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 *
 * Copyright 1999-2002 (C) Intalio, Inc. All Rights Reserved.
 *
 * $Id$
 */
package org.exolab.castor.xml.validators;

/**
 * A static class for performing simple validation.
 *
 * @author <a href="mailto:kvisco@intalio.com">Keith Visco</a>
 * @version $Revision$ $Date: 2003-03-03 00:05:44 -0700 (Mon, 03 Mar 2003) $
 */
public final class ValidationUtils {

  // ----------------/
  // - Constructors -/
  // ----------------/

  /**
   * No-arg constructor.
   */
  private ValidationUtils() {
    super();
  }

  // ------------------/
  // - Public Methods -/
  // ------------------/

  /**
   * Checks the given character to determine if it is a valid CombiningChar as defined by the W3C
   * XML 1.0 Recommendation.
   * <p>
   * FIXME: This method needs to be properly implemented.
   * 
   * @param ch THe character to check.
   *
   * @return true if the given character is a CombiningChar
   */
  public static boolean isCombiningChar(final char ch) {
    // -- NOTE: THIS METHOD IS NOT COMPLETE
    return false;
  } // -- isCombiningChar

  /**
   * Checks a character to see if it is a digit or not.
   * 
   * @param ch the character to check
   * @return true if the given character is a digit
   */
  public static boolean isDigit(final char ch) {
    return Character.isDigit(ch);
  } // -- isDigit

  /**
   * Checks a character to see if it is a letter or not.
   * 
   * @param ch the character to check
   * @return true if the given character is a letter
   */
  public static boolean isLetter(final char ch) {
    return Character.isLetter(ch);
  } // -- isLetter

  /**
   * Checks all characters of the given String to determine if they syntactically match the
   * production of an NCName as defined by the W3C XML Namespaces recommendation.
   *
   * @param str the String to check
   * @return true if the given String follows the Syntax of an NCName
   */
  public static boolean isNCName(final String str) {
    if (str == null || str.length() == 0) {
      return false;
    }

    char[] chars = str.toCharArray();

    // -- make sure String starts with a letter or '_'
    char ch = chars[0];
    if (!isLetter(ch) && ch != '_') {
      return false;
    }

    for (int i = 1; i < chars.length; i++) {
      if (!isNCNameChar(chars[i])) {
        return false;
      }
    }
    return true;
  } // -- isNCName

  /**
   * Checks the the given character to determine if it is a valid NCNameChar as defined by the W3C
   * XML Namespaces recommendation.
   *
   * @param ch the char to check
   * @return true if the given char is an NCNameChar
   */
  public static boolean isNCNameChar(final char ch) {
    if (isLetter(ch) || isDigit(ch)) {
      return true;
    }

    if (isExtender(ch) || isCombiningChar(ch)) {
      return true;
    }

    switch (ch) {
      case '.':
      case '-':
      case '_':
        return true;
      default:
        return false;
    }
  } // -- isNCNameChar

  /**
   * Checks all characters of the given String to determine if they syntactically match the
   * production of an NMToken.
   *
   * @param str the String to check
   * @return true if the given String follows the Syntax of an NMToken
   */
  public static boolean isNMToken(final String str) {
    if (str == null) {
      return false;
    }

    char[] chars = str.toCharArray();

    for (int i = 0; i < chars.length; i++) {
      char ch = chars[i];
      if (isLetter(ch) || isDigit(ch) || isExtender(ch) || isCombiningChar(ch)) {
        continue;
      }

      switch (ch) {
        case '.':
        case '-':
        case '_':
        case ':':
          break;
        default:
          return false;
      }
    }
    return true;
  } // -- isNMToken

  /**
   * Checks all characters of the given String to determine if they syntactically match the
   * production of a CDATA.
   *
   * @param str the String to check
   * @return true if the given String follows the Syntax of an NMToken
   */
  public static boolean isCDATA(final String str) {
    if (str == null) {
      return false;
    }

    char[] chars = str.toCharArray();

    for (int i = 0; i < chars.length; i++) {
      char ch = chars[i];
      switch (ch) {
        case '\r':
        case '\n':
        case '\t':
          return false;
        default:
          continue;
      }
    }
    return true;
  } // -- isCDATA

  /**
   * Returns true if the given character is a valid XML Extender character, according to the XML 1.0
   * specification.
   *
   * @param ch the character to check
   * @return true if the character is a valid XML Extender character
   */
  public static boolean isExtender(final char ch) {
    if ((ch >= 0x3031) && (ch <= 0x3035)) {
      return true;
    }

    if ((ch >= 0x30FC) && (ch <= 0x30FE)) {
      return true;
    }

    switch (ch) {
      case 0x00B7:
      case 0x02D0:
      case 0x02D1:
      case 0x0387:
      case 0x0640:
      case 0x0E46:
      case 0x0EC6:
      case 0x3005:
      case 0x309D:
      case 0x309E:
        return true;
      default:
        break;
    }
    return false;
  } // -- isExtender

  /**
   * Checks all characters of the given String to determine if they syntactically match the
   * production of an QName as defined by the W3C XML Namespaces recommendation.
   *
   * @param str the String to check
   * @return true if the given String follows the Syntax of an QName
   */
  public static boolean isQName(final String str) {
    if (str == null || str.length() == 0) {
      return false;
    }

    char[] chars = str.toCharArray();

    // -- make sure String starts with a letter or '_'
    char ch = chars[0];
    if (!isLetter(ch) && ch != '_') {
      return false;
    }

    for (int i = 1; i < chars.length; i++) {
      if (chars[i] == ':') {
        continue;
      }

      if (!isNCNameChar(chars[i])) {
        return false;
      }
    }
    return true;
  } // -- isQName

} // -- Validator
