add SSE for receiving failsafe status

api/index.js

@@ -2,50 +2,79 @@ var express = require("express");
 var app = express();
 const WebSocket = require("ws");
 
+//# TODO SSE https://www.digitalocean.com/community/tutorials/nodejs-server-sent-events-build-realtime-app
+
 var last_status = {};
 var last_image;
 var received_picture = false;
 var received_error = false;
 
+let sse_clients = [];
+
 app.use(express.static("public"));
 app.use(express.json());
 
 var ws;
 var api_connected = false;
 
-var connect_to_api = function () {
-    console.log("Connecting to API")
-    ws = new WebSocket("ws://10.100.0.40:9001/");
+function send_events_to_clients(data) {
+    sse_clients.forEach(client => client.response.write(`data: ${JSON.stringify(data)}\n\n`));
+}
 
-    ws.on("open", function open() {
-      console.log("connected with websockets to API!");
-      api_connected = true;
-    });
-    
-    ws.on("message", function message(message) {
-        try {
-            var msg = JSON.parse(message);
-            if (msg.type == "STATUS") {
-              last_status = msg.data;
-            } else if (msg.type == "IMAGE") {
-              console.log("got picture");
-              // console.log(msg.image);
-              last_image = msg.image;
-              received_picture = true;
-            }
-        } catch (error) {
-            console.log("could not parse as json")
+function handle_sse_client(request, response, next) {
+  const headers = {
+    "Content-Type": "text/event-stream",
+    'Connection': "keep-alive",
+    "Cache-Control": "no-cache",
+  };
+    // response.writeHead(200, headers);
+    // response.write("yeet\n\n");
+    const clientID = Date.now();
+    const newClient = {
+        id: clientID,
+        response
+    };
 
-        }
-    });
-    
-    ws.on("error", function error(err) {
-        console.log("there was an error")
-        console.error("error: " + err);
-        received_error = true;
+    sse_clients.push(newClient);
+
+    request.on("close", () => {
+        console.log(`${clientID} Connection closed`);
+        sse_clients = sse_clients.filter(client => client.id !== clientID);
     });
 }
 
+var connect_to_api = function () {
+  console.log("Connecting to API");
+  ws = new WebSocket("ws://10.100.0.40:9001/");
+
+  ws.on("open", function open() {
+    console.log("connected with websockets to API!");
+    api_connected = true;
+  });
+
+  ws.on("message", function message(message) {
+    try {
+      var msg = JSON.parse(message);
+      if (msg.type == "STATUS") {
+          last_status = msg.data;
+          send_events_to_clients(message);
+      } else if (msg.type == "IMAGE") {
+        console.log("got picture");
+        // console.log(msg.image);
+        last_image = msg.image;
+        received_picture = true;
+      }
+    } catch (error) {
+      console.log("could not parse as json");
+    }
+  });
+
+  ws.on("error", function error(err) {
+    console.log("there was an error");
+    console.error("error: " + err);
+    received_error = true;
+  });
+};
 
 // set the view engine to ejs
 app.set("view engine", "ejs");
@@ -61,12 +90,14 @@ app.get("/status", function (req, res) {
   res.status(200).json(last_status);
 });
 
-app.get("/image", function (req, res) { 
+app.get("/events", handle_sse_client);
+
+app.get("/image", function (req, res) {
   console.log("got picture request");
   var request = JSON.stringify({
-    command: 5
+    command: 5,
   });
-  console.log("sending picture request")
+  console.log("sending picture request");
   ws.send(request);
   res.status(200).send(last_image);
 });
@@ -78,23 +109,22 @@ app.post("/move", function (req, res) {
     up_down: req.body.up_down,
     left_right: req.body.left_right,
     forward_backward: req.body.forward_backward,
-    yaw: req.body.turn_left_right
+    yaw: req.body.turn_left_right,
   });
   ws.send(request);
 });
 
 app.get("/connect", function (req, res) {
-    console.log("got connect request");
-    connect_to_api();
-    setTimeout(function () {
-        if (api_connected) {
-            res.status(200).json({ connected: true });
-        } else {
-            received_error = false;
-            res.status(400).json({ connected: false });
-        }
-    }, 1000);
-    
+  console.log("got connect request");
+  connect_to_api();
+  setTimeout(function () {
+    if (api_connected) {
+      res.status(200).json({ connected: true });
+    } else {
+      received_error = false;
+      res.status(400).json({ connected: false });
+    }
+  }, 1000);
 });
 
 app.listen(8080);