File Coverage

blib/lib/Pandoc/Elements.pm

Criterion	Covered	Total	%
statement	427	537	79.5
branch	182	394	46.1
condition	60	88	68.1
subroutine	80	91	87.9
pod	6	19	31.5
total	755	1129	66.8

package Pandoc::Elements;
use strict;
## no critic (ProhibitNoStrict, ProhibitSubroutinePrototypes)
use warnings;
use 5.010001;

our $VERSION = '0.36';

use Carp;
use JSON qw(decode_json);
use Scalar::Util qw(blessed reftype);
use Pandoc::Walker qw(walk);
use Pandoc::Version;


our $PANDOC_VERSION; # a string like '1.16'
$PANDOC_VERSION ||= eval { Pandoc::Version->new($ENV{PANDOC_VERSION}) };

# internal variables

my $PANDOC_API_MIN = Pandoc::Version->new('1.12.3');    # since pandoc 1.12.1
my $PANDOC_BIN_MIN = Pandoc::Version->new('1.12.1');

# release version => minimal required api version
my @REQUIRED_API = map { Pandoc::Version->new($_) }
    '1.19'   => '1.17',  # pandoc 1.19 has api 1.17.0.4, compatible with api 1.17
    '1.18'   => '1.17',  # pandoc 1.18 has api 1.17.0.4, compatible with api 1.17
    '1.16'   => '1.16',  # pandoc 1.16 has api 1.16
    '1.17'   => '1.16',  # pandoc 1.17 has api 1.16
;

sub _as_pandoc_version {
    (blessed $_[0] and $_[0]->isa('Pandoc::Version'))
        ? $_[0] : Pandoc::Version->new($_[0])
}

sub pandoc_version {
    if (@_) {
        my $doc = shift;
        if (@_) {
            $doc->api_version(
                _minimum_pandoc_api_for(@_)
                    // croak "pandoc version not supported"
            );
        }
        _minimum_pandoc_version_for_api($doc->api_version);
    } elsif (defined $PANDOC_VERSION) {
        _as_pandoc_version($PANDOC_VERSION)
    } else {
        $REQUIRED_API[0]
    }
}

sub _minimum_pandoc_version_for_api {
    my $api = shift;

    my $version;

    foreach (grep { $_ % 2} 0 .. @REQUIRED_API) { # 1,3,...
        if ($api->match($REQUIRED_API[$_]) ) {
            if (!$version or $version > $REQUIRED_API[$_-1]) {
                $version = $REQUIRED_API[$_-1]
            }
        }
    }

    if (!$version and $api >= $PANDOC_API_MIN) {
        $PANDOC_BIN_MIN;
    } else {
        return $version;
    }
}

sub _minimum_pandoc_api_for {
    my $version = _as_pandoc_version(shift);
    return if @$version <= 1; # require major.minor

    foreach (grep { $_ % 2} 0 .. @REQUIRED_API) { # 1,3,...
        if ($version->match($REQUIRED_API[$_-1]) ) {
            return $REQUIRED_API[$_];
        }
    }

    # required version is newer than any known version
    # return the latest known api version and hope it has not changed
    if ($version > $REQUIRED_API[0]) {
        return $REQUIRED_API[1];
    }

    return $version >= $PANDOC_BIN_MIN ? $PANDOC_API_MIN : undef;
}

our %ELEMENTS = (

    # BLOCK ELEMENTS
    Plain          => [ Block => 'content' ],
    Para           => [ Block => 'content' ],
    CodeBlock      => [ Block => qw(attr content) ],
    RawBlock       => [ Block => qw(format content) ],
    BlockQuote     => [ Block => 'content' ],
    OrderedList    => [ Block => qw(attr content/items) ],
    BulletList     => [ Block => 'content/items' ],
    DefinitionList => [ Block => 'content/items:[DefinitionPair]' ],
    Header         => [ Block => qw(level attr content) ],
    HorizontalRule => ['Block'],
    Table          => [ Block => qw(caption alignment widths headers rows) ],
    Div            => [ Block => qw(attr content) ],
    Null           => ['Block'],
    LineBlock      => [ Block => qw(content) ],

    # INLINE ELEMENTS
    Str         => [ Inline => 'content' ],
    Emph        => [ Inline => 'content' ],
    Strong      => [ Inline => 'content' ],
    Strikeout   => [ Inline => 'content' ],
    Superscript => [ Inline => 'content' ],
    Subscript   => [ Inline => 'content' ],
    SmallCaps   => [ Inline => 'content' ],
    Quoted      => [ Inline => qw(type content) ],
    Cite        => [ Inline => qw(citations content) ],
    Code        => [ Inline => qw(attr content) ],
    Space       => ['Inline'],
    SoftBreak   => ['Inline'],
    LineBreak   => ['Inline'],
    Math        => [ Inline => qw(type content) ],
    RawInline   => [ Inline => qw(format content) ],
    Link        => [ Inline => qw(attr content target) ],
    Image       => [ Inline => qw(attr content target) ],
    Note        => [ Inline => 'content' ],
    Span        => [ Inline => qw(attr content) ],

    # METADATA ELEMENTS
    MetaBool    => [ Meta => 'content' ],
    MetaString  => [ Meta => 'content' ],
    MetaMap     => [ Meta => 'content' ],
    MetaInlines => [ Meta => 'content' ],
    MetaList    => [ Meta => 'content' ],
    MetaBlocks  => [ Meta => 'content' ],

    # TYPE KEYWORDS
    map { $_ => ['Keyword'] }
    qw(DefaultDelim Period OneParen TwoParens SingleQuote DoubleQuote
    DisplayMath InlineMath AuthorInText SuppressAuthor NormalCitation
    AlignLeft AlignRight AlignCenter AlignDefault DefaultStyle Example
    Decimal LowerRoman UpperRoman LowerAlpha UpperAlpha)
);

use parent 'Exporter';
our @EXPORT = (
    keys %ELEMENTS,
    qw(Document attributes metadata citation pandoc_version pandoc_json pandoc_query)
);
our @EXPORT_OK = ( @EXPORT, 'element' );

# create constructor functions
foreach my $name ( keys %ELEMENTS ) {
    no strict 'refs';    ## no critic

    my ( $parent, @accessors ) = @{ $ELEMENTS{$name} };
    my $numargs = scalar @accessors;
    my @parents = map { "Pandoc::Document::$_" } ($parent);
    $parent = join ' ', map { "Pandoc::Document::$_" } $parent,
      map { 'AttributesRole' } grep { $_ eq 'attr' } @accessors;

    ## no critic (ProhibitStringyEval)
    eval "package Pandoc::Document::$name; our \@ISA = qw($parent);";

    *{ __PACKAGE__ . "::$name" } = Scalar::Util::set_prototype(
        sub {
            croak "$name expects $numargs arguments, but given " . scalar @_
              if @_ != $numargs;
            my $self = bless {
                t => $name,
                c => ( @_ == 1 ? $_[0] : [@_] )
            }, "Pandoc::Document::$name";
            $self->set_content(@_);
            $self;
        },
        '$' x $numargs
    );

    for ( my $i = 0 ; $i < @accessors ; $i++ ) {
        my $member = @accessors == 1 ? "\$e->{c}" : "\$e->{c}->[$i]";
        my $code = "my \$e = shift; $member = ( 1 == \@_ ? \$_[0] : [\@_] ) if \@_; return";
        # auto-bless on access via accessor (TODO: move to constructor?)
        $code .= $accessors[$i] =~ s/:\[(.+)\]$//
        ? " [ map { bless \$_, 'Pandoc::Document::$1' } \@{$member} ];"
        : " $member;";
        for ( split '/', $accessors[$i] ) {
            ## no critic
            *{"Pandoc::Document::${name}::$_"} = eval "sub { $code }";
        }
    }
}

sub element {
    my $name = shift;
    no strict 'refs'; #
    croak "undefined element" unless defined $name;
    croak "unknown element $name" unless $ELEMENTS{$name};
    &$name(@_);
}

sub Document {

    my $from_json;
    my $arg = do {
        if ( @_ == 1 ) {
            $from_json = 1;
            my $reftype = reftype $_[0] // '';
            if ( $reftype eq 'ARRAY') {
                # old JSON format
                {
                    meta => $_[0]->[0]->{unMeta},
                    blocks => $_[0]->[1],
                    api_version => 1.16,
                }
            } elsif ( $reftype eq 'HASH' ) {
                $_[0]
            } else {
                croak 'Document: expect array or hash reference'
            }
        } elsif ( @_ == 2 ) {
            # \%meta, \@blocks
            { meta => $_[0], blocks => $_[1] }
        } elsif ( @_ % 2 ) {
            # odd number of args
            croak "Document: too many or ambiguous arguments";
        } else {
            # even number of args: api_version as named parameter
            { meta => shift, blocks => shift, @_ }
        }
    };

    # prefer haskell-style key but accept perl-style and abbreviated key
    my $api_version = $arg->{'pandoc-api-version'}
        // $arg->{pandoc_api_version}
        // $arg->{api_version};

    # We copy values here because $arg may not be a pure AST representation
    my $doc = bless { blocks => ( $arg->{blocks} // [] ) }, 'Pandoc::Document';

    # unblessed metadata in internal format can only come from JSON
    my $meta = $arg->{meta} // {};
    if ($from_json) {
        croak "Document metadata must be a hash" unless 'HASH' eq reftype $meta;
        $doc->{meta} = bless {
            map { $_ => _bless_pandoc_element( $meta->{$_} ) } keys %$meta
        }, 'Pandoc::Document::Metadata';
    } else {
        # otherwise allow user-friendly upgrade via 'metadata' function
        $doc->meta($meta)
    }

    if (!defined $api_version and defined $arg->{pandoc_version}) {
        $doc->pandoc_version($arg->{pandoc_version});
    } else {
        $doc->api_version($api_version // $REQUIRED_API[1]);
    }

    walk $doc, \&_bless_pandoc_element;

    return $doc;

}

# internal helper method
sub _bless_pandoc_element {
    my $e = shift;
    return $e unless ref $e;
    return $e if blessed $e and $e->isa('Pandoc::Document::Element');

    # TODO: run recursively via set_content (don't require 'walk')
    if ( 'MetaMap' eq $e->{t} ) {
        for my $v ( values %{ $e->{c} } ) {
            _bless_pandoc_element( $v );
        }
    }

    bless $e, 'Pandoc::Document::' . $e->{t};
    $e->upgrade($e) if $e->can('upgrade');
    return $e;
}


# specific accessors

sub Pandoc::Document::DefinitionPair::term        { $_[0]->[0] }
sub Pandoc::Document::DefinitionPair::definitions { $_[0]->[1] }

# additional functions

sub attributes($) {

    my $e = Span(['',[],[]],[]); # to make use of AttributesRole
    $e->keyvals(@_);

    return $e->attr;
}

sub citation($) {
    my $a = shift;
    {
        citationId     => $a->{id}     // "missing",
        citationPrefix => $a->{prefix} // [],
        citationSuffix => $a->{suffix} // [],
        citationMode   => $a->{mode}   // bless(
            { t => 'NormalCitation', c => [] },
            'Pandoc::Document::NormalCitation'
        ),
        citationNoteNum => $a->{num}  // 0,
        citationHash    => $a->{hash} // 1,
    };
}

# XXX: must require rather than use Pandoc::Metadata
# or its attempt to use Pandoc::Elements will result in a broken state.
require Pandoc::Metadata;

sub metadata($);  ## no critic

sub metadata($) { ## no critic
    my $value = shift;
    if ( !ref $value ) {
        MetaString($value // '')
    }
    elsif ( JSON::is_bool($value) ) {
        MetaBool($value)
    }
    elsif ( blessed($value) ) {
        if ( $value->can('is_meta') and $value->is_meta ) {
            $value
        }
        elsif ( $value->can('is_inline') and $value->is_inline ) {
            MetaInlines([ $value ])
        }
        elsif ( $value->can('is_block') and $value->is_block ) {
            MetaBlocks([ $value ])
        } elsif ( $value->isa('Pandoc::Document::Metadata') ) {
            MetaMap( { map { $_ => $value->{$_} } keys %$value } )
        } else {
            MetaString("$value")
        }
    }
    elsif ( reftype $value eq 'ARRAY' ) {
        MetaList( [ map { metadata $_ } @$value ] )
    }
    elsif ( reftype $value eq 'HASH' ) {
        MetaMap( { map { $_ => metadata $value->{$_} } keys %$value } )
    }
    else {
        MetaString("$value")
    }
}

sub pandoc_json($) {
    shift if $_[0] =~ /^Pandoc::/;

    my $ast = eval { decode_json( $_[0] ) };
    if ($@) {
        $@ =~ s/ at [^ ]+Elements\.pm line \d+//;
        chomp $@;
        croak $@;
    }
    return Document $ast;
}

*pandoc_query = *Pandoc::Walker::query;

# document element packages

{

    package Pandoc::Document;
    use strict;
    use Carp 'croak';
    use Scalar::Util qw(blessed reftype);
    use Pandoc;
    our $VERSION = '0.04';
    our @ISA = ('Pandoc::Document::Element');
    sub blocks;
    sub name { 'Document' }
    sub meta {
        if (@_ > 1) {
            croak "document metadata must be a hash"
                unless 'HASH' eq reftype $_[1];
            my $map = Pandoc::Elements::metadata($_[1])->content;
            $_[0]->{meta} = bless $map, 'Pandoc::Document::Metadata';
        }
        $_[0]->{meta};
    }
    sub content {
        $_[0]->{blocks} = $_[1] if @_ > 1;
        $_[0]->{blocks};
    }
    *blocks = \&content;
    sub is_document { 1 }
    sub as_block {
        bless { t => 'Div', c => [ {}, $_[0]->{blocks} ] }, 'Pandoc::Document::Div';
    }
    sub value {
        shift->meta->value(@_);
    }
    *metavalue = \&value;
    sub string {
        join '', map { $_->string } @{$_[0]->content}
    }
    sub api_version {
        my $self = shift;
        if ( @_ ) {
            my $version = Pandoc::Version->new(shift);
            croak "api_version must be >= $PANDOC_API_MIN"
                if $version < $PANDOC_API_MIN;
            croak "api_version must have major and minor part"
                if @$version < 2;
            $self->{'pandoc-api-version'} = $version;
        }
        return $self->{'pandoc-api-version'};
    }
    *pandoc_version = \&Pandoc::Elements::pandoc_version;
    sub outline {
        my ($self, $depth) = @_;
        _sections( [@{$self->blocks}], $depth );
    }
    sub _sections {
        my ($list, $depth) = @_;
        my (@blocks, @sections);

        # everything up to the first Header
        while (@$list) {
            if ($list->[0]->name eq 'Header') {
                last if !$depth or $depth >= $list->[0]->level;
            }
            push @blocks, shift @$list;
        }

        # divide into sections
        while (@$list) {
            my $header = shift @$list;
            my $level  = $header->level;

            my @content;
            while (@$list) {
                if ($list->[0]->name eq 'Header') {
                    last if $list->[0]->level <= $level;
                }
                push @content, shift @$list;
            }

            my $s = ($depth and $depth < $level)
                ? { blocks => \@content }
                : _sections(\@content,$depth);
            push @sections, { header => $header, %$s };
        }

        return { blocks => \@blocks, sections => \@sections };
    }
    sub to_pandoc {
        my ($self, @args) = @_;
        my $pandoc = (@args and blessed($args[0]) and $args[0]->isa('Pandoc'))
                   ? shift(@args) : pandoc;

        my $api_version = $self->api_version;   # save
        $self->pandoc_version( $pandoc->version );

        my $in = $self->to_json;
        $self->api_version($api_version);       # restore

        $pandoc->run( [ -f => 'json', @args ], { in => \$in, out => \my $out } );
        return $out;
    }
    foreach my $format (qw(markdown latex html rst plain)) {
        no strict 'refs';
        *{ __PACKAGE__ . "::to_$format" } = sub {
            shift()->to_pandoc( @_, '-t' => $format );
        }
    }
}

{
    package Pandoc::Document::Keyword;
    our @ISA = ('Pandoc::Document::Element');
}

{

    package Pandoc::Document::Element;
    use strict;
    use warnings;
    our $VERSION = $Pandoc::Document::VERSION;
    use JSON ();
    use Scalar::Util qw(reftype blessed);
    use Pandoc::Walker ();
    use Pandoc::Selector;
    use subs qw(walk query transform);    # Silence syntax warnings

    sub to_json {
        JSON->new->utf8->canonical->convert_blessed->encode( $_[0] );
    }

    sub TO_JSON {

        # Run everything thru this method so arrays/hashes are cloned
        # and objects without TO_JSON methods are stringified.
        # Required to ensure correct scalar types for Pandoc.

# There is no easy way in Perl to tell if a scalar value is already a string or number,
# so we stringify all scalar values and numify/boolify as needed afterwards.

        my ( $ast, $maybe_blessed ) = @_;
        if ( $maybe_blessed && blessed $ast ) {
            return $ast if $ast->can('TO_JSON');    # JSON.pm will convert
                 # may have overloaded stringification! Should we check?
                 # require overload;
              # return "$ast" if overload::Method($ast, q/""/) or overload::Method($ast, q/0+/);
              # carp "Non-stringifiable object $ast";
            return "$ast";
        }
        elsif ( 'ARRAY' eq reftype $ast ) {
            return [ map { ref($_) ? TO_JSON( $_, 1 ) : "$_"; } @$ast ];
        }
        elsif ( 'HASH' eq reftype $ast ) {
            my %ret = %$ast;
            while ( my ( $k, $v ) = each %ret ) {
                $ret{$k} = ref($v) ? TO_JSON( $v, 1 ) : "$v";
            }
            return \%ret;
        }
        else { return "$ast" }
    }

    sub name        { $_[0]->{t} }
    sub content     {
       my $e = shift;
       $e->set_content(@_) if @_;
       $e->{c}
    }
    sub set_content { # TODO: document this
       my $e = shift;
       $e->{c} = @_ == 1 ? $_[0] : [@_]
    }
    sub is_document { 0 }
    sub is_block    { 0 }
    sub is_inline   { 0 }
    sub is_meta     { 0 }
    sub as_block    {
        bless { t => 'Null', c => [] }, 'Pandoc::Document::Null';
    }
    *walk      = *Pandoc::Walker::walk;
    *query     = *Pandoc::Walker::query;
    *transform = *Pandoc::Walker::transform;

    sub string {

        # TODO: fix issue #4 to avoid this duplication
        if ( $_[0]->name =~ /^(Str|Code|CodeBlock|Math|MetaString)$/ ) {
            return $_[0]->content;
        }
        elsif ( $_[0]->name =~ /^(LineBreak|SoftBreak|Space)$/ ) {
            return ' ';
        }
        join '', @{
            $_[0]->query(
                {
                    'Str|Code|CodeBlock|Math|MetaString'  => sub { $_->content },
                    'LineBreak|Space|SoftBreak' => sub { ' ' },
                }
            );
        };
    }

    sub match {
        my $self = shift;
        my $selector = blessed $_[0] ? shift : Pandoc::Selector->new(shift);
        $selector->match($self);
    }
}

{

    package Pandoc::Document::AttributesRole;
    use Hash::MultiValue;
    use Scalar::Util qw(reftype blessed);
    use Carp qw(croak);

    sub id {
        $_[0]->attr->[0] = defined $_[1] ? "$_[1]" : "" if @_ > 1;
        $_[0]->attr->[0]
    }

    sub classes {
        my $e = shift;
        croak 'Method classes() is not a setter' if @_;
        warn "->classes is deprecated. Use [ split ' ', \$e->class ] instead\n";
        $e->attr->[1]
    }

    sub class {
        my $e = shift;
        if (@_) {
            $e->attr->[1] = [
                grep { $_ ne '' }
                map { split qr/\s+/, $_ }
                map { (ref $_ and reftype $_ eq 'ARRAY') ? @$_ : $_ }
                @_
            ];
        }
        join ' ', @{$e->attr->[1]}
    }

    sub add_attribute {
        my ($e, $key, $value) = @_;
        if ($key eq 'id') {
            $e->id($value);
        } elsif ($key eq 'class') {
            $value //= '';
            $value = ["$value"] unless (reftype $value // '') eq 'ARRAY';
            push @{$e->attr->[1]}, grep { $_ ne '' } map { split qr/\s+/, $_ } @$value;
        } else {
            push @{$e->attr->[2]}, [ $key, "$value" ];
        }
    }

    sub keyvals {
        my $e = shift;
        if (@_) {
            my $attrs = @_ == 1 ? shift : Hash::MultiValue->new(@_);
            unless (blessed $attrs and $attrs->isa('Hash::MultiValue')) {
                $attrs = Hash::MultiValue->new(%$attrs);
            }
            $e->attr->[1] = [] if exists $attrs->{class};
            $e->attr->[2] = [];
            $attrs->each(sub { $e->add_attribute(@_) });
        }
        my @h;
        push @h, id => $e->id if $e->id ne '';
        push @h, class => $e->class if @{$e->attr->[1]};
        Hash::MultiValue->new( @h, map { @$_ } @{$e->attr->[2]} );
    }

}

{

    package Pandoc::Document::Block;
    our $VERSION = $PANDOC::Document::VERSION;
    our @ISA     = ('Pandoc::Document::Element');
    sub is_block { 1 }
    sub as_block { $_[0] }
    sub null { # TODO: document this (?)
        %{$_[0]} = (t => 'Null', c => []);
        bless $_[0], 'Pandoc::Document::Null';
    }
}

{

    package Pandoc::Document::Inline;
    our $VERSION = $PANDOC::Document::VERSION;
    our @ISA     = ('Pandoc::Document::Element');
    sub is_inline { 1 }
    sub as_block {
        bless { t => 'Plain', c => [ $_[0] ] }, 'Pandoc::Document::Plain';
    }
}

{

    package Pandoc::Document::LinkageRole;
    our $VERSION = $PANDOC::Document::VERSION;

    for my $Element (qw[ Link Image ]) {
        no strict 'refs';    #no critic
        unshift @{"Pandoc::Document::${Element}::ISA"}, __PACKAGE__; # no critic
    }

    sub url   { my $e = shift; $e->{c}->[-1][0] = shift if @_; return $e->{c}->[-1][0] //= ""; }
    sub title { my $e = shift; $e->{c}->[-1][1] = shift if @_; return $e->{c}->[-1][1] //= ""; }

    sub upgrade {
        # prepend attributes to old-style ast
        unshift @{ $_[0]->{c} }, [ "", [], [] ]
            if 2 == @{ $_[0]->{c} };
    }
}

# Special TO_JSON methods to coerce data to int/number/Boolean as appropriate
# and to downgrade document model depending on pandoc_version

sub Pandoc::Document::to_json {
    my ($self) = @_;

    local $Pandoc::Elements::PANDOC_VERSION =
        $Pandoc::Elements::PANDOC_VERSION // $self->pandoc_version;

    return Pandoc::Document::Element::to_json( $self->TO_JSON );
}

sub Pandoc::Document::TO_JSON {
    my ( $self ) = @_;
    return $self->api_version >= 1.17
        ? { %$self }
        : [ { unMeta => $self->{meta} }, $self->{blocks} ]
}

sub Pandoc::Document::SoftBreak::TO_JSON {
    if ( pandoc_version() < '1.16' ) {
        return { t => 'Space', c => [] };
    } else {
        return { t => 'SoftBreak', c => [] };
    }
}

sub Pandoc::Document::LinkageRole::TO_JSON {
    my $ast = Pandoc::Document::Element::TO_JSON( $_[0] );
    if ( pandoc_version() < 1.16 ) {
        # remove attributes
        $ast->{c} = [ @{ $ast->{c} }[ 1, 2 ] ];
    }
    return $ast;
}

sub Pandoc::Document::Header::TO_JSON {
    my $ast = Pandoc::Document::Element::TO_JSON( $_[0] );

    # coerce heading level to int
    $ast->{c}[0] = int( $ast->{c}[0] );
    return $ast;
}

sub Pandoc::Document::OrderedList::TO_JSON {
    my $ast = Pandoc::Document::Element::TO_JSON( $_[0] );

    # coerce first item number to int
    $ast->{c}[0][0] = int( $ast->{c}[0][0] );
    return $ast;
}

sub Pandoc::Document::Table::TO_JSON {
    my $ast = Pandoc::Document::Element::TO_JSON( $_[0] );

    # coerce column widths to numbers (floats)
    $_ += 0 for @{ $ast->{c}[2] };    # faster than map
    return $ast;
}

sub Pandoc::Document::Cite::TO_JSON {
    my $ast = Pandoc::Document::Element::TO_JSON( $_[0] );
    for my $citation ( @{ $ast->{c}[0] } ) {
        for my $key (qw[ citationHash citationNoteNum ]) {

            # coerce to int
            $citation->{$key} = int( $citation->{$key} );
        }
    }
    return $ast;
}

sub Pandoc::Document::LineBlock::TO_JSON {
    my $ast     = Pandoc::Document::Element::TO_JSON( $_[0] );
    my $content = $ast->{c};

    for my $line ( @$content ) {

        # Convert spaces at the beginning of each line
        # to Unicode non-breaking spaces, because pandoc does.
        next unless @$line and $line->[0]->{t} eq 'Str';
        $line->[0]->{c} =~ s{^(\x{20}+)}{ "\x{a0}" x length($1) }e;
    }

    return $ast if pandoc_version() >= 1.18;

    my $c = [ map { ; @$_, LineBreak() } @{$content} ];
    pop @$c;    # remove trailing line break
    return Para( $c )->TO_JSON;
}

1;
__END__