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Client for SwiftMQ Messaging System with JMS, AMQP 1.0 and file transfer over JMS.

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/*
 * Copyright 2019 IIT Software GmbH
 *
 * IIT Software GmbH 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 com.swiftmq.tools.concurrent;

import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.atomic.AtomicReference;

public abstract class CallbackJoin {
    protected volatile boolean finalSuccess = true;
    protected volatile Object finalResult = null;
    protected volatile Exception finalException = null;
    AtomicInteger numberCallbacks = new AtomicInteger();
    volatile boolean blocked = true;
    private final AtomicReference nextRef = new AtomicReference<>();

    protected CallbackJoin(AsyncCompletionCallback next) {
        this.nextRef.set(next);
    }

    protected CallbackJoin() {
    }

    private AsyncCompletionCallback getNext() {
        if (blocked || nextRef.get() == null)
            return null;
        return nextRef.getAndSet(null);  // Atomic get and set to null
    }

    private void checkNext() {
        AsyncCompletionCallback theNext = getNext();
        if (theNext != null) {
            theNext.setException(finalException);
            theNext.setResult(finalResult);
            theNext.notifyCallbackStack(finalSuccess);
        }
    }

    public void incNumberCallbacks() {
        numberCallbacks.incrementAndGet();
    }

    public void setNumberCallbacks(int numberCallbacks) {
        this.numberCallbacks.set(numberCallbacks);
    }

    public void setBlocked(boolean blocked) {
        this.blocked = blocked;
        if (numberCallbacks.get() == 0)
            checkNext();
    }

    public void done(AsyncCompletionCallback callback, boolean success) {
        int n = numberCallbacks.decrementAndGet();
        callbackDone(callback, success, n == 0);
        if (n == 0)
            checkNext();
    }

    protected abstract void callbackDone(AsyncCompletionCallback callback, boolean success, boolean last);
}