     text-align: left;
     z-index: 100;
 }
+#countdown {
+    display: none;
+    color: rgb(240, 240, 240);
+    background-color: rgb(50, 50, 50);
+    padding-left: 10px;
+    padding-right: 10px;
+    border-color: white;
+    border-style: none solid none solid;
+    border-width: 1px;
+    text-align: left;
+    z-index: 100;
+}
+#countdown.active {
+    display: inline-block;
+    animation: countdown infinite alternate 200ms;
+}
+@keyframes countdown {
+    from {
+        background-color: rgb(255, 255, 0);
+    }
+    to {
+        background-color: inherit;
+    }
+}
 #menu {
     display: inline-block;
     font-size: 16px;

app/client/src/client.htm

@@ -19,6 +19,7 @@
       </div>
       <div id="footer"></div>
       <div id="status"></div>
+      <div id="countdown"></div>
     </div>
   </div>
 <script src="/ssh/webssh2.bundle.js" defer></script>

app/client/src/css/style.css

@@ -75,6 +75,30 @@ body, html  {
     text-align: left;
     z-index: 100;
 }
+#countdown {
+    display: none;
+    color: rgb(240, 240, 240);
+    background-color: rgb(50, 50, 50);
+    padding-left: 10px;
+    padding-right: 10px;
+    border-color: white;
+    border-style: none solid none solid;
+    border-width: 1px;
+    text-align: left;
+    z-index: 100;
+}
+#countdown.active {
+    display: inline-block;
+    animation: countdown infinite alternate 200ms;
+}
+@keyframes countdown {
+    from {
+        background-color: rgb(255, 255, 0);
+    }
+    to {
+        background-color: inherit;
+    }
+}
 #menu {
     display: inline-block;
     font-size: 16px;

app/client/src/js/index.js

@@ -26,6 +26,7 @@ var status = document.getElementById('status')
 var header = document.getElementById('header')
 var dropupContent = document.getElementById('dropupContent')
 var footer = document.getElementById('footer')
+var countdown = document.getElementById('countdown')
 var fitAddon = new FitAddon()
 var terminalContainer = document.getElementById('terminal-container')
 term.loadAddon(fitAddon)
@@ -136,6 +137,7 @@ socket.on('disconnect', function (err) {
       'WEBSOCKET SERVER DISCONNECTED: ' + err
   }
   socket.io.reconnection(false)
+  countdown.classList.remove('active')
 })
 
 socket.on('error', function (err) {
@@ -149,6 +151,18 @@ socket.on('reauth', function () {
   (allowreauth) && reauthSession()
 })
 
+// safe shutdown
+var hasCountdownStarted = false
+
+socket.on('shutdownCountdownUpdate', function (remainingSeconds) {
+  if (!hasCountdownStarted) {
+    countdown.classList.add('active')
+    hasCountdownStarted = true
+  }
+
+  countdown.innerText = 'Shutting down in ' + remainingSeconds + 's'
+})
+
 term.onTitleChange(function (title) {
   document.title = title
 })

app/server/app.js

@@ -199,4 +199,50 @@ io.use(function (socket, next) {
 // bring up socket
 io.on('connection', socket)
 
+// safe shutdown
+var shutdownMode = false
+var shutdownInterval = 0
+var connectionCount = 0
+
+io.on('connection', function (socket) {
+  connectionCount++
+
+  socket.on('disconnect', function () {
+    if ((--connectionCount <= 0) && shutdownMode) {
+      stop('All clients disconnected')
+    }
+  })
+})
+
+process.on('SIGINT', function () {
+  if (shutdownMode) stop('Safe shutdown aborted, force quitting')
+  else if (connectionCount > 0) {
+    var remainingSeconds = 300
+    shutdownMode = true
+
+    var message = (connectionCount === 1) ? ' client is still connected'
+      : ' clients are still connected'
+    console.error(connectionCount + message)
+    console.error('Starting a ' + remainingSeconds + ' seconds countdown')
+    console.error('Press Ctrl+C again to force quit')
+
+    shutdownInterval = setInterval(function () {
+      if ((remainingSeconds--) <= 0) {
+        stop('Countdown is over')
+      } else {
+        io.sockets.emit('shutdownCountdownUpdate', remainingSeconds)
+      }
+    }, 1000)
+  } else stop()
+})
+
+// clean stop
+function stop (reason) {
+  shutdownMode = false
+  if (reason) console.log('Stopping: ' + reason)
+  if (shutdownInterval) clearInterval(shutdownInterval)
+  io.close()
+  server.close()
+}
+
 module.exports = { server: server, config: config }