package org.cyclopsgroup.caff.token;
   
   /**
    * An implementation that escapes special character with an escape character
    *
    * @author <a href="mailto:jiaqi@cyclopsgroup.org">Jiaqi Guo</a>
    */
   public class EscapingValueTokenizer implements ValueTokenizer {
     private static enum ProcessingState {
      /** Followd by escape character */
      ESCAPING,
      /** Ready for new word */
      READY,
      /** Appending a word */
      WORD;
    }
  
    private final char delimiter;
  
    private final char escaper;
  
    /**
     * Default constructor sets escape character with back slash, and imply white space as delimiter
     */
    public EscapingValueTokenizer() {
      this(' ', '\\');
    }
  
    /**
     * @param delimiter Delimiter character
     * @param escaper Given escape character
     */
    public EscapingValueTokenizer(char delimiter, char escaper) {
      this.escaper = escaper;
      this.delimiter = delimiter;
    }
  
    @Override
    public String escape(String output) {
      if (output.indexOf(escaper) == -1 && output.indexOf(delimiter) == -1) {
        return output;
      }
      StringBuffer sb = new StringBuffer();
      for (int i = 0, j = 0; i < output.length(); ) {
        int e = output.indexOf(escaper, i);
        int d = output.indexOf(delimiter, i);
        if (e == -1 && d == -1) {
          sb.append(output.substring(i));
          break;
        }
        if (e >= 0 && d >= 0) {
          j = Math.min(e, d);
        } else {
          j = Math.max(e, d);
        }
        sb.append(output.substring(i, j)).append(escaper).append(output.charAt(j));
        i = ++j;
      }
      return sb.toString();
    }
  
    /** @return Delimiter character */
    public final char getDelimiter() {
      return delimiter;
    }
  
    /** @return Escape character */
    public final char getEscaper() {
      return escaper;
    }
  
    @Override
    public void parse(CharSequence input, TokenEventHandler handler) {
      ProcessingState state = ProcessingState.READY;
      StringBuilder word = null;
      int wordStart = 0;
      for (int i = 0; i < input.length(); i++) {
        char c = input.charAt(i);
        switch (state) {
          case READY:
            if (c == delimiter) {
              continue;
            } else {
              wordStart = i;
              word = new StringBuilder();
              if (c == escaper) {
                state = ProcessingState.ESCAPING;
              } else {
                state = ProcessingState.WORD;
                word.append(c);
              }
            }
            break;
          case WORD:
            if (c == delimiter) {
              state = ProcessingState.READY;
              TokenEvent ev = new TokenEvent(word.toString(), wordStart, i, true);
              handler.handleEvent(ev);
              word = null;
           } else if (c == escaper) {
             state = ProcessingState.ESCAPING;
           } else {
             word.append(c);
           }
           break;
         case ESCAPING:
           state = ProcessingState.WORD;
           word.append(c);
       }
     }
     if (word != null) {
       TokenEvent ev = new TokenEvent(word.toString(), wordStart, input.length(), false);
       handler.handleEvent(ev);
     }
   }
 }