/*
    * 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
    *
    *      https://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.ByteArrayOutputStream;
  import java.io.UnsupportedEncodingException;
  import java.nio.charset.Charset;
  import java.nio.charset.IllegalCharsetNameException;
  import java.nio.charset.StandardCharsets;
  import java.nio.charset.UnsupportedCharsetException;
  import java.util.BitSet;
  
  import org.apache.commons.codec.BinaryDecoder;
  import org.apache.commons.codec.BinaryEncoder;
  import org.apache.commons.codec.DecoderException;
  import org.apache.commons.codec.EncoderException;
  import org.apache.commons.codec.StringDecoder;
  import org.apache.commons.codec.StringEncoder;
  import org.apache.commons.codec.binary.StringUtils;
  
  /**
   * Codec for the Quoted-Printable section of <a href="https://www.ietf.org/rfc/rfc1521.txt">RFC 1521</a>.
   * <p>
   * The Quoted-Printable encoding is intended to represent data that largely consists of octets that correspond to printable characters in the ASCII character
   * set. It encodes the data in such a way that the resulting octets are unlikely to be modified by mail transport. If the data being encoded are mostly ASCII
   * text, the encoded form of the data remains largely recognizable by humans. A body which is entirely ASCII may also be encoded in Quoted-Printable to ensure
   * the integrity of the data should the message pass through a character- translating, and/or line-wrapping gateway.
   * </p>
   * <p>
   * Note:
   * </p>
   * <p>
   * Depending on the selected {@code strict} parameter, encoding implements a different set of rules of the quoted-printable spec:
   * </p>
   * <ul>
   * <li>{@code strict=false}: only rules #1 and #2 are implemented</li>
   * <li>{@code strict=true}: all rules #1 through #5 are implemented</li>
   * </ul>
   * <p>
   * Originally, this class only supported the non-strict mode, but the codec in this partial form could already be used for certain applications that do not
   * require quoted-printable line formatting (rules #3, #4, #5), for instance Q codec. The strict mode has been added in 1.10.
   * Decoding is independent of this parameter; see {@link #decodeQuotedPrintable(byte[])} for its behavior.
   * </p>
   * <p>
   * This class is immutable and thread-safe.
   * </p>
   *
   * @see <a href="https://www.ietf.org/rfc/rfc1521.txt">RFC 1521 MIME (Multipurpose Internet Mail Extensions) Part One: Mechanisms for Specifying and Describing
   *      the Format of Internet Message Bodies </a>
   *
   * @since 1.3
   */
  public class QuotedPrintableCodec implements BinaryEncoder, BinaryDecoder, StringEncoder, StringDecoder {
  
      /**
       * BitSet of printable characters as defined in RFC 1521.
       */
      private static final BitSet PRINTABLE_CHARS = new BitSet(256);
      private static final byte ESCAPE_CHAR = '=';
      private static final byte TAB = 9;
      private static final byte CR = 13;
      private static final byte LF = 10;
  
      /**
       * Minimum length required for the byte arrays used by encodeQuotedPrintable method.
       */
      private static final int MIN_BYTES = 3;
  
      /**
       * Safe line length for quoted printable encoded text.
       */
      private static final int SAFE_LENGTH = 73;
  
      // Static initializer for printable chars collection
      static {
          // alpha characters
          for (int i = 33; i <= 60; i++) {
              PRINTABLE_CHARS.set(i);
          }
          for (int i = 62; i <= 126; i++) {
              PRINTABLE_CHARS.set(i);
          }
          PRINTABLE_CHARS.set(TAB);
          PRINTABLE_CHARS.set(Utils.SPACE);
     }
 
     /**
      * Decodes quoted-printable bytes.
      *
      * <p>
      * Converts hexadecimal escapes to their original bytes, removes soft line breaks ({@code =CRLF}), and preserves hard CRLF line breaks.
      * </p>
      *
      * <p>
      * As a lenient extension for malformed input, unpaired CR and LF bytes are also preserved. An equals sign followed by CR without LF is rejected.
      * This method does not perform full MIME validation: for example, it neither removes trailing whitespace nor handles transport padding after an
      * equals sign. The {@code strict} constructor parameter affects encoding only.
      * </p>
      *
      * <p>
      * Since 1.23.0, unescaped CR and LF bytes are preserved and {@code =CR} without a following LF is rejected. Earlier versions discarded unescaped
      * CR and LF bytes and accepted {@code =CR} as a soft line break.
      * </p>
      *
      * @param bytes array of quoted-printable characters.
      * @return array of original bytes, or {@code null} if the input is {@code null}.
      * @throws DecoderException Thrown if an escape is incomplete or invalid, including a soft line break without the full CRLF pair.
      */
     public static final byte[] decodeQuotedPrintable(final byte[] bytes) throws DecoderException {
         if (bytes == null) {
             return null;
         }
         final ByteArrayOutputStream buffer = new ByteArrayOutputStream();
         for (int i = 0; i < bytes.length; i++) {
             final int b = bytes[i];
             if (b == ESCAPE_CHAR) {
                 try {
                     // rule #5: a soft line break is the escape character followed by a CRLF sequence;
                     // it is removed entirely from the decoded output
                     if (bytes[++i] == CR) {
                         if (++i >= bytes.length || bytes[i] != LF) {
                             throw new DecoderException("Invalid quoted-printable encoding: soft line break must be =CRLF");
                         }
                         continue;
                     }
                     final int u = Utils.digit16(bytes[i]);
                     final int l = Utils.digit16(bytes[++i]);
                     buffer.write((char) ((u << 4) + l));
                 } catch (final ArrayIndexOutOfBoundsException e) {
                     throw new DecoderException("Invalid quoted-printable encoding", e);
                 }
             } else {
                 // Preserve hard line breaks and, leniently, unpaired CR and LF bytes.
                 buffer.write(b);
             }
         }
         return buffer.toByteArray();
     }
 
     /**
      * Encodes a byte in the buffer.
      *
      * @param b      byte to write.
      * @param encode indicates whether the octet shall be encoded.
      * @param buffer The buffer to write to.
      * @return The number of bytes that have been written to the buffer.
      */
     private static int encodeByte(final int b, final boolean encode, final ByteArrayOutputStream buffer) {
         if (encode) {
             return encodeQuotedPrintable(b, buffer);
         }
         buffer.write(b);
         return 1;
     }
 
     /**
      * Encodes an array of bytes into an array of quoted-printable 7-bit characters. Unsafe characters are escaped.
      * <p>
      * This function implements a subset of quoted-printable encoding specification (rule #1 and rule #2) as defined in RFC 1521 and is suitable for encoding
      * binary data and unformatted text.
      * </p>
      *
      * @param printable bitset of characters deemed quoted-printable.
      * @param bytes     array of bytes to be encoded.
      * @return array of bytes containing quoted-printable data.
      */
     public static final byte[] encodeQuotedPrintable(final BitSet printable, final byte[] bytes) {
         return encodeQuotedPrintable(printable, bytes, false);
     }
 
     /**
      * Encodes an array of bytes into an array of quoted-printable 7-bit characters. Unsafe characters are escaped.
      * <p>
      * Depending on the selection of the {@code strict} parameter, this function either implements the full ruleset or only a subset of quoted-printable
      * encoding specification (rule #1 and rule #2) as defined in RFC 1521 and is suitable for encoding binary data and unformatted text.
      * </p>
      *
      * @param printable bitset of characters deemed quoted-printable.
      * @param bytes     array of bytes to be encoded.
      * @param strict    if {@code true} the full ruleset is used, otherwise only rule #1 and rule #2.
      * @return array of bytes containing quoted-printable data.
      * @since 1.10
      */
     public static final byte[] encodeQuotedPrintable(BitSet printable, final byte[] bytes, final boolean strict) {
         if (bytes == null) {
             return null;
         }
         if (printable == null) {
             printable = PRINTABLE_CHARS;
         }
         final ByteArrayOutputStream buffer = new ByteArrayOutputStream();
         final int bytesLength = bytes.length;
         if (strict) {
             if (bytesLength < MIN_BYTES) {
                 return null;
             }
             int pos = 1;
             // encode up to buffer.length - 3, the last three octets will be treated
             // separately for simplification of note #3
             for (int i = 0; i < bytesLength - 3; i++) {
                 final int b = getUnsignedOctet(i, bytes);
                 if (pos < SAFE_LENGTH) {
                     // up to this length it is safe to add any byte, encoded or not
                     pos += encodeByte(b, !printable.get(b), buffer);
                 } else {
                     // rule #3: whitespace at the end of a line *must* be encoded
                     encodeByte(b, !printable.get(b) || isWhitespace(b), buffer);
                     // rule #5: soft line break
                     buffer.write(ESCAPE_CHAR);
                     buffer.write(CR);
                     buffer.write(LF);
                     pos = 1;
                 }
             }
             // rule #3: whitespace at the end of a line *must* be encoded
             // if we would do a soft break line after this octet, encode whitespace
             int b = getUnsignedOctet(bytesLength - 3, bytes);
             boolean encode = !printable.get(b) || isWhitespace(b) && pos > SAFE_LENGTH - 5;
             pos += encodeByte(b, encode, buffer);
             // note #3: '=' *must not* be the ultimate or penultimate character
             // simplification: if < 6 bytes left, do a soft line break as we may need
             // exactly 6 bytes space for the last 2 bytes
             if (pos > SAFE_LENGTH - 2) {
                 buffer.write(ESCAPE_CHAR);
                 buffer.write(CR);
                 buffer.write(LF);
             }
             for (int i = bytesLength - 2; i < bytesLength; i++) {
                 b = getUnsignedOctet(i, bytes);
                 // rule #3: trailing whitespace shall be encoded
                 encode = !printable.get(b) || i > bytesLength - 2 && isWhitespace(b);
                 encodeByte(b, encode, buffer);
             }
         } else {
             for (final byte c : bytes) {
                 int b = c;
                 if (b < 0) {
                     b = 256 + b;
                 }
                 if (printable.get(b)) {
                     buffer.write(b);
                 } else {
                     encodeQuotedPrintable(b, buffer);
                 }
             }
         }
         return buffer.toByteArray();
     }
 
     /**
      * Encodes byte into its quoted-printable representation.
      *
      * @param b      byte to encode.
      * @param buffer The buffer to write to.
      * @return The number of bytes written to the {@code buffer}.
      */
     private static int encodeQuotedPrintable(final int b, final ByteArrayOutputStream buffer) {
         buffer.write(ESCAPE_CHAR);
         final char hex1 = Utils.hexChar(b >> 4);
         final char hex2 = Utils.hexChar(b);
         buffer.write(hex1);
         buffer.write(hex2);
         return 3;
     }
 
     /**
      * Gets the byte at position {@code index} of the byte array and makes sure it is unsigned.
      *
      * @param index position in the array.
      * @param bytes The byte array.
      * @return The unsigned octet at position {@code index} from the array.
      */
     private static int getUnsignedOctet(final int index, final byte[] bytes) {
         int b = bytes[index];
         if (b < 0) {
             b = 256 + b;
         }
         return b;
     }
 
     /**
      * Tests whether the given byte is whitespace.
      *
      * @param b byte to be checked.
      * @return {@code true} if the byte is either a space or tab character.
      */
     private static boolean isWhitespace(final int b) {
         return b == Utils.SPACE || b == TAB;
     }
 
     /**
      * The default Charset used for string decoding and encoding.
      */
     private final Charset charset;
 
     /**
      * Indicates whether soft line breaks shall be used during encoding (rule #3-5).
      */
     private final boolean strict;
 
     /**
      * Constructs a new instance, assumes default Charset of {@link StandardCharsets#UTF_8}
      */
     public QuotedPrintableCodec() {
         this(StandardCharsets.UTF_8, false);
     }
 
     /**
      * Constructs a new instance for the selection of the strict mode.
      *
      * @param strict if {@code true}, soft line breaks will be used.
      * @since 1.10
      */
     public QuotedPrintableCodec(final boolean strict) {
         this(StandardCharsets.UTF_8, strict);
     }
 
     /**
      * Constructs a new instance for the selection of a default Charset.
      *
      * @param charset The default string Charset to use.
      * @since 1.7
      */
     public QuotedPrintableCodec(final Charset charset) {
         this(charset, false);
     }
 
     /**
      * Constructs a new instance for the selection of a default Charset and strict mode.
      *
      * @param charset The default string Charset to use.
      * @param strict  if {@code true}, soft line breaks will be used.
      * @since 1.10
      */
     public QuotedPrintableCodec(final Charset charset, final boolean strict) {
         this.charset = charset;
         this.strict = strict;
     }
 
     /**
      * Constructs a new instance for the selection of a default Charset.
      *
      * @param charsetName The default string Charset to use.
      * @throws UnsupportedCharsetException Thrown if no support for the named Charset is available in this instance of the Java virtual machine.
      * @throws IllegalArgumentException    Thrown if the given charsetName is null.
      * @throws IllegalCharsetNameException Thrown if the given Charset name is illegal.
      *
      * @since 1.7 throws UnsupportedCharsetException if the named Charset is unavailable
      */
     public QuotedPrintableCodec(final String charsetName) throws IllegalCharsetNameException, IllegalArgumentException, UnsupportedCharsetException {
         this(Charset.forName(charsetName), false);
     }
 
     /**
      * Decodes an array of quoted-printable characters into an array of original bytes. Escaped characters are converted back to their original representation.
      * <p>
      * This function fully implements the quoted-printable encoding specification (rule #1 through rule #5) as defined in RFC 1521.
      * </p>
      *
      * @param bytes array of quoted-printable characters.
      * @return array of original bytes.
      * @throws DecoderException Thrown if quoted-printable decoding is unsuccessful.
      */
     @Override
     public byte[] decode(final byte[] bytes) throws DecoderException {
         return decodeQuotedPrintable(bytes);
     }
 
     /**
      * 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} or {@code byte[]}. 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;
         }
         if (obj instanceof byte[]) {
             return decode((byte[]) obj);
         }
         if (obj instanceof String) {
             return decode((String) obj);
         }
         throw new DecoderException("Objects of type " + obj.getClass().getName() + " cannot be quoted-printable decoded");
     }
 
     /**
      * Decodes a quoted-printable string into its original form using the default string Charset. Escaped characters are converted back to their original
      * representation.
      *
      * @param sourceStr quoted-printable string to convert into its original form.
      * @return original string.
      * @throws DecoderException Thrown if quoted-printable decoding is unsuccessful. Thrown if Charset is not supported.
      * @see #getCharset()
      */
     @Override
     public String decode(final String sourceStr) throws DecoderException {
         return this.decode(sourceStr, getCharset());
     }
 
     /**
      * Decodes a quoted-printable string into its original form using the specified string Charset. Escaped characters are converted back to their original
      * representation.
      *
      * @param sourceStr     quoted-printable string to convert into its original form.
      * @param sourceCharset The original string Charset.
      * @return original string.
      * @throws DecoderException Thrown if quoted-printable decoding is unsuccessful.
      * @since 1.7
      */
     public String decode(final String sourceStr, final Charset sourceCharset) throws DecoderException {
         if (sourceStr == null) {
             return null;
         }
         return new String(this.decode(StringUtils.getBytesUsAscii(sourceStr)), sourceCharset);
     }
 
     /**
      * Decodes a quoted-printable string into its original form using the specified string Charset. Escaped characters are converted back to their original
      * representation.
      *
      * @param sourceStr     quoted-printable string to convert into its original form.
      * @param sourceCharset The original string Charset.
      * @return original string.
      * @throws DecoderException             Thrown if quoted-printable decoding is unsuccessful.
      * @throws UnsupportedEncodingException Thrown if Charset is not supported.
      */
     public String decode(final String sourceStr, final String sourceCharset) throws DecoderException, UnsupportedEncodingException {
         if (sourceStr == null) {
             return null;
         }
         return new String(decode(StringUtils.getBytesUsAscii(sourceStr)), sourceCharset);
     }
 
     /**
      * Encodes an array of bytes into an array of quoted-printable 7-bit characters. Unsafe characters are escaped.
      * <p>
      * Depending on the selection of the {@code strict} parameter, this function either implements the full ruleset or only a subset of quoted-printable
      * encoding specification (rule #1 and rule #2) as defined in RFC 1521 and is suitable for encoding binary data and unformatted text.
      * </p>
      *
      * @param bytes array of bytes to be encoded.
      * @return array of bytes containing quoted-printable data.
      */
     @Override
     public byte[] encode(final byte[] bytes) {
         return encodeQuotedPrintable(PRINTABLE_CHARS, bytes, strict);
     }
 
     /**
      * Encodes an object into its quoted-printable safe form. Unsafe characters are escaped.
      *
      * @param obj string to convert to a quoted-printable form.
      * @return quoted-printable object.
      * @throws EncoderException Thrown if quoted-printable encoding is not applicable to objects of this type or if encoding is unsuccessful.
      */
     @Override
     public Object encode(final Object obj) throws EncoderException {
         if (obj == null) {
             return null;
         }
         if (obj instanceof byte[]) {
             return encode((byte[]) obj);
         }
         if (obj instanceof String) {
             return encode((String) obj);
         }
         throw new EncoderException("Objects of type " + obj.getClass().getName() + " cannot be quoted-printable encoded");
     }
 
     /**
      * Encodes a string into its quoted-printable form using the default string Charset. Unsafe characters are escaped.
      * <p>
      * Depending on the selection of the {@code strict} parameter, this function either implements the full ruleset or only a subset of quoted-printable
      * encoding specification (rule #1 and rule #2) as defined in RFC 1521 and is suitable for encoding binary data and unformatted text.
      * </p>
      *
      * @param sourceStr string to convert to quoted-printable form.
      * @return quoted-printable string.
      * @throws EncoderException Thrown if quoted-printable encoding is unsuccessful.
      *
      * @see #getCharset()
      */
     @Override
     public String encode(final String sourceStr) throws EncoderException {
         return encode(sourceStr, getCharset());
     }
 
     /**
      * Encodes a string into its quoted-printable form using the specified Charset. Unsafe characters are escaped.
      * <p>
      * Depending on the selection of the {@code strict} parameter, this function either implements the full ruleset or only a subset of quoted-printable
      * encoding specification (rule #1 and rule #2) as defined in RFC 1521 and is suitable for encoding binary data and unformatted text.
      * </p>
      *
      * @param sourceStr     string to convert to quoted-printable form.
      * @param sourceCharset The Charset for sourceStr.
      * @return quoted-printable string.
      * @since 1.7
      */
     public String encode(final String sourceStr, final Charset sourceCharset) {
         if (sourceStr == null) {
             return null;
         }
         return StringUtils.newStringUsAscii(this.encode(sourceStr.getBytes(sourceCharset)));
     }
 
     /**
      * Encodes a string into its quoted-printable form using the specified Charset. Unsafe characters are escaped.
      * <p>
      * Depending on the selection of the {@code strict} parameter, this function either implements the full ruleset or only a subset of quoted-printable
      * encoding specification (rule #1 and rule #2) as defined in RFC 1521 and is suitable for encoding binary data and unformatted text.
      * </p>
      *
      * @param sourceStr     string to convert to quoted-printable form.
      * @param sourceCharset The Charset for sourceStr.
      * @return quoted-printable string.
      * @throws UnsupportedEncodingException Thrown if the Charset is not supported.
      */
     public String encode(final String sourceStr, final String sourceCharset) throws UnsupportedEncodingException {
         if (sourceStr == null) {
             return null;
         }
         return StringUtils.newStringUsAscii(encode(sourceStr.getBytes(sourceCharset)));
     }
 
     /**
      * 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();
     }
 }