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/*
 * Copyright 2017 SPF4J.
 *
 * Licensed 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 org.spf4j.failsafe;

import javax.annotation.concurrent.ThreadSafe;

/**
 * @author Zoltan Farkas
 */
@ThreadSafe
public final class FibonacciRetryDelaySupplier implements RetryDelaySupplier {

  private int immediateLeft;

  private long p1;

  private long p2;

  private final long maxDelay;

  private final long startDelay;

  public FibonacciRetryDelaySupplier(final int immediateLeft, final long startDelay, final long maxDelay) {
    this.immediateLeft = immediateLeft;
    this.startDelay = startDelay;
    this.maxDelay = maxDelay;
    if (startDelay < 1) {
      this.p1 = 0;
      this.p2 = 1;
    } else {
      this.p1 = startDelay;
      this.p2 = startDelay + 1;
    }
  }

  @Override
  public synchronized long nextDelay() {
    if (immediateLeft > 0) {
      immediateLeft--;
      return p1;
    } else if (p2 > maxDelay) {
      return maxDelay;
    } else {
      long result = p2;
      p2 = p1 + p2;
      p1 = result;
      return result;
    }
  }

  @Override
  public synchronized String toString() {
    return "FibonacciBackoff{" + "immediateLeft=" + immediateLeft + ", p1=" + p1
            + ", p2=" + p2 + ", maxDelay=" + maxDelay + ", startDelay=" + startDelay + '}';
  }


}