/**
 * Licensed to Cloudera, Inc. under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  Cloudera, Inc. 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.cloudera.util;

/**
 * Wraps the retry logic associated with a BackoffPolicy to 
 * save having to write driver code.
 */
public class RetryHarness {
  Retryable retry;
  BackoffPolicy policy;
  Exception lastException = null;
  boolean throwOnFailure = false;
  volatile boolean abort = false;
  
  public RetryHarness(Retryable retry, BackoffPolicy policy) {
    this.retry = retry;
    this.policy = policy;
    retry.setHarness(this);
  }

  public RetryHarness(Retryable retry, BackoffPolicy policy, boolean throwOnFailure) {
    this.retry = retry;
    this.policy = policy;
    this.throwOnFailure = throwOnFailure;
    retry.setHarness(this);
  }
  
  /**
   * Returns the last exception thrown by the Retryable (or null if there was
   * none)
   */
  public Exception getLastException() {
    return lastException;  
  }
      
  /**
   * Calls doTry on a Retryable until either it succeeds or the backoff policy
   * fails. 
   */
  public boolean attempt() throws Exception {
    boolean success = false;
    abort = false;
    policy.reset();
    while (!abort && !policy.isFailed()) {
      policy.waitUntilRetryOk();
      try {
        if (policy.isRetryOk()) {
          success = retry.doTry();
          if (success) {
            return true;
          }             
        }
      } catch (Exception e) {
        lastException = e;        
      }
      policy.backoff();
    }
    if (throwOnFailure && lastException != null) {
      throw lastException;
    }
    return false;
  }
  
  public void doAbort() {    
    abort = true;
  }
}