/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.wicket.validation.validator;

import java.util.regex.Pattern;

import org.apache.wicket.markup.html.form.FormComponent;
import org.apache.wicket.util.parse.metapattern.MetaPattern;
import org.apache.wicket.validation.IValidatable;
import org.apache.wicket.validation.IValidationError;
import org.apache.wicket.validation.IValidator;
import org.apache.wicket.validation.ValidationError;

/**
 * Validates an {@link IValidatable} by matching the value against a regular expression pattern. A
 * <code>PatternValidator</code> can be constructed with either a Java regular expression (compiled
 * or not) or a {@link MetaPattern}. If the pattern matches against the value then it is considered
 * valid. If the pattern does not match, the an {@link IValidationError} will be reported on the
 * {@link IValidatable}.
 * <p>
 * For example, to restrict a field to only digits, you might add a <code>PatternValidator</code>
 * constructed with the pattern "\d+". Another way to do the same thing would be to construct the
 * <code>PatternValidator</code> passing in {@link MetaPattern#DIGITS}. The advantages of using
 * {@link MetaPattern} over straight Java regular expressions are that the patterns are easier to
 * construct and easier to combine into complex patterns. They are also more readable and more
 * reusable. See {@link MetaPattern} for details.
 * <p>
 * The error message will be generated with the key "PatternValidator" and one additional message
 * key ${pattern} for the pattern which failed to match. See {@link FormComponent} for a list of
 * further messages keys.
 * 
 * @see java.util.regex.Pattern
 * 
 * @author Jonathan Locke
 * @author Igor Vaynberg (ivaynberg)
 * @since 1.2.6
 */
public class PatternValidator implements IValidator<String>
{
        private static final long serialVersionUID = 1L;

        /** the pattern to match */
        private final Pattern pattern;

        /** whether to exclude matching input **/
        private boolean reverse = false;

        /**
         * Constructor that accepts a <code>String</code> regular expression pattern.
         * 
         * @param pattern
         *            a regular expression pattern
         */
        public PatternValidator(final String pattern)
        {
                this(Pattern.compile(pattern));
        }

        /**
         * Constructor that accepts a <code>String</code> pattern and Java <code>regex</code> compile
         * flags as arguments.
         * 
         * @param pattern
         *            a regular expression pattern
         * @param flags
         *            compile flags for <code>java.util.regex.Pattern</code>
         */
        public PatternValidator(final String pattern, final int flags)
        {
                this(Pattern.compile(pattern, flags));
        }

        /**
         * Constructor that accepts a compiled pattern.
         * 
         * @param pattern
         *            a compiled pattern
         */
        public PatternValidator(final Pattern pattern)
        {
                this.pattern = pattern;
        }

        /**
         * Constructor that accepts a <code>MetaPattern</code> argument.
         * 
         * @param pattern
         *            a <code>MetaPattern</code>
         */
        public PatternValidator(final MetaPattern pattern)
        {
                this(pattern.pattern());
        }

        /**
         * Gets the regexp pattern.
         * 
         * @return the regexp pattern
         */
        public final Pattern getPattern()
        {
                return pattern;
        }

        /**
         * If set to true then input that matches the pattern is considered invalid.
         * 
         * @param reverse
         * @return itself
         */
        public PatternValidator setReverse(boolean reverse)
        {
                this.reverse = reverse;
                return this;
        }

        /**
         * @see java.lang.Object#toString()
         */
        @Override
        public String toString()
        {
                return "[PatternValidator pattern = " + pattern + "]";
        }

        /**
         * Checks a value against this <code>PatternValidator</code>'s {@link Pattern}.
         * 
         * @param validatable
         *            the <code>IValidatable</code> to check
         */
        @Override
        public void validate(IValidatable<String> validatable)
        {
                // Check value against pattern
                if (pattern.matcher(validatable.getValue()).matches() == reverse)
                {
                        ValidationError error = new ValidationError(this);
                        error.setVariable("pattern", pattern.pattern());
                        validatable.error(decorate(error, validatable));
                }
        }

        /**
         * Allows subclasses to decorate reported errors
         * 
         * @param error
         * @param validatable
         * @return decorated error
         */
        protected IValidationError decorate(IValidationError error, IValidatable<String> validatable)
        {
                return error;
        }
}