$latex = 'internal mylatex platex %A %O %S';
$bibtex = 'pbibtex %O %B';
$dvipdf = 'dvipdfmx %O -o %D %S';
$makeindex = 'mendex %O -o %D %S';
$max_repeat = 10;
$pdf_mode = 3;

sub get_preamble_from_tex {
    my ($base) = @_;
    open(my $fh, '<', "$base.tex") or die "Could not open file '$base.tex' $!";
    my $preamble = '';
    while (my $line = <$fh>) {
        last if $line =~ /^\s*\\begin\{document\}|\\endofdump\b/;
        $preamble .= $line;
    }
    close $fh;
    return $preamble;
}

sub save_preamble {
    my ($base) = @_;
    unless (-e "$base.preamble") {
        Run_subst("touch $base.preamble");
    }
    my $preamble = get_preamble_from_tex($base);
    open(my $fh, '>', "$base.preamble") or die "Could not open file '$base.preamble' $!";
    print $fh $preamble;
    close $fh;
}

sub make_fmt {
    my ($engine, $base) = @_;
    print "mylatex: making $base.fmt in ini mode... \n";
    save_preamble($base);
    Run_subst("$engine -ini -jobname=\"$base\" \\\&$engine mylatexformat.ltx %S");
}

sub is_different_preamble {
    my ($base) = @_;
    if (-e "$base.preamble") {
        my $preamble = get_preamble_from_tex($base);
        open(my $fh, '<', "$base.preamble") or die "Could not open file '$base.preamble' $!";
        my $old_preamble = do { local $/; <$fh> };
        close $fh;
        return $preamble ne $old_preamble;
    } else {
        return 1;
    }
}

sub mylatex {
    my ($engine, $base, @args) = @_;
    my $com = join(' ', @args);
    if (!-e "$base.fmt" || is_different_preamble($base)) {
        make_fmt($engine, $base);
    }
    print "mylatex: $base.fmt detected, so running normal latex... \n";
    return Run_subst("$engine -fmt $base $com");
}