// Copyright (C) 2015 The Android Open Source Project
//
// 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 com.google.gerrit.metrics;

/**
 * Metric whose value is supplied when the trigger is invoked.
 *
 * <pre>
 *   CallbackMetric0&lt;Long&gt; hits = metricMaker.newCallbackMetric("hits", ...);
 *   CallbackMetric0&lt;Long&gt; total = metricMaker.newCallbackMetric("total", ...);
 *   metricMaker.newTrigger(hits, total, new Runnable() {
 *     public void run() {
 *       hits.set(1);
 *       total.set(5);
 *     }
 *   });
 * </pre>
 *
 * @param <V> type of the metric value, typically Integer or Long.
 */
public abstract class CallbackMetric0<V> implements CallbackMetric<V> {
  /**
   * Supply the current value of the metric.
   *
   * @param value current value.
   */
  public abstract void set(V value);

  @Override
  public void prune() {}
}