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/*
 * Copyright (C) 2020 Graylog, Inc.
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the Server Side Public License, version 1,
 * as published by MongoDB, Inc.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * Server Side Public License for more details.
 *
 * You should have received a copy of the Server Side Public License
 * along with this program. If not, see
 * .
 */
package org.graylog2.plugin.buffers;

import com.lmax.disruptor.BlockingWaitStrategy;
import com.lmax.disruptor.BusySpinWaitStrategy;
import com.lmax.disruptor.RingBuffer;
import com.lmax.disruptor.SleepingWaitStrategy;
import com.lmax.disruptor.WaitStrategy;
import com.lmax.disruptor.YieldingWaitStrategy;
import org.graylog2.plugin.Message;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * @author Lennart Koopmann 
 */
public abstract class Buffer implements EventBuffer {
    private static final Logger log = LoggerFactory.getLogger(Buffer.class);

    protected RingBuffer ringBuffer;
    protected int ringBufferSize;

    @Override
    public boolean isEmpty() {
        return getUsage() == 0;
    }

    public long getRemainingCapacity() {
        return ringBuffer.remainingCapacity();
    }

    public int getRingBufferSize() {
        return ringBufferSize;
    }

    @Override
    public long getUsage() {
        if (ringBuffer == null) {
            return 0;
        }
        return (long) ringBuffer.getBufferSize() - ringBuffer.remainingCapacity();
    }

    protected void insert(Message message) {
        long sequence = ringBuffer.next();
        MessageEvent event = ringBuffer.get(sequence);
        event.setMessage(message);
        ringBuffer.publish(sequence);

        afterInsert(1);

    }

    protected WaitStrategy getWaitStrategy(String waitStrategyName, String configOptionName) {
        switch (waitStrategyName) {
            case "sleeping":
                return new SleepingWaitStrategy();
            case "yielding":
                return new YieldingWaitStrategy();
            case "blocking":
                return new BlockingWaitStrategy();
            case "busy_spinning":
                return new BusySpinWaitStrategy();
            default:
                log.warn("Invalid setting for [{}]:"
                                + " Falling back to default: BlockingWaitStrategy.", configOptionName);
                return new BlockingWaitStrategy();
        }
    }

    protected abstract void afterInsert(int n);

    protected void insert(Message[] messages) {
        int length = messages.length;
        long hi = ringBuffer.next(length);
        long lo = hi - (length - 1);
        for (long sequence = lo; sequence <= hi; sequence++) {
            MessageEvent event = ringBuffer.get(sequence);
            event.setMessage(messages[(int)(sequence - lo)]);
        }
        ringBuffer.publish(lo, hi);
        afterInsert(length);
    }
}