/*

  * 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.myfaces.shared.renderkit.html.util;

 import java.io.ByteArrayOutputStream;

 import java.io.IOException;

 import java.io.OutputStreamWriter;

 import java.io.Writer;

 /**

  * Converts Strings so that they can be used within HTML-Code.

  */

 public abstract class HTMLEncoder

 {

     /**

      * Variant of {@link #encode} where encodeNewline is false and encodeNbsp is true.

      */

     public static String encode (String string)

     {

         return encode(string, false, true);

     }

     /**

      * Variant of {@link #encode} where encodeNbsp is true.

      */

     public static String encode (String string, boolean encodeNewline)

     {

         return encode(string, encodeNewline, true);

     }

     /**

      * Variant of {@link #encode} where encodeNbsp and encodeNonLatin are true 

      */

     public static String encode (String string, boolean encodeNewline, boolean encodeSubsequentBlanksToNbsp)

     {

         return encode(string, encodeNewline, encodeSubsequentBlanksToNbsp, true);

     }

     /**

      * Encodes the given string, so that it can be used within a html page.

      * @param string the string to convert

      * @param encodeNewline if true newline characters are converted to <br>'s

      * @param encodeSubsequentBlanksToNbsp if true subsequent blanks are converted to  's

      * @param encodeNonLatin if true encode non-latin characters as numeric character references

      */

     public static String encode (String string,

                                  boolean encodeNewline,

                                  boolean encodeSubsequentBlanksToNbsp,

                                  boolean encodeNonLatin)

     {

         if (string == null)

         {

             return "";

         }

         StringBuilder sb = null;    //create later on demand

         String app;

         char c = ' ';

         char prevC;

         int length = string.length();

         for (int i = 0; i < length; ++i)

         {

             app = null;

             prevC = c;

             c = string.charAt(i);

             // All characters before letters

             if ((int)c < 0x41)

             {

                 switch (c)

                 {

                     case '"': app = """; break;    //"

                     case '&': app = "&"; break;     //&

                     case '<': app = "&lt;"; break;      //<

                     case '>': app = ">"; break;      //>

                     case ' ':

                         if (encodeSubsequentBlanksToNbsp &&

                                 prevC == ' ')

                         {

                             //Space at beginning or after another space

                             app = " ";

                         }

                         break;

                     case '\n':

                         if (encodeNewline)

                         {

                             app = "<br/>";

                         }

                         break;

                     default:

                         break;

                 }

                 // http://www.w3.org/MarkUp/html3/specialchars.html

                 // From C0 extension U+0000-U+001F only U+0009, U+000A and

                 // U+000D are valid control characters

                 if (c <= 0x1F && c != 0x09 && c != 0x0A && c != 0x0D)

                 {

                     // Ignore escape character

                     app = "";

                 }

             }

             else if (encodeNonLatin && (int)c > 0x80)

             {

                  switch(c)

                  {

                     //german umlauts

                     case '\u00E4' : app = "ä";  break;

                     case '\u00C4' : app = "Ä";  break;

                     case '\u00F6' : app = "ö";  break;

                     case '\u00D6' : app = "Ö";  break;

                     case '\u00FC' : app = "ü";  break;

                     case '\u00DC' : app = "Ü";  break;

                     case '\u00DF' : app = "ß"; break;

                     //misc

                     //case 0x80: app = "€"; break;  sometimes euro symbol is ascii 128, should we suport it?

                     case '\u20AC': app = "€";  break;

                     case '\u00AB': app = "«"; break;

                     case '\u00BB': app = "»"; break;

                     case '\u00A0': app = " "; break;

                     default :

                         //encode all non basic latin characters

                         app = "&#" + ((int)c) + ";";

                     break;

                 }

             }

             if (app != null)

             {

                 if (sb == null)

                 {

                     sb = new StringBuilder(string.substring(0, i));

                 }

                 sb.append(app);

             }

             else

             {

                 if (sb != null)

                 {

                     sb.append(c);

                 }

             }

         }

         if (sb == null)

         {

             return string;

         }

         else

         {

             return sb.toString();

         }

     }

     /**

      * Variant of {@link #encode} where encodeNewline is false and encodeNbsp is true.

      */

     public static void encode (Writer writer, String string) throws IOException

     {

         encode(writer, string, false, true);

     }

     /**

      * Variant of {@link #encode} where encodeNbsp is true.

      */

     public static void encode (Writer writer, String string, boolean encodeNewline) throws IOException

     {

         encode(writer, string, encodeNewline, true);

     }

     /**

      * Variant of {@link #encode} where encodeNbsp and encodeNonLatin are true 

      */

     public static void encode (Writer writer, String string, 

             boolean encodeNewline, boolean encodeSubsequentBlanksToNbsp) throws IOException

     {

         encode(writer, string, encodeNewline, encodeSubsequentBlanksToNbsp, true);

     }

     public static void encode (Writer writer, String string,

                                  boolean encodeNewline,

                                  boolean encodeSubsequentBlanksToNbsp,

                                  boolean encodeNonLatin) throws IOException

     {

         if (string == null)

         {

             return;

         }

         int start = 0;

         String app;

         char c = ' ';

         char prevC;

         int length = string.length();

         for (int i = 0; i < length; ++i)

         {

             app = null;

             prevC = c;

             c = string.charAt(i);

             // All characters before letters

             if ((int)c < 0x41)

             {

                 switch (c)

                 {

                     case '"': app = """; break;    //"

                     case '&': app = "&"; break;     //&

                     case '<': app = "&lt;"; break;      //<

                     case '>': app = ">"; break;      //>

                     case ' ':

                         if (encodeSubsequentBlanksToNbsp &&

                                 prevC == ' ')

                         {

                             //Space at beginning or after another space

                             app = " ";

                         }

                         break;

                     case '\n':

                         if (encodeNewline)

                         {

                             app = "<br/>";

                         }

                         break;

                     default:

                         break;

                 }

                 // http://www.w3.org/MarkUp/html3/specialchars.html

                 // From C0 extension U+0000-U+001F only U+0009, U+000A and

                 // U+000D are valid control characters

                 if (c <= 0x1F && c != 0x09 && c != 0x0A && c != 0x0D)

                 {

                     // Ignore escape character

                     app = "";

                 }

             }

             else if (encodeNonLatin && (int)c > 0x80)

             {

                  switch(c)

                  {

                     //german umlauts

                     case '\u00E4' : app = "ä";  break;

                     case '\u00C4' : app = "Ä";  break;

                     case '\u00F6' : app = "ö";  break;

                     case '\u00D6' : app = "Ö";  break;

                     case '\u00FC' : app = "ü";  break;

                     case '\u00DC' : app = "Ü";  break;

                     case '\u00DF' : app = "ß"; break;

                     //misc

                     //case 0x80: app = "€"; break;  sometimes euro symbol is ascii 128, should we suport it?

                     case '\u20AC': app = "€";  break;

                     case '\u00AB': app = "«"; break;

                     case '\u00BB': app = "»"; break;

                     case '\u00A0': app = " "; break;

                     default :

                         //encode all non basic latin characters

                         app = "&#" + ((int)c) + ";";

                     break;

                 }

             }

             if (app != null)

             {

                 //if (sb == null)

                 //{

                 //    sb = new StringBuilder(string.substring(0, i));

                 //}

                 //sb.append(app);

                 if (start < i)

                 {

                     writer.write(string, start, i-start);

                 }

                 start = i+1;

                 writer.write(app);

             }

             //else

             //{

             //    if (sb != null)

             //    {

             //        sb.append(c);

             //    }

             //}

         }

         //if (sb == null)

         //{

         //    return string;

         //}

         //else

         //{

         //    return sb.toString();

         //}

         if (start == 0)

         {

             writer.write(string);

         }

         else if (start < length)

         {

             writer.write(string,start,length-start);

         }

     }

     /**

      * Variant of {@link #encode} where encodeNewline is false and encodeNbsp is true.

      */

     public static void encode (char[] string, int offset, int length, Writer writer) throws IOException

     {

         encode(string, offset, length, false, true, writer);

     }

     /**

      * Variant of {@link #encode} where encodeNbsp is true.

      */

     public static void encode (char[] string, int offset, int length, boolean encodeNewline, Writer writer)

         throws IOException

     {

         encode(string, offset, length, encodeNewline, true, writer);

     }

     /**

      * Variant of {@link #encode} where encodeNbsp and encodeNonLatin are true 

      */

     public static void encode (char[] string, int offset, int length, boolean encodeNewline, 

             boolean encodeSubsequentBlanksToNbsp, Writer writer) throws IOException

     {

         encode(string, offset, length, encodeNewline, encodeSubsequentBlanksToNbsp, true, writer);

     }

     /**

      * Encodes the given string, so that it can be used within a html page.

      * @param string the string to convert

      * @param encodeNewline if true newline characters are converted to <br>'s

      * @param encodeSubsequentBlanksToNbsp if true subsequent blanks are converted to  's

      * @param encodeNonLatin if true encode non-latin characters as numeric character references

      */

     public static void encode (char[] string, int offset, int length,

                                  boolean encodeNewline,

                                  boolean encodeSubsequentBlanksToNbsp,

                                  boolean encodeNonLatin, Writer writer) throws IOException

     {

         if (string == null || length < 0 || offset >= string.length)

         {

             return;

         }

         offset = Math.max(0, offset);

         int realLength = Math.min(length, string.length - offset);

         //StringBuilder sb = null;    //create later on demand

         String app;

         char c = ' ';

         char prevC;

         int start = offset;

         for (int i = offset; i < offset + realLength; ++i)

         {

             app = null;

             prevC = c;

             c = string[i];

             // All characters before letters

             if ((int)c < 0x41)

             {

                 switch (c)

                 {

                     case '"': app = """; break;    //"

                     case '&': app = "&"; break;     //&

                     case '<': app = "&lt;"; break;      //<

                     case '>': app = ">"; break;      //>

                     case ' ':

                         if (encodeSubsequentBlanksToNbsp &&

                                 prevC == ' ')

                         {

                             //Space at beginning or after another space

                             app = " ";

                         }

                         break;

                     case '\n':

                         if (encodeNewline)

                         {

                             app = "<br/>";

                         }

                         break;

                     default:

                         break;

                 }

                 // http://www.w3.org/MarkUp/html3/specialchars.html

                 // From C0 extension U+0000-U+001F only U+0009, U+000A and

                 // U+000D are valid control characters

                 if (c <= 0x1F && c != 0x09 && c != 0x0A && c != 0x0D)

                 {

                     // Ignore escape character

                     app = "";

                 }

             }

             else if (encodeNonLatin && (int)c > 0x80)

             {

                  switch(c)

                  {

                     //german umlauts

                     case '\u00E4' : app = "ä";  break;

                     case '\u00C4' : app = "Ä";  break;

                     case '\u00F6' : app = "ö";  break;

                     case '\u00D6' : app = "Ö";  break;

                     case '\u00FC' : app = "ü";  break;

                     case '\u00DC' : app = "Ü";  break;

                     case '\u00DF' : app = "ß"; break;

                     //misc

                     //case 0x80: app = "€"; break;  sometimes euro symbol is ascii 128, should we suport it?

                     case '\u20AC': app = "€";  break;

                     case '\u00AB': app = "«"; break;

                     case '\u00BB': app = "»"; break;

                     case '\u00A0': app = " "; break;

                     default :

                         //encode all non basic latin characters

                         app = "&#" + ((int)c) + ";";

                     break;

                 }

             }

             if (app != null)

             {

                 //if (sb == null)

                 //{

                 //    sb = new StringBuilder(realLength*2);

                 //    sb.append(string, offset, i - offset);

                 //}

                 //sb.append(app);

                 if (start < i)

                 {

                     writer.write(string, start, i-start);

                 }

                 start = i+1;

                 writer.write(app);

             }

             /*

             else

             {

                 if (sb != null)

                 {

                     sb.append(c);

                 }

             }*/

         }

         //if (sb == null)

         //{

         //    writer.write(string, offset, realLength);

         //}

         //else

         //{

         //    writer.write(sb.toString());

         //}

         if (start == offset)

         {

             writer.write(string, offset, realLength);

         }

         else if (start < offset+realLength)

         {

             writer.write(string,start,offset+realLength-start);

         }

     }

     private static final String HEX_CHARSET = "0123456789ABCDEF";

     private static final String UTF8 = "UTF-8";

     /**

      * Encode an URI, escaping or percent-encoding all required characters and

      * following the rules mentioned on RFC 3986.  

      * 

      * @param string

      * @param encodeNonLatin

      * @return

      * @throws IOException

      */

     public static String encodeURIAttribute(final String string, final String characterEncoding)

         throws IOException

     {

         StringBuilder sb = null;    //create later on demand

         String app;

         char c;

         boolean endLoop = false;

         int length = string.length();

         for (int i = 0; i < length; ++i)

         {

             app = null;

             c = string.charAt(i);

             // This are the guidelines to be taken into account by this algorithm to encode:

             // RFC 2396 Section 2.4.3 Excluded US-ASCII Characters

             //

             // control     = <US-ASCII coded characters 00-1F and 7F hexadecimal>

             // space       = <US-ASCII coded character 20 hexadecimal>

             // delims      = "<" | ">" | "#" | "%" | <">

             //               %3C   %3E   %23   %25   %22

             // unwise      = "{" | "}" | "|" | "\" | "^" | "[" | "]" | "`"

             //               %7D   %7B   %7C   %5C   %5E   %5B   %5D   %60

             //

             // ".... Data corresponding to excluded characters must be escaped in order to

             // be properly represented within a URI....."

             // RFC 3986 Section 3.  Syntax Components

             //

             // "... The generic URI syntax consists of a hierarchical sequence of

             // components referred to as the scheme, authority, path, query, and

             // fragment.

             //

             //   URI         = scheme ":" hier-part [ "?" query ] [ "#" fragment ]

             //

             //   hier-part   = "//" authority path-abempty

             //               / path-absolute

             //               / path-rootless

             //               / path-empty

             // ...."

             // RFC 3986 Section 2.2:

             // Reserved characters (should not be percent-encoded)

             // reserved    = gen-delims / sub-delims

             // gen-delims  = ":" / "/" / "?" / "#" / "[" / "]" / "@"

             //               %3A   %2F   %3F   %23   %5B   %5D   %40

             // sub-delims  = "!" / "$" / "&" / "'" / "(" / ")" / "*" / "+" / "," / ";" / "="

             //               %21   %24   %26   %27   %28   %29   %2A   %2B   %2C   %3B   %3D

             // Note than chars "[" and "]" are mentioned as they should be escaped on RFC 2396,

             // but on the part D. Changes from RFC 2396 says about this chars (used on IPv6) 

             // "...those rules were redefined to directly specify the characters allowed...."

             // There is also other characters moved from excluded list to reserved:

             // "[" / "]" / "#"  

             // RFC 3986 Section 2.3:

             // "... for consistency, percent-encoded octets in the ranges of ALPHA

             // (%41-%5A and %61-%7A), DIGIT (%30-%39), hyphen (%2D), period (%2E),

             // underscore (%5F), or tilde (%7E) should not be created by URI

             // producers...."

             // RFC 3986 Section  3.2.2.  Host

             // host = IP-literal / IPv4address / reg-name

             // The reg-name syntax allows percent-encoded octets in order to

             // represent non-ASCII registered names in a uniform way that is

             // independent of the underlying name resolution technology.  Non-ASCII

             // characters must first be encoded according to UTF-8 [STD63], and then

             // each octet of the corresponding UTF-8 sequence must be percent-

             // encoded to be represented as URI characters.  URI producing

             // applications must not use percent-encoding in host unless it is used

             // to represent a UTF-8 character sequence.

             // RFC 3986 Section 3.4 Query 

             //         query       = *( pchar / "/" / "?" )

             //

             // "...  However, as query components are often used to carry identifying information 

             // in the form of "key=value" pairs and one frequently used value is a reference to

             // another URI, it is sometimes better for usability to avoid percent-encoding those characters....."

             //

             // RFC 3986 Section 2.5 Identifying Data (Apply to query section)

             //

             // When a new URI scheme defines a component that represents textual

             // data consisting of characters from the Universal Character Set [UCS],

             // the data should first be encoded as octets according to the UTF-8

             // character encoding [STD63]; then only those octets that do not

             // correspond to characters in the unreserved set should be percent-

             // encoded.  For example, the character A would be represented as "A",

             // the character LATIN CAPITAL LETTER A WITH GRAVE would be represented

             // as "%C3%80", and the character KATAKANA LETTER A would be represented

             // as "%E3%82%A2".

             //

             // RFC 3986 Section 3.5 Fragment

             //         fragment    = *( pchar / "/" / "?" )

             //

             // Note that follows the same as query

             // Based on the extracts the strategy to apply on this method is:

             // 

             // On scheme ":" hier-part

             //

             // Escape or percent encode chars inside :

             // 

             // - From %00 to %20, 

             // - <"> %22, "%" %25 (If there is encode of "%", there is a risk of 

             //                     duplicate encoding, encode it when we are sure 

             //                     that there are not encoded twice)

             // - "<" %3C, ">" %3E

             // - "\" %5C, "^" %5E, "`" %60 

             // - "{" %7B, "|" %7C, "}" %7D

             // - From %7F ad infinitum (characters from %100 to infinitum should not be used in this

             //   part of an URI, but it is preferred to encode it that omit it).

             //

             // The remaining characters must not be encoded

             //

             // Characters after ? or # should be percent encoding but only the necessary ones:

             //

             // - From %00 to %20 (' ' %20 could encode as +, but %20 also works, so we keep %20)

             // - <"> %22, "%" %25 (If there is encode of "%", there is a risk of 

             //                     duplicate encoding, encode it when we are sure 

             //                     that there are not encoded twice)

             // - "<" %3C, ">" %3E,

             // - "\" %5C, "^" %5E, "`" %60 

             // - "{" %7B, "|" %7C, "}" %7D

             // - From %7F ad infinitum (each character as many bytes as necessary but take into account

             //   that a single char should contain 2,3 or more bytes!. This data should be encoded 

             //   translating from the document character encoding to percent encoding, because this values

             //   could be retrieved from httpRequest.getParameter() and it uses the current character encoding

             //   for decode values)

             //

             // "&" should be encoded as "&" because this link is inside an html page, and 

             // put only & is invalid in this context.

             if (   (c <= (char)0x20) || (c >= (char)0x7F) || 

                     c == '"' || c == '<' ||

                     c == '>' || c == '\\' || c == '^' || c == '`' ||

                     c == '{' || c == '|' || c == '}')

             {

                 // The percent encoding on this part should be done using UTF-8 charset

                 // as RFC 3986 Section 3.2.2 says.

                 // Also there is a reference on 

                 // http://www.w3.org/TR/html40/appendix/notes.html#non-ascii-chars

                 // that recommend use of UTF-8 instead the document character encoding.

                 // Jetty set by default UTF-8 (see http://jira.codehaus.org/browse/JETTY-113)

                 app = percentEncode(c, "UTF-8");

             }

             else if (c == '%')

             {

                 if (i + 2 < length)

                 {

                     char c1 = string.charAt(i+1);

                     char c2 = string.charAt(i+2);

                     if ((( c1 >= '0' && c1 <='9') || (c1 >='A' && c1 <='Z') || (c1 >='a' && c1 <='z')) &&

                         (( c2 >= '0' && c2 <='9') || (c2 >='A' && c2 <='Z') || (c2 >='a' && c2 <='z')))

                     {

                         // do not percent encode, because it could be already encoded

                         // and we don't want encode it twice

                     }

                     else

                     {

                         app = percentEncode(c, UTF8);

                     }

                 }

                 else

                 {

                     app = percentEncode(c, UTF8);

                 }

             }

             else if (c == '?' || c == '#')

             {

                 if (i+1 < length)

                 {

                     // The remaining part of the URI are data that should be encoded

                     // using the document character encoding.

                     app = c + encodeURIQuery(string.substring(i+1), characterEncoding);

                     endLoop = true;

                 }

             }

             else

             {

                 //No encoding, just do nothing, char will be added later.

             }

             if (app != null)

             {

                 if (sb == null)

                 {

                     sb = new StringBuilder(string.substring(0, i));

                 }

                 sb.append(app);

             }

             else

             {

                 if (sb != null)

                 {

                     sb.append(c);

                 }

             }

             if (endLoop)

             {

                 break;

             }

         }

         if (sb == null)

         {

             return string;

         }

         else

         {

             return sb.toString();

         }

     }

     /**

      * Encode a unicode char value in percentEncode, decoding its bytes using a specified 

      * characterEncoding.

      * 

      * @param c

      * @param characterEncoding

      * @return

      */

     private static String percentEncode(char c, String characterEncoding)

     {

         String app = null;

         if (c > (char)((short)0x007F))

         {

             //percent encode in the proper encoding to be consistent

             app = percentEncodeNonUsAsciiCharacter(c, characterEncoding);

         }

         else

         {

             //percent encode US-ASCII char (0x00-0x7F range)

             app = "%" + HEX_CHARSET.charAt( ((c >> 0x4) % 0x10)) +HEX_CHARSET.charAt(c % 0x10);

         }

         return app;

     }

     private static String percentEncodeNonUsAsciiCharacter(char c, String characterEncoding)

     {

         ByteArrayOutputStream baos = new ByteArrayOutputStream(10);

         StringBuilder builder = new StringBuilder();

         try

         {

             OutputStreamWriter writer = new OutputStreamWriter(baos,characterEncoding);

             writer.write(c);

             writer.flush();

         }

         catch(IOException e)

         {

             baos.reset();

             return null;

         }

         byte [] byteArray =  baos.toByteArray();

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

         {

             builder.append('%');

             builder.append(HEX_CHARSET.charAt( (( ((short) byteArray[i] & 0xFF ) >> 0x4) % 0x10)) );

             builder.append(HEX_CHARSET.charAt( ((short) byteArray[i] & 0xFF ) % 0x10));

         }

         return builder.toString();

     }

     /**

      * Encode the query part using the document charset encoding provided.

      * 

      * 

      * @param string

      * @param characterEncoding

      * @return

      */

     private static String encodeURIQuery(final String string, final String characterEncoding)

     {

         StringBuilder sb = null;    //create later on demand

         String app;

         char c;

         boolean endLoop = false;

         int length = string.length();

         for (int i = 0; i < length; ++i)

         {

             app = null;

             c = string.charAt(i);

             // - From %00 to %20 (' ' %20 could encode as +, but %20 also works, so we keep %20)

             // - <"> %22 (If there is encode of "%", there is a risk of duplicate encoding, so 

             //            we make easier and omit this one)

             // - "<" %3C, ">" %3E,

             // - "\" %5C, "^" %5E, "`" %60 

             // - "{" %7B, "|" %7C, "}" %7D

             // - From %7F ad infinitum (each character as many bytes as necessary but take into account

             //   that a single char should contain 2,3 or more bytes!. This data should be encoded 

             //   translating from the document character encoding to percent encoding)

             //

             // "&" should be encoded as "&" because this link is inside an html page, and 

             // put & is invalid in this context   

             if (   (c <= (char)0x20) || (c >= (char)0x7F) || 

                     c == '"' || c == '<' ||

                     c == '>' || c == '\\' || c == '^' || c == '`' ||

                     c == '{' || c == '|' || c == '}')

             {

                 // The percent encoding on this part should be done using UTF-8 charset

                 // as RFC 3986 Section 3.2.2 says

                 app = percentEncode(c, characterEncoding);

             }

             else if (c == '%')

             {

                 if (i + 2 < length)

                 {

                     char c1 = string.charAt(i+1);

                     char c2 = string.charAt(i+2);

                     if ((( c1 >= '0' && c1 <='9') || (c1 >='A' && c1 <='Z') || (c1 >='a' && c1 <='z')) &&

                         (( c2 >= '0' && c2 <='9') || (c2 >='A' && c2 <='Z') || (c2 >='a' && c2 <='z')))

                     {

                         // do not percent encode, because it could be already encoded

                     }

                     else

                     {

                         app = percentEncode(c, characterEncoding);

                     }

                 }

                 else

                 {

                     app = percentEncode(c, characterEncoding);

                 }

             }

             else if (c == '&')

             {

                 if (i+4 < length )

                 {

                     if ('a' == string.charAt(i+1) &&

                         'm' == string.charAt(i+2) &&

                         'p' == string.charAt(i+3) &&

                         ';' == string.charAt(i+4))

                     {

                         //Skip

                     }

                     else

                     {

                         app = "&";

                     }

                 }

                 else

                 {

                     app = "&";

                 }

             }

             else

             {

                 //No encoding, just do nothing, char will be added later.

             }

             if (app != null)

             {

                 if (sb == null)

                 {

                     sb = new StringBuilder(string.substring(0, i));

                 }

                 sb.append(app);

             }

             else

             {

                 if (sb != null)

                 {

                     sb.append(c);

                 }

             }

             if (endLoop)

             {

                 break;

             }

         }

         if (sb == null)

         {

             return string;

         }

         else

         {

             return sb.toString();

         }

     }

     /**

      * Encode an URI, escaping or percent-encoding all required characters and

      * following the rules mentioned on RFC 3986.  

      * 

      * @param string

      * @param encodeNonLatin

      * @return

      * @throws IOException

      */

     public static void encodeURIAttribute(Writer writer, final String string, final String characterEncoding)

         throws IOException

     {

         //StringBuilder sb = null;    //create later on demand

         int start = 0;

         String app;

         char c;

         boolean endLoop = false;

         int length = string.length();

         for (int i = 0; i < length; ++i)

         {

             app = null;

             c = string.charAt(i);

             // This are the guidelines to be taken into account by this algorithm to encode:

             // RFC 2396 Section 2.4.3 Excluded US-ASCII Characters

             //

             // control     = <US-ASCII coded characters 00-1F and 7F hexadecimal>

             // space       = <US-ASCII coded character 20 hexadecimal>

             // delims      = "<" | ">" | "#" | "%" | <">

             //               %3C   %3E   %23   %25   %22

             // unwise      = "{" | "}" | "|" | "\" | "^" | "[" | "]" | "`"

             //               %7D   %7B   %7C   %5C   %5E   %5B   %5D   %60

             //

             // ".... Data corresponding to excluded characters must be escaped in order to

             // be properly represented within a URI....."

             // RFC 3986 Section 3.  Syntax Components

             //

             // "... The generic URI syntax consists of a hierarchical sequence of

             // components referred to as the scheme, authority, path, query, and

             // fragment.

             //

             //   URI         = scheme ":" hier-part [ "?" query ] [ "#" fragment ]

             //

             //   hier-part   = "//" authority path-abempty

             //               / path-absolute

             //               / path-rootless

             //               / path-empty

             // ...."

             // RFC 3986 Section 2.2:

             // Reserved characters (should not be percent-encoded)

             // reserved    = gen-delims / sub-delims

             // gen-delims  = ":" / "/" / "?" / "#" / "[" / "]" / "@"

             //               %3A   %2F   %3F   %23   %5B   %5D   %40

             // sub-delims  = "!" / "$" / "&" / "'" / "(" / ")" / "*" / "+" / "," / ";" / "="

             //               %21   %24   %26   %27   %28   %29   %2A   %2B   %2C   %3B   %3D

             // Note than chars "[" and "]" are mentioned as they should be escaped on RFC 2396,

             // but on the part D. Changes from RFC 2396 says about this chars (used on IPv6) 

             // "...those rules were redefined to directly specify the characters allowed...."

             // There is also other characters moved from excluded list to reserved:

             // "[" / "]" / "#"  

             // RFC 3986 Section 2.3:

             // "... for consistency, percent-encoded octets in the ranges of ALPHA

             // (%41-%5A and %61-%7A), DIGIT (%30-%39), hyphen (%2D), period (%2E),

             // underscore (%5F), or tilde (%7E) should not be created by URI

             // producers...."

             // RFC 3986 Section  3.2.2.  Host

             // host = IP-literal / IPv4address / reg-name

             // The reg-name syntax allows percent-encoded octets in order to

             // represent non-ASCII registered names in a uniform way that is

             // independent of the underlying name resolution technology.  Non-ASCII

             // characters must first be encoded according to UTF-8 [STD63], and then

             // each octet of the corresponding UTF-8 sequence must be percent-

             // encoded to be represented as URI characters.  URI producing

             // applications must not use percent-encoding in host unless it is used

             // to represent a UTF-8 character sequence.

             // RFC 3986 Section 3.4 Query 

             //         query       = *( pchar / "/" / "?" )

             //

             // "...  However, as query components are often used to carry identifying information 

             // in the form of "key=value" pairs and one frequently used value is a reference to

             // another URI, it is sometimes better for usability to avoid percent-encoding those characters....."

             //

             // RFC 3986 Section 2.5 Identifying Data (Apply to query section)

             //

             // When a new URI scheme defines a component that represents textual

             // data consisting of characters from the Universal Character Set [UCS],

             // the data should first be encoded as octets according to the UTF-8

             // character encoding [STD63]; then only those octets that do not

             // correspond to characters in the unreserved set should be percent-

             // encoded.  For example, the character A would be represented as "A",

             // the character LATIN CAPITAL LETTER A WITH GRAVE would be represented

             // as "%C3%80", and the character KATAKANA LETTER A would be represented

             // as "%E3%82%A2".

             //

             // RFC 3986 Section 3.5 Fragment

             //         fragment    = *( pchar / "/" / "?" )

             //

             // Note that follows the same as query

             // Based on the extracts the strategy to apply on this method is:

             // 

             // On scheme ":" hier-part

             //

             // Escape or percent encode chars inside :

             // 

             // - From %00 to %20, 

             // - <"> %22, "%" %25 (If there is encode of "%", there is a risk of 

             //                     duplicate encoding, encode it when we are sure 

             //                     that there are not encoded twice)

             // - "<" %3C, ">" %3E

             // - "\" %5C, "^" %5E, "`" %60 

             // - "{" %7B, "|" %7C, "}" %7D

             // - From %7F ad infinitum (characters from %100 to infinitum should not be used in this

             //   part of an URI, but it is preferred to encode it that omit it).

             //

             // The remaining characters must not be encoded

             //

             // Characters after ? or # should be percent encoding but only the necessary ones:

             //

             // - From %00 to %20 (' ' %20 could encode as +, but %20 also works, so we keep %20)

             // - <"> %22, "%" %25 (If there is encode of "%", there is a risk of 

             //                     duplicate encoding, encode it when we are sure 

             //                     that there are not encoded twice)

             // - "<" %3C, ">" %3E,

             // - "\" %5C, "^" %5E, "`" %60 

             // - "{" %7B, "|" %7C, "}" %7D

             // - From %7F ad infinitum (each character as many bytes as necessary but take into account

             //   that a single char should contain 2,3 or more bytes!. This data should be encoded 

             //   translating from the document character encoding to percent encoding, because this values

             //   could be retrieved from httpRequest.getParameter() and it uses the current character encoding

             //   for decode values)

             //

             // "&" should be encoded as "&" because this link is inside an html page, and 

             // put only & is invalid in this context.

             if (   (c <= (char)0x20) || (c >= (char)0x7F) || 

                     c == '"' || c == '<' ||

                     c == '>' || c == '\\' || c == '^' || c == '`' ||

                     c == '{' || c == '|' || c == '}')

             {

                 // The percent encoding on this part should be done using UTF-8 charset

                 // as RFC 3986 Section 3.2.2 says.

                 // Also there is a reference on 

                 // http://www.w3.org/TR/html40/appendix/notes.html#non-ascii-chars

                 // that recommend use of UTF-8 instead the document character encoding.

                 // Jetty set by default UTF-8 (see http://jira.codehaus.org/browse/JETTY-113)

                 //app = percentEncode(c, "UTF-8");

                 if (start < i)

                 {

                     writer.write(string, start, i-start);

                 }

                 start = i+1;

                 percentEncode(writer, c, "UTF-8");

             }

             else if (c == '%')

             {

                 if (i + 2 < length)

                 {

                     char c1 = string.charAt(i+1);

                     char c2 = string.charAt(i+2);

                     if ((( c1 >= '0' && c1 <='9') || (c1 >='A' && c1 <='Z') || (c1 >='a' && c1 <='z')) &&

                         (( c2 >= '0' && c2 <='9') || (c2 >='A' && c2 <='Z') || (c2 >='a' && c2 <='z')))

                     {

                         // do not percent encode, because it could be already encoded

                         // and we don't want encode it twice

                     }

                     else

                     {

                         //app = percentEncode(c, UTF8);

                         if (start < i)

                         {

                             writer.write(string, start, i-start);

                         }

                         start = i+1;

                         percentEncode(writer, c, UTF8);

                     }

                 }

                 else

                 {

                     //app = percentEncode(c, UTF8);

                     if (start < i)

                     {

                         writer.write(string, start, i-start);

                     }

                     start = i+1;

                     percentEncode(writer, c, UTF8);

                 }

             }

             else if (c == '?' || c == '#')

             {

                 if (i+1 < length)

                 {

                     // The remaining part of the URI are data that should be encoded

                     // using the document character encoding.

                     //app = c + encodeURIQuery(string.substring(i+1), characterEncoding);

                     if (start < i)

                     {

                         writer.write(string, start, i-start);

                     }

                     start = i+1;

                     writer.write(c);

                     //encodeURIQuery(writer, string.substring(i+1), characterEncoding);

                     encodeURIQuery(writer, string, i+1, characterEncoding);

                     endLoop = true;

                 }

             }

             else

             {

                 //No encoding, just do nothing, char will be added later.

             }

             if (app != null)

             {

                 //if (sb == null)

                 //{

                 //    sb = new StringBuilder(string.substring(0, i));

                 //}

                 //sb.append(app);

                 if (start < i)

                 {

                     writer.write(string, start, i-start);

                 }

                 start = i+1;

                 writer.write(app);

             }

             //else

             //{

             //    if (sb != null)

             //    {

             //        sb.append(c);

             //    }

             //}

             if (endLoop)

             {

                 start = length;

                 break;

             }

         }

         //if (sb == null)

         //{

         //    return string;

         //}

         //else

         //{

         //    return sb.toString();

         //}

         if (start == 0)

         {

             writer.write(string);

         }

         else if (start < length)

         {

             writer.write(string,start,length-start);

         }

     }

     /**

      * Encode a unicode char value in percentEncode, decoding its bytes using a specified 

      * characterEncoding.

      * 

      * @param c

      * @param characterEncoding

      * @return

      */

     private static void percentEncode(Writer writer, char c, String characterEncoding) throws IOException

     {

         String app = null;

         if (c > (char)((short)0x007F))

         {

             //percent encode in the proper encoding to be consistent

             //app = percentEncodeNonUsAsciiCharacter(writer c, characterEncoding);

             percentEncodeNonUsAsciiCharacter(writer, c, characterEncoding);

         }

         else

         {

             //percent encode US-ASCII char (0x00-0x7F range)

             //app = "%" + HEX_CHARSET.charAt( ((c >> 0x4) % 0x10)) +HEX_CHARSET.charAt(c % 0x10);

             writer.write('%');

             writer.write(HEX_CHARSET.charAt( ((c >> 0x4) % 0x10)));

             writer.write(HEX_CHARSET.charAt(c % 0x10));

         }

         //return app;

     }

     private static void percentEncodeNonUsAsciiCharacter(Writer currentWriter, char c, String characterEncoding) 

         throws IOException

     {

         ByteArrayOutputStream baos = new ByteArrayOutputStream(10);

         try

         {

             OutputStreamWriter writer = new OutputStreamWriter(baos,characterEncoding);

             writer.write(c);

             writer.flush();

         }

         catch(IOException e)

         {

             baos.reset();

             return;

         }

         byte [] byteArray =  baos.toByteArray();

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

         {

             //builder.append('%');

             //builder.append(HEX_CHARSET.charAt( (( ((short) byteArray[i] & 0xFF ) >> 0x4) % 0x10)) );

             //builder.append(HEX_CHARSET.charAt( ((short) byteArray[i] & 0xFF ) % 0x10));

             currentWriter.write('%');

             currentWriter.write(HEX_CHARSET.charAt( (( ((short) byteArray[i] & 0xFF ) >> 0x4) % 0x10)) );

             currentWriter.write(HEX_CHARSET.charAt( ((short) byteArray[i] & 0xFF ) % 0x10));

         }

         //return builder.toString();

     }

     /**

      * Encode the query part using the document charset encoding provided.

      * 

      * 

      * @param string

      * @param characterEncoding

      * @return

      */

     private static void encodeURIQuery(Writer writer, final String string, int offset, final String characterEncoding)

             throws IOException

     {

         //StringBuilder sb = null;    //create later on demand

         int start = offset;

         int length = string.length();

         int realLength = length-offset;

         String app;

         char c;

         //boolean endLoop = false;

         for (int i = offset; i < length; ++i)

         {

             app = null;

             c = string.charAt(i);

             // - From %00 to %20 (' ' %20 could encode as +, but %20 also works, so we keep %20)

             // - <"> %22 (If there is encode of "%", there is a risk of duplicate encoding, so 

             //            we make easier and omit this one)

             // - "<" %3C, ">" %3E,

             // - "\" %5C, "^" %5E, "`" %60 

             // - "{" %7B, "|" %7C, "}" %7D

             // - From %7F ad infinitum (each character as many bytes as necessary but take into account

             //   that a single char should contain 2,3 or more bytes!. This data should be encoded 

             //   translating from the document character encoding to percent encoding)

             //

             // "&" should be encoded as "&" because this link is inside an html page, and 

             // put & is invalid in this context   

             if (   (c <= (char)0x20) || (c >= (char)0x7F) || 

                     c == '"' || c == '<' ||

                     c == '>' || c == '\\' || c == '^' || c == '`' ||

                     c == '{' || c == '|' || c == '}')

             {

                 // The percent encoding on this part should be done using UTF-8 charset

                 // as RFC 3986 Section 3.2.2 says

                 //app = percentEncode(c, characterEncoding);

                 if (start < i)

                 {

                     writer.write(string, start, i-start);

                 }

                 start = i+1;

                 percentEncode(writer, c, characterEncoding);

             }

             else if (c == '%')

             {

                 if (i + 2 < length)

                 {

                     char c1 = string.charAt(i+1);

                     char c2 = string.charAt(i+2);

                     if ((( c1 >= '0' && c1 <='9') || (c1 >='A' && c1 <='Z') || (c1 >='a' && c1 <='z')) &&

                         (( c2 >= '0' && c2 <='9') || (c2 >='A' && c2 <='Z') || (c2 >='a' && c2 <='z')))

                     {

                         // do not percent encode, because it could be already encoded

                     }

                     else

                     {

                         //app = percentEncode(c, characterEncoding);

                         if (start < i)

                         {

                             writer.write(string, start, i-start);

                         }

                         start = i+1;

                         percentEncode(writer, c, characterEncoding);

                     }

                 }

                 else

                 {

                     //app = percentEncode(c, characterEncoding);

                     if (start < i)

                     {

                         writer.write(string, start, i-start);

                     }

                     start = i+1;

                     percentEncode(writer, c, characterEncoding);

                 }