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/****************************************************************
 * 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   *
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 *                                                              *
 * 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.                                           *
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package org.apache.james.imap.api.display;

import java.nio.ByteBuffer;
import java.nio.charset.Charset;

import com.beetstra.jutf7.CharsetProvider;
import com.google.common.base.CharMatcher;

/**
 * This class has some methods included which helps to encode/decode modified UTF7
 */
public class ModifiedUtf7 {
    private static final CharMatcher UNENCODED_CHAR_MATCHER = CharMatcher.isNot('&');

    private static final Charset X_MODIFIED_UTF_7_CHARSET = new CharsetProvider().charsetForName("X-MODIFIED-UTF-7");

    /**
     * Decode the given UTF7 encoded String
     * 
     * @param input utf7-encoded value
     * @return decoded value
     */
    public static String decodeModifiedUTF7(String input) {
        if (UNENCODED_CHAR_MATCHER.matchesAllOf(input)) {
            return input;
        }
        return X_MODIFIED_UTF_7_CHARSET.decode(ByteBuffer.wrap(input.getBytes())).toString();
    }

    /**
     * Encode the given String to modified UTF7. 
     * See RFC3501 for more details
     * 
     * @param input
     * @return utf7-encoded value
     */
    public static String encodeModifiedUTF7(String input) {
        ByteBuffer encode = X_MODIFIED_UTF_7_CHARSET.encode(input);
        return new String(encode.array(), 0, encode.remaining());
    }
}