private Action<?> walk(AmObject cobj) {
Action<?> action = visitor.preorderVisit(cobj, context);
if (action == null) action = Action.next();
final AmObject walkObj = extractWalkObject(cobj, action);
if (walkObj != null) {
// walk children
UpdatingIterator it = getChildrenOf(walkObj);
context.getAmParents().addLast(walkObj);
while (it.hasNext()) {
AmObject child = it.next();
Action<?> childAction = walk(child);
processAction(childAction, it);
}
context.getAmParents().removeLast();
}
Action<?> postAction =
visitor.postorderVisit(walkObj != null ? walkObj : cobj, context, action);
if (postAction == null) postAction = Action.next;
action = action.mergeWith(postAction);
return action;
}
private void processAction(Action<?> action, UpdatingIterator parentIterator) {
if (action.act == Action.Act.next || action.act == Action.Act.nextSibling) {
// do nothing
} else if (action.act == Action.Act.remove) {
parentIterator.remove();
} else if (action.act == Action.Act.replace) {
AmObject replacement = action.getReplaceWith();
parentIterator.set(replacement);
} else throw new AssertionError(action);
}
@Nullable
private AmObject extractWalkObject(AmObject amObject, Action<?> result) {
if (result.act == Action.Act.next) {
return amObject;
} else if (result.act == Action.Act.nextSibling) {
return null;
} else if (result.act == Action.Act.remove) {
return null;
} else if (result.act == Action.Act.replace) {
return result.getReplaceWith();
} else throw new AssertionError(result);
}
public static <T extends AmObject> Action<T> replaceWith(T replacement) {
Action<T> result = new Action<>(Act.replace);
result.replaceWith = replacement;
return result;
}