package URI::_idna;

# This module implements the RFCs 3490 (IDNA) and 3491 (Nameprep)
# based on Python-2.6.4/Lib/encodings/idna.py

use strict;
use URI::_punycode qw(encode_punycode decode_punycode);
use Carp qw(croak);

my $ASCII = qr/^[\x00-\x7F]*\z/;

sub encode {
    my $idomain = shift;
    my @labels = split(/\./, $idomain, -1);
    my @last_empty;
    push(@last_empty, pop @labels) if @labels > 1 && $labels[-1] eq "";
    for (@labels) {
	$_ = ToASCII($_);
    }
    return join(".", @labels, @last_empty);
}

sub decode {
    my $domain = shift;
    return join(".", map ToUnicode($_), split(/\./, $domain, -1))
}

sub nameprep { # XXX real implementation missing
    my $label = shift;
    $label = lc($label);
    return $label;
}

sub check_size {
    my $label = shift;
    croak "Label empty" if $label eq "";
    croak "Label too long" if length($label) > 63;
    return $label;
}

sub ToASCII {
    my $label = shift;
    return check_size($label) if $label =~ $ASCII;

    # Step 2: nameprep
    $label = nameprep($label);
    # Step 3: UseSTD3ASCIIRules is false
    # Step 4: try ASCII again
    return check_size($label) if $label =~ $ASCII;

    # Step 5: Check ACE prefix
    if ($label =~ /^xn--/) {
        croak "Label starts with ACE prefix";
    }

    # Step 6: Encode with PUNYCODE
    $label = encode_punycode($label);

    # Step 7: Prepend ACE prefix
    $label = "xn--$label";

    # Step 8: Check size
    return check_size($label);
}

sub ToUnicode {
    my $label = shift;
    $label = nameprep($label) unless $label =~ $ASCII;
    return $label unless $label =~ /^xn--/;
    my $result = decode_punycode(substr($label, 4));
    my $label2 = ToASCII($result);
    if (lc($label) ne $label2) {
	croak "IDNA does not round-trip: '\L$label\E' vs '$label2'";
    }
    return $result;
}

1;
