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package org.dcache.util.backoff;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.concurrent.Callable;

import static org.dcache.util.backoff.IBackoffAlgorithm.Status.FAILURE;
import static org.dcache.util.backoff.IBackoffAlgorithm.Status.SUCCESS;

/**
 * Executes a {@link Callable} object in a loop controlled by an
 * {@link IBackoffAlgorithm} implementation which provides the logic for
 * determining how long of a wait should be executed between passes, or
 * whether the thread should quit, when the call status is FAILURE.
 */
public class BackoffController
{
    private static final Logger logger =
            LoggerFactory.getLogger(BackoffController.class);

    private final IBackoffAlgorithmFactory factory;

    public BackoffController(IBackoffAlgorithmFactory factory)
    {
        this.factory = factory;
    }

    public IBackoffAlgorithm.Status call(Callable<IBackoffAlgorithm.Status> callable)
                    throws Exception
    {
        IBackoffAlgorithm algorithm = factory.getAlgorithm();

        while (true) {
            switch (callable.call()) {
            case SUCCESS:
                 return SUCCESS;

            case FAILURE:
                long wait = algorithm.getWaitDuration();

                if (wait == IBackoffAlgorithm.NO_WAIT) {
                    logger.trace("algorithm returned NO_WAIT");
                    return FAILURE;
                }

                handleWait(wait);
            }
        }
    }

    protected void handleWait(long wait) throws InterruptedException
    {
        Thread.sleep(wait);
    }
}