
/*
 * 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.algorithm;

import org.locationtech.jts.geom.Coordinate;
import org.locationtech.jts.geom.Geometry;
import org.locationtech.jts.geom.GeometryCollection;
import org.locationtech.jts.geom.LineString;

/**
 * Computes a point in the interior of an linear geometry.
 * <h2>Algorithm</h2>
 * <ul>
 * <li>Find an interior vertex which is closest to
 * the centroid of the linestring.
 * <li>If there is no interior vertex, find the endpoint which is
 * closest to the centroid.
 * </ul>
 *
 * @version 1.7
 */
public class InteriorPointLine {
  
  /**
   * Computes an interior point for the
   * linear components of a Geometry.
   * 
   * @param geom the geometry to compute
   * @return the computed interior point,
   * or <code>null</code> if the geometry has no linear components
   */
  public static Coordinate getInteriorPoint(Geometry geom) {
    InteriorPointLine intPt = new InteriorPointLine(geom);
    return intPt.getInteriorPoint();
  }
  
  private Coordinate centroid;
  private double minDistance = Double.MAX_VALUE;

  private Coordinate interiorPoint = null;

  public InteriorPointLine(Geometry g)
  {
    centroid = g.getCentroid().getCoordinate();
    addInterior(g);
    if (interiorPoint == null)
      addEndpoints(g);
  }

  public Coordinate getInteriorPoint()
  {
    return interiorPoint;
  }

  /**
   * Tests the interior vertices (if any)
   * defined by a linear Geometry for the best inside point.
   * If a Geometry is not of dimension 1 it is not tested.
   * @param geom the geometry to add
   */
  private void addInterior(Geometry geom)
  {
    if (geom instanceof LineString) {
      addInterior(geom.getCoordinates());
    }
    else if (geom instanceof GeometryCollection) {
      GeometryCollection gc = (GeometryCollection) geom;
      for (int i = 0; i < gc.getNumGeometries(); i++) {
        addInterior(gc.getGeometryN(i));
      }
    }
  }
  private void addInterior(Coordinate[] pts)
  {
    for (int i = 1; i < pts.length - 1; i++) {
      add(pts[i]);
    }
  }
  /**
   * Tests the endpoint vertices
   * defined by a linear Geometry for the best inside point.
   * If a Geometry is not of dimension 1 it is not tested.
   * @param geom the geometry to add
   */
  private void addEndpoints(Geometry geom)
  {
    if (geom instanceof LineString) {
      addEndpoints(geom.getCoordinates());
    }
    else if (geom instanceof GeometryCollection) {
      GeometryCollection gc = (GeometryCollection) geom;
      for (int i = 0; i < gc.getNumGeometries(); i++) {
        addEndpoints(gc.getGeometryN(i));
      }
    }
  }
  private void addEndpoints(Coordinate[] pts)
  {
    add(pts[0]);
    add(pts[pts.length - 1]);
  }

  private void add(Coordinate point)
  {
    double dist = point.distance(centroid);
    if (dist < minDistance) {
      interiorPoint = new Coordinate(point);
      minDistance = dist;
    }
  }

}
