Uploading Genesys Cloud Web Messaging File Attachments via Guest API with TypeScript

What You Will Build

• A TypeScript module that validates, uploads, and attaches files to Genesys Cloud Web Messaging guest sessions using the Attachment and Web Messaging APIs.
• The implementation leverages the @genesyscloud/purecloud-platform-client-v2 SDK for initialization and axios for binary stream handling to preserve payload integrity.
• The code covers TypeScript with Node.js runtime, Express for webhook ingestion, and AWS SDK v3 types for external bucket synchronization.

Prerequisites

• OAuth client credentials flow with scopes: attachment:upload, webmessaging:guest, webmessaging:guest:send
• Genesys Cloud API v2 base URL: https://api.mypurecloud.com
• Node.js 18+ with TypeScript 5+ and npm or yarn
• External dependencies: @genesyscloud/purecloud-platform-client-v2, axios, express, @aws-sdk/client-s3, uuid, crypto

Authentication Setup

Genesys Cloud requires a bearer token for all API calls. The client credentials flow exchanges a client ID and secret for a short-lived token. Production systems must cache tokens and refresh before expiration. The SDK handles token caching internally, but direct HTTP calls require explicit header injection.

import axios, { AxiosInstance } from 'axios';
import { platformClient } from '@genesyscloud/purecloud-platform-client-v2';
import { Configuration } from '@genesyscloud/purecloud-platform-client-v2';

export interface GenesysAuthConfig {
  clientId: string;
  clientSecret: string;
  environment: string; // e.g., 'mypurecloud.com'
}

export async function initializeGenesysClient(config: GenesysAuthConfig): Promise<AxiosInstance> {
  const env = config.environment === 'mypurecloud.com' ? '' : `.${config.environment}`;
  const baseUrl = `https://api${env}`;

  // Configure the official SDK for scope validation and token caching
  platformClient.setEnvironment('mypurecloud.com');
  platformClient.loginClientCredentials(config.clientId, config.clientSecret);

  // Retrieve token for direct axios usage
  const tokenResponse = await platformClient.auth.getAccessToken();
  const accessToken = tokenResponse.token;

  // Axios instance with standardized headers and retry configuration
  const client = axios.create({
    baseURL: `${baseUrl}/api/v2`,
    headers: {
      Authorization: `Bearer ${accessToken}`,
      'Content-Type': 'application/json',
      'Accept': 'application/json',
      'User-Agent': 'GenesysAttachmentUploader/1.0'
    }
  });

  return client;
}

The platformClient.loginClientCredentials method caches the token in memory and automatically handles scope validation. The returned AxiosInstance injects the Authorization header into every request. The attachment:upload scope is mandatory for the attachment endpoints, and webmessaging:guest is required for message dispatch.

Implementation

Step 1: Validation Pipeline & Schema Enforcement

Genesys Cloud enforces strict media engine constraints. The platform rejects payloads that exceed size limits, contain blacklisted MIME types, or violate chunk boundaries. Client-side validation prevents unnecessary network calls and reduces 400/413 errors. The pipeline below enforces a MIME matrix, size directive, extension whitelist, and chunk boundary verification.

import { Readable } from 'stream';

export interface UploadConstraints {
  maxFileSizeBytes: number;
  maxAttachmentsPerMessage: number;
  allowedMimes: string[];
  allowedExtensions: string[];
  chunkSizeBytes: number;
}

const DEFAULT_CONSTRAINTS: UploadConstraints = {
  maxFileSizeBytes: 10 * 1024 * 1024, // 10 MB
  maxAttachmentsPerMessage: 5,
  allowedMimes: ['image/png', 'image/jpeg', 'application/pdf', 'text/plain', 'application/zip'],
  allowedExtensions: ['.png', '.jpg', '.jpeg', '.pdf', '.txt', '.zip'],
  chunkSizeBytes: 64 * 1024 // 64 KB chunks for boundary verification
};

export function validateAttachment(file: Buffer, fileName: string, constraints: UploadConstraints = DEFAULT_CONSTRAINTS): void {
  // Size directive validation
  if (file.length > constraints.maxFileSizeBytes) {
    throw new Error(`File exceeds maximum size directive: ${file.length} bytes. Limit: ${constraints.maxFileSizeBytes}`);
  }

  // Extension whitelisting
  const ext = fileName.substring(fileName.lastIndexOf('.')).toLowerCase();
  if (!constraints.allowedExtensions.includes(ext)) {
    throw new Error(`Extension ${ext} is not in the whitelist. Allowed: ${constraints.allowedExtensions.join(', ')}`);
  }

  // MIME matrix validation (basic magic number check)
  const mimeMap: Record<string, Buffer> = {
    '.png': Buffer.from([0x89, 0x50, 0x4E, 0x47]),
    '.jpg': Buffer.from([0xFF, 0xD8, 0xFF]),
    '.pdf': Buffer.from([0x25, 0x50, 0x44, 0x46]),
    '.zip': Buffer.from([0x50, 0x4B, 0x03, 0x04])
  };

  if (mimeMap[ext] && !file.slice(0, mimeMap[ext].length).equals(mimeMap[ext])) {
    throw new Error(`MIME matrix mismatch for ${ext}. File header does not match expected magic numbers.`);
  }

  // Chunk boundary verification pipeline
  let offset = 0;
  const chunkCount = Math.ceil(file.length / constraints.chunkSizeBytes);
  for (let i = 0; i < chunkCount; i++) {
    const end = Math.min(offset + constraints.chunkSizeBytes, file.length);
    const chunk = file.slice(offset, end);
    
    // Verify chunk boundaries are not corrupted by null-injection or stream truncation
    if (chunk.length === 0 && i < chunkCount - 1) {
      throw new Error(`Chunk boundary verification failed: Empty chunk at index ${i}. Stream may be truncated.`);
    }
    offset = end;
  }
}

The validation function runs before any network call. It checks the size directive against the media engine limit, verifies the extension against a whitelist, compares file headers against a MIME matrix, and iterates through chunk boundaries to ensure stream integrity. This prevents malformed payloads from triggering Genesys validation errors or exhausting API quotas.

Step 2: Attachment Creation & Atomic Binary Upload

Genesys Cloud uses a two-step attachment process. The first request registers the metadata and returns an attachment ID. The second request performs an atomic PUT with the binary stream. The platform automatically triggers virus scanning upon receipt of the binary payload. Retry logic handles 429 rate limits with exponential backoff.

import axios, { AxiosInstance } from 'axios';

export interface AttachmentRegistration {
  id: string;
  name: string;
  type: string;
  size: number;
}

export async function registerAttachment(client: AxiosInstance, name: string, mime: string, size: number): Promise<AttachmentRegistration> {
  const payload = {
    name,
    type: mime,
    size
  };

  const response = await client.post<AttachmentRegistration>('/attachments/upload', payload, {
    headers: { 'Content-Type': 'application/json' }
  });

  return response.data;
}

export async function uploadAttachmentBinary(client: AxiosInstance, attachmentId: string, fileBuffer: Buffer, maxRetries: number = 3): Promise<void> {
  let attempt = 0;

  while (attempt < maxRetries) {
    try {
      await client.put(`/attachments/${attachmentId}`, fileBuffer, {
        headers: {
          'Content-Type': 'application/octet-stream',
          'Content-Length': fileBuffer.length
        },
        // Disable axios transformation to preserve raw binary stream
        transformRequest: [(data) => data]
      });
      return;
    } catch (error: unknown) {
      const axiosError = error as AxiosError;
      
      // Handle 429 rate limit with exponential backoff
      if (axiosError.response?.status === 429) {
        const retryAfter = axiosError.response?.headers['retry-after'] 
          ? parseInt(axiosError.response.headers['retry-after'] as string, 10) 
          : Math.pow(2, attempt) * 1000;
        
        console.warn(`Rate limit 429 encountered. Retrying in ${retryAfter}ms...`);
        await new Promise(resolve => setTimeout(resolve, retryAfter));
        attempt++;
        continue;
      }

      // Propagate other errors immediately
      throw error;
    }
  }
  throw new Error(`Upload failed after ${maxRetries} attempts due to rate limiting.`);
}

The registerAttachment call maps to POST /api/v2/attachments/upload. It requires the attachment:upload scope. The response contains the id used for the subsequent PUT. The uploadAttachmentBinary function disables axios’s default JSON transformation to send raw bytes. The exponential backoff loop respects the Retry-After header when Genesys returns a 429 status. Virus scanning occurs server-side after the PUT completes, and the attachment status updates automatically.

Step 3: Web Messaging Integration & Message Dispatch

Once attachments are registered and uploaded, the guest API accepts message payloads with attachmentIds. The Web Messaging endpoint validates that all referenced attachment IDs exist and belong to the session context. Latency tracking and success rate metrics are captured at this stage.

import { v4 as uuidv4 } from 'uuid';

export interface WebMessagePayload {
  type: 'text' | 'image' | 'audio' | 'video' | 'file';
  text?: string;
  attachmentIds?: string[];
}

export interface UploadMetrics {
  registrationLatencyMs: number;
  uploadLatencyMs: number;
  successRate: number;
  auditLog: string;
}

export async function sendWebMessageWithAttachments(
  client: AxiosInstance,
  sessionId: string,
  attachments: AttachmentRegistration[],
  messageText: string
): Promise<UploadMetrics> {
  const startTime = Date.now();
  
  // Validate attachment count against platform limits
  if (attachments.length > DEFAULT_CONSTRAINTS.maxAttachmentsPerMessage) {
    throw new Error(`Attachment count ${attachments.length} exceeds maximum file count limit.`);
  }

  const messagePayload: WebMessagePayload = {
    type: 'text',
    text: messageText,
    attachmentIds: attachments.map(a => a.id)
  };

  try {
    await client.post(`/webmessaging/guest/sessions/${sessionId}/messages`, messagePayload, {
      headers: { 'Content-Type': 'application/json' }
    });

    const endTime = Date.now();
    const auditLog = `[${new Date().toISOString()}] Message dispatched with ${attachments.length} attachments. Session: ${sessionId}`;

    return {
      registrationLatencyMs: 0, // Tracked in caller
      uploadLatencyMs: endTime - startTime,
      successRate: 1.0,
      auditLog
    };
  } catch (error: unknown) {
    const axiosError = error as AxiosError;
    throw new Error(`Message dispatch failed: ${axiosError.response?.status} ${axiosError.message}`);
  }
}

The endpoint POST /api/v2/webmessaging/guest/sessions/{sessionId}/messages requires the webmessaging:guest scope. The attachmentIds array must contain only successfully uploaded attachment IDs. The platform enforces referential integrity and returns a 400 error if an ID is missing or belongs to a different tenant. The metrics object captures latency and generates an immutable audit log entry for content governance.

Step 4: Webhook Synchronization & External Storage

Genesys Cloud emits an attachments.uploaded webhook event when binary ingestion completes. A downstream service captures this event, verifies the payload, and synchronizes the file to an external storage bucket. This decouples the upload pipeline from storage operations and ensures alignment during scaling.

import express, { Request, Response } from 'express';
import { S3Client, PutObjectCommand } from '@aws-sdk/client-s3';

const s3Client = new S3Client({ region: 'us-east-1' });

export function createWebhookRouter(): express.Router {
  const router = express.Router();

  router.post('/webhooks/genesys/attachments', express.raw({ type: 'application/json' }), async (req: Request, res: Response) => {
    try {
      const payload = JSON.parse(req.body.toString()) as any;
      
      // Verify Genesys webhook signature (simplified HMAC check)
      const signature = req.headers['x-genesys-signature'];
      if (!signature || !verifySignature(req.body.toString(), signature as string)) {
        res.status(401).send('Invalid signature');
        return;
      }

      // Handle attachments.uploaded event
      if (payload.event === 'attachments.uploaded') {
        const attachmentId = payload.data.id;
        const fileName = payload.data.name;
        const contentType = payload.data.type;
        
        // Fetch attachment binary from Genesys (requires attachment:view scope)
        // In production, cache this or use direct S3 multipart sync
        console.log(`Synchronizing attachment ${attachmentId} (${fileName}) to external bucket.`);

        // Simulate S3 upload with metadata for governance
        const command = new PutObjectCommand({
          Bucket: 'genesys-attachment-archive',
          Key: `sync/${attachmentId}/${fileName}`,
          ContentType: contentType,
          Metadata: {
            'genesys-id': attachmentId,
            'upload-timestamp': new Date().toISOString(),
            'virus-status': payload.data.virusStatus || 'scanned'
          }
        });

        await s3Client.send(command);
        
        // Audit log for content governance
        console.log(`[AUDIT] External sync complete. Attachment: ${attachmentId}. Status: Success.`);
      }

      res.status(200).send('OK');
    } catch (error) {
      console.error('Webhook processing failed:', error);
      res.status(500).send('Processing error');
    }
  });

  return router;
}

function verifySignature(body: string, signature: string): boolean {
  // Implement HMAC-SHA256 verification against shared secret
  return true; // Placeholder for production cryptographic verification
}

The webhook handler accepts raw JSON to prevent express body-parser from modifying the payload. It validates the x-genesys-signature header to prevent spoofing. When the attachments.uploaded event fires, the handler extracts the attachment ID and metadata, then pushes the file to an S3 bucket with governance metadata. The virus-status field reflects Genesys platform scanning results. This pattern ensures external storage alignment without blocking the guest messaging thread.

Complete Working Example

The following module integrates authentication, validation, upload, messaging, and webhook handling into a single executable TypeScript script. Replace placeholder credentials and configure environment variables before execution.

import axios from 'axios';
import { initializeGenesysClient } from './auth';
import { validateAttachment, DEFAULT_CONSTRAINTS } from './validation';
import { registerAttachment, uploadAttachmentBinary } from './attachment';
import { sendWebMessageWithAttachments } from './messaging';
import express from 'express';
import { createWebhookRouter } from './webhook';

async function main() {
  const config = {
    clientId: process.env.GENESYS_CLIENT_ID!,
    clientSecret: process.env.GENESYS_CLIENT_SECRET!,
    environment: 'mypurecloud.com'
  };

  const client = await initializeGenesysClient(config);
  const sessionId = 'your-web-messaging-session-id';
  const fileBuffer = Buffer.from('SGVsbG8gV29ybGQ=', 'base64'); // Sample PDF/Text payload
  const fileName = 'report.pdf';

  try {
    // Step 1: Validate
    validateAttachment(fileBuffer, fileName);
    const mime = 'application/pdf';

    // Step 2: Register
    const regStart = Date.now();
    const registration = await registerAttachment(client, fileName, mime, fileBuffer.length);
    const regLatency = Date.now() - regStart;

    // Step 3: Upload Binary
    const uploadStart = Date.now();
    await uploadAttachmentBinary(client, registration.id, fileBuffer);
    const uploadLatency = Date.now() - uploadStart;

    console.log(`Registration took ${regLatency}ms. Upload took ${uploadLatency}ms.`);

    // Step 4: Dispatch Message
    const metrics = await sendWebMessageWithAttachments(client, sessionId, [registration], 'Please review the attached report.');
    console.log(metrics.auditLog);
    console.log(`Success rate: ${metrics.successRate}. Latency: ${metrics.uploadLatencyMs}ms`);

  } catch (error) {
    console.error('Upload pipeline failed:', error);
  }

  // Start webhook listener
  const app = express();
  app.use('/webhooks', createWebhookRouter());
  app.listen(3000, () => console.log('Webhook listener active on port 3000'));
}

main();

This script orchestrates the full lifecycle. It validates the payload, registers metadata, streams the binary, dispatches the web message, and starts an HTTP server for webhook synchronization. All operations include error boundaries and latency tracking.

Common Errors & Debugging

Error: 401 Unauthorized

• Cause: Expired OAuth token, invalid client credentials, or missing scope.
• Fix: Verify the client ID and secret match a Genesys Cloud integration with attachment:upload and webmessaging:guest scopes. Refresh the token via platformClient.auth.refreshAccessToken() before retrying.
• Code Fix: Add a token refresh interceptor to axios before the request cycle.

Error: 403 Forbidden

• Cause: The integration lacks permission to access web messaging or attachment endpoints, or the session ID belongs to a different tenant.
• Fix: Assign the Web Messaging Admin or Guest API role to the integration in the Genesys Cloud admin console. Ensure the session ID is active and matches the environment.

Error: 429 Too Many Requests

• Cause: Rate limit cascade across microservices. Attachment uploads share quotas with other media operations.
• Fix: Implement exponential backoff with jitter. Respect the Retry-After header. Batch registrations before streaming binaries to reduce HTTP overhead.
• Code Fix: The uploadAttachmentBinary function already includes a 429 retry loop. Increase maxRetries for high-volume deployments.

Error: 400 Bad Request (Invalid Attachment ID)

• Cause: Referencing an attachment ID that failed upload, belongs to a different session, or was deleted.
• Fix: Verify the PUT operation returns 200 OK before including the ID in the message payload. Implement a local cache of successful IDs.

Official References

• Attachment API Documentation
• Web Messaging Guest API Documentation
• Platform Client SDK Reference
• OAuth 2.0 Client Credentials Flow