/* UIxMailPartHTMLViewer.m - this file is part of SOGo
 *
 * Copyright (C) 2007-2019 Inverse inc.
 *
 * This file is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2, or (at your option)
 * any later version.
 *
 * This file is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; see the file COPYING.  If not, write to
 * the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 */

#import <Foundation/NSDictionary.h>
#import <Foundation/NSData.h>

#import <SaxObjC/SaxLexicalHandler.h>
#import <SaxObjC/SaxXMLReaderFactory.h>
#import <NGExtensions/NSString+misc.h>
#import <NGExtensions/NSString+Encoding.h>
#import <NGMime/NGMimeBodyPart.h>
#import <NGMime/NGMimeType.h>

#include <libxml/encoding.h>

#import <SoObjects/SOGo/NSString+Utilities.h>
#import <SoObjects/Mailer/NSData+Mail.h>
#import <SoObjects/Mailer/SOGoMailAccounts.h>
#import <SoObjects/Mailer/SOGoMailObject.h>
#import <SoObjects/Mailer/SOGoMailBodyPart.h>

#import "UIxMailPartHTMLViewer.h"

#if 0
#define showWhoWeAre() NSLog(@"invoked '%@'", NSStringFromSelector(_cmd))
#else
#define showWhoWeAre()
#endif

/* Tags that are forbidden within the body of the html content */
static NSArray *BannedTags = nil;

/* Tags that can't have any contents (no end tag) */
static NSArray *VoidTags= nil;

static xmlCharEncoding
_xmlCharsetForCharset (NSString *charset)
{
  struct { NSString *name; xmlCharEncoding encoding; } xmlEncodings[] = {
    { @"us-ascii", XML_CHAR_ENCODING_ASCII},
    { @"utf-8", XML_CHAR_ENCODING_UTF8},
    { @"utf8", XML_CHAR_ENCODING_UTF8},		// broken mailers
    { @"utf-16le", XML_CHAR_ENCODING_UTF16LE},
    { @"utf-16be",  XML_CHAR_ENCODING_UTF16BE},
    { @"ucs-4le", XML_CHAR_ENCODING_UCS4LE},
    { @"ucs-4be", XML_CHAR_ENCODING_UCS4BE},
    { @"ebcdic", XML_CHAR_ENCODING_EBCDIC},
//     { @"iso-10646" , XML_CHAR_ENCODING_UCS4_2143},
//     {  , XML_CHAR_ENCODING_UCS4_3412},
//     { @"ucs-2", XML_CHAR_ENCODING_UCS2},
    { @"iso8859_1", XML_CHAR_ENCODING_8859_1},
    { @"iso-8859-1", XML_CHAR_ENCODING_8859_1},
    { @"iso-8859-2",  XML_CHAR_ENCODING_8859_2},
    { @"iso-8859-3", XML_CHAR_ENCODING_8859_3},
    { @"iso-8859-4", XML_CHAR_ENCODING_8859_4},
    { @"iso-8859-5", XML_CHAR_ENCODING_8859_5},
    { @"iso-8859-6", XML_CHAR_ENCODING_8859_6},
    { @"iso-8859-7", XML_CHAR_ENCODING_8859_7},
    { @"iso-8859-8", XML_CHAR_ENCODING_8859_8},
    { @"iso-8859-9", XML_CHAR_ENCODING_8859_9},
    { @"iso-8859-13", XML_CHAR_ENCODING_ERROR},
    { @"iso-2022-jp", XML_CHAR_ENCODING_2022_JP},
//     { @"iso-2022-jp", XML_CHAR_ENCODING_SHIFT_JIS},
    { @"koi8-r", XML_CHAR_ENCODING_ERROR},       // unsupported, will trigger koi8-r -> utf8 conversion
    { @"windows-1250", XML_CHAR_ENCODING_ERROR}, // unsupported, will trigger windows-1250 -> utf8 conversion
    { @"windows-1251", XML_CHAR_ENCODING_ERROR}, // unsupported, will trigger windows-1251 -> utf8 conversion
    { @"windows-1255", XML_CHAR_ENCODING_ERROR}, // unsupported, will trigger windows-1255 -> utf8 conversion
    { @"windows-1256", XML_CHAR_ENCODING_ERROR}, // unsupported, will trigger windows-1255 -> utf8 conversion
    { @"windows-1257", XML_CHAR_ENCODING_ERROR}, // unsupported, will trigger windows-1257 -> utf8 conversion
    { @"gb2312", XML_CHAR_ENCODING_ERROR},       // unsupported, will trigger gb2312 -> utf8 conversion
    { @"gbk", XML_CHAR_ENCODING_ERROR},          // unsupported, will trigger gb2312 -> utf8 conversion
    { @"gb18030", XML_CHAR_ENCODING_ERROR},      // unsupported, will trigger gb2312 -> utf8 conversion
    { @"big5", XML_CHAR_ENCODING_ERROR},         // unsupported, will trigger gb2312 -> utf8 conversion
    { @"euc-jp", XML_CHAR_ENCODING_EUC_JP}};
  unsigned count;
  xmlCharEncoding encoding;

  encoding = XML_CHAR_ENCODING_NONE;
  count = 0;

  while (encoding == XML_CHAR_ENCODING_NONE
	 && count < (sizeof (xmlEncodings) / sizeof (xmlEncodings[0])))
    if ([charset isEqualToString: xmlEncodings[count].name])
      encoding = xmlEncodings[count].encoding;
    else
      count++;

  if (encoding == XML_CHAR_ENCODING_NONE)
    encoding = XML_CHAR_ENCODING_8859_1;

  return encoding;
}

@interface _UIxHTMLMailContentHandler : NSObject <SaxContentHandler, SaxLexicalHandler>
{
  NSMutableString *result;
  NSMutableString *css;
  NSDictionary *attachmentIds;
  int ignoredContent, embeddedCSSLevel;
  NSString *ignoreTag;
  BOOL inBody;
  BOOL inStyle;
  BOOL inCSSDeclaration;
  BOOL hasEmbeddedCSS;
  xmlCharEncoding contentEncoding;
}

- (NSString *) result;

@end

@implementation _UIxHTMLMailContentHandler

+ (void) initialize
{
  if (!BannedTags)
    BannedTags = [[NSArray alloc] initWithObjects: @"script", @"frameset",
                                  @"frame", @"iframe", @"applet", @"link",
                                  @"base", @"meta", @"title", nil];
  if (!VoidTags)
    {
      /* see http://www.w3.org/TR/html4/index/elements.html */
      VoidTags = [[NSArray alloc] initWithObjects: @"area", @"base",
                                  @"basefont", @"br", @"col", @"frame", @"hr",
                                  @"img", @"input", @"isindex", @"link",
                                @"meta", @"param", @"", nil];
    }
}

- (id) init
{
  if ((self = [super init]))
    {
      css = nil;
      result = nil;
      ignoreTag = nil;
      attachmentIds = nil;
      contentEncoding = XML_CHAR_ENCODING_UTF8;
    }

  return self;
}

- (void) dealloc
{
  [result release];
  [css release];
  [ignoreTag release];
  [super dealloc];
}

- (void) setContentEncoding: (xmlCharEncoding) newContentEncoding
{
  contentEncoding = newContentEncoding;
}

- (xmlCharEncoding) contentEncoding
{
  return contentEncoding;
}

- (void) setAttachmentIds: (NSDictionary *) newAttachmentIds
{
  attachmentIds = newAttachmentIds;
}

- (NSString *) css
{
  return css;
}

- (NSString *) result
{
  return result;
}

/* SaxContentHandler */
- (void) startDocument
{
  showWhoWeAre();

  [css release];
  [result release];

  result = [NSMutableString new];
  css = [NSMutableString new];

  ignoredContent = 0;
  [ignoreTag release];
  ignoreTag = nil;

  inBody = NO;
  inStyle = NO;
  inCSSDeclaration = NO;
  hasEmbeddedCSS = NO;
  embeddedCSSLevel = 0;
}

- (void) endDocument
{
  showWhoWeAre();
}

- (void) startPrefixMapping: (NSString *)_prefix
                        uri: (NSString *)_uri
{
  showWhoWeAre();
}

- (void) endPrefixMapping: (NSString *)_prefix
{
  showWhoWeAre();
}

/**
 * About CSS At-Rules (https://css-tricks.com/the-at-rules-of-css/)
 *
 * At-Rules follow two possible synthaxes:
 *
 *   @[KEYWORD] (RULE);
 *     Examples:
 *       @charset "UTF-8";
 *       @import 'global.css';
 *       @namespace svg url(http://www.w3.org/2000/svg);
 *
 *   @[KEYWORD] { (Nested Statements) }
 *     Examples:
 *       @font-face {
 *         font-family: 'MyWebFont';
 *         src:  url('myfont.woff2') format('woff2'),
 *               url('myfont.woff') format('woff');
 *       }
 *       @media only screen
 *         and (min-device-width: 320px)
 *         and (max-device-width: 480px)
 *         and (-webkit-min-device-pixel-ratio: 2) {
 *           .module { width: 100%; }
 *       }
 */
- (void) _appendStyle: (unichar *) _chars
               length: (NSUInteger) _len
{
  NSMutableString *sanitizedStyle, *declaration, *rule;
  NSUInteger count, length, max;
  unichar *sanitizedChars, *start, *currentChar;
  BOOL inComment;

  /**
   * Sanitize style
   *   - remove control characters
   *   - remove HTML comment delimiters
   *   - remove CSS comments
   */
  sanitizedStyle = [NSMutableString string];
  inComment = NO;
  start = _chars;
  for (count = 0; count < _len; count++)
    {
      currentChar = _chars + count;
      if (*currentChar < 32)
        {
          // Ignore control characters
          if (!inComment && currentChar > start)
            [sanitizedStyle appendString: [NSString stringWithCharacters: start
                                                                  length: (currentChar - start)]];
          start = currentChar + 1;
        }
      else
        {
          if ((currentChar < _chars + _len - 3) &&
              *currentChar     == '<' &&
              *(currentChar+1) == '!' &&
              *(currentChar+2) == '-' &&
              *(currentChar+3) == '-')
            {
              // Ignore starting HTML comment
              if (!inComment && currentChar > start)
                [sanitizedStyle appendString: [NSString stringWithCharacters: start
                                                                      length: (currentChar - start)]];
              start = currentChar + 4;
            }
          else if ((currentChar < _chars + _len - 2) &&
                   *currentChar     == '-' &&
                   *(currentChar+1) == '-' &&
                   *(currentChar+2) == '>')
            {
              // Ignore ending HTML comment
              if (!inComment && currentChar > start)
                [sanitizedStyle appendString: [NSString stringWithCharacters: start
                                                                      length: (currentChar - start)]];
              start = currentChar + 3;
            }
          if (currentChar < _chars + _len - 1)
            {
              // Ignore CSS comments
              if (*currentChar == '/' && *(currentChar+1) == '*')
                {
                  inComment = YES;
                  if (currentChar > start)
                    [sanitizedStyle appendString: [NSString stringWithCharacters: start
                                                                          length: (currentChar - start)]];
                }
              else if (*currentChar == '*' && *(currentChar+1) == '/')
                {
                  inComment = NO;
                  start = currentChar + 2;
                }
            }
        }
    }
  if (!inComment && currentChar > start)
    [sanitizedStyle appendString: [NSString stringWithCharacters: start
                                               length: (currentChar - start)]];

  /**
   * Parse sanitized style
   *   - remove at-rule definitions
   *   - add custom class to selectors
   *   - add !important suffix to all rules
   */
  rule = [NSMutableString string];
  max = [sanitizedStyle length];
  sanitizedChars = NSZoneMalloc (NULL, max * sizeof (unichar));
  [sanitizedStyle getCharacters: sanitizedChars];
  start = sanitizedChars;
  currentChar = start;
  for (count = 0; count < max; count++)
    {
      currentChar = sanitizedChars + count;
      if (inCSSDeclaration)
        {
          if (*currentChar == '}')
            {
              // Prefix CSS rule including ending curly bracket
              inCSSDeclaration = NO;
              length = (currentChar - start) + 1;
              [declaration appendString: [NSString stringWithCharacters: start length: length]];
              [css appendString: declaration];
              start = currentChar + 1;
            }
          else if (*currentChar == ';')
            {
              // Add !important
              if ((currentChar < sanitizedChars + 10) ||
                  !((*(currentChar-1) == 't' || *(currentChar-1) == 'T') &&
                    (*(currentChar-2) == 'n' || *(currentChar-2) == 'N') &&
                    (*(currentChar-3) == 'a' || *(currentChar-3) == 'A') &&
                    (*(currentChar-4) == 't' || *(currentChar-4) == 'T') &&
                    (*(currentChar-5) == 'r' || *(currentChar-5) == 'R') &&
                    (*(currentChar-6) == 'o' || *(currentChar-6) == 'O') &&
                    (*(currentChar-7) == 'p' || *(currentChar-7) == 'P') &&
                    (*(currentChar-8) == 'm' || *(currentChar-8) == 'M') &&
                    (*(currentChar-9) == 'i' || *(currentChar-9) == 'I') &&
                    *(currentChar-10) == '!'))
                {
                  length = (currentChar - start);
                  [declaration appendFormat: @"%@ !important;",
                               [NSString stringWithCharacters: start length: length]];
                  start = currentChar + 1;
                }
            }
        }
      else
        {
          if (*currentChar == '{')
            {
              if (hasEmbeddedCSS)
                {
                  embeddedCSSLevel++;
                }
              else
                {
                  // Start of rule declaration
                  inCSSDeclaration = YES;
                  length = (currentChar - start);
                  [rule appendFormat: @".SOGoHTMLMail-CSS-Delimiter %@ {",
                        [NSString stringWithCharacters: start length: length]];
                  [css appendString: rule];
                  rule = [NSMutableString string];
                  declaration = [NSMutableString string];
                }
              start = currentChar + 1;
            }
          if (*currentChar == '}')
            {
              if (hasEmbeddedCSS)
                {
                  embeddedCSSLevel--;
                  if (embeddedCSSLevel <= 0)
                    hasEmbeddedCSS = NO;
                }
              else
                {
                  // CSS syntax error: ending declaration character while not in a CSS declaration.
                  // Ignore eveything from last CSS declaration.
                  rule = [NSMutableString string];
                }
              start = currentChar + 1;
            }
          else if (*currentChar == ',')
            {
              if (!hasEmbeddedCSS)
                {
                  // Prefix CSS selector
                  length = (currentChar - start);
                  [rule appendFormat: @" .SOGoHTMLMail-CSS-Delimiter %@,",
                        [NSString stringWithCharacters: start length: length]];
                }
              start = currentChar + 1;
            }
          else if (*currentChar == '@')
            {
              // Start of at-rule definition
              hasEmbeddedCSS = YES;
              embeddedCSSLevel = 0;
            }
        }
    }
  if (currentChar > start)
    {
      [css appendString: [NSString stringWithCharacters: start
                                                 length: (currentChar - start)]];
    }
}

- (void) startElement: (NSString *) _localName
            namespace: (NSString *) _ns
              rawName: (NSString *) _rawName
           attributes: (id <SaxAttributes>) _attributes
{
  unsigned int count, max;
  NSString *name, *value, *cid, *lowerName, *lowerValue;
  NSMutableString *resultPart;
  BOOL skipAttribute;

  showWhoWeAre();

  lowerName = [_localName lowercaseString];
  if (inStyle || ignoredContent)
    ;
  else if ([lowerName isEqualToString: @"base"])
    ;
  else if ([lowerName isEqualToString: @"meta"])
    ;
  else if ([lowerName isEqualToString: @"body"])
    inBody = YES;
  else if ([lowerName isEqualToString: @"style"])
    inStyle = YES;
  else if (inBody)
    {
      if ([BannedTags containsObject: lowerName])
        {
          if (!ignoredContent)
            ignoreTag = [lowerName copy];
          ignoredContent++;
        }
      else
        {
          resultPart = [NSMutableString string];
          [resultPart appendFormat: @"<%@", _rawName];

          if ([VoidTags containsObject: lowerName])
            {
              if (!ignoredContent)
                ignoreTag = [lowerName copy];
              ignoredContent++;
            }
          max = [_attributes count];
          for (count = 0; count < max; count++)
            {
              skipAttribute = NO;
              name = [[_attributes nameAtIndex: count] lowercaseString];
              if ([name isEqualToString: @"src"])
                {
                  value = [_attributes valueAtIndex: count];
                  if ([value hasPrefix: @"cid:"])
                    {
                      cid = [NSString stringWithFormat: @"<%@>",
                             [value substringFromIndex: 4]];
                      value = [attachmentIds objectForKey: cid];
                      skipAttribute = (value == nil);
                    }
                  else if ([lowerName isEqualToString: @"img"])
                    {
                      /* [resultPart appendString:
                         @"src=\"/SOGo.woa/WebServerResources/empty.gif\""]; */
                      name = @"unsafe-src";
                    }
                  else
                    skipAttribute = YES;
                }
              else if ([name isEqualToString: @"background"] ||
                       (([name isEqualToString: @"data"]
                         || [name isEqualToString: @"classid"])
                        && [lowerName isEqualToString: @"object"]))
                {
                  value = [_attributes valueAtIndex: count];
                  name = [NSString stringWithFormat: @"unsafe-%@", name];
                }
              else if ([name isEqualToString: @"href"]
                       || [name isEqualToString: @"action"]
                       || [name isEqualToString: @"formaction"])
                {
                  value = [_attributes valueAtIndex: count];
                  lowerValue = [[value lowercaseString] stringByReplacingString: @"\""
                                                                     withString: @""];
                  skipAttribute =
                    ([lowerValue rangeOfString: @"://"].location == NSNotFound
                     && ![lowerValue hasPrefix: @"mailto:"]
                     && ![lowerValue hasPrefix: @"#"])
                    || [lowerValue rangeOfString: @"javascript:"].location != NSNotFound;
                  if (!skipAttribute)
                    [resultPart appendString: @" rel=\"noopener\""];
                }
              // Avoid: <div style="background:url('http://www.sogo.nu/fileadmin/sogo/logos/sogo.bts.png' ); width: 200px; height: 200px;" title="ssss">
              else if ([name isEqualToString: @"style"])
                {
                  value = [_attributes valueAtIndex: count];
                  lowerValue = [[value lowercaseString] stringByReplacingString: @"\""
                                                                     withString: @""];
                  if ([lowerValue rangeOfString: @"url"].location != NSNotFound)
                    name = [NSString stringWithFormat: @"unsafe-%@", name];
                }
	      else if ([name isEqualToString: @"rel"])
		{
		  skipAttribute = YES;
		}
	      else if ([name hasPrefix: @"on"])
		{
                  // on Events
		  skipAttribute = YES;
		}
              else
                value = [_attributes valueAtIndex: count];
              
              if (!skipAttribute)
                [resultPart appendFormat: @" %@=\"%@\"",
                            name, [value stringByReplacingString: @"\""
                                                  withString: @""]];
            }
          
          if ([VoidTags containsObject: lowerName])
            [resultPart appendString: @"/"];
          [resultPart appendString: @">"];
          [result appendString: resultPart];
        }
    }
}

- (void) _finishCSS
{
  [css replaceString: @"<!--" withString: @""];
  [css replaceString: @"-->" withString: @""];
  [css replaceString: @".SOGoHTMLMail-CSS-Delimiter body"
       withString: @".SOGoHTMLMail-CSS-Delimiter"];
}

- (void) endElement: (NSString *) _localName
          namespace: (NSString *) _ns
            rawName: (NSString *) _rawName
{
  NSString *lowerName;

  showWhoWeAre();

  lowerName = [_localName lowercaseString];

  if (ignoredContent)
    {
      if ([lowerName isEqualToString: ignoreTag])
        {
          ignoredContent--;
          if (!ignoredContent)
            {
              [ignoreTag release];
              ignoreTag = nil;
            }
        }
    }
  else
    {
      if (inStyle)
        {
          if ([lowerName isEqualToString: @"style"])
            {
              inStyle = NO;
              inCSSDeclaration = NO;
            }
        }
      else if (inBody)
        {
          if ([lowerName isEqualToString: @"body"])
            {
              // Assume <body> never ends to properly display incorrectly constructed messages.
              // See bug #4492
              // inBody = NO;
              if (css)
                [self _finishCSS];
            }
          else
            {
              //NSLog (@"%@", _localName);
              [result appendFormat: @"</%@>", _localName];
            }
        }
    }
}

- (void) characters: (unichar *) _chars
             length: (NSUInteger) _len
{
  showWhoWeAre();
  if (!ignoredContent)
    {
      if (inStyle)
        [self _appendStyle: _chars length: _len];
      else if (inBody)
        {
	  NSString *s;
  
          s = [NSString stringWithCharacters: _chars length: _len];

	  // HACK: This is to avoid appending the useless junk in the <html> tag
	  //       that Outlook adds. It seems to confuse the XML parser for
	  //       forwarded messages as we get this in the _body_ of the email
	  //       while we really aren't in it!
	  if (![s hasPrefix: @" xmlns:v=\"urn:schemas-microsoft-com:vml\""])
	    [result appendString: [s stringByEscapingHTMLString]];
        }
    }
}

- (void) ignorableWhitespace: (unichar *) _chars
                      length: (NSUInteger) _len
{
  showWhoWeAre();
}

- (void) processingInstruction: (NSString *) _pi
                          data: (NSString *) _data
{
  showWhoWeAre();
}

- (void) setDocumentLocator: (id <NSObject, SaxLocator>) _locator
{
  showWhoWeAre();
}

- (void) skippedEntity: (NSString *) _entityName
{
  showWhoWeAre();
}

/* SaxLexicalHandler */
- (void) comment: (unichar *) _chars
          length: (int) _len
{
  showWhoWeAre();
  if (inStyle)
    [self _appendStyle: _chars length: _len];
}

- (void) startDTD: (NSString *) _name
         publicId: (NSString *) _pub
         systemId: (NSString *) _sys
{
  showWhoWeAre();
}

- (void) endDTD
{
  showWhoWeAre();
}

- (void) startEntity: (NSString *) _name
{
  showWhoWeAre();
}

- (void) endEntity: (NSString *) _name
{
  showWhoWeAre();
}

- (void) startCDATA
{
  showWhoWeAre();
}

- (void) endCDATA
{
  showWhoWeAre();
}

@end

@interface NSDictionary (SOGoDebug)

- (void) dump;

@end

@implementation NSDictionary (SOGoDebug)

- (void) dump
{
  NSEnumerator *keys;
  NSString *key;
  NSMutableString *dump;

  dump = [NSMutableString new];
  [dump appendFormat: @"\nNSDictionary dump (%@):\n", self];
  keys = [[self allKeys] objectEnumerator];
  key = [keys nextObject];
  while (key)
    {
      [dump appendFormat: @"%@: %@\n", key, [self objectForKey: key]];
      key = [keys nextObject];
    }
  [dump appendFormat: @"--- end ---\n"];

  NSLog(@"%@", dump);
  [dump release];
}

@end

@implementation UIxMailPartHTMLViewer

- (id) init
{
  if ((self = [super init]))
    {
      handler = nil;
    }

  return self;
}

- (void) dealloc
{
  [handler release];
  [super dealloc];
}

- (xmlCharEncoding) _xmlCharEncoding
{
  NSString *charset;

  charset = [[bodyInfo objectForKey:@"parameterList"]
	      objectForKey: @"charset"];
  if (![charset length])
    charset = @"us-ascii";

  return _xmlCharsetForCharset([charset lowercaseString]);
}

- (void) _parseContent
{
  NSObject <SaxXMLReader> *parser;
  NSData *preparsedContent;
  NSMutableData *htmlContent;
  NSString *s;

  xmlCharEncoding enc;

  if ([[self decodedFlatContent] isKindOfClass: [NGMimeBodyPart class]])
    preparsedContent = [[[self decodedFlatContent] body] sanitizedContentUsingVoidTags: VoidTags];
  else
    preparsedContent = [[self decodedFlatContent] sanitizedContentUsingVoidTags: VoidTags];

  parser = [[SaxXMLReaderFactory standardXMLReaderFactory]
             createXMLReaderForMimeType: @"text/html"];

  handler = [_UIxHTMLMailContentHandler new];
  [handler setAttachmentIds: attachmentIds];

  // Some broken email messages have some additionnal content outside the main HTML tags which are
  // ignored by libxml.
  // We surround the whole part with additional HTML tags to render all content.
  htmlContent = [NSMutableData dataWithBytes: "<html>" length: 6];
  [htmlContent appendData: preparsedContent];
  [htmlContent appendBytes: "</html>" length: 7];
  preparsedContent = (NSData *)htmlContent;

  // We check if we got an unsupported charset. If so
  // we convert everything to UTF-16{LE,BE} so it passes
  // in libxml2 and also in characters: length: defined
  // in this file (that expects unichar:s)
  enc = [self _xmlCharEncoding];
  if (enc == XML_CHAR_ENCODING_ERROR)
    {
      s = [NSString stringWithData: preparsedContent
		    usingEncodingNamed: [[bodyInfo objectForKey:@"parameterList"]
					  objectForKey: @"charset"]];

      // In some rare cases (like #3276), we can get utterly broken email messages where
      // HTML parts are wrongly encoded. We try to fall back to UTF-8 if that happens and
      // if it still happens, we fall back to ISO-Latin-1.
      if (!s)
        {
          s = [[NSString alloc] initWithData: preparsedContent  encoding: NSUTF8StringEncoding];

          if (!s)
            s = [[NSString alloc] initWithData: preparsedContent  encoding: NSISOLatin1StringEncoding];

          AUTORELEASE(s);
        }

#if BYTE_ORDER == BIG_ENDIAN
      preparsedContent = [s dataUsingEncoding: NSUTF16BigEndianStringEncoding];
      enc = XML_CHAR_ENCODING_UTF16BE;
#else
      preparsedContent = [s dataUsingEncoding: NSUTF16LittleEndianStringEncoding];
      enc = XML_CHAR_ENCODING_UTF16LE;
#endif
    }

  // Let's sanitize the string to make sure libxml doesn't go havoc
  if (enc == XML_CHAR_ENCODING_UTF8)
    {
      s = [[NSString alloc] initWithData: preparsedContent  encoding: NSUTF8StringEncoding];

      // Again, In some rare cases (like #4513), we can get utterly broken email messages where
      // HTML parts are wrongly encoded. We try to fall back to UTF-8 if that happens and
      // if it still happens, we fall back to ISO-Latin-1.
      if (!s)
        s = [[NSString alloc] initWithData: preparsedContent  encoding: NSISOLatin1StringEncoding];

      preparsedContent = [[s safeString] dataUsingEncoding: NSUTF8StringEncoding];
      RELEASE(s);
    }

  [handler setContentEncoding: enc];

  [parser setContentHandler: handler];
  [parser parseFromSource: preparsedContent];
}

- (NSString *) cssContent
{
  NSString *cssContent, *css;

  if (!handler)
    [self _parseContent];

  css = [handler css];
  if ([css length])
    cssContent
      = [NSString stringWithFormat: @"<style type=\"text/css\">%@</style>",
		  [handler css]];
  else
    cssContent = @"";

  return cssContent;
}

- (NSString *) flatContentAsString
{
  if (!handler)
    [self _parseContent];
      
  return [handler result];
}

@end

@implementation UIxMailPartExternalHTMLViewer

- (id) init
{
  if ((self = [super init]))
    {
      handler = nil;
    }

  return self;
}

- (void) dealloc
{
  [handler release];
  [super dealloc];
}

- (xmlCharEncoding) _xmlCharEncoding
{
  NSString *charset;

  charset = [[bodyInfo objectForKey:@"parameterList"]
	      objectForKey: @"charset"];
  if (![charset length])
    charset = @"us-ascii";

  return _xmlCharsetForCharset([charset lowercaseString]);
}

- (void) _parseContent
{
  NSObject <SaxXMLReader> *parser;
  NSData *preparsedContent;
  SOGoMailBodyPart *part;
  NSString *encoding;
  xmlCharEncoding enc;

  parser = [[SaxXMLReaderFactory standardXMLReaderFactory]
             createXMLReaderForMimeType: @"text/html"];

  if ([[self decodedFlatContent] isKindOfClass: [NGMimeBodyPart class]])
    {
      preparsedContent = [[[self decodedFlatContent] body] sanitizedContentUsingVoidTags: VoidTags];
      encoding = [[[self decodedFlatContent] contentType] valueOfParameter: @"charset"];
    }
  else
    {
      part = [self clientObject];
      preparsedContent = [[part fetchBLOB] sanitizedContentUsingVoidTags: VoidTags];
      encoding = [[part partInfo] valueForKey: @"encoding"];
    }

  if (![encoding length])
    encoding = @"us-ascii";

  handler = [_UIxHTMLMailContentHandler new];
  [handler setAttachmentIds: attachmentIds];

  // We check if we got an unsupported charset. If so
  // we convert everything to UTF-16{LE,BE} so it passes
  // in libxml2 and also in characters: length: defined
  // in this file (that expects unichar:s)
  enc = _xmlCharsetForCharset(encoding);
  if (enc == XML_CHAR_ENCODING_ERROR)
    {
      NSString *s;

      s = [NSString stringWithData: preparsedContent
		    usingEncodingNamed: [[bodyInfo objectForKey:@"parameterList"]
					  objectForKey: @"charset"]];
      
#if BYTE_ORDER == BIG_ENDIAN
      preparsedContent = [s dataUsingEncoding: NSUTF16BigEndianStringEncoding];
      enc = XML_CHAR_ENCODING_UTF16BE;
#else
      preparsedContent = [s dataUsingEncoding: NSUTF16LittleEndianStringEncoding];
      enc = XML_CHAR_ENCODING_UTF16LE;
#endif
    }

  [handler setContentEncoding: enc];
  [parser setContentHandler: handler];
  [parser parseFromSource: preparsedContent];
}

- (NSString *) filename
{
  return [[self clientObject] filename];
}

- (NSString *) cssContent
{
  NSString *cssContent, *css;

  if (!handler)
    [self _parseContent];

  css = [handler css];
  if ([css length])
    cssContent
      = [NSString stringWithFormat: @"<style type=\"text/css\">%@</style>",
		  [handler css]];
  else
    cssContent = @"";

  return cssContent;
}

- (NSString *) flatContentAsString
{
  if (!handler)
    [self _parseContent];

  return [handler result];
}

@end
