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HttpClient-based client for Riak
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/*
 * This file is provided 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.basho.riak.client.cap;

import java.util.concurrent.Callable;

import com.basho.riak.client.RiakRetryFailedException;
import com.basho.riak.client.convert.ConversionException;
import com.basho.riak.client.raw.MatchFoundException;

/**
 * A basic retrier implementation that attempts *n* times before throwing a
 * {@link UnresolvedConflictException}.
 * 
 * 
 * Construct it with the number of times a {@link Callable} should be attempted.
 * When attempt is called with a {@link Callable} then
 * {@link Callable#call()} is run attempts times before throwing a
 * {@link RiakRetryFailedException}. It is important to note that there is no
 * backoff between attempts.
 * 
 * 
 * @author russell
 */
public class DefaultRetrier implements Retrier {

    private final int attempts;

    /**
     * @param attempts
     *            how many times the retrier should attempt the call before
     *            throwing a {@link RiakRetryFailedException}
     */
    public DefaultRetrier(int attempts) {
        this.attempts = attempts;
    }

    /* (non-Javadoc)
     * @see com.basho.riak.client.cap.Retrier#attempt(java.util.concurrent.Callable)
     */
    public  T attempt(Callable command) throws RiakRetryFailedException {
        return attempt(command, attempts);
    }

    /**
     * Calls {@link Callable#call()} times before giving up and
     * throwing a {@link RiakRetryFailedException} There is no back off.
     *
     * @param 
     *            the {@link Callable}'s return type.
     * @param command
     *            the {@link Callable} to attempt
     * @param times
     *            how many times to try before we throw
     * @return the result of command
     * @throws RiakRetryFailedException
     *             if the Callable throws an exception times times
     */
    public static  T attempt(final Callable command, final int times) throws RiakRetryFailedException {
        try {
            return command.call();
        } catch (MatchFoundException e) {
            throw e;
        } catch (ConversionException e) {
            throw e;
        } catch (Exception e) {
            if (times == 0) {
                throw new RiakRetryFailedException(e);
            } else {
                return attempt(command, times - 1);
            }
        }
    }

    /**
     * Static factory method to create a default retrier
     *
     * @param attempts
     *            how many times the {@link DefaultRetrier} will attempt to call
     *            a {@link Callable} supplied to
     *            {@link Retrier#attempt(Callable)}
     * @return a {@link DefaultRetrier} configured for attempts
     *         retries
     */
    public static Retrier attempts(int attempts) {
        return new DefaultRetrier(attempts);
    }
}