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package Pandoc::Filter::HeaderIdentifiers;
use strict;
use warnings;
use 5.010;
our $VERSION = '0.34';
use parent 'Pandoc::Filter';
use Pandoc::Elements;
our @EXPORT = qw(header_identifier InPandocHeaderIdentifier);
## FUNCTIONS
sub header_identifier {
my $id = shift;
my $ids = shift;
# stringify inline elements except footnotes
$id = join '', @{
pandoc_query( $id, sub {
$_->is_inline and $_->name ne 'Note' ? $_->string : \undef
})
} if ref $id;
# Convert all alphabetic characters to lowercase.
$id = lc $id;
# these steps not strictly documented but it is how Pandoc works
$id =~ s/\p{^InPandocHeaderIdOrWs}+//g;
$id =~ s/\p{WhiteSpace}+$//;
# Replace all spaces and newlines with hyphens.
$id =~ s/\p{WhiteSpace}+/-/g;
# Remove all punctuation, except underscores, hyphens, periods, and whitespace.
$id =~ s/\p{^InPandocHeaderIdentifier}//g;
# remove everything up to the first letter
$id =~ s/^[_.0-9-]+//;
# if nothing is left, use the identifier 'section'
$id ||= 'section';
# add counter on repeated identifiers
if ($ids and $ids->{$id}++) {
$id .= '-' . ($ids->{$id}-1);
}
return $id;
}
## METHODS
sub new {
bless { }, shift;
}
sub apply {
my ($self, $doc) = @_;
my $ids = @_ > 2 ? $_[2] : {};
# collect existing identifiers
$doc->walk( Header => sub {
my $id = $_->id;
return if $id !~ /^\p{InPandocHeaderIdentifier}+$/ or $id !~ /^\p{Letter}/;
if ($id =~ /^(.+)-(\d+)$/) {
$id = $1;
$ids->{$id} = $2 unless defined $ids->{$id} and $ids->{$id} > $2;
}
$ids->{$id}++;
} );
# add missing identifiers
$doc->walk( Header => sub {
$_[0]->id( header_identifier( $_[0]->content, $ids ) ) if $_[0]->id eq '';
});
$doc;
}
## CHARACTER PROPERTIES
sub InPandocHeaderIdentifier {
return "+utf8::Letter\n-utf8::Uppercase_Letter\n-utf8::Titlecase_Letter\n0030 0039\n005F\n002d 002e\n";
}
sub InPandocHeaderIdOrWs {
return "+utf8::Whitespace\n+utf8::Letter\n-utf8::Uppercase_Letter\n-utf8::Titlecase_Letter\n0030 0039\n005F\n002d 002e\n";
}
__END__
=head1 NAME
Pandoc::Filter::HeaderIdentifiers - Add identifiers to headers
=head1 SYNOPSIS
my $id = header_identifier( $header->content ); # calculate identifier
Pandoc::Filter::HeaderIdentifiers->new->apply($doc); # add all identifiers
=head1 DESCRIPTION
This L<Pandoc::Filter> adds identifier attributes (L<id|Pandoc::Elements/id>)
to all L<Headers|Pandoc::Elements/Header> elements. It uses the same algorithm
as internally used by pandoc. The module also exports function
C<header_identifier> to calculate an identifier from a list of elements.
=head1 FUNCTIONS
=head2 header_identifier( $content [, $ids ] )
Returns an identifier for a given list of L<inlines|Pandoc::Elements/INLINE
ELEMENTS> or string (C<$content>). Optionally takes into account and updates
existing ids, given as hash reference mapping identifier to usage count
(C<$ids>).
=head1 METHODS
=head2 apply( $element [, $ids ] )
Add identifiers to all L<Header|Pandoc::Elements/Header> elements found at a
given element (typically a L<Document|Pandoc::Elements/Document>. A hash
reference of existing identifier counts (or an empty hash to get the new
counts) can be passed in addition.
=head1 CHARACTER PROPERTIES
=head2 InPandocHeaderIdentifier
Matches all Unicode lowercase letters, digits 0 to 9, underscore, hyphen, and
period. In the unlikely event that you want to check whether a given string
could have been generated as header identifier, use this:
$id =~ /^\p{InPandocHeaderIdentifier}+$/ and $id =~ /^\p{Letter}/
=head1 SEE ALSO
L<http://pandoc.org/MANUAL.html#header-identifiers>
=cut
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