NodeBase.java

/*
 * 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 v1.0
 * and Eclipse Distribution License v. 1.0 which accompanies this distribution.
 * The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v10.html
 * and the Eclipse Distribution License is available at
 *
 * http://www.eclipse.org/org/documents/edl-v10.php.
 */
package org.locationtech.jts.index.quadtree;

import java.io.Serializable;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

import org.locationtech.jts.geom.Envelope;
import org.locationtech.jts.index.ItemVisitor;


/**
 * The base class for nodes in a {@link Quadtree}.
 *
 * @version 1.7
 */
public abstract class NodeBase implements Serializable {

//DEBUG private static int itemCount = 0;  // debugging
  
  /**
   * Gets the index of the subquad that wholly contains the given envelope.
   * If none does, returns -1.
   * 
   * @return the index of the subquad that wholly contains the given envelope
   * or -1 if no subquad wholly contains the envelope
   */
  public static int getSubnodeIndex(Envelope env, double centrex, double centrey)
  {
    int subnodeIndex = -1;
    if (env.getMinX() >= centrex) {
      if (env.getMinY() >= centrey) subnodeIndex = 3;
      if (env.getMaxY() <= centrey) subnodeIndex = 1;
    }
    if (env.getMaxX() <= centrex) {
      if (env.getMinY() >= centrey) subnodeIndex = 2;
      if (env.getMaxY() <= centrey) subnodeIndex = 0;
    }
    return subnodeIndex;
  }

  protected List items = new ArrayList();

  /**
   * subquads are numbered as follows:
   * <pre>
   *  2 | 3
   *  --+--
   *  0 | 1
   * </pre>
   */
  protected Node[] subnode = new Node[4];

  public NodeBase() {
  }

  public List getItems() { return items; }

  public boolean hasItems() { return ! items.isEmpty(); }

  public void add(Object item)
  {
    items.add(item);
//DEBUG itemCount++;
//DEBUG System.out.print(itemCount);
  }

  /**
   * Removes a single item from this subtree.
   *
   * @param itemEnv the envelope containing the item
   * @param item the item to remove
   * @return <code>true</code> if the item was found and removed
   */
  public boolean remove(Envelope itemEnv, Object item)
  {
    // use envelope to restrict nodes scanned
    if (! isSearchMatch(itemEnv))
      return false;

    boolean found = false;
    for (int i = 0; i < 4; i++) {
      if (subnode[i] != null) {
        found = subnode[i].remove(itemEnv, item);
        if (found) {
          // trim subtree if empty
          if (subnode[i].isPrunable())
            subnode[i] = null;
          break;
        }
      }
    }
    // if item was found lower down, don't need to search for it here
    if (found) return found;
    // otherwise, try and remove the item from the list of items in this node
    found = items.remove(item);
    return found;
  }

  public boolean isPrunable()
  {
    return ! (hasChildren() || hasItems());
  }

  public boolean hasChildren()
  {
    for (int i = 0; i < 4; i++) {
      if (subnode[i] != null)
        return true;
    }
    return false;
  }

  public boolean isEmpty()
  {
    boolean isEmpty = true;
    if (! items.isEmpty()) isEmpty = false;
    for (int i = 0; i < 4; i++) {
      if (subnode[i] != null) {
        if (! subnode[i].isEmpty() )
          isEmpty = false;
      }
    }
    return isEmpty;
  }

  //<<TODO:RENAME?>> Sounds like this method adds resultItems to items
  //(like List#addAll). Perhaps it should be renamed to "addAllItemsTo" [Jon Aquino]
  public List addAllItems(List resultItems)
  {
    // this node may have items as well as subnodes (since items may not
    // be wholely contained in any single subnode
    resultItems.addAll(this.items);
    for (int i = 0; i < 4; i++) {
      if (subnode[i] != null) {
        subnode[i].addAllItems(resultItems);
      }
    }
    return resultItems;
  }
  protected abstract boolean isSearchMatch(Envelope searchEnv);

  public void addAllItemsFromOverlapping(Envelope searchEnv, List resultItems)
  {
    if (! isSearchMatch(searchEnv))
      return;

    // this node may have items as well as subnodes (since items may not
    // be wholely contained in any single subnode
    resultItems.addAll(items);

    for (int i = 0; i < 4; i++) {
      if (subnode[i] != null) {
        subnode[i].addAllItemsFromOverlapping(searchEnv, resultItems);
      }
    }
  }

  public void visit(Envelope searchEnv, ItemVisitor visitor)
  {
    if (! isSearchMatch(searchEnv))
      return;

    // this node may have items as well as subnodes (since items may not
    // be wholely contained in any single subnode
    visitItems(searchEnv, visitor);

    for (int i = 0; i < 4; i++) {
      if (subnode[i] != null) {
        subnode[i].visit(searchEnv, visitor);
      }
    }
  }

  private void visitItems(Envelope searchEnv, ItemVisitor visitor)
  {
    // would be nice to filter items based on search envelope, but can't until they contain an envelope
    for (Iterator i = items.iterator(); i.hasNext(); ) {
      visitor.visitItem(i.next());
    }
  }

//<<TODO:RENAME?>> In Samet's terminology, I think what we're returning here is
//actually level+1 rather than depth. (See p. 4 of his book) [Jon Aquino]
  int depth()
  {
    int maxSubDepth = 0;
    for (int i = 0; i < 4; i++) {
      if (subnode[i] != null) {
        int sqd = subnode[i].depth();
        if (sqd > maxSubDepth)
          maxSubDepth = sqd;
      }
    }
    return maxSubDepth + 1;
  }

  int size()
  {
    int subSize = 0;
    for (int i = 0; i < 4; i++) {
      if (subnode[i] != null) {
        subSize += subnode[i].size();
      }
    }
    return subSize + items.size();
  }

  int getNodeCount()
  {
    int subSize = 0;
    for (int i = 0; i < 4; i++) {
      if (subnode[i] != null) {
        subSize += subnode[i].size();
      }
    }
    return subSize + 1;
  }

}