use warnings;
use strict;

use feature 'state';
use Carp;
use Math::BigInt;
use Config;
use Regexp::Common qw/number/;

sub validate_int {
	my $str = shift;
	state $max = Math::BigInt->new(
		eval $Config{nv_overflows_integers_at} );
	croak "not an integer"
		unless defined $str && $str=~/\A$RE{num}{int}\z/;
	my $num = Math::BigInt->new($str);
	croak "integer to small" if $num < 0;
	croak "integer too big" if $num > $max;
	return $num->numify;
}


use Test::More;
sub exception (&) { eval { shift->(); 1 } ? undef : ($@ || die) }

is validate_int(0), 0;
is validate_int(1), 1;
is validate_int(3), 3;
ok exception { validate_int(undef) };
ok exception { validate_int("") };
ok exception { validate_int("x") };
ok exception { validate_int("123y") };
ok exception { validate_int(-1) };
ok exception { validate_int("-9999999999999999999999999999999") };

my $x = Math::BigInt->new(eval $Config{nv_overflows_integers_at})-1;
is validate_int("$x"), 0+$x->numify, "'$x' works (max-1)";
$x++;
is validate_int("$x"), 0+$x->numify, "'$x' works (max)";
$x++;
ok exception { validate_int("$x") }, "'$x' fails (max+1)";

ok exception { validate_int("999999999999999999999999999999999999") };

done_testing;