source: 3thparty/jmessenger/src/com/swabunga/spell/engine/SpellDictionaryASpell.java @ 3952

/* Created by bgalbs on Jan 30, 2003 at 11:45:25 PM */
package com.swabunga.spell.engine;

import java.io.File;
import java.io.IOException;
import java.io.Reader;
import java.security.InvalidParameterException;
import java.util.*;

/**
 * Container for various methods that any <code>SpellDictionary</code> will use.
 * Based on the original Jazzy <a href="http://aspell.net/">aspell</a> port.
 * <p/>
 *
 *
 */
public abstract class SpellDictionaryASpell implements SpellDictionary {


  /** The reference to a Transformator, used to transform a word into it's phonetic code. */
  protected Transformator tf;

  public SpellDictionaryASpell(File phonetic) throws IOException {
    if (phonetic == null)
      tf = new DoubleMeta();
    else
      tf = new GenericTransformator(phonetic);
  }

  public SpellDictionaryASpell(File phonetic, String encoding) throws IOException {
    if (phonetic == null)
      tf = new DoubleMeta();
    else
      tf = new GenericTransformator(phonetic, encoding);
  }

  public SpellDictionaryASpell(Reader phonetic) throws IOException {
    if (phonetic == null)
      tf = new DoubleMeta();
    else
      tf = new GenericTransformator(phonetic);
  }


  /**
   * Returns a list of Word objects that are the suggestions to an
   * incorrect word.
   * <p>
   * @param word Suggestions for given mispelt word
   * @param threshold The lower boundary of similarity to mispelt word
   * @return Vector a List of suggestions
   */
  public List getSuggestions(String word, int threshold) {

    Hashtable nearmisscodes = new Hashtable();
    String code = getCode(word);

    // add all words that have the same phonetics
    nearmisscodes.put(code, code);
    Vector phoneticList = getWordsFromCode(word, nearmisscodes);

    // do some tranformations to pick up more results
    //interchange
    nearmisscodes = new Hashtable();
    char[] charArray = word.toCharArray();
    for (int i = 0; i < word.length() - 1; i++) {
      char a = charArray[i];
      char b = charArray[i + 1];
      charArray[i] = b;
      charArray[i + 1] = a;
      String s = getCode(new String(charArray));
      nearmisscodes.put(s, s);
      charArray[i] = a;
      charArray[i + 1] = b;
    }

    char[] replacelist = tf.getReplaceList();

    //change
    charArray = word.toCharArray();
    for (int i = 0; i < word.length(); i++) {
      char original = charArray[i];
      for (int j = 0; j < replacelist.length; j++) {
        charArray[i] = replacelist[j];
        String s = getCode(new String(charArray));
        nearmisscodes.put(s, s);
      }
      charArray[i] = original;
    }

    //add
    charArray = (word += " ").toCharArray();
    int iy = charArray.length - 1;
    while (true) {
      for (int j = 0; j < replacelist.length; j++) {
        charArray[iy] = replacelist[j];
        String s = getCode(new String(charArray));
        nearmisscodes.put(s, s);
      }
      if (iy == 0)
        break;
      charArray[iy] = charArray[iy - 1];
      --iy;
    }

    //delete
    word = word.trim();
    charArray = word.toCharArray();
    char[] charArray2 = new char[charArray.length - 1];
    for (int ix = 0; ix < charArray2.length; ix++) {
      charArray2[ix] = charArray[ix];
    }
    char a, b;
    a = charArray[charArray.length - 1];
    int ii = charArray2.length;
    while (true) {
      String s = getCode(new String(charArray));
      nearmisscodes.put(s, s);
      if (ii == 0)
        break;
      b = a;
      a = charArray2[ii - 1];
      charArray2[ii - 1] = b;
      --ii;
    }

    nearmisscodes.remove(code); //already accounted for in phoneticList

    Vector wordlist = getWordsFromCode(word, nearmisscodes);

    if (wordlist.size() == 0 && phoneticList.size() == 0)
      addBestGuess(word, phoneticList);


    // We sort a Vector at the end instead of maintaining a
    // continously sorted TreeSet because everytime you add a collection
    // to a treeset it has to be resorted. It's better to do this operation
    // once at the end.

    Collections.sort(phoneticList, new Word()); //always sort phonetic matches along the top
    Collections.sort(wordlist, new Word()); //the non-phonetic matches can be listed below

    phoneticList.addAll(wordlist);
    return phoneticList;
  }

  /**
   * When we don't come up with any suggestions (probably because the threshold was too strict),
   * then pick the best guesses from the those words that have the same phonetic code.
   * @param word - the word we are trying spell correct
   * @param wordList - the linked list that will get the best guess
   */
  private void addBestGuess(String word, Vector wordList) {
    if (wordList.size() != 0)
      throw new InvalidParameterException("the wordList vector must be empty");

    int bestScore = Integer.MAX_VALUE;

    String code = getCode(word);
    List simwordlist = getWords(code);

    LinkedList candidates = new LinkedList();

    for (Iterator j = simwordlist.iterator(); j.hasNext();) {
      String similar = (String) j.next();
      int distance = EditDistance.getDistance(word, similar);
      if (distance <= bestScore) {
        bestScore = distance;
        Word goodGuess = new Word(similar, distance);
        candidates.add(goodGuess);
      }
    }

    //now, only pull out the guesses that had the best score
    for (Iterator iter = candidates.iterator(); iter.hasNext();) {
      Word candidate = (Word) iter.next();
      if (candidate.getCost() == bestScore)
        wordList.add(candidate);
    }

  }

  private Vector getWordsFromCode(String word, Hashtable codes) {
    Configuration config = Configuration.getConfiguration();
    Vector result = new Vector();
    final int configDistance = config.getInteger(Configuration.SPELL_THRESHOLD);

    for (Enumeration i = codes.keys(); i.hasMoreElements();) {
      String code = (String) i.nextElement();

      List simwordlist = getWords(code);
      for (Iterator iter = simwordlist.iterator(); iter.hasNext();) {
        String similar = (String) iter.next();
        int distance = EditDistance.getDistance(word, similar);
        if (distance < configDistance) {
          Word w = new Word(similar, distance);
          result.addElement(w);
        }
      }
    }
    return result;
  }

  /**
   * Returns the phonetic code representing the word.
   */
  public String getCode(String word) {
    return tf.transform(word);
  }

  /**
   * Returns a list of words that have the same phonetic code.
   */
  protected abstract List getWords(String phoneticCode);

  /**
   * Returns true if the word is correctly spelled against the current word list.
   */
  public boolean isCorrect(String word) {
    List possible = getWords(getCode(word));
    if (possible.contains(word))
      return true;
    //JMH should we always try the lowercase version. If I dont then capitalised
    //words are always returned as incorrect.
    else if (possible.contains(word.toLowerCase()))
      return true;
    return false;
  }
}