

/*
 * Copyright (c) 2016 Vivid Solutions.
 *
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * and Eclipse Distribution License v. 1.0 which accompanies this distribution.
 * The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v20.html
 * and the Eclipse Distribution License is available at
 *
 * http://www.eclipse.org/org/documents/edl-v10.php.
 */
package org.locationtech.jts.geom;

import org.locationtech.jts.geom.util.GeometryEditor;
import org.locationtech.jts.geom.util.GeometryTransformer;

/**
 *  An interface for classes which process the coordinates in a {@link CoordinateSequence}. 
 *  A filter can either record information about each coordinate,
 *  or change the value of the coordinate. 
 *  Filters can be
 *  used to implement operations such as coordinate transformations, centroid and
 *  envelope computation, and many other functions.
 *  {@link Geometry} classes support the concept of applying a
 *  <code>CoordinateSequenceFilter</code> to each 
 *  {@link CoordinateSequence}s they contain. 
 *  <p>
 *  For maximum efficiency, the execution of filters can be short-circuited by using the {@link #isDone} method.
 *  <p>
 *  <code>CoordinateSequenceFilter</code> is
 *  an example of the Gang-of-Four Visitor pattern.
 *  <p> 
 * <b>Note</b>: In general, it is preferable to treat Geometrys as immutable. 
 * Mutation should be performed by creating a new Geometry object (see {@link GeometryEditor} 
 * and {@link GeometryTransformer} for convenient ways to do this).
 * An exception to this rule is when a new Geometry has been created via {@link Geometry#copy()}.
 * In this case mutating the Geometry will not cause aliasing issues, 
 * and a filter is a convenient way to implement coordinate transformation.
 *  
 * @see Geometry#apply(CoordinateFilter)
 * @see GeometryTransformer
 * @see GeometryEditor
 *
 *@see Geometry#apply(CoordinateSequenceFilter)
 *@author Martin Davis
 *@version 1.7
 */
public interface CoordinateSequenceFilter 
{
  /**
   * Performs an operation on a coordinate in a {@link CoordinateSequence}.
   *
   *@param seq  the <code>CoordinateSequence</code> to which the filter is applied
   *@param i the index of the coordinate to apply the filter to
   */
  void filter(CoordinateSequence seq, int i);
  
  /**
   * Reports whether the application of this filter can be terminated.
   * Once this method returns <tt>true</tt>, it must 
   * continue to return <tt>true</tt> on every subsequent call.
   * 
   * @return true if the application of this filter can be terminated.
   */
  boolean isDone();
  
  /**
   * Reports whether the execution of this filter
   * has modified the coordinates of the geometry.
   * If so, {@link Geometry#geometryChanged} will be executed
   * after this filter has finished being executed.
   * <p>
   * Most filters can simply return a constant value reflecting
   * whether they are able to change the coordinates.
   * 
   * @return true if this filter has changed the coordinates of the geometry
   */
  boolean isGeometryChanged();
}

