/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.apache.bookkeeper.util;

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import org.apache.bookkeeper.client.ITopologyAwareEnsemblePlacementPolicy;
import org.apache.bookkeeper.client.RackChangeNotifier;
import org.apache.bookkeeper.net.AbstractDNSToSwitchMapping;
import org.apache.bookkeeper.net.BookieId;
import org.apache.bookkeeper.net.BookieNode;
import org.apache.bookkeeper.net.BookieSocketAddress;
import org.apache.bookkeeper.net.DNSToSwitchMapping;
import org.apache.bookkeeper.net.NetworkTopology;
import org.apache.bookkeeper.net.NodeBase;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Implements {@link DNSToSwitchMapping} via static mappings. Used in test cases to simulate racks.
 */
public class StaticDNSResolver extends AbstractDNSToSwitchMapping implements RackChangeNotifier {

    static final Logger LOG = LoggerFactory.getLogger(StaticDNSResolver.class);

    private static final ConcurrentMap<String, String> name2Racks = new ConcurrentHashMap<String, String>();

    public static void addNodeToRack(String name, String rack) {
        name2Racks.put(name, rack);
        if (LOG.isDebugEnabled()) {
            LOG.debug("Add node {} to rack {}.", name, rack);
        }
    }

    public static String getRack(String name) {
        String rack = name2Racks.get(name);
        if (null == rack) {
            rack = NetworkTopology.DEFAULT_REGION_AND_RACK;
        }
        return rack;
    }

    public static String getRegion(String name) {
        String[] parts = getRack(name).split(NodeBase.PATH_SEPARATOR_STR);
        if (parts.length <= 1) {
            return NetworkTopology.DEFAULT_REGION;
        } else {
            return parts[1];
        }
    }

    public static void reset() {
        name2Racks.clear();
    }

    @Override
    public List<String> resolve(List<String> names) {
        if (getBookieAddressResolver() == null) {
            // test that this instance has been properly initialized
            throw new IllegalStateException("bookieAddressResolver was not set");
        }
        List<String> racks = new ArrayList<String>();
        for (String n : names) {
            String rack = name2Racks.get(n);
            if (LOG.isDebugEnabled()) {
                LOG.debug("Resolve name {} to rack {}.", n, rack);
            }
            racks.add(rack);
        }
        return racks;
    }

    @Override
    public void reloadCachedMappings() {
        // nop
    }

    private static ITopologyAwareEnsemblePlacementPolicy<BookieNode> rackawarePolicy = null;

    @Override
    public void registerRackChangeListener(ITopologyAwareEnsemblePlacementPolicy<BookieNode> rackawareEnsemblePolicy) {
        rackawarePolicy = rackawareEnsemblePolicy;
    }

    public static void changeRack(List<BookieSocketAddress> bookieAddressList, List<String> rack) {
        List<BookieId> bookieIds = new ArrayList<>();
        for (int i = 0; i < bookieAddressList.size(); i++) {
            BookieSocketAddress bkAddress = bookieAddressList.get(i);
            name2Racks.put(bkAddress.getHostName(), rack.get(i));
            bookieIds.add(bkAddress.toBookieId());
        }
        rackawarePolicy.onBookieRackChange(bookieIds);
    }
}