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/*
 * Copyright 2008-2012 Sergey Skladchikov
 *
 * 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 org.gwt.advanced.client.datamodel;

import java.util.Collections;
import java.util.HashMap;
import java.util.Map;

/**
 * This is a model event that is sent by the {@link org.gwt.advanced.client.datamodel.ListDataModel} implementations
 * if anything is changed in encapsulated data.
 *
 * @author Sergey Skladchikov
 * @since 1.4.9
 */
public class ListModelEvent {
    /** item added */
    public static final EventType ADD_ITEM = new EventType();
    /** item removed */
    public static final EventType REMOVE_ITEM = new EventType();
    /** all data removed */
    public static final EventType CLEAN = new EventType();
    /** item selected */
    public static final EventType SELECT_ITEM = new EventType();

    /** it's a data model that produced the event */
    private ListDataModel source;
    /** it's list of attached item indexes mapped to their IDs */
    private Map itemIndexes;
    /** type of the event */
    private EventType type;

    /**
     * Creates an instance of this class.
     * Mostly applicable for types like {@link #CLEAN} which don't require to specify a concrete item.
     *
     * @param source is a data model produced this event.
     * @param type   is an event type.
     */
    public ListModelEvent(ListDataModel source, EventType type) {
        this(source, new HashMap(), type);
    }

    /**
     * Creates an instance of this class.

     * Mostly applicable for types like {@link #ADD_ITEM}, {@link #REMOVE_ITEM} or {@link #SELECT_ITEM}
     * which require to specify a concrete item.
     *
     * @param source    is a data model produced this event.
     * @param itemId    is a related item ID.
     * @param itemIndex is a related item index (usually index of the item identified with itemId.
     * @param type      is an event type.
     */
    public ListModelEvent(ListDataModel source, String itemId, int itemIndex, EventType type) {
        this(source, new HashMap(), type);
        this.itemIndexes.put(itemId, itemIndex);
    }

    /**
     * Creates an instance of this class.

     * Mostly applicable for types like {@link #ADD_ITEM}, {@link #REMOVE_ITEM} or {@link #SELECT_ITEM}
     * which require to specify a concrete item.

     * use this constructor if you want to notify listeners about bulk model update.
     *
     * @param source      is a data model produced this event.
     * @param itemIndexes is a list of indexes mapped to their IDs. It must contain items which were affected by
     *                    model change.
     * @param type        is an event type.
     */
    public ListModelEvent(ListDataModel source, Map itemIndexes, EventType type) {
        this.source = source;
        this.itemIndexes = itemIndexes;
        this.type = type;
    }

    /**
     * Gets an event source data model.
     *
     * @return a list data model.
     */
    public ListDataModel getSource() {
        return source;
    }

    /**
     * Gets a related item ID.

     * Might be equal to null for those events which are not related to a concrete item.

     * If there are several affected items it gets an ID of the first one.
     *
     * @return an item ID.
     */
    public String getItemId() {
        return itemIndexes.isEmpty() ? null : itemIndexes.keySet().iterator().next();
    }

    /**
     * Gets a related item index.

     * Might be equal to -1 for those events which are not related to a concrete item.

     * If there are several affected items it gets an ID of the first one.
     *
     * @return an item ID.
     */
    public int getItemIndex() {
        return itemIndexes.isEmpty() ? -1 : itemIndexes.values().iterator().next();
    }

    /**
     * This method gets a map of affected item indexes mapped to their IDs.
     *
     * @return a map of item indexes with IDs.
     */
    public Map getItemIndexes() {
        return Collections.unmodifiableMap(itemIndexes);
    }

    /**
     * Gets an event type that specifies what exactly happened.
     *
     * @return an event type.
     */
    public EventType getType() {
        return type;
    }

    /**
     * Event type class
     * It's in use because older versions of GWT don't support enums.
     */
    protected static class EventType {
        /** See class docs */
        protected EventType() {
        }
    }
}