/*
 * Copyright (c) 2012 Big Switch Networks, Inc.
 *
 * Licensed under the Eclipse Public License, Version 1.0 (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.eclipse.org/legal/epl-v10.html
 *
 * 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.
 *
 * This file incorporates work covered by the following copyright and
 * permission notice:
 *
 *    Originally created by David Erickson, Stanford University
 *
 *    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.opendaylight.controller.hosttracker.internal;

import java.util.Collection;
import java.util.EnumSet;
import java.util.Iterator;

import org.opendaylight.controller.hosttracker.Entity;
import org.opendaylight.controller.hosttracker.IDeviceService.DeviceField;

/**
 * An index that maps key fields of an entity to device keys
 */
public abstract class DeviceIndex {
    /**
     * The key fields for this index
     */
    protected EnumSet<DeviceField> keyFields;

    /**
     * Construct a new device index using the provided key fields
     *
     * @param keyFields
     *            the key fields to use
     */
    public DeviceIndex(EnumSet<DeviceField> keyFields) {
        super();
        this.keyFields = keyFields;
    }

    /**
     * Find all device keys in the index that match the given entity on all the
     * key fields for this index
     *
     * @param e
     *            the entity to search for
     * @return an iterator over device keys
     */
    public abstract Iterator<Long> queryByEntity(Entity entity);

    /**
     * Get all device keys in the index. If certain devices exist multiple
     * times, then these devices may be returned multiple times
     *
     * @return an iterator over device keys
     */
    public abstract Iterator<Long> getAll();

    /**
     * Attempt to update an index with the entities in the provided
     * {@link Device}. If the update fails because of a concurrent update, will
     * return false.
     *
     * @param device
     *            the device to update
     * @param deviceKey
     *            the device key for the device
     * @return true if the update succeeded, false otherwise.
     */
    public abstract boolean updateIndex(Device device, Long deviceKey);

    /**
     * Add a mapping from the given entity to the given device key. This update
     * will not fail because of a concurrent update
     *
     * @param device
     *            the device to update
     * @param deviceKey
     *            the device key for the device
     */
    public abstract void updateIndex(Entity entity, Long deviceKey);

    /**
     * Remove the entry for the given entity
     *
     * @param entity
     *            the entity to remove
     */
    public abstract void removeEntity(Entity entity);

    /**
     * Remove the given device key from the index for the given entity
     *
     * @param entity
     *            the entity to search for
     * @param deviceKey
     *            the key to remove
     */
    public abstract void removeEntity(Entity entity, Long deviceKey);

    /**
     * Remove the give device from the index only if this the collection of
     * others does not contain an entity that is identical on all the key fields
     * for this index.
     *
     * @param entity
     *            the entity to search for
     * @param deviceKey
     *            the key to remove
     * @param others
     *            the others against which to check
     */
    public void removeEntityIfNeeded(Entity entity, Long deviceKey,
            Collection<Entity> others) {
        IndexedEntity ie = new IndexedEntity(keyFields, entity);
        for (Entity o : others) {
            IndexedEntity oio = new IndexedEntity(keyFields, o);
            if (oio.equals(ie))
                return;
        }

        Iterator<Long> keyiter = this.queryByEntity(entity);
        while (keyiter.hasNext()) {
            Long key = keyiter.next();
            if (key.equals(deviceKey)) {
                removeEntity(entity, deviceKey);
                break;
            }
        }
    }

}