/*
 * 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.kafka.common.network;

import org.apache.kafka.common.KafkaException;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.IOException;
import java.nio.channels.GatheringByteChannel;
import java.util.Iterator;
import java.util.List;

/**
 * A set of composite sends, sent one after another
 */

public class MultiSend implements Send {

    private static final Logger log = LoggerFactory.getLogger(MultiSend.class);

    private final String dest;
    private final Iterator<Send> sendsIterator;
    private final long size;

    private long totalWritten = 0;
    private Send current;

    public MultiSend(String dest, List<Send> sends) {
        this.dest = dest;
        this.sendsIterator = sends.iterator();
        nextSendOrDone();
        long size = 0;
        for (Send send : sends)
            size += send.size();
        this.size = size;
    }

    @Override
    public long size() {
        return size;
    }

    @Override
    public String destination() {
        return dest;
    }

    @Override
    public boolean completed() {
        return current == null;
    }

    @Override
    public long writeTo(GatheringByteChannel channel) throws IOException {
        if (completed())
            throw new KafkaException("This operation cannot be invoked on a complete request.");

        int totalWrittenPerCall = 0;
        boolean sendComplete;
        do {
            long written = current.writeTo(channel);
            totalWrittenPerCall += written;
            sendComplete = current.completed();
            if (sendComplete)
                nextSendOrDone();
        } while (!completed() && sendComplete);

        totalWritten += totalWrittenPerCall;

        if (completed() && totalWritten != size)
            log.error("mismatch in sending bytes over socket; expected: " + size + " actual: " + totalWritten);

        log.trace("Bytes written as part of multi-send call: {}, total bytes written so far: {}, expected bytes to write: {}",
                totalWrittenPerCall, totalWritten, size);

        return totalWrittenPerCall;
    }

    private void nextSendOrDone() {
        if (sendsIterator.hasNext())
            current = sendsIterator.next();
        else
            current = null;
    }
}