Squashed commit of the following:

commit 32f4b1a13057d56b6de487cdb80ff7c205af01a6
Author: chrislu <chris.lu@gmail.com>
Date:   Sun Aug 20 22:52:19 2023 -0700

    fix compilation

commit e77ad33b7ca0423138fbae26a4433b60923a9588
Author: chrislu <chris.lu@gmail.com>
Date:   Sun Aug 20 22:46:44 2023 -0700

    pub

commit f431f30cc7ca277ca299e3cd118c05537fb9f5c3
Author: chrislu <chris.lu@gmail.com>
Date:   Sun Aug 20 13:27:39 2023 -0700

    fix generic type

commit 4e9dcb18293fd1e3e306e2dceb995dfd67a35e1d
Merge: 30f942580 16e3f2d52
Author: chrislu <chris.lu@gmail.com>
Date:   Sun Aug 20 12:47:14 2023 -0700

    Merge branch 'master' into pubsub

commit 30f942580ad1bb32ae94aade2e3a21ec3ab63e21
Author: chrislu <chris.lu@gmail.com>
Date:   Sun Aug 20 11:10:58 2023 -0700

    wip

commit f8b00980bc2f3879bb43decffd9a08d842f196f2
Author: chrislu <chris.lu@gmail.com>
Date:   Tue Jul 25 09:14:35 2023 -0700

    add design document

commit 08d2bebe42a26ebc39f1542f54d99e73620727dd
Author: chrislu <chris.lu@gmail.com>
Date:   Tue Jul 25 09:14:06 2023 -0700

    minor

commit bcfa7982b262a40fcdce6fc6613fad2ce07c13da
Author: chrislu <chris.lu@gmail.com>
Date:   Tue Jul 25 09:13:49 2023 -0700

    rename

1 files changed, 73 insertions, 0 deletions

diff --git a/weed/mq/topic/topic.go b/weed/mq/topic/topic.go
new file mode 100644
index 000000000..430999179
--- /dev/null
+++ b/weed/mq/topic/topic.go
@@ -0,0 +1,73 @@
+package topic
+
+import (
+	"fmt"
+	"github.com/seaweedfs/seaweedfs/weed/filer"
+	"github.com/seaweedfs/seaweedfs/weed/pb/mq_pb"
+	"time"
+)
+
+type Namespace string
+
+type Topic struct {
+	Namespace Namespace
+	Name      string
+}
+
+func NewTopic(namespace Namespace, name string) Topic {
+	return Topic{
+		Namespace: namespace,
+		Name:      name,
+	}
+}
+func FromPbTopic(topic *mq_pb.Topic) Topic {
+	return Topic{
+		Namespace: Namespace(topic.Namespace),
+		Name:      topic.Name,
+	}
+}
+
+func (tp Topic) String() string {
+	return fmt.Sprintf("%s.%s", tp.Namespace, tp.Name)
+}
+
+type Segment struct {
+	Topic        Topic
+	Id           int32
+	Partition    Partition
+	LastModified time.Time
+}
+
+func FromPbSegment(segment *mq_pb.Segment) *Segment {
+	return &Segment{
+		Topic: Topic{
+			Namespace: Namespace(segment.Namespace),
+			Name:      segment.Topic,
+		},
+		Id: segment.Id,
+		Partition: Partition{
+			RangeStart: segment.Partition.RangeStart,
+			RangeStop:  segment.Partition.RangeStop,
+			RingSize:   segment.Partition.RingSize,
+		},
+	}
+}
+
+func (segment *Segment) ToPbSegment() *mq_pb.Segment {
+	return &mq_pb.Segment{
+		Namespace: string(segment.Topic.Namespace),
+		Topic:     segment.Topic.Name,
+		Id:        segment.Id,
+		Partition: &mq_pb.Partition{
+			RingSize:   segment.Partition.RingSize,
+			RangeStart: segment.Partition.RangeStart,
+			RangeStop:  segment.Partition.RangeStop,
+		},
+	}
+}
+
+func (segment *Segment) DirAndName() (dir string, name string) {
+	dir = fmt.Sprintf("%s/%s/%s", filer.TopicsDir, segment.Topic.Namespace, segment.Topic.Name)
+	name = fmt.Sprintf("%4d.segment", segment.Id)
+	return
+}