# Convert POD data to formatted overstrike text
#
# This was written because the output from:
#
#     pod2text Text.pm > plain.txt; less plain.txt
#
# is not as rich as the output from
#
#     pod2man Text.pm | nroff -man > fancy.txt; less fancy.txt
#
# and because both Pod::Text::Color and Pod::Text::Termcap are not device
# independent.
#
# SPDX-License-Identifier: GPL-1.0-or-later OR Artistic-1.0-Perl

##############################################################################
# Modules and declarations
##############################################################################

package Pod::Text::Overstrike;

use 5.006;
use strict;
use warnings;

use vars qw(@ISA $VERSION);

use Pod::Text ();

@ISA = qw(Pod::Text);

$VERSION = '4.11';

##############################################################################
# Overrides
##############################################################################

# Make level one headings bold, overriding any existing formatting.
sub cmd_head1 {
    my ($self, $attrs, $text) = @_;
    $text =~ s/\s+$//;
    $text = $self->strip_format ($text);
    $text =~ s/(.)/$1\b$1/g;
    return $self->SUPER::cmd_head1 ($attrs, $text);
}

# Make level two headings bold, overriding any existing formatting.
sub cmd_head2 {
    my ($self, $attrs, $text) = @_;
    $text =~ s/\s+$//;
    $text = $self->strip_format ($text);
    $text =~ s/(.)/$1\b$1/g;
    return $self->SUPER::cmd_head2 ($attrs, $text);
}

# Make level three headings underscored, overriding any existing formatting.
sub cmd_head3 {
    my ($self, $attrs, $text) = @_;
    $text =~ s/\s+$//;
    $text = $self->strip_format ($text);
    $text =~ s/(.)/_\b$1/g;
    return $self->SUPER::cmd_head3 ($attrs, $text);
}

# Level four headings look like level three headings.
sub cmd_head4 {
    my ($self, $attrs, $text) = @_;
    $text =~ s/\s+$//;
    $text = $self->strip_format ($text);
    $text =~ s/(.)/_\b$1/g;
    return $self->SUPER::cmd_head4 ($attrs, $text);
}

# The common code for handling all headers.  We have to override to avoid
# interpolating twice and because we don't want to honor alt.
sub heading {
    my ($self, $text, $indent, $marker) = @_;
    $self->item ("\n\n") if defined $$self{ITEM};
    $text .= "\n" if $$self{opt_loose};
    my $margin = ' ' x ($$self{opt_margin} + $indent);
    $self->output ($margin . $text . "\n");
    return '';
}

# Fix the various formatting codes.
sub cmd_b { local $_ = $_[0]->strip_format ($_[2]); s/(.)/$1\b$1/g; $_ }
sub cmd_f { local $_ = $_[0]->strip_format ($_[2]); s/(.)/_\b$1/g; $_ }
sub cmd_i { local $_ = $_[0]->strip_format ($_[2]); s/(.)/_\b$1/g; $_ }

# Output any included code in bold.
sub output_code {
    my ($self, $code) = @_;
    $code =~ s/(.)/$1\b$1/g;
    $self->output ($code);
}

# Strip all of the formatting from a provided string, returning the stripped
# version.
sub strip_format {
    my ($self, $text) = @_;
    $text =~ s/(.)[\b]\1/$1/g;
    $text =~ s/_[\b]//g;
    return $text;
}

# We unfortunately have to override the wrapping code here, since the normal
# wrapping code gets really confused by all the backspaces.
sub wrap {
    my $self = shift;
    local $_ = shift;
    my $output = '';
    my $spaces = ' ' x $$self{MARGIN};
    my $width = $$self{opt_width} - $$self{MARGIN};
    while (length > $width) {
        # This regex represents a single character, that's possibly underlined
        # or in bold (in which case, it's three characters; the character, a
        # backspace, and a character).  Use [^\n] rather than . to protect
        # against odd settings of $*.
        my $char = '(?:[^\n][\b])?[^\n]';
        if (s/^((?>$char){0,$width})(?:\Z|\s+)//) {
            $output .= $spaces . $1 . "\n";
        } else {
            last;
        }
    }
    $output .= $spaces . $_;
    $output =~ s/\s+$/\n\n/;
    return $output;
}

##############################################################################
# Module return value and documentation
##############################################################################

1;
__END__

=for stopwords
overstrike overstruck Overstruck Allbery terminal's

=head1 NAME

Pod::Text::Overstrike - Convert POD data to formatted overstrike text

=head1 SYNOPSIS

    use Pod::Text::Overstrike;
    my $parser = Pod::Text::Overstrike->new (sentence => 0, width => 78);

    # Read POD from STDIN and write to STDOUT.
    $parser->parse_from_filehandle;

    # Read POD from file.pod and write to file.txt.
    $parser->parse_from_file ('file.pod', 'file.txt');

=head1 DESCRIPTION

Pod::Text::Overstrike is a simple subclass of Pod::Text that highlights
output text using overstrike sequences, in a manner similar to nroff.
Characters in bold text are overstruck (character, backspace, character)
and characters in underlined text are converted to overstruck underscores
(underscore, backspace, character).  This format was originally designed
for hard-copy terminals and/or line printers, yet is readable on soft-copy
(CRT) terminals.

Overstruck text is best viewed by page-at-a-time programs that take
advantage of the terminal's B<stand-out> and I<underline> capabilities, such
as the less program on Unix.

Apart from the overstrike, it in all ways functions like Pod::Text.  See
L<Pod::Text> for details and available options.

=head1 BUGS

Currently, the outermost formatting instruction wins, so for example
underlined text inside a region of bold text is displayed as simply bold.
There may be some better approach possible.

=head1 AUTHOR

Originally written by Joe Smith <Joe.Smith@inwap.com>, using the framework
created by Russ Allbery <rra@cpan.org>.  Subsequently updated by Russ Allbery.

=head1 COPYRIGHT AND LICENSE

Copyright 2000 by Joe Smith <Joe.Smith@inwap.com>

Copyright 2001, 2004, 2008, 2014, 2018 by Russ Allbery <rra@cpan.org>

This program is free software; you may redistribute it and/or modify it
under the same terms as Perl itself.

=head1 SEE ALSO

L<Pod::Text>, L<Pod::Simple>

The current version of this module is always available from its web site at
L<https://www.eyrie.org/~eagle/software/podlators/>.  It is also part of the
Perl core distribution as of 5.6.0.

=cut

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