/*

  * 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.commons.codec.net;

 import java.io.UnsupportedEncodingException;

 import java.nio.charset.Charset;

 import java.util.BitSet;

 import org.apache.commons.codec.Charsets;

 import org.apache.commons.codec.DecoderException;

 import org.apache.commons.codec.EncoderException;

 import org.apache.commons.codec.StringDecoder;

 import org.apache.commons.codec.StringEncoder;

 /**

  * Similar to the Quoted-Printable content-transfer-encoding defined in

  * <a href="http://www.ietf.org/rfc/rfc1521.txt">RFC 1521</a> and designed to allow text containing mostly ASCII

  * characters to be decipherable on an ASCII terminal without decoding.

  * <p>

  * <a href="http://www.ietf.org/rfc/rfc1522.txt">RFC 1522</a> describes techniques to allow the encoding of non-ASCII

  * text in various portions of a RFC 822 [2] message header, in a manner which is unlikely to confuse existing message

  * handling software.

  * <p>

  * This class is conditionally thread-safe.

  * The instance field {@link #encodeBlanks} is mutable {@link #setEncodeBlanks(boolean)}

  * but is not volatile, and accesses are not synchronised.

  * If an instance of the class is shared between threads, the caller needs to ensure that suitable synchronisation

  * is used to ensure safe publication of the value between threads, and must not invoke

  * {@link #setEncodeBlanks(boolean)} after initial setup.

  *

  * @see <a href="http://www.ietf.org/rfc/rfc1522.txt">MIME (Multipurpose Internet Mail Extensions) Part Two: Message

  *          Header Extensions for Non-ASCII Text</a>

  *

  * @since 1.3

  * @version $Id$

  */

 public class QCodec extends RFC1522Codec implements StringEncoder, StringDecoder {

     /**

      * The default charset used for string decoding and encoding.

      */

     private final Charset charset;

     /**

      * BitSet of printable characters as defined in RFC 1522.

      */

     private static final BitSet PRINTABLE_CHARS = new BitSet(256);

     // Static initializer for printable chars collection

     static {

         // alpha characters

         PRINTABLE_CHARS.set(' ');

         PRINTABLE_CHARS.set('!');

         PRINTABLE_CHARS.set('"');

         PRINTABLE_CHARS.set('#');

         PRINTABLE_CHARS.set('$');

         PRINTABLE_CHARS.set('%');

         PRINTABLE_CHARS.set('&');

         PRINTABLE_CHARS.set('\'');

         PRINTABLE_CHARS.set('(');

         PRINTABLE_CHARS.set(')');

         PRINTABLE_CHARS.set('*');

         PRINTABLE_CHARS.set('+');

         PRINTABLE_CHARS.set(',');

         PRINTABLE_CHARS.set('-');

         PRINTABLE_CHARS.set('.');

         PRINTABLE_CHARS.set('/');

         for (int i = '0'; i <= '9'; i++) {

             PRINTABLE_CHARS.set(i);

         }

         PRINTABLE_CHARS.set(':');

         PRINTABLE_CHARS.set(';');

         PRINTABLE_CHARS.set('<');

         PRINTABLE_CHARS.set('>');

         PRINTABLE_CHARS.set('@');

         for (int i = 'A'; i <= 'Z'; i++) {

             PRINTABLE_CHARS.set(i);

         }

         PRINTABLE_CHARS.set('[');

         PRINTABLE_CHARS.set('\\');

         PRINTABLE_CHARS.set(']');

         PRINTABLE_CHARS.set('^');

         PRINTABLE_CHARS.set('`');

         for (int i = 'a'; i <= 'z'; i++) {

             PRINTABLE_CHARS.set(i);

         }

         PRINTABLE_CHARS.set('{');

         PRINTABLE_CHARS.set('|');

         PRINTABLE_CHARS.set('}');

         PRINTABLE_CHARS.set('~');

     }

     private static final byte BLANK = 32;

     private static final byte UNDERSCORE = 95;

     private boolean encodeBlanks = false;

     /**

      * Default constructor.

      */

     public QCodec() {

         this(Charsets.UTF_8);

     }

     /**

      * Constructor which allows for the selection of a default charset.

      *

      * @param charset

      *            the default string charset to use.

      *

      * @see <a href="http://download.oracle.com/javase/6/docs/api/java/nio/charset/Charset.html">Standard charsets</a>

      * @since 1.7

      */

     public QCodec(final Charset charset) {

         super();

         this.charset = charset;

     }

     /**

      * Constructor which allows for the selection of a default charset.

      *

      * @param charsetName

      *            the charset to use.

      * @throws java.nio.charset.UnsupportedCharsetException

      *             If the named charset is unavailable

      * @since 1.7 throws UnsupportedCharsetException if the named charset is unavailable

      * @see <a href="http://download.oracle.com/javase/6/docs/api/java/nio/charset/Charset.html">Standard charsets</a>

      */

     public QCodec(final String charsetName) {

         this(Charset.forName(charsetName));

     }

     @Override

     protected String getEncoding() {

         return "Q";

     }

     @Override

     protected byte[] doEncoding(final byte[] bytes) {

         if (bytes == null) {

             return null;

         }

         final byte[] data = QuotedPrintableCodec.encodeQuotedPrintable(PRINTABLE_CHARS, bytes);

         if (this.encodeBlanks) {

             for (int i = 0; i < data.length; i++) {

                 if (data[i] == BLANK) {

                     data[i] = UNDERSCORE;

                 }

             }

         }

         return data;

     }

     @Override

     protected byte[] doDecoding(final byte[] bytes) throws DecoderException {

         if (bytes == null) {

             return null;

         }

         boolean hasUnderscores = false;

         for (final byte b : bytes) {

             if (b == UNDERSCORE) {

                 hasUnderscores = true;

                 break;

             }

         }

         if (hasUnderscores) {

             final byte[] tmp = new byte[bytes.length];

             for (int i = 0; i < bytes.length; i++) {

                 final byte b = bytes[i];

                 if (b != UNDERSCORE) {

                     tmp[i] = b;

                 } else {

                     tmp[i] = BLANK;

                 }

             }

             return QuotedPrintableCodec.decodeQuotedPrintable(tmp);

         }

         return QuotedPrintableCodec.decodeQuotedPrintable(bytes);

     }

     /**

      * Encodes a string into its quoted-printable form using the specified charset. Unsafe characters are escaped.

      *

      * @param str

      *            string to convert to quoted-printable form

      * @param charset

      *            the charset for str

      * @return quoted-printable string

      * @throws EncoderException

      *             thrown if a failure condition is encountered during the encoding process.

      * @since 1.7

      */

     public String encode(final String str, final Charset charset) throws EncoderException {

         if (str == null) {

             return null;

         }

         return encodeText(str, charset);

     }

     /**

      * Encodes a string into its quoted-printable form using the specified charset. Unsafe characters are escaped.

      *

      * @param str

      *            string to convert to quoted-printable form

      * @param charset

      *            the charset for str

      * @return quoted-printable string

      * @throws EncoderException

      *             thrown if a failure condition is encountered during the encoding process.

      */

     public String encode(final String str, final String charset) throws EncoderException {

         if (str == null) {

             return null;

         }

         try {

             return encodeText(str, charset);

         } catch (final UnsupportedEncodingException e) {

             throw new EncoderException(e.getMessage(), e);

         }

     }

     /**

      * Encodes a string into its quoted-printable form using the default charset. Unsafe characters are escaped.

      *

      * @param str

      *            string to convert to quoted-printable form

      * @return quoted-printable string

      * @throws EncoderException

      *             thrown if a failure condition is encountered during the encoding process.

      */

     @Override

     public String encode(final String str) throws EncoderException {

         if (str == null) {

             return null;

         }

         return encode(str, getCharset());

     }

     /**

      * Decodes a quoted-printable string into its original form. Escaped characters are converted back to their original

      * representation.

      *

      * @param str

      *            quoted-printable string to convert into its original form

      * @return original string

      * @throws DecoderException

      *             A decoder exception is thrown if a failure condition is encountered during the decode process.

      */

     @Override

     public String decode(final String str) throws DecoderException {

         if (str == null) {

             return null;

         }

         try {

             return decodeText(str);

         } catch (final UnsupportedEncodingException e) {

             throw new DecoderException(e.getMessage(), e);

         }

     }

     /**

      * Encodes an object into its quoted-printable form using the default charset. Unsafe characters are escaped.

      *

      * @param obj

      *            object to convert to quoted-printable form

      * @return quoted-printable object

      * @throws EncoderException

      *             thrown if a failure condition is encountered during the encoding process.

      */

     @Override

     public Object encode(final Object obj) throws EncoderException {

         if (obj == null) {

             return null;

         } else if (obj instanceof String) {

             return encode((String) obj);

         } else {

             throw new EncoderException("Objects of type " +

                   obj.getClass().getName() +

                   " cannot be encoded using Q codec");

         }

     }

     /**

      * Decodes a quoted-printable object into its original form. Escaped characters are converted back to their original

      * representation.

      *

      * @param obj

      *            quoted-printable object to convert into its original form

      * @return original object

      * @throws DecoderException

      *             Thrown if the argument is not a <code>String</code>. Thrown if a failure condition is encountered

      *             during the decode process.

      */

     @Override

     public Object decode(final Object obj) throws DecoderException {

         if (obj == null) {

             return null;

         } else if (obj instanceof String) {

             return decode((String) obj);

         } else {

             throw new DecoderException("Objects of type " +

                   obj.getClass().getName() +

                   " cannot be decoded using Q codec");

         }

     }

     /**

      * Gets the default charset name used for string decoding and encoding.

      *

      * @return the default charset name

      * @since 1.7

      */

     public Charset getCharset() {

         return this.charset;

     }

     /**

      * Gets the default charset name used for string decoding and encoding.

      *

      * @return the default charset name

      */

     public String getDefaultCharset() {

         return this.charset.name();

     }

     /**

      * Tests if optional transformation of SPACE characters is to be used

      *

      * @return {@code true} if SPACE characters are to be transformed, {@code false} otherwise

      */

     public boolean isEncodeBlanks() {

         return this.encodeBlanks;

     }

     /**

      * Defines whether optional transformation of SPACE characters is to be used

      *

      * @param b

      *            {@code true} if SPACE characters are to be transformed, {@code false} otherwise

      */

     public void setEncodeBlanks(final boolean b) {

         this.encodeBlanks = b;

     }

 }