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Nuts'n'Bolts Utilities
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/*
 * Copyright (c) 2007, 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016 David Berkman
 * 
 * This file is part of the SmallMind Code Project.
 * 
 * The SmallMind Code Project is free software, you can redistribute
 * it and/or modify it under either, at your discretion...
 * 
 * 1) The terms of GNU Affero General Public License as published by the
 * Free Software Foundation, either version 3 of the License, or (at
 * your option) any later version.
 * 
 * ...or...
 * 
 * 2) The terms of the Apache License, Version 2.0.
 * 
 * The SmallMind Code Project 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 or Apache License for more details.
 * 
 * You should have received a copy of the GNU Affero General Public License
 * and the Apache License along with the SmallMind Code Project. If not, see
 *  or .
 * 
 * Additional permission under the GNU Affero GPL version 3 section 7
 * ------------------------------------------------------------------
 * If you modify this Program, or any covered work, by linking or
 * combining it with other code, such other code is not for that reason
 * alone subject to any of the requirements of the GNU Affero GPL
 * version 3.
 */
package org.smallmind.nutsnbolts.util;

import java.util.regex.Pattern;

public class DotNotation {

  private static enum TranslationState {

    START, POST_DOT, WILD, NORMAL
  }

  private static enum WildState {

    STAR, QUESTION, TAME
  }

  private Pattern pattern;
  private String notation;

  public DotNotation (String notation)
    throws DotNotationException {

    this.notation = notation;

    pattern = Pattern.compile(validateAsRegEx(notation));
  }

  public String getNotation () {

    return notation;
  }

  public Pattern getPattern () {

    return pattern;
  }

  public static String validateAsRegEx (String notation)
    throws DotNotationException {

    StringBuilder patternBuilder;
    TranslationState translationState;
    WildState wildState;
    char curChar;
    int count;

    patternBuilder = new StringBuilder();
    patternBuilder.append('^');
    translationState = TranslationState.START;
    wildState = WildState.TAME;

    for (count = 0; count < notation.length(); count++) {
      curChar = notation.charAt(count);
      switch (curChar) {
        case '.':
          if (translationState.equals(TranslationState.POST_DOT)) {
            throw new DotNotationException("Empty component in the pattern");
          }
          else if (translationState.equals(TranslationState.START)) {
            throw new DotNotationException("The pattern can not begin with '.'");
          }

          if (translationState.equals(TranslationState.NORMAL)) {
            patternBuilder.append(')');
          }

          patternBuilder.append("(\\.|$)");
          translationState = TranslationState.POST_DOT;

          break;
        case '*':
          if (translationState.equals(TranslationState.WILD)) {
            throw new DotNotationException("Wildcards must either be followed by '.' or terminate the pattern");
          }
          else if (translationState.equals(TranslationState.NORMAL)) {
            throw new DotNotationException("Wildcards must either start the pattern or be preceded by '.'");
          }
          else if (!wildState.equals(WildState.TAME)) {
            throw new DotNotationException("Any wildcard followed by '*' is redundant");
          }

          patternBuilder.append("(.+|$)");
          translationState = TranslationState.WILD;
          wildState = WildState.STAR;

          break;
        case '?':
          if (translationState.equals(TranslationState.WILD)) {
            throw new DotNotationException("Wildcards must either be followed by '.' or terminate the pattern");
          }
          else if (translationState.equals(TranslationState.NORMAL)) {
            throw new DotNotationException("Wildcards must either start the pattern or be preceded by '.'");
          }
          else if (wildState.equals(WildState.STAR)) {
            throw new DotNotationException("Following '*' with '?' is redundant");
          }

          patternBuilder.append("([^.]+|$)");
          translationState = TranslationState.WILD;
          wildState = WildState.QUESTION;

          break;
        default:
          if (!Character.isJavaIdentifierPart(curChar)) {
            throw new DotNotationException("Components must be composed of valid Java identifiers");
          }
          else if (translationState.equals(TranslationState.WILD)) {
            throw new DotNotationException("Wildcards must either be followed by '.' or terminate the pattern");
          }

          if ((translationState.equals(TranslationState.POST_DOT)) || (translationState.equals(TranslationState.START))) {
            patternBuilder.append('(');
          }

          patternBuilder.append(curChar);
          translationState = TranslationState.NORMAL;
          wildState = WildState.TAME;
      }
    }

    if (translationState.equals(TranslationState.POST_DOT)) {
      throw new DotNotationException("The pattern can not end with '.'");
    }
    else if (translationState.equals(TranslationState.NORMAL)) {
      patternBuilder.append(')');
    }

    patternBuilder.append('$');

    return patternBuilder.toString();
  }
}