/*
 * @(#)Sampler.java             0.0.0 99/07/05
 *
 * Copyright (c) 1999 by Willie Wheeler.  All rights reserved.
 */
package stats;

import java.util.*;
import javax.swing.*;
import javax.swing.event.*;

/**
 * Draws ordered random samples from a given population.  Samples can be
 * drawn with or without replacement.  Sample elements having the same
 * variable values are indistinguishable.
 *
 * @version     0.0.0 07/05/99
 * @author      Willie Wheeler
 */
public class Sampler extends JComponent implements TableModelListener {
  static boolean                debug = false;

  protected DataTableModel      pop, sample;
  protected int                 sampleSize;
  protected boolean             replace;

  /**
   * Permutation of population indices used to optimize sampling without
   * replacement.  A sample is obtained by shuffling the permutation and
   * keeping an initial segment.
   */
  protected List                popPerm;

  /**
   * Bag (i.e., unordered, multiplicity > 1 OK) sample representation.  This
   * can be useful for rendering samples.
   */
  protected Map                 sampleBag;

  public Sampler() {
    debug("<init>", "Entered.");
    this.pop = null;
    this.sampleSize = 0;
    this.replace = false;
  }

  public Sampler(DataTableModel pop, int sampleSize, boolean replace) {
    debug("<init>", "Entered.");
    setPopulation(pop);
    this.sampleSize = sampleSize;
    this.replace = replace;
  }

  public void setPopulation(DataTableModel pop) {
    debug("setPopulation()", "Entered.");
    this.pop = pop;

    // Build population index permutation.
    int popSize = pop.getRowCount();
    popPerm = new Vector(popSize);
    for (int i = 0; i < popSize; i++) { popPerm.add(new Integer(i)); }

    // Build table representation of the sample, and add this sampler
    // as a listener.
    sample = new DataTableModel(pop.getVariables(), 0);
    sample.addTableModelListener(this);

    // Build a bag representation of the sample.
    sampleBag = new HashMap();
  }

  public DataTableModel getPopulation() {
    debug("getPopulation()", "Entered.");
    return pop;
  }

  public int getPopulationSize() {
    debug("getPopulationSize()", "Entered.");
    return pop.getRowCount();
  }

  public void setSampleSize(int sampleSize) {
    debug("setSampleSize()", "Entered.");
    this.sampleSize = sampleSize;
  }

  public int getSampleSize() {
    debug("getSampleSize()", "Entered.");
    return sampleSize;
  }

  public void setReplace(boolean replace) {
    debug("setReplace()", "Entered, replace=" + replace + ".");
    this.replace = replace;
  }

  public boolean getReplace() {
    debug("getReplace()", "Entered.");
    return replace;
  }

  public DataTableModel getDataOut() {
    debug("getDataOut()", "Entered.");
    return sample;
  }

  /**
   * Returns the sample multiplicity of the given population element.
   *
   * @param     popID           population element ID
   * @return                    multiplicity of the given population element
   */
  public int getMultiplicity(int popID) {
    Integer mult = (Integer)sampleBag.get(new Integer(popID));
    return (mult == null ? 0 : mult.intValue());
  }

  public void drawSample() {
    debug("drawSample()", "Entered.");

    // Get a reference to the sample table's internal data vector.
    Vector dataVector = sample.getDataVector();

    // Initialize.
    int popSize = pop.getRowCount();
    int numVars = pop.getColumnCount();
    dataVector.clear();
    sampleBag.clear();
    if (!replace) { Collections.shuffle(popPerm); }

    // Draw a sample.
    for (int i = 0; i < sampleSize; i++) {

      // Pick a population element.
      int popID = replace ? (int)(popSize * Math.random()) :
          ((Integer)popPerm.get(i)).intValue();

      // Add it to the sample table.
      Vector rowData = new Vector(numVars);
      for (int j = 0; j < numVars; j++) {
        rowData.add(pop.getValueAt(popID, j));
      }
      dataVector.add(rowData);

      // Add it to the sample bag.
      sampleBag.put(new Integer(popID),
          new Integer(getMultiplicity(popID) + 1));
    }

    // Manually fire a table model event.
    sample.fireTableDataChanged();
  }

  public void tableChanged(TableModelEvent e) {
    debug("tableChanged()", "Entered.");
    repaint();
  }

  static void debug(String method, String msg) {
    if (debug) { System.err.println("Sampler." + method + ": " + msg); }
  }
}