# --
# Copyright (C) 2001-2021 OTRS AG, https://otrs.com/
# Copyright (C) 2021 Znuny GmbH, https://znuny.org/
# --
# This software comes with ABSOLUTELY NO WARRANTY. For details, see
# the enclosed file COPYING for license information (GPL). If you
# did not receive this file, see https://www.gnu.org/licenses/gpl-3.0.txt.
# --

package Kernel::System::HTMLUtils;

use strict;
use warnings;

use utf8;

use MIME::Base64;

use Kernel::System::VariableCheck qw(:all);

our @ObjectDependencies = (
    'Kernel::Config',
    'Kernel::System::Encode',
    'Kernel::System::Log',
    'Kernel::System::Cache',
    'Kernel::System::HTMLUtils',
    'Kernel::System::Loader',
    'Kernel::System::Main'
);

=head1 NAME

Kernel::System::HTMLUtils - creating and modifying html strings

=head1 DESCRIPTION

A module for creating and modifying html strings.

=head1 PUBLIC INTERFACE

=head2 new()

Don't use the constructor directly, use the ObjectManager instead:

    my $HTMLUtilsObject = $Kernel::OM->Get('Kernel::System::HTMLUtils');

=cut

sub new {
    my ( $Type, %Param ) = @_;

    # allocate new hash for object
    my $Self = {};
    bless( $Self, $Type );

    # Helper function to construct regexes
    my $String2HTMLRE = sub {

        # Split text into characters and turn it into a series of alternations where each
        # matches either the character or its possible numerical enity encodings. Return
        # the RE joined back together as a string.
        return join( '', map { sprintf( '(?:%s|&\#0*%d;?|&\#x0*%x;?)', $_, ord, ord ) } split //, shift );
    };

    # TODO: it would be even faster to do this at compile time and have it as readonly class data
    $Self->{JavaScriptPrefixRegex} = $String2HTMLRE->('javascript');
    $Self->{ExpressionPrefixRegex} = $String2HTMLRE->('expression');

    # get debug level from parent
    $Self->{Debug} = $Param{Debug} || 0;

    return $Self;
}

=head2 ToAscii()

convert an HTML string to an ASCII string

    my $Ascii = $HTMLUtilsObject->ToAscii( String => $String );

=cut

sub ToAscii {
    my ( $Self, %Param ) = @_;

    # check needed stuff
    for my $Needed (qw(String)) {
        if ( !defined $Param{$Needed} ) {
            $Kernel::OM->Get('Kernel::System::Log')->Log(
                Priority => 'error',
                Message  => "Need $Needed!"
            );
            return;
        }
    }

    # make sure to flag the input string as unicode (utf8) because replacements below can
    # introduce unicode encoded characters (see bug#10970, bug#11596 and bug#12097 for more info)
    $Kernel::OM->Get('Kernel::System::Encode')->EncodeInput( \$Param{String} );

    # get length of line for forcing line breakes
    my $LineLength = $Kernel::OM->Get('Kernel::Config')->Get('Ticket::Frontend::TextAreaNote') || 78;

    # find <a href=....> and replace it with [x]
    my $LinkList = '';
    my $Counter  = 0;
    $Param{String} =~ s{
        <a\s.*?href=("|')(.*?)(\1).*?>
    }
    {
        my $Link = $2;

        my %SafeLink = $Kernel::OM->Get('Kernel::System::HTMLUtils')->Safety(
            String       => $Link,
            NoApplet     => 1,
            NoObject     => 1,
            NoEmbed      => 1,
            NoSVG        => 1,
            NoImg        => 1,
            NoIntSrcLoad => 1,
            NoExtSrcLoad => 1,
            NoJavaScript => 1,
        );

        $Link = $SafeLink{String} // '';

        $Counter++;
        $LinkList .= "[$Counter] $Link\n";
        "[$Counter]";
    }egxi;

    # pre-process <blockquote> and <div style=\"cite\"
    my %Cite;
    $Counter = 0;
    $Param{String} =~ s{
        <blockquote(.*?)>(.+?)</blockquote>
    }
    {
        my $Ascii = $Self->ToAscii(
            String => $2,
        );
        # force line breaking
        if ( length $Ascii > $LineLength ) {
            $Ascii =~ s/(.{4,$LineLength})(?:\s|\z)/$1\n/gm;
        }
        $Ascii =~ s/^(.*?)$/> $1/gm;
        $Counter++;
        my $Key     = "######Cite::$Counter######";
        $Cite{$Key} = $Ascii;
        $Key;
    }segxmi;
    $Param{String} =~ s{
        <div[^>]+type="cite"[^>]*>(.+?)</div>
    }
    {
        my $Ascii = $Self->ToAscii(
            String => $1,
        );
        # force line breaking
        if ( length $Ascii > $LineLength ) {
            $Ascii =~ s/(.{4,$LineLength})(?:\s|\z)/$1\n/gm;
        }
        $Ascii =~ s/^(.*?)$/> $1/gm;
        $Counter++;
        my $Key     = "######Cite::$Counter######";
        $Cite{$Key} = $Ascii;
        $Key;
    }segxmi;

    # remember <pre> and <code> tags
    my %One2One;
    $Counter = 0;
    $Param{String} =~ s{
        <(pre|code)(.*?)>(.+?)</(pre|code)(.*?)>
    }
    {
        my $Content = $3;
        $Counter++;
        my $Key        = "######One2One::$Counter######";
        $One2One{$Key} = $Content;
        $Key;
    }segxmi;

    # remove comments at the first place to avoid to much work
    # for the regex engine
    $Param{String} =~ s{<!-- .*? -->}{}xmgsi;

    # fix some bad stuff from opera and others
    $Param{String} =~ s/(\n\r|\r\r\n|\r\n)/\n/gs;

    # remove style tags
    $Param{String} =~ s{<style [^>]*? />}{}xgsi;
    $Param{String} =~ s{<style [^>]*? > .*? </style[^>]*>}{}xgsi;

    # remove br tags with new line before removing br without new line
    $Param{String} =~ s/\<br(\s{0,3}|\s{1,3}.+?)(\/|)\>[\r\n]?/\n/gsi;

    # remove <br>,<br/>,<br />, <br class="name"/>, tags and replace it with \n
    $Param{String} =~ s/\<br(\s{0,3}|\s{1,3}.+?)(\/|)\>/\n/gsi;

    # remove closing div tags, newline and replace it with \n
    $Param{String} =~ s/<\/(\s{0,3})div>[\r\n]?/\n/gsi;

    # remove opening div tags and replace it with space
    $Param{String} =~ s/<(\s{0,3})div>/ /gsi;

    # remove closing hr tags, newline and replace it with \n
    $Param{String} =~ s/\<(\/)(hr|hr.+?)\>[\r\n]?/\n/gsi;

    # remove opening hr tags and replace it with space
    $Param{String} =~ s/\<(hr|hr.+?)\>/ /gsi;

    # remove closing p, table tags, newline and replace it with \n
    $Param{String} =~ s/\<(\/)(p|p.+?|table|table.+?)\>[\r\n]?/\n/gsi;

    # remove opening p, table tags and replace it with space
    $Param{String} =~ s/\<(\/|)(p|p.+?|table|table.+?)\>/ /gsi;

    # remove closing tr, th tags, newline and replace them with \n
    $Param{String} =~ s/\<(\/)(tr|tr.+?|th|th.+?)\>[\r\n]?/\n/gsi;

    # remove opening tr, th tags and replace them with space
    $Param{String} =~ s/\<(tr|tr.+?|th|th.+?)\>/ /gsi;

    # remember <pre> and <code> tags and replace it
    for my $Key ( sort keys %One2One ) {
        $Param{String} =~ s/$Key/\n\n\n$One2One{$Key}\n\n/g;
    }

    # strip most other other tags beside </ul>, </ol>, </td>, <li>
    $Param{String} =~ s/(?!(?:<(?:(?:\/(?:ul|ol|td))|li)>))<.+?\>//gs;

    # clean string
    $Param{String} =~ s/^[ ]//gm;    # spaces are needed only between text, remove anything from the start

    $Param{String} =~ s/^\s*\n\s*\n/\n/mg;

    $Param{String} =~ s/^[\r\n]//s;

    # convert li tags to \n -
    $Param{String} =~ s/\<li\>/\n - /gsi;

    # convert </ul> and </ol> tags to \n\n
    $Param{String} =~ s/\<\/(ul|ol)\>/\n\n/gsi;

    # remove </td> tags and replace them with " "
    $Param{String} =~ s/<\/td[^>]*>/ /gsi;

    # replace multiple spaces with just one space
    $Param{String} =~ s/[ ]{2,}/ /mg;

    # replace the rest of selectors
    $Param{String} =~ s/\<\/{0,1}(ul|ol|li|td)?\><.+?\>//gs;

    # html encode based on cpan's HTML::Entities v1.35
    my %Entity = (

        # Some normal chars that have special meaning in SGML context
        amp  => '&',    # ampersand
        'gt' => '>',    # greater than
        'lt' => '<',    # less than
        quot => '"',    # double quote
        apos => "'",    # single quote

        # PUBLIC ISO 8879-1986//ENTITIES Added Latin 1//EN//HTML
        AElig  => chr(198),    # capital AE diphthong (ligature)
        Aacute => chr(193),    # capital A, acute accent
        Acirc  => chr(194),    # capital A, circumflex accent
        Agrave => chr(192),    # capital A, grave accent
        Aring  => chr(197),    # capital A, ring
        Atilde => chr(195),    # capital A, tilde
        Auml   => chr(196),    # capital A, dieresis or umlaut mark
        Ccedil => chr(199),    # capital C, cedilla
        ETH    => chr(208),    # capital Eth, Icelandic
        Eacute => chr(201),    # capital E, acute accent
        Ecirc  => chr(202),    # capital E, circumflex accent
        Egrave => chr(200),    # capital E, grave accent
        Euml   => chr(203),    # capital E, dieresis or umlaut mark
        Iacute => chr(205),    # capital I, acute accent
        Icirc  => chr(206),    # capital I, circumflex accent
        Igrave => chr(204),    # capital I, grave accent
        Iuml   => chr(207),    # capital I, dieresis or umlaut mark
        Ntilde => chr(209),    # capital N, tilde
        Oacute => chr(211),    # capital O, acute accent
        Ocirc  => chr(212),    # capital O, circumflex accent
        Ograve => chr(210),    # capital O, grave accent
        Oslash => chr(216),    # capital O, slash
        Otilde => chr(213),    # capital O, tilde
        Ouml   => chr(214),    # capital O, dieresis or umlaut mark
        THORN  => chr(222),    # capital THORN, Icelandic
        Uacute => chr(218),    # capital U, acute accent
        Ucirc  => chr(219),    # capital U, circumflex accent
        Ugrave => chr(217),    # capital U, grave accent
        Uuml   => chr(220),    # capital U, dieresis or umlaut mark
        Yacute => chr(221),    # capital Y, acute accent
        aacute => chr(225),    # small a, acute accent
        acirc  => chr(226),    # small a, circumflex accent
        aelig  => chr(230),    # small ae diphthong (ligature)
        agrave => chr(224),    # small a, grave accent
        aring  => chr(229),    # small a, ring
        atilde => chr(227),    # small a, tilde
        auml   => chr(228),    # small a, dieresis or umlaut mark
        ccedil => chr(231),    # small c, cedilla
        eacute => chr(233),    # small e, acute accent
        ecirc  => chr(234),    # small e, circumflex accent
        egrave => chr(232),    # small e, grave accent
        eth    => chr(240),    # small eth, Icelandic
        euml   => chr(235),    # small e, dieresis or umlaut mark
        iacute => chr(237),    # small i, acute accent
        icirc  => chr(238),    # small i, circumflex accent
        igrave => chr(236),    # small i, grave accent
        iuml   => chr(239),    # small i, dieresis or umlaut mark
        ntilde => chr(241),    # small n, tilde
        oacute => chr(243),    # small o, acute accent
        ocirc  => chr(244),    # small o, circumflex accent
        ograve => chr(242),    # small o, grave accent
        oslash => chr(248),    # small o, slash
        otilde => chr(245),    # small o, tilde
        ouml   => chr(246),    # small o, dieresis or umlaut mark
        szlig  => chr(223),    # small sharp s, German (sz ligature)
        thorn  => chr(254),    # small thorn, Icelandic
        uacute => chr(250),    # small u, acute accent
        ucirc  => chr(251),    # small u, circumflex accent
        ugrave => chr(249),    # small u, grave accent
        uuml   => chr(252),    # small u, dieresis or umlaut mark
        yacute => chr(253),    # small y, acute accent
        yuml   => chr(255),    # small y, dieresis or umlaut mark

        # Some extra Latin 1 chars that are listed in the HTML3.2 draft (21-May-96)
        copy => chr(169),      # copyright sign
        reg  => chr(174),      # registered sign
        nbsp => chr(160),      # non breaking space

        # Additional ISO-8859/1 entities listed in rfc1866 (section 14)
        iexcl   => chr(161),
        cent    => chr(162),
        pound   => chr(163),
        curren  => chr(164),
        yen     => chr(165),
        brvbar  => chr(166),
        sect    => chr(167),
        uml     => chr(168),
        ordf    => chr(170),
        laquo   => chr(171),
        'not'   => chr(172),    # not is a keyword in perl
        shy     => chr(173),
        macr    => chr(175),
        deg     => chr(176),
        plusmn  => chr(177),
        sup1    => chr(185),
        sup2    => chr(178),
        sup3    => chr(179),
        acute   => chr(180),
        micro   => chr(181),
        para    => chr(182),
        middot  => chr(183),
        cedil   => chr(184),
        ordm    => chr(186),
        raquo   => chr(187),
        frac14  => chr(188),
        frac12  => chr(189),
        frac34  => chr(190),
        iquest  => chr(191),
        'times' => chr(215),    # times is a keyword in perl
        divide  => chr(247),

        (
            $] > 5.007
            ? (
                OElig    => chr(338),
                oelig    => chr(339),
                Scaron   => chr(352),
                scaron   => chr(353),
                Yuml     => chr(376),
                fnof     => chr(402),
                circ     => chr(710),
                tilde    => chr(732),
                Alpha    => chr(913),
                Beta     => chr(914),
                Gamma    => chr(915),
                Delta    => chr(916),
                Epsilon  => chr(917),
                Zeta     => chr(918),
                Eta      => chr(919),
                Theta    => chr(920),
                Iota     => chr(921),
                Kappa    => chr(922),
                Lambda   => chr(923),
                Mu       => chr(924),
                Nu       => chr(925),
                Xi       => chr(926),
                Omicron  => chr(927),
                Pi       => chr(928),
                Rho      => chr(929),
                Sigma    => chr(931),
                Tau      => chr(932),
                Upsilon  => chr(933),
                Phi      => chr(934),
                Chi      => chr(935),
                Psi      => chr(936),
                Omega    => chr(937),
                alpha    => chr(945),
                beta     => chr(946),
                gamma    => chr(947),
                delta    => chr(948),
                epsilon  => chr(949),
                zeta     => chr(950),
                eta      => chr(951),
                theta    => chr(952),
                iota     => chr(953),
                kappa    => chr(954),
                lambda   => chr(955),
                mu       => chr(956),
                nu       => chr(957),
                xi       => chr(958),
                omicron  => chr(959),
                pi       => chr(960),
                rho      => chr(961),
                sigmaf   => chr(962),
                sigma    => chr(963),
                tau      => chr(964),
                upsilon  => chr(965),
                phi      => chr(966),
                chi      => chr(967),
                psi      => chr(968),
                omega    => chr(969),
                thetasym => chr(977),
                upsih    => chr(978),
                piv      => chr(982),
                ensp     => chr(8194),
                emsp     => chr(8195),
                thinsp   => chr(8201),
                zwnj     => chr(8204),
                zwj      => chr(8205),
                lrm      => chr(8206),
                rlm      => chr(8207),
                ndash    => chr(8211),
                mdash    => chr(8212),
                lsquo    => chr(8216),
                rsquo    => chr(8217),
                sbquo    => chr(8218),
                ldquo    => chr(8220),
                rdquo    => chr(8221),
                bdquo    => chr(8222),
                dagger   => chr(8224),
                Dagger   => chr(8225),
                bull     => chr(8226),
                hellip   => chr(8230),
                permil   => chr(8240),
                prime    => chr(8242),
                Prime    => chr(8243),
                lsaquo   => chr(8249),
                rsaquo   => chr(8250),
                oline    => chr(8254),
                frasl    => chr(8260),
                euro     => chr(8364),
                image    => chr(8465),
                weierp   => chr(8472),
                real     => chr(8476),
                trade    => chr(8482),
                alefsym  => chr(8501),
                larr     => chr(8592),
                uarr     => chr(8593),
                rarr     => chr(8594),
                darr     => chr(8595),
                harr     => chr(8596),
                crarr    => chr(8629),
                lArr     => chr(8656),
                uArr     => chr(8657),
                rArr     => chr(8658),
                dArr     => chr(8659),
                hArr     => chr(8660),
                forall   => chr(8704),
                part     => chr(8706),
                exist    => chr(8707),
                empty    => chr(8709),
                nabla    => chr(8711),
                isin     => chr(8712),
                notin    => chr(8713),
                ni       => chr(8715),
                prod     => chr(8719),
                sum      => chr(8721),
                minus    => chr(8722),
                lowast   => chr(8727),
                radic    => chr(8730),
                prop     => chr(8733),
                infin    => chr(8734),
                ang      => chr(8736),
                'and'    => chr(8743),
                'or'     => chr(8744),
                cap      => chr(8745),
                cup      => chr(8746),
                'int'    => chr(8747),
                there4   => chr(8756),
                sim      => chr(8764),
                cong     => chr(8773),
                asymp    => chr(8776),
                'ne'     => chr(8800),
                equiv    => chr(8801),
                'le'     => chr(8804),
                'ge'     => chr(8805),
                'sub'    => chr(8834),
                sup      => chr(8835),
                nsub     => chr(8836),
                sube     => chr(8838),
                supe     => chr(8839),
                oplus    => chr(8853),
                otimes   => chr(8855),
                perp     => chr(8869),
                sdot     => chr(8901),
                lceil    => chr(8968),
                rceil    => chr(8969),
                lfloor   => chr(8970),
                rfloor   => chr(8971),
                lang     => chr(9001),
                rang     => chr(9002),
                loz      => chr(9674),
                spades   => chr(9824),
                clubs    => chr(9827),
                hearts   => chr(9829),
                diams    => chr(9830),
                )
            : ()
        )
    );

    # encode html entities like "&#8211;"
    $Param{String} =~ s{
        (&\#(\d+);?)
    }
    {
        my $ChrOrig = $1;
        my $Dec = $2;

        # Don't process UTF-16 surrogate pairs. Used on their own, these are not valid UTF-8 code
        # points and can result in errors in old Perl versions. See bug#12588 for more information.
        # - High Surrogate codes (U+D800-U+DBFF)
        # - Low Surrogate codes (U+DC00-U+DFFF)
        if ( $Dec >= 55296 && $Dec <= 57343 ) {
            $ChrOrig;
        }
        else {
            my $Chr = chr($Dec);

            # Make sure we get valid UTF8 code points, but skip characters from 128 to 255
            #   (inclusive), since they are by default internally not encoded as UTF-8 for
            #   backward compatibility reasons. See bug#12457 for more information.
            if ( $Dec < 128 || $Dec> 255 ) {
                Encode::_utf8_off($Chr);
                $Chr = Encode::decode('utf-8', $Chr, 0);
            }

            if ( $Chr ) {
                $Chr;
            }
            else {
                $ChrOrig;
            }
        }
    }egx;

    # encode html entities like "&#x3d;"
    $Param{String} =~ s{
        (&\#[xX]([0-9a-fA-F]+);?)
    }
    {
        my $ChrOrig = $1;
        my $Dec = hex( $2 );

        # Don't process UTF-16 surrogate pairs. Used on their own, these are not valid UTF-8 code
        # points and can result in errors in old Perl versions. See bug#12588 for more information.
        # - High Surrogate codes (U+D800-U+DBFF)
        # - Low Surrogate codes (U+DC00-U+DFFF)
        if ( $Dec >= 55296 && $Dec <= 57343 ) {
            $ChrOrig;
        }
        else {
            if ( $Dec ) {
                my $Chr = chr( $Dec );

                # Make sure we get valid UTF8 code points, but skip characters from 128 to 255
                #   (inclusive), since they are by default internally not encoded as UTF-8 for
                #   backward compatibility reasons. See bug#12457 for more information.
                if ( $Dec < 128 || $Dec > 255 ) {
                    Encode::_utf8_off($Chr);
                    $Chr = Encode::decode('utf-8', $Chr, 0);
                }

                if ( $Chr ) {
                    $Chr;
                }
                else {
                    $ChrOrig;
                }
            }
            else {
                $ChrOrig;
            }
        }
    }egx;

    # encode html entities like "&amp;"
    $Param{String} =~ s{
        (&(\w+);?)
    }
    {
        if ( $Entity{$2} ) {
            $Entity{$2};
        }
        else {
            $1;
        }
    }egx;

    # remove empty lines
    $Param{String} =~ s/^\s*\n\s*\n/\n/mgaa;

    # force line breaking
    if ( length $Param{String} > $LineLength ) {
        $Param{String} =~ s/(.{4,$LineLength})(?:\s|\z)/$1\n/gm;
    }

    # remember <blockquote> and <div style=\"cite\"
    for my $Key ( sort keys %Cite ) {
        $Param{String} =~ s/$Key/$Cite{$Key}\n/g;
    }

    # add extracted links
    if ($LinkList) {
        $Param{String} .= "\n\n" . $LinkList;
    }

    return $Param{String};
}

=head2 ToHTML()

convert an ASCII string to an HTML string

    my $HTMLString = $HTMLUtilsObject->ToHTML(
        String                     => $String,
        ReplaceDoubleSpace         => 0,       # replace &nbsp;&nbsp; with "  ", optional 1 or 0 (defaults to 1)
        DoNotReplaceWithParagraphs => 0,       # this is additional feature required due to CKEditor 5 using
                                               # rule of paragraphs being the "core" selector
                                               # inside it's text data
                                                # do not replace end of lines with paragraphs
                                                # usually used to parse string (for example for template)
                                                # before fixing paragrapth for ckeditor 5
                                                # IMPORTANT!
                                                # if enabled, then after string processing you need
                                                # to execute "ToHTMLFixHardBreaks" function!
    );

=cut

sub ToHTML {
    my ( $Self, %Param ) = @_;

    # check needed stuff
    for my $Needed (qw(String)) {
        if ( !defined $Param{$Needed} ) {
            $Kernel::OM->Get('Kernel::System::Log')->Log(
                Priority => 'error',
                Message  => "Need $Needed!"
            );
            return;
        }
    }

    # fix some bad stuff from opera and others
    $Param{String} =~ s/(\n\r|\r\r\n|\r\n)/\n/gs;

    $Param{String} =~ s/</&lt;/g;
    $Param{String} =~ s/>/&gt;/g;
    $Param{String} =~ s/"/&quot;/g;

    $Param{String} = $Self->ToHTMLReplaceWithParagraphs(
        String => $Param{String},
    ) if ( !$Param{DoNotReplaceWithParagraphs} );

    $Param{String} =~ s/  /&nbsp;&nbsp;/g if $Param{ReplaceDoubleSpace};

    return $Param{String};
}

=head2 ToHTMLReplaceWithParagraphs()

replace & fix hard breaks/paragraphs for ckeditor 5

    my $HTMLString = $HTMLUtilsObject->ToHTMLReplaceWithParagraphs(
        String => $String,
    );

=cut

sub ToHTMLReplaceWithParagraphs {
    my ( $Self, %Param ) = @_;

    # check needed stuff
    for my $Needed (qw(String)) {
        if ( !defined $Param{$Needed} ) {
            $Kernel::OM->Get('Kernel::System::Log')->Log(
                Priority => 'error',
                Message  => "Need $Needed!"
            );
            return;
        }
    }

    if ( $Param{String} =~ s/^(?!.*(?:\[%.*?%\]))(?!.*(?:<p>.*<\/p>))(.*?)([\r\n])/<p>$1<\/p>$2/gm ) {
        $Param{String} =~ s/(<\/p>([\r\n])){1}(?!<p>)(.+)/$1<p>$3<\/p>/sm;
    }
    $Param{String} =~ s/^(?=.*\[%.*?%\])(.*?)([\r\n])/$1$2<p><\/p>$2/gm;

    return $Param{String};
}

=head2 RTEContentCssDefaultFromSysconfigGet()

get RTE css content styles from system configuration

    my $RTEContentCssDefault = $HTMLUtilsObject->RTEContentCssDefaultFromSysconfigGet();

=cut

sub RTEContentCssDefaultFromSysconfigGet {
    my ( $Self, %Param ) = @_;

    my $ConfigObject = $Kernel::OM->Get('Kernel::Config');

    # get default content CSS
    my $DefaultCSS = $ConfigObject->Get('Frontend::RichText::CSS::Content::Default') // '';

    # escape special characters like double-quotes, e.g. used in font names with spaces
    $DefaultCSS = $Self->ToHTML( String => $DefaultCSS ) if $DefaultCSS;
    $DefaultCSS = ".ck.ck-content{$DefaultCSS}";

    return $DefaultCSS;
}

=head2 RTEContentCssInternalGet()

get internal RTE css content styles from path

    my $RTEContentCss = $HTMLUtilsObject->RTEContentCssInternalGet(
        UserType => 'Agent' # required
    );

=cut

sub RTEContentCssInternalGet {
    my ( $Self, %Param ) = @_;

    my $LogObject = $Kernel::OM->Get('Kernel::System::Log');

    NEEDED:
    for my $Needed (qw(UserType)) {

        next NEEDED if defined $Param{$Needed};

        $LogObject->Log(
            Priority => 'error',
            Message  => "Parameter '$Needed' is needed!",
        );
        return;
    }

    my $ConfigObject = $Kernel::OM->Get('Kernel::Config');
    my $CacheObject  = $Kernel::OM->Get('Kernel::System::Cache');
    my $MainObject   = $Kernel::OM->Get('Kernel::System::Main');
    my $LoaderObject = $Kernel::OM->Get('Kernel::System::Loader');

    my $Interface = $Param{UserType};

    # get content CSS using path to the files
    my $ContentCSSPath = $Interface eq 'Agent'
        ?
        $ConfigObject->Get('Frontend::RichText::CSS::Content::Path')
        :
        $ConfigObject->Get('Frontend::RichText::CSS::Content::Path::Customer');

    my $InternalArticleStylesPaths = $ContentCSSPath->{InternalArticleStyles};

    return if !IsArrayRefWithData($InternalArticleStylesPaths);

    @{$InternalArticleStylesPaths} = map {
        $ConfigObject->Get('Home') . '/var/httpd/htdocs/' . $_
    } @{$InternalArticleStylesPaths};

    my $RTEContentPrefix = 'MinifiedRTEContentStyles';

    my $TargetDirectory = $ConfigObject->Get('Home') . "/var/httpd/htdocs/skins/$Interface/default/css-cache/";

    # minify files only once if not changed
    my $ActualMinifiedFilename = $LoaderObject->MinifyFiles(
        List                 => $InternalArticleStylesPaths,
        Type                 => 'CSS',
        TargetDirectory      => $TargetDirectory,
        TargetFilenamePrefix => $RTEContentPrefix,
    );

    my $CachedMinifiedFilename = $CacheObject->Get(
        Type => 'HTMLUtils',
        Key  => "${RTEContentPrefix}_Filename_$Interface",
    ) // '';

    my $MinifiedRTEContentCSS;
    my $FilenameVersionMatch;

    my %Styles;

    # check for minification success
    if ($ActualMinifiedFilename) {

        # actual cached file found
        $FilenameVersionMatch = $ActualMinifiedFilename eq $CachedMinifiedFilename;

        $MinifiedRTEContentCSS = $CacheObject->Get(
            Type => 'HTMLUtils',
            Key  => "${RTEContentPrefix}_$Interface",
        ) || '' if $FilenameVersionMatch;

        if ( !$MinifiedRTEContentCSS ) {

            # minified content wasn't found
            # or cache expired
            # update filename modified
            $CacheObject->Set(
                Type  => 'HTMLUtils',
                Key   => "${RTEContentPrefix}_Filename_$Interface",
                Value => $ActualMinifiedFilename
            ) if !$FilenameVersionMatch;

            $MinifiedRTEContentCSS = $MainObject->FileRead(
                Location        => $TargetDirectory . '/' . $ActualMinifiedFilename,
                Type            => 'Local',
                DisableWarnings => 1,
            );

            # update cached content
            $CacheObject->Set(
                Type  => 'HTMLUtils',
                Key   => "${RTEContentPrefix}_$Interface",
                Value => $MinifiedRTEContentCSS,
            );

            # delete old cached file
            $MainObject->FileDelete(
                Location        => "$TargetDirectory/$CachedMinifiedFilename",
                Type            => 'Local',
                DisableWarnings => 1,
            ) if !$FilenameVersionMatch;
        }
    }
    else {
        $LogObject->Log(
            Priority => 'error',
            Message  => 'Error while minifying content css file!',
        );
    }

    # clean new lines that are still present
    # after minification of multiple files
    ${$MinifiedRTEContentCSS} =~ s/\n//g;

    return $MinifiedRTEContentCSS;
}

=head2 DocumentComplete()

check and e. g. add <html> and <body> tags to given html string

    my $HTMLDocument = $HTMLUtilsObject->DocumentComplete(
        String   => $String,  # required
        Charset  => $Charset, # required
        UserType => 'Agent'   # optional
    );

=cut

sub DocumentComplete {
    my ( $Self, %Param ) = @_;

    my $LogObject = $Kernel::OM->Get('Kernel::System::Log');

    # check needed stuff
    for my $Needed (qw(String Charset)) {
        if ( !defined $Param{$Needed} ) {
            $LogObject->Log(
                Priority => 'error',
                Message  => "Need $Needed!"
            );
            return;
        }
    }

    # get content CSS from sysconfig & file path
    my $RTEContentCssDefault      = $Self->RTEContentCssDefaultFromSysconfigGet() // '';
    my $RTEContentCssInternalData = $Self->RTEContentCssInternalGet(
        UserType => $Param{UserType} || 'Agent',
    );

    my $RTEContentCssInternal = '';
    if ( defined $RTEContentCssInternalData && ref $RTEContentCssInternalData eq 'SCALAR' ) {
        $RTEContentCssInternal = ${$RTEContentCssInternalData};
    }

    if ( $Param{String} =~ m{<html>}i ) {

        my $Styles = '<style class="RTEContentCssInternal">' . $RTEContentCssInternal . '</style>'
            . '<style class="RTEContentCssDefault">' . $RTEContentCssDefault . '</style>';

        if ( $Param{String} !~ m{<style class="(?:RTEContentCssInternal|RTEContentCssDefault)">} ) {
            $Param{String} =~ s{( <html> .*? <head> )( .*? )( <\/head> )}{$1$2$Styles$3}xs;
        }

        if ( $Param{String} !~ m{<body .*? class="ck ck-content">}x ) {
            $Param{String} =~ s{( <html> .*? <head>  .*?  <\/head> .*? <body)> }{$1 class="ck ck-content">}xs;
        }

        return $Param{String};
    }

    # Use the HTML5 doctype because it is compatible with HTML4 and causes the browsers
    # to render the content in standards mode, which is more safe than quirks mode.
    my $Body = '<!DOCTYPE html><html><head>';
    $Body .= '<meta http-equiv="Content-Type" content="text/html; charset=' . $Param{Charset} . '"/>';
    $Body .= '<style class="RTEContentCssInternal">' . $RTEContentCssInternal . '</style>';
    $Body .= '<style class="RTEContentCssDefault">' . $RTEContentCssDefault . '</style>';
    $Body .= '</head><body class="ck ck-content">' . $Param{String} . '</body></html>';

    return $Body;
}

=head2 DocumentStrip()

remove html document tags from string

    my $HTMLString = $HTMLUtilsObject->DocumentStrip(
        String  => $String,
    );

=cut

sub DocumentStrip {
    my ( $Self, %Param ) = @_;

    # check needed stuff
    for my $Needed (qw(String)) {
        if ( !defined $Param{$Needed} ) {
            $Kernel::OM->Get('Kernel::System::Log')->Log(
                Priority => 'error',
                Message  => "Need $Needed!"
            );
            return;
        }
    }

    $Param{String} =~ s/^<\!DOCTYPE\s+HTML.+?>//gsi;
    $Param{String} =~ s/<head>.+?<\/head>//gsi;
    $Param{String} =~ s/<(html|body)(.*?)>//gsi;
    $Param{String} =~ s/<\/(html|body)>//gsi;

    return $Param{String};
}

=head2 DocumentCleanup()

perform some sanity checks on HTML content

 -  Replace <blockquote> by using
    "<div style="border:none;border-left:solid blue 1.5pt;padding:0cm 0cm 0cm 4.0pt" type="cite">"
    because of cross mail client and browser compatibility.

 -  If there is no HTML doctype present, inject the HTML5 doctype, because it is compatible with HTML4
    and causes the browsers to render the content in standards mode, which is safer.

    $HTMLBody = $HTMLUtilsObject->DocumentCleanup(
        String => $HTMLBody,
    );

=cut

sub DocumentCleanup {
    my ( $Self, %Param ) = @_;

    # check needed stuff
    for my $Needed (qw(String)) {
        if ( !defined $Param{$Needed} ) {
            $Kernel::OM->Get('Kernel::System::Log')->Log(
                Priority => 'error',
                Message  => "Need $Needed!"
            );
            return;
        }
    }

    # If the string starts with <html> directly, inject the doctype
    $Param{String} =~ s{ \A \s* <html }{<!DOCTYPE html><html}gsmix;

    # remove <base> tags - see bug#8880
    $Param{String} =~ s{<base .*?>}{}xmsi;

    # replace <blockquote> by using
    # "<div style="border:none;border-left:solid blue 1.5pt;padding:0cm 0cm 0cm 4.0pt" type="cite">"
    # because of cross mail client and browser compatibility
    my $Style = "border:none;border-left:solid blue 1.5pt;padding:0cm 0cm 0cm 4.0pt";
    for my $Index ( 1 .. 10 ) {
        $Param{String} =~ s{
            <blockquote(.*?)>(.+?)</blockquote>
        }
        {
            "<div $1 style=\"$Style\">$2</div>";
        }segxmi;
    }

    return $Param{String};
}

=head2 TruncateBodyQuote()

Strips document content to the limited number of lines.

    $Body = $HTMLUtilsObject->TruncateBodyQuote(
        Body       => $Body,
        Limit      => 10000,
        HTMLOutput => 1|0,
    );

=cut

sub TruncateBodyQuote {
    my ( $Self, %Param ) = @_;

    my $LogObject = $Kernel::OM->Get('Kernel::System::Log');

    NEEDED:
    for my $Needed (qw(Body Limit)) {
        next NEEDED if defined $Param{$Needed};

        $LogObject->Log(
            Priority => 'error',
            Message  => "Need $Needed!"
        );
        return;
    }

    # split body - one element per line
    my @Body = split "\n", $Param{Body};

    # only modify if body is longer than allowed
    return $Param{Body} if scalar @Body <= $Param{Limit};

    # splice to max. allowed lines and reassemble
    @Body = @Body[ 0 .. ( $Param{Limit} - 1 ) ];
    $Param{Body} = join "\n", @Body;

    if ( $Param{HTMLOutput} ) {
        $Param{Body} .= "\n<div class=\"LimitEnabledCharacters\"> [...]</div>";
    }
    else {
        $Param{Body} .= "\n[...]";
    }

    return $Param{Body};
}

=head2 LinkQuote()

detect links in HTML code, add C<a href> if missing

    my $HTMLWithLinks = $HTMLUtilsObject->LinkQuote(
        String    => $HTMLString,
        Target    => 'TargetName', # content of target="?", e. g. _blank
        TargetAdd => 1,            # add target="_blank" to all existing "<a href"
    );

also string ref is possible

    my $HTMLWithLinksRef = $HTMLUtilsObject->LinkQuote(
        String => \$HTMLStringRef,
    );

=cut

sub LinkQuote {
    my ( $Self, %Param ) = @_;

    my $String = $Param{String} || '';

    # check ref
    my $StringScalar;
    if ( !ref $String ) {
        $StringScalar = $String;
        $String       = \$StringScalar;

        # return if string is not a ref and it is empty
        return $StringScalar if !$StringScalar;
    }

    # add target to already existing url of html string
    if ( $Param{TargetAdd} ) {

        # find target
        my $Target = $Param{Target};
        if ( !$Target ) {
            $Target = '_blank';
        }

        # add target to existing "<a href"
        ${$String} =~ s{
            (<a\s{1,10})([^>]+)>
        }
        {
            my $Start = $1;
            my $Value = $2;
            if ( $Value !~ /href=/i || $Value =~ /target=/i ) {
                "$Start$Value>";
            }
            else {
                "$Start$Value target=\"$Target\">";
            }
        }egxsi;
    }

    my $Marker = "§" x 10;

    # Remove existing <a>...</a> tags and their content to be re-inserted later, this must not be quoted.
    # Also remove other tags to avoid quoting in tag parameters.
    my $Counter = 0;
    my %TagHash;
    ${$String} =~ s{
        (<a\s[^>]*?>[^>]*</a>|<[^>]+?>)
    }
    {
        my $Content = $1;
        my $Key     = "${Marker}TagHash-$Counter${Marker}";
        $TagHash{$Counter++} = $Content;
        $Key;
    }egxism;

    # Add <a> tags for URLs in the content.
    my $Target = '';
    if ( $Param{Target} ) {
        $Target = " target=\"$Param{Target}\"";
    }
    ${$String} =~ s{
        (                                          # $1 greater-than and less-than sign
            > | < | \s | §{10} |
            (?: &[a-zA-Z0-9]+; )                   # get html entities
        )
        (                                          # $2
            (?:                                    # http or only www
                (?: (?: http s? | ftp ) :\/\/) |   # http://,https:// and ftp://
                (?: (?: www | ftp ) \.)            # www. and ftp.
            )
        )
        (                                          # $3
            (?: [a-z0-9\-]+ \. )*                  # get subdomains, optional
            [a-z0-9\-]+                            # get top level domain
            (?:                                    # optional port number
                [:]
                [0-9]+
            )?
            (?:                                    # file path element
                [\/\.]
                | [a-zA-Z0-9\-_=%]
            )*
            (?:                                    # param string
                [\?]                               # if param string is there, "?" must be present
                [a-zA-Z0-9&;=%\-_:\.\/]*           # param string content, this will also catch entities like &amp;
            )?
            (?:                                    # link hash string
                [\#]                               #
                [a-zA-Z0-9&;=%\-_:\.\/]*           # hash string content, this will also catch entities like &amp;
            )?
        )
        (?=                                        # $4
            (?:
                [\?,;!\.\)] (?: \s | $ )           # \)\s this construct is because of bug# 2450
                | \"
                | \]
                | \s+
                | '
                | >                               # greater-than and less-than sign
                | <                               # "
                | (?: &[a-zA-Z0-9]+; )+            # html entities
                | $                                # bug# 2715
            )
            | §{10}                                # ending TagHash
        )
    }
    {
        my $Start    = $1;
        my $Protocol = $2;
        my $Link     = $3;
        my $End      = $4 || '';

        # there may different links for href and link body
        my $HrefLink;
        my $DisplayLink;

        if ( $Protocol =~ m{\A ( http | https | ftp ) : \/ \/ }xi ) {
            $DisplayLink = $Protocol . $Link;
            $HrefLink    = $DisplayLink;
        }
        else {
            if ($Protocol =~ m{\A ftp }smx ) {
                $HrefLink = 'ftp://';
            }
            else {
                $HrefLink = 'http://';
            }

            if ( $Protocol ) {
                $HrefLink   .= $Protocol;
                $DisplayLink = $Protocol;
            }

            $DisplayLink .= $Link;
            $HrefLink    .= $Link;
        }

        # remove trailing dots in href link
        if( $HrefLink =~ s{\.+\z}{} ){
            $DisplayLink =~ s{\.+\z}{};
            $End .= '.';
        }

        $Start . "<a href=\"$HrefLink\"$Target title=\"$HrefLink\">$DisplayLink<\/a>" . $End;
    }egxism;

    # Re-add previously removed tags.
    ${$String} =~ s{${Marker}TagHash-(\d+)${Marker}}{$TagHash{$1}}egsxim;

    # check ref && return result like called
    if ( defined $StringScalar ) {
        return ${$String};
    }
    return $String;
}

=head2 Safety()

To remove/strip active html tags/addons (JavaScript, C<applet>s, C<embed>s and C<object>s)
from html strings.

    my %Safe = $HTMLUtilsObject->Safety(
        String         => $HTMLString,
        NoApplet       => 1,
        NoObject       => 1,
        NoEmbed        => 1,
        NoSVG          => 1,
        NoImg          => 1,
        NoIntSrcLoad   => 0,
        NoExtSrcLoad   => 1,
        NoJavaScript   => 1,
        ReplacementStr => 'string',          # optional, string to show instead of applet, object, embed, svg and img tags
    );

also string ref is possible

    my %Safe = $HTMLUtilsObject->Safety(
        String       => \$HTMLStringRef,
        NoApplet     => 1,
        NoObject     => 1,
        NoEmbed      => 1,
        NoSVG        => 1,
        NoImg        => 1,
        NoIntSrcLoad => 0,
        NoExtSrcLoad => 1,
        NoJavaScript => 1,
    );

returns

    my %Safe = (
        String  => $HTMLString, # modified html string (scalar or ref)
        Replace => 1,           # info if something got replaced
    );

=cut

sub Safety {
    my ( $Self, %Param ) = @_;

    # check needed stuff
    for my $Needed (qw(String)) {
        if ( !defined $Param{$Needed} ) {
            $Kernel::OM->Get('Kernel::System::Log')->Log(
                Priority => 'error',
                Message  => "Need $Needed!"
            );
            return;
        }
    }

    my $String = $Param{String} // '';

    # check ref
    my $StringScalar;
    if ( !ref $String ) {
        $StringScalar = $String;
        $String       = \$StringScalar;
    }

    my %Safety;

    my $Replaced;

    # In UTF-7, < and > can be encoded to mask them from security filters like this one.
    my $TagStart = '(?:<|[+]ADw-)';
    my $TagEnd   = '(?:>|[+]AD4-)';

    # Replace as many times as it is needed to avoid nesting tag attacks.
    do {
        $Replaced = undef;

        # remove script tags
        if ( $Param{NoJavaScript} ) {
            $Replaced += ${$String} =~ s{
                $TagStart script.*? $TagEnd .*?  $TagStart /script \s* $TagEnd
            }
            {}sgxim;
            $Replaced += ${$String} =~ s{
                $TagStart script.*? $TagEnd .+? ($TagStart|$TagEnd)
            }
            {}sgxim;

            # remove style/javascript parts
            $Replaced += ${$String} =~ s{
                $TagStart style[^>]+? $Self->{JavaScriptPrefixRegex} (.+?|) $TagEnd (.*?) $TagStart /style \s* $TagEnd
            }
            {}sgxim;

            # remove MS CSS expressions (JavaScript embedded in CSS)
            ${$String} =~ s{
                ($TagStart style[^>]+? $TagEnd .*? $TagStart /style \s* $TagEnd)
            }
            {
                if ( index($1, 'expression(' ) > -1 ) {
                    $Replaced = 1;
                    '';
                }
                else {
                    $1;
                }
            }egsxim;
        }

        # remove HTTP redirects
        $Replaced += ${$String} =~ s{
            $TagStart meta [^>]+? http-equiv=('|"|)refresh [^>]+? $TagEnd
        }
        {}sgxim;

        my $ReplacementStr = $Param{ReplacementStr} // '';

        # remove <applet> tags
        if ( $Param{NoApplet} ) {
            $Replaced += ${$String} =~ s{
                $TagStart applet.*? $TagEnd (.*?) $TagStart /applet \s* $TagEnd
            }
            {$ReplacementStr}sgxim;
        }

        # remove <Object> tags
        if ( $Param{NoObject} ) {
            $Replaced += ${$String} =~ s{
                $TagStart object.*? $TagEnd (.*?) $TagStart /object \s* $TagEnd
            }
            {$ReplacementStr}sgxim;
        }

        # remove <svg> tags
        if ( $Param{NoSVG} ) {
            $Replaced += ${$String} =~ s{
                $TagStart svg.*? $TagEnd (.*?) $TagStart /svg \s* $TagEnd
            }
            {$ReplacementStr}sgxim;
        }

        # remove <img> tags
        if ( $Param{NoImg} ) {
            $Replaced += ${$String} =~ s{
                $TagStart img.*? (.*?) \s* $TagEnd
            }
            {$ReplacementStr}sgxim;
        }

        # remove <embed> tags
        if ( $Param{NoEmbed} ) {
            $Replaced += ${$String} =~ s{
                $TagStart embed.*? $TagEnd
            }
            {$ReplacementStr}sgxim;
        }

        # check each html tag
        ${$String} =~ s{
            ($TagStart.+?$TagEnd)
        }
        {
            my $Tag = $1;
            if ($Param{NoJavaScript}) {

                # remove on action attributes
                $Replaced += $Tag =~ s{
                    (?:\s|/) on[a-z]+\s*=("[^"]+"|'[^']+'|.+?)($TagEnd|\s)
                }
                {$2}sgxim;

                # remove javascript in a href links or src links
                $Replaced += $Tag =~ s{
                    ((?:\s|;|/)(?:background|url|src|href)\s*=\s*)
                    ('|"|)                                  # delimiter, can be empty
                    (?:\s* $Self->{JavaScriptPrefixRegex} .*?)      # javascript, followed by anything but the delimiter
                    \2                                      # delimiter again
                    (\s|$TagEnd)
                }
                {
                    "$1\"\"$3";
                }sgxime;

                # remove link javascript tags
                $Replaced += $Tag =~ s{
                    ($TagStart link .+? $Self->{JavaScriptPrefixRegex} (.+?|) $TagEnd)
                }
                {}sgxim;

                # remove MS CSS expressions (JavaScript embedded in CSS)
                $Replaced += $Tag =~ s{
                    \sstyle=("|')[^\1]*? $Self->{ExpressionPrefixRegex} [(].*?\1($TagEnd|\s)
                }
                {
                    $2;
                }egsxim;
            }

            # Remove malicious CSS content
            $Tag =~ s{
                (\s)style=("|') (.*?) \2
            }
            {
                my ($Space, $Delimiter, $Content) = ($1, $2, $3);

                if (
                    ($Param{NoIntSrcLoad} && $Content =~ m{url\(})
                    || ($Param{NoExtSrcLoad} && $Content =~ m/((http|ftp|https):|\/\/)/i)) {
                    $Replaced = 1;
                    '';
                }
                else {
                    "${Space}style=${Delimiter}${Content}${Delimiter}";
                }
            }egsxim;

            # remove load tags
            if ($Param{NoIntSrcLoad} || $Param{NoExtSrcLoad}) {
                $Tag =~ s{
                    ($TagStart (.+?) (?: \s | /) (?:src|poster)=(.+?) (\s.+?|) $TagEnd)
                }
                {
                    my $URL = $3;
                    if ($Param{NoIntSrcLoad} || ($Param{NoExtSrcLoad} && $URL =~ /((http|ftp|https):|\/\/)/i)) {
                        $Replaced = 1;
                        '';
                    }
                    else {
                        $1;
                    }
                }segxim;
            }

            # replace original tag with clean tag
            $Tag;
        }segxim;

        $Safety{Replace} += $Replaced;

    } while ($Replaced);    ## no critic

    # check ref && return result like called
    if ( defined $StringScalar ) {
        $Safety{String} = ${$String};
    }
    else {
        $Safety{String} = $String;
    }
    return %Safety;
}

=head2 EmbeddedImagesExtract()

extracts embedded images with data-URLs from an HTML document.

    $HTMLUtilsObject->EmbeddedImagesExtract(
        DocumentRef    => \$Body,
        AttachmentsRef => \@Attachments,
    );

Returns nothing. If embedded images were found, these will be appended
to the attachments list, and the image data URL will be replaced with a
C<cid:> URL in the document.

=cut

sub EmbeddedImagesExtract {
    my ( $Self, %Param ) = @_;

    if ( ref $Param{DocumentRef} ne 'SCALAR' || !defined ${ $Param{DocumentRef} } ) {
        $Kernel::OM->Get('Kernel::System::Log')->Log(
            Priority => 'error',
            Message  => "Need DocumentRef!"
        );
        return;
    }
    if ( ref $Param{AttachmentsRef} ne 'ARRAY' ) {
        $Kernel::OM->Get('Kernel::System::Log')->Log(
            Priority => 'error',
            Message  => "Need AttachmentsRef!"
        );
        return;
    }

    my $ConfigObject = $Kernel::OM->Get('Kernel::Config');
    my $ExternalFQDN = $ConfigObject->Get('ExternalFQDN') || $ConfigObject->Get('FQDN');

    ${ $Param{DocumentRef} } =~ s{(src=")(data:image/)(png|gif|jpg|jpeg|bmp)(;base64,)(.+?)(")}{

        my $Base64String = $5;

        my $FileName     = 'pasted-' . time() . '-' . int(rand(1000000)) . '.' . $3;
        my $ContentType  = "image/$3; name=\"$FileName\"";
        my $ContentID    = 'pasted.' . time() . '.' . int(rand(1000000)) . '@' . $ExternalFQDN;

        my $AttachmentData = {
            Content     => decode_base64($Base64String),
            ContentType => $ContentType,
            ContentID   => $ContentID,
            Filename    => $FileName,
            Disposition => 'inline',
        };
        push @{$Param{AttachmentsRef}}, $AttachmentData;

        # compose new image tag
        $1 . "cid:$ContentID" . $6

    }egxi;

    return 1;
}

1;

=head1 TERMS AND CONDITIONS

This software is part of the OTRS project (L<https://otrs.org/>).

This software comes with ABSOLUTELY NO WARRANTY. For details, see
the enclosed file COPYING for license information (GPL). If you
did not receive this file, see L<https://www.gnu.org/licenses/gpl-3.0.txt>.

=cut
