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/*
 * All content copyright Terracotta, Inc., unless otherwise indicated.
 *
 * 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.terracotta.statistics;

import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.Callable;
import java.util.concurrent.CopyOnWriteArrayList;

import org.terracotta.context.WeakIdentityHashMap;
import org.terracotta.context.annotations.ContextAttribute;

@ContextAttribute(value="this")
class PassThroughStatistic implements ValueStatistic {

  private static final WeakIdentityHashMap>> BINDING = new WeakIdentityHashMap>>();
  
  private static void bindStatistic(PassThroughStatistic stat, Object to) {
    Collection> collection = BINDING.get(to);
    if (collection == null) {
      collection = new CopyOnWriteArrayList>();
      Collection> racer = BINDING.putIfAbsent(to, collection);
      if (racer != null) {
        collection = racer;
      }
    }
    collection.add(stat);
  }
  
  @ContextAttribute("name") public final String name;
  @ContextAttribute("tags") public final Set tags;
  @ContextAttribute("properties") public final Map properties;
  private final Callable source;
  
  public PassThroughStatistic(Object context, String name, Set tags, Map properties, Callable source) {
    this.name = name;
    this.tags = Collections.unmodifiableSet(new HashSet(tags));
    this.properties = Collections.unmodifiableMap(new HashMap(properties));
    this.source = source;
    bindStatistic(this, context);
  }

  @Override
  public T value() {
    try {
      return source.call();
    } catch (Exception ex) {
      throw new RuntimeException(ex);
    }
  }
}