use open qw/:std :utf8/;
use Test::More;
use File::Temp qw/tempfile/;

my ($tempfh, $filename) = tempfile( UNLINK => 1 );
binmode $tempfh, ':encoding(UTF-8)';
print $tempfh "H\N{U+20AC}ll\N{U+00F6}, \N{U+1F5FA}!\n";
close $tempfh;
#system('hexdump','-C',$filename);

my $four = readbackwards_utf8($filename, 4);
is $four->(), "!\n";
is $four->(), "\N{U+1F5FA}";
is $four->(), "\N{U+00F6}, ";
is $four->(), "ll";
is $four->(), "H\N{U+20AC}";
is $four->(), undef;
is $four->(), undef;

my $five = readbackwards_utf8($filename, 5);
is $five->(), "!\n";
is $five->(), " \N{U+1F5FA}";
is $five->(), "ll\N{U+00F6},";
is $five->(), "H\N{U+20AC}";
is $five->(), undef;

my $six = readbackwards_utf8($filename, 6);
is $six->(), "\N{U+1F5FA}!\n";
is $six->(), "ll\N{U+00F6}, ";
is $six->(), "H\N{U+20AC}";
is $six->(), undef;

my $seven = readbackwards_utf8($filename, 7);
is $seven->(), " \N{U+1F5FA}!\n";
is $seven->(), "ll\N{U+00F6},";
is $seven->(), "H\N{U+20AC}";
is $seven->(), undef;

for my $n (8..9) {
	my $eight = readbackwards_utf8($filename, $n);
	is $eight->(), ", \N{U+1F5FA}!\n";
	is $eight->(), "H\N{U+20AC}ll\N{U+00F6}";
	is $eight->(), undef;
}

my $ten = readbackwards_utf8($filename, 10);
is $ten->(), "\N{U+00F6}, \N{U+1F5FA}!\n";
is $ten->(), "H\N{U+20AC}ll";
is $ten->(), undef;

my $eleven = readbackwards_utf8($filename, 11);
is $eleven->(), "l\N{U+00F6}, \N{U+1F5FA}!\n";
is $eleven->(), "H\N{U+20AC}l";
is $eleven->(), undef;

for my $n (12..14) {
	my $twelve = readbackwards_utf8($filename, $n);
	is $twelve->(), "ll\N{U+00F6}, \N{U+1F5FA}!\n";
	is $twelve->(), "H\N{U+20AC}";
	is $twelve->(), undef;
}

my $fifteen = readbackwards_utf8($filename, 15);
is $fifteen->(), "\N{U+20AC}ll\N{U+00F6}, \N{U+1F5FA}!\n";
is $fifteen->(), "H";
is $fifteen->(), undef;

for my $n (16..17) {
	my $sixteen = readbackwards_utf8($filename, 16);
	is $sixteen->(), "H\N{U+20AC}ll\N{U+00F6}, \N{U+1F5FA}!\n";
	is $sixteen->(), undef;
}

done_testing;