1 files changed, 189 insertions, 0 deletions
diff --git a/bug/op_label_change.go b/bug/op_label_change.go
new file mode 100644
index 00000000..120671fb
--- /dev/null
+++ b/bug/op_label_change.go
@@ -0,0 +1,189 @@
+package bug
+
+import (
+	"fmt"
+	"sort"
+
+	"github.com/pkg/errors"
+)
+
+var _ Operation = LabelChangeOperation{}
+
+// LabelChangeOperation define a Bug operation to add or remove labels
+type LabelChangeOperation struct {
+	*OpBase
+	Added   []Label `json:"added"`
+	Removed []Label `json:"removed"`
+}
+
+func (op LabelChangeOperation) base() *OpBase {
+	return op.OpBase
+}
+
+// Apply apply the operation
+func (op LabelChangeOperation) Apply(snapshot Snapshot) 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
+}
+
+func (op LabelChangeOperation) Validate() error {
+	if err := opBaseValidate(op, LabelChangeOp); err != nil {
+		return err
+	}
+
+	for _, l := range op.Added {
+		if err := l.Validate(); err != nil {
+			return errors.Wrap(err, "added label")
+		}
+	}
+
+	for _, l := range op.Removed {
+		if err := l.Validate(); err != nil {
+			return errors.Wrap(err, "removed label")
+		}
+	}
+
+	if len(op.Added)+len(op.Removed) <= 0 {
+		return fmt.Errorf("no label change")
+	}
+
+	return nil
+}
+
+func NewLabelChangeOperation(author Person, unixTime int64, added, removed []Label) LabelChangeOperation {
+	return LabelChangeOperation{
+		OpBase:  newOpBase(LabelChangeOp, author, unixTime),
+		Added:   added,
+		Removed: removed,
+	}
+}
+
+// ChangeLabels is a convenience function to apply the operation
+func ChangeLabels(b Interface, author Person, unixTime int64, add, remove []string) ([]LabelChangeResult, error) {
+	var added, removed []Label
+	var results []LabelChangeResult
+
+	snap := b.Compile()
+
+	for _, str := range add {
+		label := Label(str)
+
+		// check for duplicate
+		if labelExist(added, label) {
+			results = append(results, LabelChangeResult{Label: label, Status: LabelChangeDuplicateInOp})
+			continue
+		}
+
+		// check that the label doesn't already exist
+		if labelExist(snap.Labels, label) {
+			results = append(results, LabelChangeResult{Label: label, Status: LabelChangeAlreadySet})
+			continue
+		}
+
+		added = append(added, label)
+		results = append(results, LabelChangeResult{Label: label, Status: LabelChangeAdded})
+	}
+
+	for _, str := range remove {
+		label := Label(str)
+
+		// check for duplicate
+		if labelExist(removed, label) {
+			results = append(results, LabelChangeResult{Label: label, Status: LabelChangeDuplicateInOp})
+			continue
+		}
+
+		// check that the label actually exist
+		if !labelExist(snap.Labels, label) {
+			results = append(results, LabelChangeResult{Label: label, Status: LabelChangeDoesntExist})
+			continue
+		}
+
+		removed = append(removed, label)
+		results = append(results, LabelChangeResult{Label: label, Status: LabelChangeRemoved})
+	}
+
+	if len(added) == 0 && len(removed) == 0 {
+		return results, fmt.Errorf("no label added or removed")
+	}
+
+	labelOp := NewLabelChangeOperation(author, unixTime, added, removed)
+
+	if err := labelOp.Validate(); err != nil {
+		return nil, err
+	}
+
+	b.Append(labelOp)
+
+	return results, nil
+}
+
+func labelExist(labels []Label, label Label) bool {
+	for _, l := range labels {
+		if l == label {
+			return true
+		}
+	}
+
+	return false
+}
+
+type LabelChangeStatus int
+
+const (
+	_ LabelChangeStatus = iota
+	LabelChangeAdded
+	LabelChangeRemoved
+	LabelChangeDuplicateInOp
+	LabelChangeAlreadySet
+	LabelChangeDoesntExist
+)
+
+type LabelChangeResult struct {
+	Label  Label
+	Status LabelChangeStatus
+}
+
+func (l LabelChangeResult) String() string {
+	switch l.Status {
+	case LabelChangeAdded:
+		return fmt.Sprintf("label %s added", l.Label)
+	case LabelChangeRemoved:
+		return fmt.Sprintf("label %s removed", l.Label)
+	case LabelChangeDuplicateInOp:
+		return fmt.Sprintf("label %s is a duplicate", l.Label)
+	case LabelChangeAlreadySet:
+		return fmt.Sprintf("label %s was already set", l.Label)
+	case LabelChangeDoesntExist:
+		return fmt.Sprintf("label %s doesn't exist on this bug", l.Label)
+	default:
+		panic(fmt.Sprintf("unknown label change status %v", l.Status))
+	}
+}