1 files changed, 56 insertions, 0 deletions
diff --git a/bug/operations/label_change.go b/bug/operations/label_change.go
new file mode 100644
index 00000000..ca07f6f5
--- /dev/null
+++ b/bug/operations/label_change.go
@@ -0,0 +1,56 @@
+package operations
+
+import (
+	"github.com/MichaelMure/git-bug/bug"
+	"sort"
+)
+
+// LabelChangeOperation will add or remove a set of labels
+
+var _ bug.Operation = LabelChangeOperation{}
+
+type LabelChangeOperation struct {
+	bug.OpBase
+	Added   []bug.Label
+	Removed []bug.Label
+}
+
+func NewLabelChangeOperation(author bug.Person, added, removed []bug.Label) LabelChangeOperation {
+	return LabelChangeOperation{
+		OpBase:  bug.NewOpBase(bug.LabelChangeOp, author),
+		Added:   added,
+		Removed: removed,
+	}
+}
+
+func (op LabelChangeOperation) Apply(snapshot bug.Snapshot) bug.Snapshot {
+	// Add in the set
+AddLoop:
+	for _, added := range op.Added {
+		for _, label := range snapshot.Labels {
+			if label == added {
+				// Already exist
+				continue AddLoop
+			}
+		}
+
+		snapshot.Labels = append(snapshot.Labels, added)
+	}
+
+	// Remove in the set
+	for _, removed := range op.Removed {
+		for i, label := range snapshot.Labels {
+			if label == removed {
+				snapshot.Labels[i] = snapshot.Labels[len(snapshot.Labels)-1]
+				snapshot.Labels = snapshot.Labels[:len(snapshot.Labels)-1]
+			}
+		}
+	}
+
+	// Sort
+	sort.Slice(snapshot.Labels, func(i, j int) bool {
+		return string(snapshot.Labels[i]) < string(snapshot.Labels[j])
+	})
+
+	return snapshot
+}