/*******************************************************************************
 *
 * Copyright (c) 2004-2009 Oracle Corporation.
 *
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 * 
 *    Kohsuke Kawaguchi
 *
 *
 *******************************************************************************/ 

package hudson.util;

import java.util.AbstractList;
import java.util.List;
import java.util.logging.Handler;
import java.util.logging.LogRecord;

/**
 * Log {@link Handler} that stores the log records into a ring buffer.
 *
 * @author Kohsuke Kawaguchi
 */
public class RingBufferLogHandler extends Handler {

    private int start = 0;
    private final LogRecord[] records;
    private volatile int size = 0;

    public RingBufferLogHandler() {
        this(256);
    }

    public RingBufferLogHandler(int ringSize) {
        records = new LogRecord[ringSize];
    }

    public synchronized void publish(LogRecord record) {
        int len = records.length;
        records[(start + size) % len] = record;
        if (size == len) {
            start++;
        } else {
            size++;
        }
    }

    /**
     * Returns the list view of {@link LogRecord}s in the ring buffer.
     *
     * <p> New records are always placed early in the list.
     */
    public List<LogRecord> getView() {
        return new AbstractList<LogRecord>() {
            public LogRecord get(int index) {
                // flip the order
                synchronized (RingBufferLogHandler.this) {
                    return records[(start + (size - (index + 1))) % records.length];
                }
            }

            public int size() {
                return size;
            }
        };
    }

    // noop
    public void flush() {
    }

    public void close() throws SecurityException {
    }
}