001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *     http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.commons.mail2.jakarta.util;
018
019import java.net.IDN;
020import java.util.function.Function;
021
022import jakarta.mail.internet.InternetAddress;
023
024/**
025 * Converts email addresses containing International Domain Names into an ASCII representation suitable for sending an email.
026 *
027 * @see <a href="https://docs.oracle.com/javase/tutorial/i18n/network/idn.html">https://docs.oracle.com/javase/tutorial/i18n/network/idn.html</a>
028 * @see <a href="https://en.wikipedia.org/wiki/Punycode">https://en.wikipedia.org/wiki/Punycode</a>
029 * @see <a href="https://tools.ietf.org/html/rfc5891">https://tools.ietf.org/html/rfc5891</a>
030 * @see <a href="https://en.wikipedia.org/wiki/Punycode">https://en.wikipedia.org/wiki/Punycode</a>
031 *
032 * @since 1.5
033 */
034public class IDNEmailAddressConverter {
035
036    /**
037     * Constructs a new instance.
038     */
039    public IDNEmailAddressConverter() {
040        // empty
041    }
042
043    /**
044     * Extracts the domain part of the email address.
045     *
046     * @param email email address.
047     * @param idx   index of '@' character.
048     * @return domain part of email
049     */
050    private String getDomainPart(final String email, final int idx) {
051        return email.substring(idx + 1);
052    }
053
054    /**
055     * Extracts the local part of the email address.
056     *
057     * @param email email address.
058     * @param idx   index of '@' character.
059     * @return local part of email
060     */
061    private String getLocalPart(final String email, final int idx) {
062        return email.substring(0, idx);
063    }
064
065    /**
066     * Converts an email address to its ASCII representation using "Punycode".
067     *
068     * @param email email address.
069     * @return The ASCII representation
070     */
071    public String toASCII(final String email) {
072        return toString(email, IDN::toASCII);
073    }
074
075    private String toString(final String email, final Function<String, String> converter) {
076        final int idx = email == null ? -1 : email.indexOf('@');
077        if (idx < 0) {
078            return email;
079        }
080        return getLocalPart(email, idx) + '@' + converter.apply(getDomainPart(email, idx));
081    }
082
083    /**
084     * Converts the address part of an InternetAddress to its Unicode representation.
085     *
086     * @param address email address.
087     * @return The Unicode representation
088     */
089    String toUnicode(final InternetAddress address) {
090        return address != null ? toUnicode(address.getAddress()) : null;
091    }
092
093    /**
094     * Converts an "Punycode" email address to its Unicode representation.
095     *
096     * @param email email address.
097     * @return The Unicode representation
098     */
099    String toUnicode(final String email) {
100        return toString(email, IDN::toUnicode);
101    }
102}