From 0590f84d684bae348797c223e5602dcf181281a5 Mon Sep 17 00:00:00 2001
From: Denis Kirillov <d.kirillov@yadro.com>
Date: Tue, 13 Jun 2023 12:33:03 +0300
Subject: [PATCH] [#135] crdt: Add GSet

Signed-off-by: Denis Kirillov <d.kirillov@yadro.com>
---
 internal/frostfs/crdt/gset.go      | 124 +++++++++++++++++++++++++++++
 internal/frostfs/crdt/gset_test.go |  38 +++++++++
 2 files changed, 162 insertions(+)
 create mode 100644 internal/frostfs/crdt/gset.go
 create mode 100644 internal/frostfs/crdt/gset_test.go

diff --git a/internal/frostfs/crdt/gset.go b/internal/frostfs/crdt/gset.go
new file mode 100644
index 0000000..977c7d7
--- /dev/null
+++ b/internal/frostfs/crdt/gset.go
@@ -0,0 +1,124 @@
+package crdt
+
+import (
+	"sort"
+	"strings"
+
+	"git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object"
+	oid "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object/id"
+)
+
+const (
+	versionsAddAttr = "S3-CRDT-Versions-Add"
+)
+
+type ObjectVersions struct {
+	name     string
+	objects  []*ObjectVersion
+	addList  []string
+	isSorted bool
+}
+
+type ObjectVersion struct {
+	OjbID         oid.ID
+	Headers       map[string]string
+	CreationEpoch uint64
+}
+
+func (o *ObjectVersion) VersionID() string {
+	return o.OjbID.EncodeToString()
+}
+
+func NewObjectVersions(name string) *ObjectVersions {
+	return &ObjectVersions{name: name}
+}
+
+func NewObjectVersion(obj *object.Object) *ObjectVersion {
+	objID, _ := obj.ID()
+	headers := make(map[string]string)
+
+	for _, attr := range obj.Attributes() {
+		headers[attr.Key()] = attr.Value()
+	}
+
+	return &ObjectVersion{
+		OjbID:         objID,
+		Headers:       headers,
+		CreationEpoch: obj.CreationEpoch(),
+	}
+}
+
+func (v *ObjectVersions) Name() string {
+	return v.name
+}
+
+func (v *ObjectVersions) AppendVersion(ov *ObjectVersion) {
+	addVers := append(splitVersions(ov.Headers[versionsAddAttr]), ov.VersionID())
+	v.objects = append(v.objects, ov)
+	for _, add := range addVers {
+		if !contains(v.addList, add) {
+			v.addList = append(v.addList, add)
+		}
+	}
+	v.isSorted = false
+}
+
+func (v *ObjectVersions) GetCRDTHeaders() map[string]string {
+	if len(v.objects) == 0 {
+		return nil
+	}
+
+	headers := make(map[string]string, 2)
+
+	if len(v.addList) != 0 {
+		headers[versionsAddAttr] = v.getAddHeader()
+	}
+
+	return headers
+}
+
+func (v *ObjectVersions) GetLast() *ObjectVersion {
+	if len(v.objects) == 0 {
+		return nil
+	}
+
+	v.sort()
+	return v.objects[len(v.objects)-1]
+}
+
+func splitVersions(header string) []string {
+	if len(header) == 0 {
+		return nil
+	}
+
+	return strings.Split(header, ",")
+}
+
+func (v *ObjectVersions) sort() {
+	if !v.isSorted {
+		sort.Slice(v.objects, func(i, j int) bool {
+			return less(v.objects[i], v.objects[j])
+		})
+		v.isSorted = true
+	}
+}
+
+func (v *ObjectVersions) getAddHeader() string {
+	return strings.Join(v.addList, ",")
+}
+
+func less(ov1, ov2 *ObjectVersion) bool {
+	if ov1.CreationEpoch == ov2.CreationEpoch {
+		return ov1.VersionID() < ov2.VersionID()
+	}
+	return ov1.CreationEpoch < ov2.CreationEpoch
+}
+
+func contains(list []string, elem string) bool {
+	for _, item := range list {
+		if elem == item {
+			return true
+		}
+	}
+	return false
+}
diff --git a/internal/frostfs/crdt/gset_test.go b/internal/frostfs/crdt/gset_test.go
new file mode 100644
index 0000000..a26589d
--- /dev/null
+++ b/internal/frostfs/crdt/gset_test.go
@@ -0,0 +1,38 @@
+package crdt
+
+import (
+	"testing"
+
+	oid "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object/id"
+	"github.com/stretchr/testify/require"
+)
+
+func TestObjectVersionsSort(t *testing.T) {
+	t.Run("sort by epoch", func(t *testing.T) {
+		versions := NewObjectVersions("test")
+		versions.AppendVersion(&ObjectVersion{CreationEpoch: 3})
+		versions.AppendVersion(&ObjectVersion{CreationEpoch: 1})
+		versions.AppendVersion(&ObjectVersion{CreationEpoch: 2})
+
+		last := versions.GetLast()
+		require.Equal(t, uint64(3), last.CreationEpoch)
+	})
+
+	t.Run("sort by oids", func(t *testing.T) {
+		versions := NewObjectVersions("test")
+		versions.AppendVersion(&ObjectVersion{CreationEpoch: 3, OjbID: getTestOID(2)})
+		versions.AppendVersion(&ObjectVersion{CreationEpoch: 3, OjbID: getTestOID(1)})
+		versions.AppendVersion(&ObjectVersion{CreationEpoch: 1, OjbID: getTestOID(3)})
+		versions.AppendVersion(&ObjectVersion{CreationEpoch: 2, OjbID: getTestOID(4)})
+
+		last := versions.GetLast()
+		require.Equal(t, uint64(3), last.CreationEpoch)
+		require.Equal(t, getTestOID(2).String(), last.VersionID())
+	})
+}
+
+func getTestOID(val byte) oid.ID {
+	var res oid.ID
+	res.SetSHA256([32]byte{val})
+	return res
+}