[#174] Add fallback path to search

Fallback path to search is needed because
some software may keep FileName attribute
and ignore FilePath attribute during file
upload. Therefore, if this feature is
enabled under certain conditions (for more
information, see gate-configuration.md) a
search will be performed for the FileName
attribute.

Signed-off-by: Roman Loginov <r.loginov@yadro.com>

internal/handler/handler.go

@@ -35,6 +35,7 @@ type Config interface {
 	IndexPageTemplate() string
 	BufferMaxSizeForPut() uint64
 	NamespaceHeader() string
+	EnableFilepathFallback() bool
 }
 
 // PrmContainer groups parameters of FrostFS.Container operation.
@@ -291,35 +292,58 @@ func (h *Handler) byAttribute(c *fasthttp.RequestCtx, f func(context.Context, re
 		return
 	}
 
-	res, err := h.search(ctx, bktInfo.CID, key, val, object.MatchStringEqual)
+	objID, err := h.findObjectByAttribute(ctx, log, bktInfo.CID, key, val)
 	if err != nil {
-		log.Error(logs.CouldNotSearchForObjects, zap.Error(err))
-		response.Error(c, "could not search for objects: "+err.Error(), fasthttp.StatusBadRequest)
+		if errors.Is(err, io.EOF) {
+			response.Error(c, err.Error(), fasthttp.StatusNotFound)
+			return
+		}
+
+		response.Error(c, err.Error(), fasthttp.StatusBadRequest)
 		return
 	}
 
+	var addrObj oid.Address
+	addrObj.SetContainer(bktInfo.CID)
+	addrObj.SetObject(objID)
+
+	f(ctx, *h.newRequest(c, log), addrObj)
+}
+
+func (h *Handler) findObjectByAttribute(ctx context.Context, log *zap.Logger, cnrID cid.ID, attrKey, attrVal string) (oid.ID, error) {
+	res, err := h.search(ctx, cnrID, attrKey, attrVal, object.MatchStringEqual)
+	if err != nil {
+		log.Error(logs.CouldNotSearchForObjects, zap.Error(err))
+		return oid.ID{}, fmt.Errorf("could not search for objects: %w", err)
+	}
 	defer res.Close()
 
 	buf := make([]oid.ID, 1)
 
 	n, err := res.Read(buf)
 	if n == 0 {
-		if errors.Is(err, io.EOF) {
+		switch {
+		case errors.Is(err, io.EOF) && h.needSearchByFileName(attrKey, attrVal):
+			log.Debug(logs.ObjectNotFoundByFilePathTrySearchByFileName)
+			return h.findObjectByAttribute(ctx, log, cnrID, attrFileName, attrVal)
+		case errors.Is(err, io.EOF):
 			log.Error(logs.ObjectNotFound, zap.Error(err))
-			response.Error(c, "object not found", fasthttp.StatusNotFound)
-			return
+			return oid.ID{}, fmt.Errorf("object not found: %w", err)
+		default:
+			log.Error(logs.ReadObjectListFailed, zap.Error(err))
+			return oid.ID{}, fmt.Errorf("read object list failed: %w", err)
 		}
-
-		log.Error(logs.ReadObjectListFailed, zap.Error(err))
-		response.Error(c, "read object list failed: "+err.Error(), fasthttp.StatusBadRequest)
-		return
 	}
 
-	var addrObj oid.Address
-	addrObj.SetContainer(bktInfo.CID)
-	addrObj.SetObject(buf[0])
+	return buf[0], nil
+}
 
-	f(ctx, *h.newRequest(c, log), addrObj)
+func (h *Handler) needSearchByFileName(key, val string) bool {
+	if key != attrFilePath || !h.config.EnableFilepathFallback() {
+		return false
+	}
+
+	return strings.HasPrefix(val, "/") && strings.Count(val, "/") == 1 || !strings.Contains(val, "/")
 }
 
 // resolveContainer decode container id, if it's not a valid container id