rocks.xmpp.extensions.disco.DefaultItemProvider Maven / Gradle / Ivy

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/*
 * The MIT License (MIT)
 *
 * Copyright (c) 2014-2016 Christian Schudt
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

package rocks.xmpp.extensions.disco;

import rocks.xmpp.extensions.disco.model.items.Item;
import rocks.xmpp.extensions.rsm.ResultSetProvider;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
import java.util.ListIterator;
import java.util.Objects;

/**
 * A default item provider for Service Discovery. When items are requested via Service Discovery, this class provides the items
 * and if requested with Result Set Management, it also takes care of providing the correct number of items or the total count of items.
 * 
 * This class is a view on a collection, if the underlying collection changes, the view on the collection will yield different results.
 *
 * @author Christian Schudt
 * @see XEP-0030: Service Discovery 4.2 Items Nodes
 * @see XEP-0059: Result Set Management 3. Examples
 */
public final class DefaultItemProvider implements ResultSetProvider {

    private final Collection items;

    public DefaultItemProvider(Collection items) {
        this.items = Objects.requireNonNull(items);
    }

    @Override
    public List getItems() {
        return Collections.unmodifiableList(new ArrayList<>(items));
    }

    @Override
    public int getItemCount() {
        return items.size();
    }

    @Override
    public List getItems(int index, int maxSize) {
        int toIndex = index + maxSize;
        synchronized (items) {
            if (index < 0 || toIndex > items.size() || index > toIndex) {
                return Collections.emptyList();
            }
            return Collections.unmodifiableList(new ArrayList<>(items).subList(index, toIndex));
        }
    }

    @Override
    public List getItemsAfter(String itemId, int maxSize) {
        return getItems(indexOf(itemId) + 1, maxSize);
    }

    @Override
    public List getItemsBefore(String itemId, int maxSize) {
        return getItems(indexOf(itemId) - maxSize, maxSize);
    }

    @Override
    public int indexOf(String itemId) {
        Objects.requireNonNull(itemId);
        synchronized (items) {
            ListIterator itemIterator = new ArrayList<>(items).listIterator();
            while (itemIterator.hasNext()) {
                Item item = itemIterator.next();
                if (item != null && itemId.equals(item.getId())) {
                    return itemIterator.previousIndex();
                }
            }
        }
        return -1;
    }
}