feat(ws): send history data and update data with web socket

Added following logic:
1. New clients receive 15 entry history from history file
2. After that, every 10 seconds when new entry is generated it is sent
out to all connected clients

backend/classes/HistoryFile.js

@@ -14,7 +14,7 @@ export default class HistoryFile {
    */
   writeToFile() {
     try {
-      fs.writeFileSync(this.path, JSON.stringify(this.history));
+      fs.writeFileSync(this.path, JSON.stringify(this.history, null, 2));
       return true;
     } catch (err) {
       console.error(`Failed to write data to history file: ${err.message}`);

backend/consts.js

@@ -0,0 +1,6 @@
+// Define global constants for min and max values
+export const MAX = 100;
+export const MIN = 0;
+
+// Define range for random number generation
+export const RANGE = 0.3; // +-0.3 -> +-30% of previous number

backend/data.json

@@ -1 +0,0 @@
-[]

backend/index.js

@@ -1,26 +1,41 @@
 import { WebSocketServer } from 'ws';
 import HistoryFile from './classes/HistoryFile.js';
+import { MIN, MAX, RANGE } from './consts.js';
+import { randomInt, randomInRange } from './utils/random.js';
 
-// Define WebSocket server
-const wss = new WebSocketServer({ port: 8080 });
 // Define History file class
 // For managing data state beyond restart
 const history = new HistoryFile('data.json');
 
+// Define WebSocket server
+const wss = new WebSocketServer({ port: 8080 });
+
 wss.on('connection', (ws) => {
   // On successful connection, we send history data to the client
   // After that, we procceed sending data update every 10 seconds
-  console.log('Client connected');
-
-  ws.on('message', (message) => {
-    console.log(`Received message => ${message}`);
-  });
-
-  ws.on('close', () => {
-    console.log('Client disconnected');
-  });
-
-  ws.send('Hello! Message from server.');
+  ws.send(JSON.stringify({ type: 'history', data: history.history }));
 });
 
-console.log('WebSocket server is running on ws://localhost:8080');
+// Generate initial random number, or take it from the history if that exists
+let previousNumber = randomInt(MIN, MAX);
+if (history.history.length > 0) {
+  previousNumber = history.history[history.history.length - 1].number;
+  console.log(`Previous number: ${previousNumber}`);
+}
+
+/*
+ * Execute every 10 seconds
+ * This will update hisotry data, by appending new entry
+ * Then save this data to a history file
+ * And notify all clients about new data entry
+ */
+setInterval(() => {
+  const newNumber = randomInRange(previousNumber, RANGE, MIN, MAX);
+  const newEntry = history.append(newNumber);
+
+  // Send new entry to all connected clients
+  wss.clients.forEach((client) => {
+    if (client.readyState !== WebSocket.OPEN) return;
+    client.send(JSON.stringify({ type: 'update', data: newEntry }));
+  });
+}, 10 * 1000);

backend/nodemon.json

@@ -0,0 +1,4 @@
+{
+  "watch": ["."],
+  "ignore": ["node_modules/**", "data.json"]
+}