# =========================
sub commonTagsHandler
{
### my ( $text, $topic, $web ) = @_;   # do not uncomment, use $_[0], $_[1]... instead

    # Diff utility to compare docs
    $_[0] =~ s/%TWIKIDOCDIFF{(.*?)}%/twikiDocDiffHandler( $1, $_[2] )/geo;
}

# =========================
sub twikiDocDiffHandler
{
    my ( $args, $web ) = @_;

    my $topic = $TWiki::includingTopicName;  # CODE_SMELL: unofficial code reference
    my $text = "";
    if( $args eq "diff" ) {

        my $diffCmd = "/usr/bin/diff -b -C5 -u";
        my $dataDir = TWiki::Func::getDataDir();
        my $betaDataDir = "/home/beta/data";

        unless( -e "$betaDataDir/$web/$topic.txt" ) {
            return "Error: Topic does not exist in TWiki Beta.";
        }
        my $diff = `$diffCmd $betaDataDir/$web/$topic.txt $dataDir/$web/$topic.txt`;
        $diff =~ s/[\n\r]+/\n/gos;
        $diff =~ s/^(.)/\n$1/gos;
        $diff =~ s/\&/&/go;
        $diff =~ s/\</&lt;/go;
        $diff =~ s/\>/&gt;/go;
        $diff =~ s/\%/&#037;/go;
        $diff =~ s/\*/&#042;/go;
        $diff =~ s/\:/&#058;/go;
        $diff =~ s/\=/&#061;/go;
        $diff =~ s/\_/&#095;/go;
        $diff =~ s/\\/&#092;/go;
        $diff =~ s/\[/&#091;/go;
        $diff =~ s/\]/&#093;/go;
        $diff =~ s/\|/&#124;/go;
        $diff =~ s/([\s\(])([A-Z])/$1<nop>$2/go; # defuse WikiWord links

        $diff =~ s/\t/&nbsp; &nbsp;/go;
        $diff =~ s/\n(\-)([^\n]*)/\n%RED%$2%ENDCOLOR%/go;
        $diff =~ s/\n(\+)([^\n]*)/\n%GREEN%$2%ENDCOLOR%/go;
        $diff =~ s/\n(\@)([^\n]*)/\n%BLUE%<b>$1$2<\/b>%ENDCOLOR%/go;
        $diff =~ s/\@/&#64;/go;
        $diff =~ s/^\n//gos;
        $diff =~ s/\n/<br \/>\n/gos;
        $text .= "<tt>$diff</tt>";

    } elsif( TWiki::Access::userIsInGroup( TWiki::Func::userToWikiName( $user ), "TWikiAdminGroup" ) ) {
        my $time = time();
        $text  = "<br />TWiki Beta topic . { ";
        $text .= "<a href=\"/beta/view/$web/$topic\">View</a> | ";
        $text .= "<a href=\"/beta/edit/$web/$topic?t=$time\">Edit</a> | ";
        $text .= "<a href=\"%SCRIPTURLPATH%/oops%SCRIPTSUFFIX%/$web/$topic?template=oopstwikidocdiff\">Diff</a>";
        $text .= " }";

    } else {
        $text .= "<a href=\"%SCRIPTURLPATH%/viewauth/$web/$topic\">.</a>";
    }
    return $text;
}

# =========================