// Copyright 2010 Google Inc. All Rights Reserved.

package org.waveprotocol.wave.model.util;

import java.util.Map;

/**
 * Observable collection of items.
 *
*
 */
public final class ObservableMapImpl<K, V> implements SimpleMap<K, V>, ObservableMap<K, V> {
  /** Listeners to notify of collection changes. */
  private final CopyOnWriteSet<Listener<? super K, ? super V>> listeners = CopyOnWriteSet.create();

  /** Items. */
  private final Map<K, V> items = CollectionUtils.newHashMap();

  /**
   * Creates an observable map.
   */
  private ObservableMapImpl() {
    // nothing to do
  }

  /**
   * Creates an observable map.
   */
  public static <K, V> ObservableMapImpl<K, V> create() {
    ObservableMapImpl<K, V> map = new ObservableMapImpl<K, V>();
    return map;
  }

  @Override
  public V put(K id, V item) {
    V old = items.get(id);
    if (old == item) {
      // Already there.
      return old;
    }
    items.put(id, item);
    if (old != null) {
      triggerOnItemRemoved(id, old);
    }
    triggerOnItemAdded(id, item);
    return old;
  }

  @Override
  public V remove(K id) {
    V old = items.remove(id);
    if (old != null) {
      triggerOnItemRemoved(id, old);
    }
    return old;
  }

  @Override
  public void clear() {
    items.clear();
  }

  @Override
  public V get(K key) {
    return items.get(key);
  }

  @Override
  public int size() {
    return items.size();
  }

  @Override
  public boolean isEmpty() {
    return items.isEmpty();
  }

  @Override
  public Iterable<K> copyKeys() {
    return CollectionUtils.newArrayList(items.keySet());
  }

  //
  // Extra methods that are useful, but not exposed by the map interfaces.
  //

  @Override
  public final boolean equals(Object o) {
    return (this == o)
        || (o instanceof ObservableMapImpl && items.equals(((ObservableMapImpl<?, ?>) o).items));
  }

  @Override
  public final int hashCode() {
    return items.hashCode();
  }

  //
  // Listeners.
  //

  @Override
  public void addListener(Listener<? super K, ? super V> l) {
    listeners.add(l);
  }

  @Override
  public void removeListener(Listener<? super K, ? super V> l) {
    listeners.remove(l);
  }

  private void triggerOnItemAdded(K key, V blip) {
    for (Listener<? super K, ? super V> l : listeners) {
      l.onEntryAdded(key, blip);
    }
  }

  private void triggerOnItemRemoved(K key, V blip) {
    for (Listener<? super K, ? super V> l : listeners) {
      l.onEntryRemoved(key, blip);
    }
  }
}