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KeysetPaginator.php
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KeysetPaginator.php
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<?php
declare(strict_types=1);
namespace Yiisoft\Data\Paginator;
use InvalidArgumentException;
use RuntimeException;
use Yiisoft\Arrays\ArrayHelper;
use Yiisoft\Data\Reader\Filter\Compare;
use Yiisoft\Data\Reader\Filter\GreaterThan;
use Yiisoft\Data\Reader\Filter\GreaterThanOrEqual;
use Yiisoft\Data\Reader\Filter\LessThan;
use Yiisoft\Data\Reader\Filter\LessThanOrEqual;
use Yiisoft\Data\Reader\FilterableDataInterface;
use Yiisoft\Data\Reader\ReadableDataInterface;
use Yiisoft\Data\Reader\Sort;
use Yiisoft\Data\Reader\SortableDataInterface;
use Yiisoft\Strings\Inflector;
use function array_reverse;
use function count;
use function is_callable;
use function is_object;
use function key;
use function reset;
use function sprintf;
/**
* Keyset paginator.
*
* Advantages:
*
* - Performance does not depend on page number
* - Consistent results regardless of insertions and deletions
*
* Disadvantages:
*
* - Total number of pages is not available
* - Can not get to specific page, only "previous" and "next"
* - Data cannot be unordered
*
* @link https://use-the-index-luke.com/no-offset
*
* @template TKey as array-key
* @template TValue as array|object
*
* @implements PaginatorInterface<TKey, TValue>
*/
final class KeysetPaginator implements PaginatorInterface
{
/**
* Data reader being paginated.
*
* @psalm-var ReadableDataInterface<TKey, TValue>&FilterableDataInterface&SortableDataInterface
*/
private ReadableDataInterface $dataReader;
/**
* @var int Maximum number of items per page.
*/
private int $pageSize = self::DEFAULT_PAGE_SIZE;
private ?string $firstValue = null;
private ?string $lastValue = null;
private ?string $currentFirstValue = null;
private ?string $currentLastValue = null;
/**
* @var bool Whether there is previous page.
*/
private bool $hasPreviousPage = false;
/**
* @var bool Whether there is next page.
*/
private bool $hasNextPage = false;
/**
* Reader cache against repeated scans.
* See more {@see __clone()} and {@see initialize()}.
*
* @psalm-var null|array<TKey, TValue>
*/
private ?array $readCache = null;
/**
* @param ReadableDataInterface $dataReader Data reader being paginated.
* @psalm-param ReadableDataInterface<TKey, TValue>&FilterableDataInterface&SortableDataInterface $dataReader
* @psalm-suppress DocblockTypeContradiction
*/
public function __construct(ReadableDataInterface $dataReader)
{
if (!$dataReader instanceof FilterableDataInterface) {
throw new InvalidArgumentException(sprintf(
'Data reader should implement "%s" to be used with keyset paginator.',
FilterableDataInterface::class,
));
}
if (!$dataReader instanceof SortableDataInterface) {
throw new InvalidArgumentException(sprintf(
'Data reader should implement "%s" to be used with keyset paginator.',
SortableDataInterface::class,
));
}
$sort = $dataReader->getSort();
if ($sort === null) {
throw new RuntimeException('Data sorting should be configured to work with keyset pagination.');
}
if (empty($sort->getOrder())) {
throw new RuntimeException('Data should be always sorted to work with keyset pagination.');
}
$this->dataReader = $dataReader;
}
public function __clone()
{
$this->readCache = null;
$this->hasPreviousPage = false;
$this->hasNextPage = false;
$this->currentFirstValue = null;
$this->currentLastValue = null;
}
public function withNextPageToken(?string $token): static
{
$new = clone $this;
$new->firstValue = null;
$new->lastValue = $token;
return $new;
}
public function withPreviousPageToken(?string $token): static
{
$new = clone $this;
$new->firstValue = $token;
$new->lastValue = null;
return $new;
}
public function withPageSize(int $pageSize): static
{
if ($pageSize < 1) {
throw new InvalidArgumentException('Page size should be at least 1.');
}
$new = clone $this;
$new->pageSize = $pageSize;
return $new;
}
/**
* Reads items of the page.
*
* This method uses the read cache to prevent duplicate reads from the data source. See more {@see resetInternal()}.
*/
public function read(): iterable
{
if ($this->readCache !== null) {
return $this->readCache;
}
/** @var Sort $sort */
$sort = $this->dataReader->getSort();
$dataReader = $this->dataReader->withLimit($this->pageSize + 1);
if ($this->isGoingToPreviousPage()) {
$sort = $this->reverseSort($sort);
$dataReader = $dataReader->withSort($sort);
}
if ($this->isGoingSomewhere()) {
$dataReader = $dataReader->withFilter($this->getFilter($sort));
$this->hasPreviousPage = $this->previousPageExist($dataReader, $sort);
}
$data = $this->readData($dataReader, $sort);
if ($this->isGoingToPreviousPage()) {
$data = $this->reverseData($data);
}
return $this->readCache = $data;
}
public function getPageSize(): int
{
return $this->pageSize;
}
public function getCurrentPageSize(): int
{
$this->initialize();
return count($this->readCache);
}
public function getPreviousPageToken(): ?string
{
return $this->isOnFirstPage() ? null : $this->currentFirstValue;
}
public function getNextPageToken(): ?string
{
return $this->isOnLastPage() ? null : $this->currentLastValue;
}
public function getSort(): ?Sort
{
/** @psalm-var SortableDataInterface $this->dataReader */
return $this->dataReader->getSort();
}
public function isOnFirstPage(): bool
{
if ($this->lastValue === null && $this->firstValue === null) {
return true;
}
$this->initialize();
return !$this->hasPreviousPage;
}
public function isOnLastPage(): bool
{
$this->initialize();
return !$this->hasNextPage;
}
public function isRequired(): bool
{
return !$this->isOnFirstPage() || !$this->isOnLastPage();
}
/**
* @psalm-assert array<TKey, TValue> $this->readCache
*/
private function initialize(): void
{
if ($this->readCache !== null) {
return;
}
$cache = [];
foreach ($this->read() as $key => $value) {
$cache[$key] = $value;
}
$this->readCache = $cache;
}
/**
* @psalm-param ReadableDataInterface<TKey, TValue> $dataReader
* @psalm-return array<TKey, TValue>
*/
private function readData(ReadableDataInterface $dataReader, Sort $sort): array
{
$data = [];
/** @var string $field */
[$field] = $this->getFieldAndSortingFromSort($sort);
foreach ($dataReader->read() as $key => $item) {
if ($this->currentFirstValue === null) {
$this->currentFirstValue = (string) $this->getValueFromItem($item, $field);
}
if (count($data) === $this->pageSize) {
$this->hasNextPage = true;
} else {
$this->currentLastValue = (string) $this->getValueFromItem($item, $field);
$data[$key] = $item;
}
}
return $data;
}
/**
* @psalm-param array<TKey, TValue> $data
* @psalm-return array<TKey, TValue>
*/
private function reverseData(array $data): array
{
[$this->currentFirstValue, $this->currentLastValue] = [$this->currentLastValue, $this->currentFirstValue];
[$this->hasPreviousPage, $this->hasNextPage] = [$this->hasNextPage, $this->hasPreviousPage];
return array_reverse($data, true);
}
/**
* @psalm-param ReadableDataInterface<TKey, TValue>&FilterableDataInterface&SortableDataInterface $dataReader
*/
private function previousPageExist(ReadableDataInterface $dataReader, Sort $sort): bool
{
$reverseFilter = $this->getReverseFilter($sort);
return !empty($dataReader->withFilter($reverseFilter)->withLimit(1)->read());
}
private function getValueFromItem(array|object $item, string $field): mixed
{
$methodName = 'get' . (new Inflector())->toPascalCase($field);
if (is_object($item) && is_callable([$item, $methodName])) {
return $item->$methodName();
}
return ArrayHelper::getValue($item, $field);
}
private function getFilter(Sort $sort): Compare
{
$value = $this->getValue();
/** @var string $field */
[$field, $sorting] = $this->getFieldAndSortingFromSort($sort);
return $sorting === 'asc' ? new GreaterThan($field, $value) : new LessThan($field, $value);
}
private function getReverseFilter(Sort $sort): Compare
{
$value = $this->getValue();
/** @var string $field */
[$field, $sorting] = $this->getFieldAndSortingFromSort($sort);
return $sorting === 'asc' ? new LessThanOrEqual($field, $value) : new GreaterThanOrEqual($field, $value);
}
/**
* @psalm-suppress NullableReturnStatement, InvalidNullableReturnType The code calling this method
* must ensure that at least one of the properties `$firstValue` or `$lastValue` is not `null`.
*/
private function getValue(): string
{
return $this->isGoingToPreviousPage() ? $this->firstValue : $this->lastValue;
}
private function reverseSort(Sort $sort): Sort
{
$order = $sort->getOrder();
foreach ($order as &$sorting) {
$sorting = $sorting === 'asc' ? 'desc' : 'asc';
}
return $sort->withOrder($order);
}
private function getFieldAndSortingFromSort(Sort $sort): array
{
$order = $sort->getOrder();
return [
(string) key($order),
reset($order),
];
}
private function isGoingToPreviousPage(): bool
{
return $this->firstValue !== null && $this->lastValue === null;
}
private function isGoingSomewhere(): bool
{
return $this->firstValue !== null || $this->lastValue !== null;
}
}