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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 org.apache.kudu.client;

import java.util.concurrent.TimeUnit;

import com.google.common.base.Stopwatch;

/**
 * This is a wrapper class around {@link com.google.common.base.Stopwatch} used to track a timeout
 * in the future.
 * 
 * The watch starts as soon as this object is created with a timeout of 0, which means that
 * there's no timeout.
 * The timeout has been reached once the stopwatch's elapsed time is equal or greater than the
 * provided timeout.
 */
public class TimeoutTracker {
  private final Stopwatch stopwatch;
  /** timeout in milliseconds **/
  private long timeout = 0;

  /**
   * Creates a new tracker, which starts the stopwatch right now.
   */
  public TimeoutTracker() {
    this(Stopwatch.createUnstarted());
  }

  /**
   * Creates a new tracker, using the specified stopwatch, and starts it right now.
   * The stopwatch is reset if it was already running.
   * @param stopwatch Specific Stopwatch to use
   */
  public TimeoutTracker(Stopwatch stopwatch) {
    if (stopwatch.isRunning()) {
      stopwatch.reset();
    }
    this.stopwatch = stopwatch.start();
  }

  /**
   * Check if we're already past the timeout.
   * @return true if we're past the timeout, otherwise false. Also returns false if no timeout
   * was specified
   */
  public boolean timedOut() {
    if (!hasTimeout()) {
      return false;
    }
    return timeout - stopwatch.elapsed(TimeUnit.MILLISECONDS) <= 0;
  }

  /**
   * Get the number of milliseconds before the timeout is reached.
   * 

   * This method is used to pass down the remaining timeout to the RPCs, so has special semantics.
   * A timeout of 0 is used to indicate an infinite timeout, and negative timeouts are invalid.
   * Thus, if the timeout has passed (i.e. timeout - stopwatch.elapsedMillis() <= 0),
   * the returned value is floored at 1.
   * 
   * Callers who care about this behavior should first check {@link #timedOut()}.
   *
   * @return the remaining millis before the timeout is reached, or 1 if the remaining time is
   * lesser or equal to 0, or Long.MAX_VALUE if no timeout was specified (in which case it
   * should never be called).
   * @throws IllegalStateException if this method is called and no timeout was set
   */
  public long getMillisBeforeTimeout() {
    if (!hasTimeout()) {
      throw new IllegalStateException("This tracker doesn't have a timeout set so it cannot " +
          "answer getMillisBeforeTimeout()");
    }
    long millisBeforeTimeout = timeout - stopwatch.elapsed(TimeUnit.MILLISECONDS);
    millisBeforeTimeout = millisBeforeTimeout <= 0 ? 1 : millisBeforeTimeout;
    return millisBeforeTimeout;
  }

  public long getElapsedMillis() {
    return this.stopwatch.elapsed(TimeUnit.MILLISECONDS);
  }

  /**
   * Tells if a non-zero timeout was set.
   * @return true if the timeout is greater than 0, false otherwise.
   */
  public boolean hasTimeout() {
    return timeout != 0;
  }

  /**
   * Utility method to check if sleeping for a specified amount of time would put us past the
   * timeout.
   * @param plannedSleepTimeMillis number of milliseconds for a planned sleep
   * @return if the planned sleeps goes past the timeout.
   */
  public boolean wouldSleepingTimeoutMillis(long plannedSleepTimeMillis) {
    if (!hasTimeout()) {
      return false;
    }
    return getMillisBeforeTimeout() - plannedSleepTimeMillis <= 0;
  }

  /**
   * Sets the timeout to 0 (no timeout) and restarts the stopwatch from scratch.
   */
  public void reset() {
    timeout = 0;
    stopwatch.reset();
    stopwatch.start();
  }

  /**
   * Get the timeout (in milliseconds).
   * @return the current timeout
   */
  public long getTimeout() {
    return timeout;
  }

  /**
   * Set a new timeout for this tracker. It cannot be smaller than 0,
   * and if it is 0 then it means that there is no timeout (which is the default behavior).
   * This method won't call reset().
   * @param timeout a number of milliseconds greater or equal to 0
   * @throws IllegalArgumentException if the timeout is lesser than 0
   */
  public void setTimeout(long timeout) {
    if (timeout < 0) {
      throw new IllegalArgumentException("The timeout must be greater or equal to 0, " +
          "the passed value is " + timeout);
    }
    this.timeout = timeout;
  }

  @Override
  public String toString() {
    StringBuilder buf = new StringBuilder("TimeoutTracker(timeout=");
    buf.append(timeout);
    buf.append(", elapsed=").append(stopwatch.elapsed(TimeUnit.MILLISECONDS));
    buf.append(")");
    return buf.toString();
  }
}