From 21708d54086aa5960a9b20ce76c7874af9812a2a Mon Sep 17 00:00:00 2001
From: Alex Vanin <alexey@nspcc.ru>
Date: Tue, 1 Dec 2020 14:06:14 +0300
Subject: [PATCH] [#222] Add Exists method in storage engine

Signed-off-by: Alex Vanin <alexey@nspcc.ru>
---
 pkg/local_object_storage/engine/exists.go | 81 +++++++++++++++++++++++
 pkg/local_object_storage/engine/put.go    | 24 ++-----
 2 files changed, 86 insertions(+), 19 deletions(-)
 create mode 100644 pkg/local_object_storage/engine/exists.go

diff --git a/pkg/local_object_storage/engine/exists.go b/pkg/local_object_storage/engine/exists.go
new file mode 100644
index 000000000..6febe5891
--- /dev/null
+++ b/pkg/local_object_storage/engine/exists.go
@@ -0,0 +1,81 @@
+package engine
+
+import (
+	"errors"
+
+	objectSDK "github.com/nspcc-dev/neofs-api-go/pkg/object"
+	"github.com/nspcc-dev/neofs-node/pkg/core/object"
+	"github.com/nspcc-dev/neofs-node/pkg/local_object_storage/shard"
+	"go.uber.org/zap"
+)
+
+// ExistsPrm groups the parameters of Exists operation.
+type ExistsPrm struct {
+	addr *objectSDK.Address
+}
+
+// ExistsRes groups resulting values of Exists operation.
+type ExistsRes struct {
+	ex bool
+}
+
+// WithAddress is an Exists option to set object checked for existence.
+func (p *ExistsPrm) WithAddress(addr *objectSDK.Address) *ExistsPrm {
+	if p != nil {
+		p.addr = addr
+	}
+
+	return p
+}
+
+// Exists returns the fact that the object is in the storage engine.
+func (p *ExistsRes) Exists() bool {
+	return p.ex
+}
+
+// Exists checks if object is presented in storage engine
+//
+// Returns any error encountered that does not allow to
+// unambiguously determine the presence of an object.
+func (e *StorageEngine) Exists(prm *ExistsPrm) (*ExistsRes, error) {
+	exists, err := e.exists(prm.addr)
+
+	return &ExistsRes{
+		ex: exists,
+	}, err
+}
+
+func (e *StorageEngine) exists(addr *objectSDK.Address) (bool, error) {
+	shPrm := new(shard.ExistsPrm).WithAddress(addr)
+	alreadyRemoved := false
+	exists := false
+
+	e.iterateOverSortedShards(addr, func(_ int, sh *shard.Shard) (stop bool) {
+		res, err := sh.Exists(shPrm)
+		if err != nil {
+			if errors.Is(err, object.ErrAlreadyRemoved) {
+				alreadyRemoved = true
+
+				return true
+			}
+
+			// TODO: smth wrong with shard, need to be processed
+			e.log.Warn("could not check existence of object in shard",
+				zap.Stringer("shard", sh.ID()),
+				zap.String("error", err.Error()),
+			)
+		}
+
+		if res != nil && !exists {
+			exists = res.Exists()
+		}
+
+		return false
+	})
+
+	if alreadyRemoved {
+		return false, object.ErrAlreadyRemoved
+	}
+
+	return exists, nil
+}
diff --git a/pkg/local_object_storage/engine/put.go b/pkg/local_object_storage/engine/put.go
index 55d212aa2..2d5b0926e 100644
--- a/pkg/local_object_storage/engine/put.go
+++ b/pkg/local_object_storage/engine/put.go
@@ -34,27 +34,14 @@ func (p *PutPrm) WithObject(obj *object.Object) *PutPrm {
 // Returns any error encountered that
 // did not allow to completely save the object.
 func (e *StorageEngine) Put(prm *PutPrm) (*PutRes, error) {
-	alreadyRemoved := false // first check if object has not been marked as removed
+	_, err := e.exists(prm.obj.Address()) // todo: make this check parallel
+	if err != nil {
+		return nil, err
+	}
 
 	existPrm := new(shard.ExistsPrm)
 	existPrm.WithAddress(prm.obj.Address())
 
-	// todo: make this check parallel
-	e.iterateOverUnsortedShards(func(s *shard.Shard) (stop bool) {
-		_, err := s.Exists(existPrm)
-		if err != nil && errors.Is(err, object.ErrAlreadyRemoved) {
-			alreadyRemoved = true
-
-			return true
-		}
-
-		return false
-	})
-
-	if alreadyRemoved {
-		return nil, object.ErrAlreadyRemoved
-	}
-
 	finished := false
 
 	e.iterateOverSortedShards(prm.obj.Address(), func(ind int, s *shard.Shard) (stop bool) {
@@ -96,11 +83,10 @@ func (e *StorageEngine) Put(prm *PutPrm) (*PutRes, error) {
 		}
 
 		finished = true
+
 		return true
 	})
 
-	var err error = nil
-
 	if !finished {
 		err = errPutShard
 	}