/*

 * Copyright (c) 2003, 2006, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; 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.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * 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.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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 */

package com.sun.jmx.remote.internal;

import java.util.AbstractList;

import java.util.Iterator;

public class ArrayQueue<T> extends AbstractList<T> {

    public ArrayQueue(int capacity) {

        this.capacity = capacity + 1;

        this.queue = newArray(capacity + 1);

        this.head = 0;

        this.tail = 0;

    }

    public void resize(int newcapacity) {

        int size = size();

        if (newcapacity < size)

            throw new IndexOutOfBoundsException("Resizing would lose data");

        newcapacity++;

        if (newcapacity == this.capacity)

            return;

        T[] newqueue = newArray(newcapacity);

        for (int i = 0; i < size; i++)

            newqueue[i] = get(i);

        this.capacity = newcapacity;

        this.queue = newqueue;

        this.head = 0;

        this.tail = size;

    }

    @SuppressWarnings("unchecked")

    private T[] newArray(int size) {

        return (T[]) new Object[size];

    }

    public boolean add(T o) {

        queue[tail] = o;

        int newtail = (tail + 1) % capacity;

        if (newtail == head)

            throw new IndexOutOfBoundsException("Queue full");

        tail = newtail;

        return true; // we did add something

    }

    public T remove(int i) {

        if (i != 0)

            throw new IllegalArgumentException("Can only remove head of queue");

        if (head == tail)

            throw new IndexOutOfBoundsException("Queue empty");

        T removed = queue[head];

        queue[head] = null;

        head = (head + 1) % capacity;

        return removed;

    }

    public T get(int i) {

        int size = size();

        if (i < 0 || i >= size) {

            final String msg = "Index " + i + ", queue size " + size;

            throw new IndexOutOfBoundsException(msg);

        }

        int index = (head + i) % capacity;

        return queue[index];

    }

    public int size() {

        // Can't use % here because it's not mod: -3 % 2 is -1, not +1.

        int diff = tail - head;

        if (diff < 0)

            diff += capacity;

        return diff;

    }

    private int capacity;

    private T[] queue;

    private int head;

    private int tail;

}