Setup legacy search based on mode (#98908)

pkg/storage/unified/resource/go.mod

@@ -17,6 +17,7 @@ require (
 	github.com/grafana/grafana v11.4.0-00010101000000-000000000000+incompatible
 	github.com/grafana/grafana-plugin-sdk-go v0.263.0
 	github.com/grafana/grafana/pkg/apimachinery v0.0.0-20250121113133-e747350fee2d
+	github.com/grafana/grafana/pkg/apiserver v0.0.0-20250121113133-e747350fee2d
 	github.com/grpc-ecosystem/go-grpc-middleware/v2 v2.2.0
 	github.com/hashicorp/golang-lru/v2 v2.0.7
 	github.com/prometheus/client_golang v1.20.5
@@ -120,7 +121,6 @@ require (
 	github.com/grafana/grafana-app-sdk/logging v0.29.0 // indirect
 	github.com/grafana/grafana-aws-sdk v0.31.5 // indirect
 	github.com/grafana/grafana-azure-sdk-go/v2 v2.1.6 // indirect
-	github.com/grafana/grafana/pkg/apiserver v0.0.0-20250121113133-e747350fee2d // indirect
 	github.com/grafana/otel-profiling-go v0.5.1 // indirect
 	github.com/grafana/pyroscope-go/godeltaprof v0.1.8 // indirect
 	github.com/grafana/sqlds/v4 v4.1.3 // indirect

pkg/storage/unified/resource/search_client.go

@@ -0,0 +1,20 @@
+package resource
+
+import (
+	"github.com/grafana/grafana/pkg/apiserver/rest"
+	"github.com/grafana/grafana/pkg/setting"
+)
+
+func NewSearchClient(cfg *setting.Cfg, unifiedStorageConfigKey string, unifiedClient ResourceIndexClient, legacyClient ResourceIndexClient) ResourceIndexClient {
+	config, ok := cfg.UnifiedStorage[unifiedStorageConfigKey]
+	if !ok {
+		return legacyClient
+	}
+
+	switch config.DualWriterMode {
+	case rest.Mode0, rest.Mode1, rest.Mode2:
+		return legacyClient
+	default:
+		return unifiedClient
+	}
+}