content: /*
   *    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 2 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, write to the Free Software
   *    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
   */
  
  /*
   * NGramTokenizer.java
   * Copyright (C) 2007 University of Waikato
   */
  
  package weka.core.tokenizers;
  
  import weka.core.Option;
  import weka.core.RevisionUtils;
  import weka.core.Utils;
  
  import java.util.Enumeration;
  import java.util.LinkedList;
  import java.util.Vector;
  
  /**
   <!-- globalinfo-start -->
   * Splits a string into an n-gram with min and max grams.
   * <p/>
   <!-- globalinfo-end -->
   * 
   <!-- options-start -->
   * Valid options are: <p/>
   * 
   * <pre> -delimiters &lt;value&gt;
   *  The delimiters to use
   *  (default ' \r\n\t.,;:'"()?!').</pre>
   * 
   * <pre> -max &lt;int&gt;
   *  The max size of the Ngram (default = 3).</pre>
   * 
   * <pre> -min &lt;int&gt;
   *  The min size of the Ngram (default = 1).</pre>
   * 
   <!-- options-end -->
   *
   * @author  Sebastian Germesin (sebastian.germesin@dfki.de)
   * @author  FracPete (fracpete at waikato dot ac dot nz)
   * @version $Revision: 5953 $
   */
  public class NGramTokenizer
    extends CharacterDelimitedTokenizer {
  
    /** for serialization */
    private static final long serialVersionUID = -2181896254171647219L;
  
    /** the maximum number of N */
    protected int m_NMax = 3;
    
    /** the minimum number of N */
    protected int m_NMin = 1;
    
    /** the current length of the N-grams */
    protected int m_N;
    
    /** the number of strings available */
    protected int m_MaxPosition;
    
    /** the current position for returning elements */
    protected int m_CurrentPosition;
    
    /** all the available grams */
    protected String[] m_SplitString;
    
    /**
     * Returns a string describing the stemmer
     * 
     * @return 		a description suitable for displaying in the 
     * 			explorer/experimenter gui
     */
    public String globalInfo() {
      return "Splits a string into an n-gram with min and max grams.";
    }
    
    /**
     * Returns an enumeration of all the available options..
     *
     * @return 		an enumeration of all available options.
     */
    public Enumeration listOptions() {
      Vector<Option>	result;
      Enumeration enm;
      
      result = new Vector<Option>();
      
      enm = super.listOptions();
      while (enm.hasMoreElements())
        result.addElement((Option)enm.nextElement());
  
      result.addElement(new Option(
  	"\tThe max size of the Ngram (default = 3).",
  	"max", 1, "-max <int>"));
  
      result.addElement(new Option(
  	"\tThe min size of the Ngram (default = 1).",
  	"min", 1, "-min <int>"));
      
      return result.elements();
    }
    
    /**
     * Gets the current option settings for the OptionHandler.
     *
     * @return 		the list of current option settings as an array of 
     * 			strings
     */
    public String[] getOptions() {
      Vector<String>	result;
      String[]		options;
      int			i;
      
      result = new Vector<String>();
      
      options = super.getOptions();
      for (i = 0; i < options.length; i++)
        result.add(options[i]);
      
      result.add("-max");
      result.add("" + getNGramMaxSize());
  
      result.add("-min");
      result.add("" + getNGramMinSize());
  
      return result.toArray(new String[result.size()]);
    }
  
    /**
     * Parses a given list of options. <p/>
     *
     <!-- options-start -->
     * Valid options are: <p/>
     * 
     * <pre> -delimiters &lt;value&gt;
     *  The delimiters to use
     *  (default ' \r\n\t.,;:'"()?!').</pre>
     * 
     * <pre> -max &lt;int&gt;
     *  The max size of the Ngram (default = 3).</pre>
     * 
     * <pre> -min &lt;int&gt;
     *  The min size of the Ngram (default = 1).</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	value;
      
      super.setOptions(options);
  
      value = Utils.getOption("max", options);
      if (value.length() != 0)
        setNGramMaxSize(Integer.parseInt(value));
      else
        setNGramMaxSize(3);
  
      value = Utils.getOption("min", options);
      if (value.length() != 0)
        setNGramMinSize(Integer.parseInt(value));
      else
        setNGramMinSize(1);
    }
    
    /**
     * Gets the max N of the NGram.
     * 
     * @return 		the size (N) of the NGram.
     */
    public int getNGramMaxSize() {
      return m_NMax;
    }
  
    /**
     * Sets the max size of the Ngram.
     * 
     * @param value 	the size of the NGram.
     */
    public void setNGramMaxSize(int value) {
      if (value < 1)
        m_NMax = 1;
      else
        m_NMax = value;
    }
  
    /**
     * Returns the tip text for this property.
     *
     * @return 		tip text for this property suitable for
     * 			displaying in the explorer/experimenter gui
     */
    public String NGramMaxSizeTipText() {
      return "The max N of the NGram.";
    }
  
    /**
     * Sets the min size of the Ngram.
     * 
     * @param value 	the size of the NGram.
     */
    public void setNGramMinSize(int value) {
      if (value < 1)
        m_NMin = 1;
      else
        m_NMin = value;
    }
  
    /**
     * Gets the min N of the NGram.
     * 
     * @return 		the size (N) of the NGram.
     */
    public int getNGramMinSize() {
      return m_NMin;
    }
  
    /**
     * Returns the tip text for this property.
     *
     * @return 		tip text for this property suitable for
     * 			displaying in the explorer/experimenter gui
     */
    public String NGramMinSizeTipText() {
      return "The min N of the NGram.";
    }
  
    /**
     * returns true if there's more elements available
     * 
     * @return		true if there are more elements available
     */
    public boolean hasMoreElements() {
      return (m_CurrentPosition < m_MaxPosition && 
  	m_N - 1 + m_CurrentPosition < m_MaxPosition && 
  	m_N >= m_NMin);
    }
    
    /**
     * Returns N-grams and also (N-1)-grams and .... and 1-grams.
     * 
     * @return		the next element
     */
    public Object nextElement() {
      String retValue = "";
      
      for (int i = 0; i < m_N && i + m_CurrentPosition < m_MaxPosition; i++)
        retValue += " " + m_SplitString[m_CurrentPosition + i];
      
      m_CurrentPosition++;
      
      if (m_CurrentPosition + m_N - 1 == m_MaxPosition) {
        m_CurrentPosition = 0;
        m_N--;
      }
  
      return retValue.trim();
    }
  
    /** 
     * filters out empty strings in m_SplitString and
     * replaces m_SplitString with the cleaned version.
     * 
     * @see #m_SplitString
     */
    protected void filterOutEmptyStrings() {
      String[] newSplit;
      LinkedList<String> clean = new LinkedList<String>();
  
      for (int i = 0; i < m_SplitString.length; i++) {
        if (!m_SplitString[i].equals(""))
  	clean.add(m_SplitString[i]);
      }
  
      newSplit = new String[clean.size()];
      for (int i = 0; i < clean.size(); i++) 
        newSplit[i] = clean.get(i);
  
      m_SplitString = newSplit;
    }
    
    /**
     * Sets the string to tokenize. Tokenization happens immediately.
     * 
     * @param s		the string to tokenize
     */
    public void tokenize(String s) {
      m_N           = m_NMax;
      m_SplitString = s.split("[" + getDelimiters() + "]");
      
      filterOutEmptyStrings();
  
      m_CurrentPosition = 0;
      m_MaxPosition     = m_SplitString.length;
    }
    
    /**
     * Returns the revision string.
     * 
     * @return		the revision
     */
    public String getRevision() {
      return RevisionUtils.extract("$Revision: 5953 $");
    }
  
    /**
     * Runs the tokenizer with the given options and strings to tokenize.
     * The tokens are printed to stdout.
     * 
     * @param args	the commandline options and strings to tokenize
     */
    public static void main(String[] args) {
      runTokenizer(new NGramTokenizer(), args);
    }
  }
  
  