/
GroupBy.php
72 lines (64 loc) · 2.15 KB
/
GroupBy.php
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<?php
/**
* For the full copyright and license information, please view
* the LICENSE file that was distributed with this source code.
*/
declare(strict_types=1);
namespace loophp\collection\Operation;
use Closure;
use Generator;
use Iterator;
/**
* @immutable
*
* @template TKey
* @template T
*
* phpcs:disable Generic.Files.LineLength.TooLong
*/
final class GroupBy extends AbstractOperation
{
/**
* @pure
*
* @template NewTKey of array-key
*
* @return Closure(callable(T=, TKey=): NewTKey):Closure(Iterator<TKey, T>): Generator<NewTKey, non-empty-list<T>>
*/
public function __invoke(): Closure
{
return
/**
* @param callable(T=, TKey=): NewTKey $callable
*
* @return Closure(Iterator<TKey, T>): Generator<NewTKey, non-empty-list<T>>
*/
static function (callable $callable): Closure {
$reducerFactory =
/**
* @param callable(T=, TKey=): NewTKey $callback
*
* @return Closure(array<NewTKey, non-empty-list<T>>, T, TKey): array<NewTKey, non-empty-list<T>>
*/
static fn (callable $callback): Closure =>
/**
* @param array<NewTKey, non-empty-list<T>> $collect
* @param T $value
* @param TKey $key
*
* @return non-empty-array<NewTKey, non-empty-list<T>>
*/
static function (array $collect, $value, $key) use ($callback): array {
$collect[$callback($value, $key)][] = $value;
return $collect;
};
/** @var Closure(Iterator<TKey, T>): Generator<NewTKey, non-empty-list<T>> $pipe */
$pipe = Pipe::of()(
Reduce::of()($reducerFactory($callable))([]),
Flatten::of()(1)
);
// Point free style.
return $pipe;
};
}
}