/*
    *  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;
          for (int i = 0; i < string.length (); ++i)
          {
              app = null;
              c = string.charAt(i);
              
              // All characters before letters
              if ((int)c < 0x41)
              {
                  switch (c)
                  {
                      case '"': app = "&quot;"; break;    //"
                      case '&': app = "&amp;"; break;     //&
                      case '<': app = "&lt;"; break;      //<
                      case '>': app = "&gt;"; break;      //>
                      case ' ':
                          if (encodeSubsequentBlanksToNbsp &&
                                  (i == 0 || (i - 1 >= 0 && string.charAt(i - 1) == ' ')))
                          {
                              //Space at beginning or after another space
                              app = "&#160;";
                          }
                          break;
                      case '\n':
                          if (encodeNewline)
                          {
                             app = "<br/>";
                         }
                         break;
                 }
             } else if (encodeNonLatin && (int)c > 0x80) {
                  switch(c) {
                     //german umlauts
                     case '\u00E4' : app = "&auml;";  break;
                     case '\u00C4' : app = "&Auml;";  break;
                     case '\u00F6' : app = "&ouml;";  break;
                     case '\u00D6' : app = "&Ouml;";  break;
                     case '\u00FC' : app = "&uuml;";  break;
                     case '\u00DC' : app = "&Uuml;";  break;
                     case '\u00DF' : app = "&szlig;"; break;
 
                     //misc
                     //case 0x80: app = "&euro;"; break;  sometimes euro symbol is ascii 128, should we suport it?
                     case '\u20AC': app = "&euro;";  break;
                     case '\u00AB': app = "&laquo;"; break;
                     case '\u00BB': app = "&raquo;"; break;
                     case '\u00A0': app = "&#160;"; 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 (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 &lt;br&gt;'s
      * @param encodeSubsequentBlanksToNbsp if true subsequent blanks are converted to &amp;nbsp;'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;
         
         for (int i = offset; i < offset + realLength; ++i)
         {
             app = null;
             c = string[i];
 
             // All characters before letters
             if ((int)c < 0x41)
             {
                 switch (c)
                 {
                     case '"': app = "&quot;"; break;    //"
                     case '&': app = "&amp;"; break;     //&
                     case '<': app = "&lt;"; break;      //<
                     case '>': app = "&gt;"; break;      //>
                     case ' ':
                         if (encodeSubsequentBlanksToNbsp &&
                                 (i == 0 || (i - 1 >= 0 && string[i - 1] == ' ')))
                         {
                             //Space at beginning or after another space
                             app = "&#160;";
                         }
                         break;
                     case '\n':
                         if (encodeNewline)
                         {
                             app = "<br/>";
                         }
                         break;
                 }
             } else if (encodeNonLatin && (int)c > 0x80) {
                  switch(c) {
                     //german umlauts
                     case '\u00E4' : app = "&auml;";  break;
                     case '\u00C4' : app = "&Auml;";  break;
                     case '\u00F6' : app = "&ouml;";  break;
                     case '\u00D6' : app = "&Ouml;";  break;
                     case '\u00FC' : app = "&uuml;";  break;
                     case '\u00DC' : app = "&Uuml;";  break;
                     case '\u00DF' : app = "&szlig;"; break;
 
                     //misc
                     //case 0x80: app = "&euro;"; break;  sometimes euro symbol is ascii 128, should we suport it?
                     case '\u20AC': app = "&euro;";  break;
                     case '\u00AB': app = "&laquo;"; break;
                     case '\u00BB': app = "&raquo;"; break;
                     case '\u00A0': app = "&#160;"; 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);
             } else {
                 if (sb != null)
                 {
                     sb.append(c);
                 }
             }
         }
 
         if (sb == null)
         {
             writer.write(string, offset, realLength);
         }
         else
         {
             writer.write(sb.toString());
         }
     }
     
     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 encodeURIAtributte(final String string, final String characterEncoding)
         throws IOException
     {
         StringBuilder sb = null;    //create later on demand
         String app;
         char c;
         boolean endLoop = false;
         for (int i = 0; i < string.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 "&amp;" 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 < string.length())
                 {
                     char c1 = string.charAt(i+1);
                     char c2 = string.charAt(i+2);
                     if ((( c1 >= '0' && c1 <='9') || (c1 >='A' && c1 <='Z')) &&
                         (( c2 >= '0' && c2 <='9') || (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 < string.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);
         StringBuffer builder = new StringBuffer();
         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;
         for (int i = 0; i < string.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 "&amp;" 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 < string.length())
                 {
                     char c1 = string.charAt(i+1);
                     char c2 = string.charAt(i+2);
                     if ((( c1 >= '0' && c1 <='9') || (c1 >='A' && c1 <='Z')) &&
                         (( c2 >= '0' && c2 <='9') || (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 < string.length() )
                 {
                     if ('a' == string.charAt(i+1) &&
                         'm' == string.charAt(i+2) &&
                         'p' == string.charAt(i+3) &&
                         ';' == string.charAt(i+4))
                     {
                         //Skip
                     }
                     else
                     {
                         app = "&amp;";
                     }
                 }
                 else
                 {
                     app = "&amp;";
                 }
             }
             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();
         }
     }
 }