/*
 * Copyright (c) 2013, OpenCloudDB/MyCAT and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software;Designed and Developed mainly by many Chinese 
 * opensource volunteers. you can redistribute it and/or modify it under the 
 * terms of the GNU General Public License version 2 only, as published by the
 * Free Software Foundation.
 *
 * This code 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 GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 * 
 * Any questions about this component can be directed to it's project Web address 
 * https://code.google.com/p/opencloudb/.
 *
 */
package org.opencloudb.buffer;

import java.nio.ByteBuffer;
import java.util.ArrayList;
import java.util.concurrent.locks.ReentrantLock;

import org.apache.log4j.Logger;

/**
 * @author mycat
 */
public final class BufferPool {
	private static final Logger LOGGER = Logger.getLogger(BufferPool.class);
	private final int chunkSize;
	private final ByteBuffer[] items;
	private final ReentrantLock lock;
	private int putIndex;
	private int takeIndex;
	private int count;
	private volatile int newCount;

	public BufferPool(int bufferSize, int chunkSize) {
		this.chunkSize = chunkSize;
		int capacity = bufferSize / chunkSize;
		capacity = (bufferSize % chunkSize == 0) ? capacity : capacity + 1;
		this.items = new ByteBuffer[capacity];
		this.lock = new ReentrantLock();
		for (int i = 0; i < capacity; i++) {
			insert(createDirectBuffer(chunkSize));
		}
	}

	public int capacity() {
		return items.length;
	}

	public int size() {
		return count;
	}

	public int getNewCount() {
		return newCount;
	}

	public ByteBuffer allocate() {
		ByteBuffer node = null;
		final ReentrantLock lock = this.lock;
		lock.lock();
		try {
			node = (count == 0) ? null : extract();
		} finally {
			lock.unlock();
		}
		if (node == null) {
			++newCount;
			LOGGER.warn("pool is full ,allocate tempory buffer ,total alloccated times:"
					+ newCount);
			return createTempBuffer(chunkSize);
		} else {
			return node;
		}
	}

	/**
	 * check if buffer already recycled ,only used when not sure if a buffer
	 * already recycled
	 * 
	 * @param buffer
	 */
	public void safeRecycle(ByteBuffer buffer) {
		checkValidBuffer(buffer);
		final boolean debug = LOGGER.isDebugEnabled();
		final ReentrantLock lock = this.lock;
		lock.lock();
		try {
			if (testIfDuplicate(buffer)) {
				if (debug) {
					LOGGER.debug("already recycled buffer ");
				}
				return;
			}
			recycleBuffer(buffer);
		} finally {
			lock.unlock();
		}
	}

	private void checkValidBuffer(ByteBuffer buffer) {
		// 拒绝回收null和容量大于chunkSize的缓存
		if (buffer == null || !buffer.isDirect()) {
			return;
		} else if (buffer.capacity() > chunkSize) {
			buffer.clear();
			LOGGER.warn("cant' recycle  a buffer large than my pool chunksize "
					+ buffer.capacity());
			return;
		}
	}

	public void recycle(ByteBuffer buffer) {
		checkValidBuffer(buffer);
		recycleBuffer(buffer);
	}

	private void recycleBuffer(ByteBuffer buffer) {
		final ReentrantLock lock = this.lock;
		lock.lock();
		try {
			// reportDuplicate(buffer);
			if (count != items.length) {
				buffer.clear();
				insert(buffer);

			} else {
				if (LOGGER.isDebugEnabled()) {
					LOGGER.debug("can't recycle  buffer ,pool is full ");
				}

			}
		} finally {
			lock.unlock();
		}
	}

	private void insert(ByteBuffer buffer) {
		items[putIndex] = buffer;

		putIndex = inc(putIndex);
		++count;

	}

	public boolean testIfDuplicate(ByteBuffer buffer) {
		for (ByteBuffer exists : items) {
			if (exists == buffer) {
				return true;
			}
		}
		return false;

	}

	private ByteBuffer extract() {
		final ByteBuffer[] items = this.items;
		ByteBuffer item = items[takeIndex];
		items[takeIndex] = null;
		takeIndex = inc(takeIndex);
		--count;
		return item;
	}

	private int inc(int i) {
		return (++i == items.length) ? 0 : i;
	}

	private ByteBuffer createTempBuffer(int size) {
		return ByteBuffer.allocate(size);
	}

	private ByteBuffer createDirectBuffer(int size) {
		// for performance
		return ByteBuffer.allocateDirect(size);
	}

	public ByteBuffer allocate(int size) {
		if (size <= this.chunkSize) {
			return allocate();
		} else {
			LOGGER.warn("allocate buffer size large than default chunksize:"
					+ this.chunkSize + " he want " + size);
			return createTempBuffer(size);
		}
	}

	public static void main(String[] args) {
		BufferPool pool = new BufferPool(1024 * 5, 1024);
		int i = pool.capacity();
		ArrayList<ByteBuffer> all = new ArrayList<ByteBuffer>();
		for (int j = 0; j <= i; j++) {
			all.add(pool.allocate());
		}
		for (ByteBuffer buf : all) {
			pool.recycle(buf);
		}
		System.out.println(pool.size());
	}
}