/*
 *
 * 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.proto;

import java.util.concurrent.atomic.AtomicLong;

import org.apache.bookkeeper.net.BookieSocketAddress;
import org.apache.bookkeeper.proto.BookkeeperInternalCallbacks.GenericCallback;
import org.apache.bookkeeper.util.MathUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.concurrent.atomic.AtomicInteger;
import com.google.common.base.Preconditions;

/**
 *  Provide a simple round-robin style channel pool. We could improve it later to do more
 *  fantastic things.
 */
class DefaultPerChannelBookieClientPool implements PerChannelBookieClientPool,
        GenericCallback<PerChannelBookieClient> {

    static final Logger logger = LoggerFactory.getLogger(DefaultPerChannelBookieClientPool.class);

    final PerChannelBookieClientFactory factory;
    final BookieSocketAddress address;
    final PerChannelBookieClient[] clients;
    final AtomicInteger counter = new AtomicInteger(0);
    final AtomicLong errorCounter = new AtomicLong(0);

    DefaultPerChannelBookieClientPool(PerChannelBookieClientFactory factory,
                                      BookieSocketAddress address,
                                      int coreSize) {
        Preconditions.checkArgument(coreSize > 0);
        this.factory = factory;
        this.address = address;
        this.clients = new PerChannelBookieClient[coreSize];
        for (int i = 0; i < coreSize; i++) {
            this.clients[i] = factory.create(address, this);
        }
    }

    @Override
    public void operationComplete(int rc, PerChannelBookieClient pcbc) {
        // nop
    }

    @Override
    public void intialize() {
        for (PerChannelBookieClient pcbc : this.clients) {
            pcbc.connectIfNeededAndDoOp(this);
        }
    }

    @Override
    public void obtain(GenericCallback<PerChannelBookieClient> callback) {
        if (1 == clients.length) {
            clients[0].connectIfNeededAndDoOp(callback);
            return;
        }
        int idx = MathUtils.signSafeMod(counter.getAndIncrement(), clients.length);
        clients[idx].connectIfNeededAndDoOp(callback);
    }

    @Override
    public void recordError() {
        errorCounter.incrementAndGet();
    }

    @Override
    public void disconnect(boolean wait) {
        for (PerChannelBookieClient pcbc : clients) {
            pcbc.disconnect(wait);
        }
    }

    @Override
    public void close(boolean wait) {
        for (PerChannelBookieClient pcbc : clients) {
            pcbc.close(wait);
        }
    }
}