/*
 * Copyright 2000-2016 Vaadin Ltd.
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */
package com.vaadin.client;

import java.io.Serializable;
import java.util.List;

import com.google.gwt.event.shared.EventHandler;
import com.google.gwt.event.shared.GwtEvent;
import com.vaadin.client.ConnectorHierarchyChangeEvent.ConnectorHierarchyChangeHandler;
import com.vaadin.client.communication.AbstractServerConnectorEvent;
import com.vaadin.client.ui.AbstractHasComponentsConnector;

/**
 * Event for containing data related to a change in the {@link ServerConnector}
 * hierarchy. A {@link ConnectorHierarchyChangedEvent} is fired when an update
 * from the server has been fully processed and all hierarchy updates have been
 * completed.
 *
 * @author Vaadin Ltd
 * @since 7.0.0
 *
 */
public class ConnectorHierarchyChangeEvent
        extends AbstractServerConnectorEvent<ConnectorHierarchyChangeHandler> {
    /**
     * Type of this event, used by the event bus.
     */
    public static final Type<ConnectorHierarchyChangeHandler> TYPE = new Type<>();

    List<ComponentConnector> oldChildren;

    public ConnectorHierarchyChangeEvent() {
    }

    /**
     * Returns a collection of the old children for the connector. This was the
     * state before the update was received from the server.
     *
     * @return A collection of old child connectors. Never returns null.
     */
    public List<ComponentConnector> getOldChildren() {
        return oldChildren;
    }

    /**
     * Sets the collection of the old children for the connector.
     *
     * @param oldChildren
     *            The old child connectors. Must not be null.
     */
    public void setOldChildren(List<ComponentConnector> oldChildren) {
        this.oldChildren = oldChildren;
    }

    /**
     * Returns the {@link HasComponentsConnector} for which this event occurred.
     *
     * @return The {@link HasComponentsConnector} whose child collection has
     *         changed. Never returns null.
     */
    public HasComponentsConnector getParent() {
        return (HasComponentsConnector) getConnector();
    }

    @Override
    public void setConnector(ServerConnector connector) {
        assert connector instanceof HasComponentsConnector : "A ConnectorHierarchyChangeEvent "
                + "can only occur for connectors implementing HasComponentsConnector. "
                + connector.getClass().getName() + " does not";

        super.setConnector(connector);
    }

    /**
     * Handles connector hierarchy events. You should typically not directly
     * implement this interface, but instead make your connector class extend
     * {@link AbstractHasComponentsConnector} or an appropriate subclass.
     */
    public interface ConnectorHierarchyChangeHandler
            extends Serializable, EventHandler {
        /**
         * Called by the framework when the list of child components of the
         * connector implementing this interface has changed. The implementation
         * is responsible for attaching the widgets of any new children and
         * detaching the widgets of any removed children. Implementations should
         * typically also make sure that the child widgets are attached
         * according to the ordering of the child components.
         * <p>
         * This method is called after the shared state and hierarchy data (i.e.
         * {@link AbstractHasComponentsConnector#setChildComponents(List)}) been
         * updated for all affected connectors, but before updating captions,
         * firing state change events, invoking updateFromUIDL for legacy
         * connectors, invoking RPC and starting the layout phase.
         * <p>
         * Please note that hierarchy change events are fired in a
         * non-deterministic order when a message from the server causes
         * multiple parts of the hierarchy to change. This means that the old
         * parent connector might not yet have detached a child widget and that
         * the widget of a removed child might already have been attached by its
         * new parent.
         *
         * @param connectorHierarchyChangeEvent
         *            the event with information about the hierarchy change
         */
        public void onConnectorHierarchyChange(
                ConnectorHierarchyChangeEvent connectorHierarchyChangeEvent);
    }

    @Override
    public void dispatch(ConnectorHierarchyChangeHandler handler) {
        handler.onConnectorHierarchyChange(this);
    }

    @Override
    public GwtEvent.Type<ConnectorHierarchyChangeHandler> getAssociatedType() {
        return TYPE;
    }

}