protocol/packp: UploadPackResponse implementation (#161)

* plumbing/protocol: paktp avoid duplication of haves, wants and shallow

* protocol/pakp: UploadPackResponse implementation

* changes

* changes

* changes

* debug

* changes

1 files changed, 70 insertions, 0 deletions

diff --git a/plumbing/protocol/packp/srvresp.go b/plumbing/protocol/packp/srvresp.go
new file mode 100644
index 0000000..3284fa2
--- /dev/null
+++ b/plumbing/protocol/packp/srvresp.go
@@ -0,0 +1,70 @@
+package packp
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"io"
+
+	"gopkg.in/src-d/go-git.v4/plumbing"
+	"gopkg.in/src-d/go-git.v4/plumbing/format/pktline"
+)
+
+const ackLineLen = 44
+
+// ServerResponse object acknowledgement from upload-pack service
+// TODO: implement support for multi_ack or multi_ack_detailed responses
+type ServerResponse struct {
+	ACKs []plumbing.Hash
+}
+
+// Decode decodes the response into the struct, isMultiACK should be true, if
+// the request was done with multi_ack or multi_ack_detailed capabilities
+func (r *ServerResponse) Decode(reader io.Reader, isMultiACK bool) error {
+	if isMultiACK {
+		return errors.New("multi_ack and multi_ack_detailed are not supported")
+	}
+
+	s := pktline.NewScanner(reader)
+
+	for s.Scan() {
+		line := s.Bytes()
+
+		if err := r.decodeLine(line); err != nil {
+			return err
+		}
+
+		if !isMultiACK {
+			break
+		}
+	}
+
+	return s.Err()
+}
+
+func (r *ServerResponse) decodeLine(line []byte) error {
+	if len(line) == 0 {
+		return fmt.Errorf("unexpected flush")
+	}
+
+	if bytes.Compare(line[0:3], ack) == 0 {
+		return r.decodeACKLine(line)
+	}
+
+	if bytes.Compare(line[0:3], nak) == 0 {
+		return nil
+	}
+
+	return fmt.Errorf("unexpected content %q", string(line))
+}
+
+func (r *ServerResponse) decodeACKLine(line []byte) error {
+	if len(line) < ackLineLen {
+		return fmt.Errorf("malformed ACK %q", line)
+	}
+
+	sp := bytes.Index(line, []byte(" "))
+	h := plumbing.NewHash(string(line[sp+1 : sp+41]))
+	r.ACKs = append(r.ACKs, h)
+	return nil
+}