/* 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.clustering;

import org.apache.mahout.math.Vector;
import org.apache.mahout.math.VectorWritable;

/**
 * Implementations of this interface have a printable representation and certain
 * attributes that are common across all clustering implementations
 * 
 */
public interface Cluster extends Model<VectorWritable> {
  
  // default directory for all clustered points
  String CLUSTERED_POINTS_DIR = "clusteredPoints";

  // default directory for initial clusters to prime iterative clustering algorithms
  String INITIAL_CLUSTERS_DIR = "clusters-0";

  // default directory for output of clusters per iteration
  String CLUSTERS_DIR = "clusters-";

  /**
   * Get the id of the Cluster
   * 
   * @return a unique integer
   */
  int getId();

  /**
   * Get the "center" of the Cluster as a Vector
   * 
   * @return a Vector
   */
  Vector getCenter();
  
  /**
   * Get the "radius" of the Cluster as a Vector. Usually the radius is the standard deviation expressed
   * as a Vector of size equal to the center. Some clusters may return zero values if not appropriate.
   * 
   * @return aVector
   */
  Vector getRadius();

  /**
   * Get an integer denoting the number of points observed by this cluster
   * @return an integer 
   */
  int getNumPoints();

  /**
   * Produce a custom, human-friendly, printable representation of the Cluster.
   * 
   * @param bindings
   *          an optional String[] containing labels used to format the primary Vector/s of this
   *          implementation.
   * @return a String
   */
  String asFormatString(String[] bindings);
  
  /**
   * Produce a textual representation of the Cluster using Json format. (Label bindings are transient and not part
   * of the Json representation)
   * 
   * @return a Json String
   */
  String asJsonString();
  
}
