[FSSDK-11169] Implement Decision Service methods to handle CMAB

pkg/decision/composite_experiment_service.go

@@ -1,5 +1,5 @@
 /****************************************************************************
- * Copyright 2019-2020, Optimizely, Inc. and contributors                   *
+ * Copyright 2019-2025, Optimizely, Inc. and contributors                   *
  *                                                                          *
  * Licensed under the Apache License, Version 2.0 (the "License");          *
  * you may not use this file except in compliance with the License.         *
@@ -40,11 +40,19 @@ func WithOverrideStore(overrideStore ExperimentOverrideStore) CESOptionFunc {
 	}
 }
 
+// WithCmabService adds a CMAB service
+func WithCmabService(cmabService CmabService) CESOptionFunc {
+	return func(f *CompositeExperimentService) {
+		f.cmabService = cmabService
+	}
+}
+
 // CompositeExperimentService bridges together the various experiment decision services that ship by default with the SDK
 type CompositeExperimentService struct {
 	experimentServices []ExperimentService
 	overrideStore      ExperimentOverrideStore
 	userProfileService UserProfileService
+	cmabService        CmabService
 	logger             logging.OptimizelyLogProducer
 }
 
@@ -53,7 +61,8 @@ func NewCompositeExperimentService(sdkKey string, options ...CESOptionFunc) *Com
 	// These decision services are applied in order:
 	// 1. Overrides (if supplied)
 	// 2. Whitelist
-	// 3. Bucketing (with User profile integration if supplied)
+	// 3. CMAB (if experiment is a CMAB experiment)
+	// 4. Bucketing (with User profile integration if supplied)
 	compositeExperimentService := &CompositeExperimentService{logger: logging.GetLogger(sdkKey, "CompositeExperimentService")}
 	for _, opt := range options {
 		opt(compositeExperimentService)
@@ -68,6 +77,12 @@ func NewCompositeExperimentService(sdkKey string, options ...CESOptionFunc) *Com
 		experimentServices = append([]ExperimentService{overrideService}, experimentServices...)
 	}
 
+	// Add CMAB service if available
+	if compositeExperimentService.cmabService != nil {
+		cmabService := NewExperimentCmabService(compositeExperimentService.cmabService, logging.GetLogger(sdkKey, "ExperimentCmabService"))
+		experimentServices = append(experimentServices, cmabService)
+	}
+
 	experimentBucketerService := NewExperimentBucketerService(logging.GetLogger(sdkKey, "ExperimentBucketerService"))
 	if compositeExperimentService.userProfileService != nil {
 		persistingExperimentService := NewPersistingExperimentService(compositeExperimentService.userProfileService, experimentBucketerService, logging.GetLogger(sdkKey, "PersistingExperimentService"))

pkg/decision/entities.go

@@ -1,5 +1,5 @@
 /****************************************************************************
- * Copyright 2019-2021, Optimizely, Inc. and contributors                   *
+ * Copyright 2019-2025, Optimizely, Inc. and contributors                   *
  *                                                                          *
  * Licensed under the Apache License, Version 2.0 (the "License");          *
  * you may not use this file except in compliance with the License.         *
@@ -55,6 +55,8 @@ const (
 	Rollout Source = "rollout"
 	// FeatureTest - the decision came from a feature test
 	FeatureTest Source = "feature-test"
+	// Cmab - the decision came from a CMAB service
+	Cmab Source = "cmab"
 )
 
 // Decision contains base information about a decision

pkg/decision/experiment_cmab_service.go

@@ -0,0 +1,97 @@
+/****************************************************************************
+ * Copyright 2025, Optimizely, Inc. and contributors                        *
+ *                                                                          *
+ * Licensed under the Apache License, Version 2.0 (the "License");          *
+ * you may not use this file except in compliance with the License.         *
+ * You may obtain a copy of the License at                                  *
+ *                                                                          *
+ *    http://www.apache.org/licenses/LICENSE-2.0                            *
+ *                                                                          *
+ * Unless required by applicable law or agreed to in writing, software      *
+ * distributed under the License is distributed on an "AS IS" BASIS,        *
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. *
+ * See the License for the specific language governing permissions and      *
+ * limitations under the License.                                           *
+ ***************************************************************************/
+
+// Package decision //
+package decision
+
+import (
+	"errors"
+	"fmt"
+
+	"github.com/optimizely/go-sdk/v2/pkg/decide"
+	"github.com/optimizely/go-sdk/v2/pkg/decision/reasons"
+	"github.com/optimizely/go-sdk/v2/pkg/entities"
+	"github.com/optimizely/go-sdk/v2/pkg/logging"
+)
+
+// ExperimentCmabService makes decisions for CMAB experiments
+type ExperimentCmabService struct {
+	cmabService CmabService
+	logger      logging.OptimizelyLogProducer
+}
+
+// NewExperimentCmabService creates a new instance of ExperimentCmabService
+func NewExperimentCmabService(cmabService CmabService, logger logging.OptimizelyLogProducer) *ExperimentCmabService {
+	return &ExperimentCmabService{
+		cmabService: cmabService,
+		logger:      logger,
+	}
+}
+
+// GetDecision returns a decision for the given experiment and user context
+func (s *ExperimentCmabService) GetDecision(decisionContext ExperimentDecisionContext, userContext entities.UserContext, options *decide.Options) (decision ExperimentDecision, decisionReasons decide.DecisionReasons, err error) {
+	decisionReasons = decide.NewDecisionReasons(options)
+	experiment := decisionContext.Experiment
+	projectConfig := decisionContext.ProjectConfig
+
+	// Check if experiment is nil or not a CMAB experiment
+	if experiment == nil || !isCmab(*experiment) {
+		message := "Not a CMAB experiment, skipping CMAB decision service"
+		decisionReasons.AddInfo(message)
+		return decision, decisionReasons, nil
+	}
+
+	// Check if CMAB service is available
+	if s.cmabService == nil {
+		message := "CMAB service is not available"
+		decisionReasons.AddInfo(message)
+		return decision, decisionReasons, errors.New(message)
+	}
+
+	// Get CMAB decision
+	cmabDecision, err := s.cmabService.GetDecision(projectConfig, userContext, experiment.ID, options)
+	if err != nil {
+		message := fmt.Sprintf("Failed to get CMAB decision: %v", err)
+		decisionReasons.AddInfo(message)
+		return decision, decisionReasons, fmt.Errorf("failed to get CMAB decision: %w", err)
+	}
+
+	// Find variation by ID
+	for _, variation := range experiment.Variations {
+		if variation.ID != cmabDecision.VariationID {
+			continue
+		}
+
+		// Create a copy of the variation to avoid memory aliasing
+		variationCopy := variation
+		decision.Variation = &variationCopy
+		decision.Reason = reasons.CmabVariationAssigned
+		message := fmt.Sprintf("User bucketed into variation %s by CMAB service", variation.Key)
+		decisionReasons.AddInfo(message)
+		return decision, decisionReasons, nil
+	}
+
+	// If we get here, the variation ID returned by CMAB service was not found
+	message := fmt.Sprintf("variation with ID %s not found in experiment %s", cmabDecision.VariationID, experiment.ID)
+	decisionReasons.AddInfo(message)
+	return decision, decisionReasons, fmt.Errorf("variation with ID %s not found in experiment %s", cmabDecision.VariationID, experiment.ID)
+
+}
+
+// isCmab is a helper method to check if an experiment is a CMAB experiment
+func isCmab(experiment entities.Experiment) bool {
+	return experiment.Cmab != nil
+}