feat: add $flagd.timestamp to json evaluator

core/pkg/eval/json_evaluator.go

@@ -9,6 +9,7 @@ import (
 	"regexp"
 	"strconv"
 	"strings"
+	"time"
 
 	"github.com/diegoholiveira/jsonlogic/v3"
 	"github.com/open-feature/flagd/core/pkg/logger"
@@ -38,7 +39,8 @@ const (
 var regBrace *regexp.Regexp
 
 type flagdProperties struct {
-	FlagKey string `json:"flagKey"`
+	FlagKey   string    `json:"flagKey"`
+	Timestamp time.Time `json:"timestamp"`
 }
 
 func init() {
@@ -321,7 +323,8 @@ func (je *JSONEvaluator) evaluateVariant(reqID string, flagKey string, context m
 		}
 
 		context = je.setFlagdProperties(context, flagdProperties{
-			FlagKey: flagKey,
+			FlagKey:   flagKey,
+			Timestamp: time.Now(),
 		})
 
 		b, err := json.Marshal(context)

core/pkg/eval/json_evaluator_test.go

@@ -1248,4 +1248,36 @@ func TestFlagdAmbientProperties(t *testing.T) {
 			t.Fatalf("expected %s, got %s", model.TargetingMatchReason, reason)
 		}
 	})
+
+	t.Run("timestampIsInTheContext", func(t *testing.T) {
+		evaluator := eval.NewJSONEvaluator(logger.NewLogger(nil, false), store.NewFlags())
+
+		_, _, err := evaluator.SetState(sync.DataSync{FlagData: `{
+			"flags": {
+				"welcome-banner": {
+					"state": "ENABLED",
+					"variants": {
+						"true": true,
+						"false": false
+					},
+					"defaultVariant": "false",
+					"targeting": {
+						"if": [ { "var": ["$flagd.timestamp", false] }, true, false ]
+					}
+				}
+			}
+		}`})
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		value, variant, reason, _, err := evaluator.ResolveBooleanValue(context.Background(), "default", "welcome-banner", nil)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		if !value || variant != "true" || reason != model.TargetingMatchReason {
+			t.Fatal("timestamp was not in the context")
+		}
+	})
 }