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 *
 * Copyright 2000-2004 (C) Intalio, Inc. All Rights Reserved.
 *
 * $Id$
 */
package org.exolab.castor.xml.validators;

import java.text.MessageFormat;
import java.util.Collections;
import java.util.LinkedList;
import java.util.List;
import java.util.Locale;
import java.util.ResourceBundle;

import org.exolab.castor.util.RegExpEvaluator;
import org.exolab.castor.xml.ValidationContext;
import org.exolab.castor.xml.ValidationException;

/**
 * A simple abstract class used for validating types which allow the pattern facet.
 *
 * @author <a href="mailto:kvisco-at-intalio.com">Keith Visco</a>
 * @author <a href="mailto:edward.kuns@aspect.com">Edward Kuns</a>
 * @version $Revision$ $Date: 2004-12-11 02:13:52 -0700 (Sat, 11 Dec 2004) $
 */
public abstract class PatternValidator {

  protected static ResourceBundle resourceBundle;

  static {
    resourceBundle = ResourceBundle.getBundle("ValidationMessages", Locale.getDefault());
  }

  /**
   * The regular expressions to match against.
   */
  private LinkedList<String> _patterns = new LinkedList<String>();

  /**
   * If true, object is nillable, otherwise it is not.
   */
  private boolean _nillable = false;

  /**
   * An instance of the regular expression evaluator if necessary.
   */
  private RegExpEvaluator _regex = null;

  /**
   * Creates a new {@link PatternValidator} with no initial regular expression.
   */
  public PatternValidator() {
    super();

  }

  /**
   * Creates a new {@link PatternValidator} with the given initial regular expression.
   *
   * @param pattern the regular expression to validate against
   */
  public PatternValidator(final String pattern) {
    _patterns.add(pattern);
  }

  /**
   * Returns the collection of regular expression patterns.
   *
   * @return the collection of regular expression patterns.
   * @see #setPattern
   */
  public List<String> getPatterns() {
    return Collections.unmodifiableList(_patterns);
  }

  /**
   * Returns whether or not objects validated by this Validator are nillable (are allowed to be
   * null).
   *
   * @return true if null is a valid value
   */
  public boolean isNillable() {
    return _nillable;
  }

  /**
   * Returns true if a regular expression has been set for this PatternValidator.
   *
   * @return true if a regular expression has been set for this PatternValidator
   */
  public boolean hasPattern() {
    return !_patterns.isEmpty();
  }

  /**
   * Sets whether or not objects validated by this Validator are allowed to be null (nillable).
   *
   * @param nillable a boolean that when true indicates null values pass validation
   */
  public void setNillable(final boolean nillable) {
    _nillable = nillable;
  }

  /**
   * Sets the regular expression to validate against.
   *
   * @param pattern the regular expression to use when validating
   */
  public void addPattern(final String pattern) {
    _patterns.add(pattern);
  }

  /**
   * Clear all configured patterns.
   */
  public void clearPatterns() {
    _patterns.clear();
  }

  /**
   * Validates the given String against the regular expression pattern of this PatternValidator.
   *
   * @param str the string to validate
   * @param context the validation context
   *
   * @see #setPattern
   * @throws ValidationException if the given String is not matched by the regular expression
   *         pattern
   */
  public void validate(final String str, final ValidationContext context)
      throws ValidationException {
    if (_patterns.isEmpty()) {
      return;
    }

    if (context == null) {
      throw new IllegalArgumentException(
          resourceBundle.getString("patternValidator.error.exception"));
    }

    if (_regex == null) {
      initEvaluator(context);
    }

    // Loop over all patterns and return (success) if any one of them matches
    for (String pattern : _patterns) {
      _regex.setExpression(pattern);
      if (_regex.matches(str)) {
        return;
      }
    }

    // If we get here, all patterns failed.
    StringBuilder buff = new StringBuilder("'" + str + "'");
    if (_patterns.size() == 1) {
      buff.append(
          MessageFormat.format(resourceBundle.getString("patternValidator.error.pattern.not.match"),
              new Object[] {_patterns.getFirst()}));
    } else {
      StringBuilder patterns = new StringBuilder();
      for (String pattern : _patterns) {
        patterns.append('\"');
        patterns.append(pattern);
        patterns.append('\"');
      }

      buff.append(MessageFormat.format(
          resourceBundle.getString("patternValidator.error.pattern.not.match.any"),
          new Object[] {patterns.toString()}));
    }
    throw new ValidationException(buff.toString());
  }

  /**
   * Validates the given Object.
   *
   * @param object the Object to validate
   * @param context the ValidationContext
   * @throws ValidationException if the given String is not matched by the regular expression
   *         pattern
   */
  public void validate(final Object object, final ValidationContext context)
      throws ValidationException {
    if (object == null) {
      if (!_nillable) {
        String err = resourceBundle.getString("patternValidator.error.cannot.validate.null.object");
        throw new ValidationException(err);
      }
      return;
    }
    validate(object.toString(), context);
  }

  /**
   * Initializes the regular expression validator.
   * 
   * @param context the ValidationContext
   */
  private void initEvaluator(final ValidationContext context) {
    _regex = context.getInternalContext().getRegExpEvaluator();
    if (_regex == null && hasPattern()) {
      throw new IllegalStateException(
          resourceBundle.getString("patternValidator.error.exception.noPatterns"));
    }
  }

}
