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package atom.app.disruptor;

import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

/**
 * Callback container for activity thread processing.
 *
 * @author Alexander Voloshyn
 * @version 1.0 2/18/2013
 */
public final class Callback {
    /**
     * Sync lock for thread locking.
     */
    private final transient Lock sync = new ReentrantLock();
    /**
     * Special condition for key matching check.
     */
    private final transient Condition condition = sync.newCondition();
    /**
     * A key that used for lock this activity thread.
     */
    private transient int key;
    /**
     * Exception that could appear during activity thread processing.
     */
    private transient Throwable fault;

    /**
     * Sets an exception that could appear during activity thread processing.
     *
     * @param throwable an exception that could appear during activity thread
     *                  processing
     */
    public void setFault(final Throwable throwable) {
        fault = throwable;
    }

    /**
     * Provide ability to lock activity thread for return any value until it
     * will be unlocked by the same object or equals.
     *
     * @param lockKey lock object current thread
     */
    public void lock(final int lockKey) {
        key = lockKey;
    }

    /**
     * Provide ability to unlock activity thread by given key object.
     *
     * @param lockKey unlock object current thread
     */
    public void unlock(final int lockKey) {
        if (key == lockKey) {
            unlock();
        }
    }

    /**
     * Provide ability to unlock activity thread by given key object.
     */
    public void unlock() {
        sync.lock();
        key = 0;
        condition.signal();
        sync.unlock();
    }

    /**
     * Provide callback steps.
     */
    public void perform() {
        sync.lock();
        try {
            while (key != 0) {
                condition.await();
            }
        } catch (InterruptedException e) {
            fault = e;
        } finally {
            sync.unlock();
        }

        if (fault != null) {
            final Throwable throwable = fault;
            fault = null;
            if (throwable instanceof RuntimeException) {
                throw (RuntimeException) throwable;
            } else {
                throw new IllegalStateException(throwable);
            }
        }
    }
}