path: root/pandoc-emphasis

#!/usr/bin/perl

# emphasis + doublequote means technical or foreign term.
# doublequote + emphasis means title.
#
# Pandoc parses quotation marks in two ways (possibly concurrently):
#  * Leave as-is when parsing and serializing
#  * smart-converts to Quoted object and serializes to ``'' or `'
# Some quotation marks may still be left as-is in smart mode, depending
# on parser.  See e.g. https://github.com/jgm/pandoc/issues/2012
#
# This filter handles Quoted objects and (less reliably) Char quotes.

use Moops -strict;

use Pandoc::Filter 0.06;
use Pandoc::Elements;
use Scalar::Util qw(reftype);
use Clone qw(clone);

use Log::Any qw($log);
use Log::Any::Adapter ( 'ScreenColoredLevel',
    use_color => ! -t *STDERR );

# TODO: add class Egg, and coercing roles Exotic and Noble

class Uterus with MooX::Role::Logger {
    lexical_has fetuses => (
        isa => ArrayRef[Object],
        default => sub { [] },
        reader => \( my $fetuses ),
        lazy => 1,
    );
    has is_monstrous => (
        is => 'rw',
        isa => Bool,
        default => sub { 0 },
    );
    # TODO: replace with method fertilize, with Egg coercions
    method implant ( Object $clone ) {
        push @{ $self->$fetuses }, $clone;
    }
    method create ( Object $monster ) {
        push @{ $self->$fetuses }, $monster;
        $self->is_monstrous(1);
    }
    method abort () {
        splice @{ $self->$fetuses };
        return;
    }
    method deliver () {
        my @babies = splice @{ $self->$fetuses };
        if ($self->_logger->is_debug()) {
#           $self->_logger->debugf( 'giving birth: %s',
#               \@babies );
            for my $baby ( @babies ) {
                $self->_logger->debugf( 'giving birth: %s',
                    $baby->name );
            };
        };
        return [ @babies ];
    }
}

my $womb = Uterus->new;

pandoc_filter(
    \&emphasis,
);

# FIXME: wrongly messes with "'''open'''": avoid strong emphasis
# FIXME: wrongly adds quotation mark to "'''''if''''' ...": maybe avoid emphasis not immediately followed by plain text?
# TODO: flatten only Str and Space as content of new children, else skip
sub emphasis {
    my $self = shift;
    # TODO: replace @children with $kids ref, and use at more places
    my (@children, $last_child, $kid);

    # we do our own walk of inline objects
    return unless $self->is_block;

    # skip known irrelevant block types
    return if ( $self->name =~
        /CodeBlock|RawBlock|Header|HorizontalRule|Null/ );

    # skip known irrelevant block types
    if ( $self->name =~
        /OrderedList|BulletList|DefinitionList|Table/
    ) {
        $log->infof( 'emphasis: skipping unsupported block: %s',
            $self->name );
        return
    };

    # align coherently and walk direct descendants
    if ( reftype $self->content eq 'ARRAY') {
        @children = @{ $self->content };
        $last_child = scalar $self->content->[
            ( keys @{ $self->content } ) -1 ];
    } elsif ( reftype $self->content eq 'HASH') {
        @children = [ $self->content ];
        $last_child = scalar $self->content;
    } else {
        $log->warnf( 'emphasis: skipping oddly structured block: %s',
            $self->name );
        return;
    }
    $kid = 0;
    $log->debugf( 'emphasis: processing block: %s',
        $self->name );
    while ($kid < keys @children ) {
        # title markup via Quoted
        # TODO: limit container to type DoubleQuote
        if ( $self->content->[$kid]->name eq 'Quoted'
            and $self->content->[$kid]->content->[0]->name eq 'Emph'
        ) {
            my $new_content = stringify(
                $self->content->[$kid]->content->[0] );
            $log->infof( 'emphasis: Quoted+Emph→title: %s',
                $new_content );
            # FIXME: LaTeX-encode content
            $womb->create(
                Quoted( DoubleQuote,
                $new_content ));
            $kid++;
            next;
        }
        # title markup via quotation mark in Str
        # TODO: widen container to non-upright doublequote
        if ( $self->content->[$kid]->name eq 'Str'
            and $self->content->[$kid]->content eq '"'
            and $self->content->[$kid+1]->name eq 'Emph'
            and $self->content->[$kid+2]->name eq 'Str'
            and $self->content->[$kid+2]->content eq '"'
        ) {
            $log->infof( 'emphasis: %s+Emph→title: %s',
                $self->content->[$kid]->content,
                stringify(
                    $self->content->[$kid+1]->content ));
            $womb->create(
                Quoted( DoubleQuote,
                $self->content->[$kid+1]->content ));
            $kid += 3;
            next;
        };
        # foreign markup via Quoted
        # TODO: limit container to type DoubleQuote
        if ( $self->content->[$kid]->name eq 'Emph'
            and $self->content->[$kid]->content->[0]->name eq 'Quoted'
        ) {
            my $new_content = stringify(
                $self->content->[$kid]->content->[0] );
            $log->infof( 'emphasis: Emph+Quoted→foreign: %s',
                $new_content );
            # FIXME: LaTeX-encode content
            $womb->create(
                RawInline( 'latex',
                sprintf( '\foreign{%s}',
                    $new_content )));
            $kid++;
            next;
        }
        # foreign markup via quotation mark in Str
        # TODO: widen container to non-upright doublequote
        if ( $self->content->[$kid]->name eq 'Emph'
            and stringify($self->content->[$kid]) =~ /^(\")([^\"]+)\"$/
        ) {
            $log->infof( 'emphasis: Emph+%s→foreign: %s',
                $1, $2 );
            # FIXME: LaTeX-encode content
            $womb->create(
                RawInline( 'latex',
                sprintf( '\foreign{%s}',
                    $2 )));
            $kid++;
            next;
        }

        # clone healthy kid, in case of monstrous siblings
        $womb->implant( $self->content->[$kid] );
        $kid++;
    }

    # cheaper to abort (i.e. return nothing) if no monsters created
    return $womb->abort unless ($womb->is_monstrous);

    my $kids = $womb->deliver;
    $log->debugf( 'delivered kids: %s', $kids );

    # dirty hack to preserve non-content block parts
    my $new_block = clone $self;
    $$new_block{c} = $kids;
    $log->debugf( 'block: %s', $new_block );

    return [ $new_block ];
}