Configuring NICE CXone Pure Connect DID Ranges via Pure Connect APIs with Go

What You Will Build

• This program automates bulk DID range provisioning, validates telephony constraints, checks license capacity, and triggers trunk binding in NICE CXone Pure Connect.
• The solution uses the NICE CXone Pure Connect Telephony Numbers and Administration REST APIs.
• The implementation is written in Go 1.21+ using only the standard library.

Prerequisites

• OAuth client type and required scopes: Client Credentials grant. Required scopes: telephony:numbers:write, telephony:numbers:read, admin:licenses:read
• SDK version or API version: Pure Connect REST API v2, Go 1.21+
• Language/runtime requirements: Go 1.21+, standard net/http, encoding/json, log/slog, time, context packages
• Any external dependencies: None. The implementation relies exclusively on the Go standard library to minimize supply chain risk in production environments.

Authentication Setup

NICE CXone uses OAuth 2.0 Client Credentials flow. The token endpoint requires a client_id, client_secret, and grant_type=client_credentials. Tokens expire after a defined window, so the implementation includes a thread-safe cache with automatic refresh logic to prevent 401 interruptions during bulk operations.

The following function handles token acquisition and caching. It uses a mutex to prevent concurrent refresh calls and stores the token in memory with an expiration buffer.

package main

import (
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"io"
	"log/slog"
	"net/http"
	"strings"
	"sync"
	"time"
)

const (
	cxoneBaseURL       = "https://api-us-1.cxone.com"
	oauthTokenEndpoint = "/oauth/token"
)

type OAuthConfig struct {
	ClientID     string
	ClientSecret string
	Region       string
}

type TokenResponse struct {
	AccessToken string `json:"access_token"`
	TokenType   string `json:"token_type"`
	ExpiresIn   int    `json:"expires_in"`
}

type TokenCache struct {
	mu          sync.RWMutex
	token       string
	expiresAt   time.Time
	httpClient  *http.Client
	oauthConfig OAuthConfig
}

func NewTokenCache(cfg OAuthConfig) *TokenCache {
	return &TokenCache{
		httpClient:  &http.Client{Timeout: 10 * time.Second},
		oauthConfig: cfg,
	}
}

func (tc *TokenCache) GetToken(ctx context.Context) (string, error) {
	tc.mu.RLock()
	if time.Until(tc.expiresAt) > 5*time.Minute {
		token := tc.token
		tc.mu.RUnlock()
		return token, nil
	}
	tc.mu.RUnlock()

	tc.mu.Lock()
	defer tc.mu.Unlock()

	if time.Until(tc.expiresAt) > 5*time.Minute {
		return tc.token, nil
	}

	return tc.refreshToken(ctx)
}

func (tc *TokenCache) refreshToken(ctx context.Context) (string, error) {
	payload := fmt.Sprintf("grant_type=client_credentials&client_id=%s&client_secret=%s",
		tc.oauthConfig.ClientID, tc.oauthConfig.ClientSecret)

	req, err := http.NewRequestWithContext(ctx, http.MethodPost, cxoneBaseURL+oauthTokenEndpoint, strings.NewReader(payload))
	if err != nil {
		return "", fmt.Errorf("failed to create oauth request: %w", err)
	}
	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")

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

	if resp.StatusCode != http.StatusOK {
		body, _ := io.ReadAll(resp.Body)
		return "", fmt.Errorf("oauth failed with status %d: %s", resp.StatusCode, string(body))
	}

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

	tc.token = tokenResp.AccessToken
	tc.expiresAt = time.Now().Add(time.Duration(tokenResp.ExpiresIn)*time.Second - 5*time.Minute)
	return tc.token, nil
}

Implementation

Step 1: Schema Validation & Telephony Constraint Checking

Pure Connect enforces strict telephony constraints. Bulk range operations fail immediately if the number matrix exceeds maximum range size limits, violates E.164 formatting, or contains invalid numbering plan prefixes. The validation pipeline runs locally before any network request to conserve API quota and prevent 400 Bad Request responses.

The ValidateDIDRange function checks E.164 compliance, enforces a maximum range size of 200 numbers per atomic request, and verifies that the start and end numbers share the same numbering plan prefix.

import (
	"fmt"
	"regexp"
	"strconv"
)

const maxRangeSize = 200

var e164Regex = regexp.MustCompile(`^\+?[1-9]\d{1,14}$`)

type RangeValidation struct {
	IsE164Valid   bool
	IsWithinLimit bool
	HasSamePrefix bool
	Count         int
}

func ValidateDIDRange(startNumber, endNumber string) (RangeValidation, error) {
	startClean := strings.ReplaceAll(startNumber, "+", "")
	endClean := strings.ReplaceAll(endNumber, "+", "")

	if !e164Regex.MatchString(startNumber) || !e164Regex.MatchString(endNumber) {
		return RangeValidation{IsE164Valid: false}, nil
	}

	startInt, err1 := strconv.ParseInt(startClean, 10, 64)
	endInt, err2 := strconv.ParseInt(endClean, 10, 64)
	if err1 != nil || err2 != nil {
		return RangeValidation{}, fmt.Errorf("invalid number format: %w", err1)
	}

	if endInt < startInt {
		return RangeValidation{}, fmt.Errorf("end number must be greater than start number")
	}

	count := int(endInt-startInt) + 1
	if count > maxRangeSize {
		return RangeValidation{IsWithinLimit: false, Count: count}, nil
	}

	prefixLen := 6
	if len(startClean) < prefixLen || len(endClean) < prefixLen {
		return RangeValidation{HasSamePrefix: false}, nil
	}

	return RangeValidation{
		IsE164Valid:   true,
		IsWithinLimit: true,
		HasSamePrefix: startClean[:prefixLen] == endClean[:prefixLen],
		Count:         count,
	}, nil
}

Step 2: License Capacity Verification & Number Conflict Prevention

Provisioning DIDs beyond allocated telephony license capacity triggers a 403 Forbidden response. The implementation queries the administration license endpoint to verify available capacity before constructing the assignment payload. This prevents wasted API calls and ensures scaling operations respect organizational billing limits.

type LicenseCapacityResponse struct {
	Telephony struct {
		Assigned   int `json:"assigned"`
		Total      int `json:"total"`
		Available  int `json:"available"`
	} `json:"telephony"`
}

func CheckLicenseCapacity(ctx context.Context, token string, requiredCount int) error {
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, cxoneBaseURL+"/api/v2/admin/licenses", nil)
	if err != nil {
		return fmt.Errorf("failed to create license check request: %w", err)
	}
	req.Header.Set("Authorization", "Bearer "+token)
	req.Header.Set("Accept", "application/json")

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

	if resp.StatusCode != http.StatusOK {
		body, _ := io.ReadAll(resp.Body)
		return fmt.Errorf("license check returned %d: %s", resp.StatusCode, string(body))
	}

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

	if capacity.Telephony.Available < requiredCount {
		return fmt.Errorf("insufficient license capacity: available %d, required %d",
			capacity.Telephony.Available, requiredCount)
	}

	return nil
}

Step 3: Atomic Payload Construction & POST Execution with Retry Logic

Pure Connect requires atomic POST operations for range assignments. The payload must include an assignDirective, numberMatrix, and didReferences array containing trunk and routing policy identifiers. The implementation constructs this payload, attaches an idempotency key to prevent duplicate provisioning on retry, and implements exponential backoff for 429 Too Many Requests responses.

Required OAuth scope: telephony:numbers:write

type AssignPayload struct {
	AssignDirective string `json:"assignDirective"`
	NumberMatrix    struct {
		StartNumber string `json:"startNumber"`
		EndNumber   string `json:"endNumber"`
		Step        int    `json:"step"`
	} `json:"numberMatrix"`
	DIDReferences []struct {
		TrunkID          string `json:"trunkId"`
		RoutingPolicyID  string `json:"routingPolicyId"`
		AutomaticBinding bool   `json:"automaticTrunkBinding"`
	} `json:"didReferences"`
}

type AssignmentResult struct {
	Success     bool
	Latency     time.Duration
	StatusCode  int
	ResponseBody []byte
}

func AssignDIDRange(ctx context.Context, token string, payload AssignPayload) AssignmentResult {
	start := time.Now()
	jsonBody, _ := json.Marshal(payload)

	maxRetries := 3
	var lastErr error

	for attempt := 0; attempt <= maxRetries; attempt++ {
		req, err := http.NewRequestWithContext(ctx, http.MethodPost,
			cxoneBaseURL+"/api/v2/telephony/numbers/ranges/assign", bytes.NewReader(jsonBody))
		if err != nil {
			return AssignmentResult{Success: false, Latency: time.Since(start), ResponseBody: []byte(err.Error())}
		}

		req.Header.Set("Authorization", "Bearer "+token)
		req.Header.Set("Content-Type", "application/json")
		req.Header.Set("Accept", "application/json")
		req.Header.Set("Idempotency-Key", fmt.Sprintf("did-assign-%d-%s", time.Now().UnixNano(), payload.NumberMatrix.StartNumber))

		resp, err := http.DefaultClient.Do(req)
		if err != nil {
			lastErr = err
			continue
		}

		body, _ := io.ReadAll(resp.Body)
		resp.Body.Close()

		if resp.StatusCode == http.StatusTooManyRequests {
			waitTime := time.Duration(1<<uint(attempt)) * time.Second
			slog.Warn("rate limited, retrying", "attempt", attempt, "wait", waitTime)
			time.Sleep(waitTime)
			continue
		}

		if resp.StatusCode >= 200 && resp.StatusCode < 300 {
			return AssignmentResult{
				Success:      true,
				Latency:      time.Since(start),
				StatusCode:   resp.StatusCode,
				ResponseBody: body,
			}
		}

		lastErr = fmt.Errorf("assignment failed with status %d: %s", resp.StatusCode, string(body))
		break
	}

	return AssignmentResult{
		Success:      false,
		Latency:      time.Since(start),
		StatusCode:   0,
		ResponseBody: []byte(lastErr.Error()),
	}
}

Step 4: Audit Logging, Latency Tracking, & Webhook Synchronization

Telephony governance requires immutable audit trails. The implementation records every assignment attempt with structured logging, captures latency metrics, calculates success rates, and synchronizes successful configurations with external billing systems via webhook POST requests. This ensures financial alignment and operational visibility.

type ConfiguratorMetrics struct {
	mu           sync.Mutex
	TotalRuns    int
	Successful   int
	TotalLatency time.Duration
}

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

func (m *ConfiguratorMetrics) GetSuccessRate() float64 {
	m.mu.Lock()
	defer m.mu.Unlock()
	if m.TotalRuns == 0 {
		return 0.0
	}
	return float64(m.Successful) / float64(m.TotalRuns)
}

func SyncBillingWebhook(ctx context.Context, webhookURL string, payload AssignPayload) error {
	jsonBody, _ := json.Marshal(map[string]interface{}{
		"event":        "did_range_configured",
		"timestamp":    time.Now().UTC().Format(time.RFC3339),
		"assignDetail": payload,
	})

	req, err := http.NewRequestWithContext(ctx, http.MethodPost, webhookURL, bytes.NewReader(jsonBody))
	if err != nil {
		return fmt.Errorf("webhook request creation failed: %w", err)
	}
	req.Header.Set("Content-Type", "application/json")

	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		return fmt.Errorf("webhook delivery 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
}

Complete Working Example

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

package main

import (
	"context"
	"fmt"
	"log/slog"
	"os"
	"time"
)

func main() {
	ctx := context.Background()

	// Initialize structured logger
	slog.SetDefault(slog.New(slog.NewJSONHandler(os.Stdout, nil)))

	// Configuration
	cfg := OAuthConfig{
		ClientID:     "YOUR_CLIENT_ID",
		ClientSecret: "YOUR_CLIENT_SECRET",
		Region:       "us-1",
	}

	cache := NewTokenCache(cfg)
	metrics := &ConfiguratorMetrics{}

	// DID Range Parameters
	startDID := "+18005550100"
	endDID := "+18005550150"
	trunkID := "trk-nice-telephony-001"
	routingPolicyID := "pol-inbound-sales-001"
	webhookURL := "https://billing.example.com/webhooks/cxone-did-sync"

	// Step 1: Validate Schema & Constraints
	slog.Info("validating did range constraints", "start", startDID, "end", endDID)
	validation, err := ValidateDIDRange(startDID, endDID)
	if err != nil {
		slog.Error("validation error", "error", err)
		os.Exit(1)
	}

	if !validation.IsE164Valid || !validation.IsWithinLimit || !validation.HasSamePrefix {
		slog.Error("range failed validation", "validation", validation)
		os.Exit(1)
	}

	// Step 2: Acquire Token & Check License Capacity
	slog.Info("acquiring oauth token")
	token, err := cache.GetToken(ctx)
	if err != nil {
		slog.Error("oauth token acquisition failed", "error", err)
		os.Exit(1)
	}

	slog.Info("checking license capacity", "required", validation.Count)
	if err := CheckLicenseCapacity(ctx, token, validation.Count); err != nil {
		slog.Error("license capacity check failed", "error", err)
		os.Exit(1)
	}

	// Step 3: Construct Payload & Execute Atomic Assignment
	payload := AssignPayload{
		AssignDirective: "PROVISION_AND_BIND",
		NumberMatrix: struct {
			StartNumber string `json:"startNumber"`
			EndNumber   string `json:"endNumber"`
			Step        int    `json:"step"`
		}{
			StartNumber: startDID,
			EndNumber:   endDID,
			Step:        1,
		},
		DIDReferences: []struct {
			TrunkID          string `json:"trunkId"`
			RoutingPolicyID  string `json:"routingPolicyId"`
			AutomaticBinding bool   `json:"automaticTrunkBinding"`
		}{
			{
				TrunkID:          trunkID,
				RoutingPolicyID:  routingPolicyID,
				AutomaticBinding: true,
			},
		},
	}

	slog.Info("executing atomic did assignment", "range_size", validation.Count)
	result := AssignDIDRange(ctx, token, payload)

	metrics.Record(result.Success, result.Latency)

	if result.Success {
		slog.Info("assignment succeeded", "latency", result.Latency, "status", result.StatusCode)

		// Step 4: Sync with External Billing System
		slog.Info("triggering billing webhook sync")
		if err := SyncBillingWebhook(ctx, webhookURL, payload); err != nil {
			slog.Warn("webhook sync failed", "error", err)
		}
	} else {
		slog.Error("assignment failed", "latency", result.Latency, "response", string(result.ResponseBody))
	}

	// Step 5: Output Audit Metrics
	slog.Info("configuration audit summary",
		"total_runs", metrics.TotalRuns,
		"success_rate", metrics.GetSuccessRate(),
		"avg_latency", metrics.TotalLatency/time.Duration(metrics.TotalRuns))
}

Common Errors & Debugging

Error: 401 Unauthorized

• What causes it: The OAuth token expired during a long-running batch operation, or the client credentials are invalid.
• How to fix it: Ensure the TokenCache refresh logic runs before every request. Verify that the client_id and client_secret match a registered Machine-to-Machine application in the CXone admin console.
• Code showing the fix: The GetToken method in the authentication section automatically refreshes tokens that expire within a 5-minute buffer.

Error: 403 Forbidden

• What causes it: The OAuth token lacks the telephony:numbers:write scope, or the account has exhausted its telephony license capacity.
• How to fix it: Attach the correct scopes to the M2M client. Run the CheckLicenseCapacity function before assignment to verify available seats.
• Code showing the fix: The CheckLicenseCapacity function queries /api/v2/admin/licenses and halts execution if capacity.Telephony.Available < requiredCount.

Error: 400 Bad Request

• What causes it: The number matrix violates E.164 formatting, exceeds the 200-number maximum range limit, or mixes numbering plan prefixes.
• How to fix it: Pre-validate ranges using the ValidateDIDRange function. Split ranges larger than 200 into separate atomic POST requests.
• Code showing the fix: The validation pipeline returns structured boolean flags that halt execution before network transmission.

Error: 429 Too Many Requests

• What causes it: Pure Connect enforces rate limits on telephony configuration endpoints. Bulk operations without backoff trigger cascading failures.
• How to fix it: Implement exponential backoff with idempotency keys to safely retry failed requests.
• Code showing the fix: The AssignDIDRange function retries up to three times with 1<<uint(attempt) second delays and attaches a unique Idempotency-Key header.

Official References

• NICE CXone Pure Connect API Documentation
• Telephony Numbers REST API v2
• OAuth 2.0 Client Credentials Flow
• Administration & License Management API