update

workflow/advanced_processors.go

@@ -0,0 +1,961 @@
+package workflow
+
+import (
+	"context"
+	"crypto/hmac"
+	"crypto/sha256"
+	"encoding/hex"
+	"encoding/json"
+	"fmt"
+	"html/template"
+	"regexp"
+	"strconv"
+	"strings"
+	"time"
+)
+
+// SubDAGProcessor handles sub-workflow execution
+type SubDAGProcessor struct{}
+
+func (p *SubDAGProcessor) Process(ctx context.Context, input ProcessingContext) (*ProcessingResult, error) {
+	config := input.Node.Config
+
+	subWorkflowID := config.SubWorkflowID
+	if subWorkflowID == "" {
+		return &ProcessingResult{
+			Success: false,
+			Error:   "sub_workflow_id not specified",
+		}, nil
+	}
+
+	// Apply input mapping
+	subInput := make(map[string]interface{})
+	for subKey, sourceKey := range config.InputMapping {
+		if value, exists := input.Data[sourceKey]; exists {
+			subInput[subKey] = value
+		}
+	}
+
+	// Simulate sub-workflow execution (in real implementation, this would trigger actual sub-workflow)
+	time.Sleep(100 * time.Millisecond)
+
+	// Mock sub-workflow output
+	subOutput := map[string]interface{}{
+		"sub_workflow_result": "completed",
+		"sub_workflow_id":     subWorkflowID,
+		"processed_data":      subInput,
+	}
+
+	// Apply output mapping
+	result := make(map[string]interface{})
+	for targetKey, subKey := range config.OutputMapping {
+		if value, exists := subOutput[subKey]; exists {
+			result[targetKey] = value
+		}
+	}
+
+	// If no output mapping specified, return all sub-workflow output
+	if len(config.OutputMapping) == 0 {
+		result = subOutput
+	}
+
+	return &ProcessingResult{
+		Success: true,
+		Data:    result,
+		Message: fmt.Sprintf("Sub-workflow %s completed successfully", subWorkflowID),
+	}, nil
+}
+
+// HTMLProcessor handles HTML page generation
+type HTMLProcessor struct{}
+
+func (p *HTMLProcessor) Process(ctx context.Context, input ProcessingContext) (*ProcessingResult, error) {
+	config := input.Node.Config
+
+	templateStr := config.Template
+	if templateStr == "" {
+		return &ProcessingResult{
+			Success: false,
+			Error:   "template not specified",
+		}, nil
+	}
+
+	// Parse template
+	tmpl, err := template.New("html_page").Parse(templateStr)
+	if err != nil {
+		return &ProcessingResult{
+			Success: false,
+			Error:   fmt.Sprintf("failed to parse template: %v", err),
+		}, nil
+	}
+
+	// Prepare template data
+	templateData := make(map[string]interface{})
+
+	// Add data from input
+	for key, value := range input.Data {
+		templateData[key] = value
+	}
+
+	// Add template-specific data from config
+	for key, value := range config.TemplateData {
+		templateData[key] = value
+	}
+
+	// Add current timestamp
+	templateData["timestamp"] = time.Now().Format("2006-01-02 15:04:05")
+
+	// Execute template
+	var htmlBuffer strings.Builder
+	if err := tmpl.Execute(&htmlBuffer, templateData); err != nil {
+		return &ProcessingResult{
+			Success: false,
+			Error:   fmt.Sprintf("failed to execute template: %v", err),
+		}, nil
+	}
+
+	html := htmlBuffer.String()
+
+	result := map[string]interface{}{
+		"html_content": html,
+		"template":     templateStr,
+		"data_used":    templateData,
+	}
+
+	// If output path is specified, simulate file writing
+	if config.OutputPath != "" {
+		result["output_path"] = config.OutputPath
+		result["file_written"] = true
+	}
+
+	return &ProcessingResult{
+		Success: true,
+		Data:    result,
+		Message: "HTML page generated successfully",
+	}, nil
+}
+
+// SMSProcessor handles SMS operations
+type SMSProcessor struct{}
+
+func (p *SMSProcessor) Process(ctx context.Context, input ProcessingContext) (*ProcessingResult, error) {
+	config := input.Node.Config
+
+	provider := config.Provider
+	if provider == "" {
+		provider = "default"
+	}
+
+	from := config.From
+	if from == "" {
+		return &ProcessingResult{
+			Success: false,
+			Error:   "from number not specified",
+		}, nil
+	}
+
+	if len(config.SMSTo) == 0 {
+		return &ProcessingResult{
+			Success: false,
+			Error:   "recipient numbers not specified",
+		}, nil
+	}
+
+	message := config.Message
+	if message == "" {
+		return &ProcessingResult{
+			Success: false,
+			Error:   "message not specified",
+		}, nil
+	}
+
+	// Process message template with input data
+	processedMessage := p.processMessageTemplate(message, input.Data)
+
+	// Validate phone numbers
+	validRecipients := []string{}
+	invalidRecipients := []string{}
+
+	for _, recipient := range config.SMSTo {
+		if p.isValidPhoneNumber(recipient) {
+			validRecipients = append(validRecipients, recipient)
+		} else {
+			invalidRecipients = append(invalidRecipients, recipient)
+		}
+	}
+
+	if len(validRecipients) == 0 {
+		return &ProcessingResult{
+			Success: false,
+			Error:   "no valid recipient numbers",
+		}, nil
+	}
+
+	// Simulate SMS sending
+	time.Sleep(50 * time.Millisecond)
+
+	// Mock SMS sending results
+	results := []map[string]interface{}{}
+	for _, recipient := range validRecipients {
+		results = append(results, map[string]interface{}{
+			"recipient":  recipient,
+			"status":     "sent",
+			"message_id": fmt.Sprintf("msg_%d", time.Now().UnixNano()),
+			"provider":   provider,
+		})
+	}
+
+	result := map[string]interface{}{
+		"provider":           provider,
+		"from":               from,
+		"message":            processedMessage,
+		"valid_recipients":   validRecipients,
+		"invalid_recipients": invalidRecipients,
+		"sent_count":         len(validRecipients),
+		"failed_count":       len(invalidRecipients),
+		"results":            results,
+	}
+
+	return &ProcessingResult{
+		Success: true,
+		Data:    result,
+		Message: fmt.Sprintf("SMS sent to %d recipients via %s", len(validRecipients), provider),
+	}, nil
+}
+
+func (p *SMSProcessor) processMessageTemplate(message string, data map[string]interface{}) string {
+	result := message
+	for key, value := range data {
+		placeholder := fmt.Sprintf("{{%s}}", key)
+		result = strings.ReplaceAll(result, placeholder, fmt.Sprintf("%v", value))
+	}
+	return result
+}
+
+func (p *SMSProcessor) isValidPhoneNumber(phone string) bool {
+	// Simple phone number validation (E.164 format)
+	phoneRegex := regexp.MustCompile(`^\+[1-9]\d{1,14}$`)
+	return phoneRegex.MatchString(phone)
+}
+
+// AuthProcessor handles authentication operations
+type AuthProcessor struct{}
+
+func (p *AuthProcessor) Process(ctx context.Context, input ProcessingContext) (*ProcessingResult, error) {
+	config := input.Node.Config
+
+	authType := config.AuthType
+	if authType == "" {
+		authType = "jwt"
+	}
+
+	credentials := config.Credentials
+	if credentials == nil {
+		return &ProcessingResult{
+			Success: false,
+			Error:   "credentials not provided",
+		}, nil
+	}
+
+	switch authType {
+	case "jwt":
+		return p.processJWTAuth(input, credentials, config.TokenExpiry)
+	case "basic":
+		return p.processBasicAuth(input, credentials)
+	case "api_key":
+		return p.processAPIKeyAuth(input, credentials)
+	default:
+		return &ProcessingResult{
+			Success: false,
+			Error:   fmt.Sprintf("unsupported auth type: %s", authType),
+		}, nil
+	}
+}
+
+func (p *AuthProcessor) processJWTAuth(input ProcessingContext, credentials map[string]string, expiry time.Duration) (*ProcessingResult, error) {
+	username, hasUsername := credentials["username"]
+	password, hasPassword := credentials["password"]
+
+	if !hasUsername || !hasPassword {
+		return &ProcessingResult{
+			Success: false,
+			Error:   "username and password required for JWT auth",
+		}, nil
+	}
+
+	// Simulate authentication (in real implementation, verify against user store)
+	if username == "admin" && password == "password" {
+		// Generate mock JWT token
+		token := fmt.Sprintf("jwt.token.%d", time.Now().Unix())
+		expiresAt := time.Now().Add(expiry)
+		if expiry == 0 {
+			expiresAt = time.Now().Add(24 * time.Hour)
+		}
+
+		result := map[string]interface{}{
+			"auth_type":   "jwt",
+			"token":       token,
+			"expires_at":  expiresAt,
+			"username":    username,
+			"permissions": []string{"read", "write", "admin"},
+		}
+
+		return &ProcessingResult{
+			Success: true,
+			Data:    result,
+			Message: "JWT authentication successful",
+		}, nil
+	}
+
+	return &ProcessingResult{
+		Success: false,
+		Error:   "invalid credentials",
+	}, nil
+}
+
+func (p *AuthProcessor) processBasicAuth(input ProcessingContext, credentials map[string]string) (*ProcessingResult, error) {
+	username, hasUsername := credentials["username"]
+	password, hasPassword := credentials["password"]
+
+	if !hasUsername || !hasPassword {
+		return &ProcessingResult{
+			Success: false,
+			Error:   "username and password required for basic auth",
+		}, nil
+	}
+
+	// Simulate basic auth
+	if username != "" && password != "" {
+		result := map[string]interface{}{
+			"auth_type": "basic",
+			"username":  username,
+			"status":    "authenticated",
+		}
+
+		return &ProcessingResult{
+			Success: true,
+			Data:    result,
+			Message: "Basic authentication successful",
+		}, nil
+	}
+
+	return &ProcessingResult{
+		Success: false,
+		Error:   "invalid credentials",
+	}, nil
+}
+
+func (p *AuthProcessor) processAPIKeyAuth(input ProcessingContext, credentials map[string]string) (*ProcessingResult, error) {
+	apiKey, hasAPIKey := credentials["api_key"]
+
+	if !hasAPIKey {
+		return &ProcessingResult{
+			Success: false,
+			Error:   "api_key required for API key auth",
+		}, nil
+	}
+
+	// Simulate API key validation
+	if apiKey != "" && len(apiKey) >= 10 {
+		result := map[string]interface{}{
+			"auth_type": "api_key",
+			"api_key":   apiKey[:6] + "...", // Partially masked
+			"status":    "authenticated",
+		}
+
+		return &ProcessingResult{
+			Success: true,
+			Data:    result,
+			Message: "API key authentication successful",
+		}, nil
+	}
+
+	return &ProcessingResult{
+		Success: false,
+		Error:   "invalid API key",
+	}, nil
+}
+
+// ValidatorProcessor handles data validation
+type ValidatorProcessor struct{}
+
+func (p *ValidatorProcessor) Process(ctx context.Context, input ProcessingContext) (*ProcessingResult, error) {
+	config := input.Node.Config
+
+	validationType := config.ValidationType
+	if validationType == "" {
+		validationType = "rules"
+	}
+
+	validationRules := config.ValidationRules
+	if len(validationRules) == 0 {
+		return &ProcessingResult{
+			Success: false,
+			Error:   "no validation rules specified",
+		}, nil
+	}
+
+	errors := []string{}
+	warnings := []string{}
+	validatedFields := []string{}
+
+	for _, rule := range validationRules {
+		fieldValue, exists := input.Data[rule.Field]
+		if !exists {
+			if rule.Required {
+				errors = append(errors, fmt.Sprintf("required field '%s' is missing", rule.Field))
+			}
+			continue
+		}
+
+		// Validate based on rule type
+		switch rule.Type {
+		case "string":
+			if err := p.validateString(fieldValue, rule); err != nil {
+				errors = append(errors, fmt.Sprintf("field '%s': %s", rule.Field, err.Error()))
+			} else {
+				validatedFields = append(validatedFields, rule.Field)
+			}
+		case "number":
+			if err := p.validateNumber(fieldValue, rule); err != nil {
+				errors = append(errors, fmt.Sprintf("field '%s': %s", rule.Field, err.Error()))
+			} else {
+				validatedFields = append(validatedFields, rule.Field)
+			}
+		case "email":
+			if err := p.validateEmail(fieldValue); err != nil {
+				errors = append(errors, fmt.Sprintf("field '%s': %s", rule.Field, err.Error()))
+			} else {
+				validatedFields = append(validatedFields, rule.Field)
+			}
+		case "regex":
+			if err := p.validateRegex(fieldValue, rule.Pattern); err != nil {
+				errors = append(errors, fmt.Sprintf("field '%s': %s", rule.Field, err.Error()))
+			} else {
+				validatedFields = append(validatedFields, rule.Field)
+			}
+		default:
+			warnings = append(warnings, fmt.Sprintf("unknown validation type '%s' for field '%s'", rule.Type, rule.Field))
+		}
+	}
+
+	success := len(errors) == 0
+	result := map[string]interface{}{
+		"validation_type":  validationType,
+		"validated_fields": validatedFields,
+		"errors":           errors,
+		"warnings":         warnings,
+		"error_count":      len(errors),
+		"warning_count":    len(warnings),
+		"is_valid":         success,
+	}
+
+	message := fmt.Sprintf("Validation completed: %d fields validated, %d errors, %d warnings",
+		len(validatedFields), len(errors), len(warnings))
+
+	return &ProcessingResult{
+		Success: success,
+		Data:    result,
+		Message: message,
+	}, nil
+}
+
+func (p *ValidatorProcessor) validateString(value interface{}, rule ValidationRule) error {
+	str, ok := value.(string)
+	if !ok {
+		return fmt.Errorf("expected string, got %T", value)
+	}
+
+	if rule.MinLength > 0 && len(str) < int(rule.MinLength) {
+		return fmt.Errorf("minimum length is %d, got %d", rule.MinLength, len(str))
+	}
+
+	if rule.MaxLength > 0 && len(str) > int(rule.MaxLength) {
+		return fmt.Errorf("maximum length is %d, got %d", rule.MaxLength, len(str))
+	}
+
+	return nil
+}
+
+func (p *ValidatorProcessor) validateNumber(value interface{}, rule ValidationRule) error {
+	var num float64
+	switch v := value.(type) {
+	case int:
+		num = float64(v)
+	case int64:
+		num = float64(v)
+	case float64:
+		num = v
+	case string:
+		parsed, err := strconv.ParseFloat(v, 64)
+		if err != nil {
+			return fmt.Errorf("cannot parse as number: %s", v)
+		}
+		num = parsed
+	default:
+		return fmt.Errorf("expected number, got %T", value)
+	}
+
+	if rule.Min != nil && num < *rule.Min {
+		return fmt.Errorf("minimum value is %f, got %f", *rule.Min, num)
+	}
+
+	if rule.Max != nil && num > *rule.Max {
+		return fmt.Errorf("maximum value is %f, got %f", *rule.Max, num)
+	}
+
+	return nil
+}
+
+func (p *ValidatorProcessor) validateEmail(value interface{}) error {
+	email, ok := value.(string)
+	if !ok {
+		return fmt.Errorf("expected string, got %T", value)
+	}
+
+	emailRegex := regexp.MustCompile(`^[a-zA-Z0-9._%+\-]+@[a-zA-Z0-9.\-]+\.[a-zA-Z]{2,}$`)
+	if !emailRegex.MatchString(email) {
+		return fmt.Errorf("invalid email format")
+	}
+
+	return nil
+}
+
+func (p *ValidatorProcessor) validateRegex(value interface{}, pattern string) error {
+	str, ok := value.(string)
+	if !ok {
+		return fmt.Errorf("expected string, got %T", value)
+	}
+
+	regex, err := regexp.Compile(pattern)
+	if err != nil {
+		return fmt.Errorf("invalid regex pattern: %s", err.Error())
+	}
+
+	if !regex.MatchString(str) {
+		return fmt.Errorf("does not match pattern %s", pattern)
+	}
+
+	return nil
+}
+
+// RouterProcessor handles conditional routing
+type RouterProcessor struct{}
+
+func (p *RouterProcessor) Process(ctx context.Context, input ProcessingContext) (*ProcessingResult, error) {
+	config := input.Node.Config
+
+	routingRules := config.RoutingRules
+	if len(routingRules) == 0 {
+		return &ProcessingResult{
+			Success: false,
+			Error:   "no routing rules specified",
+		}, nil
+	}
+
+	selectedRoutes := []RoutingRule{}
+
+	for _, rule := range routingRules {
+		if p.evaluateRoutingCondition(rule.Condition, input.Data) {
+			selectedRoutes = append(selectedRoutes, rule)
+		}
+	}
+
+	if len(selectedRoutes) == 0 {
+		// Check if there's a default route
+		for _, rule := range routingRules {
+			if rule.IsDefault {
+				selectedRoutes = append(selectedRoutes, rule)
+				break
+			}
+		}
+	}
+
+	result := map[string]interface{}{
+		"selected_routes": selectedRoutes,
+		"route_count":     len(selectedRoutes),
+		"routing_data":    input.Data,
+	}
+
+	if len(selectedRoutes) == 0 {
+		return &ProcessingResult{
+			Success: false,
+			Data:    result,
+			Error:   "no matching routes found",
+		}, nil
+	}
+
+	message := fmt.Sprintf("Routing completed: %d routes selected", len(selectedRoutes))
+
+	return &ProcessingResult{
+		Success: true,
+		Data:    result,
+		Message: message,
+	}, nil
+}
+
+func (p *RouterProcessor) evaluateRoutingCondition(condition string, data map[string]interface{}) bool {
+	// Simple condition evaluation - in real implementation, use expression parser
+	if condition == "" {
+		return false
+	}
+
+	// Support simple equality checks
+	if strings.Contains(condition, "==") {
+		parts := strings.Split(condition, "==")
+		if len(parts) == 2 {
+			field := strings.TrimSpace(parts[0])
+			expectedValue := strings.TrimSpace(strings.Trim(parts[1], "\"'"))
+
+			if value, exists := data[field]; exists {
+				return fmt.Sprintf("%v", value) == expectedValue
+			}
+		}
+	}
+
+	// Support simple greater than checks
+	if strings.Contains(condition, ">") {
+		parts := strings.Split(condition, ">")
+		if len(parts) == 2 {
+			field := strings.TrimSpace(parts[0])
+			threshold := strings.TrimSpace(parts[1])
+
+			if value, exists := data[field]; exists {
+				if numValue, ok := value.(float64); ok {
+					if thresholdValue, err := strconv.ParseFloat(threshold, 64); err == nil {
+						return numValue > thresholdValue
+					}
+				}
+			}
+		}
+	}
+
+	return false
+}
+
+// StorageProcessor handles data storage operations
+type StorageProcessor struct{}
+
+func (p *StorageProcessor) Process(ctx context.Context, input ProcessingContext) (*ProcessingResult, error) {
+	config := input.Node.Config
+
+	storageType := config.StorageType
+	if storageType == "" {
+		storageType = "memory"
+	}
+
+	operation := config.StorageOperation
+	if operation == "" {
+		operation = "store"
+	}
+
+	key := config.StorageKey
+	if key == "" {
+		key = fmt.Sprintf("data_%d", time.Now().UnixNano())
+	}
+
+	switch operation {
+	case "store":
+		return p.storeData(storageType, key, input.Data)
+	case "retrieve":
+		return p.retrieveData(storageType, key)
+	case "delete":
+		return p.deleteData(storageType, key)
+	default:
+		return &ProcessingResult{
+			Success: false,
+			Error:   fmt.Sprintf("unsupported storage operation: %s", operation),
+		}, nil
+	}
+}
+
+func (p *StorageProcessor) storeData(storageType, key string, data map[string]interface{}) (*ProcessingResult, error) {
+	// Simulate data storage
+	time.Sleep(10 * time.Millisecond)
+
+	result := map[string]interface{}{
+		"storage_type": storageType,
+		"operation":    "store",
+		"key":          key,
+		"stored_data":  data,
+		"timestamp":    time.Now(),
+		"size_bytes":   len(fmt.Sprintf("%v", data)),
+	}
+
+	return &ProcessingResult{
+		Success: true,
+		Data:    result,
+		Message: fmt.Sprintf("Data stored successfully with key: %s", key),
+	}, nil
+}
+
+func (p *StorageProcessor) retrieveData(storageType, key string) (*ProcessingResult, error) {
+	// Simulate data retrieval
+	time.Sleep(5 * time.Millisecond)
+
+	// Mock retrieved data
+	retrievedData := map[string]interface{}{
+		"key":       key,
+		"value":     "mock_stored_value",
+		"timestamp": time.Now().Add(-1 * time.Hour),
+	}
+
+	result := map[string]interface{}{
+		"storage_type":   storageType,
+		"operation":      "retrieve",
+		"key":            key,
+		"retrieved_data": retrievedData,
+		"found":          true,
+	}
+
+	return &ProcessingResult{
+		Success: true,
+		Data:    result,
+		Message: fmt.Sprintf("Data retrieved successfully for key: %s", key),
+	}, nil
+}
+
+func (p *StorageProcessor) deleteData(storageType, key string) (*ProcessingResult, error) {
+	// Simulate data deletion
+	time.Sleep(5 * time.Millisecond)
+
+	result := map[string]interface{}{
+		"storage_type": storageType,
+		"operation":    "delete",
+		"key":          key,
+		"deleted":      true,
+		"timestamp":    time.Now(),
+	}
+
+	return &ProcessingResult{
+		Success: true,
+		Data:    result,
+		Message: fmt.Sprintf("Data deleted successfully for key: %s", key),
+	}, nil
+}
+
+// NotifyProcessor handles notification operations
+type NotifyProcessor struct{}
+
+func (p *NotifyProcessor) Process(ctx context.Context, input ProcessingContext) (*ProcessingResult, error) {
+	config := input.Node.Config
+
+	notificationType := config.NotificationType
+	if notificationType == "" {
+		notificationType = "email"
+	}
+
+	recipients := config.NotificationRecipients
+	if len(recipients) == 0 {
+		return &ProcessingResult{
+			Success: false,
+			Error:   "no notification recipients specified",
+		}, nil
+	}
+
+	message := config.NotificationMessage
+	if message == "" {
+		message = "Workflow notification"
+	}
+
+	// Process message template with input data
+	processedMessage := p.processNotificationTemplate(message, input.Data)
+
+	switch notificationType {
+	case "email":
+		return p.sendEmailNotification(recipients, processedMessage, config)
+	case "sms":
+		return p.sendSMSNotification(recipients, processedMessage, config)
+	case "webhook":
+		return p.sendWebhookNotification(recipients, processedMessage, input.Data, config)
+	default:
+		return &ProcessingResult{
+			Success: false,
+			Error:   fmt.Sprintf("unsupported notification type: %s", notificationType),
+		}, nil
+	}
+}
+
+func (p *NotifyProcessor) processNotificationTemplate(message string, data map[string]interface{}) string {
+	result := message
+	for key, value := range data {
+		placeholder := fmt.Sprintf("{{%s}}", key)
+		result = strings.ReplaceAll(result, placeholder, fmt.Sprintf("%v", value))
+	}
+	return result
+}
+
+func (p *NotifyProcessor) sendEmailNotification(recipients []string, message string, config NodeConfig) (*ProcessingResult, error) {
+	// Simulate email sending
+	time.Sleep(100 * time.Millisecond)
+
+	results := []map[string]interface{}{}
+	for _, recipient := range recipients {
+		results = append(results, map[string]interface{}{
+			"recipient": recipient,
+			"status":    "sent",
+			"type":      "email",
+			"timestamp": time.Now(),
+		})
+	}
+
+	result := map[string]interface{}{
+		"notification_type": "email",
+		"recipients":        recipients,
+		"message":           message,
+		"sent_count":        len(recipients),
+		"results":           results,
+	}
+
+	return &ProcessingResult{
+		Success: true,
+		Data:    result,
+		Message: fmt.Sprintf("Email notifications sent to %d recipients", len(recipients)),
+	}, nil
+}
+
+func (p *NotifyProcessor) sendSMSNotification(recipients []string, message string, config NodeConfig) (*ProcessingResult, error) {
+	// Simulate SMS sending
+	time.Sleep(50 * time.Millisecond)
+
+	results := []map[string]interface{}{}
+	for _, recipient := range recipients {
+		results = append(results, map[string]interface{}{
+			"recipient": recipient,
+			"status":    "sent",
+			"type":      "sms",
+			"timestamp": time.Now(),
+		})
+	}
+
+	result := map[string]interface{}{
+		"notification_type": "sms",
+		"recipients":        recipients,
+		"message":           message,
+		"sent_count":        len(recipients),
+		"results":           results,
+	}
+
+	return &ProcessingResult{
+		Success: true,
+		Data:    result,
+		Message: fmt.Sprintf("SMS notifications sent to %d recipients", len(recipients)),
+	}, nil
+}
+
+func (p *NotifyProcessor) sendWebhookNotification(recipients []string, message string, data map[string]interface{}, config NodeConfig) (*ProcessingResult, error) {
+	// Simulate webhook sending
+	time.Sleep(25 * time.Millisecond)
+
+	results := []map[string]interface{}{}
+	for _, recipient := range recipients {
+		// Mock webhook response
+		results = append(results, map[string]interface{}{
+			"url":       recipient,
+			"status":    "sent",
+			"type":      "webhook",
+			"response":  map[string]interface{}{"status": "ok", "code": 200},
+			"timestamp": time.Now(),
+		})
+	}
+
+	result := map[string]interface{}{
+		"notification_type": "webhook",
+		"urls":              recipients,
+		"message":           message,
+		"payload":           data,
+		"sent_count":        len(recipients),
+		"results":           results,
+	}
+
+	return &ProcessingResult{
+		Success: true,
+		Data:    result,
+		Message: fmt.Sprintf("Webhook notifications sent to %d URLs", len(recipients)),
+	}, nil
+}
+
+// WebhookReceiverProcessor handles incoming webhook processing
+type WebhookReceiverProcessor struct{}
+
+func (p *WebhookReceiverProcessor) Process(ctx context.Context, input ProcessingContext) (*ProcessingResult, error) {
+	config := input.Node.Config
+
+	expectedSignature := config.WebhookSignature
+	secret := config.WebhookSecret
+
+	// Extract webhook data from input
+	webhookData, ok := input.Data["webhook_data"].(map[string]interface{})
+	if !ok {
+		return &ProcessingResult{
+			Success: false,
+			Error:   "no webhook data found in input",
+		}, nil
+	}
+
+	// Verify webhook signature if provided
+	if expectedSignature != "" && secret != "" {
+		isValid := p.verifyWebhookSignature(webhookData, secret, expectedSignature)
+		if !isValid {
+			return &ProcessingResult{
+				Success: false,
+				Error:   "webhook signature verification failed",
+			}, nil
+		}
+	}
+
+	// Process webhook data based on source
+	source, _ := webhookData["source"].(string)
+	if source == "" {
+		source = "unknown"
+	}
+
+	processedData := map[string]interface{}{
+		"source":          source,
+		"original_data":   webhookData,
+		"processed_at":    time.Now(),
+		"signature_valid": expectedSignature == "" || secret == "",
+	}
+
+	// Apply any data transformations specified in config
+	if transformRules, exists := config.WebhookTransforms["transforms"]; exists {
+		if rules, ok := transformRules.(map[string]interface{}); ok {
+			for key, rule := range rules {
+				if sourceField, ok := rule.(string); ok {
+					if value, exists := webhookData[sourceField]; exists {
+						processedData[key] = value
+					}
+				}
+			}
+		}
+	}
+
+	result := map[string]interface{}{
+		"webhook_source":   source,
+		"processed_data":   processedData,
+		"original_payload": webhookData,
+		"processing_time":  time.Now(),
+	}
+
+	return &ProcessingResult{
+		Success: true,
+		Data:    result,
+		Message: fmt.Sprintf("Webhook from %s processed successfully", source),
+	}, nil
+}
+
+func (p *WebhookReceiverProcessor) verifyWebhookSignature(data map[string]interface{}, secret, expectedSignature string) bool {
+	// Convert data to JSON for signature verification
+	payload, err := json.Marshal(data)
+	if err != nil {
+		return false
+	}
+
+	// Create HMAC signature
+	h := hmac.New(sha256.New, []byte(secret))
+	h.Write(payload)
+	computedSignature := hex.EncodeToString(h.Sum(nil))
+
+	// Compare signatures (constant time comparison for security)
+	return hmac.Equal([]byte(computedSignature), []byte(expectedSignature))
+}

workflow/api.go

@@ -0,0 +1,436 @@
+package workflow
+
+import (
+	"strconv"
+	"time"
+
+	"github.com/gofiber/fiber/v2"
+	"github.com/google/uuid"
+)
+
+// WorkflowAPI provides HTTP handlers for workflow management
+type WorkflowAPI struct {
+	engine *WorkflowEngine
+}
+
+// NewWorkflowAPI creates a new workflow API handler
+func NewWorkflowAPI(engine *WorkflowEngine) *WorkflowAPI {
+	return &WorkflowAPI{
+		engine: engine,
+	}
+}
+
+// RegisterRoutes registers all workflow routes with Fiber app
+func (api *WorkflowAPI) RegisterRoutes(app *fiber.App) {
+	v1 := app.Group("/api/v1/workflows")
+
+	// Workflow definition routes
+	v1.Post("/", api.CreateWorkflow)
+	v1.Get("/", api.ListWorkflows)
+	v1.Get("/:id", api.GetWorkflow)
+	v1.Put("/:id", api.UpdateWorkflow)
+	v1.Delete("/:id", api.DeleteWorkflow)
+	v1.Get("/:id/versions", api.GetWorkflowVersions)
+
+	// Execution routes
+	v1.Post("/:id/execute", api.ExecuteWorkflow)
+	v1.Get("/:id/executions", api.ListWorkflowExecutions)
+	v1.Get("/executions", api.ListAllExecutions)
+	v1.Get("/executions/:executionId", api.GetExecution)
+	v1.Post("/executions/:executionId/cancel", api.CancelExecution)
+	v1.Post("/executions/:executionId/suspend", api.SuspendExecution)
+	v1.Post("/executions/:executionId/resume", api.ResumeExecution)
+
+	// Management routes
+	v1.Get("/health", api.HealthCheck)
+	v1.Get("/metrics", api.GetMetrics)
+}
+
+// CreateWorkflow creates a new workflow definition
+func (api *WorkflowAPI) CreateWorkflow(c *fiber.Ctx) error {
+	var definition WorkflowDefinition
+	if err := c.BodyParser(&definition); err != nil {
+		return c.Status(fiber.StatusBadRequest).JSON(fiber.Map{
+			"error": "Invalid request body",
+		})
+	}
+
+	// Set ID if not provided
+	if definition.ID == "" {
+		definition.ID = uuid.New().String()
+	}
+
+	// Set version if not provided
+	if definition.Version == "" {
+		definition.Version = "1.0.0"
+	}
+
+	if err := api.engine.RegisterWorkflow(c.Context(), &definition); err != nil {
+		return c.Status(fiber.StatusBadRequest).JSON(fiber.Map{
+			"error": err.Error(),
+		})
+	}
+
+	return c.Status(fiber.StatusCreated).JSON(definition)
+}
+
+// ListWorkflows lists workflow definitions with filtering
+func (api *WorkflowAPI) ListWorkflows(c *fiber.Ctx) error {
+	filter := &WorkflowFilter{
+		Limit:  10,
+		Offset: 0,
+	}
+
+	// Parse query parameters
+	if limit := c.Query("limit"); limit != "" {
+		if l, err := strconv.Atoi(limit); err == nil {
+			filter.Limit = l
+		}
+	}
+
+	if offset := c.Query("offset"); offset != "" {
+		if o, err := strconv.Atoi(offset); err == nil {
+			filter.Offset = o
+		}
+	}
+
+	if status := c.Query("status"); status != "" {
+		filter.Status = []WorkflowStatus{WorkflowStatus(status)}
+	}
+
+	if category := c.Query("category"); category != "" {
+		filter.Category = []string{category}
+	}
+
+	if owner := c.Query("owner"); owner != "" {
+		filter.Owner = []string{owner}
+	}
+
+	if search := c.Query("search"); search != "" {
+		filter.Search = search
+	}
+
+	if sortBy := c.Query("sort_by"); sortBy != "" {
+		filter.SortBy = sortBy
+	}
+
+	if sortOrder := c.Query("sort_order"); sortOrder != "" {
+		filter.SortOrder = sortOrder
+	}
+
+	workflows, err := api.engine.ListWorkflows(c.Context(), filter)
+	if err != nil {
+		return c.Status(fiber.StatusInternalServerError).JSON(fiber.Map{
+			"error": err.Error(),
+		})
+	}
+
+	return c.JSON(fiber.Map{
+		"workflows": workflows,
+		"total":     len(workflows),
+		"limit":     filter.Limit,
+		"offset":    filter.Offset,
+	})
+}
+
+// GetWorkflow retrieves a specific workflow definition
+func (api *WorkflowAPI) GetWorkflow(c *fiber.Ctx) error {
+	id := c.Params("id")
+	version := c.Query("version")
+
+	workflow, err := api.engine.GetWorkflow(c.Context(), id, version)
+	if err != nil {
+		return c.Status(fiber.StatusNotFound).JSON(fiber.Map{
+			"error": err.Error(),
+		})
+	}
+
+	return c.JSON(workflow)
+}
+
+// UpdateWorkflow updates an existing workflow definition
+func (api *WorkflowAPI) UpdateWorkflow(c *fiber.Ctx) error {
+	id := c.Params("id")
+
+	var definition WorkflowDefinition
+	if err := c.BodyParser(&definition); err != nil {
+		return c.Status(fiber.StatusBadRequest).JSON(fiber.Map{
+			"error": "Invalid request body",
+		})
+	}
+
+	// Ensure ID matches
+	definition.ID = id
+
+	if err := api.engine.RegisterWorkflow(c.Context(), &definition); err != nil {
+		return c.Status(fiber.StatusBadRequest).JSON(fiber.Map{
+			"error": err.Error(),
+		})
+	}
+
+	return c.JSON(definition)
+}
+
+// DeleteWorkflow removes a workflow definition
+func (api *WorkflowAPI) DeleteWorkflow(c *fiber.Ctx) error {
+	id := c.Params("id")
+
+	if err := api.engine.DeleteWorkflow(c.Context(), id); err != nil {
+		return c.Status(fiber.StatusNotFound).JSON(fiber.Map{
+			"error": err.Error(),
+		})
+	}
+
+	return c.Status(fiber.StatusNoContent).Send(nil)
+}
+
+// GetWorkflowVersions retrieves all versions of a workflow
+func (api *WorkflowAPI) GetWorkflowVersions(c *fiber.Ctx) error {
+	id := c.Params("id")
+
+	versions, err := api.engine.registry.GetVersions(c.Context(), id)
+	if err != nil {
+		return c.Status(fiber.StatusNotFound).JSON(fiber.Map{
+			"error": err.Error(),
+		})
+	}
+
+	return c.JSON(fiber.Map{
+		"workflow_id": id,
+		"versions":    versions,
+	})
+}
+
+// ExecuteWorkflow starts workflow execution
+func (api *WorkflowAPI) ExecuteWorkflow(c *fiber.Ctx) error {
+	id := c.Params("id")
+
+	var request struct {
+		Input           map[string]interface{} `json:"input"`
+		Priority        Priority               `json:"priority"`
+		Owner           string                 `json:"owner"`
+		TriggeredBy     string                 `json:"triggered_by"`
+		ParentExecution string                 `json:"parent_execution"`
+		Delay           int                    `json:"delay"` // seconds
+	}
+
+	if err := c.BodyParser(&request); err != nil {
+		return c.Status(fiber.StatusBadRequest).JSON(fiber.Map{
+			"error": "Invalid request body",
+		})
+	}
+
+	options := &ExecutionOptions{
+		Priority:        request.Priority,
+		Owner:           request.Owner,
+		TriggeredBy:     request.TriggeredBy,
+		ParentExecution: request.ParentExecution,
+		Delay:           time.Duration(request.Delay) * time.Second,
+	}
+
+	execution, err := api.engine.ExecuteWorkflow(c.Context(), id, request.Input, options)
+	if err != nil {
+		return c.Status(fiber.StatusBadRequest).JSON(fiber.Map{
+			"error": err.Error(),
+		})
+	}
+
+	return c.Status(fiber.StatusCreated).JSON(execution)
+}
+
+// ListWorkflowExecutions lists executions for a specific workflow
+func (api *WorkflowAPI) ListWorkflowExecutions(c *fiber.Ctx) error {
+	workflowID := c.Params("id")
+
+	filter := &ExecutionFilter{
+		WorkflowID: []string{workflowID},
+		Limit:      10,
+		Offset:     0,
+	}
+
+	// Parse query parameters
+	if limit := c.Query("limit"); limit != "" {
+		if l, err := strconv.Atoi(limit); err == nil {
+			filter.Limit = l
+		}
+	}
+
+	if offset := c.Query("offset"); offset != "" {
+		if o, err := strconv.Atoi(offset); err == nil {
+			filter.Offset = o
+		}
+	}
+
+	if status := c.Query("status"); status != "" {
+		filter.Status = []ExecutionStatus{ExecutionStatus(status)}
+	}
+
+	executions, err := api.engine.ListExecutions(c.Context(), filter)
+	if err != nil {
+		return c.Status(fiber.StatusInternalServerError).JSON(fiber.Map{
+			"error": err.Error(),
+		})
+	}
+
+	return c.JSON(fiber.Map{
+		"executions": executions,
+		"total":      len(executions),
+		"limit":      filter.Limit,
+		"offset":     filter.Offset,
+	})
+}
+
+// ListAllExecutions lists all executions with filtering
+func (api *WorkflowAPI) ListAllExecutions(c *fiber.Ctx) error {
+	filter := &ExecutionFilter{
+		Limit:  10,
+		Offset: 0,
+	}
+
+	// Parse query parameters
+	if limit := c.Query("limit"); limit != "" {
+		if l, err := strconv.Atoi(limit); err == nil {
+			filter.Limit = l
+		}
+	}
+
+	if offset := c.Query("offset"); offset != "" {
+		if o, err := strconv.Atoi(offset); err == nil {
+			filter.Offset = o
+		}
+	}
+
+	if status := c.Query("status"); status != "" {
+		filter.Status = []ExecutionStatus{ExecutionStatus(status)}
+	}
+
+	if owner := c.Query("owner"); owner != "" {
+		filter.Owner = []string{owner}
+	}
+
+	if priority := c.Query("priority"); priority != "" {
+		filter.Priority = []Priority{Priority(priority)}
+	}
+
+	executions, err := api.engine.ListExecutions(c.Context(), filter)
+	if err != nil {
+		return c.Status(fiber.StatusInternalServerError).JSON(fiber.Map{
+			"error": err.Error(),
+		})
+	}
+
+	return c.JSON(fiber.Map{
+		"executions": executions,
+		"total":      len(executions),
+		"limit":      filter.Limit,
+		"offset":     filter.Offset,
+	})
+}
+
+// GetExecution retrieves a specific execution
+func (api *WorkflowAPI) GetExecution(c *fiber.Ctx) error {
+	executionID := c.Params("executionId")
+
+	execution, err := api.engine.GetExecution(c.Context(), executionID)
+	if err != nil {
+		return c.Status(fiber.StatusNotFound).JSON(fiber.Map{
+			"error": err.Error(),
+		})
+	}
+
+	return c.JSON(execution)
+}
+
+// CancelExecution cancels a running execution
+func (api *WorkflowAPI) CancelExecution(c *fiber.Ctx) error {
+	executionID := c.Params("executionId")
+
+	if err := api.engine.CancelExecution(c.Context(), executionID); err != nil {
+		return c.Status(fiber.StatusBadRequest).JSON(fiber.Map{
+			"error": err.Error(),
+		})
+	}
+
+	return c.Status(fiber.StatusOK).JSON(fiber.Map{
+		"message": "Execution cancelled",
+	})
+}
+
+// SuspendExecution suspends a running execution
+func (api *WorkflowAPI) SuspendExecution(c *fiber.Ctx) error {
+	executionID := c.Params("executionId")
+
+	if err := api.engine.SuspendExecution(c.Context(), executionID); err != nil {
+		return c.Status(fiber.StatusBadRequest).JSON(fiber.Map{
+			"error": err.Error(),
+		})
+	}
+
+	return c.Status(fiber.StatusOK).JSON(fiber.Map{
+		"message": "Execution suspended",
+	})
+}
+
+// ResumeExecution resumes a suspended execution
+func (api *WorkflowAPI) ResumeExecution(c *fiber.Ctx) error {
+	executionID := c.Params("executionId")
+
+	if err := api.engine.ResumeExecution(c.Context(), executionID); err != nil {
+		return c.Status(fiber.StatusBadRequest).JSON(fiber.Map{
+			"error": err.Error(),
+		})
+	}
+
+	return c.Status(fiber.StatusOK).JSON(fiber.Map{
+		"message": "Execution resumed",
+	})
+}
+
+// HealthCheck returns the health status of the workflow engine
+func (api *WorkflowAPI) HealthCheck(c *fiber.Ctx) error {
+	return c.JSON(fiber.Map{
+		"status":    "healthy",
+		"timestamp": time.Now(),
+		"version":   "1.0.0",
+	})
+}
+
+// GetMetrics returns workflow engine metrics
+func (api *WorkflowAPI) GetMetrics(c *fiber.Ctx) error {
+	// In a real implementation, collect actual metrics
+	metrics := map[string]interface{}{
+		"total_workflows":        0,
+		"total_executions":       0,
+		"running_executions":     0,
+		"completed_executions":   0,
+		"failed_executions":      0,
+		"average_execution_time": "0s",
+		"uptime":                 "0s",
+		"memory_usage":           "0MB",
+		"cpu_usage":              "0%",
+	}
+
+	return c.JSON(metrics)
+}
+
+// Error handling middleware
+func ErrorHandler(c *fiber.Ctx, err error) error {
+	code := fiber.StatusInternalServerError
+
+	if e, ok := err.(*fiber.Error); ok {
+		code = e.Code
+	}
+
+	return c.Status(code).JSON(fiber.Map{
+		"error":     true,
+		"message":   err.Error(),
+		"timestamp": time.Now(),
+	})
+}
+
+// CORS middleware configuration
+func CORSConfig() fiber.Config {
+	return fiber.Config{
+		ErrorHandler: ErrorHandler,
+	}
+}

workflow/demo/main.go

@@ -0,0 +1,718 @@
+package main
+
+import (
+	"context"
+	"fmt"
+	"log"
+	"time"
+
+	"github.com/gofiber/fiber/v2"
+	"github.com/gofiber/fiber/v2/middleware/cors"
+	"github.com/gofiber/fiber/v2/middleware/logger"
+	"github.com/gofiber/fiber/v2/middleware/recover"
+
+	"github.com/oarkflow/mq/workflow"
+)
+
+func main() {
+	fmt.Println("🚀 Starting Complete Workflow Engine Demo...")
+
+	// Create workflow engine with configuration
+	config := &workflow.Config{
+		MaxWorkers:       10,
+		ExecutionTimeout: 30 * time.Minute,
+		EnableMetrics:    true,
+		EnableAudit:      true,
+		EnableTracing:    true,
+		LogLevel:         "info",
+		Storage: workflow.StorageConfig{
+			Type:           "memory",
+			MaxConnections: 100,
+		},
+		Security: workflow.SecurityConfig{
+			EnableAuth:     false,
+			AllowedOrigins: []string{"*"},
+		},
+	}
+
+	engine := workflow.NewWorkflowEngine(config)
+
+	// Start the engine
+	ctx := context.Background()
+	if err := engine.Start(ctx); err != nil {
+		log.Fatalf("Failed to start workflow engine: %v", err)
+	}
+	defer engine.Stop(ctx)
+
+	// Create and register sample workflows
+	createSampleWorkflows(ctx, engine)
+
+	// Start HTTP server
+	startHTTPServer(engine)
+}
+
+func createSampleWorkflows(ctx context.Context, engine *workflow.WorkflowEngine) {
+	fmt.Println("📝 Creating sample workflows...")
+
+	// 1. Simple Data Processing Workflow
+	dataProcessingWorkflow := &workflow.WorkflowDefinition{
+		ID:          "data-processing-workflow",
+		Name:        "Data Processing Pipeline",
+		Description: "A workflow that processes incoming data through validation, transformation, and storage",
+		Version:     "1.0.0",
+		Status:      workflow.WorkflowStatusActive,
+		Category:    "data-processing",
+		Owner:       "demo-user",
+		Tags:        []string{"data", "processing", "pipeline"},
+		Variables: map[string]workflow.Variable{
+			"source_url": {
+				Name:         "source_url",
+				Type:         "string",
+				DefaultValue: "https://api.example.com/data",
+				Required:     true,
+				Description:  "URL to fetch data from",
+			},
+			"batch_size": {
+				Name:         "batch_size",
+				Type:         "integer",
+				DefaultValue: 100,
+				Required:     false,
+				Description:  "Number of records to process in each batch",
+			},
+		},
+		Nodes: []workflow.WorkflowNode{
+			{
+				ID:          "fetch-data",
+				Name:        "Fetch Data",
+				Type:        workflow.NodeTypeAPI,
+				Description: "Fetch data from external API",
+				Config: workflow.NodeConfig{
+					URL:    "${source_url}",
+					Method: "GET",
+					Headers: map[string]string{
+						"Content-Type": "application/json",
+					},
+				},
+				Position: workflow.Position{X: 100, Y: 100},
+				Timeout:  func() *time.Duration { d := 30 * time.Second; return &d }(),
+			},
+			{
+				ID:          "validate-data",
+				Name:        "Validate Data",
+				Type:        workflow.NodeTypeTask,
+				Description: "Validate the fetched data",
+				Config: workflow.NodeConfig{
+					Script: "console.log('Validating data:', ${data})",
+				},
+				Position: workflow.Position{X: 300, Y: 100},
+			},
+			{
+				ID:          "transform-data",
+				Name:        "Transform Data",
+				Type:        workflow.NodeTypeTransform,
+				Description: "Transform data to required format",
+				Config: workflow.NodeConfig{
+					TransformType: "json_path",
+					Expression:    "$.data",
+				},
+				Position: workflow.Position{X: 500, Y: 100},
+			},
+			{
+				ID:          "check-quality",
+				Name:        "Data Quality Check",
+				Type:        workflow.NodeTypeDecision,
+				Description: "Check if data meets quality standards",
+				Config: workflow.NodeConfig{
+					Rules: []workflow.Rule{
+						{
+							Condition: "record_count > 0",
+							Output:    "quality_passed",
+							NextNode:  "store-data",
+						},
+						{
+							Condition: "record_count == 0",
+							Output:    "quality_failed",
+							NextNode:  "notify-failure",
+						},
+					},
+				},
+				Position: workflow.Position{X: 700, Y: 100},
+			},
+			{
+				ID:          "store-data",
+				Name:        "Store Data",
+				Type:        workflow.NodeTypeDatabase,
+				Description: "Store processed data in database",
+				Config: workflow.NodeConfig{
+					Query:      "INSERT INTO processed_data (data, created_at) VALUES (?, ?)",
+					Connection: "default",
+				},
+				Position: workflow.Position{X: 900, Y: 50},
+			},
+			{
+				ID:          "notify-failure",
+				Name:        "Notify Failure",
+				Type:        workflow.NodeTypeEmail,
+				Description: "Send notification about data quality failure",
+				Config: workflow.NodeConfig{
+					To:      []string{"admin@example.com"},
+					Subject: "Data Quality Check Failed",
+					Body:    "The data processing workflow failed quality checks.",
+				},
+				Position: workflow.Position{X: 900, Y: 150},
+			},
+		},
+		Edges: []workflow.WorkflowEdge{
+			{
+				ID:       "fetch-to-validate",
+				FromNode: "fetch-data",
+				ToNode:   "validate-data",
+				Priority: 1,
+			},
+			{
+				ID:       "validate-to-transform",
+				FromNode: "validate-data",
+				ToNode:   "transform-data",
+				Priority: 1,
+			},
+			{
+				ID:       "transform-to-check",
+				FromNode: "transform-data",
+				ToNode:   "check-quality",
+				Priority: 1,
+			},
+			{
+				ID:        "check-to-store",
+				FromNode:  "check-quality",
+				ToNode:    "store-data",
+				Condition: "quality_passed",
+				Priority:  1,
+			},
+			{
+				ID:        "check-to-notify",
+				FromNode:  "check-quality",
+				ToNode:    "notify-failure",
+				Condition: "quality_failed",
+				Priority:  2,
+			},
+		},
+		Config: workflow.WorkflowConfig{
+			Timeout:     func() *time.Duration { d := 10 * time.Minute; return &d }(),
+			MaxRetries:  3,
+			Priority:    workflow.PriorityMedium,
+			Concurrency: 5,
+			ErrorHandling: workflow.ErrorHandling{
+				OnFailure: "stop",
+				MaxErrors: 3,
+				Rollback:  false,
+			},
+		},
+	}
+
+	// 2. Approval Workflow
+	approvalWorkflow := &workflow.WorkflowDefinition{
+		ID:          "approval-workflow",
+		Name:        "Document Approval Process",
+		Description: "Multi-stage approval workflow for document processing",
+		Version:     "1.0.0",
+		Status:      workflow.WorkflowStatusActive,
+		Category:    "approval",
+		Owner:       "demo-user",
+		Tags:        []string{"approval", "documents", "review"},
+		Nodes: []workflow.WorkflowNode{
+			{
+				ID:          "initial-review",
+				Name:        "Initial Review",
+				Type:        workflow.NodeTypeHumanTask,
+				Description: "Initial review by team lead",
+				Config: workflow.NodeConfig{
+					Custom: map[string]interface{}{
+						"assignee":    "team-lead",
+						"due_date":    "3 days",
+						"description": "Please review the document for technical accuracy",
+					},
+				},
+				Position: workflow.Position{X: 100, Y: 100},
+			},
+			{
+				ID:          "check-approval",
+				Name:        "Check Approval Status",
+				Type:        workflow.NodeTypeDecision,
+				Description: "Check if document was approved or rejected",
+				Config: workflow.NodeConfig{
+					Rules: []workflow.Rule{
+						{
+							Condition: "status == 'approved'",
+							Output:    "approved",
+							NextNode:  "manager-review",
+						},
+						{
+							Condition: "status == 'rejected'",
+							Output:    "rejected",
+							NextNode:  "notify-rejection",
+						},
+						{
+							Condition: "status == 'needs_changes'",
+							Output:    "needs_changes",
+							NextNode:  "notify-changes",
+						},
+					},
+				},
+				Position: workflow.Position{X: 300, Y: 100},
+			},
+			{
+				ID:          "manager-review",
+				Name:        "Manager Review",
+				Type:        workflow.NodeTypeHumanTask,
+				Description: "Final approval by manager",
+				Config: workflow.NodeConfig{
+					Custom: map[string]interface{}{
+						"assignee":    "manager",
+						"due_date":    "2 days",
+						"description": "Final approval required",
+					},
+				},
+				Position: workflow.Position{X: 500, Y: 50},
+			},
+			{
+				ID:          "final-approval",
+				Name:        "Final Approval Check",
+				Type:        workflow.NodeTypeDecision,
+				Description: "Check final approval status",
+				Config: workflow.NodeConfig{
+					Rules: []workflow.Rule{
+						{
+							Condition: "status == 'approved'",
+							Output:    "final_approved",
+							NextNode:  "publish-document",
+						},
+						{
+							Condition: "status == 'rejected'",
+							Output:    "final_rejected",
+							NextNode:  "notify-rejection",
+						},
+					},
+				},
+				Position: workflow.Position{X: 700, Y: 50},
+			},
+			{
+				ID:          "publish-document",
+				Name:        "Publish Document",
+				Type:        workflow.NodeTypeTask,
+				Description: "Publish approved document",
+				Config: workflow.NodeConfig{
+					Script: "console.log('Publishing document:', ${document_id})",
+				},
+				Position: workflow.Position{X: 900, Y: 50},
+			},
+			{
+				ID:          "notify-rejection",
+				Name:        "Notify Rejection",
+				Type:        workflow.NodeTypeEmail,
+				Description: "Send rejection notification",
+				Config: workflow.NodeConfig{
+					To:      []string{"${author_email}"},
+					Subject: "Document Rejected",
+					Body:    "Your document has been rejected. Reason: ${rejection_reason}",
+				},
+				Position: workflow.Position{X: 500, Y: 200},
+			},
+			{
+				ID:          "notify-changes",
+				Name:        "Notify Changes Needed",
+				Type:        workflow.NodeTypeEmail,
+				Description: "Send notification about required changes",
+				Config: workflow.NodeConfig{
+					To:      []string{"${author_email}"},
+					Subject: "Document Changes Required",
+					Body:    "Your document needs changes. Details: ${change_details}",
+				},
+				Position: workflow.Position{X: 300, Y: 200},
+			},
+		},
+		Edges: []workflow.WorkflowEdge{
+			{
+				ID:       "review-to-check",
+				FromNode: "initial-review",
+				ToNode:   "check-approval",
+				Priority: 1,
+			},
+			{
+				ID:        "check-to-manager",
+				FromNode:  "check-approval",
+				ToNode:    "manager-review",
+				Condition: "approved",
+				Priority:  1,
+			},
+			{
+				ID:        "check-to-rejection",
+				FromNode:  "check-approval",
+				ToNode:    "notify-rejection",
+				Condition: "rejected",
+				Priority:  2,
+			},
+			{
+				ID:        "check-to-changes",
+				FromNode:  "check-approval",
+				ToNode:    "notify-changes",
+				Condition: "needs_changes",
+				Priority:  3,
+			},
+			{
+				ID:       "manager-to-final",
+				FromNode: "manager-review",
+				ToNode:   "final-approval",
+				Priority: 1,
+			},
+			{
+				ID:        "final-to-publish",
+				FromNode:  "final-approval",
+				ToNode:    "publish-document",
+				Condition: "final_approved",
+				Priority:  1,
+			},
+			{
+				ID:        "final-to-rejection",
+				FromNode:  "final-approval",
+				ToNode:    "notify-rejection",
+				Condition: "final_rejected",
+				Priority:  2,
+			},
+		},
+		Config: workflow.WorkflowConfig{
+			Timeout:     func() *time.Duration { d := 7 * 24 * time.Hour; return &d }(), // 7 days
+			MaxRetries:  1,
+			Priority:    workflow.PriorityHigh,
+			Concurrency: 1,
+			ErrorHandling: workflow.ErrorHandling{
+				OnFailure: "continue",
+				MaxErrors: 5,
+				Rollback:  false,
+			},
+		},
+	}
+
+	// 3. Complex ETL Workflow
+	etlWorkflow := &workflow.WorkflowDefinition{
+		ID:          "etl-workflow",
+		Name:        "ETL Data Pipeline",
+		Description: "Extract, Transform, Load workflow with parallel processing",
+		Version:     "1.0.0",
+		Status:      workflow.WorkflowStatusActive,
+		Category:    "etl",
+		Owner:       "data-team",
+		Tags:        []string{"etl", "data", "parallel", "batch"},
+		Nodes: []workflow.WorkflowNode{
+			{
+				ID:          "extract-customers",
+				Name:        "Extract Customer Data",
+				Type:        workflow.NodeTypeDatabase,
+				Description: "Extract customer data from source database",
+				Config: workflow.NodeConfig{
+					Query:      "SELECT * FROM customers WHERE updated_at > ?",
+					Connection: "source_db",
+				},
+				Position: workflow.Position{X: 100, Y: 50},
+			},
+			{
+				ID:          "extract-orders",
+				Name:        "Extract Order Data",
+				Type:        workflow.NodeTypeDatabase,
+				Description: "Extract order data from source database",
+				Config: workflow.NodeConfig{
+					Query:      "SELECT * FROM orders WHERE created_at > ?",
+					Connection: "source_db",
+				},
+				Position: workflow.Position{X: 100, Y: 150},
+			},
+			{
+				ID:          "transform-customers",
+				Name:        "Transform Customer Data",
+				Type:        workflow.NodeTypeTransform,
+				Description: "Clean and transform customer data",
+				Config: workflow.NodeConfig{
+					TransformType: "expression",
+					Expression:    "standardize_phone(${phone}) AND validate_email(${email})",
+				},
+				Position: workflow.Position{X: 300, Y: 50},
+			},
+			{
+				ID:          "transform-orders",
+				Name:        "Transform Order Data",
+				Type:        workflow.NodeTypeTransform,
+				Description: "Calculate order metrics and clean data",
+				Config: workflow.NodeConfig{
+					TransformType: "expression",
+					Expression:    "calculate_total(${items}) AND format_date(${order_date})",
+				},
+				Position: workflow.Position{X: 300, Y: 150},
+			},
+			{
+				ID:          "parallel-validation",
+				Name:        "Parallel Data Validation",
+				Type:        workflow.NodeTypeParallel,
+				Description: "Run validation checks in parallel",
+				Config: workflow.NodeConfig{
+					Custom: map[string]interface{}{
+						"max_parallel": 5,
+						"timeout":      "30s",
+					},
+				},
+				Position: workflow.Position{X: 500, Y: 100},
+			},
+			{
+				ID:          "merge-data",
+				Name:        "Merge Customer & Order Data",
+				Type:        workflow.NodeTypeTask,
+				Description: "Join customer and order data",
+				Config: workflow.NodeConfig{
+					Script: "merge_datasets(${customers}, ${orders})",
+				},
+				Position: workflow.Position{X: 700, Y: 100},
+			},
+			{
+				ID:          "load-warehouse",
+				Name:        "Load to Data Warehouse",
+				Type:        workflow.NodeTypeDatabase,
+				Description: "Load processed data to warehouse",
+				Config: workflow.NodeConfig{
+					Query:      "INSERT INTO warehouse.customer_orders SELECT * FROM temp_table",
+					Connection: "warehouse_db",
+				},
+				Position: workflow.Position{X: 900, Y: 100},
+			},
+			{
+				ID:          "send-report",
+				Name:        "Send Processing Report",
+				Type:        workflow.NodeTypeEmail,
+				Description: "Send completion report",
+				Config: workflow.NodeConfig{
+					To:      []string{"data-team@example.com"},
+					Subject: "ETL Pipeline Completed",
+					Body:    "ETL pipeline completed successfully. Processed ${record_count} records.",
+				},
+				Position: workflow.Position{X: 1100, Y: 100},
+			},
+		},
+		Edges: []workflow.WorkflowEdge{
+			{
+				ID:       "extract-customers-to-transform",
+				FromNode: "extract-customers",
+				ToNode:   "transform-customers",
+				Priority: 1,
+			},
+			{
+				ID:       "extract-orders-to-transform",
+				FromNode: "extract-orders",
+				ToNode:   "transform-orders",
+				Priority: 1,
+			},
+			{
+				ID:       "customers-to-validation",
+				FromNode: "transform-customers",
+				ToNode:   "parallel-validation",
+				Priority: 1,
+			},
+			{
+				ID:       "orders-to-validation",
+				FromNode: "transform-orders",
+				ToNode:   "parallel-validation",
+				Priority: 1,
+			},
+			{
+				ID:       "validation-to-merge",
+				FromNode: "parallel-validation",
+				ToNode:   "merge-data",
+				Priority: 1,
+			},
+			{
+				ID:       "merge-to-load",
+				FromNode: "merge-data",
+				ToNode:   "load-warehouse",
+				Priority: 1,
+			},
+			{
+				ID:       "load-to-report",
+				FromNode: "load-warehouse",
+				ToNode:   "send-report",
+				Priority: 1,
+			},
+		},
+		Config: workflow.WorkflowConfig{
+			Timeout:     func() *time.Duration { d := 2 * time.Hour; return &d }(),
+			MaxRetries:  2,
+			Priority:    workflow.PriorityCritical,
+			Concurrency: 10,
+			ErrorHandling: workflow.ErrorHandling{
+				OnFailure: "retry",
+				MaxErrors: 3,
+				Rollback:  true,
+			},
+		},
+	}
+
+	// Register all workflows
+	workflows := []*workflow.WorkflowDefinition{
+		dataProcessingWorkflow,
+		approvalWorkflow,
+		etlWorkflow,
+	}
+
+	for _, wf := range workflows {
+		if err := engine.RegisterWorkflow(ctx, wf); err != nil {
+			log.Printf("Failed to register workflow %s: %v", wf.Name, err)
+		} else {
+			fmt.Printf("✅ Registered workflow: %s (ID: %s)\n", wf.Name, wf.ID)
+		}
+	}
+
+	// Execute sample workflows
+	fmt.Println("🏃 Executing sample workflows...")
+
+	// Execute data processing workflow
+	dataExecution, err := engine.ExecuteWorkflow(ctx, "data-processing-workflow", map[string]interface{}{
+		"source_url":   "https://jsonplaceholder.typicode.com/posts",
+		"batch_size":   50,
+		"record_count": 100,
+	}, &workflow.ExecutionOptions{
+		Priority:    workflow.PriorityMedium,
+		Owner:       "demo-user",
+		TriggeredBy: "demo",
+	})
+	if err != nil {
+		log.Printf("Failed to execute data processing workflow: %v", err)
+	} else {
+		fmt.Printf("🚀 Started data processing execution: %s\n", dataExecution.ID)
+	}
+
+	// Execute approval workflow
+	approvalExecution, err := engine.ExecuteWorkflow(ctx, "approval-workflow", map[string]interface{}{
+		"document_id":       "DOC-12345",
+		"author_email":      "author@example.com",
+		"document_title":    "Technical Specification",
+		"document_category": "technical",
+	}, &workflow.ExecutionOptions{
+		Priority:    workflow.PriorityHigh,
+		Owner:       "demo-user",
+		TriggeredBy: "document-system",
+	})
+	if err != nil {
+		log.Printf("Failed to execute approval workflow: %v", err)
+	} else {
+		fmt.Printf("🚀 Started approval execution: %s\n", approvalExecution.ID)
+	}
+
+	// Execute ETL workflow with delay
+	etlExecution, err := engine.ExecuteWorkflow(ctx, "etl-workflow", map[string]interface{}{
+		"start_date": "2023-01-01",
+		"end_date":   "2023-12-31",
+		"table_name": "customer_orders",
+	}, &workflow.ExecutionOptions{
+		Priority:    workflow.PriorityCritical,
+		Owner:       "data-team",
+		TriggeredBy: "scheduler",
+		Delay:       2 * time.Second, // Start after 2 seconds
+	})
+	if err != nil {
+		log.Printf("Failed to execute ETL workflow: %v", err)
+	} else {
+		fmt.Printf("🚀 Scheduled ETL execution: %s (starts in 2 seconds)\n", etlExecution.ID)
+	}
+
+	// Wait a bit to see some execution progress
+	time.Sleep(3 * time.Second)
+
+	// Check execution status
+	fmt.Println("📊 Checking execution status...")
+	if dataExecution != nil {
+		if exec, err := engine.GetExecution(ctx, dataExecution.ID); err == nil {
+			fmt.Printf("Data Processing Status: %s\n", exec.Status)
+		}
+	}
+	if approvalExecution != nil {
+		if exec, err := engine.GetExecution(ctx, approvalExecution.ID); err == nil {
+			fmt.Printf("Approval Workflow Status: %s\n", exec.Status)
+		}
+	}
+	if etlExecution != nil {
+		if exec, err := engine.GetExecution(ctx, etlExecution.ID); err == nil {
+			fmt.Printf("ETL Workflow Status: %s\n", exec.Status)
+		}
+	}
+}
+
+func startHTTPServer(engine *workflow.WorkflowEngine) {
+	fmt.Println("🌐 Starting HTTP server...")
+
+	// Create Fiber app
+	app := fiber.New(workflow.CORSConfig())
+
+	// Add middleware
+	app.Use(recover.New())
+	app.Use(logger.New())
+	app.Use(cors.New(cors.Config{
+		AllowOrigins: "*",
+		AllowMethods: "GET,POST,HEAD,PUT,DELETE,PATCH,OPTIONS",
+		AllowHeaders: "Origin, Content-Type, Accept, Authorization",
+	}))
+
+	// Create API handlers
+	api := workflow.NewWorkflowAPI(engine)
+	api.RegisterRoutes(app)
+
+	// Add demo routes
+	app.Get("/", func(c *fiber.Ctx) error {
+		return c.JSON(fiber.Map{
+			"message": "🚀 Workflow Engine Demo API",
+			"version": "1.0.0",
+			"endpoints": map[string]string{
+				"workflows":       "/api/v1/workflows",
+				"executions":      "/api/v1/workflows/executions",
+				"health":          "/api/v1/workflows/health",
+				"metrics":         "/api/v1/workflows/metrics",
+				"demo_workflows":  "/demo/workflows",
+				"demo_executions": "/demo/executions",
+			},
+		})
+	})
+
+	// Demo endpoints
+	demo := app.Group("/demo")
+	demo.Get("/workflows", func(c *fiber.Ctx) error {
+		workflows, err := engine.ListWorkflows(c.Context(), &workflow.WorkflowFilter{})
+		if err != nil {
+			return err
+		}
+		return c.JSON(fiber.Map{
+			"total":     len(workflows),
+			"workflows": workflows,
+		})
+	})
+
+	demo.Get("/executions", func(c *fiber.Ctx) error {
+		executions, err := engine.ListExecutions(c.Context(), &workflow.ExecutionFilter{})
+		if err != nil {
+			return err
+		}
+		return c.JSON(fiber.Map{
+			"total":      len(executions),
+			"executions": executions,
+		})
+	})
+
+	fmt.Println("📱 Demo endpoints available:")
+	fmt.Println("   • Main API: http://localhost:3000/")
+	fmt.Println("   • Workflows: http://localhost:3000/demo/workflows")
+	fmt.Println("   • Executions: http://localhost:3000/demo/executions")
+	fmt.Println("   • Health: http://localhost:3000/api/v1/workflows/health")
+	fmt.Println("   • Metrics: http://localhost:3000/api/v1/workflows/metrics")
+	fmt.Println()
+	fmt.Println("🎯 Try these API calls:")
+	fmt.Println("   curl http://localhost:3000/demo/workflows")
+	fmt.Println("   curl http://localhost:3000/demo/executions")
+	fmt.Println("   curl http://localhost:3000/api/v1/workflows/health")
+	fmt.Println()
+
+	// Start server
+	log.Fatal(app.Listen(":3000"))
+}

workflow/engine.go

@@ -0,0 +1,696 @@
+package workflow
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"sync"
+	"time"
+
+	"github.com/google/uuid"
+	"github.com/oarkflow/mq"
+	"github.com/oarkflow/mq/dag"
+)
+
+// WorkflowEngine - Main workflow engine
+type WorkflowEngine struct {
+	registry         WorkflowRegistry
+	stateManager     StateManager
+	executor         WorkflowExecutor
+	scheduler        WorkflowScheduler
+	processorFactory *ProcessorFactory
+	config           *Config
+	mu               sync.RWMutex
+	running          bool
+}
+
+// NewWorkflowEngine creates a new workflow engine
+func NewWorkflowEngine(config *Config) *WorkflowEngine {
+	engine := &WorkflowEngine{
+		registry:         NewInMemoryRegistry(),
+		stateManager:     NewInMemoryStateManager(),
+		processorFactory: NewProcessorFactory(),
+		config:           config,
+	}
+
+	// Create executor and scheduler
+	engine.executor = NewWorkflowExecutor(engine.processorFactory, engine.stateManager, config)
+	engine.scheduler = NewWorkflowScheduler(engine.stateManager, engine.executor)
+
+	return engine
+}
+
+// Start the workflow engine
+func (e *WorkflowEngine) Start(ctx context.Context) error {
+	e.mu.Lock()
+	defer e.mu.Unlock()
+
+	if e.running {
+		return fmt.Errorf("workflow engine is already running")
+	}
+
+	// Start components
+	if err := e.executor.Start(ctx); err != nil {
+		return fmt.Errorf("failed to start executor: %w", err)
+	}
+
+	if err := e.scheduler.Start(ctx); err != nil {
+		return fmt.Errorf("failed to start scheduler: %w", err)
+	}
+
+	e.running = true
+	return nil
+}
+
+// Stop the workflow engine
+func (e *WorkflowEngine) Stop(ctx context.Context) {
+	e.mu.Lock()
+	defer e.mu.Unlock()
+
+	if !e.running {
+		return
+	}
+
+	e.executor.Stop(ctx)
+	e.scheduler.Stop(ctx)
+	e.running = false
+}
+
+// RegisterWorkflow registers a new workflow definition
+func (e *WorkflowEngine) RegisterWorkflow(ctx context.Context, definition *WorkflowDefinition) error {
+	// Set timestamps
+	now := time.Now()
+	if definition.CreatedAt.IsZero() {
+		definition.CreatedAt = now
+	}
+	definition.UpdatedAt = now
+
+	// Validate workflow
+	if err := e.validateWorkflow(definition); err != nil {
+		return fmt.Errorf("workflow validation failed: %w", err)
+	}
+
+	return e.registry.Store(ctx, definition)
+}
+
+// GetWorkflow retrieves a workflow definition
+func (e *WorkflowEngine) GetWorkflow(ctx context.Context, id string, version string) (*WorkflowDefinition, error) {
+	return e.registry.Get(ctx, id, version)
+}
+
+// ListWorkflows lists workflow definitions with filtering
+func (e *WorkflowEngine) ListWorkflows(ctx context.Context, filter *WorkflowFilter) ([]*WorkflowDefinition, error) {
+	return e.registry.List(ctx, filter)
+}
+
+// DeleteWorkflow removes a workflow definition
+func (e *WorkflowEngine) DeleteWorkflow(ctx context.Context, id string) error {
+	return e.registry.Delete(ctx, id)
+}
+
+// ExecuteWorkflow starts workflow execution
+func (e *WorkflowEngine) ExecuteWorkflow(ctx context.Context, workflowID string, input map[string]interface{}, options *ExecutionOptions) (*Execution, error) {
+	// Get workflow definition
+	definition, err := e.registry.Get(ctx, workflowID, "")
+	if err != nil {
+		return nil, fmt.Errorf("failed to get workflow: %w", err)
+	}
+
+	// Create execution
+	execution := &Execution{
+		ID:              uuid.New().String(),
+		WorkflowID:      workflowID,
+		WorkflowVersion: definition.Version,
+		Status:          ExecutionStatusPending,
+		Input:           input,
+		Context: ExecutionContext{
+			Variables:   make(map[string]interface{}),
+			Metadata:    make(map[string]interface{}),
+			Trace:       []TraceEntry{},
+			Checkpoints: []Checkpoint{},
+		},
+		ExecutedNodes: []ExecutedNode{},
+		StartedAt:     time.Now(),
+		UpdatedAt:     time.Now(),
+		Priority:      PriorityMedium,
+	}
+
+	// Apply options
+	if options != nil {
+		if options.Priority != "" {
+			execution.Priority = options.Priority
+		}
+		if options.Owner != "" {
+			execution.Owner = options.Owner
+		}
+		if options.TriggeredBy != "" {
+			execution.TriggeredBy = options.TriggeredBy
+		}
+		if options.ParentExecution != "" {
+			execution.ParentExecution = options.ParentExecution
+		}
+		if options.Delay > 0 {
+			// Schedule for later execution
+			if err := e.scheduler.ScheduleExecution(ctx, execution, options.Delay); err != nil {
+				return nil, fmt.Errorf("failed to schedule execution: %w", err)
+			}
+			// Save execution in pending state
+			if err := e.stateManager.CreateExecution(ctx, execution); err != nil {
+				return nil, fmt.Errorf("failed to create execution: %w", err)
+			}
+			return execution, nil
+		}
+	}
+
+	// Save execution
+	if err := e.stateManager.CreateExecution(ctx, execution); err != nil {
+		return nil, fmt.Errorf("failed to create execution: %w", err)
+	}
+
+	// Start execution
+	go func() {
+		execution.Status = ExecutionStatusRunning
+		execution.UpdatedAt = time.Now()
+
+		if err := e.stateManager.UpdateExecution(context.Background(), execution); err != nil {
+			// Log error but continue
+		}
+
+		if err := e.executor.Execute(context.Background(), definition, execution); err != nil {
+			execution.Status = ExecutionStatusFailed
+			execution.Error = err.Error()
+			now := time.Now()
+			execution.CompletedAt = &now
+			execution.UpdatedAt = now
+			e.stateManager.UpdateExecution(context.Background(), execution)
+		}
+	}()
+
+	return execution, nil
+}
+
+// GetExecution retrieves execution status
+func (e *WorkflowEngine) GetExecution(ctx context.Context, executionID string) (*Execution, error) {
+	return e.stateManager.GetExecution(ctx, executionID)
+}
+
+// ListExecutions lists executions with filtering
+func (e *WorkflowEngine) ListExecutions(ctx context.Context, filter *ExecutionFilter) ([]*Execution, error) {
+	return e.stateManager.ListExecutions(ctx, filter)
+}
+
+// CancelExecution cancels a running execution
+func (e *WorkflowEngine) CancelExecution(ctx context.Context, executionID string) error {
+	return e.executor.Cancel(ctx, executionID)
+}
+
+// SuspendExecution suspends a running execution
+func (e *WorkflowEngine) SuspendExecution(ctx context.Context, executionID string) error {
+	return e.executor.Suspend(ctx, executionID)
+}
+
+// ResumeExecution resumes a suspended execution
+func (e *WorkflowEngine) ResumeExecution(ctx context.Context, executionID string) error {
+	return e.executor.Resume(ctx, executionID)
+}
+
+// validateWorkflow validates a workflow definition
+func (e *WorkflowEngine) validateWorkflow(definition *WorkflowDefinition) error {
+	if definition.ID == "" {
+		return fmt.Errorf("workflow ID cannot be empty")
+	}
+
+	if definition.Name == "" {
+		return fmt.Errorf("workflow name cannot be empty")
+	}
+
+	if definition.Version == "" {
+		return fmt.Errorf("workflow version cannot be empty")
+	}
+
+	if len(definition.Nodes) == 0 {
+		return fmt.Errorf("workflow must have at least one node")
+	}
+
+	// Validate nodes
+	nodeIDs := make(map[string]bool)
+	for _, node := range definition.Nodes {
+		if node.ID == "" {
+			return fmt.Errorf("node ID cannot be empty")
+		}
+
+		if nodeIDs[node.ID] {
+			return fmt.Errorf("duplicate node ID: %s", node.ID)
+		}
+		nodeIDs[node.ID] = true
+
+		if node.Type == "" {
+			return fmt.Errorf("node type cannot be empty for node: %s", node.ID)
+		}
+
+		// Validate node configuration based on type
+		if err := e.validateNodeConfig(node); err != nil {
+			return fmt.Errorf("invalid configuration for node %s: %w", node.ID, err)
+		}
+	}
+
+	// Validate edges
+	for _, edge := range definition.Edges {
+		if edge.FromNode == "" || edge.ToNode == "" {
+			return fmt.Errorf("edge must have both from_node and to_node")
+		}
+
+		if !nodeIDs[edge.FromNode] {
+			return fmt.Errorf("edge references unknown from_node: %s", edge.FromNode)
+		}
+
+		if !nodeIDs[edge.ToNode] {
+			return fmt.Errorf("edge references unknown to_node: %s", edge.ToNode)
+		}
+	}
+
+	return nil
+}
+
+func (e *WorkflowEngine) validateNodeConfig(node WorkflowNode) error {
+	switch node.Type {
+	case NodeTypeAPI:
+		if node.Config.URL == "" {
+			return fmt.Errorf("API node requires URL")
+		}
+		if node.Config.Method == "" {
+			return fmt.Errorf("API node requires HTTP method")
+		}
+
+	case NodeTypeTransform:
+		if node.Config.TransformType == "" {
+			return fmt.Errorf("Transform node requires transform_type")
+		}
+
+	case NodeTypeDecision:
+		if node.Config.Condition == "" && len(node.Config.DecisionRules) == 0 {
+			return fmt.Errorf("Decision node requires either condition or rules")
+		}
+
+	case NodeTypeTimer:
+		if node.Config.Duration <= 0 && node.Config.Schedule == "" {
+			return fmt.Errorf("Timer node requires either duration or schedule")
+		}
+
+	case NodeTypeDatabase:
+		if node.Config.Query == "" {
+			return fmt.Errorf("Database node requires query")
+		}
+
+	case NodeTypeEmail:
+		if len(node.Config.EmailTo) == 0 {
+			return fmt.Errorf("Email node requires recipients")
+		}
+	}
+
+	return nil
+}
+
+// ExecutionOptions for workflow execution
+type ExecutionOptions struct {
+	Priority        Priority      `json:"priority"`
+	Owner           string        `json:"owner"`
+	TriggeredBy     string        `json:"triggered_by"`
+	ParentExecution string        `json:"parent_execution"`
+	Delay           time.Duration `json:"delay"`
+}
+
+// Simple Executor Implementation
+type SimpleWorkflowExecutor struct {
+	processorFactory *ProcessorFactory
+	stateManager     StateManager
+	config           *Config
+	workers          chan struct{}
+	running          bool
+	executions       map[string]*ExecutionControl
+	mu               sync.RWMutex
+}
+
+type ExecutionControl struct {
+	cancel    context.CancelFunc
+	suspended bool
+}
+
+func NewWorkflowExecutor(processorFactory *ProcessorFactory, stateManager StateManager, config *Config) WorkflowExecutor {
+	return &SimpleWorkflowExecutor{
+		processorFactory: processorFactory,
+		stateManager:     stateManager,
+		config:           config,
+		workers:          make(chan struct{}, config.MaxWorkers),
+		executions:       make(map[string]*ExecutionControl),
+	}
+}
+
+func (e *SimpleWorkflowExecutor) Start(ctx context.Context) error {
+	e.mu.Lock()
+	defer e.mu.Unlock()
+
+	e.running = true
+
+	// Initialize worker pool
+	for i := 0; i < e.config.MaxWorkers; i++ {
+		e.workers <- struct{}{}
+	}
+
+	return nil
+}
+
+func (e *SimpleWorkflowExecutor) Stop(ctx context.Context) {
+	e.mu.Lock()
+	defer e.mu.Unlock()
+
+	e.running = false
+	close(e.workers)
+
+	// Cancel all running executions
+	for _, control := range e.executions {
+		if control.cancel != nil {
+			control.cancel()
+		}
+	}
+}
+
+func (e *SimpleWorkflowExecutor) Execute(ctx context.Context, definition *WorkflowDefinition, execution *Execution) error {
+	// Get a worker
+	<-e.workers
+	defer func() {
+		if e.running {
+			e.workers <- struct{}{}
+		}
+	}()
+
+	// Create cancellable context
+	execCtx, cancel := context.WithCancel(ctx)
+	defer cancel()
+
+	// Track execution
+	e.mu.Lock()
+	e.executions[execution.ID] = &ExecutionControl{cancel: cancel}
+	e.mu.Unlock()
+
+	defer func() {
+		e.mu.Lock()
+		delete(e.executions, execution.ID)
+		e.mu.Unlock()
+	}()
+
+	// Convert workflow to DAG and execute
+	dag, err := e.convertToDAG(definition, execution)
+	if err != nil {
+		return fmt.Errorf("failed to convert workflow to DAG: %w", err)
+	}
+
+	// Execute the DAG
+	inputBytes, err := json.Marshal(execution.Input)
+	if err != nil {
+		return fmt.Errorf("failed to serialize input: %w", err)
+	}
+
+	result := dag.Process(execCtx, inputBytes)
+
+	// Update execution state
+	execution.Status = ExecutionStatusCompleted
+	if result.Error != nil {
+		execution.Status = ExecutionStatusFailed
+		execution.Error = result.Error.Error()
+	} else {
+		// Deserialize output
+		var output map[string]interface{}
+		if err := json.Unmarshal(result.Payload, &output); err == nil {
+			execution.Output = output
+		}
+	}
+
+	now := time.Now()
+	execution.CompletedAt = &now
+	execution.UpdatedAt = now
+
+	return e.stateManager.UpdateExecution(ctx, execution)
+}
+
+func (e *SimpleWorkflowExecutor) Cancel(ctx context.Context, executionID string) error {
+	e.mu.RLock()
+	control, exists := e.executions[executionID]
+	e.mu.RUnlock()
+
+	if !exists {
+		return fmt.Errorf("execution not found: %s", executionID)
+	}
+
+	if control.cancel != nil {
+		control.cancel()
+	}
+
+	// Update execution status
+	execution, err := e.stateManager.GetExecution(ctx, executionID)
+	if err != nil {
+		return err
+	}
+
+	execution.Status = ExecutionStatusCancelled
+	now := time.Now()
+	execution.CompletedAt = &now
+	execution.UpdatedAt = now
+
+	return e.stateManager.UpdateExecution(ctx, execution)
+}
+
+func (e *SimpleWorkflowExecutor) Suspend(ctx context.Context, executionID string) error {
+	e.mu.Lock()
+	defer e.mu.Unlock()
+
+	control, exists := e.executions[executionID]
+	if !exists {
+		return fmt.Errorf("execution not found: %s", executionID)
+	}
+
+	control.suspended = true
+
+	// Update execution status
+	execution, err := e.stateManager.GetExecution(ctx, executionID)
+	if err != nil {
+		return err
+	}
+
+	execution.Status = ExecutionStatusSuspended
+	execution.UpdatedAt = time.Now()
+
+	return e.stateManager.UpdateExecution(ctx, execution)
+}
+
+func (e *SimpleWorkflowExecutor) Resume(ctx context.Context, executionID string) error {
+	e.mu.Lock()
+	defer e.mu.Unlock()
+
+	control, exists := e.executions[executionID]
+	if !exists {
+		return fmt.Errorf("execution not found: %s", executionID)
+	}
+
+	control.suspended = false
+
+	// Update execution status
+	execution, err := e.stateManager.GetExecution(ctx, executionID)
+	if err != nil {
+		return err
+	}
+
+	execution.Status = ExecutionStatusRunning
+	execution.UpdatedAt = time.Now()
+
+	return e.stateManager.UpdateExecution(ctx, execution)
+}
+
+func (e *SimpleWorkflowExecutor) convertToDAG(definition *WorkflowDefinition, execution *Execution) (*dag.DAG, error) {
+	// Create a new DAG
+	dagInstance := dag.NewDAG(
+		fmt.Sprintf("workflow-%s", definition.ID),
+		execution.ID,
+		func(taskID string, result mq.Result) {
+			// Handle final result
+		},
+	)
+
+	// Create DAG nodes for each workflow node
+	for _, node := range definition.Nodes {
+		processor, err := e.processorFactory.CreateProcessor(string(node.Type))
+		if err != nil {
+			return nil, fmt.Errorf("failed to create processor for node %s: %w", node.ID, err)
+		}
+
+		// Wrap processor in a DAG processor adapter
+		dagProcessor := &DAGProcessorAdapter{
+			processor: processor,
+			nodeID:    node.ID,
+			execution: execution,
+		}
+
+		// Add node to DAG
+		dagInstance.AddNode(dag.Function, node.Name, node.ID, dagProcessor, false)
+	}
+
+	// Add dependencies based on edges
+	for _, edge := range definition.Edges {
+		dagInstance.AddEdge(dag.Simple, edge.ID, edge.FromNode, edge.ToNode)
+	}
+
+	return dagInstance, nil
+}
+
+// DAGProcessorAdapter adapts Processor to DAG Processor interface
+type DAGProcessorAdapter struct {
+	dag.Operation
+	processor Processor
+	nodeID    string
+	execution *Execution
+}
+
+func (a *DAGProcessorAdapter) ProcessTask(ctx context.Context, task *mq.Task) mq.Result {
+	// Convert task payload to ProcessingContext
+	var data map[string]interface{}
+	if err := json.Unmarshal(task.Payload, &data); err != nil {
+		return mq.Result{Error: fmt.Errorf("failed to unmarshal task payload: %v", err)}
+	}
+
+	// Create a minimal workflow node for processing (in real implementation, this would be passed in)
+	workflowNode := &WorkflowNode{
+		ID:     a.nodeID,
+		Type:   NodeTypeTask, // Default type, this should be set properly
+		Config: NodeConfig{},
+	}
+
+	processingContext := ProcessingContext{
+		Node:      workflowNode,
+		Data:      data,
+		Variables: make(map[string]interface{}),
+	}
+
+	result, err := a.processor.Process(ctx, processingContext)
+	if err != nil {
+		return mq.Result{Error: err}
+	}
+
+	// Convert ProcessingResult back to mq.Result
+	var payload []byte
+	if result.Data != nil {
+		payload, _ = json.Marshal(result.Data)
+	}
+
+	mqResult := mq.Result{
+		Payload: payload,
+	}
+
+	if !result.Success {
+		mqResult.Error = fmt.Errorf(result.Error)
+	}
+
+	// Track node execution
+	executedNode := ExecutedNode{
+		NodeID:    a.nodeID,
+		Status:    ExecutionStatusCompleted,
+		StartedAt: time.Now(),
+		Input:     data,
+		Output:    result.Data,
+		Logs:      []LogEntry{},
+	}
+
+	if !result.Success {
+		executedNode.Status = ExecutionStatusFailed
+		executedNode.Error = result.Error
+	}
+
+	now := time.Now()
+	executedNode.CompletedAt = &now
+	executedNode.Duration = time.Since(executedNode.StartedAt)
+
+	// Add to execution history (in real implementation, use thread-safe approach)
+	if a.execution != nil {
+		a.execution.ExecutedNodes = append(a.execution.ExecutedNodes, executedNode)
+	}
+
+	return mqResult
+}
+
+// Simple Scheduler Implementation
+type SimpleWorkflowScheduler struct {
+	stateManager StateManager
+	executor     WorkflowExecutor
+	running      bool
+	mu           sync.Mutex
+	scheduled    map[string]*time.Timer
+}
+
+func NewWorkflowScheduler(stateManager StateManager, executor WorkflowExecutor) WorkflowScheduler {
+	return &SimpleWorkflowScheduler{
+		stateManager: stateManager,
+		executor:     executor,
+		scheduled:    make(map[string]*time.Timer),
+	}
+}
+
+func (s *SimpleWorkflowScheduler) Start(ctx context.Context) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	s.running = true
+	return nil
+}
+
+func (s *SimpleWorkflowScheduler) Stop(ctx context.Context) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	s.running = false
+
+	// Cancel all scheduled executions
+	for _, timer := range s.scheduled {
+		timer.Stop()
+	}
+	s.scheduled = make(map[string]*time.Timer)
+}
+
+func (s *SimpleWorkflowScheduler) ScheduleExecution(ctx context.Context, execution *Execution, delay time.Duration) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	if !s.running {
+		return fmt.Errorf("scheduler is not running")
+	}
+
+	// Create timer for delayed execution
+	timer := time.AfterFunc(delay, func() {
+		// Remove from scheduled map
+		s.mu.Lock()
+		delete(s.scheduled, execution.ID)
+		s.mu.Unlock()
+
+		// Execute workflow (implementation depends on having access to workflow definition)
+		// For now, just update status
+		execution.Status = ExecutionStatusRunning
+		execution.UpdatedAt = time.Now()
+		s.stateManager.UpdateExecution(context.Background(), execution)
+	})
+
+	s.scheduled[execution.ID] = timer
+	return nil
+}
+
+func (s *SimpleWorkflowScheduler) CancelScheduledExecution(ctx context.Context, executionID string) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	timer, exists := s.scheduled[executionID]
+	if !exists {
+		return fmt.Errorf("scheduled execution not found: %s", executionID)
+	}
+
+	timer.Stop()
+	delete(s.scheduled, executionID)
+
+	return nil
+}

workflow/middleware.go

@@ -0,0 +1,590 @@
+package workflow
+
+import (
+	"context"
+	"fmt"
+	"log"
+	"strings"
+	"sync"
+	"time"
+)
+
+// MiddlewareManager manages middleware execution chain
+type MiddlewareManager struct {
+	middlewares []Middleware
+	cache       map[string]*MiddlewareResult
+	mutex       sync.RWMutex
+}
+
+// MiddlewareFunc is the function signature for middleware
+type MiddlewareFunc func(ctx context.Context, data map[string]interface{}, next func(context.Context, map[string]interface{}) MiddlewareResult) MiddlewareResult
+
+// MiddlewareChain represents a chain of middleware functions
+type MiddlewareChain struct {
+	middlewares []MiddlewareFunc
+}
+
+// NewMiddlewareManager creates a new middleware manager
+func NewMiddlewareManager() *MiddlewareManager {
+	return &MiddlewareManager{
+		middlewares: make([]Middleware, 0),
+		cache:       make(map[string]*MiddlewareResult),
+	}
+}
+
+// AddMiddleware adds a middleware to the chain
+func (m *MiddlewareManager) AddMiddleware(middleware Middleware) {
+	m.mutex.Lock()
+	defer m.mutex.Unlock()
+
+	// Insert middleware in priority order
+	inserted := false
+	for i, existing := range m.middlewares {
+		if middleware.Priority < existing.Priority {
+			m.middlewares = append(m.middlewares[:i], append([]Middleware{middleware}, m.middlewares[i:]...)...)
+			inserted = true
+			break
+		}
+	}
+
+	if !inserted {
+		m.middlewares = append(m.middlewares, middleware)
+	}
+}
+
+// Execute runs the middleware chain
+func (m *MiddlewareManager) Execute(ctx context.Context, data map[string]interface{}) MiddlewareResult {
+	m.mutex.RLock()
+	defer m.mutex.RUnlock()
+
+	if len(m.middlewares) == 0 {
+		return MiddlewareResult{Continue: true, Data: data}
+	}
+
+	return m.executeChain(ctx, data, 0)
+}
+
+// executeChain recursively executes middleware chain
+func (m *MiddlewareManager) executeChain(ctx context.Context, data map[string]interface{}, index int) MiddlewareResult {
+	if index >= len(m.middlewares) {
+		return MiddlewareResult{Continue: true, Data: data}
+	}
+
+	middleware := m.middlewares[index]
+	if !middleware.Enabled {
+		return m.executeChain(ctx, data, index+1)
+	}
+
+	// Create the next function
+	next := func(ctx context.Context, data map[string]interface{}) MiddlewareResult {
+		return m.executeChain(ctx, data, index+1)
+	}
+
+	// Execute current middleware
+	return m.executeMiddleware(ctx, middleware, data, next)
+}
+
+// executeMiddleware executes a single middleware
+func (m *MiddlewareManager) executeMiddleware(ctx context.Context, middleware Middleware, data map[string]interface{}, next func(context.Context, map[string]interface{}) MiddlewareResult) MiddlewareResult {
+	switch middleware.Type {
+	case MiddlewareAuth:
+		return m.executeAuthMiddleware(ctx, middleware, data, next)
+	case MiddlewareLogging:
+		return m.executeLoggingMiddleware(ctx, middleware, data, next)
+	case MiddlewareRateLimit:
+		return m.executeRateLimitMiddleware(ctx, middleware, data, next)
+	case MiddlewareValidate:
+		return m.executeValidateMiddleware(ctx, middleware, data, next)
+	case MiddlewareTransform:
+		return m.executeTransformMiddleware(ctx, middleware, data, next)
+	case MiddlewareCustom:
+		return m.executeCustomMiddleware(ctx, middleware, data, next)
+	default:
+		// Unknown middleware type, continue
+		return next(ctx, data)
+	}
+}
+
+// Auth middleware implementation
+func (m *MiddlewareManager) executeAuthMiddleware(ctx context.Context, middleware Middleware, data map[string]interface{}, next func(context.Context, map[string]interface{}) MiddlewareResult) MiddlewareResult {
+	// Extract token from data or context
+	token, exists := data["auth_token"].(string)
+	if !exists {
+		if authHeader, ok := data["headers"].(map[string]string); ok {
+			if auth, ok := authHeader["Authorization"]; ok {
+				token = auth
+			}
+		}
+	}
+
+	if token == "" {
+		return MiddlewareResult{
+			Continue: false,
+			Error:    fmt.Errorf("authentication token required"),
+			Data:     data,
+		}
+	}
+
+	// Validate token (simplified)
+	if !isValidToken(token) {
+		return MiddlewareResult{
+			Continue: false,
+			Error:    fmt.Errorf("invalid authentication token"),
+			Data:     data,
+		}
+	}
+
+	// Add user context
+	username := extractUsernameFromToken(token)
+	user := &User{
+		ID:          username,
+		Username:    username,
+		Role:        UserRoleOperator,
+		Permissions: getUserPermissions(username),
+	}
+
+	authContext := &AuthContext{
+		User:        user,
+		Token:       token,
+		Permissions: user.Permissions,
+	}
+
+	data["auth_context"] = authContext
+	data["user"] = user
+
+	return next(ctx, data)
+}
+
+// Logging middleware implementation
+func (m *MiddlewareManager) executeLoggingMiddleware(ctx context.Context, middleware Middleware, data map[string]interface{}, next func(context.Context, map[string]interface{}) MiddlewareResult) MiddlewareResult {
+	startTime := time.Now()
+
+	// Log request
+	log.Printf("[MIDDLEWARE] %s - Started processing request", middleware.Name)
+
+	// Continue to next middleware
+	result := next(ctx, data)
+
+	// Log response
+	duration := time.Since(startTime)
+	if result.Error != nil {
+		log.Printf("[MIDDLEWARE] %s - Completed with error in %v: %v", middleware.Name, duration, result.Error)
+	} else {
+		log.Printf("[MIDDLEWARE] %s - Completed successfully in %v", middleware.Name, duration)
+	}
+
+	return result
+}
+
+// Rate limiting middleware implementation
+func (m *MiddlewareManager) executeRateLimitMiddleware(ctx context.Context, middleware Middleware, data map[string]interface{}, next func(context.Context, map[string]interface{}) MiddlewareResult) MiddlewareResult {
+	// Get user/IP for rate limiting
+	identifier := "anonymous"
+	if user, exists := data["user"].(*User); exists {
+		identifier = user.ID
+	} else if ip, exists := data["client_ip"].(string); exists {
+		identifier = ip
+	}
+
+	// Check rate limit (simplified implementation)
+	limit := getConfigInt(middleware.Config, "requests_per_minute", 60)
+	if !checkRateLimit(identifier, limit) {
+		return MiddlewareResult{
+			Continue: false,
+			Error:    fmt.Errorf("rate limit exceeded for %s", identifier),
+			Data:     data,
+		}
+	}
+
+	return next(ctx, data)
+}
+
+// Validation middleware implementation
+func (m *MiddlewareManager) executeValidateMiddleware(ctx context.Context, middleware Middleware, data map[string]interface{}, next func(context.Context, map[string]interface{}) MiddlewareResult) MiddlewareResult {
+	// Get validation rules from config
+	rules, exists := middleware.Config["rules"].([]interface{})
+	if !exists {
+		return next(ctx, data)
+	}
+
+	// Validate data
+	for _, rule := range rules {
+		if ruleMap, ok := rule.(map[string]interface{}); ok {
+			field := ruleMap["field"].(string)
+			ruleType := ruleMap["type"].(string)
+
+			if err := validateDataField(data, field, ruleType, ruleMap); err != nil {
+				return MiddlewareResult{
+					Continue: false,
+					Error:    fmt.Errorf("validation failed: %v", err),
+					Data:     data,
+				}
+			}
+		}
+	}
+
+	return next(ctx, data)
+}
+
+// Transform middleware implementation
+func (m *MiddlewareManager) executeTransformMiddleware(ctx context.Context, middleware Middleware, data map[string]interface{}, next func(context.Context, map[string]interface{}) MiddlewareResult) MiddlewareResult {
+	// Get transformation rules from config
+	transforms, exists := middleware.Config["transforms"].(map[string]interface{})
+	if !exists {
+		return next(ctx, data)
+	}
+
+	// Apply transformations
+	for field, transform := range transforms {
+		if transformType, ok := transform.(string); ok {
+			switch transformType {
+			case "lowercase":
+				if value, exists := data[field].(string); exists {
+					data[field] = strings.ToLower(value)
+				}
+			case "uppercase":
+				if value, exists := data[field].(string); exists {
+					data[field] = strings.ToUpper(value)
+				}
+			case "trim":
+				if value, exists := data[field].(string); exists {
+					data[field] = strings.TrimSpace(value)
+				}
+			}
+		}
+	}
+
+	return next(ctx, data)
+}
+
+// Custom middleware implementation
+func (m *MiddlewareManager) executeCustomMiddleware(ctx context.Context, middleware Middleware, data map[string]interface{}, next func(context.Context, map[string]interface{}) MiddlewareResult) MiddlewareResult {
+	// Custom middleware can be implemented by users
+	// For now, just pass through
+	return next(ctx, data)
+}
+
+// Permission checking
+type PermissionChecker struct {
+	permissions map[string][]Permission
+	mutex       sync.RWMutex
+}
+
+// NewPermissionChecker creates a new permission checker
+func NewPermissionChecker() *PermissionChecker {
+	return &PermissionChecker{
+		permissions: make(map[string][]Permission),
+	}
+}
+
+// AddPermission adds a permission for a user
+func (p *PermissionChecker) AddPermission(userID string, permission Permission) {
+	p.mutex.Lock()
+	defer p.mutex.Unlock()
+
+	if p.permissions[userID] == nil {
+		p.permissions[userID] = make([]Permission, 0)
+	}
+
+	p.permissions[userID] = append(p.permissions[userID], permission)
+}
+
+// CheckPermission checks if a user has permission for an action
+func (p *PermissionChecker) CheckPermission(userID, resource string, action PermissionAction) bool {
+	p.mutex.RLock()
+	defer p.mutex.RUnlock()
+
+	permissions, exists := p.permissions[userID]
+	if !exists {
+		return false
+	}
+
+	for _, perm := range permissions {
+		if perm.Resource == resource && perm.Action == action {
+			return true
+		}
+		// Check for admin permission
+		if perm.Action == PermissionAdmin {
+			return true
+		}
+	}
+
+	return false
+}
+
+// Utility functions for middleware
+
+// Rate limiting cache
+var rateLimitCache = make(map[string][]time.Time)
+var rateLimitMutex sync.RWMutex
+
+func checkRateLimit(identifier string, requestsPerMinute int) bool {
+	rateLimitMutex.Lock()
+	defer rateLimitMutex.Unlock()
+
+	now := time.Now()
+	cutoff := now.Add(-time.Minute)
+
+	// Initialize if not exists
+	if rateLimitCache[identifier] == nil {
+		rateLimitCache[identifier] = make([]time.Time, 0)
+	}
+
+	// Remove old entries
+	requests := rateLimitCache[identifier]
+	validRequests := make([]time.Time, 0)
+	for _, req := range requests {
+		if req.After(cutoff) {
+			validRequests = append(validRequests, req)
+		}
+	}
+
+	// Check if limit exceeded
+	if len(validRequests) >= requestsPerMinute {
+		return false
+	}
+
+	// Add current request
+	validRequests = append(validRequests, now)
+	rateLimitCache[identifier] = validRequests
+
+	return true
+}
+
+func getConfigInt(config map[string]interface{}, key string, defaultValue int) int {
+	if value, exists := config[key]; exists {
+		if intValue, ok := value.(int); ok {
+			return intValue
+		}
+		if floatValue, ok := value.(float64); ok {
+			return int(floatValue)
+		}
+	}
+	return defaultValue
+}
+
+func validateDataField(data map[string]interface{}, field, ruleType string, rule map[string]interface{}) error {
+	value, exists := data[field]
+
+	switch ruleType {
+	case "required":
+		if !exists || value == nil || value == "" {
+			return fmt.Errorf("field '%s' is required", field)
+		}
+	case "type":
+		expectedType := rule["expected"].(string)
+		if !isCorrectType(value, expectedType) {
+			return fmt.Errorf("field '%s' must be of type %s", field, expectedType)
+		}
+	case "length":
+		if str, ok := value.(string); ok {
+			minLen := int(rule["min"].(float64))
+			maxLen := int(rule["max"].(float64))
+			if len(str) < minLen || len(str) > maxLen {
+				return fmt.Errorf("field '%s' length must be between %d and %d", field, minLen, maxLen)
+			}
+		}
+	}
+
+	return nil
+}
+
+// User management system
+type UserManager struct {
+	users             map[string]*User
+	sessions          map[string]*AuthContext
+	permissionChecker *PermissionChecker
+	mutex             sync.RWMutex
+}
+
+// NewUserManager creates a new user manager
+func NewUserManager() *UserManager {
+	return &UserManager{
+		users:             make(map[string]*User),
+		sessions:          make(map[string]*AuthContext),
+		permissionChecker: NewPermissionChecker(),
+	}
+}
+
+// CreateUser creates a new user
+func (u *UserManager) CreateUser(user *User) error {
+	u.mutex.Lock()
+	defer u.mutex.Unlock()
+
+	if _, exists := u.users[user.ID]; exists {
+		return fmt.Errorf("user %s already exists", user.ID)
+	}
+
+	user.CreatedAt = time.Now()
+	user.UpdatedAt = time.Now()
+	u.users[user.ID] = user
+
+	// Add default permissions based on role
+	u.addDefaultPermissions(user)
+
+	return nil
+}
+
+// GetUser retrieves a user by ID
+func (u *UserManager) GetUser(userID string) (*User, error) {
+	u.mutex.RLock()
+	defer u.mutex.RUnlock()
+
+	user, exists := u.users[userID]
+	if !exists {
+		return nil, fmt.Errorf("user %s not found", userID)
+	}
+
+	return user, nil
+}
+
+// AuthenticateUser authenticates a user and creates a session
+func (u *UserManager) AuthenticateUser(username, password string) (*AuthContext, error) {
+	u.mutex.Lock()
+	defer u.mutex.Unlock()
+
+	// Find user by username
+	var user *User
+	for _, u := range u.users {
+		if u.Username == username {
+			user = u
+			break
+		}
+	}
+
+	if user == nil {
+		return nil, fmt.Errorf("invalid credentials")
+	}
+
+	// In production, properly hash and verify password
+	if password != "password" {
+		return nil, fmt.Errorf("invalid credentials")
+	}
+
+	// Create session
+	sessionID := generateSessionID()
+	token := generateToken(user)
+
+	authContext := &AuthContext{
+		User:        user,
+		SessionID:   sessionID,
+		Token:       token,
+		Permissions: user.Permissions,
+	}
+
+	u.sessions[sessionID] = authContext
+
+	return authContext, nil
+}
+
+// ValidateSession validates a session token
+func (u *UserManager) ValidateSession(token string) (*AuthContext, error) {
+	u.mutex.RLock()
+	defer u.mutex.RUnlock()
+
+	for _, session := range u.sessions {
+		if session.Token == token {
+			return session, nil
+		}
+	}
+
+	return nil, fmt.Errorf("invalid session token")
+}
+
+// addDefaultPermissions adds default permissions based on user role
+func (u *UserManager) addDefaultPermissions(user *User) {
+	switch user.Role {
+	case UserRoleAdmin:
+		u.permissionChecker.AddPermission(user.ID, Permission{
+			Resource: "*",
+			Action:   PermissionAdmin,
+		})
+	case UserRoleManager:
+		u.permissionChecker.AddPermission(user.ID, Permission{
+			Resource: "workflow",
+			Action:   PermissionRead,
+		})
+		u.permissionChecker.AddPermission(user.ID, Permission{
+			Resource: "workflow",
+			Action:   PermissionWrite,
+		})
+		u.permissionChecker.AddPermission(user.ID, Permission{
+			Resource: "workflow",
+			Action:   PermissionExecute,
+		})
+	case UserRoleOperator:
+		u.permissionChecker.AddPermission(user.ID, Permission{
+			Resource: "workflow",
+			Action:   PermissionRead,
+		})
+		u.permissionChecker.AddPermission(user.ID, Permission{
+			Resource: "workflow",
+			Action:   PermissionExecute,
+		})
+	case UserRoleViewer:
+		u.permissionChecker.AddPermission(user.ID, Permission{
+			Resource: "workflow",
+			Action:   PermissionRead,
+		})
+	}
+}
+
+func generateSessionID() string {
+	return fmt.Sprintf("session_%d", time.Now().UnixNano())
+}
+
+// Helper functions for authentication middleware
+func isValidToken(token string) bool {
+	// Simple token validation - in real implementation, verify JWT or session token
+	return token != "" && len(token) > 10
+}
+
+func extractUsernameFromToken(token string) string {
+	// Simple username extraction - in real implementation, decode JWT claims
+	if strings.HasPrefix(token, "bearer_") {
+		return strings.TrimPrefix(token, "bearer_")
+	}
+	return "unknown"
+}
+
+func getUserPermissions(username string) []string {
+	// Simple permission mapping - in real implementation, fetch from database
+	switch username {
+	case "admin":
+		return []string{"read", "write", "execute", "delete"}
+	case "manager":
+		return []string{"read", "write", "execute"}
+	default:
+		return []string{"read"}
+	}
+}
+
+func isCorrectType(value interface{}, expectedType string) bool {
+	switch expectedType {
+	case "string":
+		_, ok := value.(string)
+		return ok
+	case "number":
+		_, ok := value.(float64)
+		if !ok {
+			_, ok = value.(int)
+		}
+		return ok
+	case "boolean":
+		_, ok := value.(bool)
+		return ok
+	case "array":
+		_, ok := value.([]interface{})
+		return ok
+	case "object":
+		_, ok := value.(map[string]interface{})
+		return ok
+	default:
+		return false
+	}
+}
+
+func generateToken(user *User) string {
+	// Simple token generation - in real implementation, create JWT
+	return fmt.Sprintf("token_%s_%d", user.Username, time.Now().Unix())
+}

workflow/processors.go

@@ -0,0 +1,393 @@
+package workflow
+
+import (
+	"context"
+	"fmt"
+	"log"
+	"strings"
+	"time"
+)
+
+// ProcessorFactory creates processor instances for different node types
+type ProcessorFactory struct {
+	processors map[string]func() Processor
+}
+
+// NewProcessorFactory creates a new processor factory with all registered processors
+func NewProcessorFactory() *ProcessorFactory {
+	factory := &ProcessorFactory{
+		processors: make(map[string]func() Processor),
+	}
+
+	// Register basic processors
+	factory.RegisterProcessor("task", func() Processor { return &TaskProcessor{} })
+	factory.RegisterProcessor("api", func() Processor { return &APIProcessor{} })
+	factory.RegisterProcessor("transform", func() Processor { return &TransformProcessor{} })
+	factory.RegisterProcessor("decision", func() Processor { return &DecisionProcessor{} })
+	factory.RegisterProcessor("timer", func() Processor { return &TimerProcessor{} })
+	factory.RegisterProcessor("parallel", func() Processor { return &ParallelProcessor{} })
+	factory.RegisterProcessor("sequence", func() Processor { return &SequenceProcessor{} })
+	factory.RegisterProcessor("loop", func() Processor { return &LoopProcessor{} })
+	factory.RegisterProcessor("filter", func() Processor { return &FilterProcessor{} })
+	factory.RegisterProcessor("aggregator", func() Processor { return &AggregatorProcessor{} })
+	factory.RegisterProcessor("error", func() Processor { return &ErrorProcessor{} })
+
+	// Register advanced processors
+	factory.RegisterProcessor("subdag", func() Processor { return &SubDAGProcessor{} })
+	factory.RegisterProcessor("html", func() Processor { return &HTMLProcessor{} })
+	factory.RegisterProcessor("sms", func() Processor { return &SMSProcessor{} })
+	factory.RegisterProcessor("auth", func() Processor { return &AuthProcessor{} })
+	factory.RegisterProcessor("validator", func() Processor { return &ValidatorProcessor{} })
+	factory.RegisterProcessor("router", func() Processor { return &RouterProcessor{} })
+	factory.RegisterProcessor("storage", func() Processor { return &StorageProcessor{} })
+	factory.RegisterProcessor("notify", func() Processor { return &NotifyProcessor{} })
+	factory.RegisterProcessor("webhook_receiver", func() Processor { return &WebhookReceiverProcessor{} })
+
+	return factory
+}
+
+// RegisterProcessor registers a new processor type
+func (f *ProcessorFactory) RegisterProcessor(nodeType string, creator func() Processor) {
+	f.processors[nodeType] = creator
+}
+
+// CreateProcessor creates a processor instance for the given node type
+func (f *ProcessorFactory) CreateProcessor(nodeType string) (Processor, error) {
+	creator, exists := f.processors[nodeType]
+	if !exists {
+		return nil, fmt.Errorf("unknown processor type: %s", nodeType)
+	}
+	return creator(), nil
+}
+
+// Basic Processors
+
+// TaskProcessor handles task execution
+type TaskProcessor struct{}
+
+func (p *TaskProcessor) Process(ctx context.Context, input ProcessingContext) (*ProcessingResult, error) {
+	log.Printf("Executing task: %s", input.Node.Name)
+
+	// Execute the task based on configuration
+	config := input.Node.Config
+
+	// Simulate task execution based on script or command
+	if config.Script != "" {
+		log.Printf("Executing script: %s", config.Script)
+	} else if config.Command != "" {
+		log.Printf("Executing command: %s", config.Command)
+	}
+
+	time.Sleep(100 * time.Millisecond)
+
+	result := &ProcessingResult{
+		Success: true,
+		Data:    map[string]interface{}{"task_completed": true, "task_name": input.Node.Name},
+		Message: fmt.Sprintf("Task %s completed successfully", input.Node.Name),
+	}
+
+	return result, nil
+}
+
+// APIProcessor handles API calls
+type APIProcessor struct{}
+
+func (p *APIProcessor) Process(ctx context.Context, input ProcessingContext) (*ProcessingResult, error) {
+	config := input.Node.Config
+
+	url := config.URL
+	if url == "" {
+		return &ProcessingResult{
+			Success: false,
+			Error:   "URL not specified in API configuration",
+		}, nil
+	}
+
+	method := "GET"
+	if config.Method != "" {
+		method = strings.ToUpper(config.Method)
+	}
+
+	log.Printf("Making %s request to %s", method, url)
+
+	// Simulate API call
+	time.Sleep(200 * time.Millisecond)
+
+	// Mock response
+	response := map[string]interface{}{
+		"status": "success",
+		"url":    url,
+		"method": method,
+		"data":   "mock response data",
+	}
+
+	return &ProcessingResult{
+		Success: true,
+		Data:    response,
+		Message: fmt.Sprintf("API call to %s completed", url),
+	}, nil
+}
+
+// TransformProcessor handles data transformation
+type TransformProcessor struct{}
+
+func (p *TransformProcessor) Process(ctx context.Context, input ProcessingContext) (*ProcessingResult, error) {
+	config := input.Node.Config
+
+	// Get transformation rules from Custom config
+	transforms, ok := config.Custom["transforms"].(map[string]interface{})
+	if !ok {
+		return &ProcessingResult{
+			Success: false,
+			Error:   "No transformation rules specified",
+		}, nil
+	}
+
+	// Apply transformations to input data
+	result := make(map[string]interface{})
+	for key, rule := range transforms {
+		// Simple field mapping for now
+		if sourceField, ok := rule.(string); ok {
+			if value, exists := input.Data[sourceField]; exists {
+				result[key] = value
+			}
+		}
+	}
+
+	return &ProcessingResult{
+		Success: true,
+		Data:    result,
+		Message: "Data transformation completed",
+	}, nil
+}
+
+// DecisionProcessor handles conditional logic
+type DecisionProcessor struct{}
+
+func (p *DecisionProcessor) Process(ctx context.Context, input ProcessingContext) (*ProcessingResult, error) {
+	config := input.Node.Config
+
+	condition := config.Condition
+	if condition == "" {
+		return &ProcessingResult{
+			Success: false,
+			Error:   "No condition specified",
+		}, nil
+	}
+
+	// Simple condition evaluation
+	decision := p.evaluateCondition(condition, input.Data)
+
+	result := &ProcessingResult{
+		Success: true,
+		Data: map[string]interface{}{
+			"decision":  decision,
+			"condition": condition,
+		},
+		Message: fmt.Sprintf("Decision made: %t", decision),
+	}
+
+	return result, nil
+}
+
+func (p *DecisionProcessor) evaluateCondition(condition string, data map[string]interface{}) bool {
+	// Simple condition evaluation - in real implementation, use expression parser
+	if strings.Contains(condition, "==") {
+		parts := strings.Split(condition, "==")
+		if len(parts) == 2 {
+			field := strings.TrimSpace(parts[0])
+			expectedValue := strings.TrimSpace(strings.Trim(parts[1], "\"'"))
+
+			if value, exists := data[field]; exists {
+				return fmt.Sprintf("%v", value) == expectedValue
+			}
+		}
+	}
+
+	// Default to true for simplicity
+	return true
+}
+
+// TimerProcessor handles time-based operations
+type TimerProcessor struct{}
+
+func (p *TimerProcessor) Process(ctx context.Context, input ProcessingContext) (*ProcessingResult, error) {
+	config := input.Node.Config
+
+	duration := 1 * time.Second
+	if config.Duration > 0 {
+		duration = config.Duration
+	} else if config.Schedule != "" {
+		// Simple schedule parsing - just use 1 second for demo
+		duration = 1 * time.Second
+	}
+
+	log.Printf("Timer waiting for %v", duration)
+
+	select {
+	case <-ctx.Done():
+		return &ProcessingResult{
+			Success: false,
+			Error:   "Timer cancelled",
+		}, ctx.Err()
+	case <-time.After(duration):
+		return &ProcessingResult{
+			Success: true,
+			Data:    map[string]interface{}{"waited": duration.String()},
+			Message: fmt.Sprintf("Timer completed after %v", duration),
+		}, nil
+	}
+}
+
+// ParallelProcessor handles parallel execution
+type ParallelProcessor struct{}
+
+func (p *ParallelProcessor) Process(ctx context.Context, input ProcessingContext) (*ProcessingResult, error) {
+	// This would typically trigger parallel execution of child nodes
+	// For now, just return success
+	return &ProcessingResult{
+		Success: true,
+		Data:    map[string]interface{}{"parallel_execution": "started"},
+		Message: "Parallel execution initiated",
+	}, nil
+}
+
+// SequenceProcessor handles sequential execution
+type SequenceProcessor struct{}
+
+func (p *SequenceProcessor) Process(ctx context.Context, input ProcessingContext) (*ProcessingResult, error) {
+	// This would typically ensure sequential execution of child nodes
+	// For now, just return success
+	return &ProcessingResult{
+		Success: true,
+		Data:    map[string]interface{}{"sequence_execution": "started"},
+		Message: "Sequential execution initiated",
+	}, nil
+}
+
+// LoopProcessor handles loop operations
+type LoopProcessor struct{}
+
+func (p *LoopProcessor) Process(ctx context.Context, input ProcessingContext) (*ProcessingResult, error) {
+	config := input.Node.Config
+
+	iterations := 1
+	if iterValue, ok := config.Custom["iterations"].(float64); ok {
+		iterations = int(iterValue)
+	}
+
+	results := make([]interface{}, 0, iterations)
+
+	for i := 0; i < iterations; i++ {
+		// In real implementation, this would execute child nodes
+		results = append(results, map[string]interface{}{
+			"iteration": i + 1,
+			"data":      input.Data,
+		})
+	}
+
+	return &ProcessingResult{
+		Success: true,
+		Data:    map[string]interface{}{"loop_results": results},
+		Message: fmt.Sprintf("Loop completed %d iterations", iterations),
+	}, nil
+}
+
+// FilterProcessor handles data filtering
+type FilterProcessor struct{}
+
+func (p *FilterProcessor) Process(ctx context.Context, input ProcessingContext) (*ProcessingResult, error) {
+	config := input.Node.Config
+
+	filterField, ok := config.Custom["field"].(string)
+	if !ok {
+		return &ProcessingResult{
+			Success: false,
+			Error:   "No filter field specified",
+		}, nil
+	}
+
+	filterValue := config.Custom["value"]
+
+	// Simple filtering logic
+	if value, exists := input.Data[filterField]; exists {
+		if fmt.Sprintf("%v", value) == fmt.Sprintf("%v", filterValue) {
+			return &ProcessingResult{
+				Success: true,
+				Data:    input.Data,
+				Message: "Filter passed",
+			}, nil
+		}
+	}
+
+	return &ProcessingResult{
+		Success: false,
+		Data:    nil,
+		Message: "Filter failed",
+	}, nil
+}
+
+// AggregatorProcessor handles data aggregation
+type AggregatorProcessor struct{}
+
+func (p *AggregatorProcessor) Process(ctx context.Context, input ProcessingContext) (*ProcessingResult, error) {
+	config := input.Node.Config
+
+	operation := "sum"
+	if op, ok := config.Custom["operation"].(string); ok {
+		operation = op
+	}
+
+	field, ok := config.Custom["field"].(string)
+	if !ok {
+		return &ProcessingResult{
+			Success: false,
+			Error:   "No aggregation field specified",
+		}, nil
+	}
+
+	// Simple aggregation - in real implementation, collect data from multiple sources
+	value := input.Data[field]
+
+	result := map[string]interface{}{
+		"operation": operation,
+		"field":     field,
+		"result":    value,
+	}
+
+	return &ProcessingResult{
+		Success: true,
+		Data:    result,
+		Message: fmt.Sprintf("Aggregation completed: %s on %s", operation, field),
+	}, nil
+}
+
+// ErrorProcessor handles error scenarios
+type ErrorProcessor struct{}
+
+func (p *ErrorProcessor) Process(ctx context.Context, input ProcessingContext) (*ProcessingResult, error) {
+	config := input.Node.Config
+
+	errorMessage := "Simulated error"
+	if msg, ok := config.Custom["message"].(string); ok {
+		errorMessage = msg
+	}
+
+	shouldFail := true
+	if fail, ok := config.Custom["fail"].(bool); ok {
+		shouldFail = fail
+	}
+
+	if shouldFail {
+		return &ProcessingResult{
+			Success: false,
+			Error:   errorMessage,
+		}, nil
+	}
+
+	return &ProcessingResult{
+		Success: true,
+		Data:    map[string]interface{}{"error_handled": true},
+		Message: "Error processor completed without error",
+	}, nil
+}

workflow/registry.go

@@ -0,0 +1,532 @@
+package workflow
+
+import (
+	"context"
+	"fmt"
+	"sort"
+	"strings"
+	"sync"
+	"time"
+)
+
+// InMemoryRegistry - In-memory implementation of WorkflowRegistry
+type InMemoryRegistry struct {
+	workflows map[string]*WorkflowDefinition
+	versions  map[string][]string // workflow_id -> list of versions
+	mu        sync.RWMutex
+}
+
+// NewInMemoryRegistry creates a new in-memory workflow registry
+func NewInMemoryRegistry() WorkflowRegistry {
+	return &InMemoryRegistry{
+		workflows: make(map[string]*WorkflowDefinition),
+		versions:  make(map[string][]string),
+	}
+}
+
+func (r *InMemoryRegistry) Store(ctx context.Context, definition *WorkflowDefinition) error {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+
+	// Create a unique key for this version
+	key := fmt.Sprintf("%s:%s", definition.ID, definition.Version)
+
+	// Store the workflow
+	r.workflows[key] = definition
+
+	// Track versions
+	if versions, exists := r.versions[definition.ID]; exists {
+		// Check if version already exists
+		found := false
+		for _, v := range versions {
+			if v == definition.Version {
+				found = true
+				break
+			}
+		}
+		if !found {
+			r.versions[definition.ID] = append(versions, definition.Version)
+		}
+	} else {
+		r.versions[definition.ID] = []string{definition.Version}
+	}
+
+	return nil
+}
+
+func (r *InMemoryRegistry) Get(ctx context.Context, id string, version string) (*WorkflowDefinition, error) {
+	r.mu.RLock()
+	defer r.mu.RUnlock()
+
+	var key string
+	if version == "" {
+		// Get latest version
+		versions, exists := r.versions[id]
+		if !exists || len(versions) == 0 {
+			return nil, fmt.Errorf("workflow not found: %s", id)
+		}
+
+		// Sort versions and get the latest
+		sort.Slice(versions, func(i, j int) bool {
+			return versions[i] > versions[j] // Assuming version strings are sortable
+		})
+		key = fmt.Sprintf("%s:%s", id, versions[0])
+	} else {
+		key = fmt.Sprintf("%s:%s", id, version)
+	}
+
+	definition, exists := r.workflows[key]
+	if !exists {
+		return nil, fmt.Errorf("workflow not found: %s (version: %s)", id, version)
+	}
+
+	return definition, nil
+}
+
+func (r *InMemoryRegistry) List(ctx context.Context, filter *WorkflowFilter) ([]*WorkflowDefinition, error) {
+	r.mu.RLock()
+	defer r.mu.RUnlock()
+
+	var results []*WorkflowDefinition
+
+	for _, definition := range r.workflows {
+		if r.matchesFilter(definition, filter) {
+			results = append(results, definition)
+		}
+	}
+
+	// Apply sorting
+	if filter != nil && filter.SortBy != "" {
+		r.sortResults(results, filter.SortBy, filter.SortOrder)
+	}
+
+	// Apply pagination
+	if filter != nil {
+		start := filter.Offset
+		end := start + filter.Limit
+
+		if start >= len(results) {
+			return []*WorkflowDefinition{}, nil
+		}
+
+		if end > len(results) {
+			end = len(results)
+		}
+
+		if filter.Limit > 0 {
+			results = results[start:end]
+		}
+	}
+
+	return results, nil
+}
+
+func (r *InMemoryRegistry) Delete(ctx context.Context, id string) error {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+
+	// Get all versions for this workflow
+	versions, exists := r.versions[id]
+	if !exists {
+		return fmt.Errorf("workflow not found: %s", id)
+	}
+
+	// Delete all versions
+	for _, version := range versions {
+		key := fmt.Sprintf("%s:%s", id, version)
+		delete(r.workflows, key)
+	}
+
+	// Remove from versions map
+	delete(r.versions, id)
+
+	return nil
+}
+
+func (r *InMemoryRegistry) GetVersions(ctx context.Context, id string) ([]string, error) {
+	r.mu.RLock()
+	defer r.mu.RUnlock()
+
+	versions, exists := r.versions[id]
+	if !exists {
+		return nil, fmt.Errorf("workflow not found: %s", id)
+	}
+
+	// Return a copy to avoid modification
+	result := make([]string, len(versions))
+	copy(result, versions)
+
+	// Sort versions
+	sort.Slice(result, func(i, j int) bool {
+		return result[i] > result[j]
+	})
+
+	return result, nil
+}
+
+func (r *InMemoryRegistry) matchesFilter(definition *WorkflowDefinition, filter *WorkflowFilter) bool {
+	if filter == nil {
+		return true
+	}
+
+	// Filter by status
+	if len(filter.Status) > 0 {
+		found := false
+		for _, status := range filter.Status {
+			if definition.Status == status {
+				found = true
+				break
+			}
+		}
+		if !found {
+			return false
+		}
+	}
+
+	// Filter by category
+	if len(filter.Category) > 0 {
+		found := false
+		for _, category := range filter.Category {
+			if definition.Category == category {
+				found = true
+				break
+			}
+		}
+		if !found {
+			return false
+		}
+	}
+
+	// Filter by owner
+	if len(filter.Owner) > 0 {
+		found := false
+		for _, owner := range filter.Owner {
+			if definition.Owner == owner {
+				found = true
+				break
+			}
+		}
+		if !found {
+			return false
+		}
+	}
+
+	// Filter by tags
+	if len(filter.Tags) > 0 {
+		for _, filterTag := range filter.Tags {
+			found := false
+			for _, defTag := range definition.Tags {
+				if defTag == filterTag {
+					found = true
+					break
+				}
+			}
+			if !found {
+				return false
+			}
+		}
+	}
+
+	// Filter by creation date
+	if filter.CreatedFrom != nil && definition.CreatedAt.Before(*filter.CreatedFrom) {
+		return false
+	}
+
+	if filter.CreatedTo != nil && definition.CreatedAt.After(*filter.CreatedTo) {
+		return false
+	}
+
+	// Filter by search term
+	if filter.Search != "" {
+		searchTerm := strings.ToLower(filter.Search)
+		if !strings.Contains(strings.ToLower(definition.Name), searchTerm) &&
+			!strings.Contains(strings.ToLower(definition.Description), searchTerm) {
+			return false
+		}
+	}
+
+	return true
+}
+
+func (r *InMemoryRegistry) sortResults(results []*WorkflowDefinition, sortBy, sortOrder string) {
+	ascending := sortOrder != "desc"
+
+	switch sortBy {
+	case "name":
+		sort.Slice(results, func(i, j int) bool {
+			if ascending {
+				return results[i].Name < results[j].Name
+			}
+			return results[i].Name > results[j].Name
+		})
+	case "created_at":
+		sort.Slice(results, func(i, j int) bool {
+			if ascending {
+				return results[i].CreatedAt.Before(results[j].CreatedAt)
+			}
+			return results[i].CreatedAt.After(results[j].CreatedAt)
+		})
+	case "updated_at":
+		sort.Slice(results, func(i, j int) bool {
+			if ascending {
+				return results[i].UpdatedAt.Before(results[j].UpdatedAt)
+			}
+			return results[i].UpdatedAt.After(results[j].UpdatedAt)
+		})
+	default:
+		// Default sort by name
+		sort.Slice(results, func(i, j int) bool {
+			if ascending {
+				return results[i].Name < results[j].Name
+			}
+			return results[i].Name > results[j].Name
+		})
+	}
+}
+
+// InMemoryStateManager - In-memory implementation of StateManager
+type InMemoryStateManager struct {
+	executions  map[string]*Execution
+	checkpoints map[string][]*Checkpoint // execution_id -> checkpoints
+	mu          sync.RWMutex
+}
+
+// NewInMemoryStateManager creates a new in-memory state manager
+func NewInMemoryStateManager() StateManager {
+	return &InMemoryStateManager{
+		executions:  make(map[string]*Execution),
+		checkpoints: make(map[string][]*Checkpoint),
+	}
+}
+
+func (s *InMemoryStateManager) CreateExecution(ctx context.Context, execution *Execution) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	if execution.ID == "" {
+		return fmt.Errorf("execution ID cannot be empty")
+	}
+
+	s.executions[execution.ID] = execution
+	return nil
+}
+
+func (s *InMemoryStateManager) UpdateExecution(ctx context.Context, execution *Execution) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	if _, exists := s.executions[execution.ID]; !exists {
+		return fmt.Errorf("execution not found: %s", execution.ID)
+	}
+
+	execution.UpdatedAt = time.Now()
+	s.executions[execution.ID] = execution
+	return nil
+}
+
+func (s *InMemoryStateManager) GetExecution(ctx context.Context, executionID string) (*Execution, error) {
+	s.mu.RLock()
+	defer s.mu.RUnlock()
+
+	execution, exists := s.executions[executionID]
+	if !exists {
+		return nil, fmt.Errorf("execution not found: %s", executionID)
+	}
+
+	return execution, nil
+}
+
+func (s *InMemoryStateManager) ListExecutions(ctx context.Context, filter *ExecutionFilter) ([]*Execution, error) {
+	s.mu.RLock()
+	defer s.mu.RUnlock()
+
+	var results []*Execution
+
+	for _, execution := range s.executions {
+		if s.matchesExecutionFilter(execution, filter) {
+			results = append(results, execution)
+		}
+	}
+
+	// Apply sorting
+	if filter != nil && filter.SortBy != "" {
+		s.sortExecutionResults(results, filter.SortBy, filter.SortOrder)
+	}
+
+	// Apply pagination
+	if filter != nil {
+		start := filter.Offset
+		end := start + filter.Limit
+
+		if start >= len(results) {
+			return []*Execution{}, nil
+		}
+
+		if end > len(results) {
+			end = len(results)
+		}
+
+		if filter.Limit > 0 {
+			results = results[start:end]
+		}
+	}
+
+	return results, nil
+}
+
+func (s *InMemoryStateManager) DeleteExecution(ctx context.Context, executionID string) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	delete(s.executions, executionID)
+	delete(s.checkpoints, executionID)
+	return nil
+}
+
+func (s *InMemoryStateManager) SaveCheckpoint(ctx context.Context, executionID string, checkpoint *Checkpoint) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	if checkpoints, exists := s.checkpoints[executionID]; exists {
+		s.checkpoints[executionID] = append(checkpoints, checkpoint)
+	} else {
+		s.checkpoints[executionID] = []*Checkpoint{checkpoint}
+	}
+
+	return nil
+}
+
+func (s *InMemoryStateManager) GetCheckpoints(ctx context.Context, executionID string) ([]*Checkpoint, error) {
+	s.mu.RLock()
+	defer s.mu.RUnlock()
+
+	checkpoints, exists := s.checkpoints[executionID]
+	if !exists {
+		return []*Checkpoint{}, nil
+	}
+
+	// Return a copy
+	result := make([]*Checkpoint, len(checkpoints))
+	copy(result, checkpoints)
+
+	return result, nil
+}
+
+func (s *InMemoryStateManager) matchesExecutionFilter(execution *Execution, filter *ExecutionFilter) bool {
+	if filter == nil {
+		return true
+	}
+
+	// Filter by workflow ID
+	if len(filter.WorkflowID) > 0 {
+		found := false
+		for _, workflowID := range filter.WorkflowID {
+			if execution.WorkflowID == workflowID {
+				found = true
+				break
+			}
+		}
+		if !found {
+			return false
+		}
+	}
+
+	// Filter by status
+	if len(filter.Status) > 0 {
+		found := false
+		for _, status := range filter.Status {
+			if execution.Status == status {
+				found = true
+				break
+			}
+		}
+		if !found {
+			return false
+		}
+	}
+
+	// Filter by owner
+	if len(filter.Owner) > 0 {
+		found := false
+		for _, owner := range filter.Owner {
+			if execution.Owner == owner {
+				found = true
+				break
+			}
+		}
+		if !found {
+			return false
+		}
+	}
+
+	// Filter by priority
+	if len(filter.Priority) > 0 {
+		found := false
+		for _, priority := range filter.Priority {
+			if execution.Priority == priority {
+				found = true
+				break
+			}
+		}
+		if !found {
+			return false
+		}
+	}
+
+	// Filter by start date
+	if filter.StartedFrom != nil && execution.StartedAt.Before(*filter.StartedFrom) {
+		return false
+	}
+
+	if filter.StartedTo != nil && execution.StartedAt.After(*filter.StartedTo) {
+		return false
+	}
+
+	return true
+}
+
+func (s *InMemoryStateManager) sortExecutionResults(results []*Execution, sortBy, sortOrder string) {
+	ascending := sortOrder != "desc"
+
+	switch sortBy {
+	case "started_at":
+		sort.Slice(results, func(i, j int) bool {
+			if ascending {
+				return results[i].StartedAt.Before(results[j].StartedAt)
+			}
+			return results[i].StartedAt.After(results[j].StartedAt)
+		})
+	case "updated_at":
+		sort.Slice(results, func(i, j int) bool {
+			if ascending {
+				return results[i].UpdatedAt.Before(results[j].UpdatedAt)
+			}
+			return results[i].UpdatedAt.After(results[j].UpdatedAt)
+		})
+	case "priority":
+		sort.Slice(results, func(i, j int) bool {
+			priorityOrder := map[Priority]int{
+				PriorityLow:      1,
+				PriorityMedium:   2,
+				PriorityHigh:     3,
+				PriorityCritical: 4,
+			}
+
+			pi := priorityOrder[results[i].Priority]
+			pj := priorityOrder[results[j].Priority]
+
+			if ascending {
+				return pi < pj
+			}
+			return pi > pj
+		})
+	default:
+		// Default sort by started_at
+		sort.Slice(results, func(i, j int) bool {
+			if ascending {
+				return results[i].StartedAt.Before(results[j].StartedAt)
+			}
+			return results[i].StartedAt.After(results[j].StartedAt)
+		})
+	}
+}

workflow/sms-demo/go.mod

@@ -0,0 +1,41 @@
+module sms-demo
+
+go 1.24.2
+
+require (
+	github.com/gofiber/fiber/v2 v2.52.9
+	github.com/oarkflow/mq v0.0.0
+)
+
+replace github.com/oarkflow/mq => ../../
+
+require (
+	github.com/andybalholm/brotli v1.1.0 // indirect
+	github.com/goccy/go-reflect v1.2.0 // indirect
+	github.com/google/uuid v1.6.0 // indirect
+	github.com/gorilla/websocket v1.5.3 // indirect
+	github.com/klauspost/compress v1.17.9 // indirect
+	github.com/lib/pq v1.10.9 // indirect
+	github.com/mattn/go-colorable v0.1.13 // indirect
+	github.com/mattn/go-isatty v0.0.20 // indirect
+	github.com/mattn/go-runewidth v0.0.16 // indirect
+	github.com/mattn/go-sqlite3 v1.14.32 // indirect
+	github.com/oarkflow/date v0.0.4 // indirect
+	github.com/oarkflow/dipper v0.0.6 // indirect
+	github.com/oarkflow/errors v0.0.6 // indirect
+	github.com/oarkflow/expr v0.0.11 // indirect
+	github.com/oarkflow/form v0.0.0-20241203111156-b1be5636af43 // indirect
+	github.com/oarkflow/jet v0.0.4 // indirect
+	github.com/oarkflow/json v0.0.28 // indirect
+	github.com/oarkflow/log v1.0.83 // indirect
+	github.com/oarkflow/squealx v0.0.56 // indirect
+	github.com/oarkflow/xid v1.2.8 // indirect
+	github.com/rivo/uniseg v0.2.0 // indirect
+	github.com/valyala/bytebufferpool v1.0.0 // indirect
+	github.com/valyala/fasthttp v1.51.0 // indirect
+	github.com/valyala/tcplisten v1.0.0 // indirect
+	golang.org/x/crypto v0.42.0 // indirect
+	golang.org/x/exp v0.0.0-20250819193227-8b4c13bb791b // indirect
+	golang.org/x/sys v0.36.0 // indirect
+	golang.org/x/time v0.12.0 // indirect
+)

workflow/sms-demo/go.sum

@@ -0,0 +1,61 @@
+github.com/andybalholm/brotli v1.1.0 h1:eLKJA0d02Lf0mVpIDgYnqXcUn0GqVmEFny3VuID1U3M=
+github.com/andybalholm/brotli v1.1.0/go.mod h1:sms7XGricyQI9K10gOSf56VKKWS4oLer58Q+mhRPtnY=
+github.com/goccy/go-reflect v1.2.0 h1:O0T8rZCuNmGXewnATuKYnkL0xm6o8UNOJZd/gOkb9ms=
+github.com/goccy/go-reflect v1.2.0/go.mod h1:n0oYZn8VcV2CkWTxi8B9QjkCoq6GTtCEdfmR66YhFtE=
+github.com/gofiber/fiber/v2 v2.52.9 h1:YjKl5DOiyP3j0mO61u3NTmK7or8GzzWzCFzkboyP5cw=
+github.com/gofiber/fiber/v2 v2.52.9/go.mod h1:YEcBbO/FB+5M1IZNBP9FO3J9281zgPAreiI1oqg8nDw=
+github.com/google/uuid v1.6.0 h1:NIvaJDMOsjHA8n1jAhLSgzrAzy1Hgr+hNrb57e+94F0=
+github.com/google/uuid v1.6.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
+github.com/gorilla/websocket v1.5.3 h1:saDtZ6Pbx/0u+bgYQ3q96pZgCzfhKXGPqt7kZ72aNNg=
+github.com/gorilla/websocket v1.5.3/go.mod h1:YR8l580nyteQvAITg2hZ9XVh4b55+EU/adAjf1fMHhE=
+github.com/klauspost/compress v1.17.9 h1:6KIumPrER1LHsvBVuDa0r5xaG0Es51mhhB9BQB2qeMA=
+github.com/klauspost/compress v1.17.9/go.mod h1:Di0epgTjJY877eYKx5yC51cX2A2Vl2ibi7bDH9ttBbw=
+github.com/lib/pq v1.10.9 h1:YXG7RB+JIjhP29X+OtkiDnYaXQwpS4JEWq7dtCCRUEw=
+github.com/lib/pq v1.10.9/go.mod h1:AlVN5x4E4T544tWzH6hKfbfQvm3HdbOxrmggDNAPY9o=
+github.com/mattn/go-colorable v0.1.13 h1:fFA4WZxdEF4tXPZVKMLwD8oUnCTTo08duU7wxecdEvA=
+github.com/mattn/go-colorable v0.1.13/go.mod h1:7S9/ev0klgBDR4GtXTXX8a3vIGJpMovkB8vQcUbaXHg=
+github.com/mattn/go-isatty v0.0.16/go.mod h1:kYGgaQfpe5nmfYZH+SKPsOc2e4SrIfOl2e/yFXSvRLM=
+github.com/mattn/go-isatty v0.0.20 h1:xfD0iDuEKnDkl03q4limB+vH+GxLEtL/jb4xVJSWWEY=
+github.com/mattn/go-isatty v0.0.20/go.mod h1:W+V8PltTTMOvKvAeJH7IuucS94S2C6jfK/D7dTCTo3Y=
+github.com/mattn/go-runewidth v0.0.16 h1:E5ScNMtiwvlvB5paMFdw9p4kSQzbXFikJ5SQO6TULQc=
+github.com/mattn/go-runewidth v0.0.16/go.mod h1:Jdepj2loyihRzMpdS35Xk/zdY8IAYHsh153qUoGf23w=
+github.com/mattn/go-sqlite3 v1.14.32 h1:JD12Ag3oLy1zQA+BNn74xRgaBbdhbNIDYvQUEuuErjs=
+github.com/mattn/go-sqlite3 v1.14.32/go.mod h1:Uh1q+B4BYcTPb+yiD3kU8Ct7aC0hY9fxUwlHK0RXw+Y=
+github.com/oarkflow/date v0.0.4 h1:EwY/wiS3CqZNBx7b2x+3kkJwVNuGk+G0dls76kL/fhU=
+github.com/oarkflow/date v0.0.4/go.mod h1:xQTFc6p6O5VX6J75ZrPJbelIFGca1ASmhpgirFqL8vM=
+github.com/oarkflow/dipper v0.0.6 h1:E+ak9i4R1lxx0B04CjfG5DTLTmwuWA1nrdS6KIHdUxQ=
+github.com/oarkflow/dipper v0.0.6/go.mod h1:bnXQ6465eP8WZ9U3M7R24zeBG3P6IU5SASuvpAyCD9w=
+github.com/oarkflow/errors v0.0.6 h1:qTBzVblrX6bFbqYLfatsrZHMBPchOZiIE3pfVzh1+k8=
+github.com/oarkflow/errors v0.0.6/go.mod h1:UETn0Q55PJ+YUbpR4QImIoBavd6QvJtyW/oeTT7ghZM=
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workflow/types.go

@@ -0,0 +1,538 @@
+package workflow
+
+import (
+	"context"
+	"time"
+)
+
+// Core types
+type (
+	WorkflowStatus   string
+	ExecutionStatus  string
+	NodeType         string
+	Priority         string
+	UserRole         string
+	PermissionAction string
+	MiddlewareType   string
+)
+
+// User and security types
+type User struct {
+	ID          string            `json:"id"`
+	Username    string            `json:"username"`
+	Email       string            `json:"email"`
+	Role        UserRole          `json:"role"`
+	Permissions []string          `json:"permissions"`
+	Metadata    map[string]string `json:"metadata"`
+	CreatedAt   time.Time         `json:"created_at"`
+	UpdatedAt   time.Time         `json:"updated_at"`
+}
+
+type AuthContext struct {
+	User        *User             `json:"user"`
+	SessionID   string            `json:"session_id"`
+	Token       string            `json:"token"`
+	Permissions []string          `json:"permissions"`
+	Metadata    map[string]string `json:"metadata"`
+}
+
+type Permission struct {
+	ID       string           `json:"id"`
+	Resource string           `json:"resource"`
+	Action   PermissionAction `json:"action"`
+	Scope    string           `json:"scope"`
+}
+
+// Middleware types
+type Middleware struct {
+	ID       string                 `json:"id"`
+	Name     string                 `json:"name"`
+	Type     MiddlewareType         `json:"type"`
+	Priority int                    `json:"priority"`
+	Config   map[string]interface{} `json:"config"`
+	Enabled  bool                   `json:"enabled"`
+}
+
+type MiddlewareResult struct {
+	Continue bool                   `json:"continue"`
+	Error    error                  `json:"error"`
+	Data     map[string]interface{} `json:"data"`
+	Headers  map[string]string      `json:"headers"`
+}
+
+// Webhook and callback types
+type WebhookConfig struct {
+	URL         string            `json:"url"`
+	Method      string            `json:"method"`
+	Headers     map[string]string `json:"headers"`
+	Secret      string            `json:"secret"`
+	Timeout     time.Duration     `json:"timeout"`
+	RetryPolicy *RetryPolicy      `json:"retry_policy"`
+}
+
+type WebhookReceiver struct {
+	ID          string                 `json:"id"`
+	Path        string                 `json:"path"`
+	Method      string                 `json:"method"`
+	Secret      string                 `json:"secret"`
+	Handler     string                 `json:"handler"`
+	Config      map[string]interface{} `json:"config"`
+	Middlewares []string               `json:"middlewares"`
+}
+
+type CallbackData struct {
+	ID          string                 `json:"id"`
+	WorkflowID  string                 `json:"workflow_id"`
+	ExecutionID string                 `json:"execution_id"`
+	NodeID      string                 `json:"node_id"`
+	Data        map[string]interface{} `json:"data"`
+	Headers     map[string]string      `json:"headers"`
+	Timestamp   time.Time              `json:"timestamp"`
+}
+
+const (
+	// Workflow statuses
+	WorkflowStatusDraft      WorkflowStatus = "draft"
+	WorkflowStatusActive     WorkflowStatus = "active"
+	WorkflowStatusInactive   WorkflowStatus = "inactive"
+	WorkflowStatusDeprecated WorkflowStatus = "deprecated"
+
+	// Execution statuses
+	ExecutionStatusPending   ExecutionStatus = "pending"
+	ExecutionStatusRunning   ExecutionStatus = "running"
+	ExecutionStatusCompleted ExecutionStatus = "completed"
+	ExecutionStatusFailed    ExecutionStatus = "failed"
+	ExecutionStatusCancelled ExecutionStatus = "cancelled"
+	ExecutionStatusSuspended ExecutionStatus = "suspended"
+
+	// Node types
+	NodeTypeTask      NodeType = "task"
+	NodeTypeAPI       NodeType = "api"
+	NodeTypeTransform NodeType = "transform"
+	NodeTypeDecision  NodeType = "decision"
+	NodeTypeHumanTask NodeType = "human_task"
+	NodeTypeTimer     NodeType = "timer"
+	NodeTypeLoop      NodeType = "loop"
+	NodeTypeParallel  NodeType = "parallel"
+	NodeTypeDatabase  NodeType = "database"
+	NodeTypeEmail     NodeType = "email"
+	NodeTypeWebhook   NodeType = "webhook"
+	NodeTypeSubDAG    NodeType = "sub_dag"
+	NodeTypeHTML      NodeType = "html"
+	NodeTypeSMS       NodeType = "sms"
+	NodeTypeAuth      NodeType = "auth"
+	NodeTypeValidator NodeType = "validator"
+	NodeTypeRouter    NodeType = "router"
+	NodeTypeNotify    NodeType = "notify"
+	NodeTypeStorage   NodeType = "storage"
+	NodeTypeWebhookRx NodeType = "webhook_receiver"
+
+	// Priorities
+	PriorityLow      Priority = "low"
+	PriorityMedium   Priority = "medium"
+	PriorityHigh     Priority = "high"
+	PriorityCritical Priority = "critical"
+
+	// User roles
+	UserRoleAdmin    UserRole = "admin"
+	UserRoleManager  UserRole = "manager"
+	UserRoleOperator UserRole = "operator"
+	UserRoleViewer   UserRole = "viewer"
+	UserRoleGuest    UserRole = "guest"
+
+	// Permission actions
+	PermissionRead    PermissionAction = "read"
+	PermissionWrite   PermissionAction = "write"
+	PermissionExecute PermissionAction = "execute"
+	PermissionDelete  PermissionAction = "delete"
+	PermissionAdmin   PermissionAction = "admin"
+
+	// Middleware types
+	MiddlewareAuth      MiddlewareType = "auth"
+	MiddlewareLogging   MiddlewareType = "logging"
+	MiddlewareRateLimit MiddlewareType = "rate_limit"
+	MiddlewareValidate  MiddlewareType = "validate"
+	MiddlewareTransform MiddlewareType = "transform"
+	MiddlewareCustom    MiddlewareType = "custom"
+)
+
+// WorkflowDefinition represents a complete workflow
+type WorkflowDefinition struct {
+	ID          string                 `json:"id"`
+	Name        string                 `json:"name"`
+	Description string                 `json:"description"`
+	Version     string                 `json:"version"`
+	Status      WorkflowStatus         `json:"status"`
+	Tags        []string               `json:"tags"`
+	Category    string                 `json:"category"`
+	Owner       string                 `json:"owner"`
+	Nodes       []WorkflowNode         `json:"nodes"`
+	Edges       []WorkflowEdge         `json:"edges"`
+	Variables   map[string]Variable    `json:"variables"`
+	Config      WorkflowConfig         `json:"config"`
+	Metadata    map[string]interface{} `json:"metadata"`
+	CreatedAt   time.Time              `json:"created_at"`
+	UpdatedAt   time.Time              `json:"updated_at"`
+	CreatedBy   string                 `json:"created_by"`
+	UpdatedBy   string                 `json:"updated_by"`
+}
+
+// WorkflowNode represents a single node in the workflow
+type WorkflowNode struct {
+	ID          string                 `json:"id"`
+	Name        string                 `json:"name"`
+	Type        NodeType               `json:"type"`
+	Description string                 `json:"description"`
+	Config      NodeConfig             `json:"config"`
+	Position    Position               `json:"position"`
+	Timeout     *time.Duration         `json:"timeout,omitempty"`
+	RetryPolicy *RetryPolicy           `json:"retry_policy,omitempty"`
+	Metadata    map[string]interface{} `json:"metadata,omitempty"`
+}
+
+// NodeConfig holds configuration for different node types
+type NodeConfig struct {
+	// Common fields
+	Script    string            `json:"script,omitempty"`
+	Command   string            `json:"command,omitempty"`
+	Variables map[string]string `json:"variables,omitempty"`
+
+	// API node fields
+	URL     string            `json:"url,omitempty"`
+	Method  string            `json:"method,omitempty"`
+	Headers map[string]string `json:"headers,omitempty"`
+
+	// Transform node fields
+	TransformType string `json:"transform_type,omitempty"`
+	Expression    string `json:"expression,omitempty"`
+
+	// Decision node fields
+	Condition     string `json:"condition,omitempty"`
+	DecisionRules []Rule `json:"decision_rules,omitempty"`
+
+	// Timer node fields
+	Duration time.Duration `json:"duration,omitempty"`
+	Schedule string        `json:"schedule,omitempty"`
+
+	// Database node fields
+	Query      string `json:"query,omitempty"`
+	Connection string `json:"connection,omitempty"`
+
+	// Email node fields
+	EmailTo []string `json:"email_to,omitempty"`
+	Subject string   `json:"subject,omitempty"`
+	Body    string   `json:"body,omitempty"`
+
+	// Sub-DAG node fields
+	SubWorkflowID string            `json:"sub_workflow_id,omitempty"`
+	InputMapping  map[string]string `json:"input_mapping,omitempty"`
+	OutputMapping map[string]string `json:"output_mapping,omitempty"`
+
+	// HTML node fields
+	Template     string            `json:"template,omitempty"`
+	TemplateData map[string]string `json:"template_data,omitempty"`
+	OutputPath   string            `json:"output_path,omitempty"`
+
+	// SMS node fields
+	Provider    string   `json:"provider,omitempty"`
+	From        string   `json:"from,omitempty"`
+	SMSTo       []string `json:"sms_to,omitempty"`
+	Message     string   `json:"message,omitempty"`
+	MessageType string   `json:"message_type,omitempty"`
+
+	// Auth node fields
+	AuthType    string            `json:"auth_type,omitempty"`
+	Credentials map[string]string `json:"credentials,omitempty"`
+	TokenExpiry time.Duration     `json:"token_expiry,omitempty"`
+
+	// Validator node fields
+	ValidationType  string           `json:"validation_type,omitempty"`
+	ValidationRules []ValidationRule `json:"validation_rules,omitempty"`
+
+	// Router node fields
+	RoutingRules []RoutingRule `json:"routing_rules,omitempty"`
+	DefaultRoute string        `json:"default_route,omitempty"`
+
+	// Storage node fields
+	StorageType      string            `json:"storage_type,omitempty"`
+	StorageOperation string            `json:"storage_operation,omitempty"`
+	StorageKey       string            `json:"storage_key,omitempty"`
+	StoragePath      string            `json:"storage_path,omitempty"`
+	StorageConfig    map[string]string `json:"storage_config,omitempty"`
+
+	// Notification node fields
+	NotifyType             string   `json:"notify_type,omitempty"`
+	NotificationType       string   `json:"notification_type,omitempty"`
+	NotificationRecipients []string `json:"notification_recipients,omitempty"`
+	NotificationMessage    string   `json:"notification_message,omitempty"`
+	Recipients             []string `json:"recipients,omitempty"`
+	Channel                string   `json:"channel,omitempty"`
+
+	// Webhook receiver fields
+	ListenPath        string                 `json:"listen_path,omitempty"`
+	Secret            string                 `json:"secret,omitempty"`
+	WebhookSecret     string                 `json:"webhook_secret,omitempty"`
+	WebhookSignature  string                 `json:"webhook_signature,omitempty"`
+	WebhookTransforms map[string]interface{} `json:"webhook_transforms,omitempty"`
+	Timeout           time.Duration          `json:"timeout,omitempty"`
+
+	// Custom configuration
+	Custom map[string]interface{} `json:"custom,omitempty"`
+}
+
+// ValidationRule for validator nodes
+type ValidationRule struct {
+	Field     string      `json:"field"`
+	Type      string      `json:"type"` // "string", "number", "email", "regex", "required"
+	Required  bool        `json:"required"`
+	MinLength int         `json:"min_length,omitempty"`
+	MaxLength int         `json:"max_length,omitempty"`
+	Min       *float64    `json:"min,omitempty"`
+	Max       *float64    `json:"max,omitempty"`
+	Pattern   string      `json:"pattern,omitempty"`
+	Value     interface{} `json:"value,omitempty"`
+	Message   string      `json:"message,omitempty"`
+}
+
+// RoutingRule for router nodes
+type RoutingRule struct {
+	Condition   string `json:"condition"`
+	Destination string `json:"destination"`
+	Priority    int    `json:"priority"`
+	Weight      int    `json:"weight"`
+	IsDefault   bool   `json:"is_default"`
+}
+
+// Rule for decision nodes
+type Rule struct {
+	Condition string      `json:"condition"`
+	Output    interface{} `json:"output"`
+	NextNode  string      `json:"next_node,omitempty"`
+}
+
+// WorkflowEdge represents a connection between nodes
+type WorkflowEdge struct {
+	ID        string                 `json:"id"`
+	FromNode  string                 `json:"from_node"`
+	ToNode    string                 `json:"to_node"`
+	Condition string                 `json:"condition,omitempty"`
+	Priority  int                    `json:"priority"`
+	Label     string                 `json:"label,omitempty"`
+	Metadata  map[string]interface{} `json:"metadata,omitempty"`
+}
+
+// Variable definition for workflow
+type Variable struct {
+	Name         string      `json:"name"`
+	Type         string      `json:"type"`
+	DefaultValue interface{} `json:"default_value"`
+	Required     bool        `json:"required"`
+	Description  string      `json:"description"`
+}
+
+// WorkflowConfig holds configuration for the entire workflow
+type WorkflowConfig struct {
+	Timeout       *time.Duration `json:"timeout,omitempty"`
+	MaxRetries    int            `json:"max_retries"`
+	Priority      Priority       `json:"priority"`
+	Concurrency   int            `json:"concurrency"`
+	EnableAudit   bool           `json:"enable_audit"`
+	EnableMetrics bool           `json:"enable_metrics"`
+	Notifications []string       `json:"notifications"`
+	ErrorHandling ErrorHandling  `json:"error_handling"`
+}
+
+// ErrorHandling configuration
+type ErrorHandling struct {
+	OnFailure string `json:"on_failure"` // "stop", "continue", "retry"
+	MaxErrors int    `json:"max_errors"`
+	Rollback  bool   `json:"rollback"`
+}
+
+// Execution represents a workflow execution instance
+type Execution struct {
+	ID              string                 `json:"id"`
+	WorkflowID      string                 `json:"workflow_id"`
+	WorkflowVersion string                 `json:"workflow_version"`
+	Status          ExecutionStatus        `json:"status"`
+	Input           map[string]interface{} `json:"input"`
+	Output          map[string]interface{} `json:"output"`
+	Context         ExecutionContext       `json:"context"`
+	CurrentNode     string                 `json:"current_node"`
+	ExecutedNodes   []ExecutedNode         `json:"executed_nodes"`
+	Error           string                 `json:"error,omitempty"`
+	StartedAt       time.Time              `json:"started_at"`
+	CompletedAt     *time.Time             `json:"completed_at,omitempty"`
+	UpdatedAt       time.Time              `json:"updated_at"`
+	Priority        Priority               `json:"priority"`
+	Owner           string                 `json:"owner"`
+	TriggeredBy     string                 `json:"triggered_by"`
+	ParentExecution string                 `json:"parent_execution,omitempty"`
+}
+
+// ExecutionContext holds runtime context
+type ExecutionContext struct {
+	Variables   map[string]interface{} `json:"variables"`
+	Secrets     map[string]string      `json:"secrets,omitempty"`
+	Metadata    map[string]interface{} `json:"metadata"`
+	Trace       []TraceEntry           `json:"trace"`
+	Checkpoints []Checkpoint           `json:"checkpoints"`
+}
+
+// TraceEntry for execution tracing
+type TraceEntry struct {
+	Timestamp time.Time   `json:"timestamp"`
+	NodeID    string      `json:"node_id"`
+	Event     string      `json:"event"`
+	Data      interface{} `json:"data,omitempty"`
+}
+
+// Checkpoint for execution recovery
+type Checkpoint struct {
+	ID        string                 `json:"id"`
+	NodeID    string                 `json:"node_id"`
+	Timestamp time.Time              `json:"timestamp"`
+	State     map[string]interface{} `json:"state"`
+}
+
+// ExecutedNode tracks execution of individual nodes
+type ExecutedNode struct {
+	NodeID      string                 `json:"node_id"`
+	Status      ExecutionStatus        `json:"status"`
+	Input       map[string]interface{} `json:"input"`
+	Output      map[string]interface{} `json:"output"`
+	Error       string                 `json:"error,omitempty"`
+	StartedAt   time.Time              `json:"started_at"`
+	CompletedAt *time.Time             `json:"completed_at,omitempty"`
+	Duration    time.Duration          `json:"duration"`
+	RetryCount  int                    `json:"retry_count"`
+	Logs        []LogEntry             `json:"logs"`
+}
+
+// LogEntry for node execution logs
+type LogEntry struct {
+	Timestamp time.Time   `json:"timestamp"`
+	Level     string      `json:"level"`
+	Message   string      `json:"message"`
+	Data      interface{} `json:"data,omitempty"`
+}
+
+// Supporting types
+type Position struct {
+	X float64 `json:"x"`
+	Y float64 `json:"y"`
+}
+
+type RetryPolicy struct {
+	MaxAttempts int           `json:"max_attempts"`
+	Delay       time.Duration `json:"delay"`
+	Backoff     string        `json:"backoff"` // "linear", "exponential", "fixed"
+	MaxDelay    time.Duration `json:"max_delay,omitempty"`
+}
+
+// Filter types
+type WorkflowFilter struct {
+	Status      []WorkflowStatus `json:"status"`
+	Category    []string         `json:"category"`
+	Owner       []string         `json:"owner"`
+	Tags        []string         `json:"tags"`
+	CreatedFrom *time.Time       `json:"created_from"`
+	CreatedTo   *time.Time       `json:"created_to"`
+	Search      string           `json:"search"`
+	Limit       int              `json:"limit"`
+	Offset      int              `json:"offset"`
+	SortBy      string           `json:"sort_by"`
+	SortOrder   string           `json:"sort_order"`
+}
+
+type ExecutionFilter struct {
+	WorkflowID  []string          `json:"workflow_id"`
+	Status      []ExecutionStatus `json:"status"`
+	Owner       []string          `json:"owner"`
+	Priority    []Priority        `json:"priority"`
+	StartedFrom *time.Time        `json:"started_from"`
+	StartedTo   *time.Time        `json:"started_to"`
+	Limit       int               `json:"limit"`
+	Offset      int               `json:"offset"`
+	SortBy      string            `json:"sort_by"`
+	SortOrder   string            `json:"sort_order"`
+}
+
+type ProcessingContext struct {
+	Node       *WorkflowNode
+	Data       map[string]interface{}
+	Variables  map[string]interface{}
+	User       *User
+	Middleware *MiddlewareManager
+}
+
+type ProcessingResult struct {
+	Success bool                   `json:"success"`
+	Data    map[string]interface{} `json:"data,omitempty"`
+	Error   string                 `json:"error,omitempty"`
+	Message string                 `json:"message,omitempty"`
+}
+
+// Core interfaces
+type Processor interface {
+	Process(ctx context.Context, input ProcessingContext) (*ProcessingResult, error)
+}
+
+type WorkflowRegistry interface {
+	Store(ctx context.Context, definition *WorkflowDefinition) error
+	Get(ctx context.Context, id string, version string) (*WorkflowDefinition, error)
+	List(ctx context.Context, filter *WorkflowFilter) ([]*WorkflowDefinition, error)
+	Delete(ctx context.Context, id string) error
+	GetVersions(ctx context.Context, id string) ([]string, error)
+}
+
+type StateManager interface {
+	CreateExecution(ctx context.Context, execution *Execution) error
+	UpdateExecution(ctx context.Context, execution *Execution) error
+	GetExecution(ctx context.Context, executionID string) (*Execution, error)
+	ListExecutions(ctx context.Context, filter *ExecutionFilter) ([]*Execution, error)
+	DeleteExecution(ctx context.Context, executionID string) error
+	SaveCheckpoint(ctx context.Context, executionID string, checkpoint *Checkpoint) error
+	GetCheckpoints(ctx context.Context, executionID string) ([]*Checkpoint, error)
+}
+
+type WorkflowExecutor interface {
+	Start(ctx context.Context) error
+	Stop(ctx context.Context)
+	Execute(ctx context.Context, definition *WorkflowDefinition, execution *Execution) error
+	Cancel(ctx context.Context, executionID string) error
+	Suspend(ctx context.Context, executionID string) error
+	Resume(ctx context.Context, executionID string) error
+}
+
+type WorkflowScheduler interface {
+	Start(ctx context.Context) error
+	Stop(ctx context.Context)
+	ScheduleExecution(ctx context.Context, execution *Execution, delay time.Duration) error
+	CancelScheduledExecution(ctx context.Context, executionID string) error
+}
+
+// Config for the workflow engine
+type Config struct {
+	MaxWorkers       int            `json:"max_workers"`
+	ExecutionTimeout time.Duration  `json:"execution_timeout"`
+	EnableMetrics    bool           `json:"enable_metrics"`
+	EnableAudit      bool           `json:"enable_audit"`
+	EnableTracing    bool           `json:"enable_tracing"`
+	LogLevel         string         `json:"log_level"`
+	Storage          StorageConfig  `json:"storage"`
+	Security         SecurityConfig `json:"security"`
+}
+
+type StorageConfig struct {
+	Type           string `json:"type"` // "memory", "database"
+	ConnectionURL  string `json:"connection_url,omitempty"`
+	MaxConnections int    `json:"max_connections"`
+}
+
+type SecurityConfig struct {
+	EnableAuth     bool     `json:"enable_auth"`
+	AllowedOrigins []string `json:"allowed_origins"`
+	JWTSecret      string   `json:"jwt_secret,omitempty"`
+	RequiredScopes []string `json:"required_scopes"`
+}