From 82d1712f3c3d1edb4f91693943154f5f5425b110 Mon Sep 17 00:00:00 2001
From: "R.I.Pienaar" <rip@devco.net>
Date: Tue, 10 Sep 2024 13:02:11 +0200
Subject: [PATCH] Adds a utility to remove server metadata

Signed-off-by: R.I.Pienaar <rip@devco.net>
---
 api/jetstream.go |  2 ++
 jsm.go           | 26 ++++++++++++++++++++++++++
 test/jsm_test.go | 36 ++++++++++++++++++++++++++++++++++++
 3 files changed, 64 insertions(+)

diff --git a/api/jetstream.go b/api/jetstream.go
index f413ea3..1b3c1ca 100644
--- a/api/jetstream.go
+++ b/api/jetstream.go
@@ -27,6 +27,8 @@ const (
 	JSAdvisoryPrefix = "$JS.EVENT.ADVISORY"
 	JSApiAccountInfo = "$JS.API.INFO"
 
+	// also update FilterServerMetadata when this changes
+
 	JSMetaCreatedServerLevel   = "_nats.created.server.api_level"
 	JSMetaCreatedServerVersion = "_nats.created.server.version"
 	JSMetaCurrentServerLevel   = "_nats.server.api_level"
diff --git a/jsm.go b/jsm.go
index 486e667..52d49d6 100644
--- a/jsm.go
+++ b/jsm.go
@@ -21,6 +21,7 @@ import (
 	"errors"
 	"fmt"
 	"regexp"
+	"slices"
 	"strconv"
 	"strings"
 	"time"
@@ -310,3 +311,28 @@ func ParseDuration(d string) (time.Duration, error) {
 
 	return time.Duration(neg) * r, nil
 }
+
+// FilterServerMetadata removes a copy of metadata with the server generated metadata removed
+func FilterServerMetadata(metadata map[string]string) map[string]string {
+	if metadata == nil {
+		return nil
+	}
+
+	nm := map[string]string{}
+	reserved := []string{
+		api.JSMetaCurrentServerVersion,
+		api.JSMetaCurrentServerLevel,
+		api.JSMetaCreatedServerVersion,
+		api.JSMetaCreatedServerVersion,
+		api.JsMetaRequiredServerLevel,
+		api.JSMetaCreatedServerLevel,
+	}
+
+	for k, v := range metadata {
+		if !slices.Contains(reserved, k) {
+			nm[k] = v
+		}
+	}
+
+	return nm
+}
diff --git a/test/jsm_test.go b/test/jsm_test.go
index 31e1b8f..1f1d188 100644
--- a/test/jsm_test.go
+++ b/test/jsm_test.go
@@ -16,6 +16,7 @@ package test
 import (
 	"encoding/json"
 	"fmt"
+	"reflect"
 	"testing"
 
 	"github.com/nats-io/jsm.go/api"
@@ -145,3 +146,38 @@ func TestIsNatsError(t *testing.T) {
 		t.Fatalf("Non api error is 10077")
 	}
 }
+
+func TestFilterServerMetadata(t *testing.T) {
+	srv, nc, mgr := startJSServer(t)
+	defer srv.Shutdown()
+	defer nc.Flush()
+
+	s, err := mgr.NewStream("q1", jsm.Subjects("in.q1"), jsm.StreamMetadata(map[string]string{
+		"io.nats.monitor.enabled":       "1",
+		"io.nats.monitor.lag-critical":  "100",
+		"io.nats.monitor.msgs-critical": "500",
+		"io.nats.monitor.msgs-warn":     "999",
+		"io.nats.monitor.peer-expect":   "3",
+		"io.nats.monitor.seen-critical": "5m",
+	}))
+	checkErr(t, err, "create failed")
+
+	if _, ok := s.Metadata()[api.JsMetaRequiredServerLevel]; !ok {
+		t.Fatalf("No server metadata added")
+	}
+
+	newMeta := jsm.FilterServerMetadata(s.Metadata())
+
+	expected := map[string]string{
+		"io.nats.monitor.enabled":       "1",
+		"io.nats.monitor.lag-critical":  "100",
+		"io.nats.monitor.msgs-critical": "500",
+		"io.nats.monitor.msgs-warn":     "999",
+		"io.nats.monitor.peer-expect":   "3",
+		"io.nats.monitor.seen-critical": "5m",
+	}
+
+	if !reflect.DeepEqual(newMeta, expected) {
+		t.Fatalf("all server data was not removed: %v", newMeta)
+	}
+}