/**
* Preview Updates Route Handler
* Provides SSE endpoint for real-time form update notifications to preview pages
*/
import express, { Request, Response, Router } from 'express';
import { randomUUID } from 'crypto';
import { SSEManager } from '../transport/sse-manager.js';
import { FormUpdateNotifier } from '../services/form-update-notifier.js';
export interface PreviewUpdatesRouteOptions {
sseManager: SSEManager;
formUpdateNotifier: FormUpdateNotifier;
maxPreviewConnections: number;
}
/**
* Creates and configures the preview updates routes
*/
export function createPreviewUpdatesRoutes(options: PreviewUpdatesRouteOptions): Router {
const router = express.Router();
const { sseManager, formUpdateNotifier, maxPreviewConnections } = options;
/**
* GET /preview-updates/:formId
* Establishes SSE connection for receiving real-time form update notifications
*/
router.get('/preview-updates/:formId', (req: Request, res: Response): void => {
const { formId } = req.params;
// Validate form ID parameter
if (!formId || formId.trim() === '') {
console.error('[PreviewUpdates] Invalid form ID:', { formId });
res.status(400).json({
error: 'Invalid form ID',
message: 'Form ID is required and cannot be empty.'
});
return;
}
// Generate unique connection ID
const connectionId = randomUUID();
// Extract client info from headers
const userAgent = req.headers['user-agent'] || 'unknown';
const clientInfo = `Preview:${formId} - ${req.ip} - ${userAgent}`;
// Get origin for CORS
const origin = req.headers.origin as string | undefined;
console.log('[PreviewUpdates] Establishing SSE connection:', {
timestamp: new Date().toISOString(),
connectionId,
formId,
ip: req.ip,
userAgent
});
try {
// Check connection limit
// Requirements: 6.4 - Log warning when approaching connection limits
const stats = formUpdateNotifier.getStats();
if (stats.totalConnections >= maxPreviewConnections) {
console.warn('[PreviewUpdates] Max preview connections reached:', {
timestamp: new Date().toISOString(),
current: stats.totalConnections,
max: maxPreviewConnections,
formId,
action: 'reject',
reason: 'connection_limit'
});
res.status(503).json({
error: 'Service Unavailable',
message: 'Maximum number of preview connections reached. Please try again later.'
});
return;
}
// Log warning when approaching limit (80% threshold)
// Requirements: 6.4 - Log warning when approaching connection limits
if (stats.totalConnections >= maxPreviewConnections * 0.8) {
const percentage = Math.round((stats.totalConnections / maxPreviewConnections) * 100);
console.warn('[PreviewUpdates] Approaching max preview connections:', {
timestamp: new Date().toISOString(),
current: stats.totalConnections,
max: maxPreviewConnections,
percentage: percentage + '%',
remaining: maxPreviewConnections - stats.totalConnections,
formId,
action: 'warning',
severity: percentage >= 90 ? 'high' : 'medium'
});
}
// Add SSE connection with origin for proper CORS handling
sseManager.addConnection(connectionId, res, clientInfo, origin);
// Register this connection with FormUpdateNotifier to receive updates for this form
formUpdateNotifier.registerPreviewConnection(connectionId, formId);
console.log('[PreviewUpdates] Preview connection registered:', {
timestamp: new Date().toISOString(),
connectionId,
formId
});
// Handle connection cleanup on disconnect
res.on('close', () => {
console.log('[PreviewUpdates] Preview connection closed:', {
timestamp: new Date().toISOString(),
connectionId,
formId
});
// Unregister from FormUpdateNotifier
formUpdateNotifier.unregisterPreviewConnection(connectionId);
});
// Handle errors
res.on('error', (err) => {
console.error('[PreviewUpdates] Preview connection error:', {
timestamp: new Date().toISOString(),
connectionId,
formId,
error: err.message
});
// Unregister from FormUpdateNotifier
formUpdateNotifier.unregisterPreviewConnection(connectionId);
});
} catch (error) {
console.error('[PreviewUpdates] Error establishing preview connection:', {
timestamp: new Date().toISOString(),
formId,
error: error instanceof Error ? error.message : String(error),
stack: error instanceof Error ? error.stack : undefined
});
// If headers haven't been sent yet, send error response
if (!res.headersSent) {
res.status(500).json({
error: 'Internal Server Error',
message: 'Failed to establish preview update connection.'
});
}
}
});
return router;
}
