[#13] Rename go module name according to NSPCC standards

- refactoring s3 gate structure
- cleanup unused code
- rename go module to `github.com/nspcc-dev/neofs-s3-gate`

closes #13

Signed-off-by: Evgeniy Kulikov <kim@nspcc.ru>

api/layer/util.go

@@ -0,0 +1,113 @@
+package layer
+
+import (
+	"net/http"
+	"os"
+	"strings"
+	"time"
+
+	"github.com/nspcc-dev/neofs-api-go/object"
+)
+
+type (
+	ObjectInfo struct {
+		Bucket      string
+		Name        string
+		Size        int64
+		ContentType string
+		Created     time.Time
+		Headers     map[string]string
+	}
+
+	// ListObjectsInfo - container for list objects.
+	ListObjectsInfo struct {
+		// Indicates whether the returned list objects response is truncated. A
+		// value of true indicates that the list was truncated. The list can be truncated
+		// if the number of objects exceeds the limit allowed or specified
+		// by max keys.
+		IsTruncated bool
+
+		// When response is truncated (the IsTruncated element value in the response
+		// is true), you can use the key name in this field as marker in the subsequent
+		// request to get next set of objects.
+		//
+		// NOTE: This element is returned only if you have delimiter request parameter
+		// specified.
+		ContinuationToken     string
+		NextContinuationToken string
+
+		// List of objects info for this request.
+		Objects []ObjectInfo
+
+		// List of prefixes for this request.
+		Prefixes []string
+	}
+)
+
+const pathSeparator = string(os.PathSeparator)
+
+func userHeaders(h []object.Header) map[string]string {
+	result := make(map[string]string, len(h))
+
+	for i := range h {
+		switch v := h[i].Value.(type) {
+		case *object.Header_UserHeader:
+			result[v.UserHeader.Key] = v.UserHeader.Value
+		default:
+			continue
+		}
+	}
+
+	return result
+}
+
+func objectInfoFromMeta(meta *object.Object) *ObjectInfo {
+	aws3name := meta.SystemHeader.ID.String()
+
+	userHeaders := userHeaders(meta.Headers)
+	if name, ok := userHeaders[AWS3NameHeader]; ok {
+		aws3name = name
+		delete(userHeaders, name)
+	}
+
+	mimeType := http.DetectContentType(meta.Payload)
+
+	return &ObjectInfo{
+		Bucket:      meta.SystemHeader.CID.String(),
+		Name:        aws3name,
+		ContentType: mimeType,
+		Headers:     userHeaders,
+		Size:        int64(meta.SystemHeader.PayloadLength),
+		Created:     time.Unix(meta.SystemHeader.CreatedAt.UnixTime, 0),
+	}
+}
+
+func parseUserHeaders(h map[string]string) []object.Header {
+	headers := make([]object.Header, 0, len(h))
+
+	for k, v := range h {
+		uh := &object.UserHeader{Key: k, Value: v}
+		headers = append(headers, object.Header{
+			Value: &object.Header_UserHeader{UserHeader: uh},
+		})
+	}
+
+	return headers
+}
+
+func nameFromObject(o *object.Object) (string, string) {
+	var (
+		name string
+		uh   = userHeaders(o.Headers)
+	)
+
+	if _, ok := uh[AWS3NameHeader]; !ok {
+		name = o.SystemHeader.ID.String()
+	} else {
+		name = uh[AWS3NameHeader]
+	}
+
+	ind := strings.LastIndex(name, pathSeparator)
+
+	return name[ind+1:], name[:ind+1]
+}