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FilteredSequentialIterator.php
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FilteredSequentialIterator.php
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<?php
namespace MediaWiki\Extension\Notifications\Iterator;
use ArrayIterator;
use CallbackFilterIterator;
use EmptyIterator;
use InvalidArgumentException;
use Iterator;
use IteratorAggregate;
use RecursiveIteratorIterator;
/**
* Allows building a single iterator out of multiple iterators
* and filtering the results. Accepts plain arrays for the simple
* use case, also accepts Iterator instances for anything more complex.
*
* This exists so that UserLocator implementations can return iterators
* that return potentially thousands of users without having to grab
* them all in one giant query.
*
* Usage:
* $users = new FilteredSequentialIterator;
* $users->add( [ $userA, $userB, $userC ] );
*
* $it = new BatchRowIterator( ... );
* ...
* $it = new RecursiveIteratorIterator( $it );
* $users->add( new CallbackIterator( $it, function( $row ) {
* ...
* return $user;
* } ) );
*
* foreach ( $users as $user ) {
* ...
* }
*
* By default the BatchRowIterator returns an array of rows, this class
* expects a stream of user objects. To bridge that gap the
* RecursiveIteratorIterator is used to flatten and the CallbackIterator
* is used to transform each database $row into a User object.
*
* @todo name?
*/
class FilteredSequentialIterator implements IteratorAggregate {
/**
* @var Iterator[]
*/
protected $iterators = [];
/**
* @var callable[]
*/
protected $filters = [];
/**
* @param Iterator|IteratorAggregate|array $users
*/
public function add( $users ) {
if ( is_array( $users ) ) {
$it = new ArrayIterator( $users );
} elseif ( $users instanceof Iterator ) {
$it = $users;
} elseif ( $users instanceof IteratorAggregate ) {
$it = $users->getIterator();
} else {
throw new InvalidArgumentException( 'Expected array, Iterator or IteratorAggregate but received ' .
get_debug_type( $users )
);
}
$this->iterators[] = $it;
}
/**
* @param callable $callable
*/
public function addFilter( $callable ) {
$this->filters[] = $callable;
}
/**
* Satisfies IteratorAggregate interface
*
* @return Iterator
*/
public function getIterator(): Iterator {
$it = $this->createIterator();
if ( $this->filters ) {
$it = new CallbackFilterIterator( $it, $this->createFilter() );
}
return $it;
}
/**
* @return Iterator
*/
protected function createIterator() {
switch ( count( $this->iterators ) ) {
case 0:
return new EmptyIterator;
case 1:
return reset( $this->iterators );
default:
return new RecursiveIteratorIterator( new MultipleIterator( $this->iterators ) );
}
}
/**
* @return callable
*/
protected function createFilter() {
switch ( count( $this->filters ) ) {
case 0:
return static function () {
return true;
};
case 1:
return reset( $this->filters );
default:
$filters = $this->filters;
return static function ( $user ) use ( $filters ) {
foreach ( $filters as $filter ) {
if ( !call_user_func( $filter, $user ) ) {
return false;
}
}
return true;
};
}
}
}

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FilteredSequentialIterator.php (3 KB)

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