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}

sub parse
{
    my ($self, $text) = @_;

    # isolate multilingual sections
    $self->_tokenize($text);

    # replace multilingual sections with TT directives
    my ($S, $E, $LANGVAR) = map $self->{$_}, qw(_start _end _langvar);

    # if language is a variant (en_US), create a template variable holding the fallback value (en)
    $text = "$S IF (tm_matches = $LANGVAR.match('^(\\w+)[-_].*\$')); tm_fb = tm_matches.0; END $E";

    for my $section (@{$self->{_sections}}) {
        if ($section->{nolang}) {
            $text .= $section->{nolang};
        }
        elsif (my $t = $section->{lang}) {
            my @languages = keys %$t;

            # first loop through languages: look for exact match
            $text .= "$S tm_f = 0; SWITCH $LANGVAR $E";
            for my $lang (@languages) {
                $text .= "$S CASE '$lang' $E" . $t->{$lang};
            }
            # add a default case to trigger fallback
            $text .= "$S CASE; tm_f=1; END; $E";

            # second loop: fallback to primary language (en_US matches en)
            $text .= "$S IF tm_fb AND tm_f; tm_f=0; SWITCH tm_fb; $E";
            for my $lang (@languages) {
                $text .= "$S CASE '$lang' $E" . $t->{$lang};
            }
            # add a default case to trigger last resort fallback
            #   LANG is fr_XX or fr but template has neither
            #   we try to fallback to fr_YY is present
            my %seen;
            my @fallbacks = map { /^(\w+)[-_].*$/ && !$seen{$_}++ ? [ $1 => $_] : () } sort @languages;
            if (@fallbacks) {
                # third loop: fallback to first available variant
                $text .= "$S CASE; tm_f=1; END; END; IF tm_f; SWITCH tm_fb || $LANGVAR; $E";
                for my $ref (@fallbacks) {
                    my ($lang, $variant) = @$ref;
                    $text .= "$S CASE '$lang' $E" . $t->{$variant};
                }
            }
            $text .= "$S END; END $E";
        }
    }
    return $self->SUPER::parse ($text);
}

sub _tokenize
{
    my ($self, $text) = @_;

    # extract all sections from the text
    $self->{_sections} = [];
    my @tokens = split m!<t>(.*?)</t>!s, $text;
    my $i = 0;
    for my $t (@tokens) {
        if ($i) {             # <t>...</t> multilingual section
            my %section;
            while ($t =~ m!<([^<>]+)>(.*?)</\1>!gs) {
                $section{$1} = $2;
            }
            push @{$self->{_sections}}, { lang => \%section }
                if %section;
        }
        else {                # bare text
            push @{$self->{_sections}}, { nolang => $t } if $t;
        }
        $i = 1 - $i;
    }
}
sub sections { $_[0]->{_sections} }

=head1 NAME

Template::Multilingual::Parser - Multilingual template parser

=head1 SYNOPSIS

    use Template;
    use Template::Multilingual::Parser;
    
    my $parser = Template::Multilingual::Parser->new();
    my $template = Template->new(PARSER => $parser);
    $template->process('example.ttml', { language => 'en'});

=head1 DESCRIPTION

This subclass of Template Toolkit's C<Template::Parser> parses multilingual
templates: templates that contain text in several languages.

    <t>
      <en>Hello!</en>
      <fr>Bonjour !</fr>
    </t>

Use this module directly if you have subclassed C<Template>, otherwise you
may find it easier to use C<Template::Multilingual>.

Language codes can be any string that matches C<\w+>, but we suggest
sticking to ISO-639 which provides 2-letter codes for common languages
and 3-letter codes for many others.

=head1 METHODS

=head2 new(\%params)

The new() constructor creates and returns a reference to a new
parser object. A reference to a hash may be supplied as a
parameter to provide configuration values.

Parser objects are typically provided as the C<PARSER> option
to the C<Template> constructor.

Configuration values are all valid C<Template::Parser> superclass