[FSSDK-10553] add IsEveryoneElseVariation marker in decide API (#422)

* add IsEveryoneElseVariation marker in decide API

* update acceptance tests

* update unit test

* update tests

* update tests

* update tests

* update test

Author: pulak-opti

pkg/handlers/decide.go

@@ -20,16 +20,20 @@ package handlers
 import (
 	"errors"
 	"net/http"
+	"strings"
 
 	"github.com/go-chi/render"
 
 	"github.com/optimizely/agent/pkg/middleware"
 	"github.com/optimizely/go-sdk/v2/pkg/client"
+	"github.com/optimizely/go-sdk/v2/pkg/config"
 	"github.com/optimizely/go-sdk/v2/pkg/decide"
 	"github.com/optimizely/go-sdk/v2/pkg/decision"
 	"github.com/optimizely/go-sdk/v2/pkg/odp/segment"
 )
 
+const DefaultRolloutPrefix = "default-"
+
 // DecideBody defines the request body for decide API
 type DecideBody struct {
 	UserID               string                            `json:"userId"`
@@ -50,7 +54,8 @@ type ForcedDecision struct {
 // DecideOut defines the response
 type DecideOut struct {
 	client.OptimizelyDecision
-	Variables map[string]interface{} `json:"variables,omitempty"`
+	Variables               map[string]interface{} `json:"variables,omitempty"`
+	IsEveryoneElseVariation bool                   `json:"isEveryoneElseVariation"`
 }
 
 // Decide makes feature decisions for the selected query parameters
@@ -97,6 +102,12 @@ func Decide(w http.ResponseWriter, r *http.Request) {
 		keys = r.Form["keys"]
 	}
 
+	featureMap := make(map[string]config.OptimizelyFeature)
+	cfg := optlyClient.GetOptimizelyConfig()
+	if cfg != nil {
+		featureMap = cfg.FeaturesMap
+	}
+
 	var decides map[string]client.OptimizelyDecision
 	switch len(keys) {
 	case 0:
@@ -107,7 +118,7 @@ func Decide(w http.ResponseWriter, r *http.Request) {
 		key := keys[0]
 		logger.Debug().Str("featureKey", key).Msg("fetching feature decision")
 		d := optimizelyUserContext.Decide(key, decideOptions)
-		decideOut := DecideOut{d, d.Variables.ToMap()}
+		decideOut := DecideOut{d, d.Variables.ToMap(), isEveryoneElseVariation(featureMap[d.FlagKey].DeliveryRules, d.RuleKey)}
 		render.JSON(w, r, decideOut)
 		return
 	default:
@@ -117,7 +128,7 @@ func Decide(w http.ResponseWriter, r *http.Request) {
 
 	decideOuts := []DecideOut{}
 	for _, d := range decides {
-		decideOut := DecideOut{d, d.Variables.ToMap()}
+		decideOut := DecideOut{d, d.Variables.ToMap(), isEveryoneElseVariation(featureMap[d.FlagKey].DeliveryRules, d.RuleKey)}
 		decideOuts = append(decideOuts, decideOut)
 		logger.Debug().Msgf("Feature %q is enabled for user %s? %t", d.FlagKey, d.UserContext.UserID, d.Enabled)
 	}
@@ -137,3 +148,12 @@ func getUserContextWithOptions(r *http.Request) (DecideBody, error) {
 
 	return body, nil
 }
+
+func isEveryoneElseVariation(rules []config.OptimizelyExperiment, ruleKey string) bool {
+	for _, r := range rules {
+		if r.Key == ruleKey {
+			return r.Key == r.ID && strings.HasPrefix(r.Key, DefaultRolloutPrefix)
+		}
+	}
+	return false
+}