/*
 * Copyright (c) 2016, 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
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */
package sun.java2d;

import java.lang.ref.SoftReference;
import java.lang.ref.WeakReference;

/**
 *
 * @param <K>
 */
public abstract class ReentrantContextProvider<K extends ReentrantContext>
{
    // thread-local storage: inactive
    public static final byte USAGE_TL_INACTIVE = 0;
    // thread-local storage: in use
    public static final byte USAGE_TL_IN_USE = 1;
    // CLQ storage
    public static final byte USAGE_CLQ = 2;

    // hard reference
    public static final int REF_HARD = 0;
    // soft reference
    public static final int REF_SOFT = 1;
    // weak reference
    public static final int REF_WEAK = 2;

    /* members */
    // internal reference type
    protected final ReferenceWrapper<K> refWrapper;

    /**
     * Create a new ReentrantContext provider using the given reference type
     * among hard, soft or weak
     * @param refType reference type
     */
    protected ReentrantContextProvider(final int refType) {
        switch (refType) {
            case REF_HARD:
                this.refWrapper = new ReferenceWrapper.HardReferenceWrapper<K>();
                break;
            case REF_SOFT:
                this.refWrapper = new ReferenceWrapper.SoftReferenceWrapper<K>();
                break;
            default:
            case REF_WEAK:
                this.refWrapper = new ReferenceWrapper.WeakReferenceWrapper<K>();
                break;
        }
    }

    /**
     * Return a new ReentrantContext instance
     * @return new ReentrantContext instance
     */
    protected abstract K newContext();

    /**
     * Give a ReentrantContext instance for the current thread
     * @return ReentrantContext instance
     */
    public abstract K acquire();

    /**
     * Restore the given ReentrantContext instance for reuse
     * @param ctx ReentrantContext instance
     */
    public abstract void release(K ctx);


    static abstract class ReferenceWrapper<K extends ReentrantContext>
    {
        abstract K resolveReference(final Object ref);

        abstract Object getOrCreateReference(final K ctx);


        final static class HardReferenceWrapper<K extends ReentrantContext>
                extends ReferenceWrapper<K>
        {
            @Override
            @SuppressWarnings("unchecked")
            K resolveReference(final Object ref) {
                return (K)ref;
            }

            @Override
            Object getOrCreateReference(final K ctx) {
                return ctx;
            }
        }

        final static class SoftReferenceWrapper<K extends ReentrantContext>
                extends ReferenceWrapper<K>
        {
            @Override
            @SuppressWarnings("unchecked")
            K resolveReference(final Object ref) {
                return (ref != null) ? ((SoftReference<K>) ref).get() : null;
            }

            @Override
            Object getOrCreateReference(final K ctx) {
                if (ctx.reference == null) {
                    // Create the reference:
                    ctx.reference = new SoftReference<K>(ctx);
                }
                return ctx.reference;
            }
        }

        final static class WeakReferenceWrapper<K extends ReentrantContext>
                extends ReferenceWrapper<K>
        {
            @Override
            @SuppressWarnings("unchecked")
            K resolveReference(final Object ref) {
                return (ref != null) ? ((WeakReference<K>) ref).get() : null;
            }

            @Override
            Object getOrCreateReference(final K ctx) {
                if (ctx.reference == null) {
                    // Create the reference:
                    ctx.reference = new WeakReference<K>(ctx);
                }
                return ctx.reference;
            }
        }
    }
}