/*
 * Copyright 2013 The Netty Project
 *
 * The Netty Project 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.ignite.internal.util.nio;

import java.nio.channels.SelectionKey;
import java.util.AbstractSet;
import java.util.Iterator;

/**
 *
 */
final class SelectedSelectionKeySet extends AbstractSet<SelectionKey> {
    /** */
    private SelectionKey[] keysA;

    /** */
    private int keysASize;

    /** */
    private SelectionKey[] keysB;

    /** */
    private int keysBSize;

    /** */
    private boolean isA = true;

    /**
     *
     */
    SelectedSelectionKeySet() {
        keysA = new SelectionKey[1024];
        keysB = keysA.clone();
    }

    /** {@inheritDoc} */
    @Override public boolean add(SelectionKey o) {
        if (o == null)
            return false;

        if (isA) {
            int size = keysASize;
            keysA[size++] = o;
            keysASize = size;
            if (size == keysA.length)
                doubleCapacityA();
        }
        else {
            int size = keysBSize;
            keysB[size++] = o;
            keysBSize = size;
            if (size == keysB.length)
                doubleCapacityB();
        }

        return true;
    }

    /**
     *
     */
    private void doubleCapacityA() {
        SelectionKey[] newKeysA = new SelectionKey[keysA.length << 1];
        System.arraycopy(keysA, 0, newKeysA, 0, keysASize);
        keysA = newKeysA;
    }

    /**
     *
     */
    private void doubleCapacityB() {
        SelectionKey[] newKeysB = new SelectionKey[keysB.length << 1];
        System.arraycopy(keysB, 0, newKeysB, 0, keysBSize);
        keysB = newKeysB;
    }

    /**
     * @return Selection keys.
     */
    SelectionKey[] flip() {
        if (isA) {
            isA = false;
            keysA[keysASize] = null;
            keysBSize = 0;
            return keysA;
        }
        else {
            isA = true;
            keysB[keysBSize] = null;
            keysASize = 0;
            return keysB;
        }
    }

    /** {@inheritDoc} */
    @Override public int size() {
        if (isA)
            return keysASize;
        else
            return keysBSize;
    }

    /** {@inheritDoc} */
    @Override public boolean remove(Object o) {
        return false;
    }

    /** {@inheritDoc} */
    @Override public boolean contains(Object o) {
        return false;
    }

    /** {@inheritDoc} */
    @Override public Iterator<SelectionKey> iterator() {
        throw new UnsupportedOperationException();
    }
}
