2 files changed, 173 insertions, 0 deletions
diff --git a/objects/object_snapshot.go b/objects/object_snapshot.go
new file mode 100644
index 0000000..a161f27
--- /dev/null
+++ b/objects/object_snapshot.go
@@ -0,0 +1,111 @@
+package objects
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"io"
+	"strings"
+	"time"
+)
+
+type Snapshot struct {
+	Tree      ObjectId
+	Date      time.Time
+	Container string
+	Comment   string
+}
+
+func (s Snapshot) Type() ObjectType {
+	return OTSnapshot
+}
+
+func appendKVPair(b []byte, k, v string) []byte {
+	b = append(b, []byte(k)...)
+	b = append(b, ' ')
+	b = append(b, []byte(v)...)
+	b = append(b, '\n')
+	return b
+}
+
+func (s Snapshot) Payload() (out []byte) {
+	out = appendKVPair(out, "container", s.Container)
+	out = appendKVPair(out, "date", s.Date.Format(time.RFC3339))
+	out = appendKVPair(out, "tree", s.Tree.String())
+
+	if s.Comment != "" {
+		out = append(out, '\n')
+		out = append(out, []byte(s.Comment)...)
+	}
+
+	return out
+}
+
+func (s *Snapshot) FromPayload(payload []byte) error {
+	r := bytes.NewBuffer(payload)
+
+	seenContainer := false
+	seenDate := false
+	seenTree := false
+
+	for {
+		line, err := r.ReadString('\n')
+		if err != nil && err != io.EOF {
+			return err
+		}
+		line = strings.TrimSpace(line)
+
+		if line == "" {
+			break // Header read successfully
+		}
+
+		parts := strings.SplitN(line, " ", 2)
+		if len(parts) != 2 {
+			return fmt.Errorf("Invalid header: %s", line)
+		}
+
+		headerval := strings.TrimSpace(parts[1])
+		switch parts[0] {
+		case "container":
+			s.Container = headerval
+			seenContainer = true
+		case "date":
+			d, err := time.Parse(time.RFC3339, headerval)
+			if err != nil {
+				return err
+			}
+			s.Date = d
+			seenDate = true
+		case "tree":
+			oid, err := ParseObjectId(headerval)
+			if err != nil {
+				return err
+			}
+			s.Tree = oid
+			seenTree = true
+		}
+
+		if err == io.EOF {
+			break
+		}
+	}
+
+	if !seenContainer || !seenDate || !seenTree {
+		return errors.New("Missing container, date or tree header")
+	}
+
+	b := new(bytes.Buffer)
+	if _, err := io.Copy(b, r); err != nil {
+		return err
+	}
+
+	s.Comment = strings.TrimSpace(string(b.Bytes()))
+	return nil
+}
+
+func (a Snapshot) Equals(b Snapshot) bool {
+	return a.Tree.Equals(b.Tree) &&
+		a.Container == b.Container &&
+		a.Date.Equal(b.Date) &&
+		a.Comment == b.Comment
+}
diff --git a/objects/object_snapshot_test.go b/objects/object_snapshot_test.go
new file mode 100644
index 0000000..b610190
--- /dev/null
+++ b/objects/object_snapshot_test.go
@@ -0,0 +1,62 @@
+package objects
+
+import (
+	"bytes"
+	"testing"
+	"time"
+)
+
+var (
+	testSnapshotObj = Snapshot{
+		Comment:   "foo\nbar\nbaz!",
+		Container: "foo",
+		Date:      time.Date(2017, 07, 01, 21, 40, 00, 0, time.FixedZone("", 2*60*60)),
+		Tree:      genId(0xff),
+	}
+
+	testSnapshotSerialization = []byte("" +
+		"container foo\n" +
+		"date 2017-07-01T21:40:00+02:00\n" +
+		"tree sha3-256:ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff\n" +
+		"\n" +
+		"foo\n" +
+		"bar\n" +
+		"baz!")
+)
+
+func TestSerializeSnapshot(t *testing.T) {
+	have := testSnapshotObj.Payload()
+
+	if !bytes.Equal(have, testSnapshotSerialization) {
+		t.Errorf("Unexpected serialization result: %s", have)
+	}
+}
+
+func TestUnserializeSnapshot(t *testing.T) {
+	have := Snapshot{}
+	if err := have.FromPayload(testSnapshotSerialization); err != nil {
+		t.Fatalf("Unexpected error: %s", err)
+	}
+
+	if !have.Equals(testSnapshotObj) {
+		t.Errorf("Unexpeced unserialization result: %v", have)
+	}
+}
+
+func TestUnserializeSnapshotFailure(t *testing.T) {
+	subtests := []struct{ name, payload string }{
+		{"empty", ""},
+		{"missing tree", "container foo\ndate 2017-07-01T22:02:00+02:00\n"},
+		{"missing container", "date 2017-07-01T22:02:00+02:00\ntree sha3-256:0000000000000000000000000000000000000000000000000000000000000000\n"},
+		{"missing date", "container foo\ntree sha3-256:0000000000000000000000000000000000000000000000000000000000000000\n"},
+		{"invalid date", "container foo\ndate foobar\ntree sha3-256:0000000000000000000000000000000000000000000000000000000000000000\n"},
+	}
+
+	for _, subtest := range subtests {
+		have := Snapshot{}
+		err := have.FromPayload([]byte(subtest.payload))
+		if err == nil {
+			t.Errorf("Unexpected unserialization success: %v", have)
+		}
+	}
+}