/*

 * 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 info.bliki.commons.validator.routines;





import java.io.Serializable;

import java.util.regex.Matcher;

import java.util.regex.Pattern;



/**

 * <p>Perform email validations.</p>

 * <p>

 * This class is a Singleton; you can retrieve the instance via the getInstance() method.

 * </p>

 * <p>

 * Based on a script by <a href="mailto:stamhankar@hotmail.com">Sandeep V. Tamhankar</a>

 * http://javascript.internet.com

 * </p>

 * <p>

 * This implementation is not guaranteed to catch all possible errors in an email address.

 * For example, an address like nobody@noplace.somedog will pass validator, even though there

 * is no TLD "somedog"

 * </p>.

 *

 * @version $Revision$ $Date$

 * @since Validator 1.4

 */

public class EmailValidator implements Serializable {



    /**

	 * Auto-generated serial version UID.

	 */

	private static final long serialVersionUID = 3799186064442277754L;

	private static final String SPECIAL_CHARS = "\\p{Cntrl}\\(\\)<>@,;:'\\\\\\\"\\.\\[\\]";

    private static final String VALID_CHARS = "[^\\s" + SPECIAL_CHARS + "]";

    private static final String QUOTED_USER = "(\"[^\"]*\")";

    private static final String WORD = "((" + VALID_CHARS + "|')+|" + QUOTED_USER + ")";



    private static final String LEGAL_ASCII_REGEX = "^\\p{ASCII}+$";

    private static final String EMAIL_REGEX = "^\\s*?(.+)@(.+?)\\s*$";

    private static final String IP_DOMAIN_REGEX = "^\\[(.*)\\]$";

    private static final String USER_REGEX = "^\\s*" + WORD + "(\\." + WORD + ")*$";



    private static final Pattern MATCH_ASCII_PATTERN = Pattern.compile(LEGAL_ASCII_REGEX);

    private static final Pattern EMAIL_PATTERN = Pattern.compile(EMAIL_REGEX);

    private static final Pattern IP_DOMAIN_PATTERN = Pattern.compile(IP_DOMAIN_REGEX);

    private static final Pattern USER_PATTERN = Pattern.compile(USER_REGEX);



    /**

     * Singleton instance of this class.

     */

    private static final EmailValidator EMAIL_VALIDATOR = new EmailValidator();



    /**

     * Returns the Singleton instance of this validator.

     *

     * @return singleton instance of this validator.

     */

    public static EmailValidator getInstance() {

        return EMAIL_VALIDATOR;

    }



    /**                                       

     * Protected constructor for subclasses to use.

     */

    protected EmailValidator() {

        super();

    }



    /**

     * <p>Checks if a field has a valid e-mail address.</p>

     *

     * @param email The value validation is being performed on.  A <code>null</code>

     *              value is considered invalid.

     * @return true if the email address is valid.

     */

    public boolean isValid(String email) {

        if (email == null) {

            return false;

        }



        Matcher asciiMatcher = MATCH_ASCII_PATTERN.matcher(email);

        if (!asciiMatcher.matches()) {

            return false;

        }



        // Check the whole email address structure

        Matcher emailMatcher = EMAIL_PATTERN.matcher(email);

        if (!emailMatcher.matches()) {

            return false;

        }



        if (email.endsWith(".")) {

            return false;

        }



        if (!isValidUser(emailMatcher.group(1))) {

            return false;

        }



        return isValidDomain(emailMatcher.group(2));

    }



    /**

     * Returns true if the domain component of an email address is valid.

     *

     * @param domain being validated.

     * @return true if the email address's domain is valid.

     */

    protected boolean isValidDomain(String domain) {

        // see if domain is an IP address in brackets

        Matcher ipDomainMatcher = IP_DOMAIN_PATTERN.matcher(domain);



        if (ipDomainMatcher.matches()) {

            InetAddressValidator inetAddressValidator =

                    InetAddressValidator.getInstance();

            return inetAddressValidator.isValid(ipDomainMatcher.group(1));

        } else {

            // Domain is symbolic name

            DomainValidator domainValidator =

                    DomainValidator.getInstance();

            return domainValidator.isValid(domain);

        }

    }



    /**

     * Returns true if the user component of an email address is valid.

     *

     * @param user being validated

     * @return true if the user name is valid.

     */

    protected boolean isValidUser(String user) {

        return USER_PATTERN.matcher(user).matches();

    }



}