Properly handle clear ack events

internal/incident/incident.go

@@ -147,7 +147,7 @@ func (i *Incident) ProcessEvent(ctx context.Context, ev *event.Event) error {
 		return errors.New("can't insert incident event to the database")
 	}
 
-	if ev.Type == event.TypeAcknowledgementSet {
+	if ev.Type == event.TypeAcknowledgementSet || ev.Type == event.TypeAcknowledgementCleared {
 		if err = i.processAcknowledgementEvent(ctx, tx, ev); err != nil {
 			return err
 		}
@@ -592,32 +592,49 @@ func (i *Incident) notifyContact(contact *recipient.Contact, ev *event.Event, ch
 }
 
 // processAcknowledgementEvent processes the given ack event.
-// Promotes the ack author to incident.RoleManager if it's not already the case and generates a history entry.
+// This function promotes/demotes the ack author to incident.RoleManager/incident.RoleSubscriber based the provided
+// event type, if it's not already the case and generates a history entry.
 // Returns error on database failure.
 func (i *Incident) processAcknowledgementEvent(ctx context.Context, tx *sqlx.Tx, ev *event.Event) error {
 	contact := i.runtimeConfig.GetContact(ev.Username)
 	if contact == nil {
-		i.logger.Warnw("Ignoring acknowledgement event from an unknown author", zap.String("author", ev.Username))
+		i.logger.Warnw("Ignoring (clear) acknowledgement event from an unknown author", zap.String("author", ev.Username))
 
-		return fmt.Errorf("unknown acknowledgment author %q", ev.Username)
+		return fmt.Errorf("unknown (clear) acknowledgment author %q", ev.Username)
 	}
 
 	recipientKey := recipient.ToKey(contact)
 	state := i.Recipients[recipientKey]
-	oldRole := RoleNone
-	newRole := RoleManager
-	if state != nil {
-		oldRole = state.Role
 
-		if oldRole == RoleManager {
-			// The user is already a manager
-			return nil
+	var newRole, oldRole ContactRole
+	switch ev.Type {
+	case event.TypeAcknowledgementSet:
+		oldRole = RoleNone
+		newRole = RoleManager
+		if state != nil {
+			oldRole = state.Role
+
+			if oldRole == RoleManager {
+				// The user is already a manager
+				i.logger.Debugw("Ignoring acknowledgement set event, object already acknowledged", zap.String("author", contact.String()))
+
+				return errors.New("duplicate acknowledgement")
+			}
+		} else {
+			i.Recipients[recipientKey] = &RecipientState{Role: newRole}
+		}
+	case event.TypeAcknowledgementCleared:
+		if state == nil || state.Role < RoleManager {
+			i.logger.Warnw("Ignoring clear acknowledgement event, no acknowledgement found", zap.String("author", contact.String()))
+
+			return errors.New("cannot clear non-existent acknowledgement")
 		}
-	} else {
-		i.Recipients[recipientKey] = &RecipientState{Role: newRole}
+
+		oldRole = state.Role
+		newRole = RoleSubscriber
 	}
 
-	i.logger.Infof("Contact %q role changed from %s to %s", contact.String(), oldRole.String(), newRole.String())
+	i.logger.Infof("Contact %q role changed from %q to %q", contact.String(), oldRole.String(), newRole.String())
 
 	hr := &HistoryRow{
 		Key:              recipientKey,