feat: initial commit at project root

internal/config/config.js

@@ -0,0 +1,48 @@
+import process from 'process';
+
+const apiKey = process.env.API_KEY || '';
+if (apiKey.length < 32) {
+  console.error(`FATAL: API_KEY must be at least 32 characters long, current length: ${apiKey.length}`);
+  process.exit(1);
+}
+
+/**
+ * Parses duration strings like "20s", "1m" to milliseconds.
+ * @param {string|undefined} val 
+ * @param {number} defaultMs 
+ * @returns {number}
+ */
+const parseDuration = (val, defaultMs) => {
+  if (!val) return defaultMs;
+  const match = val.match(/^(\d+)(s|m|h|ms)$/);
+  if (!match) return defaultMs;
+  const num = parseInt(match[1], 10);
+  const unit = match[2];
+  switch (unit) {
+    case 'ms': return num;
+    case 's': return num * 1000;
+    case 'm': return num * 60 * 1000;
+    case 'h': return num * 60 * 60 * 1000;
+    default: return defaultMs;
+  }
+};
+
+export const config = {
+  serverAddr: process.env.SERVER_ADDR || '127.0.0.1:47880',
+  apiKey: apiKey,
+  logLevel: process.env.LOG_LEVEL || 'info',
+  maxMessageBytes: parseInt(process.env.MAX_MESSAGE_BYTES || '4096', 10),
+  heartbeatInterval: parseDuration(process.env.HEARTBEAT_INTERVAL, 20000), // 20s
+  heartbeatTimeout: parseDuration(process.env.HEARTBEAT_TIMEOUT, 30000),  // 30s
+  sessionDuration: parseDuration(process.env.SESSION_DURATION, 60000),   // 60s
+  rateLimitPerMin: parseInt(process.env.RATE_LIMIT_PER_MIN || '10', 10),
+  environment: process.env.ENVIRONMENT || 'production',
+  dbHost: process.env.DB_HOST || '127.0.0.1',
+  dbPort: parseInt(process.env.DB_PORT || '3306', 10),
+  dbDatabase: process.env.DB_DATABASE || 'callDB',
+  dbUsername: process.env.DB_USERNAME || '',
+  dbPassword: process.env.DB_PASSWORD || '',
+  turnUrl: process.env.TURN_URL || '',
+  turnUsername: process.env.TURN_USERNAME || '',
+  turnCredential: process.env.TURN_CREDENTIAL || '',
+};

internal/db/db.js

@@ -0,0 +1,119 @@
+import mysql from 'mysql2/promise';
+import { config } from '../config/config.js';
+import { logger } from '../logger/logger.js';
+
+let pool = null;
+
+/**
+ * Initializes the MySQL database pool and ensures schema exists.
+ */
+export async function initializeDatabase() {
+  if (!config.dbUsername) {
+    logger.warn('db_disabled', { reason: 'No DB_USERNAME configured, database logging is disabled' });
+    return;
+  }
+
+  try {
+    pool = mysql.createPool({
+      host: config.dbHost,
+      port: config.dbPort,
+      database: config.dbDatabase,
+      user: config.dbUsername,
+      password: config.dbPassword,
+      waitForConnections: true,
+      connectionLimit: 10,
+      queueLimit: 0
+    });
+
+    // Test connection and auto-create the table if not exists
+    const conn = await pool.getConnection();
+    await conn.query(`
+      CREATE TABLE IF NOT EXISTS \`call_logs\` (
+        \`id\` INT AUTO_INCREMENT PRIMARY KEY,
+        \`session_id\` VARCHAR(36) NOT NULL UNIQUE,
+        \`ride_id\` VARCHAR(255) NOT NULL,
+        \`driver_id\` VARCHAR(255) NOT NULL,
+        \`passenger_id\` VARCHAR(255) NOT NULL,
+        \`driver_ip\` VARCHAR(45) NULL DEFAULT NULL,
+        \`passenger_ip\` VARCHAR(45) NULL DEFAULT NULL,
+        \`driver_conn_ip\` VARCHAR(45) NULL DEFAULT NULL,
+        \`passenger_conn_ip\` VARCHAR(45) NULL DEFAULT NULL,
+        \`status\` VARCHAR(50) NOT NULL DEFAULT 'created',
+        \`initiated_by\` VARCHAR(255) NULL DEFAULT NULL,
+        \`end_reason\` VARCHAR(255) NULL DEFAULT NULL,
+        \`created_at\` TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
+        \`connected_at\` TIMESTAMP NULL DEFAULT NULL,
+        \`ended_at\` TIMESTAMP NULL DEFAULT NULL,
+        INDEX \`idx_session_id\` (\`session_id\`),
+        INDEX \`idx_ride_id\` (\`ride_id\`)
+      ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;
+    `);
+    conn.release();
+    logger.info('db_initialized', { host: config.dbHost, database: config.dbDatabase });
+  } catch (err) {
+    logger.error('db_initialization_failed', { error: err.message });
+    // Soft fallback: log the failure but do not crash the signaling server
+    pool = null;
+  }
+}
+
+/**
+ * Logs session creation to the database with pre-registered client IPs.
+ */
+export async function logSessionCreated(sessionID, rideID, driverID, passengerID, driverIP = null, passengerIP = null) {
+  if (!pool) return;
+  try {
+    await pool.query(
+      `INSERT INTO call_logs (session_id, ride_id, driver_id, passenger_id, driver_ip, passenger_ip, status, created_at)
+       VALUES (?, ?, ?, ?, ?, ?, 'created', NOW())`,
+      [sessionID, rideID, driverID, passengerID, driverIP, passengerIP]
+    );
+  } catch (err) {
+    logger.error('db_log_session_created_failed', { session_id: sessionID, error: err.message });
+  }
+}
+
+/**
+ * Logs session status transition to active and records the connection IPs.
+ */
+export async function logSessionActive(sessionID, driverConnIP = null, passengerConnIP = null) {
+  if (!pool) return;
+  try {
+    await pool.query(
+      `UPDATE call_logs SET status = 'active', connected_at = NOW(), driver_conn_ip = ?, passenger_conn_ip = ? WHERE session_id = ?`,
+      [driverConnIP, passengerConnIP, sessionID]
+    );
+  } catch (err) {
+    logger.error('db_log_session_active_failed', { session_id: sessionID, error: err.message });
+  }
+}
+
+/**
+ * Logs the initiator (caller) of the call when the first SDP offer is received.
+ */
+export async function logSessionInitiator(sessionID, initiatorID) {
+  if (!pool) return;
+  try {
+    await pool.query(
+      `UPDATE call_logs SET initiated_by = ? WHERE session_id = ? AND initiated_by IS NULL`,
+      [initiatorID, sessionID]
+    );
+  } catch (err) {
+    logger.error('db_log_session_initiator_failed', { session_id: sessionID, initiator_id: initiatorID, error: err.message });
+  }
+}
+
+/**
+ * Logs call termination reason and end time.
+ */
+export async function logSessionEnded(sessionID, endReason) {
+  if (!pool) return;
+  try {
+    await pool.query(
+      `UPDATE call_logs SET status = 'ended', ended_at = NOW(), end_reason = ? WHERE session_id = ?`,
+      [endReason, sessionID]
+    );
+  } catch (err) {
+    logger.error('db_log_session_ended_failed', { session_id: sessionID, error: err.message });
+  }
+}

internal/logger/logger.js

@@ -0,0 +1,52 @@
+import process from 'process';
+
+const LOG_LEVELS = {
+  debug: 0,
+  info: 1,
+  warn: 2,
+  error: 3
+};
+
+const currentLevelStr = (process.env.LOG_LEVEL || 'info').toLowerCase();
+const currentLevel = LOG_LEVELS[currentLevelStr] !== undefined ? LOG_LEVELS[currentLevelStr] : 1;
+
+const ANSI_COLORS = {
+  DEBUG: '\x1b[36mDEBUG\x1b[0m',   // Cyan
+  INFO: '\x1b[32mINFO\x1b[0m',     // Green
+  WARN: '\x1b[33mWARN\x1b[0m',     // Yellow
+  ERROR: '\x1b[31mERROR\x1b[0m'    // Red
+};
+
+/**
+ * Helper to print log structured JSON objects to stdout.
+ * @param {string} levelName 
+ * @param {string} eventName 
+ * @param {object} [attributes] 
+ */
+function writeLog(levelName, eventName, attributes = {}) {
+  const levelNum = LOG_LEVELS[levelName];
+  if (levelNum < currentLevel) {
+    return;
+  }
+
+  const levelUpper = levelName.toUpperCase();
+  const logEntry = {
+    timestamp: new Date().toISOString(),
+    level: `__COLOR_LEVEL_${levelUpper}__`,
+    event: eventName,
+    ...attributes
+  };
+
+  let jsonStr = JSON.stringify(logEntry);
+  const coloredLevel = ANSI_COLORS[levelUpper] || levelUpper;
+  jsonStr = jsonStr.replace(`"__COLOR_LEVEL_${levelUpper}__"`, `"${coloredLevel}"`);
+
+  process.stdout.write(jsonStr + '\n');
+}
+
+export const logger = {
+  debug: (event, attrs) => writeLog('debug', event, attrs),
+  info: (event, attrs) => writeLog('info', event, attrs),
+  warn: (event, attrs) => writeLog('warn', event, attrs),
+  error: (event, attrs) => writeLog('error', event, attrs)
+};

internal/middleware/ratelimit.js

@@ -0,0 +1,59 @@
+/**
+ * RateLimiter limits connection attempts using a sliding window.
+ */
+export class RateLimiter {
+  /**
+   * @param {number} limit Maximum connections allowed
+   * @param {number} windowMs Sliding window length in milliseconds
+   */
+  constructor(limit, windowMs) {
+    this.limit = limit;
+    this.windowMs = windowMs;
+    this.attempts = new Map();
+
+    // Start background cleanup worker every 5 minutes
+    this.cleanupInterval = setInterval(() => this.cleanup(), 5 * 60 * 1000);
+    if (this.cleanupInterval.unref) {
+      this.cleanupInterval.unref();
+    }
+  }
+
+  /**
+   * Checks if an attempt is allowed under rate limits for the given IP.
+   * @param {string} ip 
+   * @returns {boolean} True if connection attempt is within rate limits
+   */
+  allow(ip) {
+    const now = Date.now();
+    const cutoff = now - this.windowMs;
+
+    let timestamps = this.attempts.get(ip) || [];
+
+    // Filter out historical connection attempts outside the current window
+    timestamps = timestamps.filter(t => t > cutoff);
+
+    if (timestamps.length >= this.limit) {
+      this.attempts.set(ip, timestamps);
+      return false;
+    }
+
+    timestamps.push(now);
+    this.attempts.set(ip, timestamps);
+    return true;
+  }
+
+  /**
+   * Sweeps inactive keys to reclaim memory.
+   */
+  cleanup() {
+    const cutoff = Date.now() - this.windowMs;
+    for (const [ip, timestamps] of this.attempts.entries()) {
+      const active = timestamps.filter(t => t > cutoff);
+      if (active.length === 0) {
+        this.attempts.delete(ip);
+      } else {
+        this.attempts.set(ip, active);
+      }
+    }
+  }
+}

internal/protocol/messages.js

@@ -0,0 +1,48 @@
+// Message type constants
+export const TypeAuthenticate  = 'authenticate';
+export const TypeCreateSession = 'create_session';
+export const TypeJoinSession   = 'join_session';
+export const TypeOffer         = 'offer';
+export const TypeAnswer        = 'answer';
+export const TypeICECandidate  = 'ice_candidate';
+export const TypeHeartbeat     = 'heartbeat';
+export const TypeEndCall       = 'end_call';
+
+export const TypeAuthenticated     = 'authenticated';
+export const TypeSessionCreated    = 'session_created';
+export const TypeSessionJoined     = 'session_joined';
+export const TypeParticipantJoined = 'participant_joined';
+export const TypeParticipantLeft   = 'participant_left';
+export const TypeCallTimeout       = 'call_timeout';
+export const TypeCallEnded         = 'call_ended';
+export const TypePong              = 'pong';
+export const TypeUnauthorized      = 'unauthorized';
+export const TypeError             = 'error';
+
+// Error codes
+export const ErrRideNotActive       = 'ride_not_active';
+export const ErrRideAlreadyStarted  = 'ride_already_started';
+export const ErrRideCancelled       = 'ride_cancelled';
+export const ErrSessionExists       = 'session_exists';
+export const ErrSessionNotFound     = 'session_not_found';
+export const ErrSessionFull         = 'session_full';
+export const ErrUnauthorizedUser    = 'unauthorized_user';
+export const ErrTokenExpired        = 'token_expired';
+export const ErrTokenInvalid        = 'token_invalid';
+export const ErrPayloadTooLarge     = 'payload_too_large';
+export const ErrRateLimited         = 'rate_limited';
+
+// Helper constructors for encoding server messages
+export const newAuthenticated = (userID, iceServers) => JSON.stringify({ type: TypeAuthenticated, user_id: userID, ice_servers: iceServers });
+export const newSessionCreated = (sessionID, rideID, expiresIn) => JSON.stringify({ type: TypeSessionCreated, session_id: sessionID, ride_id: rideID, expires_in: expiresIn });
+export const newSessionJoined = (sessionID, rideID) => JSON.stringify({ type: TypeSessionJoined, session_id: sessionID, ride_id: rideID });
+export const newParticipantJoined = (role) => JSON.stringify({ type: TypeParticipantJoined, role });
+export const newRelayOffer = (sdp) => JSON.stringify({ type: TypeOffer, sdp });
+export const newRelayAnswer = (sdp) => JSON.stringify({ type: TypeAnswer, sdp });
+export const newRelayICE = (candidate) => JSON.stringify({ type: TypeICECandidate, candidate });
+export const newParticipantLeft = (role) => JSON.stringify({ type: TypeParticipantLeft, role });
+export const newCallTimeout = (reason) => JSON.stringify({ type: TypeCallTimeout, reason });
+export const newCallEnded = (reason) => JSON.stringify({ type: TypeCallEnded, reason });
+export const newPong = () => JSON.stringify({ type: TypePong });
+export const newUnauthorized = (reason) => JSON.stringify({ type: TypeUnauthorized, reason });
+export const newError = (code, message) => JSON.stringify({ type: TypeError, code, message });

internal/session/session.js

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+import crypto from 'crypto';
+
+/**
+ * Generates a cryptographically secure UUID version 4.
+ * @returns {string}
+ */
+export function generateUUIDv4() {
+  return crypto.randomUUID();
+}
+
+/**
+ * Session models an active call coordination session.
+ */
+export class Session {
+  /**
+   * @param {string} rideID 
+   * @param {string} driverID 
+   * @param {string} passengerID 
+   * @param {number} durationMs 
+   * @param {string} [driverIP]
+   * @param {string} [passengerIP]
+   */
+  constructor(rideID, driverID, passengerID, durationMs, driverIP = null, passengerIP = null) {
+    this.sessionID = generateUUIDv4();
+    this.rideID = rideID;
+    this.driverID = driverID;
+    this.passengerID = passengerID;
+    this.driverIP = driverIP;
+    this.passengerIP = passengerIP;
+    this.createdAt = new Date();
+    this.expiresAt = new Date(this.createdAt.getTime() + durationMs);
+    this.status = 'waiting'; // "waiting" | "active" | "ended"
+    this.driverConn = null;
+    this.passengerConn = null;
+    this.timer = null;
+  }
+}

internal/session/store.js

@@ -0,0 +1,88 @@
+import { Session } from './session.js';
+
+/**
+ * Store handles active in-memory sessions indexed by session ID.
+ * It also maintains a ride ID mapping to prevent duplicate active sessions per ride.
+ */
+export class Store {
+  constructor() {
+    this.sessions = new Map(); // key: sessionID, value: Session
+    this.rideToSession = new Map(); // key: rideID, value: Session
+  }
+
+  /**
+   * Retrieves a session by its session ID.
+   * @param {string} sessionID 
+   * @returns {Session|undefined}
+   */
+  getSession(sessionID) {
+    return this.sessions.get(sessionID);
+  }
+
+  /**
+   * Retrieves an active session by its ride ID.
+   * @param {string} rideID 
+   * @returns {Session|undefined}
+   */
+  getSessionByRide(rideID) {
+    return this.rideToSession.get(rideID);
+  }
+
+  /**
+   * Registers a new call session, checking for active duplicates.
+   * @param {string} rideID 
+   * @param {string} driverID 
+   * @param {string} passengerID 
+   * @param {number} durationMs 
+   * @param {string} [driverIP]
+   * @param {string} [passengerIP]
+   * @returns {Session}
+   * @throws {Error} Throws if an active session already exists for the ride
+   */
+  createSession(rideID, driverID, passengerID, durationMs, driverIP = null, passengerIP = null) {
+    const existing = this.rideToSession.get(rideID);
+    if (existing && existing.status !== 'ended') {
+      throw new Error('session_exists');
+    }
+
+    const sess = new Session(rideID, driverID, passengerID, durationMs, driverIP, passengerIP);
+    this.sessions.set(sess.sessionID, sess);
+    this.rideToSession.set(rideID, sess);
+    return sess;
+  }
+
+  /**
+   * Removes a session from registry mappings.
+   * @param {string} sessionID 
+   */
+  destroySession(sessionID) {
+    const sess = this.sessions.get(sessionID);
+    if (sess) {
+      this.sessions.delete(sessionID);
+      this.rideToSession.delete(sess.rideID);
+    }
+  }
+
+  /**
+   * Finds expired active sessions.
+   * @returns {Session[]}
+   */
+  getExpiredSessions() {
+    const expired = [];
+    const now = Date.now();
+    for (const sess of this.sessions.values()) {
+      if (sess.status !== 'ended' && now > sess.expiresAt.getTime()) {
+        expired.push(sess);
+      }
+    }
+    return expired;
+  }
+
+  /**
+   * Returns active sessions count.
+   * @returns {number}
+   */
+  getActiveCount() {
+    return this.sessions.size;
+  }
+}

internal/timer/timer.js

@@ -0,0 +1,32 @@
+/**
+ * CallTimer wraps Node's setTimeout/clearTimeout to allow session cancellations.
+ */
+export class CallTimer {
+  /**
+   * @param {number} durationMs 
+   * @param {function} onExpiry 
+   */
+  constructor(durationMs, onExpiry) {
+    this.timer = setTimeout(onExpiry, durationMs);
+  }
+
+  /**
+   * Cancels the active timer.
+   */
+  stop() {
+    if (this.timer) {
+      clearTimeout(this.timer);
+      this.timer = null;
+    }
+  }
+}
+
+/**
+ * Starts a session timeout timer.
+ * @param {number} durationMs 
+ * @param {function} onExpiry 
+ * @returns {CallTimer}
+ */
+export function startTimer(durationMs, onExpiry) {
+  return new CallTimer(durationMs, onExpiry);
+}

internal/ws/client.js

@@ -0,0 +1,151 @@
+import { logger } from '../logger/logger.js';
+import * as protocol from '../protocol/messages.js';
+
+/**
+ * Client represents a single active WebSocket connection wrapper.
+ * It encapsulates the raw connection, handles ping/pong heartbeat,
+ * parses messages, and routes events back to the coordinator Hub.
+ */
+export class Client {
+  /**
+   * Initializes a new client instance and sets up connection event listeners and heartbeat.
+   * @param {object} conn The raw WS socket connection instance from the 'ws' library.
+   * @param {object} hub The central Hub coordinator to process and route messages.
+   */
+  constructor(conn, hub) {
+    this.conn = conn; // The underlying raw WebSocket connection
+    this.hub = hub;   // Reference to the main coordinator hub
+    this.userID = ''; // Authenticated user ID (driver_id or passenger_id)
+    this.rideID = ''; // Associated ride ID
+    this.role = '';   // User's role: 'driver' or 'passenger'
+    this.isAlive = true; // Connection status flag updated by heartbeat pong responses
+    this.pongTimeout = null; // Timer waiting for a pong reply after sending a ping
+
+    /**
+     * Listener for incoming WebSocket message payloads.
+     * Enforces a hard read limit of 4096 bytes (4KB) to prevent Denial of Service (DoS) memory consumption.
+     */
+    this.conn.on('message', (data) => {
+      if (data.length > 4096) {
+        logger.warn('payload_too_large', { remote_ip: this.remoteIP() });
+        this.send(protocol.newError(protocol.ErrPayloadTooLarge, 'Payload too large'));
+        this.close();
+        return;
+      }
+      // Pass the message to the hub for authentication and signaling routing
+      this.hub.handleMessage(this, data);
+    });
+
+    /**
+     * Listener for the 'pong' response frame.
+     * Indicates that the client is responsive. Clears the timeout timer.
+     */
+    this.conn.on('pong', () => {
+      this.isAlive = true;
+      if (this.pongTimeout) {
+        clearTimeout(this.pongTimeout);
+        this.pongTimeout = null;
+      }
+    });
+
+    /**
+     * Listener for connection close event.
+     * Triggers cleanup of heartbeat timers and unregisters the client from the hub.
+     */
+    this.conn.on('close', () => {
+      this.cleanup();
+      this.hub.unregister(this);
+    });
+
+    /**
+     * Listener for socket connection errors.
+     * Logs the error details and safely terminates the connection.
+     */
+    this.conn.on('error', (err) => {
+      logger.error('websocket_error', {
+        user_id: this.userID,
+        ride_id: this.rideID,
+        error: err.message
+      });
+      this.close();
+    });
+
+    /**
+     * Heartbeat loop: Pings the client every 20 seconds.
+     * If the client does not respond with a pong within 10 seconds, the connection is considered dead and closed.
+     * This prevents resource leaks from half-open TCP connections.
+     */
+    this.pingInterval = setInterval(() => {
+      this.isAlive = false;
+      try {
+        this.conn.ping();
+      } catch (err) {
+        this.close();
+        return;
+      }
+
+      // Schedule a timeout check for 10 seconds. Close connection if isAlive is still false.
+      this.pongTimeout = setTimeout(() => {
+        if (!this.isAlive) {
+          logger.warn('heartbeat_timeout', {
+            user_id: this.userID,
+            ride_id: this.rideID,
+            remote_ip: this.remoteIP()
+          });
+          this.close();
+        }
+      }, 10000);
+    }, 20000);
+  }
+
+  /**
+   * Sends a serialized JSON message down the WebSocket connection wire.
+   * Checks the connection readyState to ensure it is in the OPEN state before writing.
+   * @param {string} msg Serialized JSON string message payload.
+   */
+  send(msg) {
+    if (this.conn.readyState === 1) { // WebSocket.OPEN state
+      try {
+        this.conn.send(msg);
+      } catch (err) {
+        logger.error('websocket_send_failed', { error: err.message });
+      }
+    }
+  }
+
+  /**
+   * Resolves the remote IP address of the connected client.
+   * Falls back to 'unknown' if the connection socket is already closed or unavailable.
+   * @returns {string} The remote client's IP address.
+   */
+  remoteIP() {
+    return this.conn._socket ? this.conn._socket.remoteAddress : 'unknown';
+  }
+
+  /**
+   * Safely terminates the WebSocket connection and releases local memory and timers.
+   */
+  close() {
+    try {
+      this.conn.close();
+    } catch (err) {
+      // Ignored: connection might already be closed or unreachable
+    }
+    this.cleanup();
+  }
+
+  /**
+   * Cleans up and clears all scheduled interval pings and timeout check timers.
+   * This is critical to prevent CPU timer memory leaks when client closes.
+   */
+  cleanup() {
+    if (this.pingInterval) {
+      clearInterval(this.pingInterval);
+      this.pingInterval = null;
+    }
+    if (this.pongTimeout) {
+      clearTimeout(this.pongTimeout);
+      this.pongTimeout = null;
+    }
+  }
+}

internal/ws/handler.js

@@ -0,0 +1,59 @@
+import { WebSocketServer } from 'ws';
+import { Client } from './client.js';
+import { logger } from '../logger/logger.js';
+
+/**
+ * Attaches the WebSocket server upgrade hook to the given HTTP server instance.
+ * It intercepts standard HTTP GET requests for WebSocket protocols and handles upgrades.
+ * @param {object} server The native http.Server instance.
+ * @param {object} hub The central Hub coordinator instance.
+ * @param {object} limiter The IP-based RateLimiter instance.
+ */
+export function setupWebSocket(server, hub, limiter) {
+  // Initialize ws server in noServer mode since we manually intercept upgrade requests.
+  const wss = new WebSocketServer({ noServer: true });
+
+  /**
+   * Listens for the HTTP 'upgrade' event to switch protocol from HTTP to WebSocket.
+   */
+  server.on('upgrade', (request, socket, head) => {
+    const ip = getClientIP(request);
+
+    // Enforce IP-based rate limiting to prevent spam connections.
+    if (!limiter.allow(ip)) {
+      logger.warn('rate_limit_exceeded', { remote_ip: ip });
+      // Send 429 Too Many Requests response to client and close connection.
+      socket.write('HTTP/1.1 429 Too Many Requests\r\nConnection: close\r\n\r\nrate_limited');
+      socket.destroy();
+      return;
+    }
+
+    // Hand over control to 'ws' library to complete the upgrade protocol handshake.
+    wss.handleUpgrade(request, socket, head, (wsConn) => {
+      // Set remote address on socket mock for later client IP queries.
+      // This ensures we can resolve client IP even after connection is upgraded.
+      wsConn._socket = wsConn._socket || {};
+      wsConn._socket.remoteAddress = ip;
+
+      // Instantiate a new Client wrapper.
+      // Event listeners are automatically attached in the Client constructor.
+      new Client(wsConn, hub);
+    });
+  });
+}
+
+/**
+ * Resolves the client's original IP address, supporting reverse proxy setups
+ * (like Nginx) that forward the real client IP via X-Forwarded-For header.
+ * @param {object} request The http.IncomingMessage request object.
+ * @returns {string} The resolved IP address.
+ */
+function getClientIP(request) {
+  const xff = request.headers['x-forwarded-for'];
+  if (xff) {
+    // If proxied multiple times, the first element is the client's real IP.
+    const ips = xff.split(',');
+    return ips[0].trim();
+  }
+  return request.socket.remoteAddress || 'unknown';
+}

internal/ws/hub.js

@@ -0,0 +1,454 @@
+import { logger } from '../logger/logger.js';
+import * as protocol from '../protocol/messages.js';
+import { logSessionActive, logSessionInitiator, logSessionEnded } from '../db/db.js';
+import { config } from '../config/config.js';
+
+/**
+ * Hub is the central coordinator for all active call sessions and client sockets.
+ * It manages connection mappings, routing of WebRTC signaling payloads (Offer, Answer, ICE),
+ * enforcing call session timers, and logging call connectivity changes to the database.
+ */
+export class Hub {
+  /**
+   * Initializes the Hub instance.
+   * @param {object} store The session memory store that holds active call profiles.
+   */
+  constructor(store) {
+    this.clients = new Map(); // Map storing authenticated socket wrappers: Key is userID, Value is Client instance
+    this.store = store;       // Reference to the active sessions in-memory storage
+
+    // Background job: Periodically scans the session store every 10 seconds to close expired sessions
+    this.sweepInterval = setInterval(() => this.sweepExpiredSessions(), 10000);
+    if (this.sweepInterval.unref) {
+      this.sweepInterval.unref(); // Prevent this interval from keeping the Node process alive on exit
+    }
+  }
+
+  /**
+   * Unregisters a disconnected client from the active clients registry map.
+   * If the client had an active session, it triggers call termination.
+   * @param {Client} client The Client connection instance.
+   */
+  unregister(client) {
+    if (client.userID) {
+      // Check if the registered instance matches the client being removed
+      if (this.clients.get(client.userID) === client) {
+        this.clients.delete(client.userID);
+        logger.info('client_disconnected', {
+          user_id: client.userID,
+          session_id: client.sessionID,
+          remote_ip: client.remoteIP()
+        });
+      }
+    }
+
+    // If client was part of an active session, end the session since one participant disconnected
+    if (client.sessionID) {
+      this.endSession(client.sessionID, client.role);
+    }
+  }
+
+  /**
+   * Ends an active call session because one of the participants disconnected.
+   * Cleans up timeouts, notifies the counterparty, and deletes session records.
+   * @param {string} sessionID The unique identifier of the call session.
+   * @param {string} leftRole The role of the client who disconnected ('driver' or 'passenger').
+   */
+  endSession(sessionID, leftRole) {
+    const sess = this.store.getSession(sessionID);
+    if (!sess) return;
+
+    if (sess.status === 'ended') return;
+    sess.status = 'ended';
+
+    // Log the disconnection event and reason to the database
+    logSessionEnded(sessionID, `disconnect_${leftRole}`);
+
+    // Stop the 60 seconds hard call duration timer
+    if (sess.timer) {
+      sess.timer.stop();
+      sess.timer = null;
+    }
+
+    logger.info('session_ended_by_disconnect', {
+      session_id: sessionID,
+      left_role: leftRole
+    });
+
+    // Notify the remaining peer that their partner left, and close their connection
+    const peer = leftRole === 'driver' ? sess.passengerConn : sess.driverConn;
+    if (peer) {
+      peer.send(protocol.newParticipantLeft(leftRole));
+      peer.close();
+    }
+
+    // Evict the session from the active store index
+    this.store.destroySession(sessionID);
+  }
+
+  /**
+   * Forces a session to end due to reaching the maximum call duration (e.g. 60 seconds).
+   * @param {string} sessionID The unique identifier of the call session.
+   * @param {string} reason The termination reason code (usually 'max_duration_reached').
+   */
+  forceEndSession(sessionID, reason) {
+    const sess = this.store.getSession(sessionID);
+    if (!sess) return;
+
+    if (sess.status === 'ended') return;
+    sess.status = 'ended';
+
+    // Log the timeout event to the database
+    logSessionEnded(sessionID, reason);
+
+    if (sess.timer) {
+      sess.timer.stop();
+      sess.timer = null;
+    }
+
+    logger.info('call_timeout', {
+      session_id: sessionID,
+      reason: reason
+    });
+
+    // Construct and transmit the timeout signal to both participants
+    const timeoutMsg = protocol.newCallTimeout(reason);
+
+    if (sess.driverConn) {
+      sess.driverConn.send(timeoutMsg);
+      sess.driverConn.close();
+    }
+    if (sess.passengerConn) {
+      sess.passengerConn.send(timeoutMsg);
+      sess.passengerConn.close();
+    }
+
+    this.store.destroySession(sessionID);
+  }
+
+  /**
+   * Ends an active call session because one of the participants hung up.
+   * @param {string} sessionID The unique identifier of the call session.
+   */
+  userEndCall(sessionID) {
+    const sess = this.store.getSession(sessionID);
+    if (!sess) return;
+
+    if (sess.status === 'ended') return;
+    sess.status = 'ended';
+
+    // Log the hangup event to the database
+    logSessionEnded(sessionID, 'user_terminated');
+
+    if (sess.timer) {
+      sess.timer.stop();
+      sess.timer = null;
+    }
+
+    logger.info('call_ended', {
+      session_id: sessionID,
+      reason: 'user_terminated'
+    });
+
+    // Notify both participants that the call was hung up
+    const endedMsg = protocol.newCallEnded('user_terminated');
+
+    if (sess.driverConn) {
+      sess.driverConn.send(endedMsg);
+      sess.driverConn.close();
+    }
+    if (sess.passengerConn) {
+      sess.passengerConn.send(endedMsg);
+      sess.passengerConn.close();
+    }
+
+    this.store.destroySession(sessionID);
+  }
+
+  /**
+   * Gracefully shuts down all connected clients (invoked during server shutdown).
+   */
+  shutdownGracefully() {
+    logger.info('server_shutdown_alert_clients');
+    for (const client of this.clients.values()) {
+      client.send(protocol.newCallEnded('server_shutdown'));
+      client.close();
+    }
+  }
+
+  /**
+   * Sweeps and shuts down any sessions that have exceeded their expiration timestamps.
+   */
+  sweepExpiredSessions() {
+    const expired = this.store.getExpiredSessions();
+    for (const sess of expired) {
+      this.forceEndSession(sess.sessionID, 'max_duration_reached');
+    }
+  }
+
+  /**
+   * Returns the count of currently connected and authenticated WebSocket client connections.
+   * @returns {number} Active client connections count.
+   */
+  getConnectedClientsCount() {
+    return this.clients.size;
+  }
+
+  /**
+   * Processes incoming raw WebSocket message payloads.
+   * Handles client authentication and parses signalling messages.
+   * @param {Client} client The Client socket wrapper that received the message.
+   * @param {Buffer|string} msgBytes The raw message payload bytes.
+   */
+  handleMessage(client, msgBytes) {
+    let base;
+    try {
+      base = JSON.parse(msgBytes.toString());
+    } catch (err) {
+      client.send(protocol.newError(protocol.ErrTokenInvalid, 'Invalid JSON format'));
+      return;
+    }
+
+    // 1. Enforce Authentication (Must be the very first message sent by a client connection)
+    if (!client.userID) {
+      if (base.type !== protocol.TypeAuthenticate) {
+        client.send(protocol.newError(protocol.ErrTokenInvalid, 'Authentication required'));
+        client.close();
+        return;
+      }
+
+      const { session_id, user_id } = base;
+      if (!session_id || !user_id) {
+        client.send(protocol.newError(protocol.ErrTokenInvalid, 'Missing session_id or user_id'));
+        client.close();
+        return;
+      }
+
+      // Check if the session exists in the memory store
+      const sess = this.store.getSession(session_id);
+      if (!sess) {
+        client.send(protocol.newError(protocol.ErrSessionNotFound, 'No active session found'));
+        client.close();
+        return;
+      }
+
+      if (sess.status === 'ended') {
+        client.send(protocol.newError(protocol.ErrSessionNotFound, 'Session already ended'));
+        client.close();
+        return;
+      }
+
+      // Authorize client: user_id must match the driverID or passengerID pre-created for this session
+      let role = '';
+      if (user_id === sess.driverID) {
+        role = 'driver';
+        if (sess.driverConn) {
+          client.send(protocol.newError(protocol.ErrSessionExists, 'Driver already connected'));
+          client.close();
+          return;
+        }
+      } else if (user_id === sess.passengerID) {
+        role = 'passenger';
+        if (sess.passengerConn) {
+          client.send(protocol.newError(protocol.ErrSessionExists, 'Passenger already connected'));
+          client.close();
+          return;
+        }
+      } else {
+        client.send(protocol.newError(protocol.ErrUnauthorizedUser, 'User not authorized for this session'));
+        client.close();
+        return;
+      }
+
+      // Kick out any duplicate connections for this user ID
+      if (this.clients.has(user_id)) {
+        const existing = this.clients.get(user_id);
+        if (existing) {
+          existing.close();
+        }
+      }
+
+      // Bind session context to the Client object
+      client.userID = user_id;
+      client.sessionID = session_id;
+      client.role = role;
+      client.rideID = sess.rideID;
+
+      // Register the client in the hub's active connections map
+      this.clients.set(client.userID, client);
+
+      // Register connection in the session
+      if (role === 'driver') {
+        sess.driverConn = client;
+      } else {
+        sess.passengerConn = client;
+      }
+
+      // Log a warning if the connection IP does not match the pre-registered IP
+      const connectionIP = client.remoteIP();
+      const expectedIP = role === 'driver' ? sess.driverIP : sess.passengerIP;
+      if (expectedIP && expectedIP !== '127.0.0.1' && expectedIP !== 'localhost' && connectionIP !== expectedIP) {
+        logger.warn('client_ip_mismatch', {
+          user_id: user_id,
+          session_id: session_id,
+          role: role,
+          expected_ip: expectedIP,
+          connection_ip: connectionIP
+        });
+      }
+
+      logger.info('client_authenticated', {
+        user_id: client.userID,
+        session_id: client.sessionID,
+        role: client.role,
+        remote_ip: connectionIP
+      });
+
+      // Prepare ICE servers configuration dynamically
+      const iceServers = [
+        { urls: 'stun:stun.l.google.com:19302' },
+        { urls: 'stun:stun1.l.google.com:19302' }
+      ];
+      if (config.turnUrl) {
+        iceServers.push({
+          urls: `${config.turnUrl}?transport=udp`,
+          username: config.turnUsername,
+          credential: config.turnCredential
+        });
+        iceServers.push({
+          urls: `${config.turnUrl}?transport=tcp`,
+          username: config.turnUsername,
+          credential: config.turnCredential
+        });
+      }
+
+      // Confirm successful authentication to the client with the dynamic ICE servers configuration
+      client.send(protocol.newAuthenticated(client.userID, iceServers));
+
+      // Trigger WebRTC active session joined if both are connected
+      if (sess.driverConn && sess.passengerConn) {
+        sess.status = 'active';
+        const driverConnIP = sess.driverConn.remoteIP();
+        const passengerConnIP = sess.passengerConn.remoteIP();
+        logSessionActive(session_id, driverConnIP, passengerConnIP);
+
+        logger.info('session_joined_active', {
+          session_id: session_id,
+          ride_id: sess.rideID,
+          driver_conn_ip: driverConnIP,
+          passenger_conn_ip: passengerConnIP
+        });
+
+        // Notify both clients that they have successfully joined the active session
+        const joinedMsg = protocol.newSessionJoined(session_id, sess.rideID);
+        sess.driverConn.send(joinedMsg);
+        sess.passengerConn.send(joinedMsg);
+
+        // Send participant joined alerts to trigger WebRTC peer-to-peer negotiation
+        sess.driverConn.send(protocol.newParticipantJoined('passenger'));
+        sess.passengerConn.send(protocol.newParticipantJoined('driver'));
+      }
+      return;
+    }
+
+    // 2. Process authenticated WebRTC signaling payloads
+    switch (base.type) {
+      case protocol.TypeOffer:
+        this.handleOffer(client, base);
+        break;
+      case protocol.TypeAnswer:
+        this.handleAnswer(client, base);
+        break;
+      case protocol.TypeICECandidate:
+        this.handleICECandidate(client, base);
+        break;
+      case protocol.TypeHeartbeat:
+        client.send(protocol.newPong()); // Reply with pong frame
+        break;
+      case protocol.TypeEndCall:
+        this.handleEndCall(client, base);
+        break;
+      default:
+        client.send(protocol.newError('bad_request', 'Unknown message type'));
+    }
+  }
+
+  /**
+   * Relays a WebRTC SDP Offer message to the peer connection.
+   * Also identifies and logs the caller (initiator) of the call in the database on the first offer.
+   * @param {Client} client The Client instance that sent the offer.
+   * @param {object} m The offer message object containing the SDP.
+   */
+  handleOffer(client, m) {
+    const sess = this.store.getSession(client.sessionID);
+    if (!sess) {
+      client.send(protocol.newError(protocol.ErrSessionNotFound, 'Session not found'));
+      return;
+    }
+
+    // Log initiator of the call in the database (the user who sends the first WebRTC offer)
+    if (!sess.initiatedBy) {
+      sess.initiatedBy = client.userID;
+      logSessionInitiator(client.sessionID, client.userID);
+    }
+
+    const target = client.role === 'driver' ? sess.passengerConn : sess.driverConn;
+    if (!target) {
+      client.send(protocol.newError(protocol.ErrSessionNotFound, 'Peer not connected'));
+      return;
+    }
+
+    target.send(protocol.newRelayOffer(m.sdp));
+  }
+
+  /**
+   * Relays a WebRTC SDP Answer message back to the peer.
+   * @param {Client} client The Client instance that sent the answer.
+   * @param {object} m The answer message object containing the SDP.
+   */
+  handleAnswer(client, m) {
+    const sess = this.store.getSession(client.sessionID);
+    if (!sess) {
+      client.send(protocol.newError(protocol.ErrSessionNotFound, 'Session not found'));
+      return;
+    }
+
+    const target = client.role === 'driver' ? sess.passengerConn : sess.driverConn;
+    if (!target) {
+      client.send(protocol.newError(protocol.ErrSessionNotFound, 'Peer not connected'));
+      return;
+    }
+
+    target.send(protocol.newRelayAnswer(m.sdp));
+  }
+
+  /**
+   * Relays a WebRTC ICE candidate message to the peer.
+   * @param {Client} client The Client instance that sent the candidate.
+   * @param {object} m The ICE candidate message object.
+   */
+  handleICECandidate(client, m) {
+    const sess = this.store.getSession(client.sessionID);
+    if (!sess) {
+      client.send(protocol.newError(protocol.ErrSessionNotFound, 'Session not found'));
+      return;
+    }
+
+    const target = client.role === 'driver' ? sess.passengerConn : sess.driverConn;
+    if (!target) {
+      client.send(protocol.newError(protocol.ErrSessionNotFound, 'Peer not connected'));
+      return;
+    }
+
+    target.send(protocol.newRelayICE(m.candidate));
+  }
+
+  /**
+   * Handles user-triggered end_call action.
+   * @param {Client} client The Client instance that requested to end the call.
+   * @param {object} m The end_call message object.
+   */
+  handleEndCall(client, m) {
+    this.userEndCall(client.sessionID);
+  }
+}