#!/usr/bin/perl

# emphasis + doublequote means technical or foreign term.
# doublequote + emphasis means title.

use Moops -strict;

use feature qw(switch);
no if $] >= 5.018, warnings => "experimental::smartmatch";

use Pandoc::Filter 0.06;
use Pandoc::Elements;

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

class Window {
	use Pandoc::Filter;

	has view => {
		is => 'rw',
		isa => Object,
	};
	has ledge => {
		is => 'rw',
		isa => Maybe[Object],
	};
	method set_view ( Object $object ) {
		$self->view($object);
	}
	method peek_at_ledge () {
		return
			unless ( $self->ledge );
		my $value = stringify( $self->ledge );
		$value = $self->ledge->content;
		return $value;
	}
	method clear_ledge () {
		$self->ledge(undef);
	}
	method my $recall_from_ledge () {
		my $oldview = $self->ledge;
		$self->clear_ledge;
		return $oldview;
	}
	method describe_view () {
		return [ $self->$recall_from_ledge, $self->view ]
			if ( $self->ledge );
		return;
	}
	method interpret_view ( Object $interpretation ) {
		return [ $self->$recall_from_ledge, $interpretation ]
			if ( $self->$recall_from_ledge );
		return [ $interpretation ];
	}
	method suppress_view () {
		return [ $self->$recall_from_ledge ]
			if ( $self->ledge );
		return [];
	}
	method postpone_view () {
		$self->ledge( $self->view );
		return [];
	}
}

my $window = Window->new;

my ($title, $foreign);

pandoc_filter(
	\&emphasis,
);

sub emphasis {
	my $self = shift;
	return unless ( $self->name =~ /Str|Emph/ );
	if ( $self->name eq 'Emph' ) {
		$window->set_view($self);
		given ( stringify($self) ) {
			when ( $self->content->[0]->name eq 'Str' ) {
				if ( $window->peek_at_ledge() eq '"' ) {
					$window->clear_ledge();
					$title++;
					$log->infof( 'emphasis: %s+Emph→title: %s',
						'"',
						$_ );
					return $window->interpret_view(
						Quoted( DoubleQuote,
						$self->content ));
				}
			}
			when ( $self->content->[0]->name eq 'Quoted' ) {
				$log->infof( 'emphasis: Emph+Quoted→foreign: %s',
					$_ );
				# FIXME: LaTeX-encode text
				return $window->interpret_view(
					RawInline( 'latex',
					'\\foreign{' . $_ . '}' ));
			}
		}
		return $window->describe_view();
	}
	if ( $self->name eq 'Str' ) {
		$window->set_view($self);
		given ( $self->content ) {
			when ('"') {
				if ($title) {
					$title--;
					return $window->suppress_view();
				};
				return $window->postpone_view();
			}
		}
		$window->clear_ledge();
		if ($title) {
			$log->warnf( "emphasis: odd title end markup." );
			$title--;
		}
		return $window->describe_view();
	}
	return;
}