Validating NICE CXone Digital API Viber Keyboard Layouts with Go

What You Will Build

A Go service that constructs and validates Viber keyboard payloads against CXone Digital API constraints, verifies button matrices and deep links, tracks validation metrics, and exposes a REST validator endpoint for automated pipeline integration. The application uses the CXone Digital REST API, implements local schema enforcement, handles atomic validation POST requests, syncs results to external UI testing suites via webhooks, and maintains audit logs for interface governance.

Prerequisites

• CXone OAuth 2.0 Client Credentials grant configuration
• Required scopes: digital:messages:validate, digital:channels:read
• Go 1.21 or later
• Standard library dependencies: net/http, net/url, encoding/json, sync, time, log, os, io
• Access to a CXone Digital environment with Viber channel provisioning

Authentication Setup

CXone uses OAuth 2.0 Client Credentials flow. The authentication endpoint returns a bearer token that expires after one hour. You must cache the token and refresh it before expiration to avoid 401 errors during validation pipelines.

package main

import (
	"bytes"
	"encoding/json"
	"fmt"
	"net/http"
	"sync"
	"time"
)

type OAuthToken struct {
	AccessToken string `json:"access_token"`
	ExpiresIn   int    `json:"expires_in"`
	TokenType   string `json:"token_type"`
	FetchedAt   time.Time
}

type OAuthClient struct {
	ClientID     string
	ClientSecret string
	AuthURL      string
	Token        *OAuthToken
	mu           sync.RWMutex
	httpClient   *http.Client
}

func NewOAuthClient(clientID, clientSecret, authURL string) *OAuthClient {
	return &OAuthClient{
		ClientID:     clientID,
		ClientSecret: clientSecret,
		AuthURL:      authURL,
		httpClient:   &http.Client{Timeout: 10 * time.Second},
	}
}

func (o *OAuthClient) GetToken() (*OAuthToken, error) {
	o.mu.RLock()
	if o.Token != nil && time.Since(o.Token.FetchedAt) < time.Duration(o.Token.ExpiresIn-30)*time.Second {
		defer o.mu.RUnlock()
		return o.Token, nil
	}
	o.mu.RUnlock()

	o.mu.Lock()
	defer o.mu.Unlock()
	if o.Token != nil && time.Since(o.Token.FetchedAt) < time.Duration(o.Token.ExpiresIn-30)*time.Second {
		return o.Token, nil
	}

	payload := fmt.Sprintf("grant_type=client_credentials&client_id=%s&client_secret=%s", o.ClientID, o.ClientSecret)
	req, err := http.NewRequest(http.MethodPost, o.AuthURL, bytes.NewBufferString(payload))
	if err != nil {
		return nil, fmt.Errorf("failed to create auth request: %w", err)
	}
	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")

	resp, err := o.httpClient.Do(req)
	if err != nil {
		return nil, fmt.Errorf("auth request failed: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		return nil, fmt.Errorf("auth failed with status %d", resp.StatusCode)
	}

	var token OAuthToken
	if err := json.NewDecoder(resp.Body).Decode(&token); err != nil {
		return nil, fmt.Errorf("failed to decode token response: %w", err)
	}
	token.FetchedAt = time.Now()
	o.Token = &token
	return o.Token, nil
}

Implementation

Step 1: Local Schema Validation and Keyboard Construction

Viber imposes strict client-side constraints: maximum three rows, maximum three buttons per row, total button count not exceeding nine, and specific action types (open-url, reply, call). Deep links must be absolute URLs. This step enforces those constraints before sending to CXone.

type ViberButton struct {
	ColumnSpan int    `json:"column_span,omitempty"`
	RowSpan    int    `json:"row_span,omitempty"`
	Size       string `json:"size,omitempty"`
	Type       string `json:"type"`
	Text       string `json:"text"`
	ActionType string `json:"action_type"`
	ActionBody string `json:"action_body"`
}

type ViberKeyboard struct {
	Type   string          `json:"type"`
	Buttons [][]ViberButton `json:"buttons"`
}

type ValidationPayload struct {
	ChannelID string        `json:"channelId"`
	Message   ViberKeyboard `json:"message"`
}

func ValidateKeyboardConstraints(kb ViberKeyboard) error {
	if kb.Type != "keyboard" {
		return fmt.Errorf("invalid keyboard type: %s", kb.Type)
	}
	if len(kb.Buttons) == 0 || len(kb.Buttons) > 3 {
		return fmt.Errorf("keyboard must have 1 to 3 rows, got %d", len(kb.Buttons))
	}

	totalButtons := 0
	for rowIndex, row := range kb.Buttons {
		if len(row) > 3 {
			return fmt.Errorf("row %d exceeds maximum 3 buttons", rowIndex)
		}
		totalButtons += len(row)
		for colIndex, btn := range row {
			if btn.Type != "button" {
				return fmt.Errorf("invalid button type in row %d col %d", rowIndex, colIndex)
			}
			if btn.ActionType != "open-url" && btn.ActionType != "reply" && btn.ActionType != "call" {
				return fmt.Errorf("invalid action_type: %s", btn.ActionType)
			}
			if btn.ActionType == "open-url" {
				if _, err := url.ParseRequestURI(btn.ActionBody); err != nil {
					return fmt.Errorf("invalid deep link in row %d col %d: %w", rowIndex, colIndex, err)
				}
			}
		}
	}
	if totalButtons > 9 {
		return fmt.Errorf("keyboard exceeds maximum 9 buttons, got %d", totalButtons)
	}
	return nil
}

Step 2: CXone Digital API Validation POST with Retry Logic

The CXone Digital API validates message payloads against channel capabilities. You must send the constructed keyboard to /api/v1/digital/messages/validate. The endpoint returns a structured response indicating approval or specific rule violations. You must implement retry logic for 429 rate limit responses.

type CXoneValidationResponse struct {
	Success   bool              `json:"success"`
	Errors    []CXoneError      `json:"errors,omitempty"`
	Warnings  []string          `json:"warnings,omitempty"`
	Validated bool              `json:"validated"`
}

type CXoneError struct {
	Code    string `json:"code"`
	Message string `json:"message"`
	Path    string `json:"path,omitempty"`
}

func SendToCXoneValidator(client *http.Client, token *OAuthToken, payload ValidationPayload, baseURL string) (*CXoneValidationResponse, error) {
	jsonPayload, err := json.Marshal(payload)
	if err != nil {
		return nil, fmt.Errorf("failed to marshal payload: %w", err)
	}

	endpoint := fmt.Sprintf("%s/api/v1/digital/messages/validate", baseURL)
	maxRetries := 3
	var lastErr error

	for attempt := 0; attempt <= maxRetries; attempt++ {
		req, err := http.NewRequest(http.MethodPost, endpoint, bytes.NewBuffer(jsonPayload))
		if err != nil {
			return nil, fmt.Errorf("request creation failed: %w", err)
		}
		req.Header.Set("Content-Type", "application/json")
		req.Header.Set("Authorization", fmt.Sprintf("Bearer %s", token.AccessToken))
		req.Header.Set("Accept", "application/json")

		resp, err := client.Do(req)
		if err != nil {
			return nil, fmt.Errorf("http request failed: %w", err)
		}
		defer resp.Body.Close()

		if resp.StatusCode == http.StatusTooManyRequests {
			retryAfter := 2 * time.Duration(attempt+1)
			log.Printf("Received 429, retrying in %v seconds", retryAfter)
			time.Sleep(retryAfter * time.Second)
			lastErr = fmt.Errorf("rate limited")
			continue
		}

		if resp.StatusCode >= 500 {
			return nil, fmt.Errorf("server error: %d", resp.StatusCode)
		}

		var cxoneResp CXoneValidationResponse
		if err := json.NewDecoder(resp.Body).Decode(&cxoneResp); err != nil {
			return nil, fmt.Errorf("failed to decode CXone response: %w", err)
		}

		if resp.StatusCode == http.StatusBadRequest {
			return &cxoneResp, fmt.Errorf("CXone validation failed: %v", cxoneResp.Errors)
		}

		return &cxoneResp, nil
	}

	return nil, fmt.Errorf("exceeded retry limit: %w", lastErr)
}

Step 3: Webhook Sync, Latency Tracking, and Audit Logging

You must synchronize validation events with external UI testing suites, track latency and success rates, and generate audit logs. This step implements a metrics tracker and a webhook dispatcher.

type MetricsTracker struct {
	mu             sync.RWMutex
	TotalRequests  int64
	Successful     int64
	TotalLatency   time.Duration
	LastValidation time.Time
}

func (m *MetricsTracker) Record(latency time.Duration, success bool) {
	m.mu.Lock()
	defer m.mu.Unlock()
	m.TotalRequests++
	if success {
		m.Successful++
	}
	m.TotalLatency += latency
	m.LastValidation = time.Now()
}

func (m *MetricsTracker) GetSuccessRate() float64 {
	m.mu.RLock()
	defer m.mu.RUnlock()
	if m.TotalRequests == 0 {
		return 0.0
	}
	return float64(m.Successful) / float64(m.TotalRequests)
}

func (m *MetricsTracker) GetAvgLatency() time.Duration {
	m.mu.RLock()
	defer m.mu.RUnlock()
	if m.TotalRequests == 0 {
		return 0
	}
	return m.TotalLatency / time.Duration(m.TotalRequests)
}

func WriteAuditLog(logFile string, event string, payload interface{}) error {
	f, err := os.OpenFile(logFile, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0600)
	if err != nil {
		return fmt.Errorf("failed to open audit log: %w", err)
	}
	defer f.Close()

	auditEntry := map[string]interface{}{
		"timestamp": time.Now().UTC().Format(time.RFC3339),
		"event":     event,
		"payload":   payload,
	}
	data, _ := json.Marshal(auditEntry)
	_, err = f.Write(append(data, '\n'))
	return err
}

func DispatchWebhook(webhookURL string, data map[string]interface{}) error {
	if webhookURL == "" {
		return nil
	}
	jsonData, _ := json.Marshal(data)
	req, _ := http.NewRequest(http.MethodPost, webhookURL, bytes.NewBuffer(jsonData))
	req.Header.Set("Content-Type", "application/json")
	client := &http.Client{Timeout: 5 * time.Second}
	resp, err := client.Do(req)
	if err != nil {
		return fmt.Errorf("webhook dispatch failed: %w", err)
	}
	defer resp.Body.Close()
	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
		return fmt.Errorf("webhook returned non-2xx status: %d", resp.StatusCode)
	}
	return nil
}

Step 4: Exposing the Keyboard Validator HTTP Handler

You must expose a REST endpoint that accepts keyboard definitions, runs local constraints, calls CXone, records metrics, logs the audit trail, and triggers webhook synchronization.

type ValidatorService struct {
	OAuth      *OAuthClient
	CXoneBase  string
	WebhookURL string
	LogFile    string
	Metrics    *MetricsTracker
	HTTPClient *http.Client
}

func (v *ValidatorService) HandleValidation(w http.ResponseWriter, r *http.Request) {
	start := time.Now()
	w.Header().Set("Content-Type", "application/json")

	var payload ValidationPayload
	if err := json.NewDecoder(r.Body).Decode(&payload); err != nil {
		http.Error(w, fmt.Sprintf("Invalid JSON payload: %v", err), http.StatusBadRequest)
		return
	}

	if err := ValidateKeyboardConstraints(payload.Message); err != nil {
		http.Error(w, fmt.Sprintf("Local validation failed: %v", err), http.StatusBadRequest)
		return
	}

	token, err := v.OAuth.GetToken()
	if err != nil {
		http.Error(w, fmt.Sprintf("Authentication failed: %v", err), http.StatusUnauthorized)
		return
	}

	resp, err := SendToCXoneValidator(v.HTTPClient, token, payload, v.CXoneBase)
	latency := time.Since(start)
	success := err == nil && resp.Success

	v.Metrics.Record(latency, success)
	
	auditEvent := map[string]interface{}{
		"channelId": payload.ChannelID,
		"success":   success,
		"latencyMs": latency.Milliseconds(),
		"errors":    resp.Errors,
	}
	_ = WriteAuditLog(v.LogFile, "viber_keyboard_validation", auditEvent)

	_ = DispatchWebhook(v.WebhookURL, auditEvent)

	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}

	w.WriteHeader(http.StatusOK)
	json.NewEncoder(w).Encode(map[string]interface{}{
		"validated": resp.Validated,
		"warnings":  resp.Warnings,
		"latencyMs": latency.Milliseconds(),
		"metrics": map[string]interface{}{
			"success_rate": v.Metrics.GetSuccessRate(),
			"avg_latency":  v.Metrics.GetAvgLatency().String(),
		},
	})
}

Complete Working Example

The following script combines all components into a single executable service. Replace the placeholder credentials before execution.

package main

import (
	"encoding/json"
	"fmt"
	"log"
	"net/http"
	"os"
	"time"
)

func main() {
	clientID := os.Getenv("CXONE_CLIENT_ID")
	clientSecret := os.Getenv("CXONE_CLIENT_SECRET")
	cxoneBase := os.Getenv("CXONE_API_BASE")
	webhookURL := os.Getenv("WEBHOOK_URL")
	logFile := os.Getenv("AUDIT_LOG_PATH")

	if clientID == "" || clientSecret == "" || cxoneBase == "" {
		log.Fatal("Required environment variables: CXONE_CLIENT_ID, CXONE_CLIENT_SECRET, CXONE_API_BASE")
	}
	if logFile == "" {
		logFile = "validation_audit.log"
	}

	oauth := NewOAuthClient(clientID, clientSecret, "https://auth.niceincontact.com/connect/token")
	service := &ValidatorService{
		OAuth:      oauth,
		CXoneBase:  cxoneBase,
		WebhookURL: webhookURL,
		LogFile:    logFile,
		Metrics:    &MetricsTracker{},
		HTTPClient: &http.Client{Timeout: 15 * time.Second},
	}

	http.HandleFunc("/validate/keyboard", service.HandleValidation)
	http.HandleFunc("/metrics", func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Content-Type", "application/json")
		json.NewEncoder(w).Encode(map[string]interface{}{
			"total_requests": service.Metrics.TotalRequests,
			"success_rate":   service.Metrics.GetSuccessRate(),
			"avg_latency":    service.Metrics.GetAvgLatency().String(),
			"last_run":       service.Metrics.LastValidation.Format(time.RFC3339),
		})
	})

	fmt.Println("Viber Keyboard Validator running on :8080")
	log.Fatal(http.ListenAndServe(":8080", nil))
}

Common Errors & Debugging

Error: 401 Unauthorized

• Cause: Expired OAuth token or invalid client credentials. The token cache returns a token past its expires_in window.
• Fix: Verify environment variables. Ensure the OAuth client has the digital:messages:validate scope assigned in the CXone admin console. The caching logic subtracts 30 seconds from expiry to prevent edge-case expiration.
• Code Fix: The GetToken() method already handles refresh. If persistent, clear the token cache and re-authenticate.

Error: 400 Bad Request with CXone Validation Errors

• Cause: Payload violates CXone message schema or Viber channel constraints. Common issues include missing channelId, unsupported action_type, or malformed JSON structure.
• Fix: Inspect the errors array in the response. Ensure channelId matches an active Viber channel in CXone. Verify button action_body matches action_type requirements.
• Debug Step: Print the raw request body before sending. Compare against the CXone Digital API message validation schema.

Error: 429 Too Many Requests

• Cause: Exceeding CXone API rate limits. Validation pipelines running in parallel can trigger throttling.
• Fix: The retry loop implements exponential backoff. Reduce concurrent validation requests. Implement a request queue if scaling to high throughput.
• Code Fix: The SendToCXoneValidator function already retries up to three times with increasing delays. Adjust maxRetries if your workload requires longer recovery windows.

Error: Local Constraint Violation (Row/Column Limits)

• Cause: Keyboard exceeds Viber client limits (more than 3 rows, more than 3 buttons per row, or total buttons over 9).
• Fix: Flatten or restructure the keyboard matrix. Viber does not support spanning across the maximum grid. Adjust column_span and row_span to fit within the 3x3 boundary.
• Debug Step: Run ValidateKeyboardConstraints(kb) independently in a test function before integrating with the HTTP handler.

Official References

• NICE CXone Digital API Message Validation Documentation
• NICE CXone OAuth 2.0 Client Credentials Flow
• Viber Bot API Keyboard Specifications
• CXone Digital API Scopes Reference