From 164cd10af8676d52ce1ef78edbac764a59ea3727 Mon Sep 17 00:00:00 2001
From: Alex Vanin <alexey@nspcc.ru>
Date: Wed, 10 Nov 2021 14:07:57 +0300
Subject: [PATCH] [#948] engine: Hide shard IDs in ListWithCursor

Signed-off-by: Alex Vanin <alexey@nspcc.ru>
---
 pkg/local_object_storage/engine/list.go      | 107 ++++++++++++++++---
 pkg/local_object_storage/engine/list_test.go |  21 ++--
 2 files changed, 105 insertions(+), 23 deletions(-)

diff --git a/pkg/local_object_storage/engine/list.go b/pkg/local_object_storage/engine/list.go
index 64e1e3540..8d887c248 100644
--- a/pkg/local_object_storage/engine/list.go
+++ b/pkg/local_object_storage/engine/list.go
@@ -1,7 +1,12 @@
 package engine
 
 import (
+	"fmt"
+	"sort"
+	"strconv"
+
 	"github.com/nspcc-dev/neofs-api-go/pkg/object"
+	core "github.com/nspcc-dev/neofs-node/pkg/core/object"
 	"github.com/nspcc-dev/neofs-node/pkg/local_object_storage/shard"
 )
 
@@ -9,7 +14,6 @@ import (
 type ListWithCursorPrm struct {
 	count  uint32
 	cursor string
-	shard  shard.ID
 }
 
 // WithCount sets maximum amount of addresses that ListWithCursor can return.
@@ -26,12 +30,6 @@ func (p *ListWithCursorPrm) WithCursor(cursor string) *ListWithCursorPrm {
 	return p
 }
 
-// WithShardID sets shard where listing will process.
-func (p *ListWithCursorPrm) WithShardID(id shard.ID) *ListWithCursorPrm {
-	p.shard = id
-	return p
-}
-
 // ListWithCursorRes contains values returned from ListWithCursor operation.
 type ListWithCursorRes struct {
 	addrList []*object.Address
@@ -53,22 +51,99 @@ func (l ListWithCursorRes) Cursor() string {
 // Does not include inhumed objects. Use cursor value from response
 // for consecutive requests.
 func (e *StorageEngine) ListWithCursor(prm *ListWithCursorPrm) (*ListWithCursorRes, error) {
+	var (
+		err    error
+		result = make([]*object.Address, 0, prm.count)
+	)
+
+	// 1. Get available shards and sort them.
 	e.mtx.RLock()
-	shardInstance, ok := e.shards[prm.shard.String()]
+	shardIDs := make([]string, 0, len(e.shards))
+	for id := range e.shards {
+		shardIDs = append(shardIDs, id)
+	}
 	e.mtx.RUnlock()
 
-	if !ok {
-		return nil, errShardNotFound
+	if len(shardIDs) == 0 {
+		return nil, core.ErrEndOfListing
 	}
 
-	shardPrm := new(shard.ListWithCursorPrm).WithCursor(prm.cursor).WithCount(prm.count)
-	res, err := shardInstance.ListWithCursor(shardPrm)
-	if err != nil {
-		return nil, err
+	sort.Slice(shardIDs, func(i, j int) bool {
+		return shardIDs[i] < shardIDs[j]
+	})
+
+	// 2. Decode shard ID from cursor.
+	cursor := prm.cursor
+	cursorShardID := shardIDs[0]
+	if len(cursor) > 0 {
+		cursorShardID, cursor, err = decodeID(cursor)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	// 3. Iterate over available shards. Skip unavailable shards.
+	for i := range shardIDs {
+		if len(result) >= int(prm.count) {
+			break
+		}
+
+		if shardIDs[i] < cursorShardID {
+			continue
+		}
+
+		e.mtx.RLock()
+		shardInstance, ok := e.shards[shardIDs[i]]
+		e.mtx.RUnlock()
+		if !ok {
+			continue
+		}
+
+		count := uint32(int(prm.count) - len(result))
+		shardPrm := new(shard.ListWithCursorPrm).WithCount(count)
+		if shardIDs[i] == cursorShardID {
+			shardPrm.WithCursor(cursor)
+		}
+
+		res, err := shardInstance.ListWithCursor(shardPrm)
+		if err != nil {
+			continue
+		}
+
+		result = append(result, res.AddressList()...)
+		cursor = res.Cursor()
+		cursorShardID = shardIDs[i]
+	}
+
+	if len(result) == 0 {
+		return nil, core.ErrEndOfListing
 	}
 
 	return &ListWithCursorRes{
-		addrList: res.AddressList(),
-		cursor:   res.Cursor(),
+		addrList: result,
+		cursor:   encodeID(cursorShardID, cursor),
 	}, nil
 }
+
+func decodeID(cursor string) (shardID string, shardCursor string, err error) {
+	ln := len(cursor)
+	if ln < 2 {
+		return "", "", fmt.Errorf("invalid cursor %s", cursor)
+	}
+
+	idLen, err := strconv.Atoi(cursor[:2])
+	if err != nil {
+		return "", "", fmt.Errorf("invalid cursor %s", cursor)
+	}
+
+	if len(cursor) < 2+idLen {
+		return "", "", fmt.Errorf("invalid cursor %s", cursor)
+	}
+
+	return cursor[2 : 2+idLen], cursor[2+idLen:], nil
+}
+
+func encodeID(id, cursor string) string {
+	prefix := fmt.Sprintf("%02d", len(id))
+	return prefix + id + cursor
+}
diff --git a/pkg/local_object_storage/engine/list_test.go b/pkg/local_object_storage/engine/list_test.go
index 78d51eedd..ecd1918a1 100644
--- a/pkg/local_object_storage/engine/list_test.go
+++ b/pkg/local_object_storage/engine/list_test.go
@@ -1,6 +1,7 @@
 package engine
 
 import (
+	"errors"
 	"os"
 	"sort"
 	"testing"
@@ -37,17 +38,23 @@ func TestListWithCursor(t *testing.T) {
 
 	expected = sortAddresses(expected)
 
-	for _, shard := range e.DumpInfo().Shards {
-		prm := new(ListWithCursorPrm).WithShardID(*shard.ID).WithCount(total)
-		res, err := e.ListWithCursor(prm)
-		require.NoError(t, err)
-		require.NotEmpty(t, res.AddressList())
+	prm := new(ListWithCursorPrm).WithCount(1)
+	res, err := e.ListWithCursor(prm)
+	require.NoError(t, err)
+	require.NotEmpty(t, res.AddressList())
+	got = append(got, res.AddressList()...)
 
+	for i := 0; i < total-1; i++ {
+		res, err = e.ListWithCursor(prm.WithCursor(res.Cursor()))
+		if errors.Is(err, core.ErrEndOfListing) {
+			break
+		}
 		got = append(got, res.AddressList()...)
-		_, err = e.ListWithCursor(prm.WithCursor(res.Cursor()))
-		require.ErrorIs(t, err, core.ErrEndOfListing)
 	}
 
+	_, err = e.ListWithCursor(prm.WithCursor(res.Cursor()))
+	require.ErrorIs(t, err, core.ErrEndOfListing)
+
 	got = sortAddresses(got)
 	require.Equal(t, expected, got)
 }