/*
 *   This program is free software: you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation, either version 3 of the License, or
 *   (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

/*
 *    RemoveUseless.java
 *    Copyright (C) 2002-2012 University of Waikato, Hamilton, New Zealand
 *
 */

package weka.filters.unsupervised.attribute;

import java.util.Enumeration;
import java.util.Vector;

import weka.core.AttributeStats;
import weka.core.Capabilities;
import weka.core.Capabilities.Capability;
import weka.core.Instance;
import weka.core.Instances;
import weka.core.Option;
import weka.core.OptionHandler;
import weka.core.RevisionUtils;
import weka.core.Utils;
import weka.filters.Filter;
import weka.filters.UnsupervisedFilter;

/** 
 <!-- globalinfo-start -->
 * This filter removes attributes that do not vary at all or that vary too much. 
 * All constant attributes are deleted automatically, along with any that exceed 
 * #the maximum percentage of variance parameter. The maximum variance test is only applied to nominal attributes.
 * <p/>
 <!-- globalinfo-end -->
 * 
 <!-- options-start -->
 * Valid options are: <p/>
 * 
 * <pre> -M &lt;max variance %&gt;
 *  Maximum variance percentage allowed (default 99)</pre>
 * 
 <!-- options-end -->
 *
 * @author Richard Kirkby (rkirkby@cs.waikato.ac.nz)
 * @version $Revision: 8034 $
 */
public class RemoveUseless 
  extends Filter 
  implements UnsupervisedFilter, OptionHandler {
  
  /** for serialization */
  static final long serialVersionUID = -8659417851407640038L;

  /** The filter used to remove attributes */
  protected Remove m_removeFilter = null;

  /** The type of attribute to delete */
  protected double m_maxVariancePercentage = 99.0;

  /** 
   * Returns the Capabilities of this filter.
   *
   * @return            the capabilities of this object
   * @see               Capabilities
   */
  public Capabilities getCapabilities() {
    Capabilities result = super.getCapabilities();

    // attributes
    result.enable(Capability.NOMINAL_ATTRIBUTES);
    result.enable(Capability.NUMERIC_ATTRIBUTES);
    result.enable(Capability.DATE_ATTRIBUTES);
    result.enable(Capability.STRING_ATTRIBUTES);
    result.enable(Capability.MISSING_VALUES);
    
    // class
    result.enableAllClasses();
    result.enable(Capability.MISSING_CLASS_VALUES);
    result.enable(Capability.NO_CLASS);
    
    return result;
  }

  /**
   * Sets the format of the input instances.
   *
   * @param instanceInfo an Instances object containing the input instance
   * structure (any instances contained in the object are ignored - only the
   * structure is required).
   * @return true if the outputFormat may be collected immediately
   * @throws Exception if the inputFormat can't be set successfully 
   */ 
  public boolean setInputFormat(Instances instanceInfo) throws Exception {

    super.setInputFormat(instanceInfo);
    m_removeFilter = null;
    return false;
  }

  /**
   * Input an instance for filtering.
   *
   * @param instance the input instance
   * @return true if the filtered instance may now be
   * collected with output().
   */
  public boolean input(Instance instance) {

    if (getInputFormat() == null) {
      throw new IllegalStateException("No input instance format defined");
    }
    if (m_NewBatch) {
      resetQueue();
      m_NewBatch = false;
    }
    if (m_removeFilter != null) {
      m_removeFilter.input(instance);
      Instance processed = m_removeFilter.output();
      processed.setDataset(getOutputFormat());
      copyValues(processed, false, instance.dataset(), getOutputFormat());
      push(processed);
      return true;
    }
    bufferInput(instance);
    return false;
  }

  /**
   * Signify that this batch of input to the filter is finished.
   *
   * @return true if there are instances pending output
   * @throws Exception if no input format defined
   */  
  public boolean batchFinished() throws Exception {

    if (getInputFormat() == null) {
      throw new IllegalStateException("No input instance format defined");
    }
    if (m_removeFilter == null) {

      // establish attributes to remove from first batch

      Instances toFilter = getInputFormat();
      int[] attsToDelete = new int[toFilter.numAttributes()];
      int numToDelete = 0;
      for(int i = 0; i < toFilter.numAttributes(); i++) {
	if (i==toFilter.classIndex()) continue; // skip class
	AttributeStats stats = toFilter.attributeStats(i);
	if (stats.missingCount == toFilter.numInstances()) {
	  attsToDelete[numToDelete++] = i;
	} else if (stats.distinctCount < 2) {
	  // remove constant attributes
	  attsToDelete[numToDelete++] = i;
	} else if (toFilter.attribute(i).isNominal()) {
	  // remove nominal attributes that vary too much
	  double variancePercent = (double) stats.distinctCount
	    / (double)(stats.totalCount - stats.missingCount) * 100.0;
	  if (variancePercent > m_maxVariancePercentage) {
	      attsToDelete[numToDelete++] = i;
	  }
	}
      }
      
      int[] finalAttsToDelete = new int[numToDelete];
      System.arraycopy(attsToDelete, 0, finalAttsToDelete, 0, numToDelete);
      
      m_removeFilter = new Remove();
      m_removeFilter.setAttributeIndicesArray(finalAttsToDelete);
      m_removeFilter.setInvertSelection(false);
      m_removeFilter.setInputFormat(toFilter);
      
      for (int i = 0; i < toFilter.numInstances(); i++) {
	m_removeFilter.input(toFilter.instance(i));
      }
      m_removeFilter.batchFinished();

      Instance processed;
      Instances outputDataset = m_removeFilter.getOutputFormat();
    
      // restore old relation name to hide attribute filter stamp
      outputDataset.setRelationName(toFilter.relationName());
    
      setOutputFormat(outputDataset);
      while ((processed = m_removeFilter.output()) != null) {
	processed.setDataset(outputDataset);
	push(processed);
      }
    }
    flushInput();
    
    m_NewBatch = true;
    return (numPendingOutput() != 0);
  }

  /**
   * Returns an enumeration describing the available options.
   *
   * @return an enumeration of all the available options.
   */
  public Enumeration listOptions() {

    Vector newVector = new Vector(1);

    newVector.addElement(new Option(
				    "\tMaximum variance percentage allowed (default 99)",
				    "M", 1, "-M <max variance %>"));


    return newVector.elements();
  }

  /**
   * Parses a given list of options. <p/>
   * 
   <!-- options-start -->
   * Valid options are: <p/>
   * 
   * <pre> -M &lt;max variance %&gt;
   *  Maximum variance percentage allowed (default 99)</pre>
   * 
   <!-- options-end -->
   *
   * @param options the list of options as an array of strings
   * @throws Exception if an option is not supported
   */
  public void setOptions(String[] options) throws Exception {
    
    String mString = Utils.getOption('M', options);
    if (mString.length() != 0) {
      setMaximumVariancePercentageAllowed((int) Double.valueOf(mString).doubleValue());
    } else {
      setMaximumVariancePercentageAllowed(99.0);
    }

    if (getInputFormat() != null) {
      setInputFormat(getInputFormat());
    }
  }

  /**
   * Gets the current settings of the filter.
   *
   * @return an array of strings suitable for passing to setOptions
   */
  public String [] getOptions() {

    String [] options = new String [2];
    int current = 0;

    options[current++] = "-M";
    options[current++] = "" + getMaximumVariancePercentageAllowed();
    
    while (current < options.length) {
      options[current++] = "";
    }
    return options;
  }

  /**
   * Returns a string describing this filter
   *
   * @return a description of the filter suitable for
   * displaying in the explorer/experimenter gui
   */
  public String globalInfo() {
    return 
        "This filter removes attributes that do not vary at all or that vary "
      + "too much. All constant attributes are deleted automatically, along "
      + "with any that exceed the maximum percentage of variance parameter. "
      + "The maximum variance test is only applied to nominal attributes.";
  }

  /**
   * Returns the tip text for this property
   *
   * @return tip text for this property suitable for
   * displaying in the explorer/experimenter gui
   */
  public String maximumVariancePercentageAllowedTipText() {

    return "Set the threshold for the highest variance allowed before a nominal attribute will be deleted."
      + "Specifically, if (number_of_distinct_values / total_number_of_values * 100)"
      + " is greater than this value then the attribute will be removed.";
  }

  /**
   * Sets the maximum variance attributes are allowed to have before they are
   * deleted by the filter.
   *
   * @param maxVariance the maximum variance allowed, specified as a percentage
   */
  public void setMaximumVariancePercentageAllowed(double maxVariance) {
    
    m_maxVariancePercentage = maxVariance;
  }

  /**
   * Gets the maximum variance attributes are allowed to have before they are
   * deleted by the filter.
   *
   * @return the maximum variance allowed, specified as a percentage
   */
  public double getMaximumVariancePercentageAllowed() {

    return m_maxVariancePercentage;
  }
  
  /**
   * Returns the revision string.
   * 
   * @return		the revision
   */
  public String getRevision() {
    return RevisionUtils.extract("$Revision: 8034 $");
  }

  /**
   * Main method for testing this class.
   *
   * @param argv should contain arguments to the filter: use -h for help
   */
  public static void main(String [] argv) {
    runFilter(new RemoveUseless(), argv);
  }
}
