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package ucar.nc2.ft2.simpgeometry;

import java.io.IOException;
import ucar.ma2.Array;
import ucar.nc2.Variable;

/**
 * A Simple Geometry Index Finder can go find the beginning and end indicies of
 * a simple geometry X and Y within a variable. But first the Index Finder needs a few variables to find it in.
 * If the indexer is tasked to find a Simple Geometry close to one before, it will find it faster.
 * 
 * @author [email protected]
 *
 */
public class SimpleGeometryIndexFinder {

  private final int INVALID_INDEX = -10; // default invalid index before any lookups have been done
  private Array nodeCount;
  private int pastIndex;
  private int previousEnd;
  private int previousBegin;

  private int getNodeCount(int index) {
    return nodeCount.getInt(index);
  }

  /**
   * Gets the beginning index of a geometry's points given the index of the geometry within the array.
   * 
   * @return beginning of the range
   */
  public int getBeginning(int index) {

    // Test if the last end is the new beginning
    if (index == (pastIndex + 1)) {
      return previousEnd + 1;
    }

    // Otherwise, find it!
    int newBeginning = 0;
    for (int i = 0; i < index; i++) {
      newBeginning += getNodeCount(i);
    }

    pastIndex = index;
    previousBegin = newBeginning;
    return newBeginning;
  }

  /**
   * Gets the ending index of a geometry's points given the index of the geometry within the array.
   * 
   * @param index of the geometry within the array
   * @return end of the range
   */
  public int getEnd(int index) {

    // Test if the last beginning is the new end
    if (index == (pastIndex - 1)) {
      return previousBegin - 1;
    }

    // Otherwise find it!
    int new_end = 0;
    for (int i = 0; i < index + 1; i++) {
      new_end += getNodeCount(i);
    }

    pastIndex = index;
    previousEnd = new_end;
    return new_end - 1;
  }

  /**
   * Create a new indexer, the indexer must be given a variable to look through.
   * 
   * @param node_count Amount of nodes per geometry
   */
  public SimpleGeometryIndexFinder(Variable node_count) {

    try {
      this.nodeCount = node_count.read();
    } catch (IOException e) {

      this.nodeCount = null;
      e.printStackTrace();
    }

    pastIndex = INVALID_INDEX;
    previousEnd = INVALID_INDEX;
    previousBegin = INVALID_INDEX;
  }
}