use v5.14;
use strict;
use warnings;

BEGIN {
	package Local::Module 2.00;
	no thanks;  # this is just a helper for defining multiple
	            # packages in the same file!
	
	# detect requested version, and store it
	my %api_preference;
	sub VERSION
	{
		$api_preference{ scalar caller } //= $_[1] if @_==2;
		shift->SUPER::VERSION( @_ );
	}
	
	use Sub::Exporter;
	my $IMPORT = Sub::Exporter::build_exporter({
		exports => [
			alphabet => \&_build_alphabet,
			numbers  => \&_build_numbers,
			colours  => undef,
		],
		collectors => [qw/ defaults auto /],
	});
	sub import
	{
		push @_, auto => { api => ($api_preference{ scalar caller }//1.00) };
		goto $IMPORT;
	}
	
	# This sub is the same for API 1 and API 2
	sub colours
	{
		return [qw( red orange yellow green blue indigo violet )];
	}
	
	# Version 1 API returns lower-case; version 2 API is uppercase
	sub _build_alphabet
	{
		my ($class, $name, $arg, $col) = @_;
		my $api = $arg->{api} // $col->{defaults}{api} // $col->{auto}{api};
		
		if ($api >= 2)
		{
			return sub { ['A'..'Z'] };
		}
		else
		{
			return sub { ['a'..'z'] };
		}
	}

	# Version 1 API returns 1..5; version 2 API returns 1..10.
	sub _build_numbers
	{
		my ($class, $name, $arg, $col) = @_;
		my $api = $arg->{api} // $col->{defaults}{api} // $col->{auto}{api};
		
		if ($api >= 2)
		{
			return sub { [1..10] };
		}
		else
		{
			return sub { [1..5] };
		}
	}
};

TESTING: {
	use Test::More;

	# Expected results:
	my $alphabet1 = [ 'a'..'z' ];
	my $alphabet2 = [ 'A'..'Z' ];
	my $numbers1  = [  1 ..  5 ];
	my $numbers2  = [  1 .. 10 ];
	my $colours   = [qw( red orange yellow green blue indigo violet )];

	# This consumer should get API 1
	BEGIN {
		package Local::Consumer1 0.001;
		no thanks;
		use Local::Module 1.000 -all;
	};

	is_deeply(
		Local::Consumer1::alphabet(),
		$alphabet1,
		'Local::Consumer1 has alphabet() API 1',
	);

	is_deeply(
		Local::Consumer1::numbers(),
		$numbers1,
		'Local::Consumer1 has numbers() API 1',
	);

	is_deeply(
		Local::Consumer1::colours(),
		$colours,
		'Local::Consumer1 has colours() invariant',
	);

	# This consumer should get API 2
	BEGIN {
		package Local::Consumer2 0.001;
		no thanks;
		use Local::Module 2.000 -all;
	};

	is_deeply(
		Local::Consumer2::alphabet(),
		$alphabet2,
		'Local::Consumer2 has alphabet() API 2',
	);

	is_deeply(
		Local::Consumer2::numbers(),
		$numbers2,
		'Local::Consumer2 has numbers() API 1',
	);

	is_deeply(
		Local::Consumer2::colours(),
		$colours,
		'Local::Consumer2 has colours() invariant',
	);

	# This consumer should get API 1
	BEGIN {
		package Local::Consumer3 0.001;
		no thanks;
		use Local::Module -all;
	};

	is_deeply(
		Local::Consumer3::alphabet(),
		$alphabet1,
		'Local::Consumer3 has alphabet() API 1',
	);

	is_deeply(
		Local::Consumer3::numbers(),
		$numbers1,
		'Local::Consumer3 has numbers() API 1',
	);

	is_deeply(
		Local::Consumer3::colours(),
		$colours,
		'Local::Consumer3 has colours() invariant',
	);

	# This consumer should get API 2, except for numbers() where they want API 1
	BEGIN {
		package Local::Consumer4 0.001;
		no thanks;
		use Local::Module 2.000
			numbers => { api => 1 },
			qw( colours alphabet );
	};

	is_deeply(
		Local::Consumer4::alphabet(),
		$alphabet2,
		'Local::Consumer4 has alphabet() API 2',
	);

	is_deeply(
		Local::Consumer4::numbers(),
		$numbers1,
		'Local::Consumer4 has numbers() API 1',
	);

	is_deeply(
		Local::Consumer4::colours(),
		$colours,
		'Local::Consumer4 has colours() invariant',
	);

	# This consumer wants both versions of the numbers() function
	BEGIN {
		package Local::Consumer5 0.001;
		no thanks;
		use Local::Module 2.000
			numbers => { api => 1, -as => 'old_numbers' },
			numbers => { api => 2 },
		;
	};

	is_deeply(
		Local::Consumer5::numbers(),
		$numbers2,
		'Local::Consumer5 has numbers() API 2',
	);

	is_deeply(
		Local::Consumer5::old_numbers(),
		$numbers1,
		'Local::Consumer5 has old_numbers() function which is number() from API 1',
	);

	done_testing;
};