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/*
 * Copyright 2016 dorkbox, llc
 *
 * Licensed 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 dorkbox.network.rmi;

import com.esotericsoftware.kryo.util.IdentityMap;

import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;

/**
 * Uses the "single writer principle" for fast access
 */
public
class OverriddenMethods {
    // not concurrent because they are setup during system initialization
    private volatile IdentityMap, Class> overriddenMethods = new IdentityMap, Class>();
    private volatile IdentityMap, Class> overriddenReverseMethods = new IdentityMap, Class>();

    private static final AtomicReferenceFieldUpdater overriddenMethodsREF =
                    AtomicReferenceFieldUpdater.newUpdater(OverriddenMethods.class,
                                                           IdentityMap.class,
                                                           "overriddenMethods");

    private static final AtomicReferenceFieldUpdater overriddenReverseMethodsREF =
                    AtomicReferenceFieldUpdater.newUpdater(OverriddenMethods.class,
                                                           IdentityMap.class,
                                                           "overriddenReverseMethods");

    private static final OverriddenMethods INSTANCE = new OverriddenMethods();
    public static synchronized OverriddenMethods INSTANCE() {
        return INSTANCE;
    }

    private
    OverriddenMethods() {
    }

    /**
     * access a snapshot of the subscriptions (single-writer-principle)
     */
    public
    Class get(final Class type) {
        //noinspection unchecked
        final IdentityMap, Class> identityMap = overriddenMethodsREF.get(this);
        return identityMap.get(type);
    }

    /**
     * access a snapshot of the subscriptions (single-writer-principle)
     */
    public
    Class getReverse(final Class type) {
        //noinspection unchecked
        final IdentityMap, Class> identityMap = overriddenReverseMethodsREF.get(this);
        return identityMap.get(type);
    }

    // synchronized to make sure only one writer at a time
    public synchronized
    void set(final Class ifaceClass, final Class implClass) {
        this.overriddenMethods.put(ifaceClass, implClass);
        this.overriddenReverseMethods.put(implClass, ifaceClass);
    }
}