update config.ts with variables to implement rateLiiting, apiVersioning and client userAgent

src/config/config.ts

@@ -2,6 +2,11 @@ export interface IConfig {
   port: number;
   mongodbUri: string;
   nodeEnv: string;
+  apiVersion: string;
+  rateLimitWindowMs: number;
+  rateLimitMaxRequests: number;
+  requestTimeoutMs: number;
+  userAgent: string;
 }
 
 class Config implements IConfig {
@@ -10,12 +15,21 @@ class Config implements IConfig {
   public readonly port: number;
   public readonly mongodbUri: string;
   public readonly nodeEnv: string;
-
+  public readonly apiVersion: string;
+  public readonly rateLimitWindowMs: number;
+  public readonly rateLimitMaxRequests: number;
+  public readonly requestTimeoutMs: number;
+  public readonly userAgent: string;
 
   private constructor() {
-    this.port = parseInt(process.env.PORT || '4000', 10);
+    this.port = parseInt(process.env.PORT || '3000', 10);
     this.mongodbUri = process.env.MONGODB_URI || 'mongodb://localhost:27017/dailytrends';
     this.nodeEnv = process.env.NODE_ENV || 'development';
+    this.apiVersion = process.env.API_VERSION || 'v1';
+    this.rateLimitWindowMs = parseInt(process.env.RATE_LIMIT_WINDOW_MS || '900000', 10);
+    this.rateLimitMaxRequests = parseInt(process.env.RATE_LIMIT_MAX_REQUESTS || '100', 10);
+    this.requestTimeoutMs = parseInt(process.env.REQUEST_TIMEOUT_MS || '10000', 10);
+    this.userAgent = process.env.USER_AGENT || 'DailyTrends-Bot/1.0';
 
     this.validateConfig();
   }
@@ -31,6 +45,22 @@ class Config implements IConfig {
     if (!this.mongodbUri) {
       throw new Error('MONGODB_URI is required');
     }
+
+    if (this.port < 1 || this.port > 65535) {
+      throw new Error('PORT must be between 1 and 65535');
+    }
+
+    if (this.rateLimitWindowMs < 1000) {
+      throw new Error('RATE_LIMIT_WINDOW_MS must be at least 1000ms');
+    }
+
+    if (this.rateLimitMaxRequests < 1) {
+      throw new Error('RATE_LIMIT_MAX_REQUESTS must be at least 1');
+    }
+
+    if (this.requestTimeoutMs < 1000) {
+      throw new Error('REQUEST_TIMEOUT_MS must be at least 1000ms');
+    }
   }
 
   public isDevelopment(): boolean {