[#19] Extract uploading logic into a separate package

Signed-off-by: Pavel Korotkov <pavel@nspcc.ru>

uploader/filter.go

@@ -0,0 +1,68 @@
+package uploader
+
+import (
+	"bytes"
+
+	"github.com/valyala/fasthttp"
+	"go.uber.org/zap"
+)
+
+const (
+	userAttributeHeaderPrefix  = "X-Attribute-"
+	neofsAttributeHeaderPrefix = "NEOFS-"
+
+	systemAttributePrefix = "__NEOFS__"
+)
+
+func systemTranslator(key []byte) []byte {
+	// replace `NEOFS-` with `__NEOFS__`
+	key = bytes.Replace(key, []byte(neofsAttributeHeaderPrefix), []byte(systemAttributePrefix), 1)
+
+	// replace `-` with `_`
+	key = bytes.ReplaceAll(key, []byte("-"), []byte("_"))
+
+	// replace with uppercase
+	return bytes.ToUpper(key)
+}
+
+func filterHeaders(l *zap.Logger, header *fasthttp.RequestHeader) map[string]string {
+	result := make(map[string]string)
+	prefix := []byte(userAttributeHeaderPrefix)
+	system := []byte(neofsAttributeHeaderPrefix)
+
+	header.VisitAll(func(key, val []byte) {
+		// checks that key and val not empty
+		if len(key) == 0 || len(val) == 0 {
+			return
+		}
+
+		// checks that key has attribute prefix
+		if !bytes.HasPrefix(key, prefix) {
+			return
+		}
+
+		// removing attribute prefix
+		key = bytes.TrimPrefix(key, prefix)
+
+		// checks that it's a system NeoFS header
+		if bytes.HasPrefix(key, system) {
+			key = systemTranslator(key)
+		}
+
+		// checks that attribute key not empty
+		if len(key) == 0 {
+			return
+		}
+
+		// make string representation of key / val
+		k, v := string(key), string(val)
+
+		result[k] = v
+
+		l.Debug("add attribute to result object",
+			zap.String("key", k),
+			zap.String("val", v))
+	})
+
+	return result
+}