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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF 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 studio.raptor.ddal.common.retry;

import java.util.concurrent.TimeUnit;


/**
 *  Mechanism to perform an operation on Zookeeper that is safe against disconnections and
 * "recoverable" errors. 
  
 If an exception occurs during the operation, the RetryLoop
 * will process it, check with the current retry policy and either attempt to reconnect or re-throw
 * the exception 
  Canonical usage:
 

 * 
 * RetryLoop retryLoop = client.newRetryLoop();
 * while (retryLoop.shouldContinue()) {
 *     try {
 *         // do your work
 *         ZooKeeper zk = client.getZooKeeper(); // it's important to re-get the ZK instance in case
 * there was an error
 *                                               // and the instance was re-created
 *
 *         retryLoop.markComplete();
 *     }
 *     catch (Exception e) {
 *         retryLoop.takeException(e);
 *     }
 * }
 * 
 */
public class RetryLoop {

    private static final RetrySleeper sleeper = new RetrySleeper() {
        @Override
        public void sleepFor(long time, TimeUnit unit) throws InterruptedException {
            unit.sleep(time);
        }
    };
    private final long startTimeMs = System.currentTimeMillis();
    private final RetryPolicy retryPolicy;
    private int retryCount = 0;
    private boolean isDone = false;


    public RetryLoop(RetryPolicy retryPolicy) {
        this.retryPolicy = retryPolicy;
    }

    /**
     * Returns the default retry sleeper
     *
     * @return sleeper
     */
    public static RetrySleeper getDefaultRetrySleeper() {
        return sleeper;
    }

    /**
     * If true is returned, make an attempt at the operation
     *
     * @return true/false
     */
    public boolean shouldContinue() {
        return !isDone;
    }


    /**
     * Call this when your operation has successfully completed
     */
    public void markComplete() {
        isDone = true;
    }


    /**
     * Pass any caught exceptions here
     *
     * @param exception the exception
     * @throws Exception if not retry-able or the retry policy returned negative
     */
    public void takeException(Exception exception) throws Exception {
        boolean rethrow = true;

        if (retryPolicy.allowRetry(retryCount++, System.currentTimeMillis() - startTimeMs, sleeper)) {
            rethrow = false;
        }

        if (rethrow) {
            throw exception;
        }
    }

}