/**
 * 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.mahout.cf.taste.impl.recommender;

import java.io.Serializable;

import org.apache.mahout.cf.taste.recommender.RecommendedItem;
import org.apache.mahout.common.RandomUtils;

import com.google.common.base.Preconditions;

/**
 * <p>
 * A simple implementation of {@link RecommendedItem}.
 * </p>
 */
public final class GenericRecommendedItem implements RecommendedItem, Serializable {
  
  private final long itemID;
  private final float value;
  
  /**
   * @throws IllegalArgumentException
   *           if item is null or value is NaN
   */
  public GenericRecommendedItem(long itemID, float value) {
    Preconditions.checkArgument(!Float.isNaN(value), "value is NaN");
    this.itemID = itemID;
    this.value = value;
  }
  
  @Override
  public long getItemID() {
    return itemID;
  }
  
  @Override
  public float getValue() {
    return value;
  }
  
  @Override
  public String toString() {
    return "RecommendedItem[item:" + itemID + ", value:" + value + ']';
  }
  
  @Override
  public int hashCode() {
    return (int) itemID ^ RandomUtils.hashFloat(value);
  }
  
  @Override
  public boolean equals(Object o) {
    if (!(o instanceof GenericRecommendedItem)) {
      return false;
    }
    GenericRecommendedItem other = (GenericRecommendedItem) o;
    return (itemID == other.getItemID()) && (value == other.getValue());
  }
  
}
