From 0f97a1e917a2c977e5c2fb4d86feee181285cf7c Mon Sep 17 00:00:00 2001
From: Alexander Chuprov <a.chuprov@yadro.com>
Date: Thu, 13 Feb 2025 19:33:19 +0300
Subject: [PATCH] [#294] user: Implement Cmp() function for ID struct

Signed-off-by: Alexander Chuprov <a.chuprov@yadro.com>
---
 user/id.go      |  6 ++++++
 user/id_test.go | 16 ++++++++++++++++
 2 files changed, 22 insertions(+)

diff --git a/user/id.go b/user/id.go
index c8e2d14..0529414 100644
--- a/user/id.go
+++ b/user/id.go
@@ -123,3 +123,9 @@ func (x *ID) setUserID(w []byte) error {
 
 	return nil
 }
+
+// Cmp returns an integer comparing two base58 encoded user ID lexicographically.
+// The result will be 0 if a == b, -1 if a < b, and +1 if a > b.
+func (x ID) Cmp(x2 ID) int {
+	return bytes.Compare([]byte(x.EncodeToString()), []byte(x2.EncodeToString()))
+}
diff --git a/user/id_test.go b/user/id_test.go
index c517dc5..78d4b83 100644
--- a/user/id_test.go
+++ b/user/id_test.go
@@ -3,6 +3,7 @@ package user_test
 import (
 	"bytes"
 	"crypto/rand"
+	"slices"
 	"testing"
 
 	"git.frostfs.info/TrueCloudLab/frostfs-sdk-go/api/refs"
@@ -132,3 +133,18 @@ func TestID_Equal(t *testing.T) {
 	require.True(t, id3.Equals(id1)) // commutativity
 	require.False(t, id1.Equals(id2))
 }
+
+func TestID__Cmp(t *testing.T) {
+	id1 := usertest.ID()
+	id2 := usertest.ID()
+	id3 := usertest.ID()
+
+	arr := []ID{id1, id2, id3}
+
+	slices.SortFunc(arr, ID.Cmp)
+	for i := 1; i < len(arr); i++ {
+		if bytes.Compare([]byte(arr[i-1].EncodeToString()), []byte(arr[i].EncodeToString())) > 0 {
+			t.Fatalf("arrays are not sorted correctly")
+		}
+	}
+}