/*
    * Copyright 2005 the original author or authors.
    * 
    * 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 net.sf.sensor.meter;
  
  import java.util.Collection;
  import java.util.HashMap;
  import java.util.Iterator;
  import java.util.Map;
  
  /***
   * Main entry point for working with Meters.
   * 
   * 
   * @author Age Mooy
   */
  public class MeterRuntime {
  
    // ==========================================================================
    // Fields
    // ==========================================================================
    
    /***
     * The map holding all active meters. 
     */
    private Map meterDatas = new HashMap();
    
    
    // ==========================================================================
    // Meter API
    // ==========================================================================
    
    /***
     * Returns a new {@link Meter} for the specified label.
     * @param label the label for the {@link Meter}.
     * @return the {@link Meter} that matches the specified label.
     */
    public Meter getMeter(String label) {
      return getOrCreateMeterData(label).createMeter();
    }
    
    /***
     * Returns an unmodifiable Collection<MeterStatistics> of all registered meters.
     * @return an unmodifiable Collection<MeterStatistics> of all registered meters.
     */
    public Collection getMeterStatistics() {
      return new UnmodifiableMeterStatisticsCollectionView(meterDatas.values());
    }
    
    /***
     * Resets all active counters to zero.
     * This method <b>does not delete</b> any counters.
     */
    public synchronized void reset() {
      for (Iterator i = meterDatas.values().iterator(); i.hasNext();) {
        ((MeterData) i.next()).reset();
      }
    }
    
    
    // ==========================================================================
    // Implementation details
    // ==========================================================================
    
    /***
     * Retrieves the instance of MeterData matching the specified label from the
     * counters Map and creates/add it if it doesn't exist yet.
     * @param label the label that should match an instance of MeterData.
     * @return the counter matching the specified label.
     */
    synchronized MeterData getOrCreateMeterData(String label) {
      MeterData meterData = (MeterData) meterDatas.get(label);
      
      if (meterData == null) {
        meterData = new MeterData(label);
        
        meterDatas.put(label, meterData);
      }
      
      return meterData;
    }
    
    /***
     * Simple wrapper class that transforms a Collection&lt;MeterData&gt;
     * into an unmodifiable Collection&lt;{@link MeterStatistics}&gt; without
     * copying the orignal data or creating new objects/references.
    * The {@link Iterator} returned by {@link #iterator()} will perform
    * the translation from MeterData to {@link MeterStatistics} by calling
    * the MeterData.getStatistics() method when {@link Iterator#next()} is
    * called. All operations that can change data in the underlying collection
    * will throw an {@link UnsupportedOperationException}. All other methods
    * will be passed through to the delegate. 
    * 
    * @author Age Mooy
    */
   static class UnmodifiableMeterStatisticsCollectionView implements Collection {
 
     /*** The Collection&lt;MeterData&gt; to delegate to. */
     Collection dataCollection;
 
     /***
      * Constructor that wraps the specified Collection&lt;MeterData&gt;.
      * @param dataCollection a Collection&lt;MeterData&gt;.
      */
     UnmodifiableMeterStatisticsCollectionView(Collection dataCollection) {
       this.dataCollection = dataCollection;
     }
 
     /***
      * The returned {@link Iterator} will transform the MessageData instances
      * contained in the delegate Collection&lt;MeterData&gt; into instances of 
      * {@link MeterStatistics} by calling the MeterData.getStatistics() method
      * on them.
      * @see java.util.Collection#iterator()
      */
     public Iterator iterator() {
       return new Iterator() {
         Iterator i = dataCollection.iterator();
 
         public boolean hasNext() {
           return i.hasNext();
         }
 
         public Object next() {
           return ((MeterData) i.next()).getStatistics();
         }
 
         public void remove() {
           throw new UnsupportedOperationException();
         }
       };
     }
     
     /***
      * @see java.util.Collection#size()
      */
     public int size() {
       return dataCollection.size();
     }
 
     /***
      * @see java.util.Collection#isEmpty()
      */
     public boolean isEmpty() {
       return dataCollection.isEmpty();
     }
 
     /***
      * @see java.util.Collection#contains(java.lang.Object)
      */
     public boolean contains(Object o) {
       return dataCollection.contains(o);
     }
 
     /***
      * @see java.util.Collection#containsAll(java.util.Collection)
      */
     public boolean containsAll(Collection coll) {
       return dataCollection.containsAll(coll);
     }
     
     /***
      * @see java.util.Collection#toArray()
      */
     public Object[] toArray() {
       return dataCollection.toArray();
     }
 
     /***
      * @see java.util.Collection#toArray(java.lang.Object[])
      */
     public Object[] toArray(Object[] a) {
       return dataCollection.toArray(a);
     }
 
     /***
      * @see java.lang.Object#toString()
      */
     public String toString() {
       return dataCollection.toString();
     }
 
     /***
      * @see java.util.Collection#add(java.lang.Object)
      */
     public boolean add(Object o) {
       throw new UnsupportedOperationException();
     }
 
     /***
      * @see java.util.Collection#addAll(java.util.Collection)
      */
     public boolean addAll(Collection coll) {
       throw new UnsupportedOperationException();
     }
 
     /***
      * @see java.util.Collection#remove(java.lang.Object)
      */
     public boolean remove(Object o) {
       throw new UnsupportedOperationException();
     }
     
     /***
      * @see java.util.Collection#removeAll(java.util.Collection)
      */
     public boolean removeAll(Collection coll) {
       throw new UnsupportedOperationException();
     }
 
     /***
      * @see java.util.Collection#retainAll(java.util.Collection)
      */
     public boolean retainAll(Collection coll) {
       throw new UnsupportedOperationException();
     }
 
     /***
      * @see java.util.Collection#clear()
      */
     public void clear() {
       throw new UnsupportedOperationException();
     }
   }
   
   
 }